"""Push backends: ntfy (default) + FCM (optional).

``PushBackend`` interface with two implementations:
  - ``FcmBackend``: FCM HTTP v1 via ``httpx`` + a Firebase service account
    (``IRIS_FCM_SERVICE_ACCOUNT``), or a legacy server key
    (``IRIS_FCM_SERVER_KEY``).
  - ``NtfyBackend``: publishes to ``NTFY_TOPIC`` on ``NTFY_SERVER_URL``
    (default ``https://ntfy.sh``) via ``httpx``; the app's listener
    subscribes to the topic.

Selected by ``IRIS_PUSH_BACKEND`` (``ntfy`` default, ``fcm`` optional).
Fired when a frame has no live subscriber; the data payload drives a silent
sync on the device (docs/08-push.md).

Zero new dependencies: ``httpx`` is a hermes core dep. ``google.auth`` is NOT
installed, so the FCM service-account OAuth2 access token is minted directly
with PyJWT + cryptography (both core deps).

Payloads carry no secrets and only a short preview (lock-screen privacy);
full content is fetched via ``sync`` over the authenticated WS.
"""

import json
import logging
import threading
import time
from pathlib import Path
from typing import Any
from urllib.parse import quote

import httpx

logger = logging.getLogger(__name__)

FCM_SCOPE = "https://www.googleapis.com/auth/firebase.messaging"
# Not a secret: the well-known Google OAuth2 token endpoint.
# pi-lens-ignore: S105
FCM_TOKEN_URL = "https://oauth2.googleapis.com/token"  # noqa: S105
FCM_V1_SEND_URL = "https://fcm.googleapis.com/v1/projects/{project_id}/messages:send"
FCM_LEGACY_SEND_URL = "https://fcm.googleapis.com/fcm/send"
# Refresh the cached access token this long before its expiry.
_TOKEN_REFRESH_MARGIN_S = 600.0
_DEFAULT_NTFY_SERVER = "https://ntfy.sh"
_NTFY_BODY_LIMIT = 4096
_HTTP_TIMEOUT_S = 15.0
# HTTP status boundaries: 200 == success; >= 300 == redirect/error range.
_HTTP_OK = 200
_HTTP_ERROR_MIN = 300

_NTFY_PRIORITY = {"high": "5", "normal": "3", "low": "1"}


class PushBackend:
    """Interface: wake one device (FCM token or ntfy topic)."""

    name: str = "push"
    # DeviceRegistry column that carries this backend's target token.
    # Not a secret: a DB column name (string literal), not a credential.
    # pi-lens-ignore: S105, python-hardcoded-secrets
    token_field: str = ""

    def configured(self) -> bool:
        """True when the backend has credentials to send with."""
        raise NotImplementedError

    async def send(  # noqa: PLR0913
        self,
        *,
        device_id: str,
        chat_id: str,
        title: str,
        body: str,
        data: dict[str, Any],
        token: str,
        priority: str = "normal",
        data_only: bool = False,
    ) -> bool:
        """Deliver one push to *token*. Returns True on success.

        ``data`` is the silent-sync payload (``chat_id``, ``kind``,
        ``cursor``, optional ``thread_id``/``message_id``) -- string values
        only on the wire.
        """
        raise NotImplementedError


class FcmBackend(PushBackend):
    """FCM HTTP v1 (service account) or legacy ``/fcm/send`` (server key)."""

    name = "fcm"
    # Not a secret: a DB column name (string literal), not a credential.
    # pi-lens-ignore: S105
    token_field = "fcm_token"  # noqa: S105

    def __init__(
        self,
        service_account: str | None = None,
        server_key: str | None = None,
    ):
        self._sa_path = (service_account or "").strip() or None
        self._server_key = (server_key or "").strip() or None
        self._sa: dict[str, Any] | None = None
        self._sa_failed = False
        self._access_token: str | None = None
        self._token_expiry = 0.0
        self._lock = threading.Lock()

    def configured(self) -> bool:
        if self._server_key:
            return True
        return bool(self._sa_path and Path(self._sa_path).is_file())

    def _load_sa(self) -> dict[str, Any] | None:
        if self._sa is not None:
            return self._sa
        if not self._sa_path or self._sa_failed:
            return None
        try:
            with open(self._sa_path, encoding="utf-8") as f:
                sa = json.load(f)
            if isinstance(sa, dict) and sa.get("client_email") and sa.get("private_key"):
                self._sa = sa
                return sa
        except Exception:
            logger.warning("iris: FCM service account unreadable: %s", self._sa_path)
        self._sa_failed = True
        return None

    async def _authorization(self, client: httpx.AsyncClient) -> str | None:  # noqa: PLR0911
        """Bearer token: the legacy server key, or a cached service-account
        OAuth2 access token (JWT-bearer grant, minted with PyJWT)."""
        if self._server_key:
            return self._server_key
        sa = self._load_sa()
        if sa is None:
            return None
        now = time.time()
        with self._lock:
            if self._access_token and now < self._token_expiry - _TOKEN_REFRESH_MARGIN_S:
                return self._access_token
        import jwt  # PyJWT (core dep)

        claims = {
            "iss": sa["client_email"],
            "scope": FCM_SCOPE,
            "aud": FCM_TOKEN_URL,
            "iat": int(now),
            "exp": int(now) + 3600,
        }
        headers = {"kid": sa["private_key_id"]} if sa.get("private_key_id") else None
        try:
            assertion = jwt.encode(claims, sa["private_key"], algorithm="RS256", headers=headers)
        except Exception:
            logger.warning("iris: FCM JWT mint failed", exc_info=True)
            return None
        try:
            resp = await client.post(
                FCM_TOKEN_URL,
                data={
                    "grant_type": "urn:ietf:params:oauth:grant-type:jwt-bearer",
                    "assertion": assertion,
                },
                timeout=_HTTP_TIMEOUT_S,
            )
        except Exception:
            logger.warning("iris: FCM token exchange failed", exc_info=True)
            return None
        if resp.status_code != _HTTP_OK:
            logger.warning(
                "iris: FCM token exchange HTTP %s: %s",
                resp.status_code,
                resp.text[:200],
            )
            return None
        try:
            data = resp.json()
        except (json.JSONDecodeError, ValueError):
            return None
        token = data.get("access_token")
        if not isinstance(token, str) or not token:
            return None
        with self._lock:
            self._access_token = token
            try:
                self._token_expiry = now + float(data.get("expires_in", 3600))
            except (TypeError, ValueError):
                self._token_expiry = now + 3600.0
        return token

    async def send(  # noqa: PLR0913
        self,
        *,
        device_id: str,
        chat_id: str,
        title: str,
        body: str,
        data: dict[str, Any],
        token: str,
        priority: str = "normal",
        data_only: bool = False,
    ) -> bool:
        if not token:
            return False
        data = {str(k): str(v) for k, v in (data or {}).items()}
        notification = None if data_only else {"title": title or "Iris", "body": body or ""}
        async with httpx.AsyncClient(timeout=_HTTP_TIMEOUT_S) as client:
            if self._server_key:
                payload: dict[str, Any] = {"to": token}
                if notification:
                    payload["notification"] = notification
                if data:
                    payload["data"] = data
                auth = self._server_key
                url = FCM_LEGACY_SEND_URL
            else:
                sa = self._load_sa()
                project_id = (sa or {}).get("project_id")
                if not project_id:
                    return False
                message: dict[str, Any] = {"token": token}
                if notification:
                    message["notification"] = notification
                if data:
                    message["data"] = data
                message["android"] = {"priority": "high" if priority == "high" else "normal"}
                payload = {"message": message}
                auth = await self._authorization(client)
                if auth is None:
                    return False
                url = FCM_V1_SEND_URL.format(project_id=project_id)
            try:
                resp = await client.post(
                    url,
                    json=payload,
                    headers={"Authorization": f"Bearer {auth}"},
                )
            except Exception:
                logger.warning("iris: FCM send failed (network)", exc_info=True)
                return False
        if resp.status_code >= _HTTP_ERROR_MIN:
            # 404 NOT_FOUND = stale/invalid registration token.
            logger.warning("iris: FCM send HTTP %s: %s", resp.status_code, resp.text[:200])
            return False
        return True


class NtfyBackend(PushBackend):
    """ntfy publish (self-host friendly; zero Firebase).

    The structured payload rides in an ``X-Data`` header (JSON) the app's
    listener parses; the message body is the short preview. A private topic
    + ``NTFY_AUTH_TOKEN`` provides the trust boundary (docs/08 §8.7).
    """

    name = "ntfy"
    # Not a secret: a DB column name (string literal), not a credential.
    # pi-lens-ignore: S105
    token_field = "ntfy_topic"  # noqa: S105

    def __init__(
        self,
        topic: str | None = None,
        server_url: str | None = None,
        auth_token: str | None = None,
    ):
        self._topic = (topic or "").strip() or None
        self._server = (server_url or _DEFAULT_NTFY_SERVER).strip().rstrip(
            "/"
        ) or _DEFAULT_NTFY_SERVER
        self._auth_token = (auth_token or "").strip() or None

    @property
    def server_url(self) -> str:
        """The ntfy server this backend publishes to (for app discovery)."""
        return self._server

    def configured(self) -> bool:
        return bool(self._topic)

    async def send(  # noqa: PLR0913
        self,
        *,
        device_id: str,
        chat_id: str,
        title: str,
        body: str,
        data: dict[str, Any],
        token: str,
        priority: str = "normal",
        data_only: bool = False,
    ) -> bool:
        topic = (token or self._topic or "").strip()
        if not topic:
            return False
        headers = {
            "Content-Type": "text/plain; charset=utf-8",
            "X-Title": (title or "Iris")[:512],
            "X-Priority": _NTFY_PRIORITY.get(priority, "3"),
            "X-Tag": "bell",
            "X-Data": json.dumps(data or {}, separators=(",", ":")),
        }
        if self._auth_token:
            headers["Authorization"] = f"Bearer {self._auth_token}"
        text = (body or "")[:_NTFY_BODY_LIMIT]
        url = f"{self._server}/{quote(topic, safe='')}"
        try:
            async with httpx.AsyncClient(timeout=_HTTP_TIMEOUT_S) as client:
                resp = await client.post(url, content=text.encode("utf-8"), headers=headers)
        except Exception:
            logger.warning("iris: ntfy publish failed (network)", exc_info=True)
            return False
        if resp.status_code >= _HTTP_ERROR_MIN:
            logger.warning("iris: ntfy publish HTTP %s: %s", resp.status_code, resp.text[:200])
            return False
        return True


def build_push_backend(  # noqa: PLR0913
    name: str | None,
    *,
    fcm_service_account: str | None = None,
    fcm_server_key: str | None = None,
    ntfy_topic: str | None = None,
    ntfy_server_url: str | None = None,
    ntfy_auth_token: str | None = None,
) -> PushBackend:
    """Select the backend by name (``IRIS_PUSH_BACKEND``; ntfy default).

    ntfy is the default: it keeps push metadata on your own infrastructure.
    FCM is opt-in (``IRIS_PUSH_BACKEND=fcm``) — its metadata (title, device
    token) is routed through Google's servers.
    """
    if (name or "").strip().lower() == "fcm":
        return FcmBackend(service_account=fcm_service_account, server_key=fcm_server_key)
    return NtfyBackend(topic=ntfy_topic, server_url=ntfy_server_url, auth_token=ntfy_auth_token)