from __future__ import annotations

import logging
import time
from dataclasses import dataclass

import httpx

logger = logging.getLogger(__name__)

TOKEN_URL = "https://api.helpscout.net/v2/oauth2/token"
REFRESH_BUFFER_SECONDS = 300


@dataclass
class HelpScoutToken:
    access_token: str
    token_type: str = "bearer"
    expires_at: float = 0.0


class HelpScoutAuth:
    def __init__(self, app_id: str, app_secret: str):
        self._app_id = app_id
        self._app_secret = app_secret
        self._token: HelpScoutToken | None = None

    @property
    def access_token(self) -> str | None:
        if self._token:
            return self._token.access_token
        return None

    @property
    def auth_header(self) -> dict:
        return {"Authorization": f"Bearer {self.access_token or ''}"}

    @property
    def is_token_valid(self) -> bool:
        return self._token is not None and time.time() < self._token.expires_at - REFRESH_BUFFER_SECONDS

    async def ensure_token(self) -> str:
        if not self.is_token_valid:
            await self._fetch_token()
        return self._token.access_token

    async def force_refresh(self) -> str:
        logger.info("Help Scout: forcing token refresh due to 401")
        await self._fetch_token()
        return self._token.access_token

    async def _fetch_token(self) -> None:
        async with httpx.AsyncClient(timeout=15.0) as client:
            resp = await client.post(
                TOKEN_URL,
                data={
                    "grant_type": "client_credentials",
                    "client_id": self._app_id,
                    "client_secret": self._app_secret,
                },
            )
            resp.raise_for_status()
            data = resp.json()
            expires_in = data.get("expires_in", 172800)
            self._token = HelpScoutToken(
                access_token=data["access_token"],
                token_type=data.get("token_type", "bearer"),
                expires_at=time.time() + expires_in,
            )
            logger.info(
                "Help Scout token obtained: expires_in=%ds, expires_at=%s",
                expires_in,
                time.strftime("%Y-%m-%dT%H:%M:%SZ", time.gmtime(self._token.expires_at)),
            )