#385

#353 を再開できなかったので．

Reviewed-on: #380
Co-authored-by: miteruzo <miteruzo@naver.com>
Co-committed-by: miteruzo <miteruzo@naver.com>

AGENTS.md

@@ -132,6 +132,10 @@ npm run preview
 - Tabs are only for leading indentation, never for spaces after non-space text.
 - TypeScript and TSX imports may stay on one line if they remain within the
   line limit; do not expand short type-only imports mechanically.
+- In TypeScript and TSX, when breaking a line at an operator, break before the
+  operator and put the operator at the beginning of the next line. A trailing
+  operator at end of line is unacceptable. This rule does not apply to Ruby,
+  where it can change the syntactic structure.
 - In TypeScript and TSX, when a function takes one destructured object
   argument plus an inline type, prefer this shape when it fits locally:
 
@@ -231,6 +235,22 @@ const value =
 - Keep page-level code under `frontend/src/pages` and shared UI/feature code
   under `frontend/src/components` unless existing patterns point elsewhere.
 - Match existing Tailwind, component, and import alias conventions.
+- `<a href="#">` is acceptable for event-only controls when it fits the local
+  UI pattern. Do not use `<a>` for internal navigation or other non-external
+  links.
+- Internal links must use `PrefetchLink`.
+- External links must use `<a>` with `target="_blank"`.
+- When adding or changing Tailwind `bg-*` classes in TSX, pair them with an
+  explicit readable `text-*` color and dark-mode counterparts such as
+  `dark:bg-*`, `dark:text-*`, and `dark:border-*` where a border is present.
+- Do not rely on inherited text color for light backgrounds. This is especially
+  important for chips, cards, buttons, and panels that may inherit white text in
+  dark mode.
+- Mobile UI must be checked as a first-class layout. Avoid wide fixed content,
+  make dense controls wrap or scroll intentionally, and keep tag/filter
+  controls usable without horizontal page overflow.
+- For mobile horizontal scrollers, make the scroll direction and item sizing
+  explicit, and ensure chip text remains readable in both light and dark modes.
 - In TypeScript and TSX, prefer direct comparison operators such as `===` and
   `!==` over negating a comparison like `!(a === b)`.
 - In TypeScript and TSX, prefer `++i` or `--i` over `i += 1` or `i -= 1` for
@@ -248,7 +268,25 @@ const value =
 - Put two blank lines before and after top-level `const` function
   declarations, unless imports, exports, or file boundaries make that awkward.
 - In TSX, indent with 4-space logical indentation.
+- In TypeScript and TSX, convert every leading run of 8 spaces to a tab
+  character.
 - A leading tab is exactly equivalent to 8 leading spaces.
+- In TypeScript and TSX function declarations, including `const` arrow
+  function declarations, when the parameter list spans multiple lines, always
+  put the closing parenthesis at the beginning of its own line before the return
+  type or `=>`.
+- In TypeScript and TSX, never place a closing parenthesis at the beginning of
+  a line except for a multi-line function declaration parameter list.
+- Never place a closing square bracket at the beginning of a line.
+- For object literals and other associative-array-style braces, do not place
+  the closing brace at the beginning of a line. Function, lambda, callback, and
+  block closing braces are exempt and should stay on their own line when that
+  fits the local style.
+- When writing braces on a single line in TypeScript or TSX JavaScript
+  context, put exactly one space inside the braces, as in `{ value }` or
+  `{ key: value }`.
+- Do not add inner spaces to React/JSX expression braces, as in
+  `prop={value}`, `{children}`, or `<Component>{{...props}}</Component>`.
 - Keep a tag's closing marker on the same line as the final prop when the tag
   spans multiple lines.
 - Do not put `/>` or `>` on its own line unless the existing surrounding code

backend/app/controllers/material_sync_suppressions_controller.rb

@@ -0,0 +1,49 @@
+class MaterialSyncSuppressionsController < ApplicationController
+  def index
+    return head :unauthorized unless current_user
+    return head :forbidden unless current_user.gte_member?
+
+    suppressions =
+        MaterialSyncSuppression
+        .includes(:created_by_user)
+        .order(created_at: :desc, id: :desc)
+
+    render json: { suppressions: suppressions.map { |s| repr(s) } }
+  end
+
+  def create
+    return head :unauthorized unless current_user
+    return head :forbidden unless current_user.gte_member?
+
+    suppression =
+        MaterialSyncSuppressionRegistrar.create!(suppression_params,
+                                                 created_by_user: current_user)
+
+    render json: repr(suppression), status: :created
+  rescue ActiveRecord::RecordInvalid => e
+    render_validation_error e.record
+  end
+
+  private
+
+  def suppression_params
+    params.permit(:source_kind,
+                  :source_uri,
+                  :drive_path,
+                  :drive_file_id,
+                  :reason)
+  end
+
+  def repr suppression
+    { id: suppression.id,
+      source_kind: suppression.source_kind,
+      source_uri: suppression.source_uri,
+      drive_path: suppression.drive_path,
+      drive_file_id: suppression.drive_file_id,
+      normalized_source_key: suppression.normalized_source_key,
+      reason: suppression.reason,
+      created_by_user: suppression.created_by_user&.as_json(UserRepr::BASE),
+      created_at: suppression.created_at,
+      updated_at: suppression.updated_at }
+  end
+end

backend/app/controllers/material_versions_controller.rb

@@ -0,0 +1,54 @@
+class MaterialVersionsController < ApplicationController
+  def index
+    page = (params[:page].presence || 1).to_i
+    limit = (params[:limit].presence || 20).to_i
+
+    page = 1 if page < 1
+    limit = 1 if limit < 1
+
+    offset = (page - 1) * limit
+
+    q = MaterialVersion.includes(:created_by_user)
+    q = q.where(material_id: params[:material_id]) if params[:material_id].present?
+    q = q.where(tag_name: params[:tag].to_s.strip) if params[:tag].present?
+    q = q.where(event_type: params[:event_type]) if params[:event_type].present?
+
+    count = q.except(:order, :limit, :offset).count
+    versions =
+        q
+        .order(Arel.sql('material_versions.created_at DESC, material_versions.id DESC'))
+        .limit(limit)
+        .offset(offset)
+
+    render json: { versions: serialise_versions(versions), count: }
+  end
+
+  private
+
+  def serialise_versions rows
+    rows.map do |row|
+      { id: row.id,
+        material_id: row.material_id,
+        version_no: row.version_no,
+        event_type: row.event_type,
+        tag_id: row.tag_id,
+        tag_name: row.tag_name,
+        tag_category: row.tag_category,
+        url: row.url,
+        source_kind: row.source_kind,
+        source_uri: row.source_uri,
+        source_path: row.source_path,
+        source_file_id: row.source_file_id,
+        normalized_source_key: row.normalized_source_key,
+        file_blob_id: row.file_blob_id,
+        file_filename: row.file_filename,
+        file_content_type: row.file_content_type,
+        file_byte_size: row.file_byte_size,
+        file_sha256: row.file_sha256,
+        export_paths_json: row.export_paths_hash,
+        discarded_at: row.discarded_at,
+        created_by_user: row.created_by_user&.as_json(UserRepr::BASE),
+        created_at: row.created_at }
+    end
+  end
+end

backend/app/controllers/materials_controller.rb

@@ -1,3 +1,6 @@
+require 'set'
+
+
 class MaterialsController < ApplicationController
   rescue_from MaterialZipExporter::EmptyExportError, with: :render_zip_empty
   rescue_from MaterialZipExporter::DuplicatePathError, with: :render_zip_duplicate_path
@@ -12,28 +15,55 @@ class MaterialsController < ApplicationController
 
     offset = (page - 1) * limit
 
-    tag_id = params[:tag_id].presence
-    parent_id = params[:parent_id].presence
+    filters = material_index_filters
+    tag_graph = material_index_tag_graph(filters)
+    q = Material.includes(:material_export_items,
+                          thumbnail_attachment: :blob,
+                          file_attachment: :blob,
+                          tag: :tag_name)
+    q = q.where(tag_id: nil) if filters[:tag_state] == 'untagged'
+    q = q.where.not(tag_id: nil) if filters[:tag_state] == 'tagged'
+    q = apply_material_tag_filter(q, filters, tag_graph)
+    q = q.where('materials.created_at >= ?', filters[:created_from]) if filters[:created_from]
+    q = q.where('materials.created_at <= ?', filters[:created_to]) if filters[:created_to]
+    q = q.where('materials.updated_at >= ?', filters[:updated_from]) if filters[:updated_from]
+    q = q.where('materials.updated_at <= ?', filters[:updated_to]) if filters[:updated_to]
 
-    q = Material.includes(:tag, :created_by_user, :material_export_items).with_attached_file
-    q = q.where(tag_id:) if tag_id
-    q = q.where(parent_id:) if parent_id
+    q = material_index_join_tag_name(q) if material_index_needs_tag_name?(filters)
+    q = material_index_join_file_blob(q) if material_index_needs_file_blob?(filters)
+    q = apply_material_query(q, filters[:q]) if filters[:q].present?
+    q = apply_material_media_kind(q, filters[:media_kind])
 
-    count = q.count
-    materials = q.order(created_at: :desc, id: :desc).limit(limit).offset(offset)
+    count = q.distinct.count(:id)
+    materials =
+        q
+        .order(Arel.sql(material_index_order_sql(filters)))
+        .limit(limit)
+        .offset(offset)
+        .to_a
 
-    render json: { materials: MaterialRepr.many(materials, host: request.base_url), count: count }
+    response = { materials: MaterialRepr.list_many(materials, host: request.base_url),
+                 count: }
+    if filters[:tag_id]
+      response[:tag_scope] = material_index_tag_scope(filters, tag_graph)
+    end
+    if filters[:group_by] == 'parent_tag'
+      response[:groups] = material_index_groups(materials, tag_graph)
+    end
+
+    render json: response
   end
 
   def show
     material =
         Material
         .includes(:tag, :material_export_items)
+        .with_attached_thumbnail
         .with_attached_file
         .find_by(id: params[:id])
     return head :not_found unless material
 
-    wiki_page_body = material.tag.tag_name.wiki_page&.current_revision&.body
+    wiki_page_body = material.tag&.tag_name&.wiki_page&.current_revision&.body
 
     render json: MaterialRepr.base(material, host: request.base_url).merge(wiki_page_body:)
   end
@@ -78,6 +108,7 @@ class MaterialsController < ApplicationController
     end
 
     if material
+      log_thumbnail_generation(material, MaterialThumbnailGenerator.generate!(material))
       render json: MaterialRepr.base(material, host: request.base_url), status: :created
     else
       render_validation_error material
@@ -115,7 +146,6 @@ class MaterialsController < ApplicationController
         material.assign_attributes(tag:, url:, updated_by_user: current_user)
         if uploaded_blob
           material.file.attach(uploaded_blob)
-          clear_file_suppression!(material)
         elsif params.key?(:url) && url.present? && file.blank?
           material.file.detach
         end
@@ -129,6 +159,8 @@ class MaterialsController < ApplicationController
       raise
     end
 
+    log_thumbnail_generation(material, MaterialThumbnailGenerator.generate!(material))
+
     render json: MaterialRepr.base(material, host: request.base_url)
   end
 
@@ -158,38 +190,281 @@ class MaterialsController < ApplicationController
               filename: "btrc-materials-#{ profile }.zip"
   end
 
-  def suppress_file
-    return head :unauthorized unless current_user
-    return head :forbidden unless current_user.admin?
+  private
 
-    material = Material.with_attached_file.find_by(id: params[:id])
-    return head :not_found unless material
+  def material_index_filters
+    tag_state = params[:tag_state].to_s.presence
+    tag_state = 'untagged' if bool?(:unclassified)
+    tag_state = 'all' unless ['all', 'tagged', 'untagged'].include?(tag_state)
 
-    reason = params[:reason].to_s.strip.presence
-    return render_unprocessable_entity('理由は必須です．', field: :reason) unless reason
-    purge = bool?(:purge)
-    file_snapshot = purge_material_file_snapshot(material) if purge
-    attachment = purge && material.file.attached? ? material.file.attachment : nil
-
-    Material.transaction do
-      MaterialVersionRecorder.ensure_snapshot!(material, created_by_user: current_user)
-      material.update!(file_suppressed_at: Time.current,
-                       file_suppressed_by_user: current_user,
-                       file_suppression_reason: reason,
-                       updated_by_user: current_user)
-      MaterialVersionRecorder.record!(material:, event_type: :suppress,
-                                      created_by_user: current_user,
-                                      file_snapshot:)
+    media_kind = params[:media_kind].to_s.presence
+    unless ['all', 'image', 'video', 'audio', 'file_other', 'url_only'].include?(media_kind)
+      media_kind = 'all'
     end
-    # Enqueue failure raises here after the suppress metadata has been committed.
-    # In that case the file remains suppressed in UI/ZIP and purge can be retried.
-    attachment&.purge_later
-    material.reload if purge
 
-    render json: MaterialRepr.base(material, host: request.base_url)
+    sort = params[:sort].to_s.presence
+    unless ['created_at', 'updated_at', 'tag_name', 'media_kind', 'file_byte_size',
+            'version_no', 'id'].include?(sort)
+      sort = 'created_at'
+    end
+
+    direction = params[:direction].to_s.downcase
+    direction = 'desc' unless ['asc', 'desc'].include?(direction)
+
+    group_by = params[:group_by].to_s.presence
+    group_by = 'none' unless ['none', 'parent_tag'].include?(group_by)
+
+    tag_id = params[:tag_id].to_i
+    tag_id = nil if tag_id <= 0
+
+    { q: params[:q].to_s.strip.presence,
+      tag_state:,
+      media_kind:,
+      tag_id:,
+      include_descendants: bool?(:include_descendants),
+      group_by:,
+      created_from: parse_time_param(:created_from),
+      created_to: parse_time_param(:created_to),
+      updated_from: parse_time_param(:updated_from),
+      updated_to: parse_time_param(:updated_to),
+      sort:,
+      direction: }
   end
 
-  private
+  def parse_time_param name
+    value = params[name].to_s.strip
+    return nil if value.blank?
+
+    Time.zone.parse(value)
+  rescue ArgumentError
+    nil
+  end
+
+  def material_index_needs_tag_name? filters
+    filters[:q].present? || filters[:sort] == 'tag_name'
+  end
+
+  def material_index_needs_file_blob? filters
+    filters[:q].present? ||
+        filters[:media_kind] != 'all' ||
+        ['media_kind', 'file_byte_size'].include?(filters[:sort])
+  end
+
+  def material_index_join_tag_name q
+    q.left_joins(tag: :tag_name)
+  end
+
+  def material_index_join_file_blob q
+    q.joins(<<~SQL.squish)
+      LEFT JOIN active_storage_attachments material_file_attachments
+        ON material_file_attachments.record_type = 'Material'
+       AND material_file_attachments.record_id = materials.id
+       AND material_file_attachments.name = 'file'
+      LEFT JOIN active_storage_blobs material_file_blobs
+        ON material_file_blobs.id = material_file_attachments.blob_id
+    SQL
+  end
+
+  def apply_material_query q, term
+    like = "%#{ ActiveRecord::Base.sanitize_sql_like(term) }%"
+    q.where('tag_names.name LIKE :q OR materials.url LIKE :q OR ' \
+            'material_file_blobs.filename LIKE :q',
+            q: like)
+  end
+
+  def apply_material_media_kind q, media_kind
+    case media_kind
+    when 'image'
+      q.where('material_file_blobs.content_type LIKE ?', 'image/%')
+    when 'video'
+      q.where('material_file_blobs.content_type LIKE ?', 'video/%')
+    when 'audio'
+      q.where('material_file_blobs.content_type LIKE ?', 'audio/%')
+    when 'file_other'
+      q.where('material_file_attachments.id IS NOT NULL')
+       .where.not('material_file_blobs.content_type LIKE ?', 'image/%')
+       .where.not('material_file_blobs.content_type LIKE ?', 'video/%')
+       .where.not('material_file_blobs.content_type LIKE ?', 'audio/%')
+    when 'url_only'
+      q.where('material_file_attachments.id IS NULL').where.not(url: [nil, ''])
+    else
+      q
+    end
+  end
+
+  def apply_material_tag_filter q, filters, tag_graph
+    return q unless filters[:tag_id]
+
+    tag_ids =
+        if tag_graph
+          tag_graph[:scope_tag_ids]
+        else
+          [filters[:tag_id]]
+        end
+
+    q.where(tag_id: tag_ids)
+  end
+
+  def material_index_tag_graph filters
+    return nil unless filters[:tag_id]
+
+    children_by_parent_id = Hash.new { |h, k| h[k] = [] }
+    TagImplication.pluck(:parent_tag_id, :tag_id).each do |parent_id, child_id|
+      children_by_parent_id[parent_id] << child_id
+    end
+
+    scope_tag_ids =
+        if filters[:include_descendants]
+          collect_material_descendant_ids(filters[:tag_id], children_by_parent_id)
+        else
+          Set.new([filters[:tag_id]])
+        end
+    tags_by_id =
+        Tag
+        .joins(:tag_name)
+        .where(id: scope_tag_ids)
+        .pluck('tags.id', 'tag_names.name', 'tags.category', 'tags.deprecated_at')
+        .each_with_object({ }) do |(id, name, category, deprecated_at), hash|
+          hash[id] = { id:, name:, category:, deprecated: deprecated_at.present? }
+        end
+
+    selected_tag = tags_by_id[filters[:tag_id]]
+    return nil unless selected_tag
+
+    group_tag_id_by_tag_id = { }
+    children_by_parent_id[filters[:tag_id]].each do |child_tag_id|
+      assign_material_group_branch(child_tag_id,
+                                   children_by_parent_id:,
+                                   tags_by_id:,
+                                   group_tag_id_by_tag_id:,
+                                   current_group_tag_id: nil,
+                                   seen: Set.new([filters[:tag_id]]))
+    end
+
+    { selected_tag_id: filters[:tag_id],
+      selected_tag:,
+      scope_tag_ids: scope_tag_ids.to_a,
+      tags_by_id:,
+      group_tag_id_by_tag_id: }
+  end
+
+  def collect_material_descendant_ids selected_tag_id, children_by_parent_id
+    ids = Set.new([selected_tag_id])
+    stack = [selected_tag_id]
+
+    until stack.empty?
+      tag_id = stack.pop
+      children_by_parent_id[tag_id].each do |child_tag_id|
+        next if ids.include?(child_tag_id)
+
+        ids << child_tag_id
+        stack << child_tag_id
+      end
+    end
+
+    ids
+  end
+
+  def assign_material_group_branch tag_id, children_by_parent_id:, tags_by_id:,
+                                   group_tag_id_by_tag_id:, current_group_tag_id:, seen:
+    return if seen.include?(tag_id)
+
+    tag = tags_by_id[tag_id]
+    return unless tag
+
+    seen = seen.dup << tag_id
+    next_group_tag_id = current_group_tag_id
+    next_group_tag_id = tag_id if next_group_tag_id.nil? && !tag[:deprecated]
+    group_tag_id_by_tag_id[tag_id] = next_group_tag_id if next_group_tag_id
+
+    children_by_parent_id[tag_id].each do |child_tag_id|
+      assign_material_group_branch(child_tag_id,
+                                   children_by_parent_id:,
+                                   tags_by_id:,
+                                   group_tag_id_by_tag_id:,
+                                   current_group_tag_id: next_group_tag_id,
+                                   seen:)
+    end
+  end
+
+  def material_index_groups materials, tag_graph
+    return [] unless tag_graph
+
+    groups_by_key = { }
+
+    materials.each do |material|
+      next unless material.tag_id
+
+      group_tag_id =
+          if material.tag_id == tag_graph[:selected_tag_id]
+            tag_graph[:selected_tag_id]
+          else
+            tag_graph[:group_tag_id_by_tag_id][material.tag_id] || tag_graph[:selected_tag_id]
+          end
+
+      group_tag = tag_graph[:tags_by_id][group_tag_id]
+      next unless group_tag
+
+      key = "tag:#{ group_tag_id }"
+      group =
+          groups_by_key[key] ||= { key:,
+                                   tag: group_tag_repr(group_tag),
+                                   material_ids: [],
+                                   count: 0 }
+      group[:material_ids] << material.id
+      group[:count] += 1
+    end
+
+    groups_by_key.values.sort_by { |group| group[:tag][:name] }
+  end
+
+  def material_index_tag_scope filters, tag_graph
+    return nil unless tag_graph
+
+    {
+      tag: group_tag_repr(tag_graph[:selected_tag]),
+      include_descendants: filters[:include_descendants]
+    }
+  end
+
+  def group_tag_repr group_tag
+    { id: group_tag[:id],
+      name: group_tag[:name],
+      category: group_tag[:category] }
+  end
+
+  def material_index_order_sql filters
+    direction = filters[:direction] == 'asc' ? 'ASC' : 'DESC'
+    sort_sql =
+        case filters[:sort]
+        when 'tag_name'
+          'tag_names.name'
+        when 'media_kind'
+          material_media_kind_sql
+        when 'file_byte_size'
+          'material_file_blobs.byte_size'
+        when 'updated_at'
+          'materials.updated_at'
+        when 'version_no'
+          'materials.version_no'
+        when 'id'
+          'materials.id'
+        else
+          'materials.created_at'
+        end
+
+    "#{ sort_sql } #{ direction }, materials.id #{ direction }"
+  end
+
+  def material_media_kind_sql
+    "CASE " \
+      "WHEN material_file_attachments.id IS NULL AND materials.url IS NOT NULL THEN 5 " \
+      "WHEN material_file_blobs.content_type LIKE 'image/%' THEN 1 " \
+      "WHEN material_file_blobs.content_type LIKE 'video/%' THEN 2 " \
+      "WHEN material_file_blobs.content_type LIKE 'audio/%' THEN 3 " \
+      "WHEN material_file_attachments.id IS NOT NULL THEN 4 " \
+      "ELSE 6 END"
+  end
 
   def upsert_export_paths! material
     raw = params[:export_paths]
@@ -248,37 +523,23 @@ class MaterialsController < ApplicationController
         content_type: file.content_type,
     )
 
-    if file_sha256.present?
-      blob.metadata['sha256'] = file_sha256
-      blob.save! if blob.changed?
-    end
+    MaterialFileSha256.assign_metadata_sha256!(blob, file_sha256)
 
     blob
   ensure
     file.tempfile.rewind if file&.tempfile
   end
 
-  def clear_file_suppression! material
-    material.file_suppressed_at = nil
-    material.file_suppressed_by_user = nil
-    material.file_suppression_reason = nil
-  end
-
-  def purge_material_file_snapshot material
-    return nil unless material.file.attached?
-
-    blob = material.file.blob
-
-    { file_blob_id: blob.id,
-      file_filename: blob.filename.to_s,
-      file_content_type: blob.content_type,
-      file_byte_size: blob.byte_size,
-      file_checksum: blob.checksum,
-      file_sha256: blob.metadata['sha256'] ||
-                   MaterialFileSha256.from_blob(blob, allow_download: true) }
-  end
-
   def render_material_import_block block
     render_validation_error fields: { file: ["抑止された素材です: #{ block.reason }"] }
   end
+
+  def log_thumbnail_generation material, result
+    material.reload
+    Rails.logger.info(
+        "Material thumbnail generation: material_id=#{ material.id } " \
+        "result=#{ result } " \
+        "thumbnail_attached=#{ material.thumbnail.attached? } " \
+        "content_type=#{ material.content_type }")
+  end
 end

backend/app/controllers/post_versions_controller.rb

@@ -25,6 +25,7 @@ class PostVersionsController < ApplicationController
         SQL
         .select('post_versions.*', 'prev.title AS prev_title', 'prev.url AS prev_url',
                 'prev.thumbnail_base AS prev_thumbnail_base', 'prev.tags AS prev_tags',
+                'prev.video_ms AS prev_video_ms',
                 'prev.original_created_from AS prev_original_created_from',
                 'prev.original_created_before AS prev_original_created_before')
     q = q.where('post_versions.post_id = ?', post_id) if post_id
@@ -74,6 +75,10 @@ class PostVersionsController < ApplicationController
           current: row.thumbnail_base,
           prev: row.attributes['prev_thumbnail_base']
         },
+        video_ms: {
+          current: row.video_ms,
+          prev: row.attributes['prev_video_ms']
+        },
         tags: build_version_tags(cur_tags, prev_tags),
         original_created_from: {
           current: row.original_created_from&.iso8601,

backend/app/controllers/posts_controller.rb

@@ -1,6 +1,10 @@
 class PostsController < ApplicationController
   Event = Struct.new(:post, :tag, :user, :change_type, :timestamp, keyword_init: true)
 
+  class VideoMsParseError < ArgumentError
+    ;
+  end
+
   def index
     url = params[:url].presence
     title = params[:title].presence
@@ -45,7 +49,9 @@ class PostsController < ApplicationController
         .joins("LEFT JOIN (#{ pt_max_sql }) pt_max ON pt_max.post_id = posts.id")
         .reselect('posts.*', Arel.sql("#{ updated_at_all_sql } AS updated_at_all"))
         .preload(:uploaded_user, :parents, :children,
-                 tags: [:deerjikists, :materials, { tag_name: :wiki_page }])
+                 active_post_tags: [:sections,
+                                    { tag: [:deerjikists, :materials,
+                                            { tag_name: :wiki_page }] }])
         .with_attached_thumbnail
 
     q = q.where('posts.url LIKE ?', "%#{ url }%") if url
@@ -97,7 +103,9 @@ class PostsController < ApplicationController
 
   def random
     post = filtered_posts.preload(:uploaded_user, :parents, :children,
-                                  tags: [:deerjikists, :materials, { tag_name: :wiki_page }])
+                                  active_post_tags: [:sections,
+                                                     { tag: [:deerjikists, :materials,
+                                                             { tag_name: :wiki_page }] }])
                          .with_attached_thumbnail
                          .order('RAND()')
                          .first
@@ -110,7 +118,9 @@ class PostsController < ApplicationController
     post =
         Post
         .includes(:uploaded_user, :parents, :children,
-                  tags: [:deerjikists, :materials, { tag_name: :wiki_page }])
+                  active_post_tags: [:sections,
+                                     { tag: [:deerjikists, :materials,
+                                             { tag_name: :wiki_page }] }])
         .with_attached_thumbnail
         .find_by(id: params[:id])
     return head :not_found unless post
@@ -125,7 +135,7 @@ class PostsController < ApplicationController
                                  child_posts:,
                                  sibling_posts:,
                                  related:)
-                         .merge(tags: build_tag_tree_for(post.tags))
+                         .merge(tags: build_tag_tree_for(post))
   end
 
   def create
@@ -140,24 +150,27 @@ class PostsController < ApplicationController
     original_created_from = params[:original_created_from]
     original_created_before = params[:original_created_before]
     parent_post_ids = parse_parent_post_ids
+    resized_thumbnail = thumbnail.present? ? Post.resized_thumbnail_attachment(thumbnail) : nil
 
     post = Post.new(title:, url:, thumbnail_base: nil, uploaded_user: current_user,
                     original_created_from:, original_created_before:)
-    post.thumbnail.attach(thumbnail) if thumbnail.present?
+    post.thumbnail.attach(resized_thumbnail) if resized_thumbnail
 
     ApplicationRecord.transaction do
       post.save!
 
-      tags = Tag.normalise_tags!(tag_names, deny_deprecated: true)
+      Tag.normalise_tags!(tag_names, deny_deprecated: true, with_sections: true) =>
+          { tags:, sections: }
       TagVersioning.record_tag_snapshots!(tags, created_by_user: current_user)
 
       tags = Tag.expand_parent_tags(tags).reject(&:deprecated?)
-      sync_post_tags!(post, tags)
+      post.video_ms = normalise_video_ms(tags)
+      validate_video_sections!(post.video_ms, sections)
+      post.save!
+      sync_post_tags!(post, tags, sections)
 
       sync_parent_posts!(post, parent_post_ids)
 
-      post.resized_thumbnail!
-
       PostVersionRecorder.record!(post:, event_type: :create, created_by_user: current_user)
     end
 
@@ -167,6 +180,12 @@ class PostsController < ApplicationController
     render_validation_error fields: { tags: 'ニコニコ・タグは直接指定できません．' }
   rescue Tag::DeprecatedTagNormalisationError
     render_unprocessable_entity '廃止済みタグは付与できません．', field: :tags
+  rescue Tag::SectionLiteralParseError
+    render_validation_error fields: { tags: ['タグ区間の記法が不正です．'] }
+  rescue VideoMsParseError
+    render_validation_error fields: { video_ms: ['動画時間の記法が不正です．'] }
+  rescue MiniMagick::Error
+    render_validation_error fields: { thumbnail: ['サムネイル画像の変換に失敗しました．'] }
   rescue ArgumentError => e
     render_validation_error fields: { parent_post_ids: [e.message] }
   rescue ActiveRecord::RecordInvalid => e
@@ -223,6 +242,8 @@ class PostsController < ApplicationController
                                                  original_created_from:,
                                                  original_created_before:,
                                                  tag_names:,
+                                                 video_ms_param: params[:video_ms],
+                                                 duration_param: params[:duration],
                                                  parent_post_ids:)
 
       snapshot_to_apply =
@@ -253,12 +274,16 @@ class PostsController < ApplicationController
 
     post.reload
     json = PostRepr.base(post, current_user)
-    json['tags'] = build_tag_tree_for(post.tags)
+    json['tags'] = build_tag_tree_for(post)
     render json:, status: :ok
   rescue Tag::NicoTagNormalisationError
     render_validation_error fields: { tags: ['ニコニコ・タグは直接指定できません．'] }
   rescue Tag::DeprecatedTagNormalisationError
     render_unprocessable_entity '廃止済みタグは付与できません．', field: :tags
+  rescue Tag::SectionLiteralParseError
+    render_validation_error fields: { tags: ['タグ区間の記法が不正です．'] }
+  rescue VideoMsParseError
+    render_validation_error fields: { video_ms: ['動画時間の記法が不正です．'] }
   rescue ArgumentError => e
     render_validation_error fields: { parent_post_ids: [e.message] }
   rescue ActiveRecord::RecordInvalid => e
@@ -357,7 +382,7 @@ class PostsController < ApplicationController
   def tagged_post_ids_for(name) =
       Post.joins(tags: :tag_name).where(tag_names: { name: }).select(:id)
 
-  def sync_post_tags! post, desired_tags
+  def sync_post_tags! post, desired_tags, sections
     desired_tags.each do |t|
       t.save! if t.new_record?
     end
@@ -376,13 +401,21 @@ class PostsController < ApplicationController
       end
     end
 
+    PostTagSection.where(post_id: post.id).destroy_all
+    sections.each do |tag_id, ranges|
+      ranges.each do |begin_ms, end_ms|
+        PostTagSection.create!(post_id: post.id, tag_id:, begin_ms:, end_ms:)
+      end
+    end
+
     PostTag.where(post_id: post.id, tag_id: to_remove.to_a).kept.find_each do |pt|
       pt.discard_by!(current_user)
     end
   end
 
-  def build_tag_tree_for tags
-    tags = tags.reject(&:deprecated?).to_a
+  def build_tag_tree_for post
+    post_tags = post.active_post_tags.reject { |post_tag| post_tag.tag.deprecated? }
+    tags = post_tags.map(&:tag)
     tag_ids = tags.map(&:id)
 
     implications = TagImplication.where(parent_tag_id: tag_ids, tag_id: tag_ids)
@@ -397,6 +430,9 @@ class PostsController < ApplicationController
     root_ids = tag_ids - child_ids
 
     tags_by_id = tags.index_by(&:id)
+    sections_by_tag_id = post_tags.to_h { |post_tag|
+      [post_tag.tag_id, post_tag.sections.as_json(only: [:begin_ms, :end_ms])]
+    }
 
     memo = { }
 
@@ -404,8 +440,10 @@ class PostsController < ApplicationController
       tag = tags_by_id[tag_id]
       return nil unless tag
 
+      sections = sections_by_tag_id.fetch(tag_id, [])
+
       if path.include?(tag_id)
-        return TagRepr.inline(tag).merge(children: [])
+        return TagRepr.inline(tag).merge(children: [], sections:)
       end
 
       if memo.key?(tag_id)
@@ -417,7 +455,7 @@ class PostsController < ApplicationController
 
       children = child_ids.filter_map { |cid| build_node.(cid, new_path) }
 
-      memo[tag_id] = TagRepr.inline(tag).merge(children:)
+      memo[tag_id] = TagRepr.inline(tag).merge(children:, sections:)
     end
 
     root_ids.filter_map { |id| build_node.call(id, []) }
@@ -486,6 +524,7 @@ class PostsController < ApplicationController
 
   def post_snapshot_from_version version
     { title: version.title,
+      video_ms: version.respond_to?(:video_ms) ? version.video_ms : nil,
       original_created_from: snapshot_time(version.original_created_from),
       original_created_before: snapshot_time(version.original_created_before),
       tag_names: editable_tag_names_from_version(version),
@@ -498,6 +537,7 @@ class PostsController < ApplicationController
 
   def post_snapshot_from_record post
     { title: post.title,
+      video_ms: post.video_ms,
       original_created_from: snapshot_time(post.original_created_from),
       original_created_before: snapshot_time(post.original_created_before),
       tag_names: editable_tag_names_from_post(post),
@@ -505,16 +545,41 @@ class PostsController < ApplicationController
   end
 
   def editable_tag_names_from_post post
-    post.tags.not_nico.where(deprecated_at: nil)
-        .joins(:tag_name).order('tag_names.name').pluck('tag_names.name')
+    post
+        .post_tags
+        .kept
+        .joins(tag: :tag_name)
+        .merge(Tag.not_nico)
+        .merge(Tag.where(deprecated_at: nil))
+        .includes(:sections, tag: :tag_name)
+        .order('tag_names.name')
+        .map do |post_tag|
+      name = post_tag.tag.tag_name.name
+      sections = post_tag.sections.sort_by(&:begin_ms)
+
+      next name if sections.empty?
+
+      "#{ name }#{ sections.map { Post.section_literal(_1) }.join }"
+    end
   end
 
   def post_incoming_snapshot title:, original_created_from:, original_created_before:,
-                             tag_names:, parent_post_ids:
+                             tag_names:, video_ms_param:, duration_param:, parent_post_ids:
+    Tag.normalise_tags!(tag_names, with_tagme: false, deny_deprecated: true,
+                                        with_sections: true) =>
+        { tags:, sections: }
+
+    tags = Tag.expand_parent_tags(tags).reject(&:deprecated?)
+    video_ms = normalise_video_ms(tags, video_ms_param:, duration_param:)
+    validate_video_sections!(video_ms, sections)
+
     { title:,
+      video_ms:,
       original_created_from: snapshot_time(original_created_from),
       original_created_before: snapshot_time(original_created_before),
-      tag_names: incoming_tag_names_for_snapshot(tag_names),
+      tag_names: tags.uniq(&:id).map { |tag|
+        "#{ tag.name }#{ sections[tag.id].to_a.map { section_literal(_1) }.join }"
+      }.sort,
       parent_post_ids: parent_post_ids.sort }
   end
 
@@ -537,11 +602,8 @@ class PostsController < ApplicationController
     value.to_s
   end
 
-  def incoming_tag_names_for_snapshot raw_tag_names
-    tags = Tag.normalise_tags!(raw_tag_names, with_tagme: false,
-                                              deny_deprecated: true)
-
-    Tag.expand_parent_tags(tags).reject(&:deprecated?).map(&:name).uniq.sort
+  def section_literal section
+    "[#{ Post.ms_to_time(section[0]) }-#{ section[1] ? Post.ms_to_time(section[1]) : '' }]"
   end
 
   def post_conflict_json post:, base_version_no:, base_snapshot:,
@@ -562,6 +624,8 @@ class PostsController < ApplicationController
   def post_snapshot_changes base_snapshot, current_snapshot, incoming_snapshot
     [scalar_snapshot_change(:title, 'タイトル',
                             base_snapshot, current_snapshot, incoming_snapshot),
+     scalar_snapshot_change(:video_ms, '動画時間',
+                            base_snapshot, current_snapshot, incoming_snapshot),
      scalar_snapshot_change(:original_created_from, 'オリジナルの作成日時（以降）',
                             base_snapshot, current_snapshot, incoming_snapshot),
      scalar_snapshot_change(:original_created_before, 'オリジナルの作成日時（より前）',
@@ -625,11 +689,14 @@ class PostsController < ApplicationController
     PostVersionRecorder.ensure_snapshot!(post, created_by_user: current_user)
 
     post.update!(title: snapshot[:title],
+                 video_ms: snapshot[:video_ms],
                  original_created_from: snapshot[:original_created_from],
                  original_created_before: snapshot[:original_created_before])
 
-    editable_tags = Tag.normalise_tags!(snapshot[:tag_names], with_tagme: false,
-                                                               deny_deprecated: true)
+    Tag.normalise_tags!(snapshot[:tag_names], with_tagme: false,
+                                               deny_deprecated: true,
+                                               with_sections: true) =>
+        { tags: editable_tags, sections: }
     TagVersioning.record_tag_snapshots!(editable_tags, created_by_user: current_user)
 
     readonly_tags = post.tags.nico.to_a
@@ -637,14 +704,17 @@ class PostsController < ApplicationController
     tags = readonly_tags + editable_tags
     tags = Tag.expand_parent_tags(tags).reject(&:deprecated?)
 
-    sync_post_tags!(post, tags)
+    post.video_ms = tags.any? { _1.id == Tag.video.id } ? snapshot[:video_ms] : nil
+    validate_video_sections!(post.video_ms, sections)
+    post.save!
+    sync_post_tags!(post, tags, sections)
     sync_parent_posts!(post, snapshot[:parent_post_ids])
 
     PostVersionRecorder.record!(post:, event_type: :update, created_by_user: current_user)
   end
 
   def merge_post_snapshots base_snapshot, current_snapshot, incoming_snapshot
-    [:title, :original_created_from, :original_created_before].map {
+    [:title, :video_ms, :original_created_from, :original_created_before].map {
       [_1, merge_scalar_snapshot_value(base_snapshot[_1],
                                        current_snapshot[_1],
                                        incoming_snapshot[_1])]
@@ -688,4 +758,44 @@ class PostsController < ApplicationController
       render_validation_error record
     end
   end
+
+  def normalise_video_ms tags, video_ms_param: params[:video_ms], duration_param: params[:duration]
+    return nil unless tags.any? { _1.id == Tag.video.id }
+
+    if video_ms_param.present?
+      video_ms = Integer(video_ms_param, exception: false)
+      raise VideoMsParseError unless video_ms&.positive?
+
+      return video_ms
+    end
+
+    return nil if duration_param.blank?
+
+    video_ms = Tag.time_to_ms!(duration_param.to_s, tag_name: '動画時間')
+    raise VideoMsParseError unless video_ms.positive?
+
+    video_ms
+  rescue Tag::SectionLiteralParseError
+    raise VideoMsParseError
+  end
+
+  def validate_video_sections! video_ms, sections
+    return unless video_ms
+
+    sections.each_value do |ranges|
+      ranges.each do |begin_ms, end_ms|
+        if begin_ms >= video_ms
+          post = Post.new
+          post.errors.add :video_ms, 'タグ区間の開始が動画時間以上です．'
+          raise ActiveRecord::RecordInvalid, post
+        end
+
+        if end_ms && end_ms > video_ms
+          post = Post.new
+          post.errors.add :video_ms, 'タグ区間の終端が動画時間を超えてゐます．'
+          raise ActiveRecord::RecordInvalid, post
+        end
+      end
+    end
+  end
 end

backend/app/controllers/tags_controller.rb

@@ -82,8 +82,9 @@ class TagsController < ApplicationController
   def with_depth
     parent_tag_id = params[:parent].to_i
     parent_tag_id = nil if parent_tag_id <= 0
+    material_filter = material_filter_param(default: 'any')
 
-    graph = build_with_depth_graph
+    graph = build_with_depth_graph(material_filter)
 
     tag_ids =
         if parent_tag_id
@@ -92,19 +93,9 @@ class TagsController < ApplicationController
           visible_root_tag_ids(graph)
         end
 
-    tags =
-        Tag
-        .joins(:tag_name)
-        .includes(:tag_name, :materials, tag_name: :wiki_page)
-        .where(id: tag_ids)
-        .order('tag_names.name')
-        .distinct
-        .to_a
-
-    render json: tags.map { |tag|
-      TagRepr.base(tag).merge(has_children: visible_child_tag_ids(tag.id, graph).present?,
-                              children: [])
-    }
+    render json: tag_ids
+                 .sort_by { |tag_id| graph[:tags_by_id][tag_id][:name] }
+                 .map { |tag_id| with_depth_lightweight_repr(tag_id, graph) }
   end
 
   def autocomplete
@@ -229,13 +220,16 @@ class TagsController < ApplicationController
   def materials_by_name
     name = params[:name].to_s.strip
     return render_bad_request('name は必須です．') if name.blank?
+    material_filter = material_filter_param(default: 'any')
 
     tag = Tag.joins(:tag_name)
              .includes(:tag_name, :materials, tag_name: :wiki_page)
              .find_by(tag_names: { name: })
     return head :not_found unless tag
 
-    render json: build_tag_children(tag)
+    graph = build_with_depth_graph(material_filter)
+
+    render json: build_tag_children(tag, graph:)
   end
 
   def update_all
@@ -251,10 +245,7 @@ class TagsController < ApplicationController
     return render_unprocessable_entity('カテゴリは必須です．', field: :category) if category.blank?
     return render_unprocessable_entity '廃止状態は必須です．', field: :deprecated unless params.key?(:deprecated)
 
-    if (name != tag.name &&
-        tag.in?([Tag.tagme, Tag.bot, Tag.no_deerjikist, Tag.video, Tag.niconico]))
-      return render_unprocessable_entity 'システム・タグの名称は変更できません．', field: :name
-    end
+    return unless validate_tag_rename(tag, name)
 
     alias_names = params[:aliases].to_s.split.uniq
     parent_names = params[:parent_tags].to_s.split.uniq
@@ -280,7 +271,7 @@ class TagsController < ApplicationController
       else
         tag.update!(category:, deprecated_at: deprecated ? Time.current : nil)
       end
-      tag.tag_name.update!(name:)
+      rename_tag_name!(tag, name) if name_changed
 
       alias_names << old_name if name_changed
       alias_names.delete(name)
@@ -316,6 +307,8 @@ class TagsController < ApplicationController
       return render_unprocessable_entity 'ニコタグは廃止できません．', field: :deprecated
     end
 
+    return unless validate_tag_rename(tag, name)
+
     if tag.nico? || (category.present? && category == 'nico')
       return render_unprocessable_entity 'ニコタグは変更できません．', field: :category
     end
@@ -327,7 +320,7 @@ class TagsController < ApplicationController
       name_changed = name.present? && name != old_name
       wiki_page = tag.tag_name.wiki_page if name_changed
 
-      tag.tag_name.update!(name:) if name.present?
+      rename_tag_name!(tag, name) if name_changed
       tag.update!(category:) if category.present?
       if deprecated_given && tag.deprecated? != deprecated
         tag.update!(deprecated_at: deprecated ? Time.current : nil)
@@ -348,7 +341,14 @@ class TagsController < ApplicationController
 
   private
 
-  def build_with_depth_graph
+  def material_filter_param default:
+    value = params[:material_filter].to_s.presence
+    return default unless ['present', 'missing', 'any'].include?(value)
+
+    value
+  end
+
+  def build_with_depth_graph material_filter
     children_by_parent_id = Hash.new { |h, k| h[k] = [] }
     parent_ids_by_child_id = Hash.new { |h, k| h[k] = [] }
 
@@ -361,23 +361,37 @@ class TagsController < ApplicationController
                parent_ids_by_child_id.keys +
                Tag.where(category: ['meme', 'character', 'material']).pluck(:id)).uniq
 
-    tags_by_id = Tag.where(id: tag_ids)
-                    .pluck(:id, :category, :deprecated_at)
-                    .each_with_object({ }) do |(id, category, deprecated_at), h|
-      h[id] = { category:, deprecated: deprecated_at.present? }
+    material_tag_ids = Material.unscoped.kept.where.not(tag_id: nil).distinct.pluck(:tag_id).to_set
+
+    tags_by_id = Tag.joins(:tag_name)
+                    .where(id: tag_ids)
+                    .pluck('tags.id', 'tag_names.name', 'tags.category', 'tags.deprecated_at')
+                    .each_with_object({ }) do |(id, name, category, deprecated_at), h|
+      h[id] = { name:, category:, deprecated: deprecated_at.present?,
+                has_material: material_tag_ids.include?(id) }
     end
 
     { children_by_parent_id:, parent_ids_by_child_id:, tags_by_id:,
-      visible_child_tag_ids_by_parent_id: { } }
+      visible_child_tag_ids_by_parent_id: { },
+      visible_subtree_by_tag_id: { },
+      material_filter: }
   end
 
   def visible_root_tag_ids graph
-    graph[:tags_by_id].filter_map do |tag_id, attrs|
-      next unless with_depth_visible_tag?(attrs)
-      next unless visible_root_tag?(tag_id, graph)
+    root_ids = Set.new
 
-      tag_id
+    graph[:tags_by_id].each do |tag_id, attrs|
+      next unless visible_root_tag?(tag_id, graph)
+      next unless visible_subtree?(tag_id, graph)
+
+      if attrs[:deprecated]
+        collect_visible_child_tag_ids(tag_id, graph, root_ids, Set.new)
+      else
+        root_ids << tag_id
+      end
     end
+
+    root_ids.to_a
   end
 
   def visible_root_tag? tag_id, graph
@@ -428,18 +442,76 @@ class TagsController < ApplicationController
       return
     end
 
-    visible_ids << tag_id if with_depth_visible_tag?(tag)
+    if with_depth_visible_tag?(tag, graph[:material_filter])
+      visible_ids << tag_id
+      return
+    end
+
+    visible_ids << tag_id if graph[:children_by_parent_id][tag_id].any? { |child_tag_id|
+      visible_subtree?(child_tag_id, graph)
+    }
   end
 
-  def with_depth_visible_tag? tag
-    tag[:category].in?(['meme', 'character', 'material']) && !tag[:deprecated]
+  def with_depth_visible_tag? tag, material_filter
+    return false unless tag[:category].in?(['meme', 'character', 'material']) && !tag[:deprecated]
+
+    case material_filter
+    when 'present'
+      tag[:has_material]
+    when 'missing'
+      !tag[:has_material]
+    else
+      true
+    end
   end
 
-  def build_tag_children tag
+  def visible_subtree? tag_id, graph
+    cache = graph[:visible_subtree_by_tag_id]
+    return cache[tag_id] if cache.key?(tag_id)
+
+    tag = graph[:tags_by_id][tag_id]
+    return cache[tag_id] = false unless tag
+
+    if tag[:deprecated]
+      return cache[tag_id] =
+                 graph[:children_by_parent_id][tag_id].any? { |child_tag_id|
+                   visible_subtree?(child_tag_id, graph)
+                 }
+    end
+
+    cache[tag_id] =
+        with_depth_visible_tag?(tag, graph[:material_filter]) ||
+        graph[:children_by_parent_id][tag_id].any? { |child_tag_id|
+          visible_subtree?(child_tag_id, graph)
+        }
+  end
+
+  def with_depth_lightweight_repr tag_id, graph
+    tag = graph[:tags_by_id][tag_id]
+
+    { id: tag_id,
+      name: tag[:name],
+      category: tag[:category],
+      deprecated: tag[:deprecated],
+      has_material: tag[:has_material],
+      has_children: visible_child_tag_ids(tag_id, graph).present?,
+      children: [] }
+  end
+
+  def build_tag_children tag, graph: nil
     material = tag.materials.first
+    tag_graph = graph && graph[:tags_by_id][tag.id]
+    material =
+        nil if tag_graph && !with_depth_visible_tag?(tag_graph, graph[:material_filter])
+
+    children = tag.children.sort_by(&:name)
+    if graph
+      children = children.filter { |child_tag| visible_subtree?(child_tag.id, graph) }
+    end
 
     TagRepr.base(tag).merge(
-        children: tag.children.sort_by { _1.name }.map { build_tag_children(_1) },
+        children: children.map { build_tag_children(_1, graph:) },
+        has_material: tag_graph ? tag_graph[:has_material] : material.present?,
         material: material && MaterialRepr.base(material, host: request.base_url))
   end
 
@@ -462,6 +534,67 @@ class TagsController < ApplicationController
         created_by_user:)
   end
 
+  def validate_tag_rename tag, name
+    return true if name.blank? || name == tag.name
+
+    if tag.in?([Tag.tagme, Tag.bot, Tag.no_deerjikist, Tag.video, Tag.niconico])
+      render_unprocessable_entity 'システム・タグの名称は変更できません．', field: :name
+      return false
+    end
+
+    target_tag_name = TagName.with_discarded.find_by(name:)
+    return true if target_tag_name.nil?
+    return true if target_tag_name.canonical_id?
+
+    render_unprocessable_entity 'その名前は既に使はれてゐます．', field: :name
+    false
+  end
+
+  def rename_tag_name! tag, name
+    return if name == tag.name
+
+    current_tag_name = tag.tag_name
+    target_tag_name = TagName.with_discarded.find_by(name:)
+
+    if target_tag_name.nil?
+      current_tag_name.update!(name:)
+      return
+    end
+
+    promote_tag_alias!(
+        tag,
+        current_tag_name:,
+        promoted_tag_name: target_tag_name)
+  end
+
+  def promote_tag_alias! tag, current_tag_name:, promoted_tag_name:
+    old_owner_tag = promoted_tag_name.canonical&.tag
+
+    if old_owner_tag && old_owner_tag != tag
+      TagVersioning.ensure_snapshot!(old_owner_tag, created_by_user: current_user)
+    end
+
+    promoted_tag_name.undiscard! if promoted_tag_name.discarded?
+    promoted_tag_name.update!(canonical: nil)
+
+    TagName.with_discarded
+           .where(canonical_id: current_tag_name.id)
+           .where.not(id: promoted_tag_name.id)
+           .find_each do |alias_tag_name|
+      alias_tag_name.update!(canonical: promoted_tag_name)
+    end
+
+    current_tag_name.wiki_page&.update!(tag_name: promoted_tag_name)
+    tag.update!(tag_name: promoted_tag_name)
+    current_tag_name.association(:wiki_page).reset
+    current_tag_name.association(:tag).reset
+    current_tag_name.reload.update!(canonical: promoted_tag_name)
+
+    return unless old_owner_tag && old_owner_tag != tag
+
+    record_tag_version!(old_owner_tag.reload, event_type: :update, created_by_user: current_user)
+  end
+
   def update_aliases! tag, alias_names
     alias_names = alias_names.uniq
 

backend/app/models/material.rb

@@ -1,6 +1,9 @@
 class Material < ApplicationRecord
   include MyDiscard
 
+  SOURCE_KINDS = ['uri', 'google_drive_path', 'google_drive_file',
+                  'legacy_drive_path'].freeze
+
   default_scope -> { kept }
 
   belongs_to :parent, class_name: 'Material', optional: true
@@ -9,26 +12,40 @@ class Material < ApplicationRecord
   belongs_to :tag, optional: true
   belongs_to :created_by_user, class_name: 'User', optional: true
   belongs_to :updated_by_user, class_name: 'User', optional: true
-  belongs_to :file_suppressed_by_user, class_name: 'User', optional: true
 
   has_many :material_versions, dependent: :destroy
   has_many :material_export_items, dependent: :destroy
 
   has_one_attached :file, dependent: :purge
+  has_one_attached :thumbnail, dependent: :purge
 
-  validates :tag_id, presence: true, uniqueness: true
+  before_validation :assign_normalized_source_key
+
+  validates :tag_id, uniqueness: true, allow_nil: true
+  validates :source_kind,
+            inclusion: { in: SOURCE_KINDS },
+            allow_blank: true
 
   validate :file_must_be_attached
   validate :tag_must_be_material_category
 
   def content_type
-    return nil if file_suppressed?
     return nil unless file&.attached?
 
     file.blob.content_type
   end
 
-  def file_suppressed? = file_suppressed_at.present?
+  def file_byte_size
+    return nil unless file&.attached?
+
+    file.blob.byte_size
+  end
+
+  def file_filename
+    return nil unless file&.attached?
+
+    file.blob.filename.to_s
+  end
 
   def snapshot_export_paths
     material_export_items.order(:profile).pluck(:profile, :export_path).to_h
@@ -36,6 +53,19 @@ class Material < ApplicationRecord
 
   private
 
+  def assign_normalized_source_key
+    if source_kind.blank?
+      self.normalized_source_key = nil
+      return
+    end
+
+    self.normalized_source_key =
+        MaterialSyncSuppression.normalize_source_key(source_kind:,
+                                                     source_uri:,
+                                                     drive_path: source_path,
+                                                     drive_file_id: source_file_id)
+  end
+
   def file_must_be_attached
     return if url.present? || file.attached?
 

backend/app/models/material_sync_source.rb

@@ -0,0 +1,45 @@
+class MaterialSyncSource < ApplicationRecord
+  SOURCE_KINDS = ['uri', 'google_drive_path', 'google_drive_file', 'legacy_drive_path'].freeze
+
+  belongs_to :created_by_user, class_name: 'User', optional: true
+  belongs_to :updated_by_user, class_name: 'User', optional: true
+
+  validates :name, presence: true
+  validates :source_kind,
+            presence: true,
+            inclusion: { in: SOURCE_KINDS }
+  validates :profile, presence: true, inclusion: { in: MaterialExportItem::VALID_PROFILES }
+  validate :source_value_must_be_present
+
+  scope :enabled, -> { where(enabled: true) }
+
+  def normalized_source_key
+    MaterialSyncSuppression.normalize_source_key(source_kind:,
+                                                 source_uri:,
+                                                 source_path:,
+                                                 source_file_id:)
+  end
+
+  private
+
+  def source_value_must_be_present
+    return if source_value_present?
+
+    errors.add(:base, '同期元を指定してください．')
+  end
+
+  def source_value_present?
+    case source_kind
+    when 'uri'
+      source_uri.present?
+    when 'google_drive_file'
+      source_file_id.present? || source_uri.present?
+    when 'google_drive_path'
+      source_file_id.present? || source_uri.present?
+    when 'legacy_drive_path'
+      source_path.present?
+    else
+      normalized_source_key.present?
+    end
+  end
+end

backend/app/models/material_sync_suppression.rb

@@ -0,0 +1,105 @@
+class MaterialSyncSuppression < ApplicationRecord
+  SOURCE_KINDS = [
+    'uri',
+    'google_drive_path',
+    'google_drive_path_prefix',
+    'google_drive_file',
+    'legacy_drive_path',
+    'legacy_drive_path_prefix'
+  ].freeze
+
+  REASONS = [
+    'copyright_high_risk',
+    'copyright_takedown',
+    'adult_or_sensitive',
+    'personal_information',
+    'malware_or_dangerous_file',
+    'duplicate_or_low_quality',
+    'source_owner_request',
+    'other'
+  ].freeze
+
+  belongs_to :created_by_user, class_name: 'User', optional: true
+
+  before_validation :assign_normalized_source_key
+
+  validates :source_kind, presence: true, inclusion: { in: SOURCE_KINDS }
+  validates :reason, presence: true, inclusion: { in: REASONS }
+  validates :normalized_source_key, presence: true, uniqueness: true
+  validate :source_value_must_be_present
+  validate :drive_path_must_be_safe_relative_path
+
+  def self.normalize_source_key source_kind:,
+                                source_uri: nil,
+                                drive_path: nil,
+                                drive_file_id: nil,
+                                source_path: nil,
+                                source_file_id: nil
+    kind = source_kind.to_s
+    value =
+        case kind
+        when 'uri'
+          source_uri.to_s.strip
+        when 'google_drive_path', 'google_drive_path_prefix',
+             'legacy_drive_path', 'legacy_drive_path_prefix'
+          (source_path || drive_path).to_s.strip.gsub(%r{/+}, '/')
+        when 'google_drive_file'
+          (source_file_id || drive_file_id).to_s.strip
+        else
+          ''
+        end
+
+    return nil if kind.blank? || value.blank?
+
+    "#{ kind }:#{ value }"
+  end
+
+  private
+
+  def assign_normalized_source_key
+    normalize_path_fields!
+    self.normalized_source_key =
+        self.class.normalize_source_key(source_kind:,
+                                        source_uri:,
+                                        drive_path:,
+                                        drive_file_id:)
+  end
+
+  def source_value_must_be_present
+    return if normalized_source_key.present?
+
+    errors.add(:base, '同期元を指定してください．')
+  end
+
+  def drive_path_must_be_safe_relative_path
+    return unless source_kind.in?(
+        ['google_drive_path', 'google_drive_path_prefix',
+         'legacy_drive_path', 'legacy_drive_path_prefix'])
+
+    value = drive_path.to_s
+    return if value.blank?
+
+    if value.start_with?('/') || value.match?(/\A[A-Za-z]:\//)
+      errors.add(:drive_path, '相対 path を指定してください．')
+    end
+    if value.start_with?('My Drive/', 'マイドライブ/')
+      errors.add(:drive_path, '同期元フォルダからの相対 path を指定してください．')
+    end
+    errors.add(:drive_path, 'NUL は使へません．') if value.include?("\0")
+    errors.add(:drive_path, '連続スラッシュは使へません．') if value.include?('//')
+    errors.add(:drive_path, '末尾スラッシュは使へません．') if value.end_with?('/')
+
+    parts = value.split('/')
+    if parts.any? { |part| part.in?(['.', '..']) }
+      errors.add(:drive_path, '. や .. は使へません．')
+    end
+  end
+
+  def normalize_path_fields!
+    return unless source_kind.in?(
+        ['google_drive_path', 'google_drive_path_prefix',
+         'legacy_drive_path', 'legacy_drive_path_prefix'])
+
+    self.drive_path = drive_path.to_s.tr('\\', '/').strip.presence
+  end
+end

backend/app/models/material_version.rb

@@ -2,8 +2,7 @@ class MaterialVersion < ApplicationRecord
   EVENT_TYPE_MAP = { create: 'create',
                      update: 'update',
                      discard: 'discard',
-                     restore: 'restore',
-                     suppress: 'suppress' }.freeze
+                     restore: 'restore' }.freeze
 
   include VersionRecord
 

backend/app/models/post.rb

@@ -1,5 +1,19 @@
 class Post < ApplicationRecord
   require 'mini_magick'
+  require 'stringio'
+
+  def self.resized_thumbnail_attachment(upload)
+    upload.rewind
+    image = MiniMagick::Image.read(upload.read)
+    image.resize '180x180'
+    image.format 'jpg'
+
+    { io: StringIO.new(image.to_blob),
+      filename: 'resized_thumbnail.jpg',
+      content_type: 'image/jpeg' }
+  ensure
+    upload.rewind
+  end
 
   belongs_to :uploaded_user, class_name: 'User', optional: true
 
@@ -46,6 +60,7 @@ class Post < ApplicationRecord
   before_validation :normalise_url
 
   validates :url, presence: true, uniqueness: true
+  validates :video_ms, numericality: { only_integer: true, greater_than: 0 }, allow_nil: true
 
   validate :validate_original_created_range
   validate :url_must_be_http_url
@@ -69,7 +84,42 @@ class Post < ApplicationRecord
     super(options).merge(thumbnail: nil)
   end
 
-  def snapshot_tag_names = tags.joins(:tag_name).order('tag_names.name').pluck('tag_names.name')
+  def snapshot_tag_names
+    post_tags
+        .kept
+        .joins(tag: :tag_name)
+        .includes(:sections, tag: :tag_name)
+        .order('tag_names.name')
+        .map do |post_tag|
+      name = post_tag.tag.tag_name.name
+      sections = post_tag.sections.sort_by(&:begin_ms)
+
+      next name if sections.empty?
+
+      "#{ name }#{ sections.map { Post.section_literal(_1) }.join }"
+    end
+  end
+
+  def self.section_literal section
+    "[#{ Post.ms_to_time(section.begin_ms) }-#{ section.end_ms ? Post.ms_to_time(section.end_ms) : '' }]"
+  end
+
+  def self.ms_to_time ms
+    total_s = ms / 1_000
+    s = total_s % 60
+    min = (total_s / 60) % 60
+    h = total_s / 3_600
+    remainder_ms = ms % 1_000
+
+    base =
+        if h.positive?
+          '%d:%02d:%02d' % [h, min, s]
+        else
+          '%d:%02d' % [min, s]
+        end
+
+    remainder_ms.positive? ? "#{ base }.#{ remainder_ms.to_s.rjust(3, '0') }" : base
+  end
 
   def snapshot_parent_post_ids = parents.order(:id).pluck(:id)
 
@@ -87,12 +137,7 @@ class Post < ApplicationRecord
   def resized_thumbnail!
     return unless thumbnail.attached?
 
-    image = MiniMagick::Image.read(thumbnail.download)
-    image.resize '180x180'
-    thumbnail.purge
-    thumbnail.attach(io:            File.open(image.path),
-                     filename:      'resized_thumbnail.jpg',
-                     content_type:  'image/jpeg')
+    thumbnail.attach(self.class.resized_thumbnail_attachment(StringIO.new(thumbnail.download)))
   end
 
   private

backend/app/models/post_tag.rb

@@ -10,6 +10,12 @@ class PostTag < ApplicationRecord
   belongs_to :created_user, class_name: 'User', optional: true
   belongs_to :deleted_user, class_name: 'User', optional: true
 
+  has_many :sections, -> { order(:begin_ms) }, class_name: 'PostTagSection',
+                                               foreign_key: [:post_id, :tag_id],
+                                               primary_key: [:post_id, :tag_id],
+                                               dependent: :delete_all,
+                                               inverse_of: :post_tag
+
   validates :post_id, presence: true
   validates :tag_id, presence: true
   validates :post_id, uniqueness: {

backend/app/models/post_tag_section.rb

@@ -0,0 +1,20 @@
+class PostTagSection < ApplicationRecord
+  self.primary_key = :post_id, :tag_id, :begin_ms
+
+  belongs_to :post
+  belongs_to :tag
+
+  belongs_to :post_tag, -> { kept }, foreign_key: [:post_id, :tag_id],
+                                     primary_key: [:post_id, :tag_id],
+                                     inverse_of: :sections,
+                                     optional: true
+
+  validates :post_id, presence: true
+  validates :tag_id, presence: true
+
+  validates :begin_ms, presence: true,
+                       numericality: { only_integer: true, greater_than_or_equal_to: 0 }
+
+  validates :end_ms, numericality: { only_integer: true, greater_than: :begin_ms },
+                     allow_nil: true
+end

backend/app/models/post_version.rb

@@ -5,6 +5,7 @@ class PostVersion < ApplicationRecord
   belongs_to :parent, class_name: 'Post', optional: true
 
   validates :url, presence: true
+  validates :video_ms, numericality: { only_integer: true, greater_than: 0 }, allow_nil: true
 
   validate :validate_original_created_range
 

backend/app/models/tag.rb

@@ -17,6 +17,16 @@ class Tag < ApplicationRecord
     end
   end
 
+  class SectionLiteralParseError < ArgumentError
+    attr_reader :tag_name, :literal
+
+    def initialize tag_name, literal
+      @tag_name = tag_name
+      @literal = literal
+      super("invalid section literal for tag #{ tag_name }: #{ literal }")
+    end
+  end
+
   has_many :post_tags, inverse_of: :tag
   has_many :active_post_tags, -> { kept }, class_name: 'PostTag', inverse_of: :tag
   has_many :post_tags_with_discarded, -> { with_discarded }, class_name: 'PostTag'
@@ -105,26 +115,60 @@ class Tag < ApplicationRecord
   def self.normalise_tags! tag_names, with_tagme: true,
                                       with_no_deerjikist: true,
                                       deny_nico: true,
-                                      deny_deprecated: false
+                                      deny_deprecated: false,
+                                      with_sections: false
     if deny_nico && tag_names.any? { |n| n.downcase.start_with?('nico:') }
       raise NicoTagNormalisationError
     end
 
+    sections = { }
     tags = tag_names.map do |name|
+      raw_name = name
       pf, cat = CATEGORY_PREFIXES.find { |p, _| name.downcase.start_with?(p) } || ['', nil]
-      name = TagName.canonicalise(name.sub(/\A#{ pf }/i, '')).first
+
+      name = name.sub(/\A#{ pf }/i, '')
+
+      sections_by_tag = []
+      while (match = name.match(/\A(\S*?)\[([^\[\]\s]*)-([^\[\]\s]*)\](\S*)\z/))
+        name = "#{ match[1] }#{ match[4] }"
+        next if match[2].empty? && match[3].empty?
+
+        sections_by_tag << normalise_section_range!(
+            begin_raw: match[2],
+            end_raw: match[3],
+            tag_name: name)
+      end
+
+      if name.include?('[') || name.include?(']')
+        raise SectionLiteralParseError.new(raw_name, raw_name)
+      end
+
+      name = TagName.canonicalise(name).first
+
       find_or_create_by_tag_name!(name, category: (cat || :general)).tap do |tag|
         if deny_deprecated && tag.deprecated?
           raise DeprecatedTagNormalisationError, [tag.name]
         end
 
         tag.update!(category: cat) if cat && tag.category != cat
+        next if sections_by_tag.empty?
+
+        sections[tag.id] ||= []
+        sections[tag.id].concat(sections_by_tag)
+        sections[tag.id] = merge_section_ranges(sections[tag.id])
+        sections.delete(tag.id) if sections[tag.id] == [[0, nil]]
       end
     end
 
     tags << Tag.tagme if with_tagme && tags.size < 10 && tags.none?(Tag.tagme)
     tags << Tag.no_deerjikist if with_no_deerjikist && tags.all? { |t| !(t.deerjikist?) }
-    tags.uniq(&:id)
+    tags.uniq!(&:id)
+
+    if with_sections
+      { tags:, sections: }
+    else
+      tags
+    end
   end
 
   def self.expand_parent_tags tags
@@ -150,6 +194,45 @@ class Tag < ApplicationRecord
     (result + tags).uniq { |t| t.id }
   end
 
+  def self.normalise_section_range! begin_raw:, end_raw:, tag_name:
+    begin_ms = begin_raw.empty? ? 0 : time_to_ms!(begin_raw, tag_name:)
+    end_ms = end_raw.empty? ? nil : time_to_ms!(end_raw, tag_name:)
+
+    if end_ms
+      begin_ms, end_ms = end_ms, begin_ms if begin_ms > end_ms
+      end_ms = begin_ms + 1 if begin_ms == end_ms
+    end
+
+    [begin_ms, end_ms]
+  end
+
+  def self.merge_section_ranges ranges
+    sorted_ranges = ranges.sort_by { |begin_ms, end_ms| [begin_ms, end_ms || Float::INFINITY] }
+    merged = []
+
+    sorted_ranges.each do |begin_ms, end_ms|
+      if merged.empty?
+        merged << [begin_ms, end_ms]
+        next
+      end
+
+      last_begin_ms, last_end_ms = merged[-1]
+      if last_end_ms.nil? || begin_ms <= last_end_ms
+        merged[-1] = [last_begin_ms, merge_section_end(last_end_ms, end_ms)]
+      else
+        merged << [begin_ms, end_ms]
+      end
+    end
+
+    merged
+  end
+
+  def self.merge_section_end left_end_ms, right_end_ms
+    return nil if left_end_ms.nil? || right_end_ms.nil?
+
+    [left_end_ms, right_end_ms].max
+  end
+
   def self.find_or_create_by_tag_name! name, category:
     tn = TagName.find_undiscard_or_create_by!(name: name.to_s.strip)
     tn = tn.canonical if tn.canonical_id?
@@ -246,6 +329,32 @@ class Tag < ApplicationRecord
     end
   end
 
+  def self.time_to_ms! str, tag_name:
+    match =
+        case str
+        when /\A(?<seconds>\d+)(?:\.(?<ms>\d{1,3}))?\z/
+          { hours: nil, minutes: nil, seconds: Regexp.last_match[:seconds],
+            ms: Regexp.last_match[:ms] }
+        when /\A(?<minutes>\d+):(?<seconds>[0-5]?\d)(?:\.(?<ms>\d{1,3}))?\z/
+          { hours: nil, minutes: Regexp.last_match[:minutes],
+            seconds: Regexp.last_match[:seconds],
+            ms: Regexp.last_match[:ms] }
+        when /\A(?<hours>\d+):(?<minutes>[0-5]?\d):(?<seconds>[0-5]?\d)(?:\.(?<ms>\d{1,3}))?\z/
+          { hours: Regexp.last_match[:hours],
+            minutes: Regexp.last_match[:minutes],
+            seconds: Regexp.last_match[:seconds],
+            ms: Regexp.last_match[:ms] }
+        end
+
+    raise SectionLiteralParseError.new(tag_name, str) unless match
+
+    total_s = match[:seconds].to_i
+    total_s += match[:minutes].to_i * 60 if match[:minutes]
+    total_s += match[:hours].to_i * 3_600 if match[:hours]
+
+    total_s * 1_000 + match[:ms].to_s.ljust(3, '0')[0, 3].to_i
+  end
+
   def nico_tags_cannot_be_deprecated
     if nico? && deprecated_at.present?
       errors.add :deprecated_at, 'ニコタグは廃止できません．'

backend/app/models/tag_implication.rb

@@ -6,6 +6,7 @@ class TagImplication < ApplicationRecord
   validates :parent_tag_id, presence: true
 
   validate :parent_tag_mustnt_be_itself
+  validate :parent_tag_mustnt_create_cycle
 
   private
 
@@ -14,4 +15,27 @@ class TagImplication < ApplicationRecord
       errors.add :parent_tag_id, '親タグは子タグと同一であってはなりません．'
     end
   end
+
+  def parent_tag_mustnt_create_cycle
+    return if tag_id.blank? || parent_tag_id.blank?
+    return if errors[:parent_tag_id].present?
+
+    seen = { }
+    stack = [parent_tag_id]
+
+    until stack.empty?
+      current_id = stack.pop
+      next if seen[current_id]
+
+      seen[current_id] = true
+
+      if current_id == tag_id
+        errors.add :parent_tag_id, '親タグに子孫タグを指定すると循環します．'
+        errors.add :base, 'タグの親子関係が循環します．'
+        return
+      end
+
+      stack.concat(TagImplication.where(tag_id: current_id).pluck(:parent_tag_id))
+    end
+  end
 end

backend/app/representations/material_repr.rb

@@ -2,8 +2,9 @@
 
 
 module MaterialRepr
-  BASE = { only: [:id, :url, :version_no, :file_suppressed_at,
-                  :file_suppression_reason, :created_at, :updated_at],
+  BASE = { only: [:id, :url, :version_no, :source_kind, :source_uri,
+                  :source_path, :source_file_id, :normalized_source_key,
+                  :created_at, :updated_at],
            methods: [:content_type],
            include: { tag: TagRepr::BASE,
                       created_by_user: UserRepr::BASE,
@@ -13,10 +14,15 @@ module MaterialRepr
 
   def base material, host:
     material.as_json(BASE).merge(
-        file: if material.file.attached? && !material.file_suppressed?
+        file: if material.file.attached?
                 Rails.application.routes.url_helpers.rails_storage_proxy_url(
                     material.file, host:)
               end,
+        thumbnail: thumbnail_url(material, host:),
+        thumbnail_fallback_text: thumbnail_fallback_text(material),
+        thumbnail_fallback_kind: thumbnail_fallback_kind(material),
+        media_kind: media_kind(material),
+        file_byte_size: material.file_byte_size,
         export_paths: export_paths(material),
         export_items: export_items(material))
   end
@@ -25,6 +31,32 @@ module MaterialRepr
     materials.map { |m| base(m, host:) }
   end
 
+  def list material, host:
+    { id: material.id,
+      version_no: material.version_no,
+      url: material.url,
+      source_kind: material.source_kind,
+      source_uri: material.source_uri,
+      source_path: material.source_path,
+      source_file_id: material.source_file_id,
+      normalized_source_key: material.normalized_source_key,
+      tag: compact_tag(material.tag),
+      thumbnail: thumbnail_url(material, host:),
+      thumbnail_fallback_text: thumbnail_fallback_text(material),
+      thumbnail_fallback_kind: thumbnail_fallback_kind(material),
+      media_kind: media_kind(material),
+      content_type: material.content_type,
+      file_byte_size: material.file_byte_size,
+      created_at: material.created_at,
+      updated_at: material.updated_at,
+      export_paths: export_paths(material),
+      export_items: export_items(material) }
+  end
+
+  def list_many materials, host:
+    materials.map { |m| list(m, host:) }
+  end
+
   def export_paths material
     material.material_export_items.each_with_object({ }) do |item, hash|
       hash[item.profile] = item.enabled ? item.export_path : ''
@@ -39,4 +71,39 @@ module MaterialRepr
         enabled: item.enabled }
     end
   end
+
+  def thumbnail_url material, host:
+    return nil unless material.thumbnail.attached?
+
+    Rails.application.routes.url_helpers.rails_storage_proxy_url(
+        material.thumbnail, host:)
+  end
+
+  def thumbnail_fallback_text material
+    material.tag&.name || material.created_at&.strftime('%Y-%m-%d')
+  end
+
+  def thumbnail_fallback_kind material
+    material.tag.present? ? 'tag_name' : 'created_at'
+  end
+
+  def media_kind material
+    return 'url_only' unless material.file.attached?
+
+    content_type = material.file.blob.content_type.to_s
+    return 'image' if content_type.start_with?('image/')
+    return 'video' if content_type.start_with?('video/')
+    return 'audio' if content_type.start_with?('audio/')
+
+    'file_other'
+  end
+
+  def compact_tag tag
+    return nil unless tag
+
+    { id: tag.id,
+      name: tag.name,
+      category: tag.category,
+      deprecated_at: tag.deprecated_at }
+  end
 end

backend/app/representations/post_repr.rb

@@ -8,6 +8,7 @@ module PostRepr
       :url,
       :title,
       :thumbnail_base,
+      :video_ms,
       :original_created_from,
       :original_created_before,
       :created_at,
@@ -18,7 +19,7 @@ module PostRepr
 
   def base post, current_user = nil
     json = common(post)
-    json['tags'] = tag_json(post.tags)
+    json['tags'] = tag_json(post)
     json['uploaded_user'] = post.uploaded_user && UserRepr.base(post.uploaded_user)
     json['viewed'] = current_user ? current_user.viewed?(post) : false
     json
@@ -52,8 +53,16 @@ module PostRepr
                .merge('thumbnail' => thumbnail_url(post))
   end
 
-  def tag_json tags
-    tags.reject(&:deprecated?).map { |tag| TagRepr.inline(tag) }
+  def tag_json post
+    post
+        .active_post_tags
+        .reject { _1.tag.deprecated? }
+        .sort_by { _1.tag.name }
+        .map { |post_tag|
+      TagRepr.inline(post_tag.tag).merge(
+          'children' => [],
+          'sections' => post_tag.sections.as_json(only: [:begin_ms, :end_ms]))
+    }
   end
 
   def thumbnail_url post

backend/app/services/google_drive/api_client.rb

@@ -0,0 +1,233 @@
+require 'json'
+require 'jwt'
+require 'net/http'
+require 'openssl'
+require 'tempfile'
+require 'uri'
+
+
+module GoogleDrive
+  class ApiClient
+    DRIVE_ENDPOINT = 'https://www.googleapis.com/drive/v3'
+    TOKEN_ENDPOINT = 'https://oauth2.googleapis.com/token'
+    FOLDER_MIME_TYPE = 'application/vnd.google-apps.folder'
+    NATIVE_FILE_MIME_TYPE_PREFIX = 'application/vnd.google-apps.'
+    DRIVE_SCOPE = 'https://www.googleapis.com/auth/drive.readonly'
+
+    def initialize service_account_email: ENV['GOOGLE_DRIVE_SERVICE_ACCOUNT_EMAIL'],
+                   private_key: ENV['GOOGLE_DRIVE_PRIVATE_KEY'],
+                   private_key_path: ENV['GOOGLE_DRIVE_PRIVATE_KEY_PATH'],
+                   subject: ENV['GOOGLE_DRIVE_SUBJECT']
+      @service_account_email = service_account_email.to_s
+      @private_key = load_private_key(private_key, private_key_path)
+      @subject = subject.to_s.presence
+      @access_token = nil
+    end
+
+    def list_material_files_under_folder folder_id
+      files = []
+      each_material_file_under_folder(folder_id) { |entry| files << entry }
+      files
+    end
+
+    def each_material_file_under_folder folder_id
+      return enum_for(__method__, folder_id) unless block_given?
+
+      walk_folder(folder_id, nil) do |entry, relative_path|
+        next if entry['mimeType'] == FOLDER_MIME_TYPE
+        next if native_file?(entry['mimeType'])
+
+        yield build_file_entry(entry, relative_path)
+      end
+    end
+
+    def fetch_material_file file_id
+      metadata = get_file(file_id)
+      return nil if native_file?(metadata['mimeType'])
+
+      build_file_entry(metadata, metadata['name'])
+    end
+
+    def download_to_tempfile file_id, filename:
+      tempfile = Tempfile.new(['material-sync', File.extname(filename.to_s)])
+      tempfile.binmode
+      request_binary("/files/#{ file_id }",
+                     { alt: 'media', supportsAllDrives: true }) do |chunk|
+        tempfile.write(chunk.b)
+      end
+      tempfile.rewind
+      tempfile
+    rescue StandardError
+      tempfile&.close!
+      raise
+    end
+
+    def extract_file_id value
+      raw = value.to_s.strip
+      return nil if raw.blank?
+      return raw unless raw.include?('/')
+
+      uri = URI.parse(raw)
+      return uri.query.to_s[%r{(?:^|&)id=([^&]+)}, 1] if uri.query.present?
+      return uri.path[%r{/folders/([^/]+)}, 1] if uri.path.include?('/folders/')
+
+      uri.path[%r{/d/([^/]+)}, 1]
+    rescue URI::InvalidURIError
+      nil
+    end
+
+    private
+
+    def walk_folder folder_id, prefix, &block
+      list_children(folder_id).each do |entry|
+        relative_path = MaterialSyncExportPath.build(prefix:,
+                                                     relative_path: entry['name'])
+        if entry['mimeType'] == FOLDER_MIME_TYPE
+          walk_folder(entry['id'], relative_path, &block)
+          next
+        end
+
+        block.call(entry, relative_path)
+      end
+    end
+
+    def build_file_entry entry, relative_path
+      { id: entry['id'],
+        name: entry['name'],
+        mime_type: entry['mimeType'],
+        relative_path: MaterialSyncExportPath.normalize_path(relative_path),
+        sha256_checksum: entry['sha256Checksum'],
+        web_view_link: entry['webViewLink'],
+        web_content_link: entry['webContentLink'] }
+    end
+
+    def list_children folder_id
+      files = []
+      page_token = nil
+
+      loop do
+        response =
+            request_json('/files', {
+                q: "'#{ folder_id }' in parents and trashed = false",
+                fields: 'nextPageToken,files(id,name,mimeType,sha256Checksum,' \
+                        'webViewLink,webContentLink)',
+                orderBy: 'folder,name',
+                pageSize: 1000,
+                supportsAllDrives: true,
+                includeItemsFromAllDrives: true,
+                pageToken: page_token }.compact)
+        files.concat(response.fetch('files'))
+        page_token = response['nextPageToken']
+        break if page_token.blank?
+      end
+
+      files
+    end
+
+    def get_file file_id
+      request_json("/files/#{ file_id }",
+                   fields: 'id,name,mimeType,sha256Checksum,webViewLink,webContentLink',
+                   supportsAllDrives: true)
+    end
+
+    def request_json path, params = {}
+      response = request(:get, path, params:)
+      unless response.is_a?(Net::HTTPSuccess)
+        raise "Google Drive API error: #{ response.code } #{ response.body }"
+      end
+
+      JSON.parse(response.body)
+    end
+
+    def request_binary path, params = {}
+      request(:get, path, params:) do |response|
+        unless response.is_a?(Net::HTTPSuccess)
+          raise "Google Drive download error: #{ response.code } #{ response.body }"
+        end
+
+        response.read_body do |chunk|
+          yield chunk.b
+        end
+      end
+    end
+
+    def request method, path, params: nil
+      uri = URI(DRIVE_ENDPOINT + path)
+      uri.query = URI.encode_www_form(params) if params.present?
+
+      klass =
+          case method
+          when :get
+            Net::HTTP::Get
+          else
+            raise ArgumentError, "Unsupported Google Drive request method: #{ method }"
+          end
+      request = klass.new(uri)
+      request['Authorization'] = "Bearer #{ access_token }"
+
+      Net::HTTP.start(uri.host,
+                      uri.port,
+                      use_ssl: true,
+                      open_timeout: 10,
+                      read_timeout: 60) do |http|
+        if block_given?
+          http.request(request) do |response|
+            return yield response
+          end
+        else
+          http.request(request)
+        end
+      end
+    end
+
+    def access_token
+      @access_token ||= fetch_access_token
+    end
+
+    def fetch_access_token
+      raise 'GOOGLE_DRIVE_SERVICE_ACCOUNT_EMAIL is required' if @service_account_email.blank?
+      raise 'Google Drive private key is required' if @private_key.blank?
+
+      payload = { iss: @service_account_email,
+                  scope: DRIVE_SCOPE,
+                  aud: TOKEN_ENDPOINT,
+                  exp: 1.hour.from_now.to_i,
+                  iat: Time.current.to_i }
+      payload[:sub] = @subject if @subject.present?
+
+      assertion = JWT.encode(payload, @private_key, 'RS256')
+      uri = URI(TOKEN_ENDPOINT)
+      request = Net::HTTP::Post.new(uri)
+      request.set_form_data(
+          grant_type: 'urn:ietf:params:oauth:grant-type:jwt-bearer',
+          assertion:)
+
+      response =
+          Net::HTTP.start(uri.host,
+                          uri.port,
+                          use_ssl: true,
+                          open_timeout: 10,
+                          read_timeout: 30) do |http|
+            http.request(request)
+          end
+      unless response.is_a?(Net::HTTPSuccess)
+        raise "Google OAuth error: #{ response.code } #{ response.body }"
+      end
+
+      JSON.parse(response.body).fetch('access_token')
+    end
+
+    def load_private_key private_key, private_key_path
+      raw = private_key.to_s
+      raw = raw.gsub('\n', "\n") if raw.present?
+      raw = File.read(private_key_path) if raw.blank? && private_key_path.present?
+      return nil if raw.blank?
+
+      OpenSSL::PKey::RSA.new(raw)
+    end
+
+    def native_file? mime_type
+      mime_type.to_s.start_with?(NATIVE_FILE_MIME_TYPE_PREFIX)
+    end
+  end
+end

backend/app/services/material_file_sha256.rb

@@ -1,16 +1,39 @@
 require 'digest'
+require 'json'
 
 class MaterialFileSha256
+  def self.blob_metadata blob
+    metadata = blob.metadata
+    return metadata if metadata.is_a?(Hash)
+    return { } if metadata.blank?
+
+    JSON.parse(metadata)
+  rescue JSON::ParserError
+    { }
+  end
+
+  def self.metadata_sha256 blob
+    blob_metadata(blob)['sha256'].presence
+  end
+
+  def self.assign_metadata_sha256! blob, sha256
+    return if sha256.blank?
+
+    metadata = blob_metadata(blob)
+    metadata['sha256'] = sha256
+    blob.metadata = metadata
+    blob.save! if blob.changed?
+  end
+
   def self.from_blob blob, allow_download: false
-    sha256 = blob.metadata['sha256']
+    sha256 = metadata_sha256(blob)
     return sha256 if sha256.present?
     return nil unless allow_download
 
     begin
       blob.open do |file|
         sha256 = Digest::SHA256.file(file.path).hexdigest
-        blob.metadata['sha256'] = sha256
-        blob.save! if blob.changed?
+        assign_metadata_sha256!(blob, sha256)
         sha256
       end
     rescue ActiveStorage::FileNotFoundError, ArgumentError => error

backend/app/services/material_sync_export_path.rb

@@ -0,0 +1,56 @@
+class MaterialSyncExportPath
+  class << self
+    def build prefix: nil, relative_path: nil, filename: nil, source_file_id: nil
+      path = normalize_path(relative_path)
+      path = fallback_filename(filename, source_file_id) if path.blank?
+
+      normalized_prefix = normalize_path(prefix)
+      return path if normalized_prefix.blank?
+      return normalized_prefix if path.blank?
+
+      [normalized_prefix, path].join('/')
+    end
+
+    def normalize_path path
+      raw = path.to_s.delete("\0").tr('\\', '/').strip
+      raw = raw.sub(%r{\A[A-Za-z]:/+}, '')
+      raw = raw.sub(%r{\A/+}, '')
+      return nil if raw.blank?
+
+      segments = raw.split('/').filter_map do |segment|
+        normalized = normalize_segment(segment)
+        normalized.presence
+      end
+      return nil if segments.empty?
+
+      segments.join('/')
+    end
+
+    def uniquify path, source_file_id
+      normalized = normalize_path(path)
+      return normalized if normalized.blank? || source_file_id.blank?
+
+      ext = File.extname(normalized)
+      base = ext.present? ? normalized.delete_suffix(ext) : normalized
+      "#{ base }--#{ source_file_id }#{ ext }"
+    end
+
+    private
+
+    def fallback_filename filename, source_file_id
+      name = normalize_path(filename)
+      return name if name.present?
+      return nil if source_file_id.blank?
+
+      source_file_id.to_s
+    end
+
+    def normalize_segment segment
+      cleaned = segment.to_s.delete("\0").tr('\\/', '_').strip
+      return nil if cleaned.blank? || cleaned == '.'
+      return '__' if cleaned == '..'
+
+      cleaned
+    end
+  end
+end

backend/app/services/material_sync_importer.rb

@@ -0,0 +1,259 @@
+require 'digest'
+
+class MaterialSyncImporter
+  Result = Struct.new(:material, :action, :suppressed, :suppression, keyword_init: true)
+
+  def self.import! attributes
+    new(attributes).import!
+  end
+
+  def initialize attributes
+    @attributes = attributes
+  end
+
+  def import!
+    source = source_attributes
+    key = normalized_source_key(source)
+    raise ArgumentError, 'normalized_source_key is required for material sync' if key.blank?
+
+    suppression = suppression_for(source)
+    if suppression
+      return Result.new(material: nil,
+                        action: :suppressed,
+                        suppressed: true,
+                        suppression:)
+    end
+
+    material =
+        Material
+        .unscoped
+        .find_or_initialize_by(normalized_source_key: key)
+    if unchanged?(material, source)
+      return Result.new(material:,
+                        action: :unchanged,
+                        suppressed: false,
+                        suppression: nil)
+    end
+
+    event_type =
+        if material.new_record?
+          :create
+        elsif material.discarded?
+          :restore
+        else
+          :update
+        end
+    uploaded_blob = uploaded_blob!
+    if @import_block
+      return Result.new(material: nil,
+                        action: :suppressed,
+                        suppressed: true,
+                        suppression: @import_block)
+    end
+
+    Material.transaction do
+      if material.persisted?
+        MaterialVersionRecorder.ensure_snapshot!(material,
+                                                 created_by_user: @attributes[:updated_by_user])
+      end
+      material.assign_attributes(material_attributes_for(material).merge(source))
+      material.discarded_at = nil if material.respond_to?(:discarded_at=)
+      material.file.attach(uploaded_blob) if uploaded_blob
+      material.save!
+      upsert_export_item!(material)
+      MaterialVersionRecorder.record!(material:,
+                                      event_type:,
+                                      created_by_user: @attributes[:updated_by_user])
+    end
+    MaterialThumbnailGenerator.generate!(material)
+
+    Result.new(material:,
+               action: event_type == :create ? :imported : :updated,
+               suppressed: false,
+               suppression: nil)
+  rescue StandardError
+    uploaded_blob&.purge_later
+    raise
+  ensure
+    close_tempfile!
+  end
+
+  private
+
+  def source_attributes
+    { source_kind: @attributes[:source_kind],
+      source_uri: @attributes[:source_uri],
+      source_path: @attributes[:source_path],
+      source_file_id: @attributes[:source_file_id] }
+  end
+
+  def normalized_source_key source
+    MaterialSyncSuppression.normalize_source_key(source_kind: source[:source_kind],
+                                                 source_uri: source[:source_uri],
+                                                 source_path: source[:source_path],
+                                                 source_file_id: source[:source_file_id])
+  end
+
+  def material_attributes_for material
+    attrs =
+        @attributes
+        .except(:source_kind, :source_uri, :source_path, :source_file_id,
+                :file_blob, :file_tempfile, :file_downloader,
+                :filename, :content_type,
+                :file_sha256, :export_path, :profile, :tag, :url)
+
+    if material.new_record?
+      attrs[:tag] = @attributes[:tag] if @attributes.key?(:tag)
+      attrs[:url] = @attributes[:url] if @attributes.key?(:url)
+      return attrs
+    end
+
+    if @attributes.key?(:tag) && @attributes[:tag].present?
+      attrs[:tag] = @attributes[:tag]
+    end
+    if @attributes.key?(:url) && @attributes[:url].present?
+      attrs[:url] = @attributes[:url]
+    end
+
+    attrs
+  end
+
+  def suppression_for source
+    if source[:source_kind] == 'google_drive_file' && source[:source_path].present?
+      return MaterialSyncSuppressionMatcher.match_google_drive_candidate(
+          drive_file_id: source[:source_file_id],
+          relative_path: source[:source_path])
+    end
+
+    MaterialSyncSuppressionMatcher.match(**source)
+  end
+
+  def uploaded_blob!
+    return @attributes[:file_blob] if @attributes[:file_blob]
+
+    tempfile = upload_tempfile
+    return nil unless tempfile
+
+    tempfile.rewind
+    file_sha256 = @attributes[:file_sha256] || Digest::SHA256.file(tempfile.path).hexdigest
+    @attributes[:file_sha256] = file_sha256
+
+    @import_block = MaterialImportBlockMatcher.match_for_sha256(file_sha256)
+    if @import_block
+      tempfile.rewind
+      return nil
+    end
+
+    blob = ActiveStorage::Blob.create_and_upload!(
+        io: tempfile,
+        filename: @attributes[:filename],
+        content_type: @attributes[:content_type])
+    MaterialFileSha256.assign_metadata_sha256!(blob, file_sha256)
+    tempfile.rewind
+    blob
+  end
+
+  def upload_tempfile
+    return @upload_tempfile if defined?(@upload_tempfile)
+
+    @upload_tempfile = @attributes[:file_tempfile]
+    if @upload_tempfile.blank? && @attributes[:file_downloader]
+      @upload_tempfile = @attributes[:file_downloader].call
+    end
+    @upload_tempfile
+  end
+
+  def upsert_export_item! material
+    export_path = resolved_export_path(material)
+    return if export_path.blank?
+
+    item = material.material_export_items.find_or_initialize_by(profile: effective_profile)
+    item.export_path = export_path
+    item.enabled = true
+    item.created_by_user ||= @attributes[:created_by_user]
+    item.save!
+  end
+
+  def export_path_taken_by_other? material, profile, export_path
+    MaterialExportItem
+      .where(profile:, export_path:)
+      .where.not(material_id: material.id)
+      .exists?
+  end
+
+  def close_tempfile!
+    tempfile = upload_tempfile
+    return unless tempfile
+
+    tempfile.close! unless tempfile.closed?
+  rescue StandardError
+    nil
+  end
+
+  def unchanged? material, source
+    return false if material.new_record? || material.discarded?
+    return false unless same_source_attributes?(material, source)
+    return false unless same_export_path?(material)
+    return false unless same_material_attributes?(material)
+
+    same_file_snapshot?(material)
+  end
+
+  def same_source_attributes? material, source
+    material.source_kind == source[:source_kind] \
+      && material.source_uri == source[:source_uri] \
+      && material.source_path == source[:source_path] \
+      && material.source_file_id == source[:source_file_id]
+  end
+
+  def same_export_path? material
+    expected = resolved_export_path(material)
+    current = material.material_export_items.find { |item| item.profile == effective_profile }
+
+    return current.blank? if expected.blank?
+
+    current&.enabled && current.export_path == expected
+  end
+
+  def same_material_attributes? material
+    same_tag_attribute?(material) && same_url_attribute?(material)
+  end
+
+  def same_file_snapshot? material
+    expected_sha256 = @attributes[:file_sha256].to_s.presence
+
+    if expected_sha256.present?
+      return false unless material.file.attached?
+
+      return MaterialFileSha256.metadata_sha256(material.file.blob) == expected_sha256
+    end
+
+    !material.file.attached?
+  end
+
+  def effective_profile
+    @attributes[:profile].presence || 'legacy_drive'
+  end
+
+  def resolved_export_path material
+    export_path = @attributes[:export_path].to_s.strip
+    return export_path if export_path.blank?
+    return export_path unless export_path_taken_by_other?(material, effective_profile, export_path)
+
+    MaterialSyncExportPath.uniquify(export_path, @attributes[:source_file_id])
+  end
+
+  def same_tag_attribute? material
+    return true unless @attributes.key?(:tag)
+    return true if @attributes[:tag].blank?
+
+    material.tag_id == @attributes[:tag].id
+  end
+
+  def same_url_attribute? material
+    return true unless @attributes.key?(:url)
+    return true if @attributes[:url].blank?
+
+    material.url == @attributes[:url]
+  end
+end

backend/app/services/material_sync_runner.rb

@@ -0,0 +1,251 @@
+class MaterialSyncRunner
+  Result = Struct.new(:imported, :updated, :unchanged, :suppressed, :failed,
+                      :errors, keyword_init: true)
+
+  def self.sync_enabled!
+    results = MaterialSyncSource.enabled.order(:id).map { |source| new(source).sync! }
+
+    Result.new(imported: results.sum(&:imported),
+               updated: results.sum(&:updated),
+               unchanged: results.sum(&:unchanged),
+               suppressed: results.sum(&:suppressed),
+               failed: results.sum(&:failed),
+               errors: results.flat_map(&:errors))
+  end
+
+  def initialize source
+    @source = source
+  end
+
+  def sync!
+    result = Result.new(imported: 0, updated: 0, unchanged: 0,
+                        suppressed: 0, failed: 0, errors: [])
+
+    if @source.source_kind == 'google_drive_path'
+      sync_google_drive_path!(result)
+    else
+      candidates.each do |candidate|
+        next if candidate.blank?
+
+        sync_candidate!(candidate, result)
+      end
+    end
+
+    @source.update!(last_synced_at: Time.current)
+    log_result(result)
+    result
+  rescue NotImplementedError, StandardError => e
+    result.failed += 1
+    result.errors << { source_id: @source.id, error: e.message }
+    log_result(result)
+    result
+  end
+
+  private
+
+  def candidates
+    case @source.source_kind
+    when 'uri'
+      [uri_candidate]
+    when 'google_drive_file'
+      [google_drive_file_candidate]
+    when 'legacy_drive_path'
+      raise NotImplementedError, 'legacy_drive_path material sync is not implemented'
+    else
+      raise NotImplementedError, "Unsupported material sync source_kind: #{ @source.source_kind }"
+    end
+  end
+
+  def uri_candidate
+    { source_kind: @source.source_kind,
+      source_uri: @source.source_uri,
+      source_path: @source.source_path,
+      source_file_id: @source.source_file_id,
+      url: @source.source_uri,
+      tag: nil,
+      created_by_user: @source.created_by_user,
+      updated_by_user: @source.updated_by_user || @source.created_by_user }
+  end
+
+  def sync_candidate! candidate, result
+    block = MaterialImportBlockMatcher.match_for_sha256(candidate[:file_sha256])
+    if block
+      result.suppressed += 1
+      Rails.logger.info(
+          material_sync_log(action: 'suppressed',
+                            reason: block.reason,
+                            normalized_source_key: candidate_normalized_source_key(candidate)))
+      return
+    end
+
+    suppression = suppression_for(candidate)
+
+    if suppression
+      result.suppressed += 1
+      Rails.logger.info(
+          material_sync_log(action: 'suppressed',
+                            normalized_source_key: suppression.normalized_source_key))
+      return
+    end
+
+    import = MaterialSyncImporter.import!(candidate)
+    result.public_send("#{ import.action }=", result.public_send(import.action) + 1)
+  rescue StandardError => e
+    result.failed += 1
+    result.errors << { source_id: @source.id,
+                       normalized_source_key: candidate_normalized_source_key(candidate),
+                       error: e.message }
+    Rails.logger.warn(
+        material_sync_log(action: 'failed',
+                          error: e.message,
+                          normalized_source_key: candidate_normalized_source_key(candidate)))
+  ensure
+    close_candidate_tempfile(candidate)
+  end
+
+  def google_drive_path_candidates
+    folder_id = google_drive_folder_id
+    Enumerator.new do |entries|
+      drive_client.each_material_file_under_folder(folder_id).each do |entry|
+        entries << build_google_drive_candidate(entry)
+      end
+    end
+  end
+
+  def sync_google_drive_path! result
+    folder_id = google_drive_folder_id
+    scanned_count = 0
+
+    drive_client.each_material_file_under_folder(folder_id) do |entry|
+      scanned_count += 1
+      sync_candidate!(build_google_drive_candidate(entry), result)
+      log_google_drive_progress(folder_id, scanned_count, result) if progress_log_scan_count?(scanned_count)
+    end
+
+    log_google_drive_progress(folder_id, scanned_count, result, summary: true)
+  end
+
+  def google_drive_file_candidate
+    entry = drive_client.fetch_material_file(google_drive_file_id)
+    return nil unless entry
+
+    build_google_drive_candidate(entry, single_file: true)
+  end
+
+  def build_google_drive_candidate entry, single_file: false
+    relative_path =
+        if single_file
+          nil
+        else
+          entry[:relative_path]
+        end
+    export_path =
+        MaterialSyncExportPath.build(prefix: @source.export_path_prefix,
+                                     relative_path:,
+                                     filename: entry[:name],
+                                     source_file_id: entry[:id])
+
+    { source_kind: 'google_drive_file',
+      source_uri: entry[:web_view_link] || google_drive_file_url(entry[:id]),
+      source_path: relative_path.presence || MaterialSyncExportPath.normalize_path(entry[:name]),
+      source_file_id: entry[:id],
+      filename: entry[:name],
+      content_type: entry[:mime_type],
+      file_downloader: lambda {
+        drive_client.download_to_tempfile(entry[:id], filename: entry[:name])
+      },
+      file_sha256: entry[:sha256_checksum],
+      export_path:,
+      profile: @source.profile,
+      tag: nil,
+      url: nil,
+      created_by_user: @source.created_by_user,
+      updated_by_user: @source.updated_by_user || @source.created_by_user }
+  end
+
+  def candidate_normalized_source_key candidate
+    MaterialSyncSuppression.normalize_source_key(source_kind: candidate[:source_kind],
+                                                 source_uri: candidate[:source_uri],
+                                                 source_path: candidate[:source_path],
+                                                 source_file_id: candidate[:source_file_id])
+  end
+
+  def suppression_for candidate
+    if candidate[:source_kind] == 'google_drive_file' && candidate[:source_path].present?
+      return MaterialSyncSuppressionMatcher.match_google_drive_candidate(
+          drive_file_id: candidate[:source_file_id],
+          relative_path: candidate[:source_path])
+    end
+
+    MaterialSyncSuppressionMatcher.match(source_kind: candidate[:source_kind],
+                                         source_uri: candidate[:source_uri],
+                                         source_path: candidate[:source_path],
+                                         source_file_id: candidate[:source_file_id])
+  end
+
+  def drive_client
+    @drive_client ||= GoogleDrive::ApiClient.new
+  end
+
+  def google_drive_folder_id
+    google_drive_target_id.tap do |id|
+      if id.blank?
+        raise ArgumentError, 'google_drive_path source_file_id or source_uri is required'
+      end
+    end
+  end
+
+  def google_drive_file_id
+    google_drive_target_id.tap do |id|
+      if id.blank?
+        raise ArgumentError, 'google_drive_file source_file_id or source_uri is required'
+      end
+    end
+  end
+
+  def google_drive_target_id
+    @source.source_file_id.presence || drive_client.extract_file_id(@source.source_uri)
+  end
+
+  def google_drive_file_url file_id
+    "https://drive.google.com/file/d/#{ file_id }/view"
+  end
+
+  def close_candidate_tempfile candidate
+    tempfile = candidate[:file_tempfile]
+    return unless tempfile
+
+    tempfile.close! unless tempfile.closed?
+  rescue StandardError
+    nil
+  end
+
+  def log_result result
+    Rails.logger.info(material_sync_log(imported: result.imported,
+                                        updated: result.updated,
+                                        unchanged: result.unchanged,
+                                        suppressed: result.suppressed,
+                                        failed: result.failed))
+  end
+
+  def progress_log_scan_count? scanned_count
+    scanned_count == 1 || (scanned_count % 50).zero?
+  end
+
+  def log_google_drive_progress folder_id, scanned_count, result, summary: false
+    Rails.logger.info(
+        material_sync_log(folder_id:,
+                          scanned_count:,
+                          imported: result.imported,
+                          updated: result.updated,
+                          unchanged: result.unchanged,
+                          suppressed: result.suppressed,
+                          failed: result.failed,
+                          progress: summary ? 'summary' : 'scan'))
+  end
+
+  def material_sync_log fields
+    { material_sync_source_id: @source.id,
+      material_sync_source_name: @source.name }.merge(fields).to_json
+  end
+end

backend/app/services/material_sync_suppression_matcher.rb

@@ -0,0 +1,68 @@
+class MaterialSyncSuppressionMatcher
+  def self.match source_kind:,
+                 source_uri: nil,
+                 drive_path: nil,
+                 drive_file_id: nil,
+                 source_path: nil,
+                 source_file_id: nil
+    key = MaterialSyncSuppression.normalize_source_key(source_kind:,
+                                                       source_uri:,
+                                                       drive_path:,
+                                                       drive_file_id:,
+                                                       source_path:,
+                                                       source_file_id:)
+    return nil if key.blank?
+
+    MaterialSyncSuppression.find_by(normalized_source_key: key)
+  end
+
+  def self.match_google_drive_candidate drive_file_id:, relative_path:
+    normalized_path = validate_relative_path!(relative_path)
+
+    exact = [
+      normalize_key('google_drive_file', drive_file_id),
+      normalize_key('google_drive_path', normalized_path),
+      normalize_key('legacy_drive_path', normalized_path),
+    ].compact
+
+    suppression =
+        MaterialSyncSuppression.find_by(normalized_source_key: exact)
+    return suppression if suppression
+
+    MaterialSyncSuppression
+      .where(source_kind: ['google_drive_path_prefix', 'legacy_drive_path_prefix'])
+      .where('drive_path = :path OR :path LIKE CONCAT(drive_path, "/%")', path: normalized_path)
+      .order(:id)
+      .first
+  end
+
+  def self.suppressed?(...)
+    match(...).present?
+  end
+
+  def self.validate_relative_path! relative_path
+    raw = relative_path.to_s.delete("\0").tr('\\', '/').strip
+    raise ArgumentError, 'relative_path is required' if raw.blank?
+    raise ArgumentError, 'relative_path must be relative' if raw.start_with?('/')
+    raise ArgumentError, 'relative_path must be relative' if raw.match?(/\A[A-Za-z]:\//)
+    if raw.start_with?('My Drive/', 'マイドライブ/')
+      raise ArgumentError, 'relative_path must be relative to source folder'
+    end
+    raise ArgumentError, 'relative_path must not contain //' if raw.include?('//')
+    raise ArgumentError, 'relative_path must not end with /' if raw.end_with?('/')
+
+    parts = raw.split('/')
+    if parts.any? { |part| part.in?(['.', '..']) }
+      raise ArgumentError, 'relative_path must not contain dot segments'
+    end
+
+    raw
+  end
+
+  def self.normalize_key source_kind, value
+    return nil if value.blank?
+
+    MaterialSyncSuppression.normalize_source_key(source_kind:, source_path: value,
+                                                 source_file_id: value)
+  end
+end

backend/app/services/material_sync_suppression_registrar.rb

@@ -0,0 +1,51 @@
+class MaterialSyncSuppressionRegistrar
+  def self.create! attributes, created_by_user:
+    new(attributes, created_by_user:).create!
+  end
+
+  def initialize attributes, created_by_user:
+    @attributes = attributes
+    @created_by_user = created_by_user
+  end
+
+  def create!
+    suppression = nil
+
+    MaterialSyncSuppression.transaction do
+      suppression = MaterialSyncSuppression.create!(
+          @attributes.merge(created_by_user: @created_by_user))
+      discard_existing_materials!(suppression)
+    end
+
+    suppression
+  end
+
+  private
+
+  def discard_existing_materials! suppression
+    matching_materials(suppression).find_each do |material|
+      MaterialVersionRecorder.ensure_snapshot!(material, created_by_user: @created_by_user)
+      material.discard!
+      MaterialVersionRecorder.record!(material:,
+                                      event_type: :discard,
+                                      created_by_user: @created_by_user)
+    end
+  end
+
+  def matching_materials suppression
+    materials = Material.unscoped.kept
+
+    case suppression.source_kind
+    when 'google_drive_path', 'legacy_drive_path'
+      materials.where(source_path: suppression.drive_path)
+    when 'google_drive_path_prefix', 'legacy_drive_path_prefix'
+      path = suppression.drive_path.to_s
+      materials.where(
+          'source_path = :path OR source_path LIKE :prefix',
+          path:,
+          prefix: "#{ path }/%")
+    else
+      materials.where(normalized_source_key: suppression.normalized_source_key)
+    end
+  end
+end

backend/app/services/material_thumbnail_generator.rb

@@ -0,0 +1,126 @@
+# frozen_string_literal: true
+
+require 'mini_magick'
+require 'open3'
+require 'tempfile'
+
+
+class MaterialThumbnailGenerator
+  SIZE = '180x180'
+
+  class << self
+    def generate! material
+      new(material).generate!
+    end
+  end
+
+  def initialize material
+    @material = material
+    @ffmpeg_stderr = []
+  end
+
+  def generate!
+    return log_result(:no_file) unless @material.file.attached?
+    return log_result(:unsupported_content_type) unless image? || video?
+
+    @material.file.blob.open do |file|
+      thumbnail = image? ? image_thumbnail(file.path) : video_thumbnail(file.path)
+      return log_result(:generation_failed) unless thumbnail
+
+      return attach_thumbnail(thumbnail)
+    end
+  rescue ActiveStorage::FileNotFoundError => e
+    log_result(:file_not_found, error: e)
+  rescue MiniMagick::Error => e
+    log_result(:mini_magick_error, error: e)
+  rescue ArgumentError, StandardError => e
+    log_result(:generation_failed, error: e)
+  end
+
+  private
+
+  def image? = content_type.start_with?('image/')
+
+  def video? = content_type.start_with?('video/')
+
+  def content_type
+    return nil unless @material.file.attached?
+
+    @material.file.blob.content_type.to_s
+  end
+
+  def image_thumbnail path
+    image = MiniMagick::Image.open(path)
+    image.resize(SIZE)
+    image.format('jpg')
+    image
+  end
+
+  def video_thumbnail path
+    [1, 0].each do |seconds|
+      tempfile = Tempfile.new(['material-thumbnail', '.jpg'])
+      tempfile.close
+      ok = extract_video_frame(path, tempfile.path, seconds)
+      next unless ok && File.size?(tempfile.path)
+
+      return image_thumbnail(tempfile.path)
+    ensure
+      tempfile&.unlink
+    end
+
+    nil
+  end
+
+  def extract_video_frame input_path, output_path, seconds
+    _stdout, stderr, status =
+        Open3.capture3('ffmpeg',
+                       '-y',
+                       '-ss', seconds.to_s,
+                       '-i', input_path,
+                       '-frames:v', '1',
+                       '-f', 'image2',
+                       output_path)
+    @ffmpeg_stderr << stderr if stderr.present?
+    status.success?
+  rescue Errno::ENOENT => e
+    @ffmpeg_stderr << "ffmpeg unavailable: #{ e.message }"
+    false
+  end
+
+  def attach_thumbnail image
+    blob = nil
+    File.open(image.path) do |io|
+      blob = ActiveStorage::Blob.create_and_upload!(
+          io:,
+          filename: 'material-thumbnail.jpg',
+          content_type: 'image/jpeg')
+    end
+    @material.thumbnail.attach(blob)
+    log_result(:attached)
+  rescue StandardError => e
+    blob&.purge_later
+    log_result(:attach_failed, error: e)
+  end
+
+  def log_result result, error: nil
+    log_payload = { material_id: @material.id,
+                    file_blob_id: file_blob_id,
+                    content_type:,
+                    result:,
+                    error_class: error&.class&.name,
+                    error_message: error&.message,
+                    ffmpeg_stderr: @ffmpeg_stderr.join("\n").presence }
+    if [:attached, :no_file, :unsupported_content_type].include?(result)
+      Rails.logger.info("Material thumbnail generation: #{ log_payload.to_json }")
+    else
+      Rails.logger.warn("Material thumbnail generation: #{ log_payload.to_json }")
+    end
+    result
+  end
+
+  def file_blob_id
+    return nil unless @material.file.attached?
+
+    @material.file.blob.id
+  end
+end

backend/app/services/material_version_recorder.rb

@@ -1,5 +1,5 @@
 class MaterialVersionRecorder < VersionRecorder
-  EVENT_TYPES = ['create', 'update', 'discard', 'restore', 'suppress'].freeze
+  EVENT_TYPES = ['create', 'update', 'discard', 'restore'].freeze
 
   def self.record! material:, event_type:, created_by_user:, file_snapshot: nil
     new(material:, event_type:, created_by_user:, file_snapshot:).record!
@@ -33,6 +33,11 @@ class MaterialVersionRecorder < VersionRecorder
       tag: @record.tag,
       tag_name: @record.tag&.name,
       tag_category: @record.tag&.category,
+      source_kind: @record.source_kind,
+      source_uri: @record.source_uri,
+      source_path: @record.source_path,
+      source_file_id: @record.source_file_id,
+      normalized_source_key: @record.normalized_source_key,
       export_paths_json: @record.snapshot_export_paths,
       discarded_at: @record.discarded_at,
       file_blob_id: file_snapshot[:file_blob_id],
@@ -40,9 +45,7 @@ class MaterialVersionRecorder < VersionRecorder
       file_content_type: file_snapshot[:file_content_type],
       file_byte_size: file_snapshot[:file_byte_size],
       file_checksum: file_snapshot[:file_checksum],
-      file_sha256: file_snapshot[:file_sha256],
-      file_suppressed_at: @record.file_suppressed_at,
-      file_suppression_reason: @record.file_suppression_reason }
+      file_sha256: file_snapshot[:file_sha256] }
   end
 
   def build_file_snapshot blob
@@ -54,7 +57,7 @@ class MaterialVersionRecorder < VersionRecorder
       file_content_type: blob.content_type,
       file_byte_size: blob.byte_size,
       file_checksum: blob.checksum,
-      file_sha256: blob.metadata['sha256'] }
+      file_sha256: MaterialFileSha256.metadata_sha256(blob) }
   end
 
   def empty_file_snapshot

backend/app/services/material_zip_exporter.rb

@@ -40,7 +40,6 @@ class MaterialZipExporter
            .joins(:material)
            .merge(Material.kept)
            .where(profile: @profile)
-           .where(materials: { file_suppressed_at: nil })
            .order(:export_path)
 
     rows = rows.where(materials: { tag_id: @tag_id }) if @tag_id

backend/app/services/post_version_recorder.rb

@@ -23,6 +23,7 @@ class PostVersionRecorder < VersionRecorder
     { title: @record.title,
       url: @record.url,
       thumbnail_base: @record.thumbnail_base,
+      video_ms: @record.video_ms,
       tags: @record.snapshot_tag_names.join(' '),
       parent_post_ids: @record.snapshot_parent_post_ids.join(' '),
       original_created_from: @record.original_created_from,

backend/config/routes.rb

@@ -114,9 +114,7 @@ Rails.application.routes.draw do
   end
 
   get 'materials/download.zip', to: 'materials#download'
-  resources :materials, only: [:index, :show, :create, :update, :destroy] do
-    member do
-      patch :suppress_file
-    end
-  end
+  get 'materials/versions', to: 'material_versions#index'
+  resources :material_sync_suppressions, path: 'materials/suppressions', only: [:index, :create]
+  resources :materials, only: [:index, :show, :create, :update, :destroy]
 end

backend/db/migrate/20260519013100_add_video_ms_to_posts.rb

@@ -0,0 +1,9 @@
+class AddVideoMsToPosts < ActiveRecord::Migration[8.0]
+  def change
+    add_column :posts, :video_ms, :integer
+    add_index :posts, [:video_ms, :id], name: 'idx_posts_video_ms_id'
+
+    add_check_constraint :posts, 'video_ms IS NULL OR video_ms > 0',
+                         name: 'chk_posts_video_ms_positive'
+  end
+end

backend/db/migrate/20260622010000_create_post_tag_sections.rb

@@ -0,0 +1,19 @@
+class CreatePostTagSections < ActiveRecord::Migration[8.0]
+  def change
+    create_table :post_tag_sections, primary_key: [:post_id, :tag_id, :begin_ms] do |t|
+      t.references :post, null: false, foreign_key: true, index: false
+      t.references :tag, null: false, foreign_key: true, index: false
+      t.integer :begin_ms, null: false
+      t.integer :end_ms, null: true
+      t.timestamps
+
+      t.index [:post_id, :begin_ms], name: 'idx_post_tag_sections_post_id_begin_ms'
+
+      t.check_constraint 'begin_ms >= 0',
+                         name: 'chk_post_tag_sections_begin_ms_natural'
+
+      t.check_constraint 'end_ms IS NULL OR begin_ms < end_ms',
+                         name: 'chk_post_tag_sections_end_ms_after_begin_ms'
+    end
+  end
+end

backend/db/migrate/20260622020000_add_video_ms_to_post_versions.rb

@@ -0,0 +1,9 @@
+class AddVideoMsToPostVersions < ActiveRecord::Migration[8.0]
+  def change
+    add_column :post_versions, :video_ms, :integer
+    add_index :post_versions, [:video_ms, :post_id], name: 'idx_post_versions_video_ms_post_id'
+
+    add_check_constraint :post_versions, 'video_ms IS NULL OR video_ms > 0',
+                         name: 'chk_post_versions_video_ms_positive'
+  end
+end

backend/db/migrate/20260623000000_enhance_material_management.rb

@@ -2,9 +2,6 @@ class EnhanceMaterialManagement < ActiveRecord::Migration[8.0]
   def up
     change_table :materials, bulk: true do |t|
       t.integer :version_no, null: false, default: 1
-      t.datetime :file_suppressed_at
-      t.references :file_suppressed_by_user, foreign_key: { to_table: :users }
-      t.string :file_suppression_reason
     end
 
     change_table :material_versions, bulk: true do |t|
@@ -18,8 +15,6 @@ class EnhanceMaterialManagement < ActiveRecord::Migration[8.0]
       t.bigint :file_byte_size
       t.string :file_checksum
       t.string :file_sha256
-      t.datetime :file_suppressed_at
-      t.string :file_suppression_reason
     end
 
     execute <<~SQL.squish
@@ -35,7 +30,7 @@ class EnhanceMaterialManagement < ActiveRecord::Migration[8.0]
     add_index :material_versions, :file_blob_id
 
     add_check_constraint :material_versions,
-                         "event_type IN ('create', 'update', 'discard', 'restore', 'suppress')",
+                         "event_type IN ('create', 'update', 'discard', 'restore')",
                          name: 'material_versions_event_type_valid'
 
     create_table :material_export_items do |t|
@@ -87,12 +82,7 @@ class EnhanceMaterialManagement < ActiveRecord::Migration[8.0]
     remove_column :material_versions, :file_byte_size
     remove_column :material_versions, :file_checksum
     remove_column :material_versions, :file_sha256
-    remove_column :material_versions, :file_suppressed_at
-    remove_column :material_versions, :file_suppression_reason
 
-    remove_reference :materials, :file_suppressed_by_user, foreign_key: { to_table: :users }
     remove_column :materials, :version_no
-    remove_column :materials, :file_suppressed_at
-    remove_column :materials, :file_suppression_reason
   end
 end

backend/db/migrate/20260625000000_reconcile_material_sync_suppressions.rb

@@ -0,0 +1,118 @@
+class ReconcileMaterialSyncSuppressions < ActiveRecord::Migration[8.0]
+  MATERIAL_VERSION_EVENT_CONSTRAINT = 'material_versions_event_type_valid'
+
+  def up
+    ensure_material_sync_suppressions!
+    ensure_material_source_columns!
+    ensure_material_active_source_key!
+    remove_material_file_suppression!
+    remove_material_version_file_suppression!
+    reconcile_material_version_event_constraint!
+  end
+
+  def down
+    raise ActiveRecord::IrreversibleMigration
+  end
+
+  private
+
+  def ensure_material_sync_suppressions!
+    return if table_exists?(:material_sync_suppressions)
+
+    create_table :material_sync_suppressions do |t|
+      t.string :source_kind, null: false
+      t.string :source_uri
+      t.string :drive_path
+      t.string :drive_file_id
+      t.string :normalized_source_key, null: false
+      t.string :reason, null: false
+      t.references :created_by_user, foreign_key: { to_table: :users }
+      t.timestamps
+
+      t.index :normalized_source_key, unique: true
+      t.index :source_kind
+      t.index :drive_file_id
+    end
+  end
+
+  def ensure_material_source_columns!
+    add_column :materials, :source_kind, :string unless column_exists?(:materials, :source_kind)
+    add_column :materials, :source_uri, :string unless column_exists?(:materials, :source_uri)
+    add_column :materials, :source_path, :string unless column_exists?(:materials, :source_path)
+    unless column_exists?(:materials, :source_file_id)
+      add_column :materials, :source_file_id, :string
+    end
+    unless column_exists?(:materials, :normalized_source_key)
+      add_column :materials, :normalized_source_key, :string
+    end
+
+    if index_exists?(:materials, :normalized_source_key)
+      remove_index :materials, column: :normalized_source_key
+    end
+  end
+
+  def ensure_material_active_source_key!
+    unless column_exists?(:materials, :active_normalized_source_key)
+      change_table :materials do |t|
+        t.virtual :active_normalized_source_key,
+                  type: :string,
+                  as: 'IF(discarded_at IS NULL, normalized_source_key, NULL)',
+                  stored: false
+      end
+    end
+
+    return if index_exists?(:materials,
+                            :active_normalized_source_key,
+                            name: 'index_materials_on_active_normalized_source_key')
+
+    add_index :materials,
+              :active_normalized_source_key,
+              unique: true,
+              name: 'index_materials_on_active_normalized_source_key'
+  end
+
+  def remove_material_file_suppression!
+    if foreign_key_exists?(:materials, :users, column: :file_suppressed_by_user_id)
+      remove_foreign_key :materials, column: :file_suppressed_by_user_id
+    end
+
+    if index_exists?(:materials,
+                    :file_suppressed_by_user_id,
+                    name: 'index_materials_on_file_suppressed_by_user_id')
+      remove_index :materials, name: 'index_materials_on_file_suppressed_by_user_id'
+    end
+
+    remove_column :materials, :file_suppressed_at if column_exists?(
+        :materials,
+        :file_suppressed_at)
+    remove_column :materials, :file_suppressed_by_user_id if column_exists?(
+        :materials,
+        :file_suppressed_by_user_id)
+    remove_column :materials, :file_suppression_reason if column_exists?(
+        :materials,
+        :file_suppression_reason)
+  end
+
+  def remove_material_version_file_suppression!
+    remove_column :material_versions, :file_suppressed_at if column_exists?(
+        :material_versions,
+        :file_suppressed_at)
+    remove_column :material_versions, :file_suppression_reason if column_exists?(
+        :material_versions,
+        :file_suppression_reason)
+  end
+
+  def reconcile_material_version_event_constraint!
+    constraint = check_constraints(:material_versions).find do |candidate|
+      candidate.name == MATERIAL_VERSION_EVENT_CONSTRAINT
+    end
+    return if constraint && !constraint.expression.include?('suppress')
+
+    if constraint
+      remove_check_constraint :material_versions, name: MATERIAL_VERSION_EVENT_CONSTRAINT
+    end
+    add_check_constraint :material_versions,
+                         "event_type IN ('create', 'update', 'discard', 'restore')",
+                         name: MATERIAL_VERSION_EVENT_CONSTRAINT
+  end
+end

backend/db/migrate/20260625010000_create_material_sync_sources.rb

@@ -0,0 +1,22 @@
+class CreateMaterialSyncSources < ActiveRecord::Migration[8.0]
+  def change
+    create_table :material_sync_sources do |t|
+      t.string :name, null: false
+      t.string :source_kind, null: false
+      t.string :source_uri
+      t.string :source_path
+      t.string :source_file_id
+      t.string :profile, null: false, default: 'legacy_drive'
+      t.boolean :enabled, null: false, default: true
+      t.string :default_tag_name
+      t.string :export_path_prefix
+      t.datetime :last_synced_at
+      t.references :created_by_user, foreign_key: { to_table: :users }
+      t.references :updated_by_user, foreign_key: { to_table: :users }
+      t.timestamps
+
+      t.index :enabled
+      t.index :source_kind
+    end
+  end
+end

backend/db/migrate/20260626000000_add_source_snapshot_to_material_versions.rb

@@ -0,0 +1,19 @@
+class AddSourceSnapshotToMaterialVersions < ActiveRecord::Migration[8.0]
+  def change
+    unless column_exists?(:material_versions, :source_kind)
+      add_column :material_versions, :source_kind, :string
+    end
+    unless column_exists?(:material_versions, :source_uri)
+      add_column :material_versions, :source_uri, :string
+    end
+    unless column_exists?(:material_versions, :source_path)
+      add_column :material_versions, :source_path, :string
+    end
+    unless column_exists?(:material_versions, :source_file_id)
+      add_column :material_versions, :source_file_id, :string
+    end
+    unless column_exists?(:material_versions, :normalized_source_key)
+      add_column :material_versions, :normalized_source_key, :string
+    end
+  end
+end

backend/db/migrate/20260626010000_backfill_initial_material_versions.rb

@@ -0,0 +1,171 @@
+require 'json'
+
+class BackfillInitialMaterialVersions < ActiveRecord::Migration[8.0]
+  class MigrationMaterial < ActiveRecord::Base
+    self.table_name = 'materials'
+  end
+
+  class MigrationMaterialExportItem < ActiveRecord::Base
+    self.table_name = 'material_export_items'
+  end
+
+  class MigrationMaterialVersion < ActiveRecord::Base
+    self.table_name = 'material_versions'
+  end
+
+  class MigrationStorageAttachment < ActiveRecord::Base
+    self.table_name = 'active_storage_attachments'
+  end
+
+  class MigrationStorageBlob < ActiveRecord::Base
+    self.table_name = 'active_storage_blobs'
+  end
+
+  class MigrationTag < ActiveRecord::Base
+    self.table_name = 'tags'
+  end
+
+  class MigrationTagName < ActiveRecord::Base
+    self.table_name = 'tag_names'
+  end
+
+  def up
+    say_with_time 'Backfilling initial material versions' do
+      materials_without_versions.find_in_batches(batch_size: 500) do |materials|
+        material_ids = materials.map(&:id)
+        tags_by_id = load_tags(materials.map(&:tag_id).compact.uniq)
+        export_paths_by_material_id = load_export_paths(material_ids)
+        file_snapshots_by_material_id = load_file_snapshots(material_ids)
+
+        rows = materials.map do |material|
+          tag = tags_by_id[material.tag_id]
+          file_snapshot = file_snapshots_by_material_id[material.id] || empty_file_snapshot
+
+          { material_id: material.id,
+            version_no: 1,
+            event_type: 'create',
+            url: material.url,
+            parent_id: material.parent_id,
+            tag_id: material.tag_id,
+            tag_name: tag&.fetch(:name, nil),
+            tag_category: tag&.fetch(:category, nil),
+            source_kind: material.source_kind,
+            source_uri: material.source_uri,
+            source_path: material.source_path,
+            source_file_id: material.source_file_id,
+            normalized_source_key: material.normalized_source_key,
+            export_paths_json: export_paths_by_material_id[material.id] || { },
+            discarded_at: material.discarded_at,
+            file_blob_id: file_snapshot[:file_blob_id],
+            file_filename: file_snapshot[:file_filename],
+            file_content_type: file_snapshot[:file_content_type],
+            file_byte_size: file_snapshot[:file_byte_size],
+            file_checksum: file_snapshot[:file_checksum],
+            file_sha256: file_snapshot[:file_sha256],
+            created_by_user_id: material.created_by_user_id,
+            updated_by_user_id: material.updated_by_user_id,
+            created_at: material.created_at,
+            updated_at: material.created_at }
+        end
+
+        MigrationMaterialVersion.insert_all!(rows) if rows.present?
+      end
+    end
+
+    execute <<~SQL.squish
+      UPDATE materials
+      SET version_no = COALESCE(
+        (
+          SELECT MAX(material_versions.version_no)
+          FROM material_versions
+          WHERE material_versions.material_id = materials.id
+        ),
+        1
+      )
+    SQL
+  end
+
+  def down
+    raise ActiveRecord::IrreversibleMigration
+  end
+
+  private
+
+  def materials_without_versions
+    MigrationMaterial.where.not(id: MigrationMaterialVersion.select(:material_id))
+  end
+
+  def load_tags tag_ids
+    return { } if tag_ids.empty?
+
+    tag_name_ids_by_tag_id = MigrationTag.where(id: tag_ids).pluck(:id, :tag_name_id).to_h
+    tag_names_by_id =
+        MigrationTagName
+        .where(id: tag_name_ids_by_tag_id.values.uniq)
+        .pluck(:id, :name)
+        .to_h
+    categories_by_tag_id = MigrationTag.where(id: tag_ids).pluck(:id, :category).to_h
+
+    tag_ids.each_with_object({ }) do |tag_id, hash|
+      hash[tag_id] = { name: tag_names_by_id[tag_name_ids_by_tag_id[tag_id]],
+                       category: categories_by_tag_id[tag_id] }
+    end
+  end
+
+  def load_export_paths material_ids
+    MigrationMaterialExportItem
+      .where(material_id: material_ids)
+      .order(:material_id, :profile)
+      .pluck(:material_id, :profile, :export_path)
+      .each_with_object({ }) do |(material_id, profile, export_path), hash|
+        hash[material_id] ||= { }
+        hash[material_id][profile] = export_path
+      end
+  end
+
+  def load_file_snapshots material_ids
+    attachments_by_material_id =
+        MigrationStorageAttachment
+        .where(record_type: 'Material', name: 'file', record_id: material_ids)
+        .pluck(:record_id, :blob_id)
+        .to_h
+
+    blobs_by_id =
+        MigrationStorageBlob
+        .where(id: attachments_by_material_id.values.uniq)
+        .index_by(&:id)
+
+    attachments_by_material_id.each_with_object({ }) do |(material_id, blob_id), hash|
+      blob = blobs_by_id[blob_id]
+      next unless blob
+
+      hash[material_id] = {
+        file_blob_id: blob.id,
+        file_filename: blob.filename.to_s,
+        file_content_type: blob.content_type,
+        file_byte_size: blob.byte_size,
+        file_checksum: blob.checksum,
+        file_sha256: blob_metadata(blob)['sha256']
+      }
+    end
+  end
+
+  def empty_file_snapshot
+    { file_blob_id: nil,
+      file_filename: nil,
+      file_content_type: nil,
+      file_byte_size: nil,
+      file_checksum: nil,
+      file_sha256: nil }
+  end
+
+  def blob_metadata blob
+    metadata = blob.metadata
+    return metadata if metadata.is_a?(Hash)
+    return { } if metadata.blank?
+
+    JSON.parse(metadata)
+  rescue JSON::ParserError
+    { }
+  end
+end

backend/db/schema.rb

@@ -10,7 +10,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema[8.0].define(version: 2026_06_23_000000) do
+ActiveRecord::Schema[8.0].define(version: 2026_06_26_010000) do
   create_table "active_storage_attachments", charset: "utf8mb4", collation: "utf8mb4_0900_ai_ci", force: :cascade do |t|
     t.string "name", null: false
     t.string "record_type", null: false
@@ -156,6 +156,43 @@ ActiveRecord::Schema[8.0].define(version: 2026_06_23_000000) do
     t.index ["created_by_user_id"], name: "index_material_import_blocks_on_created_by_user_id"
   end
 
+  create_table "material_sync_sources", charset: "utf8mb4", collation: "utf8mb4_0900_ai_ci", force: :cascade do |t|
+    t.string "name", null: false
+    t.string "source_kind", null: false
+    t.string "source_uri"
+    t.string "source_path"
+    t.string "source_file_id"
+    t.string "profile", default: "legacy_drive", null: false
+    t.boolean "enabled", default: true, null: false
+    t.string "default_tag_name"
+    t.string "export_path_prefix"
+    t.datetime "last_synced_at"
+    t.bigint "created_by_user_id"
+    t.bigint "updated_by_user_id"
+    t.datetime "created_at", null: false
+    t.datetime "updated_at", null: false
+    t.index ["created_by_user_id"], name: "index_material_sync_sources_on_created_by_user_id"
+    t.index ["enabled"], name: "index_material_sync_sources_on_enabled"
+    t.index ["source_kind"], name: "index_material_sync_sources_on_source_kind"
+    t.index ["updated_by_user_id"], name: "index_material_sync_sources_on_updated_by_user_id"
+  end
+
+  create_table "material_sync_suppressions", charset: "utf8mb4", collation: "utf8mb4_0900_ai_ci", force: :cascade do |t|
+    t.string "source_kind", null: false
+    t.string "source_uri"
+    t.string "drive_path"
+    t.string "drive_file_id"
+    t.string "normalized_source_key", null: false
+    t.string "reason", null: false
+    t.bigint "created_by_user_id"
+    t.datetime "created_at", null: false
+    t.datetime "updated_at", null: false
+    t.index ["created_by_user_id"], name: "index_material_sync_suppressions_on_created_by_user_id"
+    t.index ["drive_file_id"], name: "index_material_sync_suppressions_on_drive_file_id"
+    t.index ["normalized_source_key"], name: "index_material_sync_suppressions_on_normalized_source_key", unique: true
+    t.index ["source_kind"], name: "index_material_sync_suppressions_on_source_kind"
+  end
+
   create_table "material_versions", charset: "utf8mb4", collation: "utf8mb4_0900_ai_ci", force: :cascade do |t|
     t.bigint "material_id", null: false
     t.integer "version_no", null: false
@@ -177,8 +214,11 @@ ActiveRecord::Schema[8.0].define(version: 2026_06_23_000000) do
     t.bigint "file_byte_size"
     t.string "file_checksum"
     t.string "file_sha256"
-    t.datetime "file_suppressed_at"
-    t.string "file_suppression_reason"
+    t.string "source_kind"
+    t.string "source_uri"
+    t.string "source_path"
+    t.string "source_file_id"
+    t.string "normalized_source_key"
     t.index ["created_by_user_id"], name: "index_material_versions_on_created_by_user_id"
     t.index ["discarded_at"], name: "index_material_versions_on_discarded_at"
     t.index ["file_blob_id"], name: "index_material_versions_on_file_blob_id"
@@ -188,7 +228,7 @@ ActiveRecord::Schema[8.0].define(version: 2026_06_23_000000) do
     t.index ["tag_id"], name: "index_material_versions_on_tag_id"
     t.index ["updated_by_user_id"], name: "index_material_versions_on_updated_by_user_id"
     t.index ["url"], name: "index_material_versions_on_url"
-    t.check_constraint "`event_type` in (_utf8mb4'create',_utf8mb4'update',_utf8mb4'discard',_utf8mb4'restore',_utf8mb4'suppress')", name: "material_versions_event_type_valid"
+    t.check_constraint "`event_type` in (_utf8mb4'create',_utf8mb4'update',_utf8mb4'discard',_utf8mb4'restore')", name: "material_versions_event_type_valid"
   end
 
   create_table "materials", charset: "utf8mb4", collation: "utf8mb4_0900_ai_ci", force: :cascade do |t|
@@ -202,13 +242,16 @@ ActiveRecord::Schema[8.0].define(version: 2026_06_23_000000) do
     t.datetime "discarded_at"
     t.virtual "active_url", type: :string, as: "if((`discarded_at` is null),`url`,NULL)"
     t.integer "version_no", default: 1, null: false
-    t.datetime "file_suppressed_at"
-    t.bigint "file_suppressed_by_user_id"
-    t.string "file_suppression_reason"
+    t.string "source_kind"
+    t.string "source_uri"
+    t.string "source_path"
+    t.string "source_file_id"
+    t.string "normalized_source_key"
+    t.virtual "active_normalized_source_key", type: :string, as: "if((`discarded_at` is null),`normalized_source_key`,NULL)"
+    t.index ["active_normalized_source_key"], name: "index_materials_on_active_normalized_source_key", unique: true
     t.index ["active_url"], name: "index_materials_on_active_url", unique: true
     t.index ["created_by_user_id"], name: "index_materials_on_created_by_user_id"
     t.index ["discarded_at"], name: "index_materials_on_discarded_at"
-    t.index ["file_suppressed_by_user_id"], name: "index_materials_on_file_suppressed_by_user_id"
     t.index ["parent_id"], name: "index_materials_on_parent_id"
     t.index ["tag_id"], name: "index_materials_on_tag_id"
     t.index ["updated_by_user_id"], name: "index_materials_on_updated_by_user_id"
@@ -255,6 +298,19 @@ ActiveRecord::Schema[8.0].define(version: 2026_06_23_000000) do
     t.index ["target_post_id"], name: "index_post_similarities_on_target_post_id"
   end
 
+  create_table "post_tag_sections", primary_key: ["post_id", "tag_id", "begin_ms"], charset: "utf8mb4", collation: "utf8mb4_0900_ai_ci", force: :cascade do |t|
+    t.bigint "post_id", null: false
+    t.bigint "tag_id", null: false
+    t.integer "begin_ms", null: false
+    t.integer "end_ms"
+    t.datetime "created_at", null: false
+    t.datetime "updated_at", null: false
+    t.index ["post_id", "begin_ms"], name: "idx_post_tag_sections_post_id_begin_ms"
+    t.index ["tag_id"], name: "fk_rails_8be3847903"
+    t.check_constraint "(`end_ms` is null) or (`begin_ms` < `end_ms`)", name: "chk_post_tag_sections_end_ms_after_begin_ms"
+    t.check_constraint "`begin_ms` >= 0", name: "chk_post_tag_sections_begin_ms_natural"
+  end
+
   create_table "post_tags", charset: "utf8mb4", collation: "utf8mb4_0900_ai_ci", force: :cascade do |t|
     t.bigint "post_id", null: false
     t.bigint "tag_id", null: false
@@ -288,9 +344,12 @@ ActiveRecord::Schema[8.0].define(version: 2026_06_23_000000) do
     t.datetime "original_created_before"
     t.datetime "created_at", null: false
     t.bigint "created_by_user_id"
+    t.integer "video_ms"
     t.index ["created_by_user_id"], name: "index_post_versions_on_created_by_user_id"
     t.index ["post_id", "version_no"], name: "index_post_versions_on_post_id_and_version_no", unique: true
     t.index ["post_id"], name: "index_post_versions_on_post_id"
+    t.index ["video_ms", "post_id"], name: "idx_post_versions_video_ms_post_id"
+    t.check_constraint "(`video_ms` is null) or (`video_ms` > 0)", name: "chk_post_versions_video_ms_positive"
     t.check_constraint "`event_type` in (_utf8mb4'create',_utf8mb4'update',_utf8mb4'discard',_utf8mb4'restore')", name: "post_versions_event_type_valid"
     t.check_constraint "`version_no` > 0", name: "post_versions_version_no_positive"
   end
@@ -305,8 +364,11 @@ ActiveRecord::Schema[8.0].define(version: 2026_06_23_000000) do
     t.datetime "original_created_before"
     t.datetime "updated_at", null: false
     t.integer "version_no", null: false
+    t.integer "video_ms"
     t.index ["uploaded_user_id"], name: "index_posts_on_uploaded_user_id"
     t.index ["url"], name: "index_posts_on_url", unique: true
+    t.index ["video_ms", "id"], name: "idx_posts_video_ms_id"
+    t.check_constraint "(`video_ms` is null) or (`video_ms` > 0)", name: "chk_posts_video_ms_positive"
     t.check_constraint "`version_no` > 0", name: "chk_posts_version_no_positive"
   end
 
@@ -615,6 +677,9 @@ ActiveRecord::Schema[8.0].define(version: 2026_06_23_000000) do
   add_foreign_key "material_export_items", "materials"
   add_foreign_key "material_export_items", "users", column: "created_by_user_id"
   add_foreign_key "material_import_blocks", "users", column: "created_by_user_id"
+  add_foreign_key "material_sync_sources", "users", column: "created_by_user_id"
+  add_foreign_key "material_sync_sources", "users", column: "updated_by_user_id"
+  add_foreign_key "material_sync_suppressions", "users", column: "created_by_user_id"
   add_foreign_key "material_versions", "materials"
   add_foreign_key "material_versions", "materials", column: "parent_id"
   add_foreign_key "material_versions", "tags"
@@ -623,7 +688,6 @@ ActiveRecord::Schema[8.0].define(version: 2026_06_23_000000) do
   add_foreign_key "materials", "materials", column: "parent_id"
   add_foreign_key "materials", "tags"
   add_foreign_key "materials", "users", column: "created_by_user_id"
-  add_foreign_key "materials", "users", column: "file_suppressed_by_user_id"
   add_foreign_key "materials", "users", column: "updated_by_user_id"
   add_foreign_key "nico_tag_relations", "tags"
   add_foreign_key "nico_tag_relations", "tags", column: "nico_tag_id"
@@ -633,6 +697,8 @@ ActiveRecord::Schema[8.0].define(version: 2026_06_23_000000) do
   add_foreign_key "post_implications", "posts", column: "parent_post_id"
   add_foreign_key "post_similarities", "posts"
   add_foreign_key "post_similarities", "posts", column: "target_post_id"
+  add_foreign_key "post_tag_sections", "posts"
+  add_foreign_key "post_tag_sections", "tags"
   add_foreign_key "post_tags", "posts"
   add_foreign_key "post_tags", "tags"
   add_foreign_key "post_tags", "users", column: "created_user_id"

backend/db/seeds.rb

@@ -7,3 +7,21 @@
 #   ["Action", "Comedy", "Drama", "Horror"].each do |genre_name|
 #     MovieGenre.find_or_create_by!(name: genre_name)
 #   end
+
+material_sync_source_uri = ENV['MATERIAL_SYNC_SOURCE_URI']
+material_sync_source_file_id = ENV['MATERIAL_SYNC_SOURCE_FILE_ID']
+
+if material_sync_source_uri.present? || material_sync_source_file_id.present?
+  source = MaterialSyncSource.find_or_initialize_by(
+      name: ENV.fetch('MATERIAL_SYNC_SOURCE_NAME', 'Legacy URI material sync'))
+  source.assign_attributes(
+      source_kind: ENV.fetch('MATERIAL_SYNC_SOURCE_KIND', 'uri'),
+      source_uri: material_sync_source_uri,
+      source_path: ENV['MATERIAL_SYNC_SOURCE_PATH'],
+      source_file_id: material_sync_source_file_id,
+      profile: ENV.fetch('MATERIAL_SYNC_SOURCE_PROFILE', 'legacy_drive'),
+      enabled: ENV.fetch('MATERIAL_SYNC_SOURCE_ENABLED', 'true') != 'false',
+      default_tag_name: ENV['MATERIAL_SYNC_SOURCE_TAG_NAME'],
+      export_path_prefix: ENV['MATERIAL_SYNC_EXPORT_PATH_PREFIX'])
+  source.save!
+end

backend/lib/tasks/sync_materials.rake

@@ -0,0 +1,51 @@
+namespace :materials do
+  desc '素材同期'
+  task sync: :environment do
+    result = MaterialSyncRunner.sync_enabled!
+    message = [
+      "materials:sync imported=#{ result.imported }",
+      "updated=#{ result.updated }",
+      "unchanged=#{ result.unchanged }",
+      "suppressed=#{ result.suppressed }",
+      "failed=#{ result.failed }"
+    ].join(' ')
+
+    Rails.logger.info(message)
+    puts message
+
+    result.errors.each do |error|
+      Rails.logger.warn(error.to_json)
+      warn error.to_json
+    end
+  end
+
+  namespace :thumbnails do
+    desc '素材サムネールを補完'
+    task backfill: :environment do
+      counts = Hash.new(0)
+
+      Material
+        .with_attached_file
+        .with_attached_thumbnail
+        .find_each do |material|
+          next unless material.file.attached?
+          next if material.thumbnail.attached?
+
+          result = MaterialThumbnailGenerator.generate!(material)
+          counts[result] += 1
+        end
+
+      message =
+          "materials:thumbnails:backfill " \
+          "attached=#{ counts[:attached] } " \
+          "no_file=#{ counts[:no_file] } " \
+          "unsupported_content_type=#{ counts[:unsupported_content_type] } " \
+          "generation_failed=#{ counts[:generation_failed] } " \
+          "attach_failed=#{ counts[:attach_failed] } " \
+          "file_not_found=#{ counts[:file_not_found] } " \
+          "mini_magick_error=#{ counts[:mini_magick_error] }"
+      Rails.logger.info(message)
+      puts message
+    end
+  end
+end

backend/spec/factories/post_tag_sections.rb

@@ -0,0 +1,8 @@
+FactoryBot.define do
+  factory :post_tag_section do
+    association :post
+    association :tag
+    begin_ms { 1_000 }
+    end_ms { 2_000 }
+  end
+end

backend/spec/factories/post_tags.rb

@@ -0,0 +1,6 @@
+FactoryBot.define do
+  factory :post_tag do
+    association :post
+    association :tag
+  end
+end

backend/spec/factories/posts.rb

@@ -0,0 +1,8 @@
+FactoryBot.define do
+  factory :post do
+    sequence(:url) { |n| "https://example.com/factory-post-#{ n }" }
+    title { 'factory post' }
+    thumbnail_base { nil }
+    uploaded_user { nil }
+  end
+end

backend/spec/models/material_spec.rb

@@ -0,0 +1,19 @@
+require 'rails_helper'
+
+RSpec.describe Material, type: :model do
+  let(:user) { create(:user, :member) }
+
+  it 'allows only material source kinds, not suppression prefix kinds' do
+    material = described_class.new(url: 'https://example.com/material',
+                                   source_kind: 'google_drive_path_prefix',
+                                   source_path: '素材/危険',
+                                   created_by_user: user,
+                                   updated_by_user: user)
+
+    expect(material).not_to be_valid
+    expect(material.errors[:source_kind]).to be_present
+
+    material.source_kind = 'google_drive_path'
+    expect(material).to be_valid
+  end
+end

backend/spec/models/post_tag_spec.rb

@@ -0,0 +1,41 @@
+RSpec.describe PostTag, type: :model do
+  describe '#sections' do
+    it 'loads sections by post_id and tag_id' do
+      post_tag = create(:post_tag)
+      section = create(:post_tag_section,
+                       post: post_tag.post,
+                       tag: post_tag.tag,
+                       begin_ms: 1000,
+                       end_ms: 2000)
+
+      expect(post_tag.sections).to contain_exactly(section)
+    end
+
+    it 'does not load sections for another tag on the same post' do
+      post = create(:post)
+      tag = create(:tag)
+      other_tag = create(:tag)
+
+      post_tag = create(:post_tag, post:, tag:)
+      create(:post_tag_section,
+             post:,
+             tag: other_tag,
+             begin_ms: 1000,
+             end_ms: 2000)
+
+      expect(post_tag.sections).to be_empty
+    end
+
+    it 'allows open-ended sections' do
+      post_tag = create(:post_tag)
+      section = create(:post_tag_section,
+                       post: post_tag.post,
+                       tag: post_tag.tag,
+                       begin_ms: 1000,
+                       end_ms: nil)
+
+      expect(section).to be_valid
+      expect(post_tag.sections).to contain_exactly(section)
+    end
+  end
+end

backend/spec/models/tag_implication_spec.rb

@@ -0,0 +1,36 @@
+require 'rails_helper'
+
+RSpec.describe TagImplication, type: :model do
+  it 'rejects a parent tag that would create a cycle' do
+    child = create(:tag, name: 'tag_implication_cycle_child')
+    parent = create(:tag, name: 'tag_implication_cycle_parent')
+
+    described_class.create!(tag: child, parent_tag: parent)
+
+    implication = described_class.new(tag: parent, parent_tag: child)
+
+    expect(implication).not_to be_valid
+    expect(implication.errors[:parent_tag_id]).to include(
+      '親タグに子孫タグを指定すると循環します．'
+    )
+    expect(implication.errors[:base]).to be_present
+  end
+
+  it 'terminates even when existing data already contains a cycle' do
+    child = create(:tag, name: 'tag_implication_existing_cycle_child')
+    parent = create(:tag, name: 'tag_implication_existing_cycle_parent')
+    ancestor = create(:tag, name: 'tag_implication_existing_cycle_ancestor')
+
+    described_class.create!(tag: parent, parent_tag: ancestor)
+    described_class.insert_all!(
+      [
+        { tag_id: ancestor.id, parent_tag_id: parent.id,
+          created_at: Time.current, updated_at: Time.current }
+      ]
+    )
+
+    implication = described_class.new(tag: child, parent_tag: parent)
+
+    expect(implication).to be_valid
+  end
+end

backend/spec/models/tag_spec.rb

@@ -19,6 +19,95 @@ RSpec.describe Tag, type: :model do
         expect(error.tag_names).to eq([deprecated_tag.name])
       }
     end
+
+    it 'rejects invalid section literals instead of treating them as zero' do
+      expect {
+        described_class.normalise_tags!(
+          ['normalise_invalid_section[1:aa-2:00]'],
+          with_sections: true
+        )
+      }.to raise_error(Tag::SectionLiteralParseError)
+    end
+
+    it 'parses open-ended section literals' do
+      result = described_class.normalise_tags!(
+        ['伊地知ニジカ[1:00-]'],
+        with_sections: true
+      )
+
+      tag = result.fetch(:tags).find { _1.name == '伊地知ニジカ' }
+      expect(result.fetch(:sections).fetch(tag.id)).to eq([[60_000, nil]])
+    end
+
+    it 'parses omitted begin as zero' do
+      result = described_class.normalise_tags!(
+        ['伊地知ニジカ[-1:00]'],
+        with_sections: true
+      )
+
+      tag = result.fetch(:tags).find { _1.name == '伊地知ニジカ' }
+      expect(result.fetch(:sections).fetch(tag.id)).to eq([[0, 60_000]])
+    end
+
+    it 'treats fully open section literals as plain tags' do
+      result = described_class.normalise_tags!(
+        ['伊地知ニジカ[-]'],
+        with_sections: true
+      )
+
+      tag = result.fetch(:tags).find { _1.name == '伊地知ニジカ' }
+      expect(result.fetch(:sections)[tag.id]).to be_nil
+    end
+
+    it 'treats [0:00-] as a plain tag' do
+      result = described_class.normalise_tags!(
+        ['伊地知ニジカ[0:00-]'],
+        with_sections: true
+      )
+
+      tag = result.fetch(:tags).find { _1.name == '伊地知ニジカ' }
+      expect(result.fetch(:sections)[tag.id]).to be_nil
+    end
+
+    it 'expands zero-width sections to one millisecond' do
+      result = described_class.normalise_tags!(
+        ['伊地知ニジカ[1:00-1:00]'],
+        with_sections: true
+      )
+
+      tag = result.fetch(:tags).find { _1.name == '伊地知ニジカ' }
+      expect(result.fetch(:sections).fetch(tag.id)).to eq([[60_000, 60_001]])
+    end
+
+    it 'swaps reversed section boundaries' do
+      result = described_class.normalise_tags!(
+        ['伊地知ニジカ[2:00-1:00]'],
+        with_sections: true
+      )
+
+      tag = result.fetch(:tags).find { _1.name == '伊地知ニジカ' }
+      expect(result.fetch(:sections).fetch(tag.id)).to eq([[60_000, 120_000]])
+    end
+
+    it 'merges open-ended sections over later bounded sections' do
+      result = described_class.normalise_tags!(
+        ['伊地知ニジカ[1:00-][2:00-3:00]'],
+        with_sections: true
+      )
+
+      tag = result.fetch(:tags).find { _1.name == '伊地知ニジカ' }
+      expect(result.fetch(:sections).fetch(tag.id)).to eq([[60_000, nil]])
+    end
+
+    it 'merges adjacent bounded and open-ended sections' do
+      result = described_class.normalise_tags!(
+        ['伊地知ニジカ[1:00-3:00][3:00-]'],
+        with_sections: true
+      )
+
+      tag = result.fetch(:tags).find { _1.name == '伊地知ニジカ' }
+      expect(result.fetch(:sections).fetch(tag.id)).to eq([[60_000, nil]])
+    end
   end
 
   describe '.expand_parent_tags' do
@@ -54,7 +143,17 @@ RSpec.describe Tag, type: :model do
       first = create(:tag, name: 'expand_cycle_first')
       second = create(:tag, name: 'expand_cycle_second')
       TagImplication.create!(tag: first, parent_tag: second)
-      TagImplication.create!(tag: second, parent_tag: first)
+      now = Time.current
+      TagImplication.insert_all!(
+        [
+          {
+            tag_id: second.id,
+            parent_tag_id: first.id,
+            created_at: now,
+            updated_at: now
+          }
+        ]
+      )
 
       expect(described_class.expand_parent_tags([first])).to contain_exactly(first, second)
     end

backend/spec/requests/materials_spec.rb

@@ -64,27 +64,36 @@ RSpec.describe 'Materials API', type: :request do
         'name' => 'material_index_b',
         'category' => 'material'
       )
-      expect(row['created_by_user']).to include(
-        'id' => member_user.id,
-        'name' => member_user.name
-      )
       expect(row['content_type']).to eq('image/png')
+      expect(row['media_kind']).to eq('image')
     end
 
-    it 'filters materials by tag_id' do
-      get '/materials', params: { tag_id: material_a.tag_id }
+    it 'filters materials by q' do
+      get '/materials', params: { q: 'material_index_a' }
 
       expect(response).to have_http_status(:ok)
       expect(json['count']).to eq(1)
       expect(response_materials.map { |m| m['id'] }).to eq([material_a.id])
     end
 
-    it 'filters materials by parent_id' do
-      get '/materials', params: { parent_id: material_a.id }
+    it 'filters materials by tag_state' do
+      untagged =
+          build_material(tag: nil, user: member_user,
+                         file: dummy_upload(filename: 'untagged.png'))
+
+      get '/materials', params: { tag_state: 'untagged' }
 
       expect(response).to have_http_status(:ok)
       expect(json['count']).to eq(1)
-      expect(response_materials.map { |m| m['id'] }).to eq([material_b.id])
+      expect(response_materials.map { |m| m['id'] }).to eq([untagged.id])
+    end
+
+    it 'filters materials by media_kind' do
+      get '/materials', params: { media_kind: 'image' }
+
+      expect(response).to have_http_status(:ok)
+      expect(json['count']).to eq(2)
+      expect(response_materials.map { |m| m['media_kind'] }).to all(eq('image'))
     end
 
     it 'paginates and keeps total count' do
@@ -104,6 +113,68 @@ RSpec.describe 'Materials API', type: :request do
       expect(response_materials.size).to eq(1)
       expect(response_materials.first['id']).to eq(material_b.id)
     end
+
+    it 'filters by descendant tags and returns stable parent tag groups' do
+      root =
+          Tag.create!(tag_name: TagName.create!(name: 'material_scope_root'),
+                      category: :material)
+      child_b =
+          Tag.create!(tag_name: TagName.create!(name: 'material_scope_b'),
+                      category: :material)
+      child_a =
+          Tag.create!(tag_name: TagName.create!(name: 'material_scope_a'),
+                      category: :material)
+      deprecated =
+          Tag.create!(tag_name: TagName.create!(name: 'material_scope_old'),
+                      category: :material,
+                      deprecated_at: Time.current)
+      grandchild =
+          Tag.create!(tag_name: TagName.create!(name: 'material_scope_grandchild'),
+                      category: :material)
+      root_material =
+          build_material(tag: root, user: member_user,
+                         file: dummy_upload(filename: 'root.png'))
+      child_a_material =
+          build_material(tag: child_a, user: member_user,
+                         file: dummy_upload(filename: 'child_a.png'))
+      grandchild_material =
+          build_material(tag: grandchild, user: member_user,
+                         file: dummy_upload(filename: 'grandchild.png'))
+
+      TagImplication.create!(parent_tag: root, tag: child_b)
+      TagImplication.create!(parent_tag: root, tag: child_a)
+      TagImplication.create!(parent_tag: child_b, tag: deprecated)
+      TagImplication.create!(parent_tag: deprecated, tag: grandchild)
+
+      get '/materials',
+          params: { tag_id: root.id, include_descendants: '1',
+                    group_by: 'parent_tag', sort: 'id', direction: 'asc' }
+
+      expect(response).to have_http_status(:ok)
+      expect(response_materials.map { |m| m['id'] })
+        .to include(root_material.id, child_a_material.id, grandchild_material.id)
+      expect(json['tag_scope']).to eq(
+        'tag' => {
+          'id' => root.id,
+          'name' => 'material_scope_root',
+          'category' => 'material'
+        },
+        'include_descendants' => true
+      )
+      expect(json['groups'].map { |group| group.dig('tag', 'name') })
+        .to eq(['material_scope_a', 'material_scope_b', 'material_scope_root'])
+      expect(json['groups'].find { |group| group.dig('tag', 'id') == child_b.id }
+        .fetch('material_ids')).to eq([grandchild_material.id])
+    end
+
+    it 'returns nil tag_scope when tag_id is unknown' do
+      get '/materials', params: { tag_id: 999_999, group_by: 'parent_tag' }
+
+      expect(response).to have_http_status(:ok)
+      expect(json['tag_scope']).to be_nil
+      expect(json['groups']).to eq([])
+      expect(response_materials).to eq([])
+    end
   end
 
   describe 'GET /materials/:id' do
@@ -528,9 +599,8 @@ RSpec.describe 'Materials API', type: :request do
       expect(response.body.b).not_to include('素材/b.png'.b)
     end
 
-    it 'does not include suppressed materials' do
-      material_b.update!(file_suppressed_at: Time.current,
-                         file_suppression_reason: 'copyright_high_risk')
+    it 'does not include disabled export items' do
+      material_b.material_export_items.first.update!(enabled: false)
 
       get '/materials/download.zip', params: { profile: 'legacy_drive' }
 
@@ -540,62 +610,78 @@ RSpec.describe 'Materials API', type: :request do
     end
   end
 
-  describe 'PATCH /materials/:id/suppress_file' do
+  describe 'GET /materials/versions' do
     let!(:tag) do
-      Tag.create!(tag_name: TagName.create!(name: 'material_suppress'), category: :material)
+      Tag.create!(tag_name: TagName.create!(name: 'material_history'), category: :material)
     end
     let!(:material) do
-      build_material(tag:, user: member_user, file: dummy_upload(filename: 'suppress.png'))
+      build_material(tag:, user: member_user, file: dummy_upload(filename: 'history.png'))
     end
 
-    it 'allows admin to suppress a file and records a suppress version' do
-      sign_in_as(admin_user)
+    it 'returns material versions in reverse chronological order' do
+      MaterialVersionRecorder.record!(material:, event_type: :create,
+                                      created_by_user: member_user)
+      material.update!(url: 'https://example.com/history')
+      MaterialVersionRecorder.record!(material:, event_type: :update,
+                                      created_by_user: admin_user)
+
+      get '/materials/versions', params: { material_id: material.id }
+
+      expect(response).to have_http_status(:ok)
+      expect(json['count']).to eq(2)
+      versions = json.fetch('versions')
+      expect(versions.map { |v| v['version_no'] }).to eq([2, 1])
+      expect(versions.first).to include(
+        'material_id' => material.id,
+        'event_type' => 'update',
+        'tag_name' => 'material_history',
+        'file_filename' => 'history.png',
+        'url' => 'https://example.com/history'
+      )
+      expect(versions.first['created_by_user']).to include('id' => admin_user.id)
+    end
+
+    it 'filters material versions by tag and event_type' do
       MaterialVersionRecorder.record!(material:, event_type: :create,
                                       created_by_user: member_user)
 
-      expect do
-        patch "/materials/#{ material.id }/suppress_file",
-              params: { reason: 'copyright_high_risk' }
-      end.to change(MaterialVersion, :count).by(1)
+      get '/materials/versions', params: {
+        tag: 'material_history',
+        event_type: 'create'
+      }
 
       expect(response).to have_http_status(:ok)
+      expect(json.fetch('versions').map { |v| v['material_id'] }).to include(material.id)
+      expect(json.fetch('versions').map { |v| v['event_type'] }).to all(eq('create'))
+    end
+  end
 
-      material.reload
-      expect(material.file_suppressed_at).to be_present
-      expect(material.file_suppressed_by_user).to eq(admin_user)
-      expect(material.file_suppression_reason).to eq('copyright_high_risk')
-      expect(material.material_versions.order(:version_no).last.event_type).to eq('suppress')
-      expect(json['file']).to be_nil
-      expect(json['file_suppressed_at']).to be_present
+  describe 'material sync suppressions' do
+    it 'requires member permission for index' do
+      sign_out
+
+      get '/materials/suppressions'
+
+      expect(response).to have_http_status(:unauthorized)
     end
 
-    it 'purges blob when purge=true is requested' do
-      sign_in_as(admin_user)
-      old_blob_id = material.file.blob.id
-      MaterialVersionRecorder.record!(material:, event_type: :create,
-                                      created_by_user: member_user)
-
-      expect do
-        patch "/materials/#{ material.id }/suppress_file",
-              params: { reason: 'copyright_takedown', purge: '1' }
-      end.to have_enqueued_job(ActiveStorage::PurgeJob)
-
-      expect(response).to have_http_status(:ok)
-
-      version = material.material_versions.order(:version_no).last
-      expect(version.event_type).to eq('suppress')
-      expect(version.file_blob_id).to eq(old_blob_id)
-      expect(version.file_filename).to eq('suppress.png')
-      expect(version.file_sha256).to be_present
-    end
-
-    it 'rejects member suppression' do
+    it 'creates source suppression as member' do
       sign_in_as(member_user)
 
-      patch "/materials/#{ material.id }/suppress_file",
-            params: { reason: 'copyright_high_risk' }
+      expect do
+        post '/materials/suppressions', params: {
+          source_kind: 'google_drive_path_prefix',
+          drive_path: '伊地知ニジカ/危険素材',
+          reason: 'copyright_high_risk'
+        }
+      end.to change(MaterialSyncSuppression, :count).by(1)
 
-      expect(response).to have_http_status(:forbidden)
+      expect(response).to have_http_status(:created)
+      expect(json).to include(
+        'source_kind' => 'google_drive_path_prefix',
+        'drive_path' => '伊地知ニジカ/危険素材',
+        'normalized_source_key' => 'google_drive_path_prefix:伊地知ニジカ/危険素材'
+      )
     end
   end
 

backend/spec/requests/posts_spec.rb

@@ -1,4 +1,5 @@
 require 'rails_helper'
+require 'base64'
 require 'set'
 
 include ActiveSupport::Testing::TimeHelpers
@@ -8,6 +9,11 @@ RSpec.describe 'Posts API', type: :request do
   # resized_thumbnail! が MiniMagick 依存でコケやすいので request spec ではスタブしとくのが無難。
   before do
     allow_any_instance_of(Post).to receive(:resized_thumbnail!).and_return(true)
+    allow(Post).to receive(:resized_thumbnail_attachment).and_return(
+      io: StringIO.new('dummy'),
+      filename: 'resized_thumbnail.jpg',
+      content_type: 'image/jpeg'
+    )
   end
 
   def create_nico_tag!(name)
@@ -19,6 +25,18 @@ RSpec.describe 'Posts API', type: :request do
     Rack::Test::UploadedFile.new(StringIO.new('dummy'), 'image/jpeg', original_filename: 'dummy.jpg')
   end
 
+  def real_thumbnail_upload
+    gif =
+        Base64.decode64(
+            'R0lGODdhAQABAIABAP///wAAACwAAAAAAQABAAACAkQBADs=')
+
+    Rack::Test::UploadedFile.new(
+      StringIO.new(gif),
+      'image/gif',
+      original_filename: 'thumbnail.gif'
+    )
+  end
+
   def post_write_params params = { }
     { parent_post_ids: '' }.merge(params)
   end
@@ -36,6 +54,7 @@ RSpec.describe 'Posts API', type: :request do
             title: post.title,
             url: post.url,
             thumbnail_base: post.thumbnail_base,
+            video_ms: post.video_ms,
             tags: post.snapshot_tag_names.join(' '),
             parent_post_ids: post.snapshot_parent_post_ids.join(' '),
             original_created_from: post.original_created_from,
@@ -127,6 +146,22 @@ RSpec.describe 'Posts API', type: :request do
       expect(all_tag_names).to include("spec_tag")
     end
 
+    it 'keeps children and sections keys in non-detail tag responses' do
+      PostTagSection.create!(post: hit_post, tag:, begin_ms: 1_000, end_ms: nil)
+
+      get '/posts'
+
+      expect(response).to have_http_status(:ok)
+
+      hit_json = json.fetch('posts').find { |post| post['id'] == hit_post.id }
+      tag_json = hit_json.fetch('tags').find { |item| item['name'] == 'spec_tag' }
+
+      expect(tag_json.fetch('children')).to eq([])
+      expect(tag_json.fetch('sections')).to eq([
+        { 'begin_ms' => 1_000, 'end_ms' => nil }
+      ])
+    end
+
     context "when q is provided" do
       it "filters posts by q (hit case)" do
         get "/posts", params: { tags: "spec_tag" }
@@ -696,6 +731,66 @@ RSpec.describe 'Posts API', type: :request do
       expect(json['tags'][0]).to have_key('name')
     end
 
+    it '201 when posting manually with a thumbnail' do
+      sign_in_as(member)
+      allow(Post).to receive(:resized_thumbnail_attachment).and_call_original
+
+      post '/posts', params: post_write_params(
+        title: 'thumbnail post',
+        url: 'https://example.com/thumbnail-post',
+        tags: 'spec_tag',
+        thumbnail: real_thumbnail_upload
+      )
+
+      expect(response).to have_http_status(:created)
+      post_record = Post.find(json.fetch('id'))
+      expect(post_record.thumbnail).to be_attached
+      expect(post_record.thumbnail.blob.content_type).to eq('image/jpeg')
+      expect { post_record.thumbnail.download }.not_to raise_error
+    end
+
+    it 'resizes the thumbnail before the create transaction begins' do
+      sign_in_as(member)
+
+      open_transactions = []
+      baseline_open_transactions = Post.connection.open_transactions
+      allow(Post).to receive(:resized_thumbnail_attachment) do |_upload|
+        open_transactions << Post.connection.open_transactions
+        { io: StringIO.new('dummy'),
+          filename: 'resized_thumbnail.jpg',
+          content_type: 'image/jpeg' }
+      end
+
+      post '/posts', params: post_write_params(
+        title: 'transaction post',
+        url: 'https://example.com/transaction-post',
+        tags: 'spec_tag',
+        thumbnail: dummy_upload
+      )
+
+      expect(response).to have_http_status(:created)
+      expect(open_transactions).to eq([baseline_open_transactions])
+    end
+
+    it 'returns 422 and does not create a post when thumbnail resize fails' do
+      sign_in_as(member)
+      allow(Post).to receive(:resized_thumbnail_attachment).and_raise(MiniMagick::Error)
+
+      expect {
+        post '/posts', params: post_write_params(
+          title: 'broken thumbnail post',
+          url: 'https://example.com/broken-thumbnail-post',
+          tags: 'spec_tag',
+          thumbnail: dummy_upload
+        )
+      }.not_to change(Post, :count)
+
+      expect(response).to have_http_status(:unprocessable_entity)
+      expect(json.fetch('errors')).to include(
+        'thumbnail' => ['サムネイル画像の変換に失敗しました．']
+      )
+    end
+
     it '201 and creates post + tags when member and tags have aliases' do
       sign_in_as(member)
 
@@ -767,6 +862,198 @@ RSpec.describe 'Posts API', type: :request do
       expect(saved_names).not_to include('deprecated_parent', 'deprecated_grandparent')
     end
 
+    it 'returns validation error for an invalid section literal' do
+      sign_in_as(member)
+
+      post '/posts', params: post_write_params(
+        title: 'invalid section literal',
+        url: 'https://example.com/invalid-section-literal',
+        tags: 'spec_tag[1:aa-2:00]',
+        thumbnail: dummy_upload
+      )
+
+      expect(response).to have_http_status(:unprocessable_entity)
+      expect(json).to include(
+        'type' => 'validation_error',
+        'message' => '入力内容を確認してください．'
+      )
+      expect(json.fetch('errors')).to include(
+        'tags' => ['タグ区間の記法が不正です．']
+      )
+    end
+
+    it 'creates a video post with duration' do
+      sign_in_as(member)
+
+      post '/posts', params: post_write_params(
+        title: 'video post',
+        url: 'https://example.com/video-post',
+        tags: '動画 spec_tag',
+        duration: '3:00.500',
+        thumbnail: dummy_upload
+      )
+
+      expect(response).to have_http_status(:created)
+      expect(Post.find(json.fetch('id')).video_ms).to eq(180_500)
+      expect(json.fetch('video_ms')).to eq(180_500)
+    end
+
+    it 'creates a video post with number input duration seconds' do
+      sign_in_as(member)
+
+      post '/posts', params: post_write_params(
+        title: 'video post seconds',
+        url: 'https://example.com/video-post-seconds',
+        tags: '動画 spec_tag',
+        duration: '180.5',
+        thumbnail: dummy_upload
+      )
+
+      expect(response).to have_http_status(:created)
+      expect(Post.find(json.fetch('id')).video_ms).to eq(180_500)
+      expect(json.fetch('video_ms')).to eq(180_500)
+    end
+
+    it 'clears video_ms when the saved tags do not include 動画' do
+      sign_in_as(member)
+
+      post '/posts', params: post_write_params(
+        title: 'non video post',
+        url: 'https://example.com/non-video-post',
+        tags: 'spec_tag',
+        duration: '3:00',
+        thumbnail: dummy_upload
+      )
+
+      expect(response).to have_http_status(:created)
+      expect(Post.find(json.fetch('id')).video_ms).to be_nil
+    end
+
+    it 'returns validation error when a bounded section exceeds duration' do
+      sign_in_as(member)
+
+      post '/posts', params: post_write_params(
+        title: 'too long section',
+        url: 'https://example.com/too-long-section',
+        tags: '動画 伊地知ニジカ[2:50-3:10]',
+        duration: '3:00',
+        thumbnail: dummy_upload
+      )
+
+      expect(response).to have_http_status(:unprocessable_entity)
+      expect(json.fetch('errors')).to include(
+        'video_ms' => ['タグ区間の終端が動画時間を超えてゐます．']
+      )
+    end
+
+    it 'saves open-ended sections with end_ms NULL' do
+      sign_in_as(member)
+
+      post '/posts', params: post_write_params(
+        title: 'open ended section literal',
+        url: 'https://example.com/open-ended-section-literal',
+        tags: '動画 伊地知ニジカ[1:00-]',
+        duration: '3:00',
+        thumbnail: dummy_upload
+      )
+
+      expect(response).to have_http_status(:created)
+
+      created_post = Post.find(json.fetch('id'))
+      tag = Tag.joins(:tag_name).find_by!(tag_names: { name: '伊地知ニジカ' })
+      section = PostTagSection.find_by!(post: created_post, tag:)
+
+      expect(section.begin_ms).to eq(60_000)
+      expect(section.end_ms).to be_nil
+    end
+
+    it 'does not save sections for [-]' do
+      sign_in_as(member)
+
+      post '/posts', params: post_write_params(
+        title: 'fully open section literal',
+        url: 'https://example.com/fully-open-section-literal',
+        tags: '伊地知ニジカ[-]',
+        thumbnail: dummy_upload
+      )
+
+      expect(response).to have_http_status(:created)
+
+      created_post = Post.find(json.fetch('id'))
+      tag = Tag.joins(:tag_name).find_by!(tag_names: { name: '伊地知ニジカ' })
+      expect(PostTagSection.find_by(post: created_post, tag:)).to be_nil
+    end
+
+    it 'does not save sections for [0:00-]' do
+      sign_in_as(member)
+
+      post '/posts', params: post_write_params(
+        title: 'zero open ended section literal',
+        url: 'https://example.com/zero-open-ended-section-literal',
+        tags: '伊地知ニジカ[0:00-]',
+        thumbnail: dummy_upload
+      )
+
+      expect(response).to have_http_status(:created)
+
+      created_post = Post.find(json.fetch('id'))
+      tag = Tag.joins(:tag_name).find_by!(tag_names: { name: '伊地知ニジカ' })
+      expect(PostTagSection.find_by(post: created_post, tag:)).to be_nil
+    end
+
+    it 'returns end_ms null for open-ended sections in show response' do
+      sign_in_as(member)
+
+      post '/posts', params: post_write_params(
+        title: 'show open ended section literal',
+        url: 'https://example.com/show-open-ended-section-literal',
+        tags: '動画 伊地知ニジカ[1:00-]',
+        duration: '3:00',
+        thumbnail: dummy_upload
+      )
+
+      expect(response).to have_http_status(:created)
+
+      get "/posts/#{ json.fetch('id') }"
+
+      expect(response).to have_http_status(:ok)
+      tag_json = json.fetch('tags').find { |item| item['name'] == '伊地知ニジカ' }
+      expect(tag_json.fetch('sections')).to eq([
+        { 'begin_ms' => 60_000, 'end_ms' => nil }
+      ])
+    end
+
+    it 'allows open-ended sections when begin is within duration' do
+      sign_in_as(member)
+
+      post '/posts', params: post_write_params(
+        title: 'valid open ended section literal',
+        url: 'https://example.com/valid-open-ended-section-literal',
+        tags: '動画 伊地知ニジカ[1:00-]',
+        duration: '3:00',
+        thumbnail: dummy_upload
+      )
+
+      expect(response).to have_http_status(:created)
+    end
+
+    it 'rejects open-ended sections when begin equals duration' do
+      sign_in_as(member)
+
+      post '/posts', params: post_write_params(
+        title: 'invalid open ended section literal',
+        url: 'https://example.com/invalid-open-ended-section-literal',
+        tags: '動画 伊地知ニジカ[3:00-]',
+        duration: '3:00',
+        thumbnail: dummy_upload
+      )
+
+      expect(response).to have_http_status(:unprocessable_entity)
+      expect(json.fetch('errors')).to include(
+        'video_ms' => ['タグ区間の開始が動画時間以上です．']
+      )
+    end
+
     context "when nico tag already exists in tags" do
       before do
         Tag.find_undiscard_or_create_by!(

backend/spec/requests/tag_children_spec.rb

@@ -56,6 +56,17 @@ RSpec.describe "TagChildren", type: :request do
 
         expect(response).to have_http_status(:no_content)
       end
+
+      it 'returns 422 and does not create relation when the new link makes a cycle' do
+        TagImplication.create!(tag: parent, parent_tag: child)
+
+        expect {
+          do_request
+        }.not_to change(TagImplication, :count)
+
+        expect(response).to have_http_status(:unprocessable_entity)
+        expect(TagImplication.where(tag: child, parent_tag: parent)).not_to exist
+      end
     end
 
     context "when Tag.find raises (invalid ids)" do

backend/spec/requests/tags_spec.rb

@@ -581,6 +581,58 @@ RSpec.describe 'Tags API', type: :request do
         expect(response).to have_http_status(:ok)
         expect(wiki_page.reload.wiki_versions.count).to eq(before_wiki_version_count)
       end
+
+      it 'full update で旧名 alias が残った tag を PATCH で旧名へ戻せる' do
+        put "/tags/#{ tag.id }", params: {
+          name: 'patch_roundtrip_target',
+          category: 'general',
+          aliases: 'unko',
+          parent_tags: '',
+          deprecated: '0',
+        }
+
+        expect(response).to have_http_status(:ok)
+        expect(TagName.find_by!(name: 'spec_tag').canonical).to eq(tag.reload.tag_name)
+
+        patch "/tags/#{ tag.id }", params: { name: 'spec_tag' }
+
+        expect(response).to have_http_status(:ok)
+
+        tag.reload
+
+        expect(tag.name).to eq('spec_tag')
+        expect(tag.tag_name.canonical_id).to be_nil
+        expect(TagName.find_by!(name: 'patch_roundtrip_target').canonical).to eq(tag.tag_name)
+      end
+
+      it '別 tag の正規名には変更できない' do
+        wiki_page =
+            Wiki::Commit.create_content!(
+                tag_name: tag.tag_name,
+                body: 'patch collision wiki',
+                created_by_user: member_user,
+                message: 'init')
+
+        patch "/tags/#{ tag.id }", params: { name: 'unknown' }
+
+        expect(response).to have_http_status(:unprocessable_entity)
+        expect(json.fetch('errors')).to include(
+          'name' => ['その名前は既に使はれてゐます．']
+        )
+
+        expect(tag.reload.name).to eq('spec_tag')
+        expect(tag.tag_name.aliases.map(&:name)).to contain_exactly('unko')
+        expect(wiki_page.reload.tag_name).to eq(tag.tag_name)
+      end
+
+      it 'system tag の name は変更できない' do
+        system_tag = Tag.bot
+
+        patch "/tags/#{ system_tag.id }", params: { name: 'patch_system_tag_renamed' }
+
+        expect(response).to have_http_status(:unprocessable_entity)
+        expect(system_tag.reload.name).to eq('bot操作')
+      end
     end
   end
 
@@ -745,7 +797,17 @@ RSpec.describe 'Tags API', type: :request do
       )
       TagImplication.create!(tag: first, parent_tag: root_material)
       TagImplication.create!(tag: second, parent_tag: first)
-      TagImplication.create!(tag: first, parent_tag: second)
+      now = Time.current
+      TagImplication.insert_all!(
+        [
+          {
+            tag_id: first.id,
+            parent_tag_id: second.id,
+            created_at: now,
+            updated_at: now
+          }
+        ]
+      )
 
       get '/tags/with-depth', params: { parent: root_material.id }
 
@@ -1029,6 +1091,42 @@ RSpec.describe 'Tags API', type: :request do
         expect(versions.second.created_by_user_id).to eq(member_user.id)
       end
 
+      it '同じ tag の旧 alias へ戻しても rename できる' do
+        put "/tags/#{ tag.id }", params: {
+          name: 'put_roundtrip_b',
+          category: 'general',
+          aliases: 'unko',
+          parent_tags: '',
+          deprecated: '0',
+        }
+
+        expect(response).to have_http_status(:ok)
+
+        put "/tags/#{ tag.id }", params: {
+          name: 'spec_tag',
+          category: 'general',
+          aliases: 'unko',
+          parent_tags: '',
+          deprecated: '0',
+        }
+
+        expect(response).to have_http_status(:ok)
+
+        tag.reload
+
+        expect(tag.name).to eq('spec_tag')
+        expect(TagName.find_by!(name: 'put_roundtrip_b').canonical).to eq(tag.tag_name)
+        expect(tag.tag_name.aliases.map(&:name)).to contain_exactly('put_roundtrip_b', 'unko')
+        expect(tag.tag_name.aliases.map(&:name)).not_to include('spec_tag')
+        expect(alias_tn.reload.canonical).to eq(tag.tag_name)
+
+        version = tag.tag_versions.order(:version_no).last
+
+        expect(version.event_type).to eq('update')
+        expect(version.name).to eq('spec_tag')
+        expect(version.aliases.split).to contain_exactly('put_roundtrip_b', 'unko')
+      end
+
       it 'parent tag の snapshot も作成する' do
         old_parent = Tag.create!(
           tag_name: TagName.create!(name: 'put_snapshot_old_parent'),
@@ -1153,6 +1251,48 @@ RSpec.describe 'Tags API', type: :request do
         )
       end
 
+      it 'wiki を持つ tag を旧 alias へ戻しても wiki を新 canonical へ移す' do
+        wiki_page =
+            Wiki::Commit.create_content!(
+                tag_name: tag.tag_name,
+                body: 'wiki body before',
+                created_by_user: member_user,
+                message: 'init')
+
+        expect {
+          put "/tags/#{ tag.id }", params: {
+            name: 'put_wiki_roundtrip_b',
+            category: 'general',
+            aliases: 'unko',
+            parent_tags: '',
+            deprecated: '0',
+          }
+
+          put "/tags/#{ tag.id }", params: {
+            name: 'spec_tag',
+            category: 'general',
+            aliases: 'unko',
+            parent_tags: '',
+            deprecated: '0',
+          }
+        }
+            .to change(TagVersion, :count).by(3)
+            .and change(WikiVersion, :count).by(2)
+
+        expect(response).to have_http_status(:ok)
+
+        tag.reload
+
+        expect(wiki_page.reload.tag_name).to eq(tag.tag_name)
+        expect(TagName.find_by!(name: 'put_wiki_roundtrip_b').wiki_page).to be_nil
+        expect(TagName.find_by!(name: 'put_wiki_roundtrip_b').canonical).to eq(tag.tag_name)
+
+        versions = wiki_page.wiki_versions.order(:version_no).last(2)
+
+        expect(versions.map(&:event_type)).to eq(['update', 'update'])
+        expect(versions.map(&:title)).to eq(['put_wiki_roundtrip_b', 'spec_tag'])
+      end
+
       it '別名を他 tag から奪った場合、奪はれた側の tag version も作成する' do
         old_owner = Tag.create!(
           tag_name: TagName.create!(name: 'put_alias_old_owner'),
@@ -1191,9 +1331,49 @@ RSpec.describe 'Tags API', type: :request do
         expect(old_owner_versions.second.aliases.split).not_to include('put_stolen_alias')
       end
 
-      it 'parent_tags に指定すると循環する tag は 422 にする' do
-        pending '#332 で対応予定'
+      it '別 tag の alias 名を rename で奪へる' do
+        old_owner = Tag.create!(
+          tag_name: TagName.create!(name: 'put_alias_collision_owner'),
+          category: :general
+        )
+        stolen_alias = TagName.create!(
+          name: 'put_alias_collision_name',
+          canonical: old_owner.tag_name
+        )
+        wiki_page =
+            Wiki::Commit.create_content!(
+                tag_name: tag.tag_name,
+                body: 'put collision wiki',
+                created_by_user: member_user,
+                message: 'init')
 
+        put "/tags/#{ tag.id }", params: {
+          name: 'put_alias_collision_name',
+          category: 'general',
+          aliases: 'unko',
+          parent_tags: '',
+          deprecated: '0',
+        }
+
+        expect(response).to have_http_status(:ok)
+
+        tag.reload
+        old_owner.reload
+        stolen_alias.reload
+
+        expect(tag.name).to eq('put_alias_collision_name')
+        expect(stolen_alias.canonical_id).to be_nil
+        expect(TagName.find_by!(name: 'spec_tag').canonical).to eq(tag.tag_name)
+        expect(old_owner.tag_name.aliases.map(&:name)).not_to include('put_alias_collision_name')
+
+        old_owner_versions = old_owner.tag_versions.order(:version_no)
+
+        expect(old_owner_versions.last.event_type).to eq('update')
+        expect(old_owner_versions.last.aliases.split).not_to include('put_alias_collision_name')
+        expect(wiki_page.reload.tag_name).to eq(tag.tag_name)
+      end
+
+      it 'parent_tags に指定すると循環する tag は 422 にする' do
         child = Tag.create!(
           tag_name: TagName.create!(name: 'put_cycle_child'),
           category: :general

backend/spec/services/material_file_sha256_spec.rb

@@ -0,0 +1,23 @@
+require 'rails_helper'
+
+RSpec.describe MaterialFileSha256 do
+  describe '.metadata_sha256' do
+    it 'reads sha256 from Hash metadata' do
+      blob = instance_double(ActiveStorage::Blob, metadata: { 'sha256' => 'abc123' })
+
+      expect(described_class.metadata_sha256(blob)).to eq('abc123')
+    end
+
+    it 'reads sha256 from JSON string metadata' do
+      blob = instance_double(ActiveStorage::Blob, metadata: '{"sha256":"abc123"}')
+
+      expect(described_class.metadata_sha256(blob)).to eq('abc123')
+    end
+
+    it 'returns nil for invalid metadata' do
+      blob = instance_double(ActiveStorage::Blob, metadata: '{')
+
+      expect(described_class.metadata_sha256(blob)).to be_nil
+    end
+  end
+end

backend/spec/services/material_sync_importer_spec.rb

@@ -0,0 +1,128 @@
+require 'rails_helper'
+
+RSpec.describe MaterialSyncImporter do
+  let(:user) { create(:user, :member) }
+  let(:tag) { Tag.create!(tag_name: TagName.create!(name: 'sync_tag'), category: :material) }
+
+  def tempfile_for body
+    Tempfile.new(['material-sync-importer', '.png']).tap do |file|
+      file.binmode
+      file.write(body)
+      file.rewind
+    end
+  end
+
+  it 'creates an untagged material from a sync candidate with file_downloader' do
+    result =
+        described_class.import!(
+            source_kind: 'google_drive_file',
+            source_path: '素材/a.png',
+            source_file_id: 'drive-file-a',
+            normalized_source_key: 'google_drive_file:drive-file-a',
+            filename: 'a.png',
+            content_type: 'image/png',
+            file_sha256: Digest::SHA256.hexdigest('sync-body'),
+            file_downloader: -> { tempfile_for('sync-body') },
+            export_path: '素材/a.png',
+            tag: nil,
+            url: nil,
+            created_by_user: user,
+            updated_by_user: user)
+
+    material = result.material.reload
+    expect(result.action).to eq(:imported)
+    expect(material.tag).to be_nil
+    expect(material.url).to be_nil
+    expect(material.file).to be_attached
+    expect(material.file.blob.filename.to_s).to eq('a.png')
+    expect(material.material_export_items.first.export_path).to eq('素材/a.png')
+  end
+
+  it 'does not clear a human-assigned tag or URL on existing Drive sync' do
+    material =
+        Material.create!(tag:, url: 'https://example.com/human',
+                         source_kind: 'google_drive_file',
+                         source_path: '素材/a.png',
+                         source_file_id: 'drive-file-a',
+                         created_by_user: user,
+                         updated_by_user: user)
+    material.file.attach(
+        io: StringIO.new('same-body'),
+        filename: 'a.png',
+        content_type: 'image/png')
+    material.file.blob.metadata['sha256'] = Digest::SHA256.hexdigest('same-body')
+    material.file.blob.save!
+    MaterialExportItem.create!(material:,
+                               profile: 'legacy_drive',
+                               export_path: '素材/a.png',
+                               created_by_user: user)
+
+    result =
+        described_class.import!(
+            source_kind: 'google_drive_file',
+            source_path: '素材/a.png',
+            source_file_id: 'drive-file-a',
+            filename: 'a.png',
+            content_type: 'image/png',
+            file_sha256: Digest::SHA256.hexdigest('same-body'),
+            export_path: '素材/a.png',
+            tag: nil,
+            url: nil,
+            updated_by_user: user)
+
+    expect(result.action).to eq(:unchanged)
+    expect(material.reload.tag).to eq(tag)
+    expect(material.url).to eq('https://example.com/human')
+  end
+
+  it 'suppresses a Google Drive candidate by relative path prefix' do
+    MaterialSyncSuppression.create!(source_kind: 'google_drive_path_prefix',
+                                    drive_path: '素材/危険',
+                                    reason: 'copyright_high_risk',
+                                    created_by_user: user)
+
+    result =
+        described_class.import!(
+            source_kind: 'google_drive_file',
+            source_path: '素材/危険/a.png',
+            source_file_id: 'drive-file-b',
+            filename: 'a.png',
+            content_type: 'image/png',
+            file_sha256: Digest::SHA256.hexdigest('blocked-body'),
+            file_downloader: -> { tempfile_for('blocked-body') },
+            export_path: '素材/危険/a.png',
+            updated_by_user: user)
+
+    expect(result.action).to eq(:suppressed)
+    expect(result.suppression.normalized_source_key)
+      .to eq('google_drive_path_prefix:素材/危険')
+    expect(Material.find_by(source_file_id: 'drive-file-b')).to be_nil
+  end
+
+  it 'rechecks import blocks after downloaded file sha256 is known' do
+    MaterialImportBlock.create!(match_kind: 'sha256',
+                                sha256: Digest::SHA256.hexdigest('blocked-body'),
+                                reason: 'copyright_high_risk',
+                                created_by_user: user)
+    blob_count = ActiveStorage::Blob.count
+
+    expect do
+      result =
+          described_class.import!(
+              source_kind: 'google_drive_file',
+              source_path: '素材/blocked.png',
+              source_file_id: 'drive-file-blocked',
+              filename: 'blocked.png',
+              content_type: 'image/png',
+              file_downloader: -> { tempfile_for('blocked-body') },
+              export_path: '素材/blocked.png',
+              updated_by_user: user)
+
+      expect(result.action).to eq(:suppressed)
+      expect(result.suppression.reason).to eq('copyright_high_risk')
+    end.not_to change(Material, :count)
+
+    expect(ActiveStorage::Blob.count).to eq(blob_count)
+    expect(Material.find_by(source_file_id: 'drive-file-blocked')).to be_nil
+  end
+end

backend/spec/services/material_sync_runner_spec.rb

@@ -0,0 +1,89 @@
+require 'rails_helper'
+
+RSpec.describe MaterialSyncRunner do
+  let(:user) { create(:user, :member) }
+  let(:source) do
+    MaterialSyncSource.create!(
+        name: 'Drive source',
+        source_kind: 'google_drive_path',
+        source_file_id: 'folder-123',
+        profile: 'legacy_drive',
+        created_by_user: user,
+        updated_by_user: user)
+  end
+  let(:drive_client) { instance_double(GoogleDrive::ApiClient) }
+
+  describe '#sync!' do
+    it 'imports google drive path candidates as they are yielded' do
+      first_entry = { id: 'file-1',
+                      name: 'a.png',
+                      mime_type: 'image/png',
+                      relative_path: '素材/a.png',
+                      sha256_checksum: 'sha-a',
+                      web_view_link: 'https://drive.google.com/file/d/file-1/view',
+                      web_content_link: nil }
+      second_entry = { id: 'file-2',
+                       name: 'b.png',
+                       mime_type: 'image/png',
+                       relative_path: '素材/b.png',
+                       sha256_checksum: 'sha-b',
+                       web_view_link: 'https://drive.google.com/file/d/file-2/view',
+                       web_content_link: nil }
+      yielded = []
+
+      allow(GoogleDrive::ApiClient).to receive(:new).and_return(drive_client)
+      allow(drive_client).to receive(:each_material_file_under_folder) do |folder_id, &block|
+        expect(folder_id).to eq('folder-123')
+        block.call(first_entry)
+        expect(yielded).to eq(['素材/a.png'])
+        block.call(second_entry)
+      end
+      allow(MaterialSyncImporter).to receive(:import!) do |candidate|
+        yielded << candidate.fetch(:source_path)
+        instance_double(MaterialSyncImporter::Result,
+                        action: yielded.last == '素材/a.png' ? :imported : :updated)
+      end
+
+      result = described_class.new(source).sync!
+
+      expect(yielded).to eq(['素材/a.png', '素材/b.png'])
+      expect(result.imported).to eq(1)
+      expect(result.updated).to eq(1)
+      expect(result.unchanged).to eq(0)
+      expect(source.reload.last_synced_at).to be_present
+    end
+
+    it 'logs google drive path progress at first item and summary' do
+      entry = { id: 'file-1',
+                name: 'a.png',
+                mime_type: 'image/png',
+                relative_path: '素材/a.png',
+                sha256_checksum: 'sha-a',
+                web_view_link: 'https://drive.google.com/file/d/file-1/view',
+                web_content_link: nil }
+      logged = []
+
+      allow(GoogleDrive::ApiClient).to receive(:new).and_return(drive_client)
+      allow(drive_client).to receive(:each_material_file_under_folder) do |_folder_id, &block|
+        block.call(entry)
+      end
+      allow(MaterialSyncImporter).to receive(:import!)
+        .and_return(instance_double(MaterialSyncImporter::Result, action: :imported))
+      allow(Rails.logger).to receive(:info) { |message| logged << JSON.parse(message) }
+
+      described_class.new(source).sync!
+
+      progress_logs = logged.select { |row| row['folder_id'] == 'folder-123' }
+      expect(progress_logs.map { |row| row['progress'] }).to eq(['scan', 'summary'])
+      expect(progress_logs.last).to include(
+          'material_sync_source_id' => source.id,
+          'material_sync_source_name' => 'Drive source',
+          'scanned_count' => 1,
+          'imported' => 1,
+          'updated' => 0,
+          'unchanged' => 0,
+          'suppressed' => 0,
+          'failed' => 0)
+    end
+  end
+end

docs/commands.md

@@ -10,6 +10,15 @@ bundle exec rspec
 bundle exec rails routes
 ```
 
+Material video thumbnail generation requires `ffmpeg` on the host. If `ffmpeg`
+is missing or frame extraction fails, `MaterialThumbnailGenerator` logs the
+result and stderr, then leaves the existing thumbnail unchanged.
+
+```sh
+cd backend
+bundle exec rails materials:thumbnails:backfill
+```
+
 ## Frontend
 
 ```sh

frontend/src/App.tsx

@@ -6,6 +6,7 @@ import { BrowserRouter,
 	 Routes,
 	 useLocation } from 'react-router-dom'
 
+import DevModeWatermark from '@/components/DevModeWatermark'
 import RouteBlockerOverlay from '@/components/RouteBlockerOverlay'
 import TopNav from '@/components/TopNav'
 import DialogueProvider from '@/components/dialogues/DialogueProvider'
@@ -14,8 +15,10 @@ import { apiPost, isApiError } from '@/lib/api'
 import DeerjikistDetailPage from '@/pages/deerjikists/DeerjikistDetailPage'
 import MaterialBasePage from '@/pages/materials/MaterialBasePage'
 import MaterialDetailPage from '@/pages/materials/MaterialDetailPage'
+import MaterialHistoryPage from '@/pages/materials/MaterialHistoryPage'
 import MaterialListPage from '@/pages/materials/MaterialListPage'
 import MaterialNewPage from '@/pages/materials/MaterialNewPage'
+import MaterialSyncSuppressionsPage from '@/pages/materials/MaterialSyncSuppressionsPage'
 // import MaterialSearchPage from '@/pages/materials/MaterialSearchPage'
 import MorePage from '@/pages/MorePage'
 import GekanatorPage from '@/pages/GekanatorPage'
@@ -68,10 +71,11 @@ const RouteTransitionWrapper = ({ user, setUser }: {
 	  <Route path="/theatres/:id" element={<TheatreDetailPage user={user}/>}/>
 	  <Route path="/materials" element={<MaterialBasePage/>}>
 	    <Route index element={<MaterialListPage/>}/>
+	    <Route path="changes" element={<MaterialHistoryPage/>}/>
 	    <Route path="new" element={<MaterialNewPage/>}/>
-	    <Route path=":id" element ={<MaterialDetailPage user={user}/>}/>
+	    <Route path="suppressions" element={<MaterialSyncSuppressionsPage/>}/>
+	    <Route path=":id" element ={<MaterialDetailPage/>}/>
 	  </Route>
-	  {/* <Route path="/materials/search" element={<MaterialSearchPage/>}/> */}
 	  <Route path="/wiki" element={<WikiSearchPage/>}/>
 	  <Route path="/wiki/:title" element={<WikiDetailPage/>}/>
 	  <Route path="/wiki/new" element={<WikiNewPage user={user}/>}/>
@@ -142,6 +146,7 @@ const App: FC = () => {
   return (
       <>
 	<RouteBlockerOverlay/>
+	{import.meta.env.DEV && <DevModeWatermark/>}
 
 	<BrowserRouter>
 	  <DialogueProvider>
@@ -149,7 +154,7 @@ const App: FC = () => {
 	      <motion.div
 		  layout="position"
 		  transition={{ layout: { duration: .2, ease: 'easeOut' } }}
-		  className="flex flex-col h-dvh w-full overflow-y-hidden">
+		  className="relative flex flex-col h-dvh w-full overflow-y-hidden">
 		<TopNav user={user}/>
 		<RouteTransitionWrapper user={user} setUser={setUser}/>
 	      </motion.div>

frontend/src/components/DevModeWatermark.tsx

@@ -0,0 +1,46 @@
+import nikumaru from '@/assets/fonts/nikumaru.otf'
+
+import type { FC } from 'react'
+
+
+const ROW_COUNT = 8
+const COLUMN_COUNT = 12
+
+
+const DevModeWatermark: FC = () => {
+  return (
+      <div
+	  aria-hidden="true"
+	  className="pointer-events-none select-none fixed inset-0 overflow-hidden z-0">
+	<style>{`
+	  @font-face {
+	    font-family: 'Nikumaru';
+	    src: url(${nikumaru}) format('opentype');
+	  }
+	`}</style>
+	<div className="absolute -inset-32 flex flex-col justify-center gap-12 py-48">
+	  {Array.from ({ length: ROW_COUNT }, (_, rowIndex) => (
+	      <div
+		  key={rowIndex}
+		  className={
+		      'flex min-h-32 items-center gap-12 '
+		      + (rowIndex % 2 === 0 ? 'translate-x-0' : 'translate-x-32')
+		  }>
+		{Array.from ({ length: COLUMN_COUNT }, (_, columnIndex) => (
+		    <span
+			key={columnIndex}
+			className={
+			    'whitespace-nowrap text-3xl font-bold '
+			    + 'tracking-[0.3em] text-neutral-950/5 '
+			    + 'dark:text-white/10'
+			}
+			style={{ fontFamily: 'Nikumaru' }}>
+		      開発モード
+		    </span>))}
+	      </div>))}
+	</div>
+      </div>)
+}
+
+
+export default DevModeWatermark

frontend/src/components/DraggableDroppableTagRow.tsx

@@ -87,10 +87,13 @@ const DraggableDroppableTagRow: FC<Props> = ({ tag, nestLevel, pathKey, parentTa
 	    setDropRef (node)
 	  }}
 	  style={style}
-	  className={cn ('rounded select-none', over && 'ring-2 ring-offset-2')}
+	  className={cn (
+	      'min-w-0 max-w-full overflow-hidden rounded select-none',
+	      over && 'ring-2 ring-offset-2')}
 	  {...attributes}
 	  {...listeners}>
 	<motion.div
+	    className="flex min-w-0 max-w-full items-baseline overflow-hidden"
 	    transition={{ layout: { duration: .2, ease: 'easeOut' } }}
 	    layoutId={`tag-${ sp ? 'sp-' : '' }${ tag.id }`}>
 	  <TagLink tag={tag} nestLevel={nestLevel}/>
@@ -98,4 +101,4 @@ const DraggableDroppableTagRow: FC<Props> = ({ tag, nestLevel, pathKey, parentTa
       </div>)
 }
 
-export default DraggableDroppableTagRow
+export default DraggableDroppableTagRow

frontend/src/components/MaterialSidebar.tsx

@@ -1,23 +1,43 @@
-import { Fragment, useEffect, useState } from 'react'
+import { useQuery } from '@tanstack/react-query'
+import { useEffect, useRef, useState } from 'react'
+import { useLocation, useNavigate } from 'react-router-dom'
 
-import TagLink from '@/components/TagLink'
 import SidebarComponent from '@/components/layout/SidebarComponent'
-import { apiGet } from '@/lib/api'
+import TagLink from '@/components/TagLink'
+import { fetchMaterialTagTree, parseMaterialFilter } from '@/lib/materials'
+import { materialsKeys } from '@/lib/queryKeys'
+import { cn } from '@/lib/utils'
 
-import type { FC, ReactNode } from 'react'
+import type { CSSProperties, Dispatch, FC, ReactNode, SetStateAction } from 'react'
 
-import type { Tag } from '@/types'
+import type { MaterialFilter, MaterialSidebarTag, Tag } from '@/types'
 
-type TagWithDepth = Tag & {
-    hasChildren:  boolean
-    children:     TagWithDepth[] }
+const FILTERS: MaterialFilter[] = ['missing', 'present', 'any']
+const FILTER_LABELS: Record<MaterialFilter, string> = { present: '有', missing: '無', any: '全' }
+
+
+const px = (value: string): number => {
+  const parsed = Number.parseFloat (value)
+  return Number.isFinite (parsed) ? parsed : 0
+}
+
+
+const verticalChrome = (el: HTMLElement): number => {
+  const style = window.getComputedStyle (el)
+
+  return (
+      px (style.paddingTop)
+      + px (style.paddingBottom)
+      + px (style.borderTopWidth)
+      + px (style.borderBottomWidth))
+}
 
 
 const setChildrenById = (
-    tags:     TagWithDepth[],
+    tags:     MaterialSidebarTag[],
     targetId: number,
-    children: TagWithDepth[],
-): TagWithDepth[] => (
+    children: MaterialSidebarTag[],
+): MaterialSidebarTag[] => (
     tags.map (tag => {
       if (tag.id === targetId)
 	return { ...tag, children }
@@ -25,75 +45,468 @@ const setChildrenById = (
       if (tag.children.length === 0)
 	return tag
 
-      return { ...tag,
-	       children: (setChildrenById (tag.children, targetId, children)
-			  .filter (t => t.category !== 'meme' || t.hasChildren)) }
+      return { ...tag, children: setChildrenById (tag.children, targetId, children) }
     }))
 
 
-const MaterialSidebar: FC = () => {
-  const [tags, setTags] = useState<TagWithDepth[]> ([])
-  const [openTags, setOpenTags] = useState<Record<number, boolean>> ({ })
-  const [tagFetchedFlags, setTagFetchedFlags] = useState<Record<number, boolean>> ({ })
+const materialPath = (
+    tagId: number,
+    materialFilter: MaterialFilter,
+): string =>
+    `/materials?tag_id=${ tagId }&include_descendants=1&group_by=parent_tag`
+    + `&material_filter=${ materialFilter }`
 
-  useEffect (() => {
-    void (async () => {
-      setTags ((await apiGet<TagWithDepth[]> ('/tags/with-depth'))
-	       .filter (t => t.category !== 'meme' || t.hasChildren))
-    }) ()
-  }, [])
 
-  const renderTags = (ts: TagWithDepth[], nestLevel = 0): ReactNode => (
-      ts.map (t => (
-	  <Fragment key={t.id}>
-	    <li>
-	      <div className="flex">
-		<div className="flex-none w-4">
-		  {t.hasChildren && (
-		      <a
-			  href="#"
-			  onClick={async e => {
-			    e.preventDefault ()
-			    if (!(tagFetchedFlags[t.id]))
-			      {
-				try
-				{
-				  const data =
-				      await apiGet<TagWithDepth[]> (
-					  '/tags/with-depth', { params: { parent: String (t.id) } })
-				  setTags (prev => setChildrenById (prev, t.id, data))
-				  setTagFetchedFlags (prev => ({ ...prev, [t.id]: true }))
-				}
-				catch
-				{
-				  ;
-				}
-			      }
-			    setOpenTags (prev => ({ ...prev, [t.id]: !(prev[t.id]) }))
-			  }}>
-			{openTags[t.id] ? <>&minus;</> : '+'}
-		      </a>)}
-		</div>
-		<div className="flex-1 truncate">
-		  <TagLink
-		      tag={t}
-		      nestLevel={nestLevel}
-		      title={t.name}
-		      withCount={false}
-		      withWiki={false}
-		      to={`/materials?tag=${ encodeURIComponent (t.name) }`}/>
-		</div>
-	      </div>
-	    </li>
-	    {openTags[t.id] && renderTags (t.children, nestLevel + 1)}
-	  </Fragment>)))
+const sidebarTagToTag = (tag: MaterialSidebarTag): Tag => ({
+    id:             tag.id,
+    name:           tag.name,
+    category:       tag.category,
+    deprecatedAt:   tag.deprecated ? '' : null,
+    aliases:        [],
+    parents:        [],
+    postCount:      0,
+    createdAt:      '',
+    updatedAt:      '',
+    hasWiki:        false,
+    materialId:     null,
+    hasDeerjikists: false,
+    matchedAlias:   null })
 
-  return (
-      <SidebarComponent>
-	<ul>
-	  {renderTags (tags)}
-	</ul>
-      </SidebarComponent>)
+
+const tagSelectionShellClass = (selected: boolean): string =>
+    cn (selected
+	? ['rounded-md border border-sky-500 bg-sky-50 px-2 py-1 text-sky-700',
+	   'dark:border-sky-400 dark:bg-sky-950 dark:text-sky-100']
+	: 'px-2 py-1')
+
+
+const updateMaterialFilterQuery = (
+    pathname: string,
+    locationSearch: string,
+    navigate: ReturnType<typeof useNavigate>,
+    materialFilter: MaterialFilter,
+) => {
+  const qs = new URLSearchParams (locationSearch)
+  qs.set ('material_filter', materialFilter)
+  navigate (`${ pathname }${ qs.toString () ? `?${ qs.toString () }` : '' }`)
 }
 
-export default MaterialSidebar
+
+const MaterialFilterButtons: FC<{ materialFilter: MaterialFilter
+				  onChange:       (materialFilter: MaterialFilter) => void }> = (
+    { materialFilter, onChange },
+) => (
+    <div className="flex flex-wrap gap-2 justify-end md:justify-start flex-center">
+      <label className="my-auto text-sm font-bold">素材：</label>
+      {FILTERS.map (value => (
+	  <button
+	      key={value}
+	      type="button"
+	      onClick={() => onChange (value)}
+	      className={cn (
+		  'rounded-full border px-3 py-1 text-sm',
+		  (materialFilter === value
+		   ? ['border-sky-500 bg-sky-50 text-sky-700 dark:border-sky-400',
+		      'dark:bg-sky-950 dark:text-sky-100']
+		   : ['border-neutral-300 bg-white text-neutral-700 dark:border-stone-700',
+		      'dark:bg-stone-900 dark:text-stone-200']))}>
+	    {FILTER_LABELS[value]}
+	  </button>))}
+    </div>)
+
+
+const MaterialTreeNode: FC<{
+    materialFilter: MaterialFilter
+    selectedTagId:  number | null
+    nestLevel?:     number
+    onChildren:     (tagId: number, children: MaterialSidebarTag[]) => void
+    openTags:       Record<number, boolean>
+    setOpenTags:    Dispatch<SetStateAction<Record<number, boolean>>>
+    tag:            MaterialSidebarTag
+}> = ({ materialFilter, nestLevel = 0, onChildren, openTags, selectedTagId,
+	 setOpenTags, tag }) => {
+  const open = Boolean (openTags[tag.id])
+  const { data } = useQuery ({
+      queryKey: materialsKeys.tree ({ parentId: tag.id, materialFilter }),
+      queryFn:	() => fetchMaterialTagTree ({ parentId: tag.id, materialFilter }),
+      enabled:	open && tag.hasChildren && tag.children.length === 0})
+
+  useEffect (() => {
+    if (open && data && tag.children.length === 0)
+      onChildren (tag.id, data)
+  }, [data, onChildren, open, tag.children.length, tag.id])
+
+  return (
+      <>
+	<li>
+	  <div className="flex flex-center">
+	    <div className="flex-none w-4 my-auto">
+	      {tag.hasChildren && (
+		  <button
+		      type="button"
+		      onClick={() => setOpenTags (prev => ({ ...prev, [tag.id]: !prev[tag.id] }))}
+		      className="text-neutral-500 dark:text-stone-400">
+		    {open ? <>&minus;</> : '+'}
+		  </button>)}
+	    </div>
+	    <div className="min-w-0 flex-1 my-auto">
+	      <div className={cn (tagSelectionShellClass (selectedTagId === tag.id),
+				  'min-w-0 truncate')}>
+		<TagLink
+		    tag={sidebarTagToTag (tag)}
+		    nestLevel={nestLevel}
+		    title={tag.name}
+		    withCount={false}
+		    withWiki={false}
+		    to={materialPath (tag.id, materialFilter)}/>
+	      </div>
+	    </div>
+	  </div>
+	</li>
+	{open && tag.children.length > 0 && (
+	    <ul>
+	      {tag.children.map (child => (
+		  <MaterialTreeNode
+		      key={child.id}
+		      tag={child}
+		      nestLevel={nestLevel + 1}
+		      materialFilter={materialFilter}
+		      selectedTagId={selectedTagId}
+		      openTags={openTags}
+		      setOpenTags={setOpenTags}
+		      onChildren={onChildren}/>))}
+	    </ul>)}
+      </>)
+}
+
+
+const MobileMaterialTreeNode: FC<{ depth?: number
+				   availableInlineSizePx?: number | null
+				   materialFilter: MaterialFilter
+				   selectedTagId: number | null
+				   onChildren: (tagId: number, children: MaterialSidebarTag[]) =>
+						   void
+				   openTags: Record<number, boolean>
+				   setOpenTags: Dispatch<SetStateAction<Record<number, boolean>>>
+				   tag: MaterialSidebarTag }> = (
+    {
+      depth = 0,
+      availableInlineSizePx = null,
+      materialFilter,
+      onChildren,
+      openTags,
+      selectedTagId,
+      setOpenTags,
+      tag,
+    },
+) => {
+  const open = Boolean (openTags[tag.id])
+  const tagColumnRef = useRef<HTMLDivElement | null> (null)
+  const chipRef = useRef<HTMLDivElement | null> (null)
+  const buttonRef = useRef<HTMLButtonElement | null> (null)
+  const expansionSlotRef = useRef<HTMLDivElement | null> (null)
+  const expansionBorderRef = useRef<HTMLDivElement | null> (null)
+  const [tagChipInlineSizePx, setTagChipInlineSizePx] = useState<number | null> (null)
+  const [tagLinkInlineSizePx, setTagLinkInlineSizePx] = useState<number | null> (null)
+  const [childAvailableInlineSizePx, setChildAvailableInlineSizePx] = useState<number | null> (null)
+  const { data } = useQuery ({
+      queryKey: materialsKeys.tree ({ parentId: tag.id, materialFilter }),
+      queryFn:  () => fetchMaterialTagTree ({ parentId: tag.id, materialFilter }),
+      enabled:  open && tag.hasChildren && tag.children.length === 0})
+
+  useEffect (() => {
+    if (open && data && tag.children.length === 0)
+      onChildren (tag.id, data)
+  }, [data, onChildren, open, tag.children.length, tag.id])
+
+  useEffect (() => {
+    const tagColumn = tagColumnRef.current
+    const chip = chipRef.current
+    if (!(tagColumn) || !(chip))
+      return
+
+    const updateTagInlineSize = () => {
+      const buttonHeight = buttonRef.current?.offsetHeight ?? 0
+      const gap = tag.hasChildren ? px (window.getComputedStyle (tagColumn).rowGap) : 0
+      const columnHeight =
+	  availableInlineSizePx == null
+	  ? tagColumn.clientHeight
+	  : Math.min (tagColumn.clientHeight, availableInlineSizePx)
+      const nextChipInlineSize = Math.max (24, columnHeight - buttonHeight - gap)
+      const nextLinkInlineSize = Math.max (
+	  16,
+	  nextChipInlineSize - verticalChrome (chip),
+      )
+
+      setTagChipInlineSizePx (prev => prev === nextChipInlineSize ? prev : nextChipInlineSize)
+      setTagLinkInlineSizePx (prev => prev === nextLinkInlineSize ? prev : nextLinkInlineSize)
+    }
+
+    updateTagInlineSize ()
+
+    const resizeObserver = new ResizeObserver (() => {
+      updateTagInlineSize ()
+    })
+
+    resizeObserver.observe (tagColumn)
+    resizeObserver.observe (chip)
+
+    if (buttonRef.current)
+      resizeObserver.observe (buttonRef.current)
+
+    return () => {
+      resizeObserver.disconnect ()
+    }
+  }, [availableInlineSizePx, open, tag.hasChildren, tag.children.length])
+
+  useEffect (() => {
+    const expansionSlot = expansionSlotRef.current
+    const expansionBorder = expansionBorderRef.current
+    if (!(expansionSlot) || !(expansionBorder))
+      return
+
+    const updateChildInlineSize = () => {
+      const base =
+	  availableInlineSizePx == null
+	  ? expansionSlot.clientHeight
+	  : availableInlineSizePx
+      const chrome = verticalChrome (expansionSlot) + verticalChrome (expansionBorder)
+      const nextInlineSize = Math.max (24, base - chrome)
+      setChildAvailableInlineSizePx (prev => prev === nextInlineSize ? prev : nextInlineSize)
+    }
+
+    updateChildInlineSize ()
+
+    const resizeObserver = new ResizeObserver (() => {
+      updateChildInlineSize ()
+    })
+
+    resizeObserver.observe (expansionSlot)
+    resizeObserver.observe (expansionBorder)
+
+    return () => {
+      resizeObserver.disconnect ()
+    }
+  }, [availableInlineSizePx, open, tag.children.length])
+
+  return (
+      <div className="flex h-full min-h-0 max-h-full flex-row-reverse items-start gap-2
+		      overflow-hidden">
+	<div
+	    ref={tagColumnRef}
+	    className="flex h-full min-h-0 max-h-full flex-col items-center gap-1
+		       overflow-hidden">
+	  <div
+	      ref={chipRef}
+	      className={cn (
+		  tagSelectionShellClass (selectedTagId === tag.id),
+		  'box-border rounded-xl border px-3 py-2 text-sm shadow-sm',
+		  'min-h-0 overflow-hidden [max-inline-size:var(--tag-chip-inline-size)]',
+		  '[max-height:var(--tag-chip-inline-size)]',
+	      )}
+	      style={{
+		writingMode: 'vertical-rl',
+		'--tag-chip-inline-size': (
+		    tagChipInlineSizePx == null
+		    ? undefined
+		    : `${ tagChipInlineSizePx }px`),
+		'--tag-link-inline-size': (
+		    tagLinkInlineSizePx == null
+		    ? undefined
+		    : `${ tagLinkInlineSizePx }px`),
+	      } as CSSProperties}>
+	    <TagLink
+		tag={sidebarTagToTag (tag)}
+		title={tag.name}
+		truncateOnMobile
+		withCount={false}
+		withWiki={false}
+		to={materialPath (tag.id, materialFilter)}
+		className="block overflow-hidden text-ellipsis whitespace-nowrap
+			   [max-inline-size:var(--tag-link-inline-size)]
+			   [max-height:var(--tag-link-inline-size)]
+			   [&_.tag-marquee]:block
+			   [&_.tag-marquee]:h-full
+			   [&_.tag-marquee]:overflow-hidden
+			   [&_.tag-marquee__static]:h-full
+			   [&_.tag-marquee__static]:overflow-hidden
+			   [&_.tag-marquee__static]:text-ellipsis
+			   [&_.tag-marquee__static]:[text-overflow:ellipsis]"/>
+	  </div>
+	  {tag.hasChildren && (
+	      <button
+		  ref={buttonRef}
+		  type="button"
+		  onClick={() => setOpenTags (prev => ({ ...prev, [tag.id]: !prev[tag.id] }))}
+		  className="flex-none rounded-full border border-stone-300 bg-white
+			     px-2 py-0.5 text-sm text-stone-700 dark:border-stone-700
+			     dark:bg-stone-900 dark:text-stone-100">
+		{open ? <>&minus;</> : '+'}
+	      </button>)}
+	</div>
+	{open && tag.children.length > 0 && (
+	    <div
+		ref={expansionSlotRef}
+		className={cn (
+		    'h-full min-h-0 max-h-full overflow-hidden box-border',
+		    depth === 0 ? 'pt-5' : 'pt-3')}>
+	      <div
+		  ref={expansionBorderRef}
+		  className="relative max-h-full overflow-hidden rounded-2xl border border-stone-200
+			     bg-stone-100/70 py-2 pl-2 pr-2 text-stone-900
+			     dark:border-stone-700 dark:bg-stone-900/70 dark:text-stone-100">
+		<div className="flex h-full min-h-0 max-h-full flex-row-reverse items-start gap-2
+				overflow-hidden">
+		  <span
+		      aria-hidden="true"
+		      className="absolute -right-3 top-4 h-px w-3 bg-stone-300 dark:bg-stone-600"/>
+		  {tag.children.map (child => (
+		      <div
+			  key={child.id}
+			  className="relative h-full min-h-0 max-h-full overflow-hidden">
+			<MobileMaterialTreeNode
+			    tag={child}
+			    depth={depth + 1}
+			    availableInlineSizePx={childAvailableInlineSizePx}
+			    materialFilter={materialFilter}
+			    selectedTagId={selectedTagId}
+			    openTags={openTags}
+			    setOpenTags={setOpenTags}
+			    onChildren={onChildren}/>
+		      </div>))}
+		</div>
+	      </div>
+	    </div>)}
+      </div>)
+}
+
+
+const MaterialSidebar: FC = () => {
+  const location = useLocation ()
+  const navigate = useNavigate ()
+  const qs = new URLSearchParams (location.search)
+  const materialFilter = parseMaterialFilter (qs.get ('material_filter'), 'any')
+  const selectedTagId = Number (qs.get ('tag_id') ?? 0) || null
+
+  const [desktopTags, setDesktopTags] = useState<MaterialSidebarTag[]> ([])
+  const [openTags, setOpenTags] = useState<Record<number, boolean>> ({ })
+  const mobileRailRef = useRef<HTMLDivElement | null> (null)
+  const [mobileAvailableInlineSizePx, setMobileAvailableInlineSizePx] =
+      useState<number | null> (null)
+
+  const { data: rootTags = [], isLoading, isError } = useQuery ({
+      queryKey: materialsKeys.tree ({ parentId: null, materialFilter }),
+      queryFn:  () => fetchMaterialTagTree ({ parentId: null, materialFilter })})
+
+  useEffect (() => {
+    setDesktopTags (rootTags)
+  }, [rootTags])
+
+  useEffect (() => {
+    const el = mobileRailRef.current
+    if (!(el))
+      return
+
+    requestAnimationFrame (() => {
+      el.scrollLeft = el.scrollWidth
+    })
+  }, [rootTags, materialFilter])
+
+  useEffect (() => {
+    const el = mobileRailRef.current
+    if (!(el))
+      return
+
+    const updateAvailableInlineSize = () => {
+      const nextInlineSize = Math.max (24, el.clientHeight)
+      setMobileAvailableInlineSizePx (prev => prev === nextInlineSize ? prev : nextInlineSize)
+    }
+
+    updateAvailableInlineSize ()
+
+    const resizeObserver = new ResizeObserver (() => {
+      updateAvailableInlineSize ()
+    })
+
+    resizeObserver.observe (el)
+
+    return () => {
+      resizeObserver.disconnect ()
+    }
+  }, [rootTags, materialFilter])
+
+  const visibleRootTags = desktopTags.length > 0 ? desktopTags : rootTags
+
+  const setChildren = (tagId: number, children: MaterialSidebarTag[]) => {
+    setDesktopTags (prev => {
+      const base = prev.length > 0 ? prev : rootTags
+      return setChildrenById (base, tagId, children)
+    })
+  }
+
+  const handleFilterChange = (value: MaterialFilter) => {
+    setDesktopTags ([])
+    setOpenTags ({ })
+    updateMaterialFilterQuery (location.pathname, location.search, navigate, value)
+  }
+
+  const renderDesktopTree = (tags: MaterialSidebarTag[]): ReactNode => (
+      tags.map (tag => (
+	  <MaterialTreeNode
+	      key={tag.id}
+	      tag={tag}
+	      materialFilter={materialFilter}
+	      selectedTagId={selectedTagId}
+	      openTags={openTags}
+	      setOpenTags={setOpenTags}
+	      onChildren={setChildren}/>)))
+
+  return (
+      <>
+	<div className="border-b bg-stone-50 p-3 dark:border-stone-700 dark:bg-stone-950
+			dark:text-stone-100 md:hidden flex h-[25dvh] min-h-0 flex-col
+			overflow-hidden">
+	  <MaterialFilterButtons
+	      materialFilter={materialFilter}
+	      onChange={handleFilterChange}/>
+	  <div
+	      ref={mobileRailRef}
+	      className="mt-3 min-h-0 flex-1 overflow-x-auto overflow-y-hidden">
+	    <div className="flex min-w-max flex-row-reverse items-start gap-3 pb-1 h-full
+			    min-h-0 max-h-full">
+	      {visibleRootTags.map (tag => (
+		  <MobileMaterialTreeNode
+		      key={tag.id}
+		      tag={tag}
+		      availableInlineSizePx={mobileAvailableInlineSizePx}
+		      materialFilter={materialFilter}
+		      selectedTagId={selectedTagId}
+		      openTags={openTags}
+		      setOpenTags={setOpenTags}
+		      onChildren={setChildren}/>))}
+	    </div>
+	  </div>
+	</div>
+
+	<SidebarComponent sidebarKey="materials" className="hidden md:block">
+	  <div className="space-y-4">
+	    <MaterialFilterButtons
+		materialFilter={materialFilter}
+		onChange={handleFilterChange}/>
+	    {isLoading && (
+		<p className="text-sm text-neutral-500 dark:text-stone-400">読込中……</p>)}
+	    {isError && (
+		<p className="text-sm text-red-600 dark:text-red-300">
+		  タグ一覧の取得に失敗しました．
+		</p>)}
+	    {(!isLoading && !isError) && (
+		<ul>
+		  {renderDesktopTree (visibleRootTags)}
+		</ul>)}
+	  </div>
+	</SidebarComponent>
+      </>)
+}
+
+
+export default MaterialSidebar

frontend/src/components/NicoViewer.tsx

@@ -107,8 +107,7 @@ export default forwardRef ((props: Props, ref: ForwardedRef<NiconicoViewerHandle
     loadCompleteTimerRef.current = setTimeout (() => {
       onError?.({
 	  eventName: 'loadCompleteTimeout',
-	  reason:    'niconico video length was not reported by embed',
-      })
+	  reason:    'niconico video length was not reported by embed'})
     }, LOAD_COMPLETE_TIMEOUT_MS)
   }, [clearLoadCompleteTimer, onError])
 

frontend/src/components/PostEditForm.test.tsx

@@ -66,4 +66,27 @@ describe ('PostEditForm', () => {
     expect (onSave).toHaveBeenCalledWith (expect.objectContaining ({ versionNo: 5 }))
     expect (toastApi.toast).toHaveBeenCalledWith ({ description: '更新しました．' })
   })
+
+  it ('preserves duration while the video tag is temporarily removed', () => {
+    const post = buildPost ({
+      videoMs: 180_500,
+      tags:    [
+        buildTag ({ id: 1, name: '動画', category: 'general' }),
+        buildTag ({ id: 2, name: 'general-tag', category: 'general' }),
+      ],
+    })
+
+    render (<PostEditForm post={post} onSave={vi.fn ()}/>)
+
+    expect (screen.getByRole ('spinbutton')).toHaveValue (180.5)
+
+    const tags = screen.getAllByRole ('textbox')[2]
+    fireEvent.change (tags, { target: { value: 'general-tag' } })
+    expect (screen.queryByRole ('spinbutton')).not.toBeInTheDocument ()
+
+    fireEvent.change (tags, {
+      target: { value: '動画 general-tag' },
+    })
+    expect (screen.getByRole ('spinbutton')).toHaveValue (180.5)
+  })
 })

frontend/src/components/PostEditForm.tsx

@@ -1,4 +1,4 @@
-import { useEffect, useState } from 'react'
+import { useEffect, useMemo, useState } from 'react'
 
 import PostFormTagsArea from '@/components/PostFormTagsArea'
 import PostOriginalCreatedTimeField from '@/components/PostOriginalCreatedTimeField'
@@ -9,29 +9,35 @@ import { Button } from '@/components/ui/button'
 import { toast } from '@/components/ui/use-toast'
 import { isApiError } from '@/lib/api'
 import { updatePost } from '@/lib/posts'
-import { inputClass } from '@/lib/utils'
+import { inputClass, msToTime } from '@/lib/utils'
 import { useValidationErrors } from '@/lib/useValidationErrors'
 
 import type { FC, FormEvent } from 'react'
 
-import type { Post, Tag } from '@/types'
+import type { Post, TagWithSections } from '@/types'
 
 type PostFormField =
-    'parentPostIds' | 'tags' | 'originalCreatedAt'
+    'parentPostIds' | 'tags' | 'videoMs' | 'originalCreatedAt'
+
+const videoMsToDurationValue = (videoMs: number | null): string =>
+    videoMs == null ? '' : String (videoMs / 1_000)
 
 
-const tagsToStr = (tags: Tag[]): string => {
-  const result: Tag[] = []
+const tagsToStr = (tags: TagWithSections[]): string => {
+  const result: Omit<TagWithSections, 'children'>[] = []
 
-  const walk = (tag: Tag) => {
+  const walk = (tag: TagWithSections) => {
     const { children, ...rest } = tag
     result.push (rest)
-    children?.forEach (walk)
+    children.forEach (walk)
   }
 
   tags.filter (t => t.category !== 'nico').forEach (walk)
 
-  return [...(new Set (result.map (t => t.name)))].join (' ')
+  return [...(new Set (result.map (t =>
+      `${ t.name }${ t.sections
+		     .map (s => `[${ msToTime (s.beginMs) }-${ s.endMs == null ? '' : msToTime (s.endMs) }]`)
+		     .join ('') }`)))].join (' ')
 }
 
 
@@ -41,6 +47,7 @@ type Props = { post:    Post
 
 const PostEditForm: FC<Props> = ({ post, onSave }) => {
   const [disabled, setDisabled] = useState (false)
+  const [duration, setDuration] = useState<string> (videoMsToDurationValue (post.videoMs))
   const { baseErrors, fieldErrors, clearValidationErrors, applyValidationError } =
       useValidationErrors<PostFormField> ()
   const [originalCreatedBefore, setOriginalCreatedBefore] =
@@ -52,6 +59,10 @@ const PostEditForm: FC<Props> = ({ post, onSave }) => {
   const [tags, setTags] = useState<string> ('')
   const [title, setTitle] = useState (post.title)
 
+  const videoFlg =
+      useMemo (() => tags.split (/\s+/).some (tag => tag.replace (/\[.*\]$/, '') === '動画'),
+	       [tags])
+
   const dialogue = useDialogue ()
 
   const update = async (...args: Parameters<typeof updatePost>) => {
@@ -63,6 +74,7 @@ const PostEditForm: FC<Props> = ({ post, onSave }) => {
       onSave ({ ...post,
 		versionNo:              data.versionNo,
 		title:                  data.title,
+		videoMs:                data.videoMs,
 		tags:                   data.tags,
 		parentPosts:            data.parentPosts,
 		childPosts:             data.childPosts,
@@ -102,6 +114,7 @@ const PostEditForm: FC<Props> = ({ post, onSave }) => {
 	{
 	  // TODO: 差分 UI
 	  await update ({ id: post.id, title, tags, parentPostIds,
+			  duration: videoFlg ? duration : null,
 			  originalCreatedFrom, originalCreatedBefore },
 			{ baseVersionNo: post.versionNo, merge: true })
 	  return
@@ -110,6 +123,7 @@ const PostEditForm: FC<Props> = ({ post, onSave }) => {
       if (action === 'overwrite')
 	{
 	  await update ({ id: post.id, title, tags, parentPostIds,
+			  duration: videoFlg ? duration : null,
 			  originalCreatedFrom, originalCreatedBefore },
 			{ baseVersionNo: post.versionNo, force: true })
 	  return
@@ -124,6 +138,7 @@ const PostEditForm: FC<Props> = ({ post, onSave }) => {
     try
     {
       await update ({ id: post.id, title, tags, parentPostIds,
+		      duration: videoFlg ? duration : null,
 		      originalCreatedFrom, originalCreatedBefore },
 		    { baseVersionNo: post.versionNo })
     }
@@ -134,7 +149,8 @@ const PostEditForm: FC<Props> = ({ post, onSave }) => {
   }
 
   useEffect (() => {
-    setTags(tagsToStr (post.tags))
+    setTags (tagsToStr (post.tags))
+    setDuration (videoMsToDurationValue (post.videoMs))
   }, [post])
 
   return (
@@ -149,7 +165,7 @@ const PostEditForm: FC<Props> = ({ post, onSave }) => {
 		  disabled={disabled}
 		  className={inputClass (invalid)}
 		  value={title ?? ''}
-		  onChange={ev => setTitle (ev.target.value)}/>)}
+		  onChange={e => setTitle (e.target.value)}/>)}
 	</FormField>
 
 	{/* 親投稿 */}
@@ -181,6 +197,20 @@ const PostEditForm: FC<Props> = ({ post, onSave }) => {
 	    setOriginalCreatedBefore={setOriginalCreatedBefore}
 	    errors={fieldErrors.originalCreatedAt}/>
 
+	{/* 動画時間 */}
+	{videoFlg && (
+	    <FormField label="動画時間" messages={fieldErrors.videoMs}>
+	      {({ invalid }) => (
+		  <input
+		      type="number"
+		      min="0.001"
+		      step="0.001"
+		      disabled={disabled}
+		      className={inputClass (invalid)}
+		      value={duration}
+		      onChange={e => setDuration (e.target.value)}/>)}
+	    </FormField>)}
+
 	{/* 送信 */}
 	<Button type="submit" disabled={disabled}>
 	  更新
@@ -188,4 +218,5 @@ const PostEditForm: FC<Props> = ({ post, onSave }) => {
       </form>)
 }
 
+
 export default PostEditForm

frontend/src/components/PostOriginalCreatedTimeField.tsx

@@ -19,8 +19,7 @@ const PostOriginalCreatedTimeField: FC<Props> = (
       setOriginalCreatedFrom,
       originalCreatedBefore,
       setOriginalCreatedBefore,
-      errors }: Props,
-) => (
+      errors }: Props) => (
     <FormField label="オリジナルの作成日時" messages={errors}>
       {({ describedBy, invalid }) => (
 	  <>

frontend/src/components/ResponsiveMarqueeText.tsx

@@ -0,0 +1,250 @@
+import { cn } from '@/lib/utils'
+import { useEffect, useRef, useState } from 'react'
+
+import type { FC } from 'react'
+
+type Props = {
+    text:      string
+    className?: string
+    truncateOnMobile?: boolean
+    title?:    string }
+
+const DESKTOP_MARQUEE_MEDIA =
+    '(min-width: 768px) and (hover: hover) and (pointer: fine) and (prefers-reduced-motion: no-preference)'
+const MARQUEE_START_DELAY_MS = 1600
+const MARQUEE_END_HOLD_MS = 2400
+const MARQUEE_SCROLL_PX_PER_SECOND = 43
+const MIN_MARQUEE_OVERFLOW_PX = 1
+
+
+const ResponsiveMarqueeText: FC<Props> = (
+    { text, className, truncateOnMobile = false, title },
+) => {
+  const outerRef = useRef<HTMLSpanElement | null> (null)
+  const staticRef = useRef<HTMLSpanElement | null> (null)
+  const animatedRef = useRef<HTMLSpanElement | null> (null)
+  const animationRef = useRef<Animation | null> (null)
+  const timeoutRef = useRef<number | null> (null)
+  const rafRef = useRef<number | null> (null)
+  const [overflowPx, setOverflowPx] = useState (0)
+  const [desktopMarqueeEnabled, setDesktopMarqueeEnabled] = useState (false)
+  const [active, setActive] = useState (false)
+  const [marqueeVisible, setMarqueeVisible] = useState (false)
+
+  useEffect (() => {
+    const outer = outerRef.current
+    const inner = staticRef.current
+
+    if (!(outer) || !(inner))
+      return
+
+    const measure = () => {
+      const nextOverflow = Math.max (0, Math.ceil (inner.scrollWidth - outer.clientWidth))
+      setOverflowPx (prev => Math.abs (prev - nextOverflow) <= 1 ? prev : nextOverflow)
+    }
+
+    measure ()
+
+    const resizeObserver =
+	typeof ResizeObserver === 'undefined'
+	? null
+	: new ResizeObserver (() => {
+	    measure ()
+	  })
+
+    resizeObserver?.observe (outer)
+    resizeObserver?.observe (inner)
+    addEventListener ('resize', measure)
+
+    return () => {
+      resizeObserver?.disconnect ()
+      removeEventListener ('resize', measure)
+    }
+  }, [text])
+
+  useEffect (() => {
+    if (typeof window === 'undefined' || typeof window.matchMedia !== 'function')
+      return
+
+    const media = window.matchMedia (DESKTOP_MARQUEE_MEDIA)
+    const update = () => {
+      setDesktopMarqueeEnabled (media.matches)
+    }
+
+    update ()
+    media.addEventListener ('change', update)
+
+    return () => {
+      media.removeEventListener ('change', update)
+    }
+  }, [])
+
+  useEffect (() => {
+    const clearScheduled = () => {
+      if (timeoutRef.current != null)
+        {
+          clearTimeout (timeoutRef.current)
+          timeoutRef.current = null
+        }
+      if (rafRef.current != null)
+        {
+          cancelAnimationFrame (rafRef.current)
+          rafRef.current = null
+        }
+      animationRef.current?.cancel ()
+      animationRef.current = null
+    }
+
+    const animated = animatedRef.current
+    const canMarquee = (
+        active
+        && desktopMarqueeEnabled
+        && overflowPx >= MIN_MARQUEE_OVERFLOW_PX
+        && animated != null)
+
+    const resetAnimated = () => {
+      const node = animatedRef.current
+
+      animationRef.current?.cancel ()
+      animationRef.current = null
+      node?.getAnimations?.().forEach (animation => {
+        animation.cancel ()
+      })
+
+      if (!(node))
+        return
+
+      node.style.transition = 'none'
+      node.style.transform = 'translateX(0)'
+    }
+
+    if (!canMarquee)
+      {
+        clearScheduled ()
+        resetAnimated ()
+        setMarqueeVisible (false)
+        return
+      }
+
+    let cancelled = false
+
+    const sleep = (ms: number) =>
+	new Promise<void> (resolve => {
+	  timeoutRef.current = window.setTimeout (() => {
+	    timeoutRef.current = null
+	    resolve ()
+	  }, ms)
+	})
+
+    const runLoop = async () => {
+      while (!cancelled)
+        {
+          resetAnimated ()
+          setMarqueeVisible (true)
+
+          await sleep (MARQUEE_START_DELAY_MS)
+          if (cancelled || !(animatedRef.current))
+            break
+
+          const moveDurationMs =
+	      overflowPx / MARQUEE_SCROLL_PX_PER_SECOND * 1000
+          const node = animatedRef.current
+
+          if (typeof node.animate === 'function')
+            {
+              const animation = node.animate (
+		  [
+		    { transform: 'translateX(0)' },
+		    { transform: `translateX(-${ overflowPx }px)` },
+		  ],
+		  { duration: moveDurationMs, easing: 'linear', fill: 'forwards' })
+              animationRef.current = animation
+              try
+              {
+                await animation.finished
+              }
+              catch
+              {
+                break
+              }
+
+              node.style.transform = `translateX(-${ overflowPx }px)`
+              animation.cancel ()
+              if (animationRef.current === animation)
+                animationRef.current = null
+            }
+          else
+            {
+              node.style.transition = `transform ${ moveDurationMs }ms linear`
+              await new Promise<void> (resolve => {
+                rafRef.current = requestAnimationFrame (() => {
+                  rafRef.current = null
+                  node.style.transform = `translateX(-${ overflowPx }px)`
+                  resolve ()
+                })
+              })
+              await sleep (moveDurationMs)
+              node.style.transition = 'none'
+              node.style.transform = `translateX(-${ overflowPx }px)`
+            }
+
+          if (cancelled)
+            break
+
+          await sleep (MARQUEE_END_HOLD_MS)
+          if (cancelled)
+            break
+
+          resetAnimated ()
+        }
+    }
+
+    void runLoop ()
+
+    return () => {
+      cancelled = true
+      clearScheduled ()
+      resetAnimated ()
+      setMarqueeVisible (false)
+    }
+  }, [active, desktopMarqueeEnabled, overflowPx, text])
+
+  return (
+      <span
+	  ref={outerRef}
+	  title={title ?? text}
+	  onMouseEnter={() => setActive (true)}
+	  onMouseLeave={() => setActive (false)}
+	  onFocus={() => setActive (true)}
+	  onBlur={() => setActive (false)}
+	  className={cn (
+	      'tag-marquee inline-block max-w-full min-w-0 align-bottom',
+	      (truncateOnMobile
+	       ? 'overflow-hidden text-ellipsis whitespace-nowrap'
+	       : 'whitespace-normal [overflow-wrap:anywhere]'),
+	      'md:overflow-hidden md:whitespace-nowrap',
+	      className)}>
+	<span
+	    ref={staticRef}
+	    className={cn (
+		'tag-marquee__static block max-w-full',
+		(truncateOnMobile
+		 ? 'overflow-hidden text-ellipsis whitespace-nowrap'
+		 : 'whitespace-normal [overflow-wrap:anywhere]'),
+		'md:overflow-hidden md:text-ellipsis md:whitespace-nowrap',
+		marqueeVisible && 'md:opacity-0')}>
+	  {text}
+	</span>
+	{overflowPx >= MIN_MARQUEE_OVERFLOW_PX && (
+	    <span
+		ref={animatedRef}
+		aria-hidden="true"
+		className={cn (
+		    'tag-marquee__animated hidden md:block',
+		    marqueeVisible ? 'md:opacity-100' : 'md:opacity-0')}>
+	      {text}
+	    </span>)}
+      </span>)
+}
+
+export default ResponsiveMarqueeText

frontend/src/components/TagDetailSidebar.tsx

@@ -26,19 +26,18 @@ import { dateString, originalCreatedAtString } from '@/lib/utils'
 import type { DragEndEvent } from '@dnd-kit/core'
 import type { FC, MutableRefObject, ReactNode } from 'react'
 
-import type { Category, Post, Tag } from '@/types'
+import type { Category, Post, TagWithSections } from '@/types'
 
-type TagByCategory = { [key in Category]: Tag[] }
+type TagByCategory = { [key in Category]: TagWithSections[] }
 
 
 const renderTagTree = (
-    tag:              Tag,
+    tag:              TagWithSections,
     nestLevel:        number,
     path:             string,
     suppressClickRef: MutableRefObject<boolean>,
     parentTagId?:     number,
-    sp?:              boolean,
-): ReactNode[] => {
+    sp?:              boolean): ReactNode[] => {
   const key = `${ path }-${ tag.id }`
 
   const self = (
@@ -63,7 +62,7 @@ const renderTagTree = (
 
 
 const isDescendant = (
-    root:     Tag,
+    root:     TagWithSections,
     targetId: number,
 ): boolean => {
   if (!(root.children))
@@ -84,8 +83,8 @@ const isDescendant = (
 const findTag = (
     byCat:  TagByCategory,
     id:     number,
-): Tag | undefined => {
-  const walk = (nodes: Tag[]): Tag | undefined => {
+): TagWithSections | undefined => {
+  const walk = (nodes: TagWithSections[]): TagWithSections | undefined => {
     for (const t of nodes)
       {
 	if (t.id === id)
@@ -130,8 +129,7 @@ const buildTagByCategory = (post: Post): TagByCategory => {
 
 const changeCategory = async (
     tagId:    number,
-    category: Category,
-): Promise<void> => {
+    category: Category): Promise<void> => {
   await apiPatch (`/tags/${ tagId }`, { category })
 }
 
@@ -148,10 +146,13 @@ const DropSlot = ({ cat }: { cat: Category }) => {
 }
 
 
-type Props = { post: Post; sp?: boolean }
+type Props = {
+    className?: string
+    post:       Post
+    sp?:        boolean }
 
 
-const TagDetailSidebar: FC<Props> = ({ post, sp }) => {
+const TagDetailSidebar: FC<Props> = ({ className, post, sp }) => {
   sp = Boolean (sp)
 
   const qc = useQueryClient ()
@@ -167,7 +168,7 @@ const TagDetailSidebar: FC<Props> = ({ post, sp }) => {
       }
 
     for (const cat of Object.keys (tagsTmp) as (keyof typeof tagsTmp)[])
-      tagsTmp[cat].sort ((tagA: Tag, tagB: Tag) => tagA.name < tagB.name ? -1 : 1)
+      tagsTmp[cat].sort ((tagA: TagWithSections, tagB: TagWithSections) => tagA.name < tagB.name ? -1 : 1)
 
     return tagsTmp
   }, [post])
@@ -280,7 +281,7 @@ const TagDetailSidebar: FC<Props> = ({ post, sp }) => {
   }, [baseTags])
 
   return (
-      <SidebarComponent>
+      <SidebarComponent sidebarKey="post-detail-tags" className={className}>
 	<TagSearch/>
 	<DndContext
 	    sensors={sensors}
@@ -294,8 +295,7 @@ const TagDetailSidebar: FC<Props> = ({ post, sp }) => {
 	      addEventListener ('click', e => {
 		e.preventDefault ()
 		e.stopPropagation ()
-		suppressClickRef.current = false
-	      }, { capture: true, once: true })
+		suppressClickRef.current = false}, { capture: true, once: true })
 	    }}
 	    onDragCancel={() => {
 	      setActiveTagId (null)
@@ -378,4 +378,4 @@ const TagDetailSidebar: FC<Props> = ({ post, sp }) => {
       </SidebarComponent>)
 }
 
-export default TagDetailSidebar
+export default TagDetailSidebar

frontend/src/components/TagLink.tsx

@@ -1,4 +1,5 @@
 import PrefetchLink from '@/components/PrefetchLink'
+import ResponsiveMarqueeText from '@/components/ResponsiveMarqueeText'
 import { LIGHT_COLOUR_SHADE, DARK_COLOUR_SHADE, TAG_COLOUR } from '@/consts'
 import { cn } from '@/lib/utils'
 
@@ -9,6 +10,7 @@ import type { Tag } from '@/types'
 type CommonProps = { 
     tag:        Tag
     nestLevel?: number
+    truncateOnMobile?: boolean
     withWiki?:  boolean
     withCount?: boolean }
 
@@ -28,11 +30,14 @@ type Props =
 
 
 const TagLink: FC<Props> = ({ tag,
-		   nestLevel = 0,
-		   linkFlg   = true,
-		   withWiki  = true,
-		   withCount = true,
-		   ...props }) => {
+			      nestLevel = 0,
+			      linkFlg   = true,
+			      truncateOnMobile = false,
+			      withWiki  = true,
+			      withCount = true,
+			      className,
+			      title,
+			      ...props }) => {
   const spanClass = cn (
       `text-${ TAG_COLOUR[tag.category] }-${ LIGHT_COLOUR_SHADE }`,
       `dark:text-${ TAG_COLOUR[tag.category] }-${ DARK_COLOUR_SHADE }`)
@@ -40,11 +45,18 @@ const TagLink: FC<Props> = ({ tag,
       spanClass,
       `hover:text-${ TAG_COLOUR[tag.category] }-${ LIGHT_COLOUR_SHADE - 200 }`,
       `dark:hover:text-${ TAG_COLOUR[tag.category] }-${ DARK_COLOUR_SHADE - 200 }`)
+  const textClass = 'group min-w-0 max-w-full overflow-hidden align-bottom'
+  const rootClass =
+      'inline-flex min-w-0 max-w-full flex-nowrap items-stretch align-baseline gap-x-1 md:items-baseline'
+  const markerWrapClass = 'shrink-0 self-start md:self-auto'
+  const countClass = 'shrink-0 self-end md:self-auto'
+  const textTitle = title
+      ?? (tag.matchedAlias == null ? tag.name : `${ tag.matchedAlias } → ${ tag.name }`)
 
   return (
-      <>
+      <span className={rootClass}>
 	{(linkFlg && withWiki) && (
-	    <span className="mr-1">
+	    <span className={markerWrapClass}>
 	      {(tag.materialId != null || tag.hasWiki || tag.hasDeerjikists)
 	       ? (
 		  tag.materialId == null && !(tag.hasDeerjikists)
@@ -99,33 +111,48 @@ const TagLink: FC<Props> = ({ tag,
 	    </span>)}
 	{nestLevel > 0 && (
 	    <span
-		className="ml-1 mr-1"
+		className="ml-1 mr-1 shrink-0"
 		style={{ paddingLeft: `${ (nestLevel - 1) }rem` }}>
 	      ↳
 	    </span>)}
 	{tag.matchedAlias != null && (
 	    <>
-	      <span className={spanClass} {...props}>
-		{tag.matchedAlias}
+	      <span
+		  title={textTitle}
+		  className={cn (spanClass, textClass, className)}
+		  {...props}>
+		<ResponsiveMarqueeText
+		    text={tag.matchedAlias}
+		    title={textTitle}
+		    truncateOnMobile={truncateOnMobile}/>
 	      </span>
-	      <> → </>
+	      <span className="shrink-0"> → </span>
 	    </>)}
 	{linkFlg
 	 ? (
 	    <PrefetchLink
 		to={`/posts?${ (new URLSearchParams ({ tags: tag.name })).toString () }`}
-		className={linkClass}
+		title={textTitle}
+		className={cn (linkClass, textClass, className)}
 		{...props}>
-	      {tag.name}
+	      <ResponsiveMarqueeText
+		  text={tag.name}
+		  title={textTitle}
+		  truncateOnMobile={truncateOnMobile}/>
 	    </PrefetchLink>)
 	 : (
-	    <span className={spanClass}
+	    <span
+		  title={textTitle}
+		  className={cn (spanClass, textClass, className)}
 		  {...props}>
-	      {tag.name}
+	      <ResponsiveMarqueeText
+		  text={tag.name}
+		  title={textTitle}
+		  truncateOnMobile={truncateOnMobile}/>
 	    </span>)}
 	{withCount && (
-	    <span className="ml-1">{tag.postCount}</span>)}
-      </>)
+	    <span className={countClass}>{tag.postCount}</span>)}
+      </span>)
 }
 
 export default TagLink

frontend/src/components/TagSearchBox.tsx

@@ -20,12 +20,14 @@ const TagSearchBox: FC<Props> = ({ suggestions, activeIndex, onSelect }) => {
 		     rounded shadow">
 	{suggestions.map ((tag, i) => (
 	    <li key={tag.id}
-		className={cn ('px-3 py-2 cursor-pointer hover:bg-gray-300 dark:hover:bg-gray-700', 
+		className={cn ('min-w-0 overflow-hidden px-3 py-2 cursor-pointer hover:bg-gray-300 dark:hover:bg-gray-700',
 			       i === activeIndex && 'bg-gray-300 dark:bg-gray-700')}
 		onMouseDown={() => onSelect (tag)}>
-	      <TagLink tag={tag} linkFlg={false} withWiki={false}/>
+	      <div className="flex min-w-0 max-w-full items-baseline overflow-hidden">
+		<TagLink tag={tag} linkFlg={false} withWiki={false}/>
+	      </div>
 	    </li>))}
       </ul>)
 }
 
-export default TagSearchBox
+export default TagSearchBox

frontend/src/components/TagSidebar.tsx

@@ -64,8 +64,9 @@ const TagSidebar: FC<Props> = ({ posts, onClick }) => {
 	<ul>
 	  {CATEGORIES.flatMap (cat => cat in tags ? (
 	      tags[cat].map (tag => (
-		  <li key={tag.id} className="mb-1">
+		  <li key={tag.id} className="mb-1 min-w-0 max-w-full overflow-hidden">
 		    <motion.div
+			className="flex min-w-0 max-w-full items-baseline overflow-hidden"
 			transition={{ layout: { duration: .2, ease: 'easeOut' } }}
 			layoutId={`tag-${ tag.id }`}>
 		      <TagLink tag={tag} onClick={onClick}/>
@@ -95,7 +96,7 @@ const TagSidebar: FC<Props> = ({ posts, onClick }) => {
       </>)
 
   return (
-      <SidebarComponent>
+      <SidebarComponent sidebarKey="posts-index-tags">
 	<TagSearch/>
 
 	<div className="hidden md:block mt-4">
@@ -128,4 +129,4 @@ const TagSidebar: FC<Props> = ({ posts, onClick }) => {
       </SidebarComponent>)
 }
 
-export default TagSidebar
+export default TagSidebar

frontend/src/components/TopNav.tsx

@@ -7,30 +7,36 @@ import Separator from '@/components/MenuSeparator'
 import PrefetchLink from '@/components/PrefetchLink'
 import TopNavUser from '@/components/TopNavUser'
 import { WikiIdBus } from '@/lib/eventBus/WikiIdBus'
-import { tagsKeys, wikiKeys } from '@/lib/queryKeys'
+import { materialsKeys, tagsKeys, wikiKeys } from '@/lib/queryKeys'
 import { fetchTag, fetchTagByName } from '@/lib/tags'
+import { fetchMaterial } from '@/lib/materials'
 import { cn } from '@/lib/utils'
 import { fetchWikiPage } from '@/lib/wiki'
 
 import type { FC, MouseEvent } from 'react'
 
-import type { Menu, MenuVisibleItem, Tag, User } from '@/types'
+import type { Material, Menu, MenuVisibleItem, Tag, User } from '@/types'
 
 type Props = { user: User | null }
 
 
-export const menuOutline = ({ tag, wikiId, user, pathName }: { 
-    tag?: Tag | null
-    wikiId: number | null
-    user: User | null,
-    pathName: string }): Menu => {
-  const postCount = tag?.postCount ?? 0
+export const menuOutline = (
+    { tag, material, wikiId, user, pathName }: {
+	tag?: Tag | null
+	material?: Material | null
+	wikiId: number | null
+	user: User | null,
+	pathName: string },
+): Menu => {
+  const postCount = tag?.postCount ?? material?.tag?.postCount ?? 0
 
   const wikiPageFlg = Boolean (/^\/wiki\/(?!new|changes)[^/]+/.test (pathName) && wikiId)
   const wikiTitle = pathName.split ('/')[2] ?? ''
 
   const tagFlg = /^\/tags\/\d+/.test (pathName)
 
+  const materialFlg = /^\/materials\/\d+/.test (pathName)
+
   return [
       { name: '広場', to: '/posts', subMenu: [
 	  { name: '一覧', to: '/posts' },
@@ -49,12 +55,18 @@ export const menuOutline = ({ tag, wikiId, user, pathName }: {
 	    visible: tagFlg },
 	  { name: '履歴', to: `/tags/changes?id=${ tag?.id }`,
 	    visible: tagFlg && tag?.category !== 'nico' }] },
-      { name: '素材', to: '/materials', visible: false, subMenu: [
+      { name: '素材', to: '/materials', visible: true, subMenu: [
 	  { name: '一覧', to: '/materials' },
-	  { name: '検索', to: '/materials/search', visible: false }, 
 	  { name: '追加', to: '/materials/new' },
-	  { name: '全体履歴', to: '/materials/changes', visible: false },
-	  { name: 'ヘルプ', to: '/wiki/ヘルプ:素材集' }] },
+	  { name: '抑止', to: '/materials/suppressions' },
+	  { name: '全体履歴', to: '/materials/changes' },
+	  { name: 'ヘルプ', to: '/wiki/ヘルプ:素材管理' },
+	  { component: <Separator/>, visible: materialFlg },
+	  { name: `広場 (${ postCount || 0 })`,
+	    to: `/posts?tags=${ encodeURIComponent (material?.tag?.name ?? '') }`,
+	    visible: materialFlg && Boolean (material?.tag) },
+	  { name: '履歴', to: `/materials/changes?material_id=${ material?.id }`,
+	    visible: materialFlg }] },
       { name: 'Wiki', to: '/wiki/ヘルプ:ホーム', base: '/wiki', subMenu: [
 	  { name: '検索', to: '/wiki' },
 	  { name: '新規', to: '/wiki/new' },
@@ -119,15 +131,23 @@ const TopNav: FC<Props> = ({ user }) => {
       queryFn: () => fetchWikiPage (wikiIdStr, { }) })
 
   const tagFlg = /^\/tags\/\d+/.test (location.pathname)
-  const effectiveTitle = (tagFlg ? location.pathname.split ('/')[2] : wikiPage?.title) ?? ''
+  const materialFlg = /^\/materials\/\d+/.test (location.pathname)
+  const effectiveTitle = (((tagFlg || materialFlg)
+			   ? location.pathname.split ('/')[2]
+			   : wikiPage?.title)
+			  ?? '')
 
   const { data: tag } = useQuery ({
       enabled: Boolean (effectiveTitle),
       queryKey: tagsKeys.show (effectiveTitle),
       queryFn: () => (tagFlg ? fetchTag : fetchTagByName) (effectiveTitle) })
 
+  const { data: material } = useQuery ({
+      enabled: Boolean (effectiveTitle),
+      queryKey: materialsKeys.show (effectiveTitle),
+      queryFn: () => fetchMaterial (effectiveTitle) })
 
-  const menu = menuOutline ({ tag, wikiId, user, pathName: location.pathname })
+  const menu = menuOutline ({ tag, material, wikiId, user, pathName: location.pathname })
   const visibleMenu = menu.filter ((item): item is MenuVisibleItem => item.visible ?? true)
   const moreMenu = menu.filter (item =>
       !(item.visible ?? true)

frontend/src/components/common/PageTitle.tsx

@@ -1,12 +1,14 @@
 import React from 'react'
 
+import { cn } from '@/lib/utils'
+
 import type { FC } from 'react'
 
-type Props = { children: React.ReactNode }
+type Props = { children: React.ReactNode; className?: string }
 
 
-const PageTitle: FC<Props> = ({ children }) => (
-    <h1 className="text-2xl font-bold mb-2">
+const PageTitle: FC<Props> = ({ children, className, ...rest }) => (
+    <h1 className={cn ('text-2xl font-bold mb-2', className)} {...rest}>
       {children}
     </h1>)
 

frontend/src/components/common/Pagination.tsx

@@ -16,8 +16,7 @@ const range = (start: number, end: number): number[] =>
 const getPages = (
     page:         number,
     total:        number,
-    siblingCount: number,
-): (number | '…')[] => {
+    siblingCount: number): (number | '…')[] => {
   if (total <= 1)
     return [1]
 

frontend/src/components/dialogues/DialogueProvider.tsx

@@ -103,8 +103,7 @@ const DialogueProvider: FC<Props> = ({ children }) => {
       choice: options => new Promise (resolve => {
 	push ({ kind: 'choice',
 		options: options as ChoiceOptions<string>,
-		resolve: resolve as (value: string | null) => void })
-      }) }), [push])
+		resolve: resolve as (value: string | null) => void })}) }), [push])
 
   const active = queue[0]
 

frontend/src/components/layout/SidebarComponent.test.tsx

@@ -0,0 +1,124 @@
+import { fireEvent, render, screen, waitFor } from '@testing-library/react'
+import { HelmetProvider } from 'react-helmet-async'
+import { beforeEach, describe, expect, it, vi } from 'vitest'
+
+import SidebarComponent from '@/components/layout/SidebarComponent'
+
+
+const sidebarWidth = (element: Element | null): string =>
+    (element as HTMLElement).style.getPropertyValue ('--sidebar-width')
+
+
+const sidebarRoot = (container: HTMLElement): Element =>
+    container.querySelector ('[style*="--sidebar-width"]')!
+
+
+const sidebarTree = (props: Partial<Parameters<typeof SidebarComponent>[0]>) => (
+    <HelmetProvider>
+      <div data-sidebar-container>
+	<SidebarComponent sidebarKey="test-sidebar" {...props}>
+	  Sidebar body
+	</SidebarComponent>
+      </div>
+    </HelmetProvider>)
+
+
+const renderSidebar = (
+    props: Partial<Parameters<typeof SidebarComponent>[0]> = {},
+    containerWidth = 800,
+) => {
+  Object.defineProperty (HTMLElement.prototype, 'clientWidth', {
+      configurable: true,
+      get () {
+	return this.hasAttribute ('data-sidebar-container') ? containerWidth : 0
+      },
+  })
+
+  const rendered = render (sidebarTree (props))
+
+  return rendered
+}
+
+
+describe ('SidebarComponent', () => {
+  beforeEach (() => {
+    Object.defineProperty (window, 'innerWidth', {
+	configurable: true,
+	value:        1_000,
+    })
+
+    Object.defineProperty (HTMLElement.prototype, 'setPointerCapture', {
+	configurable: true,
+	value:        vi.fn (),
+    })
+    Object.defineProperty (HTMLElement.prototype, 'releasePointerCapture', {
+	configurable: true,
+	value:        vi.fn (),
+    })
+    Object.defineProperty (HTMLElement.prototype, 'hasPointerCapture', {
+	configurable: true,
+	value:        vi.fn (() => true),
+    })
+
+    vi.spyOn (HTMLElement.prototype, 'setPointerCapture').mockImplementation (() => {
+      ;
+    })
+    vi.spyOn (HTMLElement.prototype, 'releasePointerCapture').mockImplementation (() => {
+      ;
+    })
+    vi.spyOn (HTMLElement.prototype, 'hasPointerCapture').mockReturnValue (true)
+  })
+
+  it ('uses maxWidth without applying the container main-width reserve twice', async () => {
+    localStorage.setItem ('sidebar:test-sidebar:left:width', '700')
+    const onWidthChange = vi.fn ()
+
+    const { container } = renderSidebar ({ maxWidth: 700, onWidthChange }, 800)
+
+    await waitFor (() => {
+      expect (sidebarWidth (sidebarRoot (container))).toBe ('700px')
+    })
+    expect (onWidthChange).toHaveBeenLastCalledWith (700)
+  })
+
+  it ('resets width and removes only its storage key on double click', async () => {
+    localStorage.setItem ('sidebar:test-sidebar:right:width', '420')
+    localStorage.setItem ('sidebar:other-sidebar:right:width', '480')
+
+    const { container } = renderSidebar ({ side: 'right' }, 900)
+
+    await waitFor (() => {
+      expect (sidebarWidth (sidebarRoot (container))).toBe ('420px')
+    })
+
+    fireEvent.doubleClick (screen.getByRole ('separator', { name: 'サイドバー幅' }))
+
+    await waitFor (() => {
+      expect (sidebarWidth (sidebarRoot (container))).toBe ('256px')
+    })
+    expect (localStorage.getItem ('sidebar:test-sidebar:right:width')).toBeNull ()
+    expect (localStorage.getItem ('sidebar:other-sidebar:right:width')).toBe ('480')
+  })
+
+  it ('clamps current width on maxWidth changes without re-reading storage', async () => {
+    localStorage.setItem ('sidebar:test-sidebar:left:width', '420')
+
+    const { container, rerender } = renderSidebar ({ maxWidth: 420 }, 900)
+
+    await waitFor (() => {
+      expect (sidebarWidth (sidebarRoot (container))).toBe ('420px')
+    })
+
+    rerender (sidebarTree ({ maxWidth: 300 }))
+
+    await waitFor (() => {
+      expect (sidebarWidth (sidebarRoot (container))).toBe ('300px')
+    })
+
+    rerender (sidebarTree ({ maxWidth: 500 }))
+
+    await waitFor (() => {
+      expect (sidebarWidth (sidebarRoot (container))).toBe ('300px')
+    })
+  })
+})

frontend/src/components/layout/SidebarComponent.tsx

@@ -1,19 +1,319 @@
 import { motion } from 'framer-motion'
 import { Helmet } from 'react-helmet-async'
 
-import type { FC, ReactNode } from 'react'
+import { cn } from '@/lib/utils'
 
-type Props = { children: ReactNode }
+import type { CSSProperties, FC, MouseEvent, PointerEvent, ReactNode } from 'react'
+import { useCallback, useEffect, useRef, useState } from 'react'
+
+type SidebarSide = 'left' | 'right'
+
+type Props = {
+    children:      ReactNode
+    className?:    string
+    maxWidth?:     number
+    onWidthChange?: (width: number) => void
+    sidebarKey:    string
+    side?:         SidebarSide }
+
+type ResizeState = {
+    pointerId:  number
+    startWidth: number
+    startX:     number
+    side:       SidebarSide }
+
+type PendingPressState = ResizeState & { startY: number }
+
+const DEFAULT_SIDEBAR_WIDTH = 256
+const MIN_SIDEBAR_WIDTH = 192
+const MIN_MAIN_WIDTH = 360
+const MAX_VIEWPORT_WIDTH_RATIO = .8
+const LONG_PRESS_DELAY_MS = 350
+const TOUCH_MOVE_THRESHOLD_PX = 8
 
 
-const SidebarComponent: FC<Props> = ({ children }) => (
-    <motion.div
-	layout="position"
-	transition={{ layout: { duration: .2, ease: 'easeOut' } }}
-	className="p-4 w-full md:w-64 md:h-full md:overflow-y-auto sidebar">
-      <Helmet>
-	<style>
-	  {`
+const storageKeyForSidebar = (sidebarKey: string, side: SidebarSide): string =>
+    `sidebar:${ sidebarKey }:${ side }:width`
+
+
+const getSidebarMaxWidth = (containerWidth: number): number => {
+  const viewportWidth =
+      typeof window === 'undefined' ? containerWidth : window.innerWidth
+  const viewportMaxWidth = Math.floor (viewportWidth * MAX_VIEWPORT_WIDTH_RATIO)
+  const containerMaxWidth = Math.floor (containerWidth - MIN_MAIN_WIDTH)
+  const dynamicMaxWidth = Math.min (viewportMaxWidth, containerMaxWidth)
+
+  return Math.max (MIN_SIDEBAR_WIDTH, dynamicMaxWidth)
+}
+
+
+const readStoredSidebarWidth = (
+    sidebarKey: string,
+    side: SidebarSide): number => {
+  if (typeof window === 'undefined')
+    return DEFAULT_SIDEBAR_WIDTH
+
+  const value = window.localStorage.getItem (storageKeyForSidebar (sidebarKey, side))
+  const width = value == null ? Number.NaN : Number (value)
+
+  return Number.isFinite (width) ? width : DEFAULT_SIDEBAR_WIDTH
+}
+
+
+const SidebarComponent: FC<Props> = ({
+    children,
+    className,
+    maxWidth,
+    onWidthChange,
+    sidebarKey,
+    side = 'left',
+}) => {
+  const rootRef = useRef<HTMLDivElement | null> (null)
+  const maxWidthRef = useRef (maxWidth)
+  const getContainerWidth = useCallback (() => {
+    const containerWidth = rootRef.current
+	?.closest ('[data-sidebar-container]')
+	?.clientWidth
+    ?? window.innerWidth
+    return containerWidth
+  }, [])
+  const getClampedWidth = useCallback ((
+      nextWidth: number,
+      containerWidth: number): number => {
+    const viewportWidth =
+	typeof window === 'undefined' ? containerWidth : window.innerWidth
+    const viewportMaxWidth = Math.floor (viewportWidth * MAX_VIEWPORT_WIDTH_RATIO)
+    const maxAllowedWidth =
+	maxWidthRef.current == null
+	? getSidebarMaxWidth (containerWidth)
+	: Math.max (
+	    MIN_SIDEBAR_WIDTH,
+	    Math.min (viewportMaxWidth, maxWidthRef.current))
+
+    return Math.min (maxAllowedWidth, Math.max (MIN_SIDEBAR_WIDTH, nextWidth))
+  }, [])
+
+  const [width, setWidth] = useState (() => (
+      typeof window === 'undefined'
+      ? DEFAULT_SIDEBAR_WIDTH
+      : getClampedWidth (
+	  readStoredSidebarWidth (sidebarKey, side),
+	  window.innerWidth)))
+  const [resizing, setResizing] = useState (false)
+  const widthRef = useRef (width)
+  const longPressTimerRef = useRef<ReturnType<typeof setTimeout> | null> (null)
+  const pendingPressRef = useRef<PendingPressState | null> (null)
+  const resizeRef = useRef<ResizeState | null> (null)
+  const bodyStyleRef = useRef<{ cursor: string, userSelect: string } | null> (null)
+
+  const clearLongPressTimer = useCallback (() => {
+    if (longPressTimerRef.current == null)
+      return
+
+    clearTimeout (longPressTimerRef.current)
+    longPressTimerRef.current = null
+  }, [])
+
+  const restoreBodyStyle = useCallback (() => {
+    if (bodyStyleRef.current == null)
+      return
+
+    document.body.style.cursor = bodyStyleRef.current.cursor
+    document.body.style.userSelect = bodyStyleRef.current.userSelect
+    bodyStyleRef.current = null
+  }, [])
+
+  const startResize = useCallback ((state: ResizeState) => {
+    clearLongPressTimer ()
+    pendingPressRef.current = null
+    resizeRef.current = state
+    setResizing (true)
+
+    if (bodyStyleRef.current == null)
+    {
+      bodyStyleRef.current = {
+	  cursor: document.body.style.cursor,
+	  userSelect: document.body.style.userSelect }
+    }
+
+    document.body.style.cursor = 'col-resize'
+    document.body.style.userSelect = 'none'
+  }, [clearLongPressTimer])
+
+  const finishResize = useCallback (() => {
+    clearLongPressTimer ()
+    pendingPressRef.current = null
+
+    const state = resizeRef.current
+    resizeRef.current = null
+
+    if (state != null)
+      window.localStorage.setItem (
+	  storageKeyForSidebar (sidebarKey, state.side),
+	  String (widthRef.current))
+
+    setResizing (false)
+    restoreBodyStyle ()
+  }, [clearLongPressTimer, restoreBodyStyle, sidebarKey])
+
+  const applyWidth = useCallback ((nextWidth: number) => {
+    if (nextWidth === widthRef.current)
+      return
+
+    widthRef.current = nextWidth
+    setWidth (nextWidth)
+  }, [])
+
+  useEffect (() => {
+    maxWidthRef.current = maxWidth
+    const containerWidth = getContainerWidth ()
+    const nextWidth = getClampedWidth (widthRef.current, containerWidth)
+    applyWidth (nextWidth)
+  }, [applyWidth, getClampedWidth, getContainerWidth, maxWidth])
+
+  const updateWidth = useCallback ((clientX: number) => {
+    const state = resizeRef.current
+    if (state == null)
+      return
+
+    const containerWidth = getContainerWidth ()
+    const delta = state.side === 'left'
+		  ? clientX - state.startX
+		  : state.startX - clientX
+    const nextWidth = getClampedWidth (state.startWidth + delta, containerWidth)
+    applyWidth (nextWidth)
+  }, [applyWidth, getClampedWidth, getContainerWidth])
+
+  const handlePointerDown = (ev: PointerEvent<HTMLDivElement>) => {
+    if (ev.pointerType !== 'mouse' && ev.pointerType !== 'touch')
+      return
+
+    if (ev.pointerType === 'mouse' && ev.button !== 0)
+      return
+
+    ev.preventDefault ()
+    ev.stopPropagation ()
+    ev.currentTarget.setPointerCapture (ev.pointerId)
+
+    const state = {
+	pointerId: ev.pointerId,
+	side,
+	startWidth: widthRef.current,
+	startX: ev.clientX }
+
+    if (ev.pointerType === 'mouse')
+    {
+      startResize (state)
+      return
+    }
+
+    pendingPressRef.current = { ...state, startY: ev.clientY }
+    clearLongPressTimer ()
+    longPressTimerRef.current = setTimeout (() => {
+      if (pendingPressRef.current != null)
+	startResize (pendingPressRef.current)
+    }, LONG_PRESS_DELAY_MS)
+  }
+
+  const handlePointerMove = (ev: PointerEvent<HTMLDivElement>) => {
+    ev.stopPropagation ()
+
+    if (resizeRef.current != null)
+    {
+      ev.preventDefault ()
+      updateWidth (ev.clientX)
+      return
+    }
+
+    const pendingPress = pendingPressRef.current
+    if (pendingPress == null || pendingPress.pointerId !== ev.pointerId)
+      return
+
+    const deltaX = ev.clientX - pendingPress.startX
+    const deltaY = ev.clientY - pendingPress.startY
+    const distance = Math.hypot (deltaX, deltaY)
+
+    if (distance >= TOUCH_MOVE_THRESHOLD_PX)
+    {
+      clearLongPressTimer ()
+      pendingPressRef.current = null
+    }
+  }
+
+  const handlePointerEnd = (ev: PointerEvent<HTMLDivElement>) => {
+    ev.stopPropagation ()
+
+    if (ev.currentTarget.hasPointerCapture (ev.pointerId))
+      ev.currentTarget.releasePointerCapture (ev.pointerId)
+
+    finishResize ()
+  }
+
+  const resetWidth = useCallback (() => {
+    const containerWidth = getContainerWidth ()
+    const nextWidth = getClampedWidth (DEFAULT_SIDEBAR_WIDTH, containerWidth)
+    applyWidth (nextWidth)
+    window.localStorage.removeItem (storageKeyForSidebar (sidebarKey, side))
+  }, [applyWidth, getClampedWidth, getContainerWidth, sidebarKey, side])
+
+  const handleDoubleClick = (ev: MouseEvent<HTMLDivElement>) => {
+    ev.preventDefault ()
+    ev.stopPropagation ()
+    resetWidth ()
+  }
+
+  useEffect (() => {
+    const containerWidth = getContainerWidth ()
+    const nextWidth = getClampedWidth (
+	readStoredSidebarWidth (sidebarKey, side),
+	containerWidth)
+    applyWidth (nextWidth)
+  }, [applyWidth, getClampedWidth, getContainerWidth, sidebarKey, side])
+
+  useEffect (() => {
+    const containerWidth = getContainerWidth ()
+    const nextWidth = getClampedWidth (widthRef.current, containerWidth)
+    applyWidth (nextWidth)
+  }, [applyWidth, getClampedWidth, getContainerWidth])
+
+  useEffect (() => {
+    if (typeof window === 'undefined')
+      return
+
+    const handleResize = () => {
+      const containerWidth = getContainerWidth ()
+      const nextWidth = getClampedWidth (widthRef.current, containerWidth)
+      applyWidth (nextWidth)
+    }
+
+    window.addEventListener ('resize', handleResize)
+    return () => window.removeEventListener ('resize', handleResize)
+  }, [applyWidth, getClampedWidth, getContainerWidth])
+
+  useEffect (() => {
+    onWidthChange?.(width)
+  }, [onWidthChange, width])
+
+  useEffect (() => () => {
+    clearLongPressTimer ()
+    restoreBodyStyle ()
+  }, [clearLongPressTimer, restoreBodyStyle])
+
+  const style = {
+      '--sidebar-width': `${ width }px` } as CSSProperties
+
+  return (
+      <motion.div
+	  ref={rootRef}
+	  layout="position"
+	  transition={{ layout: { duration: .2, ease: 'easeOut' } }}
+	  style={style}
+	  className={cn (
+	      'relative w-full md:w-[var(--sidebar-width)] md:shrink-0 md:h-full',
+	      className)}>
+	<Helmet>
+	  <style>
+	    {`
 	      .sidebar
 	      {
 		direction: rtl;
@@ -23,10 +323,34 @@ const SidebarComponent: FC<Props> = ({ children }) => (
 	      {
 		direction: ltr;
 	      }`}
-	</style>
-      </Helmet>
+	  </style>
+	</Helmet>
 
-      {children}
-    </motion.div>)
+	<div className="h-full overflow-y-auto p-4 sidebar">
+	  {children}
+	</div>
 
-export default SidebarComponent
+	<div
+	    role="separator"
+	    aria-orientation="vertical"
+	    aria-label="サイドバー幅"
+	    onPointerDown={handlePointerDown}
+	    onPointerMove={handlePointerMove}
+	    onPointerUp={handlePointerEnd}
+	    onPointerCancel={handlePointerEnd}
+	    onDoubleClick={handleDoubleClick}
+	    className={cn (
+		'hidden md:block absolute top-0 bottom-0 z-20 w-4 cursor-col-resize',
+		'touch-none select-none',
+		side === 'left' ? '-right-2' : '-left-2',
+		'before:absolute before:top-0 before:bottom-0 before:w-px',
+		'before:bg-neutral-500/0 hover:before:bg-neutral-500/30',
+		'before:transition-colors before:duration-150',
+		side === 'left'
+		? 'before:left-1/2'
+		: 'before:right-1/2',
+		resizing && 'before:bg-neutral-500/40')}/>
+      </motion.div>)
+}
+
+export default SidebarComponent

frontend/src/components/ui/button.tsx

@@ -10,41 +10,35 @@ const buttonVariants = cva (
     'rounded-md text-sm font-medium transition-colors',
     'focus-visible:outline-none focus-visible:ring-2 focus-visible:ring-slate-400',
     'disabled:pointer-events-none disabled:opacity-50',
-    '[&_svg]:pointer-events-none [&_svg]:size-4 [&_svg]:shrink-0',
-  ].join (' '),
+    '[&_svg]:pointer-events-none [&_svg]:size-4 [&_svg]:shrink-0'].join (' '),
   {
     variants: {
       variant: {
-        default:
-          'bg-slate-900 text-white hover:bg-slate-700 dark:bg-slate-100 dark:text-slate-900 dark:hover:bg-slate-300',
+	default:
+	  'bg-slate-900 text-white hover:bg-slate-700 dark:bg-slate-100 dark:text-slate-900 dark:hover:bg-slate-300',
 
-        destructive:
-          'bg-red-600 text-white hover:bg-red-700 dark:bg-red-700 dark:hover:bg-red-600',
+	destructive:
+	  'bg-red-600 text-white hover:bg-red-700 dark:bg-red-700 dark:hover:bg-red-600',
 
-        outline:
-          'border border-slate-300 bg-white text-slate-900 hover:bg-slate-100 dark:border-slate-700 dark:bg-slate-900 dark:text-slate-100 dark:hover:bg-slate-800',
+	outline:
+	  'border border-slate-300 bg-white text-slate-900 hover:bg-slate-100 dark:border-slate-700 dark:bg-slate-900 dark:text-slate-100 dark:hover:bg-slate-800',
 
-        secondary:
-          'bg-slate-100 text-slate-900 hover:bg-slate-200 dark:bg-slate-800 dark:text-slate-100 dark:hover:bg-slate-700',
+	secondary:
+	  'bg-slate-100 text-slate-900 hover:bg-slate-200 dark:bg-slate-800 dark:text-slate-100 dark:hover:bg-slate-700',
 
-        ghost:
-          'text-slate-900 hover:bg-slate-100 dark:text-slate-100 dark:hover:bg-slate-800',
+	ghost:
+	  'text-slate-900 hover:bg-slate-100 dark:text-slate-100 dark:hover:bg-slate-800',
 
-        link:
-          'text-blue-700 underline-offset-4 hover:underline dark:text-blue-300',
-      },
+	link:
+	  'text-blue-700 underline-offset-4 hover:underline dark:text-blue-300'},
       size: {
-        default: 'h-10 px-4 py-2',
-        sm:      'h-9 rounded-md px-3',
-        lg:      'h-11 rounded-md px-8',
-        icon:    'h-10 w-10',
-      },
-    },
+	default: 'h-10 px-4 py-2',
+	sm:      'h-9 rounded-md px-3',
+	lg:      'h-11 rounded-md px-8',
+	icon:    'h-10 w-10'}},
     defaultVariants: {
       variant: 'default',
-      size:    'default',
-    },
-  })
+      size:    'default'}})
 
 export interface ButtonProps
   extends React.ButtonHTMLAttributes<HTMLButtonElement>,
@@ -57,13 +51,11 @@ const Button = React.forwardRef<HTMLButtonElement, ButtonProps>(
     const Comp = asChild ? Slot : "button"
     return (
       <Comp
-        className={cn(buttonVariants({ variant, size, className }))}
-        ref={ref}
-        {...props}
-      />
-    )
-  }
-)
+	className={cn(buttonVariants({ variant, size, className }))}
+	ref={ref}
+	{...props}
+      />)
+  })
 Button.displayName = "Button"
 
 export { Button, buttonVariants }

frontend/src/components/ui/dialog.tsx

@@ -22,11 +22,9 @@ const DialogOverlay = React.forwardRef<
     ref={ref}
     className={cn(
       "fixed inset-0 z-50 bg-black/80 data-[state=open]:animate-in data-[state=closed]:animate-out data-[state=closed]:fade-out-0 data-[state=open]:fade-in-0",
-      className
-    )}
+      className)}
     {...props}
-  />
-))
+  />))
 DialogOverlay.displayName = DialogPrimitive.Overlay.displayName
 
 const DialogContent = React.forwardRef<
@@ -62,8 +60,7 @@ const DialogContent = React.forwardRef<
 	<span className="sr-only">閉ぢる</span>
       </DialogPrimitive.Close>
     </DialogPrimitive.Content>
-  </DialogPortal>
-))
+  </DialogPortal>))
 DialogContent.displayName = DialogPrimitive.Content.displayName
 
 const DialogHeader = ({
@@ -73,11 +70,9 @@ const DialogHeader = ({
   <div
     className={cn(
       "flex flex-col space-y-1.5 text-center sm:text-left",
-      className
-    )}
+      className)}
     {...props}
-  />
-)
+  />)
 DialogHeader.displayName = "DialogHeader"
 
 const DialogFooter = ({
@@ -87,11 +82,9 @@ const DialogFooter = ({
   <div
     className={cn(
       "flex flex-col-reverse sm:flex-row sm:justify-end sm:space-x-2",
-      className
-    )}
+      className)}
     {...props}
-  />
-)
+  />)
 DialogFooter.displayName = "DialogFooter"
 
 const DialogTitle = React.forwardRef<
@@ -102,11 +95,9 @@ const DialogTitle = React.forwardRef<
     ref={ref}
     className={cn(
       "text-lg font-semibold leading-none tracking-tight",
-      className
-    )}
+      className)}
     {...props}
-  />
-))
+  />))
 DialogTitle.displayName = DialogPrimitive.Title.displayName
 
 const DialogDescription = React.forwardRef<
@@ -117,8 +108,7 @@ const DialogDescription = React.forwardRef<
     ref={ref}
     className={cn("text-sm text-muted-foreground", className)}
     {...props}
-  />
-))
+  />))
 DialogDescription.displayName = DialogPrimitive.Description.displayName
 
 export {

frontend/src/components/ui/input.tsx

@@ -1,22 +1,19 @@
-import * as React from "react"
+import * as React from 'react'
 
-import { cn } from "@/lib/utils"
+import { cn } from '@/lib/utils'
 
-const Input = React.forwardRef<HTMLInputElement, React.ComponentProps<"input">>(
+const Input = React.forwardRef<HTMLInputElement, React.ComponentProps<'input'>>(
   ({ className, type, ...props }, ref) => {
     return (
       <input
-        type={type}
-        className={cn(
-          "flex h-10 w-full rounded-md border border-input bg-background px-3 py-2 text-base ring-offset-background file:border-0 file:bg-transparent file:text-sm file:font-medium file:text-foreground placeholder:text-muted-foreground focus-visible:outline-none focus-visible:ring-2 focus-visible:ring-ring focus-visible:ring-offset-2 disabled:cursor-not-allowed disabled:opacity-50 md:text-sm",
-          className
-        )}
-        ref={ref}
-        {...props}
-      />
-    )
-  }
-)
-Input.displayName = "Input"
+	type={type}
+	className={cn(
+	  'flex h-10 w-full rounded-md border border-input bg-background px-3 py-2 text-base ring-offset-background file:border-0 file:bg-transparent file:text-sm file:font-medium file:text-foreground placeholder:text-muted-foreground focus-visible:outline-none focus-visible:ring-2 focus-visible:ring-ring focus-visible:ring-offset-2 disabled:cursor-not-allowed disabled:opacity-50 md:text-sm',
+	  className)}
+	ref={ref}
+	{...props}
+      />)
+  })
+Input.displayName = 'Input'
 
 export { Input }

frontend/src/components/ui/switch.tsx

@@ -1,9 +1,9 @@
-"use client"
+'use client'
 
-import * as React from "react"
-import * as SwitchPrimitives from "@radix-ui/react-switch"
+import * as React from 'react'
+import * as SwitchPrimitives from '@radix-ui/react-switch'
 
-import { cn } from "@/lib/utils"
+import { cn } from '@/lib/utils'
 
 const Switch = React.forwardRef<
   React.ElementRef<typeof SwitchPrimitives.Root>,
@@ -11,19 +11,16 @@ const Switch = React.forwardRef<
 >(({ className, ...props }, ref) => (
   <SwitchPrimitives.Root
     className={cn(
-      "peer inline-flex h-6 w-11 shrink-0 cursor-pointer items-center rounded-full border-2 border-transparent transition-colors focus-visible:outline-none focus-visible:ring-2 focus-visible:ring-ring focus-visible:ring-offset-2 focus-visible:ring-offset-background disabled:cursor-not-allowed disabled:opacity-50 data-[state=checked]:bg-primary data-[state=unchecked]:bg-input",
-      className
-    )}
+      'peer inline-flex h-6 w-11 shrink-0 cursor-pointer items-center rounded-full border-2 border-transparent transition-colors focus-visible:outline-none focus-visible:ring-2 focus-visible:ring-ring focus-visible:ring-offset-2 focus-visible:ring-offset-background disabled:cursor-not-allowed disabled:opacity-50 data-[state=checked]:bg-primary data-[state=unchecked]:bg-input',
+      className)}
     {...props}
     ref={ref}
   >
     <SwitchPrimitives.Thumb
       className={cn(
-        "pointer-events-none block h-5 w-5 rounded-full bg-background shadow-lg ring-0 transition-transform data-[state=checked]:translate-x-5 data-[state=unchecked]:translate-x-0"
-      )}
+	'pointer-events-none block h-5 w-5 rounded-full bg-background shadow-lg ring-0 transition-transform data-[state=checked]:translate-x-5 data-[state=unchecked]:translate-x-0')}
     />
-  </SwitchPrimitives.Root>
-))
+  </SwitchPrimitives.Root>))
 Switch.displayName = SwitchPrimitives.Root.displayName
 
 export { Switch }

frontend/src/components/ui/toast.tsx

@@ -1,129 +1,115 @@
-"use client"
-
-import * as React from "react"
-import * as ToastPrimitives from "@radix-ui/react-toast"
-import { cva, type VariantProps } from "class-variance-authority"
-import { X } from "lucide-react"
-
-import { cn } from "@/lib/utils"
-
-const ToastProvider = ToastPrimitives.Provider
-
-const ToastViewport = React.forwardRef<
-  React.ElementRef<typeof ToastPrimitives.Viewport>,
-  React.ComponentPropsWithoutRef<typeof ToastPrimitives.Viewport>
->(({ className, ...props }, ref) => (
-  <ToastPrimitives.Viewport
-    ref={ref}
-    className={cn(
-      "fixed top-0 z-[100] flex max-h-screen w-full flex-col-reverse p-4 sm:bottom-0 sm:right-0 sm:top-auto sm:flex-col md:max-w-[420px]",
-      className
-    )}
-    {...props}
-  />
-))
-ToastViewport.displayName = ToastPrimitives.Viewport.displayName
-
-const toastVariants = cva(
-  "group pointer-events-auto relative flex w-full items-center justify-between space-x-4 overflow-hidden rounded-md border p-6 pr-8 shadow-lg transition-all data-[swipe=cancel]:translate-x-0 data-[swipe=end]:translate-x-[var(--radix-toast-swipe-end-x)] data-[swipe=move]:translate-x-[var(--radix-toast-swipe-move-x)] data-[swipe=move]:transition-none data-[state=open]:animate-in data-[state=closed]:animate-out data-[swipe=end]:animate-out data-[state=closed]:fade-out-80 data-[state=closed]:slide-out-to-right-full data-[state=open]:slide-in-from-top-full data-[state=open]:sm:slide-in-from-bottom-full",
-  {
-    variants: {
-      variant: {
-        default: "border bg-background text-foreground",
-        destructive:
-          "destructive group border-destructive bg-destructive text-destructive-foreground",
-      },
-    },
-    defaultVariants: {
-      variant: "default",
-    },
-  }
-)
-
-const Toast = React.forwardRef<
-  React.ElementRef<typeof ToastPrimitives.Root>,
-  React.ComponentPropsWithoutRef<typeof ToastPrimitives.Root> &
-    VariantProps<typeof toastVariants>
->(({ className, variant, ...props }, ref) => {
-  return (
-    <ToastPrimitives.Root
-      ref={ref}
-      className={cn(toastVariants({ variant }), className)}
-      {...props}
-    />
-  )
-})
-Toast.displayName = ToastPrimitives.Root.displayName
-
-const ToastAction = React.forwardRef<
-  React.ElementRef<typeof ToastPrimitives.Action>,
-  React.ComponentPropsWithoutRef<typeof ToastPrimitives.Action>
->(({ className, ...props }, ref) => (
-  <ToastPrimitives.Action
-    ref={ref}
-    className={cn(
-      "inline-flex h-8 shrink-0 items-center justify-center rounded-md border bg-transparent px-3 text-sm font-medium ring-offset-background transition-colors hover:bg-secondary focus:outline-none focus:ring-2 focus:ring-ring focus:ring-offset-2 disabled:pointer-events-none disabled:opacity-50 group-[.destructive]:border-muted/40 group-[.destructive]:hover:border-destructive/30 group-[.destructive]:hover:bg-destructive group-[.destructive]:hover:text-destructive-foreground group-[.destructive]:focus:ring-destructive",
-      className
-    )}
-    {...props}
-  />
-))
-ToastAction.displayName = ToastPrimitives.Action.displayName
-
-const ToastClose = React.forwardRef<
-  React.ElementRef<typeof ToastPrimitives.Close>,
-  React.ComponentPropsWithoutRef<typeof ToastPrimitives.Close>
->(({ className, ...props }, ref) => (
-  <ToastPrimitives.Close
-    ref={ref}
-    className={cn(
-      "absolute right-2 top-2 rounded-md p-1 text-foreground/50 opacity-0 transition-opacity hover:text-foreground focus:opacity-100 focus:outline-none focus:ring-2 group-hover:opacity-100 group-[.destructive]:text-red-300 group-[.destructive]:hover:text-red-50 group-[.destructive]:focus:ring-red-400 group-[.destructive]:focus:ring-offset-red-600",
-      className
-    )}
-    toast-close=""
-    {...props}
-  >
-    <X className="h-4 w-4" />
-  </ToastPrimitives.Close>
-))
-ToastClose.displayName = ToastPrimitives.Close.displayName
-
-const ToastTitle = React.forwardRef<
-  React.ElementRef<typeof ToastPrimitives.Title>,
-  React.ComponentPropsWithoutRef<typeof ToastPrimitives.Title>
->(({ className, ...props }, ref) => (
-  <ToastPrimitives.Title
-    ref={ref}
-    className={cn("text-sm font-semibold", className)}
-    {...props}
-  />
-))
-ToastTitle.displayName = ToastPrimitives.Title.displayName
-
-const ToastDescription = React.forwardRef<
-  React.ElementRef<typeof ToastPrimitives.Description>,
-  React.ComponentPropsWithoutRef<typeof ToastPrimitives.Description>
->(({ className, ...props }, ref) => (
-  <ToastPrimitives.Description
-    ref={ref}
-    className={cn("text-sm opacity-90", className)}
-    {...props}
-  />
-))
-ToastDescription.displayName = ToastPrimitives.Description.displayName
-
-type ToastProps = React.ComponentPropsWithoutRef<typeof Toast>
-
-type ToastActionElement = React.ReactElement<typeof ToastAction>
-
-export {
-  type ToastProps,
-  type ToastActionElement,
-  ToastProvider,
-  ToastViewport,
-  Toast,
-  ToastTitle,
-  ToastDescription,
-  ToastClose,
-  ToastAction,
-}
+"use client"
+
+import * as React from "react"
+import * as ToastPrimitives from "@radix-ui/react-toast"
+import { cva, type VariantProps } from "class-variance-authority"
+import { X } from "lucide-react"
+
+import { cn } from "@/lib/utils"
+
+const ToastProvider = ToastPrimitives.Provider
+
+const ToastViewport = React.forwardRef<
+  React.ElementRef<typeof ToastPrimitives.Viewport>,
+  React.ComponentPropsWithoutRef<typeof ToastPrimitives.Viewport>
+>(({ className, ...props }, ref) => (
+  <ToastPrimitives.Viewport
+    ref={ref}
+    className={cn(
+      "fixed top-0 z-[100] flex max-h-screen w-full flex-col-reverse p-4 sm:bottom-0 sm:right-0 sm:top-auto sm:flex-col md:max-w-[420px]",
+      className
)}
+    {...props}
+  />
))
+ToastViewport.displayName = ToastPrimitives.Viewport.displayName
+
+const toastVariants = cva(
+  "group pointer-events-auto relative flex w-full items-center justify-between space-x-4 overflow-hidden rounded-md border p-6 pr-8 shadow-lg transition-all data-[swipe=cancel]:translate-x-0 data-[swipe=end]:translate-x-[var(--radix-toast-swipe-end-x)] data-[swipe=move]:translate-x-[var(--radix-toast-swipe-move-x)] data-[swipe=move]:transition-none data-[state=open]:animate-in data-[state=closed]:animate-out data-[swipe=end]:animate-out data-[state=closed]:fade-out-80 data-[state=closed]:slide-out-to-right-full data-[state=open]:slide-in-from-top-full data-[state=open]:sm:slide-in-from-bottom-full",
+  {
+    variants: {
+      variant: {
+	default: "border bg-background text-foreground",
+	destructive:
+	  "destructive group border-destructive bg-destructive text-destructive-foreground",
+      },
+    },
+    defaultVariants: { variant: "default" } }
)
+
+const Toast = React.forwardRef<
+  React.ElementRef<typeof ToastPrimitives.Root>,
+  React.ComponentPropsWithoutRef<typeof ToastPrimitives.Root> &
+    VariantProps<typeof toastVariants>
+>(({ className, variant, ...props }, ref) => {
+  return (
+    <ToastPrimitives.Root
+      ref={ref}
+      className={cn(toastVariants({ variant }), className)}
+      {...props}
+    />
)
})
+Toast.displayName = ToastPrimitives.Root.displayName
+
+const ToastAction = React.forwardRef<
+  React.ElementRef<typeof ToastPrimitives.Action>,
+  React.ComponentPropsWithoutRef<typeof ToastPrimitives.Action>
+>(({ className, ...props }, ref) => (
+  <ToastPrimitives.Action
+    ref={ref}
+    className={cn(
+      "inline-flex h-8 shrink-0 items-center justify-center rounded-md border bg-transparent px-3 text-sm font-medium ring-offset-background transition-colors hover:bg-secondary focus:outline-none focus:ring-2 focus:ring-ring focus:ring-offset-2 disabled:pointer-events-none disabled:opacity-50 group-[.destructive]:border-muted/40 group-[.destructive]:hover:border-destructive/30 group-[.destructive]:hover:bg-destructive group-[.destructive]:hover:text-destructive-foreground group-[.destructive]:focus:ring-destructive",
+      className
)}
+    {...props}
+  />
))
+ToastAction.displayName = ToastPrimitives.Action.displayName
+
+const ToastClose = React.forwardRef<
+  React.ElementRef<typeof ToastPrimitives.Close>,
+  React.ComponentPropsWithoutRef<typeof ToastPrimitives.Close>
+>(({ className, ...props }, ref) => (
+  <ToastPrimitives.Close
+    ref={ref}
+    className={cn(
+      "absolute right-2 top-2 rounded-md p-1 text-foreground/50 opacity-0 transition-opacity hover:text-foreground focus:opacity-100 focus:outline-none focus:ring-2 group-hover:opacity-100 group-[.destructive]:text-red-300 group-[.destructive]:hover:text-red-50 group-[.destructive]:focus:ring-red-400 group-[.destructive]:focus:ring-offset-red-600",
+      className
)}
+    toast-close=""
+    {...props}
+  >
+    <X className="h-4 w-4" />
+  </ToastPrimitives.Close>
))
+ToastClose.displayName = ToastPrimitives.Close.displayName
+
+const ToastTitle = React.forwardRef<
+  React.ElementRef<typeof ToastPrimitives.Title>,
+  React.ComponentPropsWithoutRef<typeof ToastPrimitives.Title>
+>(({ className, ...props }, ref) => (
+  <ToastPrimitives.Title
+    ref={ref}
+    className={cn("text-sm font-semibold", className)}
+    {...props}
+  />
))
+ToastTitle.displayName = ToastPrimitives.Title.displayName
+
+const ToastDescription = React.forwardRef<
+  React.ElementRef<typeof ToastPrimitives.Description>,
+  React.ComponentPropsWithoutRef<typeof ToastPrimitives.Description>
+>(({ className, ...props }, ref) => (
+  <ToastPrimitives.Description
+    ref={ref}
+    className={cn("text-sm opacity-90", className)}
+    {...props}
+  />
))
+ToastDescription.displayName = ToastPrimitives.Description.displayName
+
+type ToastProps = React.ComponentPropsWithoutRef<typeof Toast>
+
+type ToastActionElement = React.ReactElement<typeof ToastAction>
+
+export {
+  type ToastProps,
+  type ToastActionElement,
+  ToastProvider,
+  ToastViewport,
+  Toast,
+  ToastTitle,
+  ToastDescription,
+  ToastClose,
+  ToastAction,
+}

frontend/src/components/ui/toaster.tsx

@@ -1,31 +1,30 @@
-'use client'
-
-import { useToast } from '@/components/ui/use-toast'
-import { Toast,
-	 ToastClose,
-	 ToastDescription,
-	 ToastProvider,
-	 ToastTitle,
-	 ToastViewport } from '@/components/ui/toast'
-
-
-export const Toaster = () => {
-  const { toasts } = useToast ()
-
-  return (
-    <ToastProvider>
-      {toasts.map (({ id, title, description, action, ...props }) => (
-	  <Toast key={id}
-		 className="bg-gray-300/80 dark:bg-gray-700/80"
-		 {...props}>
-	    <div className="grid gap-1">
-	      {title && <ToastTitle>{title}</ToastTitle>}
-	      {description && <ToastDescription>{description}</ToastDescription>}
-	    </div>
-	    {action}
-	    <ToastClose />
-	  </Toast>))}
-      <ToastViewport />
-    </ToastProvider>
-  )
-}
+'use client'
+
+import { useToast } from '@/components/ui/use-toast'
+import { Toast,
+	 ToastClose,
+	 ToastDescription,
+	 ToastProvider,
+	 ToastTitle,
+	 ToastViewport } from '@/components/ui/toast'
+
+
+export const Toaster = () => {
+  const { toasts } = useToast ()
+
+  return (
+    <ToastProvider>
+      {toasts.map (({ id, title, description, action, ...props }) => (
+	  <Toast key={id}
+		 className="bg-gray-300/80 dark:bg-gray-700/80"
+		 {...props}>
+	    <div className="grid gap-1">
+	      {title && <ToastTitle>{title}</ToastTitle>}
+	      {description && <ToastDescription>{description}</ToastDescription>}
+	    </div>
+	    {action}
+	    <ToastClose />
+	  </Toast>))}
+      <ToastViewport />
+    </ToastProvider>
)
+}

frontend/src/components/ui/use-toast.tsx

@@ -58,8 +58,7 @@ const addToRemoveQueue = (toastId: string) => {
     toastTimeouts.delete(toastId)
     dispatch({
       type: "REMOVE_TOAST",
-      toastId: toastId,
-    })
+      toastId: toastId})
   }, TOAST_REMOVE_DELAY)
 
   toastTimeouts.set(toastId, timeout)
@@ -69,17 +68,14 @@ export const reducer = (state: State, action: Action): State => {
   switch (action.type) {
     case "ADD_TOAST":
       return {
-        ...state,
-        toasts: [action.toast, ...state.toasts].slice(0, TOAST_LIMIT),
-      }
+	...state,
+	toasts: [action.toast, ...state.toasts].slice(0, TOAST_LIMIT)}
 
     case "UPDATE_TOAST":
       return {
-        ...state,
-        toasts: state.toasts.map((t) =>
-          t.id === action.toast.id ? { ...t, ...action.toast } : t
-        ),
-      }
+	...state,
+	toasts: state.toasts.map((t) =>
+	  t.id === action.toast.id ? { ...t, ...action.toast } : t)}
 
     case "DISMISS_TOAST": {
       const { toastId } = action
@@ -87,36 +83,31 @@ export const reducer = (state: State, action: Action): State => {
       // ! Side effects ! - This could be extracted into a dismissToast() action,
       // but I'll keep it here for simplicity
       if (toastId) {
-        addToRemoveQueue(toastId)
+	addToRemoveQueue(toastId)
       } else {
-        state.toasts.forEach((toast) => {
-          addToRemoveQueue(toast.id)
-        })
+	state.toasts.forEach((toast) => {
+	  addToRemoveQueue(toast.id)
+	})
       }
 
       return {
-        ...state,
-        toasts: state.toasts.map((t) =>
-          t.id === toastId || toastId === undefined
-            ? {
-                ...t,
-                open: false,
-              }
-            : t
-        ),
-      }
+	...state,
+	toasts: state.toasts.map((t) =>
+	  t.id === toastId || toastId === undefined
+	    ? {
+		...t,
+		open: false}
+	    : t)}
     }
     case "REMOVE_TOAST":
       if (action.toastId === undefined) {
-        return {
-          ...state,
-          toasts: [],
-        }
+	return {
+	  ...state,
+	  toasts: []}
       }
       return {
-        ...state,
-        toasts: state.toasts.filter((t) => t.id !== action.toastId),
-      }
+	...state,
+	toasts: state.toasts.filter((t) => t.id !== action.toastId)}
   }
 }
 
@@ -139,8 +130,7 @@ function toast({ ...props }: Toast) {
   const update = (props: ToasterToast) =>
     dispatch({
       type: "UPDATE_TOAST",
-      toast: { ...props, id },
-    })
+      toast: { ...props, id }})
   const dismiss = () => dispatch({ type: "DISMISS_TOAST", toastId: id })
 
   dispatch({
@@ -150,16 +140,13 @@ function toast({ ...props }: Toast) {
       id,
       open: true,
       onOpenChange: (open) => {
-        if (!open) dismiss()
-      },
-    },
-  })
+	if (!open) dismiss()
+      }}})
 
   return {
     id: id,
     dismiss,
-    update,
-  }
+    update}
 }
 
 function useToast() {
@@ -170,7 +157,7 @@ function useToast() {
     return () => {
       const index = listeners.indexOf(setState)
       if (index > -1) {
-        listeners.splice(index, 1)
+	listeners.splice(index, 1)
       }
     }
   }, [state])
@@ -178,8 +165,7 @@ function useToast() {
   return {
     ...state,
     toast,
-    dismiss: (toastId?: string) => dispatch({ type: "DISMISS_TOAST", toastId }),
-  }
+    dismiss: (toastId?: string) => dispatch({ type: "DISMISS_TOAST", toastId })}
 }
 
 export { useToast, toast }

frontend/src/config.sample.ts

@@ -3,8 +3,7 @@ const ENV: string = 'development'
 
 const config = {
   API_BASE_URL: ENV === 'production' ? 'https://hub.nizika.monster/api' : 'http://localhost:3002',
-  SITE_TITLE:   'ぼざクリ タグ広場'
-}
+  SITE_TITLE:   'ぼざクリ タグ広場'}
 
 export const API_BASE_URL = config.API_BASE_URL
 export const SITE_TITLE = config.SITE_TITLE

frontend/src/consts.ts

@@ -10,8 +10,7 @@ export const CATEGORIES = [
     'general',
     'material',
     'meta',
-    'nico',
-    ] as const
+    'nico'] as const
 
 export const CATEGORY_NAMES: Record<Category, string> = {
     deerjikist: 'ニジラー',
@@ -20,16 +19,14 @@ export const CATEGORY_NAMES: Record<Category, string> = {
     general:    '一般',
     material:   '素材',
     meta:       'メタタグ',
-    nico:       'ニコニコタグ',
-    } as const
+    nico:       'ニコニコタグ'} as const
 
 export const FETCH_POSTS_ORDER_FIELDS = [
     'title',
     'url',
     'original_created_at',
     'created_at',
-    'updated_at',
-    ] as const
+    'updated_at'] as const
 
 export const PLATFORMS = ['nico', 'youtube'] as const
 
@@ -43,13 +40,11 @@ export const TAG_COLOUR = {
     general:    'cyan',
     material:   'orange',
     meta:       'yellow',
-    nico:       'gray',
-    } as const satisfies Record<Category, string>
+    nico:       'gray'} as const satisfies Record<Category, string>
 
 export const USER_ROLES = ['admin', 'member', 'guest'] as const
 
 export const ViewFlagBehavior = {
     OnShowedDetail: 1,
     OnClickedLink:  2,
-    NotAuto:        3,
-    } as const
+    NotAuto:        3} as const

frontend/src/index.css

@@ -132,3 +132,20 @@ body
   0%, 100% { color: #f87171; }
   50% { color: #60a5fa; }
 }
+
+.tag-marquee
+{
+  position: relative;
+}
+
+.tag-marquee__animated
+{
+  position: absolute;
+  inset: 0 auto 0 0;
+  min-width: 100%;
+  width: max-content;
+  opacity: 0;
+  pointer-events: none;
+  white-space: nowrap;
+  will-change: transform;
+}

frontend/src/lib/api.ts

@@ -23,8 +23,7 @@ const apiP = async <T> (
     method: 'post' | 'put' | 'patch',
     path:   string,
     body?:  unknown,
-    opt?:   Opt,
-): Promise<T> => {
+    opt?:   Opt): Promise<T> => {
   const res = await client[method] (path, body ?? { }, withUserCode (opt))
   if (opt?.responseType === 'blob')
     return res.data as T
@@ -34,8 +33,7 @@ const apiP = async <T> (
 
 export const apiGet = async <T> (
     path: string,
-    opt?: Opt,
-): Promise<T> => {
+    opt?: Opt): Promise<T> => {
   const res = await client.get (path, withUserCode (opt))
   if (opt?.responseType === 'blob')
     return res.data as T
@@ -46,28 +44,24 @@ export const apiGet = async <T> (
 export const apiPost = async <T> (
     path:   string,
     body?:  unknown,
-    opt?:   Opt,
-): Promise<T> => apiP ('post', path, body, opt)
+    opt?:   Opt): Promise<T> => apiP ('post', path, body, opt)
 
 
 export const apiPut = async <T> (
     path:   string,
     body?:  unknown,
-    opt?:   Opt,
-): Promise<T> => apiP ('put', path, body, opt)
+    opt?:   Opt): Promise<T> => apiP ('put', path, body, opt)
 
 
 export const apiPatch = async <T> (
     path:   string,
     body?:  unknown,
-    opt?:   Opt,
-): Promise<T> => apiP ('patch', path, body, opt)
+    opt?:   Opt): Promise<T> => apiP ('patch', path, body, opt)
 
 
 export const apiDelete = async <T = void> (
     path: string,
-    opt?: Opt,
-): Promise<T> => {
+    opt?: Opt): Promise<T> => {
   const res = await client.delete (path, withUserCode (opt))
   if (res.data == null || res.data === '')
     return undefined as T

frontend/src/lib/gekanator.ts

@@ -104,8 +104,7 @@ export type BuildGekanatorQuestionsOptions = {
 
 
 export const normalizeTitleLengthCondition = (
-    condition:  GekanatorQuestionCondition,
-): GekanatorQuestionCondition => {
+    condition:  GekanatorQuestionCondition): GekanatorQuestionCondition => {
   switch (condition.type)
   {
   case 'title-length-greater-than':
@@ -119,8 +118,7 @@ export const normalizeTitleLengthCondition = (
 
 
 export const titleLengthMinimumForCondition = (
-    condition:  GekanatorQuestionCondition,
-): number | null => {
+    condition:  GekanatorQuestionCondition): number | null => {
   switch (condition.type)
   {
   case 'title-length-at-least':
@@ -134,8 +132,7 @@ export const titleLengthMinimumForCondition = (
 
 
 export const questionIdForCondition = (
-    condition:  NonPostSimilarityCondition,
-): string => {
+    condition:  NonPostSimilarityCondition): string => {
   switch (condition.type)
   {
   case 'tag':
@@ -161,8 +158,7 @@ export const questionIdForCondition = (
 
 const directExampleAnswerFor = (
     question:  StoredGekanatorQuestion,
-    post:      Post,
-): GekanatorAnswerValue | null => {
+    post:      Post): GekanatorAnswerValue | null => {
   if (question.kind !== 'post_similarity' && question.kind !== 'tag')
     return null
 
@@ -178,15 +174,13 @@ const directExampleAnswerFor = (
 
 
 export const isLearnedSemanticQuestion = (
-    question:  StoredGekanatorQuestion | GekanatorQuestion,
-): boolean =>
+    question:  StoredGekanatorQuestion | GekanatorQuestion): boolean =>
     question.kind === 'post_similarity'
     && question.source === 'user_suggested'
 
 
 export const learnedSemanticSideForAnswer = (
-    answer:  GekanatorAnswerValue | null,
-): LearnedSemanticSide => {
+    answer:  GekanatorAnswerValue | null): LearnedSemanticSide => {
   if (answer === 'yes' || answer === 'partial')
     return 'positive'
 
@@ -314,8 +308,7 @@ const questionableTag = (post: Post, key: string): boolean => {
 
 const questionMatches = (
     post:       Post,
-    question:   StoredGekanatorQuestion,
-): boolean => {
+    question:   StoredGekanatorQuestion): boolean => {
   const directAnswer = directExampleAnswerFor (question, post)
   if (directAnswer)
     return question.kind === 'post_similarity'
@@ -350,8 +343,7 @@ const questionMatches = (
 
 export const expectedAnswerForQuestion = (
     question:  StoredGekanatorQuestion | GekanatorQuestion | undefined,
-    post:      Post | null,
-): GekanatorAnswerValue | null => {
+    post:      Post | null): GekanatorAnswerValue | null => {
   if (!(question) || !(post))
     return null
 
@@ -382,14 +374,12 @@ export const expectedAnswerForQuestion = (
 
 export const learnedSemanticSideForPost = (
     question:  StoredGekanatorQuestion | GekanatorQuestion | undefined,
-    post:      Post | null,
-): LearnedSemanticSide =>
+    post:      Post | null): LearnedSemanticSide =>
     learnedSemanticSideForAnswer (expectedAnswerForQuestion (question, post))
 
 
 export const restoreGekanatorQuestion = (
-    question:  StoredGekanatorQuestion,
-): GekanatorQuestion => {
+    question:  StoredGekanatorQuestion): GekanatorQuestion => {
   const normalizedCondition = normalizeTitleLengthCondition (question.condition)
   const normalizedQuestion = {
       ...question,
@@ -408,8 +398,7 @@ export const restoreGekanatorQuestion = (
 
 
 export const storeGekanatorQuestion = (
-    question:  GekanatorQuestion,
-): StoredGekanatorQuestion => ({
+    question:  GekanatorQuestion): StoredGekanatorQuestion => ({
   id: question.condition.type === 'title-length-greater-than'
       ? `title:length-at-least:${ question.condition.length + 1 }`
       : question.id,
@@ -436,8 +425,7 @@ export const fetchGekanatorQuestions = async (): Promise<StoredGekanatorQuestion
 
 export const fetchGekanatorExtraQuestions = async (
     gameId:  number,
-    nonce?: string,
-): Promise<GekanatorExtraQuestion[]> => {
+    nonce?: string): Promise<GekanatorExtraQuestion[]> => {
   const data = await apiGet<{ questions: GekanatorExtraQuestion[] }> (
       `/gekanator/games/${ gameId }/extra_questions`,
       { params: nonce ? { nonce } : undefined })
@@ -447,8 +435,7 @@ export const fetchGekanatorExtraQuestions = async (
 
 export const buildGekanatorQuestions = (
     posts:    Post[],
-    options:  BuildGekanatorQuestionsOptions = { },
-): GekanatorQuestion[] => {
+    options:  BuildGekanatorQuestionsOptions = { }): GekanatorQuestion[] => {
   const {
       includeTitleContains = true,
       tagQuestionCap = 192,
@@ -490,8 +477,7 @@ export const buildGekanatorQuestions = (
 
   const usefulEntries = <T extends string | number> (
       counts:  Map<T, number>,
-      cap:     number,
-  ) =>
+      cap:     number) =>
       [...counts.entries ()]
       .filter (([, count]) => count > 0 && count < posts.length)
       .sort ((a, b) => Math.abs (posts.length / 2 - a[1])

frontend/src/lib/gekanatorCandidateRecovery.ts

@@ -32,8 +32,7 @@ export const candidatePostsFor = (
 				   answers:                 GekanatorAnswerLog[]
 				   softenedQuestionIds:     Set<string>
 				   rejectedPostIds:         Set<number>
-				   recoveredCandidatePosts: Map<number, RecoveredCandidateState> },
-): Post[] => {
+				   recoveredCandidatePosts: Map<number, RecoveredCandidateState> }): Post[] => {
   const questionById = new Map (questions.map (question => [question.id, question]))
 
   return posts.filter (post => {
@@ -76,8 +75,7 @@ export const candidatePostsFor = (
 export const hardFilteredPostsForAnswer = (
     { posts, question, answer }: { posts:     Post[]
 				   question:  GekanatorQuestion
-				   answer:    GekanatorAnswerValue },
-): Post[] => {
+				   answer:    GekanatorAnswerValue }): Post[] => {
   if (!(questionSupportsAnswerBasedHardFiltering (question)))
     return posts
 
@@ -98,8 +96,7 @@ const concreteAnswerOptions: GekanatorAnswerValue[] = ['yes', 'no', 'partial', '
 
 export const allConcreteAnswerOptionsExhausted = (
     posts:      Post[],
-    question:   GekanatorQuestion | null,
-): boolean => {
+    question:   GekanatorQuestion | null): boolean => {
   if (!(question))
     return false
 
@@ -125,8 +122,7 @@ export const recoverCandidatePosts = (
 			     recoveredCandidatePosts: Map<number, RecoveredCandidateState>
 			     eligiblePostIds:         Set<number>
 			     answerCountAtRecovery:   number
-			     recoveryStepCount:       number },
-): { recoveredCandidatePosts: Map<number, RecoveredCandidateState>
+			     recoveryStepCount:       number }): { recoveredCandidatePosts: Map<number, RecoveredCandidateState>
      recoveryStepCount:       number } | null => {
   const recovered = new Map (recoveredCandidatePosts)
   const targetSize = nextRecoveryTargetSize (recoveryStepCount)

frontend/src/lib/gekanatorQuestionFilters.ts

@@ -8,8 +8,7 @@ import type {
 
 
 export const monthForCondition = (
-    condition:  GekanatorQuestion['condition'],
-): number | null => {
+    condition:  GekanatorQuestion['condition']): number | null => {
   if (condition.type === 'original-month')
     return condition.month
 
@@ -24,8 +23,7 @@ export const monthForCondition = (
 const isTitleLengthContradiction = (
     candidate:  GekanatorQuestion['condition'],
     previous:   GekanatorQuestion['condition'],
-    answer:     GekanatorAnswerValue,
-): boolean => {
+    answer:     GekanatorAnswerValue): boolean => {
   const candidateLength = titleLengthMinimumForCondition (candidate)
   const previousLength = titleLengthMinimumForCondition (previous)
   if (candidateLength === null || previousLength === null)
@@ -45,8 +43,7 @@ const isTitleLengthContradiction = (
 
 const isQuestionRedundantAfterAnswers = (
     question:  GekanatorQuestion,
-    answers:   GekanatorAnswerLog[],
-): boolean => answers.some (answer => {
+    answers:   GekanatorAnswerLog[]): boolean => answers.some (answer => {
   const previous = answer.questionCondition
   return previous !== undefined
       && isTitleLengthContradiction (question.condition, previous, answer.answer)
@@ -56,8 +53,7 @@ const isQuestionRedundantAfterAnswers = (
 const isSourceFactBlocked = (
     candidate:  GekanatorQuestion['condition'],
     previous:   GekanatorQuestion['condition'],
-    answer:     GekanatorAnswerValue,
-): boolean => {
+    answer:     GekanatorAnswerValue): boolean => {
   if (candidate.type !== 'source' || previous.type !== 'source')
     return false
 
@@ -76,8 +72,7 @@ const isSourceFactBlocked = (
 const isOriginalYearFactBlocked = (
     candidate:  GekanatorQuestion['condition'],
     previous:   GekanatorQuestion['condition'],
-    answer:     GekanatorAnswerValue,
-): boolean => {
+    answer:     GekanatorAnswerValue): boolean => {
   if (candidate.type !== 'original-year' || previous.type !== 'original-year')
     return false
 
@@ -96,8 +91,7 @@ const isOriginalYearFactBlocked = (
 const isOriginalMonthFactBlocked = (
     candidate:  GekanatorQuestion['condition'],
     previous:   GekanatorQuestion['condition'],
-    answer:     GekanatorAnswerValue,
-): boolean => {
+    answer:     GekanatorAnswerValue): boolean => {
   switch (answer)
   {
   case 'yes':
@@ -143,8 +137,7 @@ const isOriginalMonthFactBlocked = (
 const isFactQuestionBlocked = (
     candidate:  GekanatorQuestion['condition'],
     previous:   GekanatorQuestion['condition'],
-    answer:     GekanatorAnswerValue,
-): boolean => {
+    answer:     GekanatorAnswerValue): boolean => {
   if (!(answer === 'yes' || answer === 'no'))
     return false
 
@@ -156,8 +149,7 @@ const isFactQuestionBlocked = (
 
 export const isQuestionHardFilteredAfterAnswers = (
     question:  GekanatorQuestion,
-    answers:   GekanatorAnswerLog[],
-): boolean => answers.some (answer => {
+    answers:   GekanatorAnswerLog[]): boolean => answers.some (answer => {
   const previous = answer.questionCondition
   if (previous === undefined)
     return false

frontend/src/lib/materials.ts

@@ -0,0 +1,139 @@
+import { apiGet, isApiError, apiPost, apiPut } from '@/lib/api'
+
+import type { Material,
+	      MaterialIndexResponse,
+	      MaterialVersion,
+	      FetchMaterialsParams,
+	      MaterialFilter,
+	      MaterialSyncSuppression,
+	      MaterialSidebarTag,
+	      MaterialTagTree } from '@/types'
+
+export type FetchMaterialTreeParams = {
+    parentId?:       number | null
+    materialFilter:  MaterialFilter }
+
+export type MaterialSyncSuppressionResponse = { suppressions: MaterialSyncSuppression[] }
+
+export type MaterialChangesResponse = {
+    versions: MaterialVersion[]
+    count:    number }
+
+const MATERIAL_FILTERS: MaterialFilter[] = ['present', 'missing', 'any']
+
+
+export const parseMaterialFilter = (
+    value: unknown,
+    fallback: MaterialFilter = 'present',
+): MaterialFilter =>
+    typeof value === 'string' && MATERIAL_FILTERS.includes (value as MaterialFilter)
+    ? value as MaterialFilter
+    : fallback
+
+
+export const fetchMaterials = async (
+    { q, tagState, mediaKind, createdFrom, createdTo,
+      updatedFrom, updatedTo, sort, direction, page,
+      tagId, includeDescendants, groupBy,
+      limit }: FetchMaterialsParams,
+): Promise<MaterialIndexResponse> =>
+    await apiGet ('/materials', { params: {
+	...(q && { q }),
+	tag_state:   tagState,
+	media_kind:  mediaKind,
+	...(tagId != null && { tag_id: tagId }),
+	...(includeDescendants && { include_descendants: '1' }),
+	...(groupBy !== 'none' && { group_by: groupBy }),
+	...(createdFrom && { created_from: createdFrom }),
+	...(createdTo && { created_to: createdTo }),
+	...(updatedFrom && { updated_from: updatedFrom }),
+	...(updatedTo && { updated_to: updatedTo }),
+	sort,
+	direction,
+	page,
+	limit} })
+
+
+export const fetchMaterial = async (id: string): Promise<Material | null> => {
+  try
+  {
+    return await apiGet (`/materials/${ id }`)
+  }
+  catch (error)
+  {
+    if (isApiError (error) && error.response?.status === 404)
+      return null
+    throw error
+  }
+}
+
+
+export const fetchMaterialChanges = async (
+    { materialId, tag, eventType, page, limit }: {
+	materialId?: string
+	tag?:        string
+	eventType?:  string
+	page:        number
+	limit:       number
+    }): Promise<MaterialChangesResponse> =>
+    await apiGet ('/materials/versions', { params: {
+	...(materialId && { material_id: materialId }),
+	...(tag && { tag }),
+	...(eventType && { event_type: eventType }),
+	page,
+	limit} })
+
+
+export const fetchMaterialTagTree = async (
+    { parentId, materialFilter }: FetchMaterialTreeParams): Promise<MaterialSidebarTag[]> =>
+    await apiGet ('/tags/with-depth', { params: {
+	...(parentId != null && { parent: String (parentId) }),
+	material_filter: materialFilter} })
+
+
+export const fetchMaterialTagByName = async (
+    name: string,
+    materialFilter: MaterialFilter): Promise<MaterialTagTree | null> => {
+  try
+  {
+    return await apiGet (`/tags/name/${ encodeURIComponent (name) }/materials`,
+			 { params: { material_filter: materialFilter } })
+  }
+  catch (error)
+  {
+    if (isApiError (error) && error.response?.status === 404)
+      return null
+    throw error
+  }
+}
+
+
+export const createMaterial = async (formData: FormData): Promise<Material> =>
+    await apiPost ('/materials', formData)
+
+
+export const updateMaterial = async (
+    id: string,
+    formData: FormData): Promise<Material> =>
+    await apiPut (`/materials/${ id }`, formData)
+
+
+export const fetchMaterialSyncSuppressions =
+    async (): Promise<MaterialSyncSuppressionResponse> =>
+        await apiGet ('/materials/suppressions')
+
+
+export const createMaterialSyncSuppression = async (
+    payload: {
+        sourceKind:   string
+        sourceUri?:   string
+        drivePath?:   string
+        driveFileId?: string
+        reason:       string
+    }): Promise<MaterialSyncSuppression> =>
+    await apiPost ('/materials/suppressions', {
+        source_kind:   payload.sourceKind,
+        source_uri:    payload.sourceUri,
+        drive_path:    payload.drivePath,
+        drive_file_id: payload.driveFileId,
+        reason:        payload.reason})

frontend/src/lib/posts.test.ts

@@ -70,6 +70,7 @@ describe ('posts API functions', () => {
           id:                    5,
           title:                 'new title',
           tags:                  'tag',
+          duration:              null,
           parentPostIds:         '1 2',
           originalCreatedFrom:   null,
           originalCreatedBefore: '2026-01-02T00:00:00Z',
@@ -82,6 +83,7 @@ describe ('posts API functions', () => {
         {
           title:                   'new title',
           tags:                    'tag',
+          duration:                null,
           parent_post_ids:         '1 2',
           original_created_from:   null,
           original_created_before: '2026-01-02T00:00:00Z',

frontend/src/lib/posts.ts

@@ -5,8 +5,7 @@ import type { FetchPostsParams, Post, PostVersion } from '@/types'
 
 export const fetchPosts = async (
     { url, title, tags, match, createdFrom, createdTo, updatedFrom, updatedTo,
-      originalCreatedFrom, originalCreatedTo, page, limit, order }: FetchPostsParams,
-): Promise<{
+      originalCreatedFrom, originalCreatedTo, page, limit, order }: FetchPostsParams): Promise<{
     posts:  Post[]
     count:  number }> =>
 	await apiGet ('/posts', { params: {
@@ -33,8 +32,7 @@ export const fetchPostChanges = async (
 	post?:  string
 	tag?:   string
 	page:   number
-	limit:  number },
-): Promise<{
+	limit:  number }): Promise<{
     versions: PostVersion[]
     count:    number }> =>
 	await apiGet ('/posts/versions', { params: { ...(post && { post }),
@@ -46,18 +44,19 @@ export const updatePost = async (
     post: { id:                     number
 	    title:                  string | null
 	    tags:                   string
+	    duration:               string | null
 	    parentPostIds:          string
 	    originalCreatedFrom:    string | null
 	    originalCreatedBefore:  string | null },
     { baseVersionNo, force, merge }: {
 	baseVersionNo?: number
 	force?:         boolean
-	merge?:         boolean }
-) =>
+	merge?:         boolean }) =>
     await apiPut<Post> (
 	`/posts/${ post.id }`,
 	{ title: post.title,
 	  tags: post.tags,
+	  duration: post.duration,
 	  parent_post_ids: post.parentPostIds,
 	  original_created_from: post.originalCreatedFrom,
 	  original_created_before: post.originalCreatedBefore },

frontend/src/lib/queryKeys.ts

@@ -1,4 +1,10 @@
-import type { FetchNicoTagsParams, FetchPostsParams, FetchTagsParams } from '@/types'
+import type {
+    FetchNicoTagsParams,
+    FetchMaterialsParams,
+    FetchPostsParams,
+    FetchTagsParams,
+    MaterialFilter,
+} from '@/types'
 
 export const postsKeys = {
     root:     ['posts'] as const,
@@ -25,6 +31,27 @@ export const tagsKeys = {
 		      ['tags', 'changes', p] as const,
     deerjikists:  (id: string) => ['tags', 'deerjikists', id] as const }
 
+export const materialsKeys = {
+    root:         ['materials'] as const,
+    index:        (p: FetchMaterialsParams) => ['materials', 'index', p] as const,
+    changes:      (p: {
+	materialId?: string
+	tag?:        string
+	eventType?:  string
+	page:        number
+	limit:       number
+    }) => ['materials', 'changes', p] as const,
+    byTagName:     (name: string, materialFilter: MaterialFilter) =>
+		      ['materials', 'tag', name, materialFilter] as const,
+    show:         (id: string) => ['materials', id] as const,
+    suppressions: () => ['materials', 'suppressions'] as const,
+    tree:         (p: {
+	parentId?:       number | null
+	materialFilter:  MaterialFilter
+    }) => ['materials', 'tree', p] as const,
+    unclassified: (p: { page?: number; limit?: number } = { }) =>
+		      ['materials', 'unclassified', p] as const}
+
 export const wikiKeys = {
     root:   ['wiki'] as const,
     index:  (p: { title?: string }) => ['wiki', 'index', p] as const,

frontend/src/lib/tags.ts

@@ -11,8 +11,7 @@ import type { Deerjikist,
 export const fetchTags = async (
     { post, name, category, postCountGTE, postCountLTE, createdFrom, createdTo,
       updatedFrom, updatedTo, deprecated,
-      page, limit, order }: FetchTagsParams,
-): Promise<{ tags:  Tag[]
+      page, limit, order }: FetchTagsParams): Promise<{ tags:  Tag[]
 	     count: number }> =>
     await apiGet ('/tags', { params: {
 	...(post != null && { post }),
@@ -31,8 +30,7 @@ export const fetchTags = async (
 
 
 export const fetchNicoTags = async (
-    { name, linkedTag, linkStatus, page, limit, order }: FetchNicoTagsParams,
-): Promise<{ tags:  NicoTag[]
+    { name, linkedTag, linkStatus, page, limit, order }: FetchNicoTagsParams): Promise<{ tags:  NicoTag[]
 	     count: number }> =>
     await apiGet ('/tags/nico', { params: {
 	page,
@@ -70,14 +68,12 @@ export const fetchTagChanges = async (
     { id, page, limit }: {
 	id?:    string
 	page:   number
-	limit:  number },
-): Promise<{
+	limit:  number }): Promise<{
     versions: TagVersion[]
     count:    number }> =>
 	await apiGet ('/tags/versions', { params: { ...(id && { id }), page, limit } })
 
 
 export const fetchDeerjikistsByTag = async (
-    id: string,
-): Promise<{ tag: Tag; deerjikists: Deerjikist[]}> =>
+    id: string): Promise<{ tag: Tag; deerjikists: Deerjikist[] }> =>
     await apiGet (`/tags/${ id }/deerjikists`)

frontend/src/lib/users.ts

@@ -4,5 +4,4 @@ const CONTENT_EDITOR_ROLES: readonly UserRole[] = ['admin', 'member']
 
 
 export const canEditContent = (
-    user: Pick<User, 'role'> | null | undefined,
-): boolean => user != null && CONTENT_EDITOR_ROLES.includes (user.role)
+    user: Pick<User, 'role'> | null | undefined): boolean => user != null && CONTENT_EDITOR_ROLES.includes (user.role)

frontend/src/lib/utils.test.ts

@@ -1,6 +1,6 @@
 import { describe, expect, it } from 'vitest'
 
-import { cn, originalCreatedAtString, toDate } from '@/lib/utils'
+import { cn, msToTime, originalCreatedAtString, toDate } from '@/lib/utils'
 
 describe ('utils', () => {
   it ('converts strings to dates and leaves date instances intact', () => {
@@ -26,3 +26,14 @@ describe ('utils', () => {
     ).toContain ('時刻不詳')
   })
 })
+
+describe ('msToTime', () => {
+  it ('keeps milliseconds when present', () => {
+    expect (msToTime (60_500)).toBe ('1:00.500')
+    expect (msToTime (60_001)).toBe ('1:00.001')
+  })
+
+  it ('omits milliseconds when they are zero', () => {
+    expect (msToTime (60_000)).toBe ('1:00')
+  })
+})

frontend/src/lib/utils.ts

@@ -12,8 +12,7 @@ export const cn = (...inputs: ClassValue[]) => twMerge (clsx (...inputs))
 
 export const dateString = (
     d:        string | Date,
-    unknown:  'month' | 'day' | 'hour' | 'minute' | 'second' | null = null,
-): string =>
+    unknown:  'month' | 'day' | 'hour' | 'minute' | 'second' | null = null): string =>
     toDate (d).toLocaleString (
 	'ja-JP-u-ca-japanese',
 	{ era: 'long',
@@ -28,8 +27,7 @@ export const dateString = (
 
 export const originalCreatedAtString = (
     f:  string | Date | null,
-    b:  string | Date | null,
-): string => {
+    b:  string | Date | null): string => {
   const from = f ? toDate (f) : null
   const before = b ? toDate (b) : null
 
@@ -73,6 +71,22 @@ export const originalCreatedAtString = (
 }
 
 
+export const msToTime = (ms: number): string => {
+  const totalS = Math.trunc (ms / 1_000)
+  const s = String (totalS % 60)
+  const min = String (Math.trunc (totalS / 60) % 60)
+  const h = Math.trunc (totalS / 3_600)
+  const remainderMs = ms % 1_000
+
+  const base =
+      (h > 0
+       ? `${ h }:${ min.padStart (2, '0') }:${ s.padStart (2, '0') }`
+       : `${ min }:${ s.padStart (2, '0') }`)
+
+  return remainderMs > 0 ? `${ base }.${ remainderMs.toString ().padStart (3, '0') }` : base
+}
+
+
 export const inputClass = (invalid?: boolean, className?: string): string =>
     cn ('w-full rounded border p-2',
 	(invalid

frontend/src/lib/wiki.ts

@@ -4,22 +4,19 @@ import type { WikiPage } from '@/types'
 
 
 export const fetchWikiPages = async (
-    { title }:  { title?: string },
-): Promise<WikiPage[]> =>
+    { title }:  { title?: string }): Promise<WikiPage[]> =>
     await apiGet ('/wiki', { params: { title } })
 
 
 export const fetchWikiPage = async (
     id:           string,
-    { version }:  { version?: string },
-): Promise<WikiPage> =>
+    { version }:  { version?: string }): Promise<WikiPage> =>
     await apiGet (`/wiki/${ id }`, { params: version ? { version } : { } })
 
 
 export const fetchWikiPageByTitle = async (
     title:        string,
-    { version }:  { version?: string },
-): Promise<WikiPage | null> => {
+    { version }:  { version?: string }): Promise<WikiPage | null> => {
   try
   {
     return await apiGet (`/wiki/title/${ encodeURIComponent (title) }`, { params: { version } })

frontend/src/pages/GekanatorPage.tsx

@@ -238,8 +238,7 @@ const createGameSeed = (): string => {
 
 const normalizeStoredQuestionId = (
     questionId:  string,
-    condition?:  GekanatorQuestionCondition,
-): string => {
+    condition?:  GekanatorQuestionCondition): string => {
   if (condition?.type === 'title-length-greater-than')
     return `title:length-at-least:${ condition.length + 1 }`
 
@@ -312,8 +311,7 @@ const sourcePriorityForMerge = (question: GekanatorQuestion): number => {
 
 const shouldReplaceMergedQuestion = (
     current:    GekanatorQuestion | undefined,
-    candidate:  GekanatorQuestion,
-): boolean => {
+    candidate:  GekanatorQuestion): boolean => {
   if (!(current))
     return true
 
@@ -408,8 +406,7 @@ const loadRecentGames = (): RecentGameSummary[] => {
 
 
 const storeRecentGameSummary = (
-    summary:  RecentGameSummary,
-): RecentGameSummary[] => {
+    summary:  RecentGameSummary): RecentGameSummary[] => {
   const next =
       [summary,
        ...loadRecentGames ().filter (item => (item.savedAt !== summary.savedAt
@@ -459,8 +456,7 @@ const resettableExtraQuestionState = (): {
 
 const recoveredCandidateMapFromStored = (
     items:   RecoveredCandidatePost[],
-    scores:  [number, number][],
-): Map<number, RecoveredCandidateState> => {
+    scores:  [number, number][]): Map<number, RecoveredCandidateState> => {
   const storedScores = new Map (scores)
 
   return new Map (items.map (item => [item.postId, {
@@ -470,8 +466,7 @@ const recoveredCandidateMapFromStored = (
 
 
 const storedRecoveredCandidatesFromMap = (
-    recoveredCandidatePosts: Map<number, RecoveredCandidateState>,
-): RecoveredCandidatePost[] =>
+    recoveredCandidatePosts: Map<number, RecoveredCandidateState>): RecoveredCandidatePost[] =>
     [...recoveredCandidatePosts.entries ()]
     .map (([postId, recoveredCandidate]) => ({
 	postId,
@@ -513,8 +508,7 @@ const distributionEntropy = (weights: number[]): number =>
 const questionCategoryPenalty = (
     question:       GekanatorQuestion,
     answerCount:    number,
-    repeatPenalty:  number,
-): number => {
+    repeatPenalty:  number): number => {
   const earlyFactor = Math.max (0, (3 - answerCount) / 3)
   const titleLengthPenalty = (() => {
     if (titleLengthMinimumForCondition (question.condition) == null)
@@ -553,8 +547,7 @@ const relatedPostIdsOf = (post: Post): number[] => {
 
 const userPriorWeightsFor = (
     posts:        Post[],
-    recentGames:  RecentGameSummary[],
-): Map<number, number> => {
+    recentGames:  RecentGameSummary[]): Map<number, number> => {
   const postById = new Map (posts.map (post => [post.id, post]))
   const weights = new Map<number, number> ()
   const addWeight = (postId: number, weight: number) => {
@@ -581,14 +574,12 @@ const userPriorWeightsFor = (
 
 const answerWeightFor = (
     questionId:           string,
-    softenedQuestionIds:  Set<string>,
-): number => softenedQuestionIds.has (questionId) ? softenedAnswerWeight : 1
+    softenedQuestionIds:  Set<string>): number => softenedQuestionIds.has (questionId) ? softenedAnswerWeight : 1
 
 
 const scoreWeightForAnswer = (
     answer:               GekanatorAnswerLog,
-    softenedQuestionIds:  Set<string>,
-): number =>
+    softenedQuestionIds:  Set<string>): number =>
     answerWeightFor (answer.questionId, softenedQuestionIds)
     * (
 	answer.questionPurpose === 'learning_user_suggested'
@@ -638,8 +629,7 @@ const titleTermPattern =
 const addPostIdToIndex = <K extends string | number> (
     index:   Map<K, Set<number>>,
     key:     K,
-    postId:  number,
-) => {
+    postId:  number) => {
   const current = index.get (key)
   if (current)
     {
@@ -652,8 +642,7 @@ const addPostIdToIndex = <K extends string | number> (
 
 
 const buildMaterialIndex = (
-    posts:  Post[],
-): GekanatorQuestionMaterialIndex => {
+    posts:  Post[]): GekanatorQuestionMaterialIndex => {
   const postById = new Map<number, Post> ()
   const tagKeysByPostId = new Map<number, string[]> ()
   const postIdsByTagKey = new Map<string, Set<number>> ()
@@ -784,8 +773,7 @@ const originalDateQuestionTextFor = (
     condition:  Extract<
 	GekanatorQuestionCondition,
 	{ type: 'original-year' | 'original-month' | 'original-month-day' }
-    >,
-): string => {
+    >): string => {
   switch (condition.type)
   {
   case 'original-year':
@@ -852,8 +840,7 @@ const isLearnableTagKey = (key: string): boolean => !(key.startsWith ('nico:'))
 
 
 const isUserSuggestedLearnedSemanticQuestion = (
-    question:  GekanatorQuestion,
-): boolean => isLearnedSemanticQuestion (question)
+    question:  GekanatorQuestion): boolean => isLearnedSemanticQuestion (question)
 
 
 type LearnedSemanticCandidateStats = {
@@ -872,8 +859,7 @@ const learnedSemanticStatsForCandidateIds = (
       question }: {
 	candidateIds:  number[]
 	posts:         Post[]
-	question:      GekanatorQuestion },
-): LearnedSemanticCandidateStats => {
+	question:      GekanatorQuestion }): LearnedSemanticCandidateStats => {
   const candidateIdSet = new Set (candidateIds)
   const positiveIds = new Set<number> ()
   const negativeIds = new Set<number> ()
@@ -915,8 +901,7 @@ const learnedSemanticQuestionIsEffectiveForCandidateIds = (
       question }: {
 	candidateIds:  number[]
 	posts:         Post[]
-	question:      GekanatorQuestion },
-): boolean => {
+	question:      GekanatorQuestion }): boolean => {
   if (!(isUserSuggestedLearnedSemanticQuestion (question)))
     return false
 
@@ -936,8 +921,7 @@ const learnedSemanticQuestionIsEffectiveForCandidateIds = (
 
 const directSemanticAnswerForPost = (
     question:  GekanatorQuestion,
-    post:      Post,
-): GekanatorAnswerValue | null => {
+    post:      Post): GekanatorAnswerValue | null => {
   const direct = question.exampleAnswers?.[String (post.id) as `${ number }`]
   if (direct)
     return direct
@@ -956,8 +940,7 @@ const learnedSemanticLearningValueForTopPosts = (
 	question:      GekanatorQuestion
 	learningTargetPosts: Post[]
 	candidateIds:  number[]
-	posts:         Post[] },
-): { missingTopCount: number
+	posts:         Post[] }): { missingTopCount: number
      knownCount:      number
      hasLearningValue: boolean } => {
   const missingTopCount =
@@ -1000,8 +983,7 @@ const learningTargetPostsForCandidates = ({
 
 
 const questionPurposeCountsFor = (
-    answers:  GekanatorAnswerLog[],
-): {
+    answers:  GekanatorAnswerLog[]): {
     effectiveUserSuggestedCount: number
     learningUserSuggestedCount:  number
     normalQuestionCount:         number
@@ -1041,8 +1023,7 @@ const questionPurposeCountsFor = (
 
 const learnedSemanticNarrowPenaltyForStats = (
     candidateCount:  number,
-    stats:           LearnedSemanticCandidateStats,
-): number => {
+    stats:           LearnedSemanticCandidateStats): number => {
   const minSide = candidateCount < 10 ? 1 : Math.max (3, candidateCount * .08)
   return stats.positiveCount < minSide || stats.negativeCount < minSide ? .15 : 0
 }
@@ -1050,8 +1031,7 @@ const learnedSemanticNarrowPenaltyForStats = (
 
 const learnedSemanticScoreDeltaForExpectedAnswer = (
     userAnswer:      GekanatorAnswerValue,
-    expectedAnswer:  GekanatorAnswerValue | null,
-): number => {
+    expectedAnswer:  GekanatorAnswerValue | null): number => {
   switch (userAnswer)
   {
   case 'yes':
@@ -1089,8 +1069,7 @@ const learnedSemanticScoreDeltaForExpectedAnswer = (
 const scoreDropDeltaForRecoveredPost = (
     postId:                   number,
     totalScore:               number,
-    recoveredCandidatePosts:  Map<number, RecoveredCandidateState>,
-): number => {
+    recoveredCandidatePosts:  Map<number, RecoveredCandidateState>): number => {
   const recoveredCandidate = recoveredCandidatePosts.get (postId)
   if (recoveredCandidate == null)
     return totalScore
@@ -1114,8 +1093,7 @@ const postPassesScoreDrop = (
       recoveredCandidatePosts }: {
 	postId:                   number
 	scores:                   Map<number, number>
-	recoveredCandidatePosts:  Map<number, RecoveredCandidateState> },
-): boolean => {
+	recoveredCandidatePosts:  Map<number, RecoveredCandidateState> }): boolean => {
   if (!(activeCandidateScoreDropEnabled (scores)))
     return true
 
@@ -1129,8 +1107,7 @@ const postPassesScoreDrop = (
 
 // `post_similarities` is the score-propagation graph, not the question kind.
 const questionUsesPostSimilarityPropagationGraphForScoring = (
-    question:  GekanatorQuestion,
-): boolean =>
+    question:  GekanatorQuestion): boolean =>
     (question.kind === 'post_similarity'
      && !(isUserSuggestedLearnedSemanticQuestion (question)))
       || (question.kind === 'tag'
@@ -1139,8 +1116,7 @@ const questionUsesPostSimilarityPropagationGraphForScoring = (
 
 
 const questionSupportsAnswerBasedHardFiltering = (
-    question:  GekanatorQuestion,
-): boolean => !(questionUsesPostSimilarityPropagationGraphForScoring (question))
+    question:  GekanatorQuestion): boolean => !(questionUsesPostSimilarityPropagationGraphForScoring (question))
     && !(isUserSuggestedLearnedSemanticQuestion (question))
 
 
@@ -1160,8 +1136,7 @@ const usesLearnedTagExamples = (question: GekanatorQuestion): boolean =>
 
 const searchedQuestionsFor = (
     questions:  GekanatorQuestion[],
-    search:     string,
-): GekanatorQuestion[] => {
+    search:     string): GekanatorQuestion[] => {
   const needle = search.trim ()
   if (!(needle))
     return []
@@ -1235,8 +1210,7 @@ type QuestionMatchResolver = {
 
 const buildGekanatorMatchIndex = (
     posts:      Post[],
-    questions:  GekanatorQuestion[],
-): GekanatorMatchIndex => new Map (
+    questions:  GekanatorQuestion[]): GekanatorMatchIndex => new Map (
     questions.map (question => [
 	question.id,
 	new Set (
@@ -1285,8 +1259,7 @@ const matchingPostIdsForQuestion = ({
 
 
 const positiveMatchingPostIdsForQuestion = (
-    resolver:  QuestionMatchResolver,
-): Set<number> => {
+    resolver:  QuestionMatchResolver): Set<number> => {
   if (isUserSuggestedLearnedSemanticQuestion (resolver.question))
     {
       const cached = resolver.dynamicMatchIndex?.get (resolver.question.id)
@@ -1356,8 +1329,7 @@ const matchingWeightInCandidates = (
 			     materialIndex:       GekanatorQuestionMaterialIndex
 			     matchIndex:          GekanatorMatchIndex
 			     question:            GekanatorQuestion
-			     dynamicMatchIndex?:  GekanatorMatchIndex },
-): number => {
+			     dynamicMatchIndex?:  GekanatorMatchIndex }): number => {
   const matched = positiveMatchingPostIdsForQuestion ({
       posts,
       materialIndex,
@@ -1380,8 +1352,7 @@ const signatureForCandidateIds = (
 			      materialIndex:      GekanatorQuestionMaterialIndex
 			      matchIndex:         GekanatorMatchIndex
 			      question:           GekanatorQuestion
-			      dynamicMatchIndex?: GekanatorMatchIndex },
-): string => {
+			      dynamicMatchIndex?: GekanatorMatchIndex }): string => {
   if (isUserSuggestedLearnedSemanticQuestion (question))
     {
       const postById = new Map (posts.map (post => [post.id, post]))
@@ -1421,8 +1392,7 @@ const postIdsForHardAnswer = (
 			     posts:               Post[]
 			     materialIndex:       GekanatorQuestionMaterialIndex
 			     matchIndex:          GekanatorMatchIndex
-			     dynamicMatchIndex?:  GekanatorMatchIndex },
-): number[] => {
+			     dynamicMatchIndex?:  GekanatorMatchIndex }): number[] => {
   if (!(questionSupportsAnswerBasedHardFiltering (question)))
     return candidateIds
 
@@ -1562,8 +1532,7 @@ const buildIndexedQuestion = (
 	text:           string
 	kind:           GekanatorQuestionKind
 	priorityWeight: number
-	materialIndex:  GekanatorQuestionMaterialIndex },
-): GekanatorQuestion => ({
+	materialIndex:  GekanatorQuestionMaterialIndex }): GekanatorQuestion => ({
     id: questionIdForCondition (condition),
     text,
     kind,
@@ -1578,8 +1547,7 @@ const buildIndexedQuestion = (
 const rankedEntriesForCounts = <T extends string | number> (
     { counts, total, cap }: { counts:  Map<T, number>
 			      total:   number
-    			      cap:     number },
-): [T, number][] =>
+    			      cap:     number }): [T, number][] =>
     ([...counts.entries ()]
      .filter (([, count]) => count > 0 && count < total)
      .sort ((a, b) => Math.abs (total / 2 - a[1]) - Math.abs (total / 2 - b[1]))
@@ -1594,8 +1562,7 @@ const buildQuestionsForCandidateIds = (
 				     materialIndex:     GekanatorQuestionMaterialIndex
 				     acceptedQuestions: GekanatorQuestion[]
 				     mode?:            QuestionBuildMode
-				     confirmationPostId?: number | null },
-): GekanatorQuestion[] => {
+				     confirmationPostId?: number | null }): GekanatorQuestion[] => {
   const total = candidateIds.length
   const confirmationPost = (() => {
     if (confirmationPostId == null)
@@ -1652,8 +1619,7 @@ const buildQuestionsForCandidateIds = (
       condition: Extract<
 	  GekanatorQuestionCondition,
 	  { type: 'original-year' | 'original-month' | 'original-month-day' }
-      >,
-  ): GekanatorQuestion => {
+      >): GekanatorQuestion => {
     const priorityWeight = (() => {
       if (condition.type === 'original-year')
 	return 1.04
@@ -1673,8 +1639,7 @@ const buildQuestionsForCandidateIds = (
   const specialMonthDays = rankedEntriesForCounts ({
       counts: monthDayCounts,
       total,
-      cap: factCap
-  }).filter (([monthDay]) => specialOriginalMonthDayLabelFor (String (monthDay)) != null)
+      cap: factCap}).filter (([monthDay]) => specialOriginalMonthDayLabelFor (String (monthDay)) != null)
 
   if (mode === 'split')
     {
@@ -2124,8 +2089,7 @@ type ExclusiveConditionGroup =
 
 
 const exclusiveConditionGroupFor = (
-    condition:  GekanatorQuestion['condition'],
-): ExclusiveConditionGroup | null => {
+    condition:  GekanatorQuestion['condition']): ExclusiveConditionGroup | null => {
   switch (condition.type)
   {
   case 'original-month':
@@ -2144,8 +2108,7 @@ const exclusiveConditionGroupFor = (
 
 const sameConditionValue = (
     left:   GekanatorQuestion['condition'],
-    right:  GekanatorQuestion['condition'],
-): boolean => {
+    right:  GekanatorQuestion['condition']): boolean => {
   const leftTitleLength = titleLengthMinimumForCondition (left)
   const rightTitleLength = titleLengthMinimumForCondition (right)
   if (leftTitleLength != null || rightTitleLength != null)
@@ -2187,8 +2150,7 @@ const sameConditionValue = (
 
 const isMonthCrossMatch = (
     candidate:  GekanatorQuestion['condition'],
-    previous:   GekanatorQuestion['condition'],
-): boolean => {
+    previous:   GekanatorQuestion['condition']): boolean => {
   const candidateMonth = monthForCondition (candidate)
   const previousMonth = monthForCondition (previous)
   if (candidateMonth == null || previousMonth == null)
@@ -2204,8 +2166,7 @@ const isMonthCrossMatch = (
 
 const isExclusiveContradiction = (
     candidate:  GekanatorQuestion['condition'],
-    previous:   GekanatorQuestion['condition'],
-): boolean => {
+    previous:   GekanatorQuestion['condition']): boolean => {
   const candidateGroup = exclusiveConditionGroupFor (candidate)
   const previousGroup = exclusiveConditionGroupFor (previous)
 
@@ -2242,16 +2203,14 @@ const contradictionPenaltyFor = ({
     case 'no':
       if (
 	  sameConditionValue (question.condition, previous)
-	  || isMonthCrossMatch (question.condition, previous)
-      )
+	  || isMonthCrossMatch (question.condition, previous))
 	return sum + 40
 
       return sum
     case 'probably_no':
       if (
 	  sameConditionValue (question.condition, previous)
-	  || isMonthCrossMatch (question.condition, previous)
-      )
+	  || isMonthCrossMatch (question.condition, previous))
 	return sum + 20
 
       return sum
@@ -2281,8 +2240,7 @@ const chooseQuestion = (
 		      recentFirstQuestionPenaltyById: Map<string, number>
 		      userPriorWeights: Map<number, number>
 		      materialIndex: GekanatorQuestionMaterialIndex
-		      matchIndex: GekanatorMatchIndex },
-): QuestionSelection | null => {
+		      matchIndex: GekanatorMatchIndex }): QuestionSelection | null => {
   const dynamicMatchIndex = new Map<string, Set<number>> ()
 
   const invertedSignature = (signature: string): string =>
@@ -2327,8 +2285,7 @@ const chooseQuestion = (
   const rank = (
       questionsToRank:    GekanatorQuestion[],
       candidates:         { post: Post; score: number }[],
-      weightedCandidates: { post: Post; score: number; weight: number }[],
-  ) => {
+      weightedCandidates: { post: Post; score: number; weight: number }[]) => {
     const redundant = redundantSignatures (candidates.map (item => item.post))
     const candidateById = new Map (candidates.map (item => [item.post.id, item.post]))
     const candidateIds = candidates.map (item => item.post.id)
@@ -2613,8 +2570,7 @@ const chooseQuestion = (
   if (
 	effectiveRatio < targetEffectiveUserSuggestedQuestionRatio
 	&& totalUserSuggestedRatio < targetTotalUserSuggestedQuestionRatio
-	&& effectiveUserSuggestedPool.length > 0
-  )
+	&& effectiveUserSuggestedPool.length > 0)
     {
       selectedPool = effectiveUserSuggestedPool
       selectedPurpose = 'effective_user_suggested'
@@ -2622,8 +2578,7 @@ const chooseQuestion = (
   else if (
 	learningRatio < targetLearningUserSuggestedQuestionRatio
 	&& totalUserSuggestedRatio < targetTotalUserSuggestedQuestionRatio
-	&& learningUserSuggestedPool.length > 0
-  )
+	&& learningUserSuggestedPool.length > 0)
     {
       selectedPool = learningUserSuggestedPool
       selectedPurpose = 'learning_user_suggested'
@@ -2683,8 +2638,7 @@ const chooseQuestion = (
 
 
 const winningRunPriorityFor = (
-    expected:    GekanatorAnswerValue,
-): number | null => {
+    expected:    GekanatorAnswerValue): number | null => {
   if (expected === 'yes')
     return 0
   if (expected === 'partial')
@@ -2719,8 +2673,7 @@ const chooseWinningRunQuestion = ({
       materialIndex,
       acceptedQuestions,
       mode: 'confirmation',
-      confirmationPostId: targetPost.id
-  })
+      confirmationPostId: targetPost.id})
       .filter (question => {
 	if (askedIds.has (question.id))
 	  return false
@@ -2829,8 +2782,7 @@ const chooseFallbackQuestion = ({
 	  materialIndex,
 	  acceptedQuestions: [],
 	  mode: 'confirmation',
-	  confirmationPostId: post.id
-      })))
+	  confirmationPostId: post.id})))
       .slice (0, 32)
   const dynamicMatchIndex = new Map<string, Set<number>> ()
   const ranked = mergeQuestions ([
@@ -2905,8 +2857,7 @@ const chooseFallbackQuestion = ({
 
 
 const shouldEnterGuessPhase = (
-    reason: GuessReason | null,
-): reason is 'hard_max_questions' | 'winning_run_finished' | 'question_count_checkpoint' =>
+    reason: GuessReason | null): reason is 'hard_max_questions' | 'winning_run_finished' | 'question_count_checkpoint' =>
     (reason === 'hard_max_questions'
      || reason === 'winning_run_finished'
      || reason === 'question_count_checkpoint')
@@ -2914,15 +2865,13 @@ const shouldEnterGuessPhase = (
 
 const isWinningRunActive = (
     winningRunTargetId:         number | null,
-    winningRunStartAnswerCount: number | null,
-): boolean =>
+    winningRunStartAnswerCount: number | null): boolean =>
     winningRunTargetId != null && winningRunStartAnswerCount != null
 
 
 const winningRunQuestionCount = (
     answers:                    GekanatorAnswerLog[],
-    winningRunStartAnswerCount: number | null,
-): number => {
+    winningRunStartAnswerCount: number | null): number => {
   if (winningRunStartAnswerCount == null)
     return 0
 
@@ -2962,8 +2911,7 @@ const nextQuestionPlanFor = (
     				      matchIndex: GekanatorMatchIndex
     				      lastGuessQuestionCount: number
     				      winningRunTargetId: number | null
-    				      winningRunStartAnswerCount: number | null },
-): { question: GekanatorQuestion | null
+    				      winningRunStartAnswerCount: number | null }): { question: GekanatorQuestion | null
      guess: Post | null
      guessReason: GuessReason | null
      questionMode: QuestionMode
@@ -3013,8 +2961,7 @@ const nextQuestionPlanFor = (
     if (
 	isWinningRunActive (winningRunTargetId, winningRunStartAnswerCount)
 	&& winningRunTargetId === nextWinningRunTargetId
-	&& winningRunStartAnswerCount != null
-    )
+	&& winningRunStartAnswerCount != null)
       return winningRunStartAnswerCount
 
     return answers.length
@@ -3188,8 +3135,7 @@ const mascotStateFor = (
     resultWon:             boolean | null,
     eligiblePostCount:     number,
     bestConfidencePercent: number,
-    winningRunActive:      boolean,
-): MascotState => {
+    winningRunActive:      boolean): MascotState => {
   const resultPhase =
       phase === 'end'
       || phase === 'review'
@@ -3210,13 +3156,11 @@ const mascotStateFor = (
     if (
 	winningRunActive
 	|| eligiblePostCount <= 2
-	|| bestConfidencePercent >= 70
-    )
+	|| bestConfidencePercent >= 70)
       return 'thinking_near'
     if (
 	eligiblePostCount >= 15
-	&& bestConfidencePercent < 45
-    )
+	&& bestConfidencePercent < 45)
       return 'thinking_far'
     return 'thinking_mid'
   case 'guess':
@@ -3327,8 +3271,7 @@ const GekanatorBackdrop: FC<{
 
   const settingsForMode = useCallback (
       (
-	  mode: 'normal' | 'winning_run' | 'guess',
-      ): { columns: number; rows: number; opacity: number } => {
+	  mode: 'normal' | 'winning_run' | 'guess'): { columns: number; rows: number; opacity: number } => {
 	if (mode === 'winning_run' || mode === 'guess')
 	  return { columns: 8, rows: 8, opacity: motionMode === 'calm' ? .18 : .24 }
 
@@ -3342,8 +3285,7 @@ const GekanatorBackdrop: FC<{
   const scaleForMode = useCallback (
       (
 	  mode:                    'normal' | 'winning_run' | 'guess',
-	  displayedWinningCount:   number,
-      ): number => {
+	  displayedWinningCount:   number): number => {
 	if (mode === 'guess')
 	  return 8
 
@@ -3355,8 +3297,7 @@ const GekanatorBackdrop: FC<{
       [])
 
   const postsForMode = useCallback ((
-      mode: 'normal' | 'winning_run' | 'guess',
-  ): Post[] => {
+      mode: 'normal' | 'winning_run' | 'guess'): Post[] => {
     if (mode === 'guess' && displayedGuess)
       return [displayedGuess]
     if (mode === 'winning_run' && winningRunTargetPost)
@@ -3366,8 +3307,7 @@ const GekanatorBackdrop: FC<{
 
   const thumbnailsForMode = useCallback ((
       mode:      'normal' | 'winning_run' | 'guess',
-      count:     number,
-  ): string[] => {
+      count:     number): string[] => {
     const modePosts = postsForMode (mode)
     if (modePosts.length === 0)
       return []
@@ -3734,8 +3674,7 @@ const GekanatorBackdrop: FC<{
 
 const expectedAnswerFor = (
     question:     GekanatorQuestion | undefined,
-    correctPost:  Post | null,
-): GekanatorAnswerValue | null =>
+    correctPost:  Post | null): GekanatorAnswerValue | null =>
     expectedAnswerForQuestion (question, correctPost)
 
 
@@ -4169,8 +4108,7 @@ const GekanatorPage: FC<{ user: User | null }> = ({ user }) => {
 	setSaved (true)
 	setSavedGameId (data.id)
 	setLearnedExampleCount (data.learnedExampleCount)
-	setResultWon (variables.guessedPostId === variables.correctPostId)
-      }})
+	setResultWon (variables.guessedPostId === variables.correctPostId)}})
   const questionSuggestionMutation = useMutation ({
       mutationFn: saveGekanatorQuestionSuggestion,
       onSuccess: async data => {
@@ -4180,15 +4118,13 @@ const GekanatorPage: FC<{ user: User | null }> = ({ user }) => {
 	setQuestionSuggestionSearch ('')
 	setQuestionSuggestionSelectedId (null)
 	setQuestionSuggestion ('')
-	setQuestionSuggestionAnswer ('yes')
-      }})
+	setQuestionSuggestionAnswer ('yes')}})
   const extraQuestionAnswersMutation = useMutation ({
       mutationFn: saveGekanatorExtraQuestionAnswers,
       onSuccess: async () => {
 	await queryClient.refetchQueries ({ queryKey: gekanatorKeys.questions () })
 	setExtraQuestionState ('saved')
-	setPhase ('end')
-      }})
+	setPhase ('end')}})
 
   const resetExtraQuestionState = () => {
     const next = resettableExtraQuestionState ()
@@ -4330,8 +4266,7 @@ const GekanatorPage: FC<{ user: User | null }> = ({ user }) => {
       if (
 	  !(allowPreQuestionRecovery)
 	  || recoveredEligiblePosts.length === 0
-	  || recoveredEligiblePosts.length === 1
-      )
+	  || recoveredEligiblePosts.length === 1)
 	return false
 
       const nextQuestion = chooseQuestion ({
@@ -4493,8 +4428,7 @@ const GekanatorPage: FC<{ user: User | null }> = ({ user }) => {
     if (
 	!(nextPlan.question)
 	&& !(shouldEnterGuessPhase (nextPlan.guessReason))
-	&& recovered.eligiblePosts.length !== 1
-    )
+	&& recovered.eligiblePosts.length !== 1)
       {
 	const recoveredForQuestion = recoverQuestionState ({
 	    nextAnswers,
@@ -4602,8 +4536,7 @@ const GekanatorPage: FC<{ user: User | null }> = ({ user }) => {
 	!(canPersistGame)
 	|| reviewGuessedPostId == null
 	|| reviewCorrectPostId == null
-	|| saveMutation.isPending
-    )
+	|| saveMutation.isPending)
       return
 
     if (savedGameId != null)
@@ -4666,8 +4599,7 @@ const GekanatorPage: FC<{ user: User | null }> = ({ user }) => {
 	!(canPersistGame)
 	|| savedGameId == null
 	|| extraQuestionAnswersMutation.isPending
-	|| extraQuestions.some (question => !(extraQuestionAnswers[String (question.id)]))
-    )
+	|| extraQuestions.some (question => !(extraQuestionAnswers[String (question.id)])))
       return
 
     extraQuestionAnswersMutation.mutate ({
@@ -4870,8 +4802,7 @@ const GekanatorPage: FC<{ user: User | null }> = ({ user }) => {
 
   const answerExtraQuestion = (
       questionId:  number,
-      value:       GekanatorAnswerValue,
-  ) => {
+      value:       GekanatorAnswerValue) => {
     setExtraQuestionAnswers ({
 	...extraQuestionAnswers,
 	[String (questionId)]: value })
@@ -4909,8 +4840,7 @@ const GekanatorPage: FC<{ user: User | null }> = ({ user }) => {
 	|| isLoading
 	|| acceptedQuestionsLoading
 	|| shouldEnterGuessPhase (questionPlan.guessReason)
-	|| eligiblePosts.length === 1
-    )
+	|| eligiblePosts.length === 1)
       return
 
     const recovered = recoverQuestionState ({
@@ -4926,8 +4856,7 @@ const GekanatorPage: FC<{ user: User | null }> = ({ user }) => {
     if (
 	recovered.recoveryStepCount === recoveryStepCount
 	&& recovered.recoveredCandidatePosts.size === recoveredCandidatePosts.size
-	&& recovered.softenedQuestionIds.size === softenedQuestionIds.size
-    )
+	&& recovered.softenedQuestionIds.size === softenedQuestionIds.size)
       return
 
     setSoftenedQuestionIds (recovered.softenedQuestionIds)
@@ -4954,15 +4883,13 @@ const GekanatorPage: FC<{ user: User | null }> = ({ user }) => {
     if (
 	phase !== 'question'
 	|| isLoading
-	|| acceptedQuestionsLoading
-    )
+	|| acceptedQuestionsLoading)
       return
 
     if (
 	currentQuestion
 	|| !(questionPlan.guess)
-	|| !(shouldEnterGuessPhase (questionPlan.guessReason))
-    )
+	|| !(shouldEnterGuessPhase (questionPlan.guessReason)))
       return
 
     setWinningRunTargetId (questionPlan.winningRunTargetId)