// Live session state — deliberately in-memory, deliberately polled by
// clients rather than pushed over a socket. A session is one game night;
// nothing here needs to survive a restart or scale past one process.
// Same "boring beats clever" precedent as keep's `watch` command and
// wisp's TTL sweep elsewhere in this family.
import { Router } from 'express';
import crypto from 'crypto';
import { spotifyAsHost } from './hostAuth.js';

const router = Router();

/** @type {Map<string, Session>} */
const sessions = new Map();

// code -> interval handle, for the now-playing auto-call poller
const autoCallTimers = new Map();

function makeCode() {
  // Short, spoken-aloud-friendly: no 0/O/1/I ambiguity.
  const alphabet = 'ABCDEFGHJKLMNPQRSTUVWXYZ23456789';
  let code;
  do {
    code = Array.from({ length: 5 }, () => alphabet[crypto.randomInt(alphabet.length)]).join('');
  } while (sessions.has(code));
  return code;
}

function summarizeTrack(entry) {
  const t = entry.item;
  if (!t) return null;
  return {
    id: t.id,
    title: t.name,
    artist: t.artists?.[0]?.name ?? 'Unknown artist',
    album: t.album?.name ?? '',
    image: t.album?.images?.[0]?.url ?? null,
    uri: t.uri,
  };
}

async function fetchPlaylistTracks(playlistId) {
  const out = [];
  let url = `/playlists/${playlistId}/items?limit=100&fields=next,items(item(id,name,uri,artists(name),album(name,images)))`;
  while (url) {
    const page = await spotifyAsHost(url);
    out.push(...(page.items ?? []));
    url = page.next ? page.next.replace('https://api.spotify.com/v1', '') : null;
  }
  return out.map(summarizeTrack).filter(Boolean);
}

// POST /api/session — body: { playlistId, playlistName }
router.post('/', async (req, res) => {
  const { playlistId, playlistName } = req.body ?? {};
  if (!playlistId) return res.status(400).json({ error: 'playlistId required' });
  try {
    const tracks = await fetchPlaylistTracks(playlistId);
    if (tracks.length < 12) {
      return res.status(400).json({ error: `playlist has only ${tracks.length} usable tracks — need at least 12 for a 3x3 card with headroom` });
    }
    const code = makeCode();
    sessions.set(code, {
      code,
      playlistName: playlistName || 'Untitled session',
      tracks,
      calledIds: [],
      autoCall: false,
      createdAt: Date.now(),
    });
    res.json({ code, playlistName, trackCount: tracks.length });
  } catch (e) {
    res.status(502).json({ error: e.message });
  }
});

function requireSession(req, res, next) {
  const session = sessions.get(String(req.params.code || '').toUpperCase());
  if (!session) return res.status(404).json({ error: 'session not found — check the code' });
  req.session = session;
  next();
}

// GET /api/session/:code — join payload: full pool (for client-side card
// generation) + what's been called so far.
router.get('/:code', requireSession, (req, res) => {
  const { code, playlistName, tracks, calledIds, autoCall } = req.session;
  res.json({ code, playlistName, tracks, calledIds, autoCall });
});

// GET /api/session/:code/state — cheap polling target, no full pool.
router.get('/:code/state', requireSession, (req, res) => {
  const { calledIds, autoCall } = req.session;
  res.json({ calledIds, autoCall });
});

// POST /api/session/:code/call — body: { trackId } — manual call.
router.post('/:code/call', requireSession, (req, res) => {
  const { trackId } = req.body ?? {};
  const track = req.session.tracks.find(t => t.id === trackId);
  if (!track) return res.status(400).json({ error: 'trackId not in this session pool' });
  if (!req.session.calledIds.includes(trackId)) req.session.calledIds.push(trackId);
  res.json({ calledIds: req.session.calledIds });
});

// POST /api/session/:code/call-random — classic caller draw, no replacement.
router.post('/:code/call-random', requireSession, (req, res) => {
  const remaining = req.session.tracks.filter(t => !req.session.calledIds.includes(t.id));
  if (!remaining.length) return res.status(409).json({ error: 'every track has already been called' });
  const pick = remaining[crypto.randomInt(remaining.length)];
  req.session.calledIds.push(pick.id);
  res.json({ called: pick, calledIds: req.session.calledIds });
});

// POST /api/session/:code/autocall/start — polls the host's actual
// Spotify playback and auto-calls whatever's currently playing, if it's
// in this session's pool. Manual /call and /call-random keep working
// alongside it — this is a bonus layer, not a replacement.
router.post('/:code/autocall/start', requireSession, (req, res) => {
  const { code } = req.session;
  if (autoCallTimers.has(code)) return res.json({ ok: true, already: true });

  let lastSeenTrackId = null;
  const timer = setInterval(async () => {
    const session = sessions.get(code);
    if (!session) { clearInterval(timer); autoCallTimers.delete(code); return; }
    try {
      const playing = await spotifyAsHost('/me/player/currently-playing');
      const trackId = playing?.item?.id;
      if (!trackId || trackId === lastSeenTrackId) return;
      lastSeenTrackId = trackId;
      if (session.tracks.some(t => t.id === trackId) && !session.calledIds.includes(trackId)) {
        session.calledIds.push(trackId);
      }
    } catch {
      // host playback unavailable this tick — try again next tick, not fatal
    }
  }, 5000);

  autoCallTimers.set(code, timer);
  req.session.autoCall = true;
  res.json({ ok: true });
});

router.post('/:code/autocall/stop', requireSession, (req, res) => {
  const { code } = req.session;
  const timer = autoCallTimers.get(code);
  if (timer) { clearInterval(timer); autoCallTimers.delete(code); }
  req.session.autoCall = false;
  res.json({ ok: true });
});

// Sessions are ephemeral by design — sweep anything older than 12h so a
// forgotten session doesn't sit in memory forever. Deliberately dumb
// interval, same precedent as the rest of this family.
setInterval(() => {
  const cutoff = Date.now() - 12 * 60 * 60 * 1000;
  for (const [code, session] of sessions) {
    if (session.createdAt < cutoff) {
      const timer = autoCallTimers.get(code);
      if (timer) { clearInterval(timer); autoCallTimers.delete(code); }
      sessions.delete(code);
    }
  }
}, 60 * 60 * 1000);

export default router;