REFACTOR: Make chat summary email notifications easier to translate (#19354)

plugins/chat/lib/extensions/user_notifications_extension.rb

@@ -60,67 +60,76 @@ module Chat::UserNotificationsExtension
   end
 
   def summary_subject(user, grouped_messages)
-    channels = grouped_messages.keys
-    grouped_channels = channels.partition { |c| !c.direct_message_channel? }
-    non_dm_channels = grouped_channels.first
+    all_channels = grouped_messages.keys
+    grouped_channels = all_channels.partition { |c| !c.direct_message_channel? }
+    channels = grouped_channels.first
     dm_users = grouped_channels.last.flat_map { |c| grouped_messages[c].map(&:user) }.uniq
 
-    total_count_for_subject = non_dm_channels.size + dm_users.size
-
-    # Prioritize messages from regular channels.
-    first_message_from = non_dm_channels.pop
-    if first_message_from
-      first_message_title = first_message_from.title(user)
-      subject_key = "chat_channel"
+    # Prioritize messages from regular channels over direct messages
+    if channels.any?
+      channel_notification_text(channels, dm_users)
     else
-      subject_key = "direct_message"
-      first_message_from = dm_users.pop
-      first_message_title = first_message_from.username
+      direct_message_notification_text(dm_users)
     end
-
-    subject_opts = {
-      email_prefix: @email_prefix,
-      count: total_count_for_subject,
-      message_title: first_message_title,
-      others:
-        other_channels_text(
-          user,
-          total_count_for_subject,
-          first_message_from,
-          non_dm_channels,
-          dm_users,
-        ),
-    }
-
-    I18n.t(with_subject_prefix(subject_key), **subject_opts)
   end
 
-  def with_subject_prefix(key)
-    "user_notifications.chat_summary.subject.#{key}"
+  private
+
+  def channel_notification_text(channels, dm_users)
+    total_count = channels.size + dm_users.size
+
+    if total_count > 2
+      I18n.t(
+        "user_notifications.chat_summary.subject.chat_channel_more",
+        email_prefix: @email_prefix,
+        channel: channels.first.title,
+        count: total_count - 1
+      )
+    elsif channels.size == 1 && dm_users.size == 0
+      I18n.t(
+        "user_notifications.chat_summary.subject.chat_channel_1",
+        email_prefix: @email_prefix,
+        channel: channels.first.title
+      )
+    elsif channels.size == 1 && dm_users.size == 1
+      I18n.t(
+        "user_notifications.chat_summary.subject.chat_channel_and_direct_message",
+        email_prefix: @email_prefix,
+        channel: channels.first.title,
+        username: dm_users.first.username
+      )
+    elsif channels.size == 2
+      I18n.t(
+        "user_notifications.chat_summary.subject.chat_channel_2",
+        email_prefix: @email_prefix,
+        channel1: channels.first.title,
+        channel2: channels.second.title
+      )
+    end
   end
 
-  def other_channels_text(
-    user,
-    total_count,
-    first_message_from,
-    other_non_dm_channels,
-    other_dm_users
-  )
-    return if total_count <= 1
-    return I18n.t(with_subject_prefix("others"), count: total_count - 1) if total_count > 2
-
-    # The summary contains exactly two messages.
-    if other_non_dm_channels.empty?
-      second_message_from = other_dm_users.first
-      second_message_title = second_message_from.username
+  def direct_message_notification_text(dm_users)
+    case dm_users.size
+    when 1
+      I18n.t(
+        "user_notifications.chat_summary.subject.direct_message_from_1",
+        email_prefix: @email_prefix,
+        username: dm_users.first.username
+      )
+    when 2
+      I18n.t(
+        "user_notifications.chat_summary.subject.direct_message_from_2",
+        email_prefix: @email_prefix,
+        username1: dm_users.first.username,
+        username2: dm_users.second.username
+      )
     else
-      second_message_from = other_non_dm_channels.first
-      second_message_title = second_message_from.title(user)
+      I18n.t(
+        "user_notifications.chat_summary.subject.direct_message_from_more",
+        email_prefix: @email_prefix,
+        username: dm_users.first.username,
+        count: dm_users.size - 1
+      )
     end
-
-    second_message_is_from_channel = first_message_from.class == second_message_from.class
-    return second_message_title if second_message_is_from_channel
-
-    I18n.t(with_subject_prefix("other_direct_message"), dm_title: second_message_title)
   end
 end