add "on_client_connected" callback

server/src/server.py

@@ -1,14 +1,18 @@
 import asyncio
 import logging.config
 import uuid
+import datetime as dt
 
 from server.src.handlers import error_handler, send_message_handler, broadcast_message_handler, \
     unknown_action_handler, logout_handler
-from server.src.models.client import ClientManager
+from server.src.models.client import ClientManager, Client
 from server.src.models.request import Request
 from server.src.router import Router
 from server.src.settings import ServerSettings
 from shared.schemas.actions import ActionFrame, ActionTypes
+from shared.schemas.notifications import NotificationFrame, PrivateMessageNotificationPayload, \
+    PrivateMessageNotificationFrame
+from shared.schemas.types import UserId
 
 
 class Server:
@@ -27,7 +31,7 @@ def __init__(self, settings: ServerSettings) -> None:
 
     async def start(self) -> None:
         self._server_logger.info("Starting server on %s:%s...", self._settings.host, self._settings.port)
-        self._server = await asyncio.start_server(self._on_client_connected, self._settings.host, self._settings.port)
+        self._server = await asyncio.start_server(self._connection_callback, self._settings.host, self._settings.port)
         self._server_logger.info("Server is started")
 
     async def serve(self) -> None:
@@ -47,9 +51,10 @@ async def stop(self) -> None:
         self._server = None
         self._server_logger.debug("Server is stopped")
 
-    async def _on_client_connected(self, reader: asyncio.StreamReader, writer: asyncio.StreamWriter) -> None:
+    async def _connection_callback(self, reader: asyncio.StreamReader, writer: asyncio.StreamWriter) -> None:
         client = self._clients.create(reader, writer)
         self._server_logger.info("New connection from %s", client)
+        await self.on_client_connected(client)
         while True:
             raw = await client.listen()
             request = Request(
@@ -61,6 +66,15 @@ async def _on_client_connected(self, reader: asyncio.StreamReader, writer: async
             await self._router.handle(request)
             request.logger.debug("Request '%s' has been handled", request)
 
+    async def on_client_connected(self, client: Client) -> None:
+        payload = PrivateMessageNotificationPayload(
+            text=f"Hello, {client.user.id}!",
+            sender=UserId("SERVER"),
+            to=client.user.id,
+            created_at=dt.datetime.now(dt.UTC),
+        )
+        await client.send(PrivateMessageNotificationFrame(payload=payload))
+
     def _setup_routes(self, router: Router) -> None:
         router.register_action_handler(ActionTypes.BROADCAST_MESSAGE, broadcast_message_handler) \
             .register_action_handler(ActionTypes.SEND_MESSAGE, send_message_handler) \