feat(chat): 聊天消息预览

core/routers/chat/services.py

@@ -41,16 +41,12 @@ async def get_user_active_direct_chats(
     return None
 
 
-async def get_unread_messages_per_chat(
-        db_session: AsyncSession, chats: list[Chat], login_user: LoginUser
-) -> list[dict]:
-    """获取聊天未读消息数"""
-    unread_messages_info_per_chat: dict[int, dict] = {chat.id: {'message_count': 0} for chat in chats}
-
+async def get_chat_unread_messages_count(db_session: AsyncSession, login_user: LoginUser, chats):
+    """查询未读消息的预览"""
     # 查询消息情况
     read_status_alias = aliased(ReadStatus)
     query = (
-        select(Message.id, Message.chat_id, Message.content, Message.message_type, func.count().label("message_count"))
+        select(Message.chat_id, func.count().label("message_count"))
         .join(
             read_status_alias,
             and_(read_status_alias.user_id == login_user.user_id, read_status_alias.chat_id == Message.chat_id),
@@ -59,29 +55,71 @@ async def get_unread_messages_per_chat(
             and_(
                 Message.user_id != login_user.user_id,
                 Message.id > func.coalesce(read_status_alias.last_read_message_id, 0),
-                Message.chat_id.in_(unread_messages_info_per_chat),
+                Message.chat_id.in_(chats),
             )
         )
-        .order_by(Message.created_at.desc())
         .group_by(Message.chat_id)
     )
+
     result = await db_session.execute(query)
     unread_messages_info = result.fetchall()
+    return unread_messages_info
 
-    for messages_info in unread_messages_info:
-        unread_messages_info_per_chat[messages_info[1]] = {
-            'message': {
-                'id': messages_info[0],
-                'message_type': messages_info[3],
-                'content': messages_info[2],
-            },
-            'message_count': messages_info[4],
+
+async def get_chat_messages_preview(db_session: AsyncSession, chats):
+    """查询未读消息的预览"""
+    latest_subquery = (
+        select(
+            Message.chat_id,
+            func.max(Message.created_at).label("max_created")
+        )
+        .group_by(Message.chat_id)
+        .subquery()
+    )
+
+    LatestMessage = aliased(Message)
+
+    query = (
+        select(LatestMessage)
+        .join(latest_subquery,
+              (LatestMessage.chat_id == latest_subquery.c.chat_id) &
+              (LatestMessage.created_at == latest_subquery.c.max_created))
+    )
+    result = await db_session.execute(query)
+    unread_messages_info = result.scalars().all()
+    return unread_messages_info
+
+
+async def get_unread_messages_per_chat(
+        db_session: AsyncSession, chats: list[Chat], login_user: LoginUser
+) -> list[dict]:
+    """获取聊天未读消息数和消息预览"""
+    messages_info_per_chat: dict[int, dict] = {chat.id: {'message_count': 0} for chat in chats}
+
+    # 未读消息数和预览
+    unread_messages_count = await get_chat_unread_messages_count(
+        db_session, login_user, messages_info_per_chat
+    )
+    for messages_info in unread_messages_count:
+        messages_info_per_chat[messages_info[0]] = {
+            'message_count': messages_info[1],
         }
 
+    # 已读消息预览
+    no_unread_message_chats = [
+        chat_id
+        for chat_id, message_info in messages_info_per_chat.items() if message_info.get('message') is None
+    ]
+    messages_info = await get_chat_messages_preview(db_session, no_unread_message_chats)
+    for message_info in messages_info:
+        messages_info_per_chat[message_info.chat_id].update({
+            'message': message_info
+        })
+
     results = []
     for chat in chats:
         users = [user for user in await chat.awaitable_attrs.users if user.user_id != login_user.user_id]
-        messages_info = unread_messages_info_per_chat[chat.id]
+        messages_info = messages_info_per_chat[chat.id]
         results.append(dict(
             chat_guid=chat.guid,
             created_at=format_date(chat.created_at),