#434

backend/app/representations/counts_version_repr.rb

@@ -6,6 +6,7 @@ class CountsVersionRepr
 
   def initialize(rows, resource:, language_code:, at:, inclusive:)
     @rows = rows
+    HistoryAccess.require_many!(rows)
     @at = at
     @inclusive = inclusive
     @resource = resource
@@ -15,6 +16,7 @@ class CountsVersionRepr
     @scripts = master_names(Script)
     @tag_versions = {}
     load_tag_versions if resource == 'posts'
+    load_parent_versions if resource == 'tags'
   end
 
   def serialise
@@ -47,7 +49,7 @@ class CountsVersionRepr
         .uniq
     pairs.each_slice(500) do |batch|
       placeholders = batch.map { '(?, ?)' }.join(', ')
-      scope = TagVersion.all
+      scope = HistoryAccess.visible(TagVersion.all)
       if @at
         scope = scope.where("created_at #{ @inclusive ? '<=' : '<' } ?", @at)
       end
@@ -86,6 +88,31 @@ class CountsVersionRepr
       original_created_before: row.original_created_before&.iso8601 }
   end
 
+  def parent_point(row) = @at || row.created_at
+
+  def load_parent_versions
+    @parent_versions = {}
+    requests = @rows.flat_map do |row|
+      row.parent_tag_ids.to_s.split.map { [_1.to_i, parent_point(row)] }
+    end.uniq
+    requests.each_slice(100) do |batch|
+      queries = batch.map do |id, point|
+        scope = HistoryAccess.visible(TagVersion.where(tag_id: id))
+            .where('created_at <= ?', point)
+            .where('NOT EXISTS (SELECT 1 FROM tag_versions newer ' +
+                'WHERE newer.tag_id = tag_versions.tag_id AND newer.created_at <= ? ' +
+                'AND newer.version_no > tag_versions.version_no)', point)
+        quoted = TagVersion.connection.quote(point.iso8601(6))
+        scope.select("tag_id, name, names, #{ quoted } AS reference_point").to_sql
+      end
+      next if queries.empty?
+
+      TagVersion.connection.select_all(queries.map { "(#{ _1 })" }.join(' UNION ALL ')).each do |value|
+        @parent_versions[[value['tag_id'], value['reference_point']]] = value
+      end
+    end
+  end
+
   def tag(row)
     recorded_names = names(row.names)
     selected = recorded_names.find { _1[:language_code] == @language }
@@ -97,7 +124,12 @@ class CountsVersionRepr
     end
     { name: selected&.fetch(:name) || row.name, names: recorded_names,
       category: row.category, aliases:,
-      parents: row.parent_tag_ids.to_s.split.map { { id: _1.to_i } },
+      parents: row.parent_tag_ids.to_s.split.map do |id|
+        value = @parent_versions[[id.to_i, parent_point(row).iso8601(6)]]
+        snapshots = value && json(value['names'])
+        name = snapshots&.dig(@language, 'name') || value&.fetch('name')
+        { id: id.to_i, name: }
+      end,
       deprecated: row.deprecated_at&.iso8601 }
   end
 end