backend/db/seeds.rb

@@ -8,6 +8,43 @@
 #     MovieGenre.find_or_create_by!(name: genre_name)
 #   end
 
+post_url_sanitisation_rules = [
+  { priority: 10,
+    source_pattern: '\Ahttps?://youtu\.be/([^/?#]+)(?:[?#].*)?\z',
+    replacement: 'https://www.youtube.com/watch?v=\1' },
+  { priority: 20,
+    source_pattern: '\Ahttps?://(?:www\.|m\.)?youtube\.com/live/([^/?#]+)(?:[?#].*)?\z',
+    replacement: 'https://www.youtube.com/watch?v=\1' },
+  { priority: 30,
+    source_pattern: '\Ahttps?://(?:www\.|m\.)?youtube\.com/shorts/([^/?#]+)(?:[?#].*)?\z',
+    replacement: 'https://www.youtube.com/watch?v=\1' },
+  { priority: 40,
+    source_pattern: '\Ahttps?://(?:www\.|m\.)?youtube\.com/embed/([^/?#]+)(?:[?#].*)?\z',
+    replacement: 'https://www.youtube.com/watch?v=\1' },
+  { priority: 50,
+    source_pattern:
+        '\Ahttps?://(?:www\.|m\.)?youtube\.com/watch\?(?:[^#&]+&)*v=([^&#]+)(?:[&#].*)?\z',
+    replacement: 'https://www.youtube.com/watch?v=\1' },
+  { priority: 60,
+    source_pattern: '\Ahttps?://nico\.ms/([^/?#]+)(?:[?#].*)?\z',
+    replacement: 'https://www.nicovideo.jp/watch/\1' },
+  { priority: 70,
+    source_pattern: '\Ahttps?://(?:www\.)?nicovideo\.jp/watch/([^?#/]+)(?:[?#].*)?\z',
+    replacement: 'https://www.nicovideo.jp/watch/\1' }
+]
+
+post_url_sanitisation_rule_scope = PostUrlSanitisationRule.unscoped
+
+post_url_sanitisation_rules.each do |attributes|
+  priority = attributes.fetch(:priority)
+  source_pattern = attributes.fetch(:source_pattern)
+
+  next if post_url_sanitisation_rule_scope.exists?(priority:)
+  next if post_url_sanitisation_rule_scope.exists?(source_pattern:)
+
+  post_url_sanitisation_rule_scope.create!(attributes)
+end
+
 material_sync_source_uri = ENV['MATERIAL_SYNC_SOURCE_URI']
 material_sync_source_file_id = ENV['MATERIAL_SYNC_SOURCE_FILE_ID']
 

backend/spec/db/seeds_spec.rb

@@ -0,0 +1,65 @@
+require 'rails_helper'
+
+RSpec.describe 'database seeds' do
+  before do
+    PostUrlSanitisationRule.unscoped.delete_all
+  end
+
+  it 'registers the initial post URL sanitisation rules' do
+    load_seeds
+
+    urls = {
+      'https://youtu.be/abc123?si=share' => youtube_url('abc123'),
+      'https://www.youtube.com/live/abc123?t=10' => youtube_url('abc123'),
+      'https://youtube.com/shorts/abc123?feature=share' => youtube_url('abc123'),
+      'https://m.youtube.com/embed/abc123' => youtube_url('abc123'),
+      'https://youtube.com/watch?feature=share&v=abc123&t=10' => youtube_url('abc123'),
+      'https://nico.ms/sm123?from=share#fragment' => nico_url('sm123'),
+      'https://www.nicovideo.jp/watch/sm123?ref=share#fragment' => nico_url('sm123')
+    }
+
+    expect(PostUrlSanitisationRule.count).to eq(7)
+    urls.each do |url, canonical_url|
+      expect(PostUrlSanitisationRule.sanitise(url)).to eq(canonical_url)
+    end
+  end
+
+  it 'does not overwrite or restore an existing rule' do
+    rule = PostUrlSanitisationRule.create!(
+      priority: 10,
+      source_pattern: '\Ahttps://example\.com/custom\z',
+      replacement: 'https://example.com/replacement'
+    )
+    rule.discard!
+    original_attributes = rule.reload.attributes
+
+    2.times { load_seeds }
+
+    persisted_rule = PostUrlSanitisationRule.unscoped.find(10)
+    expect(persisted_rule.attributes).to eq(original_attributes)
+    expect(PostUrlSanitisationRule.unscoped.count).to eq(7)
+  end
+
+  it 'does not duplicate a rule moved to another priority' do
+    source_pattern = '\Ahttps?://youtu\.be/([^/?#]+)(?:[?#].*)?\z'
+    PostUrlSanitisationRule.create!(
+      priority: 80,
+      source_pattern:,
+      replacement: 'https://example.com/custom/\1'
+    )
+
+    load_seeds
+
+    rules = PostUrlSanitisationRule.unscoped
+    expect(rules.where(source_pattern:).count).to eq(1)
+    expect(rules.find(80).replacement).to eq('https://example.com/custom/\1')
+  end
+
+  def load_seeds
+    load Rails.root.join('db/seeds.rb')
+  end
+
+  def youtube_url(video_id) = "https://www.youtube.com/watch?v=#{ video_id }"
+
+  def nico_url(video_id) = "https://www.nicovideo.jp/watch/#{ video_id }"
+end

backend/spec/models/post_spec.rb

@@ -0,0 +1,68 @@
+require 'rails_helper'
+
+RSpec.describe Post, type: :model do
+  before do
+    PostUrlSanitisationRule.unscoped.delete_all
+  end
+
+  describe 'URL normalisation' do
+    it 'normalises the HTTP URL before applying sanitisation rules' do
+      PostUrlSanitisationRule.create!(
+        priority: 10,
+        source_pattern: '\\Ahttps://example\\.com/videos/([^/]+)\\z',
+        replacement: 'https://example.com/watch/\\1'
+      )
+
+      post = described_class.create!(
+        title: 'normalised URL',
+        url: '  https://EXAMPLE.com/videos/123/  '
+      )
+
+      expect(post.url).to eq('https://example.com/watch/123')
+    end
+
+    it 'does not normalise an unchanged URL when another attribute changes' do
+      post = create(:post)
+      post.update_column(:url, 'https://EXAMPLE.com/unchanged/')
+
+      post.update!(title: 'updated title')
+
+      expect(post.reload.url).to eq('https://EXAMPLE.com/unchanged/')
+    end
+
+    it 'validates the sanitised URL length' do
+      path = 'a' * 375
+
+      PostUrlSanitisationRule.create!(
+        priority: 10,
+        source_pattern: '\\Ahttps://example\\.com/(a+)\\z',
+        replacement: 'https://example.com/\\1\\1'
+      )
+
+      post = described_class.new(
+        title: 'long URL',
+        url: "https://example.com/#{ path }"
+      )
+
+      expect(post).to be_invalid
+      expect(post.errors.details.fetch(:url)).to include(
+        error: :too_long,
+        count: 768
+      )
+    end
+
+    it 'validates uniqueness after sanitisation' do
+      PostUrlSanitisationRule.create!(
+        priority: 10,
+        source_pattern: '\\Ahttps://example\\.com/alias\\z',
+        replacement: 'https://example.com/canonical'
+      )
+      create(:post, url: 'https://example.com/canonical')
+
+      post = described_class.new(title: 'duplicate URL', url: 'https://example.com/alias')
+
+      expect(post).to be_invalid
+      expect(post.errors.details.fetch(:url)).to include(error: :taken, value: post.url)
+    end
+  end
+end

backend/spec/models/post_url_sanitisation_rule_spec.rb

@@ -0,0 +1,265 @@
+require 'rails_helper'
+
+RSpec.describe PostUrlSanitisationRule, type: :model do
+  before do
+    described_class.unscoped.delete_all
+  end
+
+  describe 'validations' do
+    it 'requires a source pattern' do
+      rule = described_class.new(priority: 10, source_pattern: nil, replacement: '')
+
+      expect(rule).to be_invalid
+      expect(rule.errors.details.fetch(:source_pattern)).to eq([{ error: :blank }])
+    end
+
+    it 'requires a unique source pattern' do
+      described_class.create!(priority: 10, source_pattern: 'source', replacement: 'first')
+      rule = described_class.new(
+        priority: 20,
+        source_pattern: 'source',
+        replacement: 'second'
+      )
+
+      expect(rule).to be_invalid
+      expect(rule.errors.details.fetch(:source_pattern)).to include(
+        error: :taken,
+        value: 'source'
+      )
+    end
+
+    it 'rejects an invalid regexp' do
+      rule = described_class.new(priority: 10, source_pattern: '[', replacement: '')
+
+      expect(rule).to be_invalid
+      expect(rule.errors[:source_pattern]).to include('変な正規表現だね〜（笑）')
+    end
+  end
+
+  describe '.sanitise' do
+    it 'applies each active rule once in priority order' do
+      described_class.create!(priority: 30, source_pattern: 'c', replacement: 'd')
+      described_class.create!(priority: 10, source_pattern: 'a', replacement: 'aa')
+      described_class.create!(priority: 20, source_pattern: 'aa', replacement: 'c')
+      discarded = described_class.create!(
+        priority: 5,
+        source_pattern: '.',
+        replacement: 'discarded'
+      )
+      discarded.discard!
+
+      expect(described_class.sanitise('a')).to eq('d')
+    end
+
+    it 'canonicalises the initial YouTube and Nico URL forms' do
+      create_initial_rules
+
+      urls = {
+        'https://youtu.be/abc123?si=share' => youtube_url('abc123'),
+        'https://www.youtube.com/live/abc123?t=10' => youtube_url('abc123'),
+        'https://youtube.com/shorts/abc123?feature=share' => youtube_url('abc123'),
+        'https://m.youtube.com/embed/abc123' => youtube_url('abc123'),
+        'https://youtube.com/watch?feature=share&v=abc123&t=10' => youtube_url('abc123'),
+        'https://nico.ms/sm123?from=share#fragment' => nico_url('sm123'),
+        'https://www.nicovideo.jp/watch/sm123?ref=share#fragment' => nico_url('sm123')
+      }
+
+      urls.each do |url, canonical_url|
+        expect(described_class.sanitise(url)).to eq(canonical_url)
+      end
+    end
+  end
+
+  describe '.apply!' do
+    it 'locks posts in ID order and updates through temporary URLs' do
+      first = create(:post, url: 'https://example.com/source/1')
+      second = create(:post, url: 'https://example.com/source/2')
+      create_source_rule
+      sql = capture_sql { described_class.apply! }
+
+      lock_sql = sql.find { _1.match?(/SELECT .*posts.*FOR UPDATE/i) }
+      expect(lock_sql).to match(/ORDER BY .*posts.*id.* ASC/i)
+      expect(sql.grep(/post-url-sanitising\.invalid/).size).to eq(2)
+      expect(first.reload.url).to eq('https://example.com/canonical/1')
+      expect(second.reload.url).to eq('https://example.com/canonical/2')
+    end
+
+    it 'loads and compiles rules only once' do
+      create(:post, url: 'https://example.com/source/1')
+      create(:post, url: 'https://example.com/source/2')
+      create_source_rule
+
+      expect(described_class).to receive(:rules).once.and_call_original
+
+      described_class.apply!
+    end
+
+    it 'does not change post versions, version_no, or updated_at' do
+      post = create(:post, url: 'https://example.com/source/1')
+      post.update_columns(version_no: 7, updated_at: 1.day.ago)
+      original_updated_at = post.reload.updated_at
+      create_source_rule
+
+      expect { described_class.apply! }.not_to change(PostVersion, :count)
+
+      post.reload
+      expect(post.url).to eq('https://example.com/canonical/1')
+      expect(post.version_no).to eq(7)
+      expect(post.updated_at).to eq(original_updated_at)
+    end
+
+    invalid_urls = {
+      'a blank URL' => '',
+      'an unparseable URL' => 'https://[',
+      'a non-HTTP URL' => 'ftp://example.com/file',
+      'an HTTP URL without a host' => 'https:/path'
+    }
+
+    invalid_urls.each do |description, sanitised_url|
+      it "rolls back every update when sanitisation produces #{ description }" do
+        valid_post = create(:post, url: 'https://example.com/source/1')
+        invalid_post = create(:post, url: 'https://example.com/invalid')
+        create_source_rule
+        described_class.create!(
+          priority: 20,
+          source_pattern: '\\Ahttps://example\\.com/invalid\\z',
+          replacement: sanitised_url
+        )
+
+        expect { described_class.apply! }
+            .to raise_error(described_class::InvalidUrlError) { |error|
+          expect(error.invalid_rows).to eq([
+            { post_id: invalid_post.id,
+              original_url: 'https://example.com/invalid',
+              sanitised_url: }
+          ])
+        }
+        expect(valid_post.reload.url).to eq('https://example.com/source/1')
+        expect(invalid_post.reload.url).to eq('https://example.com/invalid')
+      end
+    end
+
+    it 'rolls back every update when sanitisation produces a URL longer than 768 characters' do
+      path = 'a' * 375
+      original_url = "https://example.com/#{ path }"
+      sanitised_url = "https://example.com/#{ path }#{ path }"
+      valid_post = create(:post, url: 'https://example.com/source/1')
+      invalid_post = create(:post, url: original_url)
+      create_source_rule
+      described_class.create!(
+        priority: 20,
+        source_pattern: '\\Ahttps://example\\.com/(a+)\\z',
+        replacement: 'https://example.com/\\1\\1'
+      )
+
+      expect { described_class.apply! }
+          .to raise_error(described_class::InvalidUrlError) { |error|
+        expect(error.invalid_rows).to eq([
+          { post_id: invalid_post.id,
+            original_url:,
+            sanitised_url: }
+        ])
+      }
+      expect(valid_post.reload.url).to eq('https://example.com/source/1')
+      expect(invalid_post.reload.url).to eq(original_url)
+    end
+
+    it 'rejects sanitised URL collisions case-insensitively without changing posts' do
+      source = create(:post, url: 'https://example.com/source/Foo')
+      canonical = create(:post, url: 'https://example.com/canonical/foo')
+      create_source_rule
+
+      expect { described_class.apply! }
+          .to raise_error(described_class::UrlConflictError) { |error|
+        expect(error.conflicts).to contain_exactly(
+          { url: 'https://example.com/canonical/Foo',
+            post_id: source.id,
+            original_url: 'https://example.com/source/Foo' },
+          { url: 'https://example.com/canonical/foo',
+            post_id: canonical.id,
+            original_url: 'https://example.com/canonical/foo' }
+        )
+      }
+      expect(source.reload.url).to eq('https://example.com/source/Foo')
+      expect(canonical.reload.url).to eq('https://example.com/canonical/foo')
+      expect(Post.count).to eq(2)
+    end
+
+    it 'converts a persisted URL constraint race into UrlConflictError' do
+      post = create(:post, url: 'https://example.com/source/1')
+      create_source_rule
+      conflict = { url: 'https://example.com/canonical/1',
+                   post_id: post.id,
+                   original_url: post.url }
+      database_error = ActiveRecord::RecordNotUnique.new('duplicate URL')
+      allow_any_instance_of(ActiveRecord::Relation)
+          .to receive(:update_all).and_raise(database_error)
+      allow(described_class).to receive(:build_persisted_conflicts).and_return([conflict])
+
+      expect { described_class.apply! }
+          .to raise_error(described_class::UrlConflictError) { |error|
+        expect(error.conflicts).to eq([conflict])
+        expect(error.cause).to equal(database_error)
+      }
+      expect(post.reload.url).to eq('https://example.com/source/1')
+    end
+
+    it 're-raises an unidentified RecordNotUnique error' do
+      post = create(:post, url: 'https://example.com/source/1')
+      create_source_rule
+      database_error = ActiveRecord::RecordNotUnique.new('another unique constraint')
+      allow_any_instance_of(ActiveRecord::Relation)
+          .to receive(:update_all).and_raise(database_error)
+      allow(described_class).to receive(:build_persisted_conflicts).and_return([])
+
+      expect { described_class.apply! }.to raise_error(database_error)
+      expect(post.reload.url).to eq('https://example.com/source/1')
+    end
+  end
+
+  def capture_sql
+    statements = []
+    subscriber = lambda do |_name, _start, _finish, _id, payload|
+      binds = payload.fetch(:binds, []).map { _1.value_for_database.to_s }
+      statements << ([payload.fetch(:sql)] + binds).join(' ')
+    end
+    ActiveSupport::Notifications.subscribed(subscriber, 'sql.active_record') { yield }
+    statements
+  end
+
+  def create_source_rule
+    described_class.create!(
+      priority: 10,
+      source_pattern: '\\Ahttps://example\\.com/source/(.+)\\z',
+      replacement: 'https://example.com/canonical/\\1'
+    )
+  end
+
+  def create_initial_rules
+    rules = [
+      ['\\Ahttps?://youtu\\.be/([^/?#]+)(?:[?#].*)?\\z', youtube_url('\\1')],
+      ['\\Ahttps?://(?:www\\.|m\\.)?youtube\\.com/live/([^/?#]+)(?:[?#].*)?\\z',
+       youtube_url('\\1')],
+      ['\\Ahttps?://(?:www\\.|m\\.)?youtube\\.com/shorts/([^/?#]+)(?:[?#].*)?\\z',
+       youtube_url('\\1')],
+      ['\\Ahttps?://(?:www\\.|m\\.)?youtube\\.com/embed/([^/?#]+)(?:[?#].*)?\\z',
+       youtube_url('\\1')],
+      ['\\Ahttps?://(?:www\\.|m\\.)?youtube\\.com/watch\\?(?:[^#&]+&)*' \
+       'v=([^&#]+)(?:[&#].*)?\\z', youtube_url('\\1')],
+      ['\\Ahttps?://nico\\.ms/([^/?#]+)(?:[?#].*)?\\z', nico_url('\\1')],
+      ['\\Ahttps?://(?:www\\.)?nicovideo\\.jp/watch/([^?#/]+)(?:[?#].*)?\\z',
+       nico_url('\\1')]
+    ]
+    rules.each_with_index do |(source_pattern, replacement), index|
+      described_class.create!(
+        priority: (index + 1) * 10,
+        source_pattern:,
+        replacement:
+      )
+    end
+  end
+
+  def youtube_url(video_id) = "https://www.youtube.com/watch?v=#{ video_id }"
+
+  def nico_url(video_id) = "https://www.nicovideo.jp/watch/#{ video_id }"
+end

backend/spec/tasks/nico_export_spec.rb

@@ -62,7 +62,7 @@ RSpec.describe 'nico:export' do
 
     it 'deduplicates video ids' do
       create_post('https://www.nicovideo.jp/watch/sm12345')
-      create_post('https://www.nicovideo.jp/watch/sm12345?from=1')
+      create_post('https://sp.nicovideo.jp/watch/sm12345')
 
       expect(Open3).to receive(:capture3) do |_env, *args, **_kwargs|
         expect(args.drop(3)).to eq(['sm12345'])