Add tootctl preview_cards clean

lib/mastodon/cli/preview_cards.rb

@@ -47,5 +47,39 @@ def remove
 
       say("Removed #{processed} #{link}preview cards (approx. #{number_to_human_size(aggregate)})#{dry_run_mode_suffix}", :green, true)
     end
+
+    option :days, type: :numeric, default: 14
+    option :verbose, type: :boolean, aliases: [:v]
+    option :dry_run, type: :boolean, default: false
+    desc 'clean', 'Clean unused preview card records'
+    long_desc <<-DESC
+      Clean unused preview card records.
+
+      The --days option specifies the number of days after which unused
+      preview cards are deleted. The default is 14 days. Preview cards are
+      reused if the link is reposted within two weeks of the last time,
+      so deleting them too early can result in additional overhead for
+      refetching.
+    DESC
+    def clean
+      time_ago = options[:days].days.ago
+      scope    = ActiveRecord::Base.connection.select_values(ActiveRecord::Base.sanitize_sql_array([
+        "select preview_card_id from preview_cards_statuses ps join preview_cards p on ps.preview_card_id = p.id left join statuses s on ps.status_id = s.id where s.id is null and p.updated_at < :time_ago",
+        { time_ago: time_ago }]))
+
+      processed = 0
+      scope.each_slice(1000) do |preview_card_ids|
+        unless dry_run?
+          PreviewCard.where(id: preview_card_ids).destroy_all
+          ActiveRecord::Base.connection.execute(ActiveRecord::Base.sanitize_sql_array([
+            "delete from preview_cards_statuses where preview_card_id in (:preview_card_ids)",
+            { preview_card_ids: preview_card_ids }]))
+        end
+
+        processed += preview_card_ids.count
+      end
+
+      say("Removed #{processed} PreviewCard records#{dry_run_mode_suffix}", :green)
+    end
   end
 end