backend: add push token API and FCM delivery pipeline

app/notifications/tasks.py

@@ -1,15 +1,100 @@
+import asyncio
+import json
 import logging
+from typing import Any
+
+import firebase_admin
+from firebase_admin import credentials, messaging
 
 from app.celery_app import celery_app
+from app.config.settings import settings
+from app.database.session import AsyncSessionLocal
+from app.notifications.repository import delete_push_device_token, list_push_tokens_for_user
 
 logger = logging.getLogger(__name__)
 
 
+_firebase_app: firebase_admin.App | None = None
+
+
+def _get_firebase_app() -> firebase_admin.App | None:
+    global _firebase_app
+    if _firebase_app is not None:
+        return _firebase_app
+    if not settings.firebase_enabled:
+        return None
+    cert_payload: dict[str, Any] | None = None
+    if settings.firebase_credentials_json:
+        try:
+            cert_payload = json.loads(settings.firebase_credentials_json)
+        except json.JSONDecodeError:
+            logger.warning("FCM disabled: invalid FIREBASE_CREDENTIALS_JSON")
+            return None
+    elif settings.firebase_credentials_path:
+        cert_payload = settings.firebase_credentials_path
+    else:
+        logger.warning("FCM disabled: credentials are not configured")
+        return None
+
+    try:
+        cred = credentials.Certificate(cert_payload)  # type: ignore[arg-type]
+        _firebase_app = firebase_admin.initialize_app(cred)
+        return _firebase_app
+    except Exception:
+        logger.exception("Failed to initialize Firebase app")
+        return None
+
+
+async def _load_tokens(user_id: int) -> list[tuple[str, str]]:
+    async with AsyncSessionLocal() as db:
+        records = await list_push_tokens_for_user(db, user_id=user_id)
+        return [(record.platform, record.token) for record in records]
+
+
+async def _delete_invalid_token(user_id: int, platform: str, token: str) -> None:
+    async with AsyncSessionLocal() as db:
+        await delete_push_device_token(db, user_id=user_id, platform=platform, token=token)
+        await db.commit()
+
+
+def _send_fcm_to_user(user_id: int, title: str, body: str, data: dict[str, Any]) -> None:
+    app = _get_firebase_app()
+    if app is None:
+        logger.info("Skipping FCM send for user=%s: Firebase disabled", user_id)
+        return
+
+    tokens = asyncio.run(_load_tokens(user_id))
+    if not tokens:
+        return
+
+    string_data = {str(key): str(value) for key, value in data.items()}
+    for platform, token in tokens:
+        webpush = None
+        if platform == "web":
+            webpush = messaging.WebpushConfig(
+                fcm_options=messaging.WebpushFCMOptions(link=settings.firebase_webpush_link)
+            )
+        message = messaging.Message(
+            token=token,
+            notification=messaging.Notification(title=title, body=body),
+            data=string_data,
+            webpush=webpush,
+        )
+        try:
+            messaging.send(message, app=app)
+        except messaging.UnregisteredError:
+            asyncio.run(_delete_invalid_token(user_id=user_id, platform=platform, token=token))
+        except messaging.SenderIdMismatchError:
+            asyncio.run(_delete_invalid_token(user_id=user_id, platform=platform, token=token))
+        except Exception:
+            logger.exception("FCM send failed for user=%s platform=%s", user_id, platform)
+
+
 @celery_app.task(name="notifications.send_push")
 def send_push_notification_task(user_id: int, title: str, body: str, data: dict) -> None:
-    logger.info("PUSH user=%s title=%s body=%s data=%s", user_id, title, body, data)
+    _send_fcm_to_user(user_id=user_id, title=title, body=body, data=data)
 
 
 @celery_app.task(name="notifications.send_mention")
 def send_mention_notification_task(user_id: int, title: str, body: str, data: dict) -> None:
-    logger.info("MENTION user=%s title=%s body=%s data=%s", user_id, title, body, data)
+    _send_fcm_to_user(user_id=user_id, title=title, body=body, data=data)