/* Resi Cues — server entry.
 *
 * Follows one Resi decoder and works out how long until its next cue point, then
 * offers that two ways:
 *
 *   GET  /state         → snapshot for this module's tile
 *   GET  /stream        → SSE, `state` events on every change
 *   GET  /timers        → snapshot for the Timers module (guide: "Offering
 *   GET  /timers/stream → SSE, `timers` events        timers to the Timers module")
 *   GET  /decoders      → optionsRoute for the admin page's decoder picker
 *
 * Both the cue list and the playhead come from Resi's cloud rather than the
 * decoder: the decoder reports its position upstream and central.resi.io hands it
 * back. Nothing is installed at the decoder end, and nothing here talks to the
 * decoder directly.
 *
 * Why the playhead is estimated rather than repeated is explained in resi.js.
 */

'use strict';

const { createResiClient, createPlayhead, surroundingCues, positionToMs } = require('./resi');

const HEARTBEAT_MS = 15000;

function json(res, code, body) {
  const text = JSON.stringify(body);
  res.writeHead(code, { 'Content-Type': 'application/json; charset=utf-8' });
  res.end(text);
}

function sseHead(res) {
  res.writeHead(200, {
    'Content-Type': 'text/event-stream; charset=utf-8',
    'Cache-Control': 'no-cache, no-transform',
    Connection: 'keep-alive',
  });
  res.write('retry: 3000\n\n');
}

function writeAll(set, chunk) {
  for (const res of set) {
    try {
      res.write(chunk);
    } catch {
      set.delete(res);
    }
  }
}

/** What the tile and the Timers module see before anything has been configured. */
function emptyState(message) {
  return {
    status: 'error',
    message: message || 'Not configured',
    decoder: '',
    event: '',
    playing: false,
    estMs: null,
    estAt: Date.now(),
    cadenceMs: 0,
    next: null,
    prev: null,
    cues: [],
  };
}

function emptyTimers(now) {
  return { source: 'resi-cues', label: 'Resi', updatedAt: now, timers: [] };
}

let current = null; // the live handle, shared with routes()

module.exports = {
  init({ config, log }) {
    const username = String(config.username || '').trim();
    const password = String(config.password || '');
    const wanted = String(config.player || '').trim();
    const pollMs = Math.max(250, Number(config.pollSeconds || 1) * 1000);
    const cueRefreshMs = Math.max(1000, Number(config.cueRefreshSeconds || 5) * 1000);

    const stateStreams = new Set();
    const timerStreams = new Set();
    let state = emptyState(username && password ? 'Connecting' : 'Enter the Resi login in admin');
    let timer = null;
    let heartbeat = null;
    let stopped = false;

    const resi = createResiClient({ username, password });
    const head = createPlayhead({ trimMs: Number(config.positionTrimMs || 0) });

    let venueUuid = '';
    let hardwareId = '';
    let decoderName = '';
    let eventId = '';
    let profileId = '';
    let eventName = '';
    let cues = [];
    let lastCueLoad = 0;
    let inFlight = false;

    /* — what the two consumers see — */

    function publishState(next) {
      const before = JSON.stringify(state);
      state = next;
      if (JSON.stringify(state) === before) return;
      writeAll(stateStreams, `event: state\ndata: ${JSON.stringify(state)}\n\n`);
    }

    /**
     * The Timers module extrapolates from `startedAt` and its own clock, so this
     * only has to change when a timer changes *structurally* — a new cue, a pause,
     * a seek. Broadcasting every poll would make every dashboard repaint at 1 Hz
     * for nothing.
     */
    function timersSignature(snap) {
      return JSON.stringify(snap.timers.map(
        (t) => [t.id, t.label, t.state, t.startedAt, t.targetMs, t.status && t.status.text]));
    }

    let lastTimerSig = '';
    function publishTimers() {
      const snap = timersSnapshot(Date.now());
      const sig = timersSignature(snap);
      if (sig === lastTimerSig) return;
      lastTimerSig = sig;
      writeAll(timerStreams, `event: timers\ndata: ${JSON.stringify(snap)}\n\n`);
    }

    function timersSnapshot(now) {
      const timers = [];
      if (state.estMs !== null && state.estMs !== undefined) {
        const est = state.estMs + (state.playing ? now - state.estAt : 0);
        if (state.next) {
          const remainingMs = Math.max(0, state.next.ms - est);
          // The countdown "runs" from the cue before it, which is what gives the
          // consumer something to colour progress against.
          const from = state.prev ? state.prev.ms : 0;
          timers.push({
            id: 'next-cue',
            label: state.next.name || 'Next cue',
            kind: 'countdown',
            state: state.playing ? 'running' : 'paused',
            startedAt: now - Math.max(0, est - from),
            elapsedMs: null,
            remainingMs,
            targetMs: Math.max(1000, state.next.ms - from),
            // The label already is the cue's name, and it is what the card is titled
            // with; repeating it on the status line only crowded the card.
            status: { text: state.playing ? 'Next cue' : 'Held', tone: state.playing ? 'ok' : 'warn' },
            detail: state.event || '',
          });
        }
        timers.push({
          id: 'playhead',
          label: 'Playhead',
          kind: 'elapsed',
          state: state.playing ? 'running' : 'paused',
          startedAt: now - Math.max(0, est),
          elapsedMs: Math.max(0, est),
          remainingMs: null,
          targetMs: null,
          status: { text: state.decoder || '', tone: state.playing ? 'ok' : 'muted' },
          detail: state.prev ? `After ${state.prev.name}` : '',
        });
      }
      return { source: 'resi-cues', label: 'Resi', updatedAt: now, timers };
    }

    /* — finding the decoder — */

    async function locate() {
      const venues = await resi.venues();
      for (const v of venues) {
        const players = await resi.players(v.uuid);
        for (const p of players) {
          if (wanted ? p.playerHardwareId === wanted : true) {
            venueUuid = v.uuid;
            hardwareId = p.playerHardwareId;
            decoderName = `${v.userName || v.name || 'Venue'} — ${p.userName || hardwareId}`;
            return true;
          }
        }
      }
      return false;
    }

    /* — the loop — */

    async function tick() {
      if (inFlight || stopped) return;
      inFlight = true;
      try {
        if (!hardwareId && !(await locate())) {
          publishState(emptyState(wanted ? 'That decoder is not on this account' : 'No decoders found'));
          return;
        }

        const players = await resi.players(venueUuid);
        const me = players.find((p) => p.playerHardwareId === hardwareId);
        if (!me) {
          publishState({ ...emptyState('Decoder not listed'), decoder: decoderName });
          return;
        }

        head.note(positionToMs(me.position));

        if (me.eventId && me.eventId !== eventId) {
          eventId = me.eventId;
          const ev = (await resi.event(eventId)) || {};
          profileId = ev.eventProfileId || '';
          eventName = ev.name || '';
          cues = profileId ? await resi.cues(profileId, eventId) : [];
          lastCueLoad = Date.now();
          log(`event ${eventName || eventId} — ${cues.length} cue(s)`);
        } else if (!me.eventId) {
          eventId = '';
          profileId = '';
          eventName = '';
          cues = [];
        }

        const seeked = head.takeSeek();
        if (profileId && eventId && (seeked || Date.now() - lastCueLoad >= cueRefreshMs)) {
          lastCueLoad = Date.now();
          const fresh = await resi.cues(profileId, eventId);
          if (JSON.stringify(fresh) !== JSON.stringify(cues)) {
            log(`cue list changed — ${fresh.length} cue(s)`);
            cues = fresh;
          }
        }

        const { estMs, playing, cadenceMs } = head.read();
        const { prev, next } = surroundingCues(cues, estMs === null ? -1 : estMs);
        publishState({
          status: 'ok',
          message: '',
          decoder: decoderName,
          event: eventName,
          playing,
          estMs,
          estAt: Date.now(),
          cadenceMs,
          next,
          prev,
          cues,
        });
      } catch (err) {
        const message = (err && err.message) || String(err);
        log(`poll failed: ${message}`);
        publishState({ ...state, status: 'error', message });
      } finally {
        inFlight = false;
        publishTimers();
      }
    }

    if (username && password) {
      timer = setInterval(() => { void tick(); }, pollMs);
      void tick();
    } else {
      log('no Resi login configured — idle');
    }
    heartbeat = setInterval(() => {
      writeAll(stateStreams, ': ping\n\n');
      writeAll(timerStreams, ': ping\n\n');
    }, HEARTBEAT_MS);

    current = {
      get state() { return state; },
      timersSnapshot,
      stateStreams,
      timerStreams,
      resi,
      configured: Boolean(username && password),
      stop() {
        stopped = true;
        if (timer) clearInterval(timer);
        if (heartbeat) clearInterval(heartbeat);
        for (const res of [...stateStreams, ...timerStreams]) {
          try { res.end(); } catch { /* already gone */ }
        }
        stateStreams.clear();
        timerStreams.clear();
        if (current && current.stop === this.stop) current = null;
      },
      health() {
        if (!username || !password) return { status: 'error', message: 'Enter the Resi login in admin' };
        if (state.status === 'ok') {
          return { status: 'ok', message: state.playing ? `Playing — ${state.decoder}` : `Paused — ${state.decoder}` };
        }
        if (state.status === 'error') return { status: 'error', message: state.message };
        return { status: 'connecting', message: state.message };
      },
    };
    return current;
  },

  routes({ config, log }) {
    return {
      'GET /state': (req, res) => {
        json(res, 200, current ? current.state : emptyState('Module restarting'));
      },

      'GET /stream': (req, res) => {
        sseHead(res);
        const snap = current ? current.state : emptyState('Module restarting');
        res.write(`event: state\ndata: ${JSON.stringify(snap)}\n\n`);
        if (!current) return res.end();
        current.stateStreams.add(res);
        req.on('close', () => current && current.stateStreams.delete(res));
      },

      'GET /timers': (req, res) => {
        const now = Date.now();
        json(res, 200, current ? current.timersSnapshot(now) : emptyTimers(now));
      },

      'GET /timers/stream': (req, res) => {
        sseHead(res);
        const now = Date.now();
        const snap = current ? current.timersSnapshot(now) : emptyTimers(now);
        res.write(`event: timers\ndata: ${JSON.stringify(snap)}\n\n`);
        if (!current) return res.end();
        current.timerStreams.add(res);
        req.on('close', () => current && current.timerStreams.delete(res));
      },

      // The admin page's decoder picker. A live call, because it is how the decoder
      // gets chosen in the first place — there is nothing cached to answer from.
      'GET /decoders': async (req, res) => {
        if (!config.username || !config.password) {
          return json(res, 200, { options: [], note: 'Enter the Resi login first' });
        }
        try {
          const client = createResiClient({
            username: String(config.username), password: String(config.password),
          });
          const options = [];
          for (const v of await client.venues()) {
            for (const p of await client.players(v.uuid)) {
              options.push({
                value: p.playerHardwareId,
                label: `${p.userName || p.playerHardwareId}`,
                group: v.userName || v.name || 'Venue',
              });
            }
          }
          json(res, 200, { options });
        } catch (err) {
          log(`decoder list failed: ${(err && err.message) || err}`);
          json(res, 502, { options: [], error: (err && err.message) || String(err) });
        }
      },
    };
  },
};