download remote custom emojis from reactions

Emoji reactions containing custom emojis from
remote instances were assumed to already have
been downloaded and stored in the database.
This might obviously not be the case.

app/lib/activitypub/activity.rb

@@ -176,4 +176,30 @@ class ActivityPub::Activity
     Rails.logger.info("Rejected #{@json['type']} activity #{@json['id']} from #{@account.uri}#{@options[:relayed_through_actor] && "via #{@options[:relayed_through_actor].uri}"}")
     nil
   end
+
+  # Ensure all emojis declared in the activity's tags are
+  # present in the database and downloaded to the local cache.
+  def process_emoji_tags
+    as_array(@object['tag']).each do |tag|
+      process_single_emoji(tag) if tag['type'] == 'Emoji'
+    end
+  end
+
+  def process_single_emoji(tag)
+    parser = ActivityPub::Parser::CustomEmojiParser.new(tag)
+    return if parser.shortcode.blank? || parser.image_remote_url.blank?
+
+    emoji = CustomEmoji.find_by(shortcode: parser.shortcode, domain: @account.domain)
+    return unless emoji.nil? ||
+                  parser.image_remote_url != emoji.image_remote_url ||
+                  (parser.updated_at && parser.updated_at >= emoji.updated_at)
+
+    begin
+      emoji ||= CustomEmoji.new(domain: @account.domain, shortcode: parser.shortcode, uri: parser.uri)
+      emoji.image_remote_url = parser.image_remote_url
+      emoji.save
+    rescue Seahorse::Client::NetworkingError => e
+      Rails.logger.warn "Error fetching emoji: #{e}"
+    end
+  end
 end

app/lib/activitypub/activity/emoji_react.rb

@@ -9,6 +9,13 @@ class ActivityPub::Activity::EmojiReact < ActivityPub::Activity
               delete_arrived_first?(@json['id']) ||
               @account.reacted?(original_status, name)
 
+    if name =~ /^:.*:$/
+      process_emoji_tags
+
+      name.delete! ':'
+      return if CustomEmoji.find_by(shortcode: name, domain: @account.domain).nil?
+    end
+
     reaction = original_status.status_reactions.create!(account: @account, name: name)
 
     LocalNotificationWorker.perform_async(original_status.account_id, reaction.id, 'StatusReaction', 'reaction')

app/lib/activitypub/activity/like.rb

@@ -5,16 +5,7 @@ class ActivityPub::Activity::Like < ActivityPub::Activity
     original_status = status_from_uri(object_uri)
     return if original_status.nil? || !original_status.account.local? || delete_arrived_first?(@json['id'])
 
-    # misskey delivers reactions as likes and attaches the emoji in _misskey_reaction
-    mk_reaction = @json['_misskey_reaction']
-    unless mk_reaction.nil?
-      custom_emoji = CustomEmoji.find_by(shortcode: mk_reaction, domain: @account.domain)
-      return if @account.reacted?(original_status, mk_reaction, custom_emoji)
-
-      reaction = original_status.status_reactions.create!(account: @account, name: mk_reaction, custom_emoji: custom_emoji)
-      LocalNotificationWorker.perform_async(original_status.account_id, reaction.id, 'StatusReaction', 'reaction')
-      return
-    end
+    return if maybe_process_misskey_reaction(original_status)
 
     return if @account.favourited?(original_status)
 
@@ -23,4 +14,25 @@ class ActivityPub::Activity::Like < ActivityPub::Activity
     LocalNotificationWorker.perform_async(original_status.account_id, favourite.id, 'Favourite', 'favourite')
     Trends.statuses.register(original_status)
   end
+
+  # Misskey delivers reactions as likes with the emoji in _misskey_reaction
+  # see https://misskey-hub.net/ns.html#misskey-reaction for details
+  def maybe_process_misskey_reaction(original_status)
+    name = @json['_misskey_reaction']
+    return false if name.nil?
+
+    custom_emoji = nil
+    if name =~ /^:.*:$/
+      process_emoji_tags
+
+      name.delete! ':'
+      custom_emoji = CustomEmoji.find_by(shortcode: name, domain: @account.domain)
+      return false if custom_emoji.nil? # invalid custom emoji, treat it as a regular like
+    end
+    return true if @account.reacted?(original_status, name, custom_emoji)
+
+    reaction = original_status.status_reactions.create!(account: @account, name: name, custom_emoji: custom_emoji)
+    LocalNotificationWorker.perform_async(original_status.account_id, reaction.id, 'StatusReaction', 'reaction')
+    return true
+  end
 end