import time

import requests
from django.conf import settings
from django.core.cache import cache

from utils.clients.gooyal_notifications_client import AuthenticatedClient
from utils.clients.gooyal_notifications_client.api.push import push_application_application_create

ACCESS_TOKEN_CACHE_KEY = "chat_notifications_access_token"


def login_as_client_credentials() -> dict:
    """
    Client-credentials OAuth2 grant against the gooyal accounts service,
    reusing a cached access token until it's within 5s of expiry.
    """
    cached = cache.get(ACCESS_TOKEN_CACHE_KEY)
    if cached:
        return cached

    data = {
        "grant_type": "client_credentials",
        "scope": settings.OAUTH2_PROVIDER_SCOPES,
    }
    auth = (settings.OAUTH2_PROVIDER_CLIENT_ID, settings.OAUTH2_PROVIDER_CLIENT_SECRET)

    response = requests.post(
        f"{settings.OAUTH2_PROVIDER_BASE_PUBLIC_URL}/token/", data=data, auth=auth
    )
    response.raise_for_status()

    auth_data = response.json()
    if "access_token" in auth_data:
        auth_data["created_at"] = time.time()
        cache.set(
            ACCESS_TOKEN_CACHE_KEY, auth_data, timeout=auth_data.get("expires_in", 300) - 5
        )

    return auth_data


def get_client() -> AuthenticatedClient:
    access_token = login_as_client_credentials()["access_token"]
    return AuthenticatedClient(
        base_url=settings.NOTIFICATIONS_BASE_PUBLIC_URL, token=access_token
    )


class _PushBody:
    """
    Duck-typed request body: push_user is already in the URL and
    application is resolved server-side from the OAuth2 client, so only
    these fields are sent (mirrors the advertising service's client).
    """

    def __init__(self, title: str, message: str, priority: int, extras):
        self._title = title
        self._message = message
        self._priority = priority
        self._extras = extras

    def to_dict(self) -> dict:
        return {
            "title": self._title,
            "message": self._message,
            "priority": self._priority,
            "extras": self._extras,
        }


def push_user(user_uuid, title: str, message: str, priority: int = 5, extras=None):
    """
    Send a push notification to a single user via the gooyal notifications
    service. Requires the `notifications.application.push:send` scope on
    this app's OAuth2 client credentials. Raises on failure — callers
    decide whether a down notifications service should be swallowed.
    """
    client = get_client()
    body = _PushBody(title=title, message=message, priority=priority, extras=extras)
    return push_application_application_create.sync(user_uuid=str(user_uuid), client=client, body=body)