#399

backend/app/controllers/posts_controller.rb

@@ -120,30 +120,64 @@ class PostsController < ApplicationController
     return head :forbidden unless current_user.gte_member?
     return render_bad_request('URL は必須です．') if params[:url].blank?
 
-    preview = PostImportPreviewer.new.preview_rows(
+    normal_url = PostUrlNormaliser.normalise(params[:url].to_s)
-        rows: [{
+    return render_validation_error(fields: { url: ['URL が不正です．'] }) if normal_url.blank?
-            source_row: 1,
+
-            url: params[:url].to_s,
+    Preview::UrlSafety.validate(normal_url)
-            attributes: { },
+    existing_post = Post.with_attached_thumbnail.find_by(url: normal_url)
-            provenance: { },
+    if existing_post.present?
-            tag_sources: { } }],
+      return render json: {
-        fetch_metadata: true).first
+          url: normal_url,
-    return render_validation_error fields: preview[:validation_errors] if preview[:validation_errors].present?
+          title: nil,
+          thumbnail_base: nil,
+          tags: nil,
+          original_created_from: nil,
+          original_created_before: nil,
+          duration: nil,
+          video_ms: nil,
+          field_warnings: { },
+          base_warnings: [],
+          existing_post: compact_post(existing_post.id) }
+    end
+
+    metadata = PostMetadataFetcher.fetch(normal_url)
+    field_warnings = { }
+    field_warnings[:title] = ['タイトルを取得できませんでした．'] if metadata[:title].blank?
+    if metadata[:thumbnail_base].blank?
+      field_warnings[:thumbnail_base] = ['サムネールを取得できませんでした．']
+    end
 
     render json: {
-        url: preview[:url],
+        url: normal_url,
-        title: preview[:attributes]['title'],
+        title: metadata[:title],
-        thumbnail_base: preview[:attributes]['thumbnail_base'],
+        thumbnail_base: metadata[:thumbnail_base],
-        tags: preview[:attributes]['tags'],
+        tags: metadata[:tags],
-        original_created_from: preview[:attributes]['original_created_from'],
+        original_created_from: metadata[:original_created_from],
-        original_created_before: preview[:attributes]['original_created_before'],
+        original_created_before: metadata[:original_created_before],
-        duration: preview[:attributes]['duration'],
+        duration: metadata[:duration],
-        video_ms: preview[:attributes]['video_ms'],
+        video_ms: metadata[:video_ms],
-        field_warnings: preview[:field_warnings],
+        field_warnings: field_warnings,
-        base_warnings: preview[:base_warnings],
+        base_warnings: [],
-        existing_post: compact_post(preview[:existing_post_id]) }
+        existing_post: nil }
   rescue ArgumentError => e
     render_bad_request e.message
+  rescue Preview::UrlSafety::UnsafeUrl => e
+    render_validation_error fields: { url: [e.message] }
+  rescue Preview::HttpFetcher::FetchFailed,
+         Preview::HttpFetcher::FetchTimeout,
+         Preview::HttpFetcher::ResponseTooLarge
+    render json: {
+        url: normal_url,
+        title: nil,
+        thumbnail_base: nil,
+        tags: nil,
+        original_created_from: nil,
+        original_created_before: nil,
+        duration: nil,
+        video_ms: nil,
+        field_warnings: { url: ['自動取得に失敗しました．'] },
+        base_warnings: [],
+        existing_post: nil }
   end
 
   def show

backend/app/models/post.rb

@@ -3,6 +3,7 @@ class Post < ApplicationRecord
   require 'mini_magick'
   require 'nokogiri'
   require 'stringio'
+  require 'timeout'
 
   class RemoteThumbnailFetchFailed < StandardError; end
 
@@ -15,6 +16,7 @@ class Post < ApplicationRecord
   REMOTE_SVG_CONTENT_TYPE = 'image/svg+xml'.freeze
   MAX_SVG_DIMENSION = 4_096
   MAX_SVG_PIXELS = 16_777_216
+  THUMBNAIL_PROCESS_TIMEOUT = 5.seconds
 
   def self.resized_thumbnail_attachment(upload, content_type: nil)
     upload.rewind
@@ -216,15 +218,37 @@ class Post < ApplicationRecord
   end
 
   def self.image_for_thumbnail_upload(bytes, content_type: nil)
-    return MiniMagick::Image.read(bytes) unless svg_content_type?(content_type)
+    return decode_raster_thumbnail(bytes) unless svg_content_type?(content_type) || svg_document_bytes?(bytes)
 
-    MiniMagick::Image.read(sanitised_svg_bytes(bytes))
+    decode_svg_thumbnail(bytes)
   end
 
   def self.svg_content_type?(content_type)
     content_type.to_s.split(';', 2).first.to_s.downcase.strip == REMOTE_SVG_CONTENT_TYPE
   end
 
+  def self.svg_document_bytes?(bytes)
+    document = Nokogiri::XML(
+        bytes,
+        nil,
+        nil,
+        Nokogiri::XML::ParseOptions::STRICT |
+        Nokogiri::XML::ParseOptions::NONET)
+    document.root&.name == 'svg'
+  rescue Nokogiri::XML::SyntaxError
+    false
+  end
+
+  def self.decode_raster_thumbnail(bytes)
+    Timeout.timeout(THUMBNAIL_PROCESS_TIMEOUT) { MiniMagick::Image.read(bytes) }
+  end
+
+  def self.decode_svg_thumbnail(bytes)
+    Timeout.timeout(THUMBNAIL_PROCESS_TIMEOUT) do
+      MiniMagick::Image.read(sanitised_svg_bytes(bytes))
+    end
+  end
+
   def self.sanitised_svg_bytes(bytes)
     parse_options =
         Nokogiri::XML::ParseOptions::STRICT |
@@ -256,20 +280,44 @@ class Post < ApplicationRecord
 
       name = node.name.to_s.downcase
       next true if name == 'script' || name == 'foreignobject'
+      next style_contains_disallowed_urls?(node.text.to_s) if name == 'style'
 
       node.attribute_nodes.any? do |attribute|
         attribute_name = attribute.name.to_s.downcase
         attribute_value = attribute.value.to_s
         attribute_name.start_with?('on') ||
-            attribute_name == 'href' ||
+            external_svg_reference?(attribute_name, attribute_value)
-            attribute_name == 'xlink:href' ||
-            attribute_name == 'src' ||
-            (attribute_name == 'style' && attribute_value.match?(/url\s*\(/i)) ||
-            attribute_value.match?(/\A\s*(?:https?:|data:|\/\/)/i)
       end
     end
   end
 
+  def self.external_svg_reference?(attribute_name, attribute_value)
+    return external_svg_url?(attribute_value) if ['href', 'xlink:href', 'src'].include?(attribute_name)
+    return style_contains_disallowed_urls?(attribute_value) if attribute_name == 'style'
+    return svg_url_function_disallowed?(attribute_value) if attribute_value.match?(/url\s*\(/i)
+
+    false
+  end
+
+  def self.external_svg_url?(value)
+    stripped = value.to_s.strip
+    return false if stripped.blank? || stripped.start_with?('#')
+
+    stripped.match?(/\A(?:https?:|data:|\/\/)/i)
+  end
+
+  def self.style_contains_disallowed_urls?(value)
+    text = value.to_s
+    text.match?(/@import/i) || svg_url_function_disallowed?(text)
+  end
+
+  def self.svg_url_function_disallowed?(value)
+    value.to_s.scan(/url\s*\(([^)]*)\)/i).flatten.any? do |entry|
+      reference = entry.to_s.strip.delete_prefix("'").delete_prefix('"').delete_suffix("'").delete_suffix('"')
+      reference.present? && !(reference.start_with?('#'))
+    end
+  end
+
   def self.svg_dimensions(root)
     width = svg_length_to_pixels(root['width'])
     height = svg_length_to_pixels(root['height'])
@@ -287,15 +335,24 @@ class Post < ApplicationRecord
     matched = /\A([0-9]+(?:\.[0-9]+)?)(px)?\z/i.match(value.to_s.strip)
     return nil if matched == nil
 
-    Float(matched[1])
+    pixels = Float(matched[1])
+    return nil unless pixels.finite? && pixels.positive?
+
+    pixels
   rescue ArgumentError
     nil
   end
 
   private_class_method :image_for_thumbnail_upload,
                        :svg_content_type?,
+                       :decode_raster_thumbnail,
+                       :decode_svg_thumbnail,
                        :sanitised_svg_bytes,
                        :svg_uses_disallowed_features?,
+                       :external_svg_reference?,
+                       :external_svg_url?,
+                       :style_contains_disallowed_urls?,
+                       :svg_url_function_disallowed?,
                        :svg_dimensions,
                        :svg_length_to_pixels
 

backend/app/representations/post_compact_repr.rb

@@ -20,7 +20,7 @@ module PostCompactRepr
     Rails.application.routes.url_helpers.rails_storage_proxy_url(
         post.thumbnail,
         only_path: false)
-  rescue
+  rescue ActionController::UrlGenerationError, ArgumentError, URI::InvalidURIError
     nil
   end
 end

backend/app/services/post_thumbnail_upload_validator.rb

@@ -11,8 +11,10 @@ class PostThumbnailUploadValidator
     end
     raise InvalidUpload, 'thumbnail file size が大きすぎます．' if thumbnail.size > MAX_THUMBNAIL_BYTES
     raise InvalidUpload, 'サムネイル画像の形式が不正です．' unless allowed_content_type?(thumbnail.content_type)
+    raise InvalidUpload, 'サムネイル画像の形式が不正です．' if Post.svg_document_bytes?(thumbnail.read)
+    thumbnail.rewind
 
-    attachment = Post.resized_thumbnail_attachment(thumbnail)
+    attachment = Post.resized_thumbnail_attachment(thumbnail, content_type: thumbnail.content_type)
     attachment[:io].close if attachment[:io].respond_to?(:close)
   rescue MiniMagick::Error
     raise InvalidUpload, 'サムネイル画像の変換に失敗しました．'

backend/app/services/preview/thumbnail_fetcher.rb

@@ -32,7 +32,7 @@ module Preview
     def self.fetch_image_response(raw_url)
       uri, = UrlSafety.validate(raw_url)
       response = HttpFetcher.fetch(uri.to_s)
-      unless allowed_remote_image_content_type?(response.content_type)
+      unless allowed_remote_image_content_type?(response.content_type) || Post.svg_document_bytes?(response.body)
         raise GenerationFailed, 'サムネール画像が見つかりませんでした．'
       end
 

frontend/src/components/posts/import/PostImportStatusBadge.tsx

@@ -10,6 +10,7 @@ type Props = {
 
 const LABELS: Record<PostImportBadgeValue, string> = {
     ready: '登録可能',
+    error: '登録不可',
     warning: '警告',
     skipped: 'スキップ',
     created: '登録済み',
@@ -17,6 +18,7 @@ const LABELS: Record<PostImportBadgeValue, string> = {
 
 const TONES: Record<PostImportBadgeValue, StatusBadgeTone> = {
     ready: 'success',
+    error: 'warning',
     warning: 'warning',
     skipped: 'neutral',
     created: 'success',

frontend/src/components/posts/import/postImportRowStatus.ts

@@ -2,6 +2,7 @@ import type { PostImportRow } from '@/lib/postImportSession'
 
 export type PostImportDisplayStatus =
     'ready'
+    | 'error'
     | 'skipped'
     | 'warning'
     | 'created'
@@ -18,13 +19,16 @@ export const displayPostImportStatus = (
 ): PostImportDisplayStatus | null =>
     row.status === 'pending'
     ? null
+    : (row.importStatus === 'failed')
+    ? 'failed'
     : (row.skipReason != null || row.importStatus === 'skipped')
     ? 'skipped'
     : (row.importStatus === 'created')
       ? 'created'
-      : ((Object.keys (row.validationErrors ?? { }).length > 0
+      : (row.status === 'error')
-	  || row.importStatus === 'failed')
+      ? 'error'
-         ? 'failed'
+      : (Object.values (row.validationErrors ?? { }).some (messages => messages.length > 0))
-         : ((hasWarnings (row) || row.status === 'warning')
+      ? 'error'
-	    ? 'warning'
+      : ((hasWarnings (row) || row.status === 'warning')
-	    : 'ready'))
+	 ? 'warning'
+	 : 'ready')

frontend/src/lib/postImportRows.ts

@@ -22,8 +22,21 @@ export const isManualSkipRow = (row: PostImportRow): boolean =>
 const hasSkipReason = (row: PostImportRow): boolean =>
     row.skipReason != null
 
+export const compactMessageRecord = (
+    messages: Record<string, string[]>,
+): Record<string, string[]> =>
+    Object.fromEntries (
+	Object.entries (messages).filter (([, values]) => values.length > 0))
+
+
+export const hasErrorMessages = (
+    messages: Record<string, string[]>,
+): boolean =>
+    Object.values (messages).some (values => values.length > 0)
+
+
 const hasValidationErrors = (row: PostImportRow): boolean =>
-    Object.keys (row.validationErrors ?? { }).length > 0
+    hasErrorMessages (row.validationErrors ?? { })
 
 const isRecoverableRow = (row: PostImportRow): boolean =>
     row.recoverable === true
@@ -79,9 +92,9 @@ const thumbnailWarnings = (row: PostImportRow): string[] => {
 
 export const applyThumbnailWarning = (row: PostImportRow): PostImportRow => ({
     ...row,
-    fieldWarnings: {
+    fieldWarnings: compactMessageRecord ({
 	...row.fieldWarnings,
-	thumbnailBase: thumbnailWarnings (row) } })
+	thumbnailBase: thumbnailWarnings (row) }) })
 
 
 export const applyThumbnailWarnings = (rows: PostImportRow[]): PostImportRow[] =>
@@ -90,7 +103,7 @@ export const applyThumbnailWarnings = (rows: PostImportRow[]): PostImportRow[] =
 
 export const processableImportRows = (rows: PostImportRow[]): PostImportRow[] =>
     validatableImportRows (rows).filter (row => {
-      if (row.metadataUrl == null)
+      if (row.status === 'pending')
         return false
       if (row.importStatus === 'created')
         return false
@@ -290,7 +303,7 @@ export const mergeValidatedImportRows = (
         return previous
 
       const fieldWarnings =
-          Object.keys (row.fieldWarnings).length > 0 || row.metadataUrl !== previous.metadataUrl
+          hasErrorMessages (row.fieldWarnings) || row.metadataUrl !== previous.metadataUrl
           ? { ...row.fieldWarnings }
           : { ...previous.fieldWarnings }
       for (const [field, origin] of Object.entries (row.provenance))
@@ -345,9 +358,10 @@ export const mergeImportResults = (
               createdPostId: result.post.id,
               existingPostId: undefined,
               existingPost: undefined,
-              fieldWarnings: result.fieldWarnings ?? row.fieldWarnings,
+              fieldWarnings: compactMessageRecord (
+		  result.fieldWarnings ?? row.fieldWarnings),
               baseWarnings: result.baseWarnings ?? row.baseWarnings,
-              importErrors: result.errors }
+              importErrors: compactMessageRecord (result.errors ?? { }) }
         case 'skipped':
           return {
               ...row,
@@ -357,9 +371,10 @@ export const mergeImportResults = (
               createdPostId: undefined,
               existingPostId: result.existingPostId,
               existingPost: result.existingPost ?? row.existingPost,
-              fieldWarnings: result.fieldWarnings ?? row.fieldWarnings,
+              fieldWarnings: compactMessageRecord (
+		  result.fieldWarnings ?? row.fieldWarnings),
               baseWarnings: result.baseWarnings ?? row.baseWarnings,
-              importErrors: result.errors }
+              importErrors: compactMessageRecord (result.errors ?? { }) }
         case 'failed':
           return {
               ...row,
@@ -369,9 +384,10 @@ export const mergeImportResults = (
               createdPostId: undefined,
               existingPostId: undefined,
               existingPost: undefined,
-              fieldWarnings: result.fieldWarnings ?? row.fieldWarnings,
+              fieldWarnings: compactMessageRecord (
+		  result.fieldWarnings ?? row.fieldWarnings),
               baseWarnings: result.baseWarnings ?? row.baseWarnings,
-              importErrors: result.errors }
+              importErrors: compactMessageRecord (result.errors ?? { }) }
         }
     })
 }

frontend/src/pages/posts/PostImportReviewPage.tsx

@@ -30,8 +30,10 @@ import {
     clearPostImportSourceDraft,
     generatePostImportSessionId,
     hasThumbnailBaseValue,
+    hasErrorMessages,
     isCompletedReviewRow,
     isExistingSkipRow,
+    isManualSkipRow,
     isNonRecoverableFailedRow,
     mergeImportResults,
     processableImportRows,
@@ -41,7 +43,7 @@ import {
     reviewSummaryCounts,
     retryImportRow,
     loadPostImportSession,
-    serialisedPostImportRowsEqual,
+    compactMessageRecord,
     savePostImportSession,
 } from '@/lib/postImportSession'
 import { useClientBehaviourSettings } from '@/lib/useClientBehaviourSettings'
@@ -102,15 +104,48 @@ const isRepairRow = (row: PostImportRow): boolean =>
     row.recoverable === true
     && (row.importStatus === 'failed'
         || (row.importStatus === 'pending'
-            && Object.keys (row.validationErrors).length > 0))
+            && hasErrorMessages (row.validationErrors)))
 
 const DUPLICATE_URL_MESSAGE = 'URL が重複しています．'
 
+const rowMetadataPending = (row: PostImportRow): boolean =>
+    row.status === 'pending'
+
+const rowOperationBusy = (
+    row:         PostImportRow,
+    submitting:  boolean,
+    loadingRow:  number | null,
+): boolean =>
+    submitting
+    || loadingRow === row.sourceRow
+    || rowMetadataPending (row)
+
+
+const rowSkipBusy = (
+    row:         PostImportRow,
+    submitting:  boolean,
+    loadingRow:  number | null,
+): boolean =>
+    submitting
+    || loadingRow === row.sourceRow
+    || (rowMetadataPending (row) && !(isManualSkipRow (row)))
+
+const shouldFetchMetadata = (row: PostImportRow): boolean =>
+    row.status === 'pending'
+    && row.skipReason !== 'manual'
+    && row.importStatus !== 'created'
+    && row.importStatus !== 'skipped'
+    && !(isNonRecoverableFailedRow (row))
+    && row.metadataUrl == null
+
 const applyDuplicateUrlErrors = (
     rows: PostImportRow[],
 ): PostImportRow[] => {
   const counts = rows.reduce<Record<string, number>> ((result, row) => {
-    if (row.url !== '')
+    if (row.url !== ''
+	&& !(isManualSkipRow (row))
+	&& row.importStatus !== 'created'
+	&& row.importStatus !== 'skipped')
       result[row.url] = (result[row.url] ?? 0) + 1
     return result
   }, { })
@@ -120,27 +155,30 @@ const applyDuplicateUrlErrors = (
 	message => message !== DUPLICATE_URL_MESSAGE)
     if ((counts[row.url] ?? 0) < 2)
       {
-        const nextValidationErrors = {
+        const nextValidationErrors = compactMessageRecord ({
 	    ...row.validationErrors,
-	    url: urlErrors }
+	    url: urlErrors })
-        const hasErrors = Object.values (nextValidationErrors).some (
+        const hasErrors = hasErrorMessages (nextValidationErrors)
-	    messages => messages.length > 0)
 	return urlErrors.length === (row.validationErrors.url ?? []).length
 	    ? row
 	    : {
 		...row,
 		validationErrors: nextValidationErrors,
+		skipReason:
+		    row.skipReason === 'manual'
+		    ? 'manual'
+		    : row.existingPostId != null
+		      ? 'existing'
+		      : undefined,
 		status: hasErrors ? 'error' : row.status }
       }
 
     return {
 	...row,
 	skipReason: row.skipReason === 'manual' ? 'manual' : undefined,
-	existingPostId: undefined,
+	validationErrors: compactMessageRecord ({
-	existingPost: undefined,
-	validationErrors: {
 	    ...row.validationErrors,
-	    url: [...new Set ([...urlErrors, DUPLICATE_URL_MESSAGE])] },
+	    url: [...new Set ([...urlErrors, DUPLICATE_URL_MESSAGE])] }),
 	status: 'error' }
   })
 }
@@ -179,8 +217,9 @@ const mergeDryRunRow = (
     currentRow: PostImportRow,
     result:     PostMetadataResponse,
 ): PostImportRow => {
+    const fieldWarnings = compactMessageRecord (result.fieldWarnings ?? { })
     const hasWarnings =
-        Object.values (result.fieldWarnings ?? { }).some (messages => messages.length > 0)
+        Object.values (fieldWarnings).some (messages => messages.length > 0)
         || (result.baseWarnings?.length ?? 0) > 0
     return applyThumbnailWarning ({
         ...currentRow,
@@ -195,7 +234,7 @@ const mergeDryRunRow = (
             videoMs: result.videoMs ?? '',
             tags: result.tags ?? '',
             parentPostIds: String (result.parentPostIds ?? currentRow.attributes.parentPostIds ?? '') },
-        fieldWarnings: result.fieldWarnings ?? { },
+        fieldWarnings,
         baseWarnings: result.baseWarnings ?? [],
         validationErrors: { },
         importErrors: undefined,
@@ -291,9 +330,9 @@ const mergePreviewRow = (
     currentRow: PostImportRow,
     preview:    PostMetadataResponse,
 ): PostImportRow => {
-  const fieldWarnings = preview.fieldWarnings ?? { }
+  const fieldWarnings = compactMessageRecord (preview.fieldWarnings ?? { })
   const baseWarnings = preview.baseWarnings ?? []
-  const validationErrors = preview.validationErrors ?? { }
+  const validationErrors = compactMessageRecord (preview.validationErrors ?? { })
   const metadataChanged = currentRow.metadataUrl !== preview.url
   const hasWarnings =
       Object.values (fieldWarnings).some (messages => messages.length > 0)
@@ -438,7 +477,20 @@ const PostImportReviewPage: FC<Props> = ({ user }) => {
   const persistSequenceRef = useRef (0)
   const previewSequenceRef = useRef (0)
 
-  const persistSession = async (
+  const commitSessionState = (
+      nextSession: PostImportSession,
+  ): PostImportSession => {
+    const sessionId =
+	sessionIdRef.current ?? generatePostImportSessionId ()
+    sessionIdRef.current = sessionId
+    const persistedSession = buildSession (nextSession.rows)
+    savePostImportSession (sessionId, persistedSession)
+    sessionRef.current = persistedSession
+    setSession (persistedSession)
+    return persistedSession
+  }
+
+  const syncSessionUrl = async (
       nextSession: PostImportSession,
   ): Promise<PostImportSession | null> => {
     const sessionId =
@@ -451,26 +503,21 @@ const PostImportReviewPage: FC<Props> = ({ user }) => {
     if (persistSequenceRef.current !== sequence)
       return null
 
-    const saved = savePostImportSession (sessionId, nextSession)
+    const persistedSession = commitSessionState (nextSession)
-    const loadedSession = loadPostImportSession (sessionId)
-    const canRecoverFromUrlOnly = serialised.complete
-    if (!(canRecoverFromUrlOnly)
-        && (!(saved))
-        && !(serialisedPostImportRowsEqual (loadedSession?.rows ?? [], nextSession.rows)))
-      return null
-    if (saved
-        && !(serialisedPostImportRowsEqual (loadedSession?.rows ?? [], nextSession.rows)))
-      return null
 
-    const persistedSession = buildSession (nextSession.rows)
     const path = appendPostNewSessionId (serialised.path, sessionId)
     persistedSearchRef.current = (new URL (path, window.location.origin)).search
-    sessionRef.current = persistedSession
-    setSession (persistedSession)
     navigate (path, { replace: true })
     return persistedSession
   }
 
+  const currentRowBySource = (
+      sourceRow: number,
+      fallback?: PostImportSession,
+  ): PostImportRow | null =>
+      (sessionRef.current?.rows ?? fallback?.rows ?? []).find (
+	  row => row.sourceRow === sourceRow) ?? null
+
   const finishImport = () => {
     const sessionId = sessionIdRef.current
     if (sessionId != null)
@@ -485,7 +532,9 @@ const PostImportReviewPage: FC<Props> = ({ user }) => {
     const previewSequence = ++previewSequenceRef.current
     const controllers = new Set<AbortController> ()
 
-    if (sessionRef.current != null && persistedSearchRef.current === location.search)
+    if (sessionRef.current != null
+        && persistedSearchRef.current === location.search
+        && !(sessionRef.current.rows.some (row => shouldFetchMetadata (row))))
       return () => {
         previewSequenceRef.current = previewSequence
       }
@@ -496,20 +545,16 @@ const PostImportReviewPage: FC<Props> = ({ user }) => {
       try
       {
         let nextIndex = 0
-        const previewErrors = new Map<number, Record<string, string[]>> ()
+        const mergeCurrentRow = (
-        let workingRows = [...(sessionRef.current ?? baseSession).rows]
-
-        const mergeWorkingRow = (
 	    sourceRow: number,
 	    updater:   (row: PostImportRow) => PostImportRow,
         ) => {
-	    workingRows = workingRows.map (row =>
+	    const latestRows = sessionRef.current?.rows ?? baseSession.rows
+	    const nextRows = applyDuplicateUrlErrors (latestRows.map (row =>
 	        row.sourceRow === sourceRow
 	        ? updater (row)
-	        : row)
+	        : row))
-	    const nextSession = buildSession (workingRows)
+	    commitSessionState (buildSession (nextRows))
-	    sessionRef.current = nextSession
-	    setSession (nextSession)
         }
         const worker = async () => {
           while (active)
@@ -520,22 +565,25 @@ const PostImportReviewPage: FC<Props> = ({ user }) => {
               return
 
             const baseRow = baseSession.rows[index]
-            if (baseRow.skipReason === 'manual'
+            const currentRow = currentRowBySource (baseRow.sourceRow, baseSession)
-                || baseRow.importStatus === 'created'
+            if (currentRow == null || !(shouldFetchMetadata (currentRow)))
-                || baseRow.importStatus === 'skipped'
-                || isNonRecoverableFailedRow (baseRow)
-                || baseRow.metadataUrl != null)
               continue
             const controller = new AbortController ()
             controllers.add (controller)
             try
             {
               const preview = await apiGet<PostMetadataResponse> ('/posts/metadata', {
-                  params: { url: baseRow.url },
+                  params: { url: currentRow.url },
                   signal: controller.signal })
               if (!(active) || previewSequenceRef.current !== previewSequence)
                 return
-              mergeWorkingRow (baseRow.sourceRow, row => mergePreviewRow (row, preview))
+              mergeCurrentRow (currentRow.sourceRow, row =>
+		  row.importStatus === 'created'
+		  || row.importStatus === 'skipped'
+		  || isNonRecoverableFailedRow (row)
+		  || row.skipReason === 'manual'
+		  ? row
+		  : mergePreviewRow (row, preview))
             }
             catch (requestError)
             {
@@ -547,21 +595,29 @@ const PostImportReviewPage: FC<Props> = ({ user }) => {
 		      errors?: Record<string, string[]>
 		      baseErrors?: string[]
 		  }> (requestError)))
-                continue
+                {
+                  mergeCurrentRow (currentRow.sourceRow, row => ({
+                      ...row,
+                      status: 'error' }))
+                  continue
+                }
               if (requestError.response?.status === 422)
                 {
-                  const rowErrors = {
+                  const rowErrors = compactMessageRecord ({
 		      ...(requestError.response.data.errors ?? { }),
 		      ...(requestError.response.data.baseErrors?.length
 			  ? {
 			      base: requestError.response.data.baseErrors }
-			  : { }) }
+			  : { }) })
-                  previewErrors.set (baseRow.sourceRow, rowErrors)
+                  mergeCurrentRow (currentRow.sourceRow, row => ({
-                  mergeWorkingRow (baseRow.sourceRow, row => ({
                       ...row,
                       validationErrors: rowErrors,
                       status: 'error' }))
                 }
+              else
+                mergeCurrentRow (currentRow.sourceRow, row => ({
+                    ...row,
+                    status: 'error' }))
             }
             finally
             {
@@ -575,20 +631,13 @@ const PostImportReviewPage: FC<Props> = ({ user }) => {
         if (!(active) || previewSequenceRef.current !== previewSequence)
           return
 
-        const nextRows = applyDuplicateUrlErrors (workingRows.map (row => {
+        const latestRows = sessionRef.current?.rows ?? baseSession.rows
-          const rowErrors = previewErrors.get (row.sourceRow)
+        const nextRows = applyDuplicateUrlErrors (latestRows)
-          if (rowErrors == null)
+        await syncSessionUrl (buildSession (nextRows))
-            return row
-          return {
-              ...row,
-              validationErrors: rowErrors,
-              status: 'error' as const }
-        }))
-        await persistSession (buildSession (nextRows))
       }
       finally
       {
-        if (active)
+        if (active && previewSequenceRef.current === previewSequence)
 	  setMetadataLoading (false)
       }
     }
@@ -649,18 +698,19 @@ const PostImportReviewPage: FC<Props> = ({ user }) => {
       : rows
   const existingRows = sortedRows.filter (row => isExistingSkipRow (row))
   const reviewRows = sortedRows.filter (row => !(isExistingSkipRow (row)))
-  const busy = metadataLoading || submitting || loadingRow != null
   const canSubmit =
       rows.every (row => isCompletedReviewRow (row))
       || processableImportRows (rows).length > 0
 
   const toggleManualSkip = async (sourceRow: number, checked: boolean) => {
-    if (busy)
-      return
-
     const currentSession = sessionRef.current
     if (currentSession == null)
       return
+    const currentRow = currentRowBySource (sourceRow, currentSession)
+    if (currentRow == null)
+      return
+    if (rowSkipBusy (currentRow, submitting, loadingRow))
+      return
 
     const nextRows = currentSession.rows.map (row => {
       if (row.sourceRow !== sourceRow)
@@ -674,7 +724,13 @@ const PostImportReviewPage: FC<Props> = ({ user }) => {
 	  existingPostId: checked ? undefined : row.existingPostId,
 	  existingPost: checked ? undefined : row.existingPost }
     })
-    await persistSession (buildSession (nextRows))
+    const nextSession = buildSession (applyDuplicateUrlErrors (nextRows))
+    if (metadataLoading)
+      {
+        commitSessionState (nextSession)
+        return
+      }
+    await syncSessionUrl (nextSession)
   }
 
   const saveDraft = async (
@@ -687,23 +743,26 @@ const PostImportReviewPage: FC<Props> = ({ user }) => {
     const currentSession = sessionRef.current
     if (currentSession == null)
       return { saved: false, row: null }
-    if (!(canEditReviewRow (row)))
+    const currentRow = currentRowBySource (row.sourceRow, currentSession)
+    if (currentRow == null)
+      return { saved: false, row: null }
+    if (!(canEditReviewRow (currentRow)))
       return { saved: false, row: null }
 
     const baseRow =
 	resetRequested
-	? { ...row,
+	? { ...currentRow,
-	    url: row.resetSnapshot.url,
+	    url: currentRow.resetSnapshot.url,
-	    attributes: { ...row.resetSnapshot.attributes },
+	    attributes: { ...currentRow.resetSnapshot.attributes },
-	    provenance: { ...row.resetSnapshot.provenance },
+	    provenance: { ...currentRow.resetSnapshot.provenance },
-	    tagSources: { ...row.resetSnapshot.tagSources },
+	    tagSources: { ...currentRow.resetSnapshot.tagSources },
 	    fieldWarnings: Object.fromEntries (
-		Object.entries (row.resetSnapshot.fieldWarnings)
+		Object.entries (currentRow.resetSnapshot.fieldWarnings)
 		    .map (([key, values]) => [key, [...values]])),
-	    baseWarnings: [...row.resetSnapshot.baseWarnings],
+	    baseWarnings: [...currentRow.resetSnapshot.baseWarnings],
-	    metadataUrl: row.resetSnapshot.metadataUrl,
+	    metadataUrl: currentRow.resetSnapshot.metadataUrl,
 	    thumbnailFile: undefined }
-	: row
+	: currentRow
     const urlChanged = draft.url !== baseRow.url
     const nextRow = buildNextEditedRow (baseRow, draft, urlChanged)
     let candidateRow = nextRow
@@ -724,15 +783,19 @@ const PostImportReviewPage: FC<Props> = ({ user }) => {
 	return { saved: false, row: null }
 
       const mergedRow = mergeDryRunRow (candidateRow, dryRun)
-      const mergedRows = replaceImportRow (latestSession.rows, mergedRow)
+      const mergedRows = applyDuplicateUrlErrors (
-      const nextSession = await persistSession (buildSession (mergedRows))
+	  replaceImportRow (latestSession.rows, mergedRow))
+      const nextSession =
+	  metadataLoading
+	  ? commitSessionState (buildSession (mergedRows))
+	  : await syncSessionUrl (buildSession (mergedRows))
       if (nextSession == null)
 	return { saved: false, row: null }
       const mergedTarget = nextSession.rows.find (
 	  currentRow => currentRow.sourceRow === baseRow.sourceRow)
       if (mergedTarget == null)
 	return { saved: false, row: null }
-      if (Object.keys (mergedTarget.validationErrors).length > 0)
+      if (hasErrorMessages (mergedTarget.validationErrors))
 	return { saved: false, row: mergedTarget }
       return { saved: true, row: null }
     }
@@ -746,7 +809,12 @@ const PostImportReviewPage: FC<Props> = ({ user }) => {
 	{
 	  const errorRow = {
 	      ...candidateRow,
-	      validationErrors: requestError.response.data.errors ?? { },
+	      validationErrors: compactMessageRecord ({
+		  ...(requestError.response.data.errors ?? { }),
+		  ...(requestError.response.data.baseErrors?.length
+		      ? {
+			  base: requestError.response.data.baseErrors }
+		      : { }) }),
 	      baseWarnings: [],
 	      fieldWarnings: { },
 	      status: 'error' as const }
@@ -778,39 +846,48 @@ const PostImportReviewPage: FC<Props> = ({ user }) => {
   }
 
   const editRow = async (row: PostImportRow) => {
-    setEditingRow (row)
+    const currentRow = sessionRef.current?.rows.find (
+	current => current.sourceRow === row.sourceRow)
+    if (currentRow == null)
+      return
+    if (!(canEditReviewRow (currentRow)))
+      return
+    if (rowOperationBusy (currentRow, submitting, loadingRow))
+      return
+
+    setEditingRow (currentRow)
     try
     {
-      await openEditingDialogue (row)
+      await openEditingDialogue (currentRow)
     }
     finally
     {
       setEditingRow (current =>
-	  current?.sourceRow === row.sourceRow
+	  current?.sourceRow === currentRow.sourceRow
 	  ? null
 	  : current)
     }
   }
 
   const retry = async (sourceRow: number) => {
-    if (busy)
-      return
-
     const initialSession = sessionRef.current
     if (initialSession == null)
       return
 
-    setLoadingRow (sourceRow)
     const originalRow = initialSession.rows.find (row => row.sourceRow === sourceRow)
     if (originalRow == null)
-      {
+      return
-	setLoadingRow (null)
+    if (rowOperationBusy (originalRow, submitting, loadingRow))
-	return
+      return
-      }
+
+    setLoadingRow (sourceRow)
     try
     {
       const pendingRows = retryImportRow (initialSession.rows, sourceRow)
-      const pendingSession = await persistSession (buildSession (pendingRows))
+      const pendingSession =
+	  metadataLoading
+	  ? commitSessionState (buildSession (pendingRows))
+	  : await syncSessionUrl (buildSession (pendingRows))
       if (pendingSession == null)
 	return
 
@@ -825,16 +902,20 @@ const PostImportReviewPage: FC<Props> = ({ user }) => {
 	{
 	  const latest = sessionRef.current ?? pendingSession
 	  const restoredRows = replaceImportRow (latest.rows, originalRow)
-	  await persistSession (buildSession (restoredRows))
+	  if (metadataLoading)
+	    commitSessionState (buildSession (restoredRows))
+	  else
+	    await syncSessionUrl (buildSession (restoredRows))
 	  toast ({ title: '登録結果が不完全でした' })
 	  return
 	}
 
       const indexedResults = indexedBulkResults ([target], result.results)
       const latestAfterImport = sessionRef.current ?? pendingSession
-      const nextRows = mergeImportResults (latestAfterImport.rows, indexedResults)
+      const nextRows = applyDuplicateUrlErrors (
+	  mergeImportResults (latestAfterImport.rows, indexedResults))
           .map (row => applyThumbnailWarning (row))
-      const persisted = await persistSession (buildSession (nextRows))
+      const persisted = await syncSessionUrl (buildSession (nextRows))
       if (persisted != null
 	  && persisted.rows.every (row => isCompletedReviewRow (row)))
 	finishImport ()
@@ -843,7 +924,10 @@ const PostImportReviewPage: FC<Props> = ({ user }) => {
     {
       const latest = sessionRef.current ?? initialSession
       const restoredRows = replaceImportRow (latest.rows, originalRow)
-      await persistSession (buildSession (restoredRows))
+      if (metadataLoading)
+	commitSessionState (buildSession (restoredRows))
+      else
+	await syncSessionUrl (buildSession (restoredRows))
       toast ({ title: '再試行に失敗しました' })
     }
     finally
@@ -854,7 +938,7 @@ const PostImportReviewPage: FC<Props> = ({ user }) => {
 
   const submit = async () => {
     const currentSession = sessionRef.current
-    if (currentSession == null || busy)
+    if (currentSession == null || metadataLoading || submitting || loadingRow != null)
       return
     if (currentSession.rows.every (row => isCompletedReviewRow (row)))
       {
@@ -880,9 +964,10 @@ const PostImportReviewPage: FC<Props> = ({ user }) => {
 
       const indexedResults = indexedBulkResults (processingRows, result.results)
       const latestAfterImport = sessionRef.current ?? buildSession (currentSession.rows)
-      const nextRows = mergeImportResults (latestAfterImport.rows, indexedResults)
+      const nextRows = applyDuplicateUrlErrors (
+	  mergeImportResults (latestAfterImport.rows, indexedResults))
           .map (row => applyThumbnailWarning (row))
-      const persisted = await persistSession (buildSession (nextRows))
+      const persisted = await syncSessionUrl (buildSession (nextRows))
       if (persisted != null
 	  && persisted.rows.every (row => isCompletedReviewRow (row)))
 	finishImport ()
@@ -958,10 +1043,10 @@ const PostImportReviewPage: FC<Props> = ({ user }) => {
 			row={row}
 			displayNumber={index + 1}
 			showSkipToggle={true}
-			editDisabled={busy}
+			editDisabled={rowOperationBusy (row, submitting, loadingRow)}
-			retryDisabled={busy}
+			retryDisabled={rowOperationBusy (row, submitting, loadingRow)}
 			skipDisabled={
-			    busy
+			    rowSkipBusy (row, submitting, loadingRow)
 			    || isExistingSkipRow (row)
 			    || row.importStatus === 'created'}
 			onEdit={() => editRow (row)}