// Host-side Spotify connection — Authorization Code flow, refresh token
// persisted server-side. Same shape as goonk's api/routes/spotify.mjs
// (a proven pattern in this family), not the guest PKCE flow used
// elsewhere in this app — this is a single, long-lived connection to
// the host's own account, not a per-visitor login.
import { Router } from 'express';
import { readFile, writeFile, mkdir } from 'fs/promises';
import { join, dirname } from 'path';
import { fileURLToPath } from 'url';
import crypto from 'crypto';

const __dirname = dirname(fileURLToPath(import.meta.url));
const router = Router();

const CLIENT_ID = process.env.SPOTIFY_CLIENT_ID;
const CLIENT_SECRET = process.env.SPOTIFY_CLIENT_SECRET;
const REDIRECT_URI = process.env.SPOTIFY_HOST_REDIRECT_URI || 'http://127.0.0.1:3010/api/spotify/callback';
// playlist-read-*: list/read the host's own playlists as a song pool.
// user-read-currently-playing + user-read-playback-state: the live
// now-playing auto-call poller.
const SCOPES = 'playlist-read-private playlist-read-collaborative user-read-currently-playing user-read-playback-state';

const TOKEN_FILE = join(__dirname, '..', 'data', 'host-token.json');

let accessToken = null;
let accessTokenExpiresAt = 0;
let refreshToken = null;

async function loadRefreshToken() {
  if (refreshToken) return refreshToken;
  try {
    const raw = await readFile(TOKEN_FILE, 'utf8');
    refreshToken = JSON.parse(raw).refresh_token;
  } catch {
    refreshToken = null;
  }
  return refreshToken;
}

async function saveRefreshToken(token) {
  refreshToken = token;
  await mkdir(dirname(TOKEN_FILE), { recursive: true });
  await writeFile(TOKEN_FILE, JSON.stringify({ refresh_token: token }, null, 2), 'utf8');
}

async function tokenRequest(params) {
  const res = await fetch('https://accounts.spotify.com/api/token', {
    method: 'POST',
    headers: {
      'Content-Type': 'application/x-www-form-urlencoded',
      Authorization: 'Basic ' + Buffer.from(`${CLIENT_ID}:${CLIENT_SECRET}`).toString('base64'),
    },
    body: new URLSearchParams(params).toString(),
  });
  if (!res.ok) throw new Error(`Spotify token request → ${res.status}: ${await res.text()}`);
  return res.json();
}

export async function getHostAccessToken() {
  if (accessToken && Date.now() < accessTokenExpiresAt) return accessToken;

  const rt = await loadRefreshToken();
  if (!rt) throw new Error('host not connected — visit /api/spotify/login first');

  const data = await tokenRequest({ grant_type: 'refresh_token', refresh_token: rt });
  accessToken = data.access_token;
  accessTokenExpiresAt = Date.now() + (data.expires_in - 60) * 1000;
  if (data.refresh_token) await saveRefreshToken(data.refresh_token);
  return accessToken;
}

export async function isHostConnected() {
  return Boolean(await loadRefreshToken());
}

export async function spotifyAsHost(path) {
  const token = await getHostAccessToken();
  const res = await fetch(`https://api.spotify.com/v1${path}`, {
    headers: { Authorization: `Bearer ${token}` },
  });
  if (res.status === 204) return null;
  if (!res.ok) throw new Error(`Spotify ${path} → ${res.status}`);
  return res.json();
}

router.get('/login', (req, res) => {
  const state = crypto.randomBytes(16).toString('hex');
  res.cookie('fh_host_auth_state', state, { httpOnly: true, maxAge: 5 * 60 * 1000 });
  const url = new URL('https://accounts.spotify.com/authorize');
  url.search = new URLSearchParams({
    response_type: 'code',
    client_id: CLIENT_ID,
    scope: SCOPES,
    redirect_uri: REDIRECT_URI,
    state,
  }).toString();
  res.redirect(url.toString());
});

router.get('/callback', async (req, res) => {
  const { code, state, error } = req.query;
  if (error) return res.status(400).send(`Spotify auth error: ${error}`);
  if (!state || state !== req.cookies?.fh_host_auth_state) {
    return res.status(400).send('State mismatch — try /api/spotify/login again');
  }
  try {
    const data = await tokenRequest({ grant_type: 'authorization_code', code, redirect_uri: REDIRECT_URI });
    await saveRefreshToken(data.refresh_token);
    accessToken = data.access_token;
    accessTokenExpiresAt = Date.now() + (data.expires_in - 60) * 1000;
    res.clearCookie('fh_host_auth_state');
    res.send('Host Spotify connected — you can close this tab and start a session.');
  } catch (e) {
    res.status(502).send(`Token exchange failed: ${e.message}`);
  }
});

router.get('/status', async (req, res) => {
  res.json({ connected: await isHostConnected() });
});

export default router;