feat(chat): add presence metadata and improve web chat core

- add user last_seen_at with alembic migration and persist on realtime disconnect
- extend chat serialization with private online/last_seen, group members/online, channel subscribers
- add Redis batch presence lookup helper
- update web chat list/header to display status counters and last-seen labels
- improve delivery receipt handling using last_delivered/last_read boundaries
- include chat info panel and related API/type updates

app/chats/repository.py

@@ -105,6 +105,11 @@ async def list_chat_members(db: AsyncSession, *, chat_id: int) -> list[ChatMembe
     return list(result.scalars().all())
 
 
+async def list_chat_member_user_ids(db: AsyncSession, *, chat_id: int) -> list[int]:
+    result = await db.execute(select(ChatMember.user_id).where(ChatMember.chat_id == chat_id))
+    return list(result.scalars().all())
+
+
 async def list_user_chat_ids(db: AsyncSession, *, user_id: int) -> list[int]:
     result = await db.execute(
         select(ChatMember.chat_id).where(ChatMember.user_id == user_id).order_by(ChatMember.chat_id.asc())

app/chats/schemas.py

@@ -18,6 +18,14 @@ class ChatRead(BaseModel):
     is_saved: bool = False
     unread_count: int = 0
     pinned_message_id: int | None = None
+    members_count: int | None = None
+    online_count: int | None = None
+    subscribers_count: int | None = None
+    counterpart_user_id: int | None = None
+    counterpart_name: str | None = None
+    counterpart_username: str | None = None
+    counterpart_is_online: bool | None = None
+    counterpart_last_seen_at: datetime | None = None
     created_at: datetime
 
 

app/chats/service.py

@@ -12,19 +12,41 @@ from app.messages.repository import (
     hide_message_for_user,
     list_chat_message_ids,
 )
+from app.realtime.presence import get_users_online_map
 from app.users.repository import get_user_by_id
 
 
 async def serialize_chat_for_user(db: AsyncSession, *, user_id: int, chat: Chat) -> ChatRead:
     display_title = chat.title
+    members_count: int | None = None
+    online_count: int | None = None
+    subscribers_count: int | None = None
+    counterpart_user_id: int | None = None
+    counterpart_name: str | None = None
+    counterpart_username: str | None = None
+    counterpart_is_online: bool | None = None
+    counterpart_last_seen_at = None
     if chat.is_saved:
         display_title = "Saved Messages"
     elif chat.type == ChatType.PRIVATE:
         counterpart_id = await repository.get_private_counterpart_user_id(db, chat_id=chat.id, user_id=user_id)
         if counterpart_id:
+            counterpart_user_id = counterpart_id
             counterpart = await get_user_by_id(db, counterpart_id)
             if counterpart:
                 display_title = counterpart.name or counterpart.username
+                counterpart_name = counterpart.name
+                counterpart_username = counterpart.username
+                counterpart_last_seen_at = counterpart.last_seen_at
+            presence = await get_users_online_map([counterpart_id])
+            counterpart_is_online = presence.get(counterpart_id, False)
+    else:
+        member_ids = await repository.list_chat_member_user_ids(db, chat_id=chat.id)
+        members_count = len(member_ids)
+        online_presence = await get_users_online_map(member_ids)
+        online_count = sum(1 for is_online in online_presence.values() if is_online)
+        if chat.type == ChatType.CHANNEL:
+            subscribers_count = members_count
 
     unread_count = await repository.get_unread_count_for_chat(db, chat_id=chat.id, user_id=user_id)
 
@@ -40,6 +62,14 @@ async def serialize_chat_for_user(db: AsyncSession, *, user_id: int, chat: Chat)
             "is_saved": chat.is_saved,
             "unread_count": unread_count,
             "pinned_message_id": chat.pinned_message_id,
+            "members_count": members_count,
+            "online_count": online_count,
+            "subscribers_count": subscribers_count,
+            "counterpart_user_id": counterpart_user_id,
+            "counterpart_name": counterpart_name,
+            "counterpart_username": counterpart_username,
+            "counterpart_is_online": counterpart_is_online,
+            "counterpart_last_seen_at": counterpart_last_seen_at,
             "created_at": chat.created_at,
         }
     )