ChatView: Add the last message to the view.

lib/pleroma/chat.ex

@@ -4,8 +4,11 @@
 
 defmodule Pleroma.Chat do
   use Ecto.Schema
-  import Ecto.Changeset
 
+  import Ecto.Changeset
+  import Ecto.Query
+
+  alias Pleroma.Object
   alias Pleroma.Repo
   alias Pleroma.User
 
@@ -23,6 +26,37 @@ defmodule Pleroma.Chat do
     timestamps()
   end
 
+  def last_message_for_chat(chat) do
+    messages_for_chat_query(chat)
+    |> order_by(desc: :id)
+    |> Repo.one()
+  end
+
+  def messages_for_chat_query(chat) do
+    chat =
+      chat
+      |> Repo.preload(:user)
+
+    from(o in Object,
+      where: fragment("?->>'type' = ?", o.data, "ChatMessage"),
+      where:
+        fragment(
+          """
+          (?->>'actor' = ? and ?->'to' = ?) 
+          OR (?->>'actor' = ? and ?->'to' = ?) 
+          """,
+          o.data,
+          ^chat.user.ap_id,
+          o.data,
+          ^[chat.recipient],
+          o.data,
+          ^chat.recipient,
+          o.data,
+          ^[chat.user.ap_id]
+        )
+    )
+  end
+
   def creation_cng(struct, params) do
     struct
     |> cast(params, [:user_id, :recipient, :unread])