import logging
from django.conf import settings

logger = logging.getLogger(__name__)

_app = None


def _get_app():
    global _app
    if _app is not None:
        return _app

    credentials_file = settings.FIREBASE_CREDENTIALS_FILE
    if not credentials_file:
        return None

    import firebase_admin
    from firebase_admin import credentials

    try:
        cred = credentials.Certificate(credentials_file)
        _app = firebase_admin.initialize_app(cred)
    except Exception:
        logger.exception("Failed to initialise Firebase app")
        return None

    return _app


def send_notification(fcm_token, *, title, body, data=None):
    """
    Send a single FCM push notification.
    Silently no-ops if Firebase is not configured (e.g. in development).
    `data` values must all be strings.
    """
    if not fcm_token:
        return

    app = _get_app()
    if app is None:
        logger.debug("FCM not configured — skipping notification: %s", title)
        return

    from firebase_admin import messaging

    message = messaging.Message(
        notification=messaging.Notification(title=title, body=body),
        data={k: str(v) for k, v in (data or {}).items()},
        token=fcm_token,
    )
    try:
        messaging.send(message)
    except Exception:
        logger.exception("Failed to send FCM notification to token %s", fcm_token[:10])