'use strict';

/**
 * ProPresenter Now / Next — server part.
 *
 * Owns the one ProPresenter connection (via propresenter-core, copied here
 * unchanged — it holds every ProPresenter 7/20 quirk) and fans the live
 * view-model out to every tile over SSE. Browsers never talk to
 * ProPresenter directly.
 *
 *   GET /state   → { state: <view-model> }   (instant paint for new tiles)
 *   GET /stream  → SSE, `state` events       (change-detected, heartbeated)
 *
 * The view-model carries `look`: the live audience look as
 * { name, modified }, or null while it is unknown. A small poller of this
 * file's own reads it (GET /v1/look/current, with /v1/looks to name it) from
 * the same ProPresenter the core follows. Its failures only null `look`; they
 * never touch the core's reachable / lastError.
 */

const { createProPresenterClient, clearedViewModel } = require('./propresenter-core');

/** SSE comment ping cadence — keeps idle connections alive through sleepy Wi-Fi. */
const HEARTBEAT_MS = 15000;

const LOOK_POLL_MS = 1000; // the look matters the moment it changes
const LOOK_RETRY_MS = 3000; // while the look cannot be read
const LOOKS_EVERY = 10; // re-read the saved looks every N polls
const LOOK_TIMEOUT_MS = 2500;
const LOOK_FAILS_BEFORE_NULL = 3; // consecutive failed reads before the look is called unknown

/** One look's name, trimmed — ProPresenter leaves the current look's name blank on some versions. */
function lookName(entry) {
  return String(entry?.id?.name ?? entry?.name ?? '').trim();
}

/** Set by init(), read by the routes — both are rebuilt together on remount. */
let current = null;

module.exports = {
  init({ config, log }) {
    const streams = new Set();
    // Endpoint config. Legacy flat host/port keys (saved before the endpoint
    // field existed) can only still be present until the admin form is
    // re-saved, so when they exist they win over the endpoint's default.
    const ep = config.propresenter && typeof config.propresenter === 'object' ? config.propresenter : {};
    const host = String(config.host ?? ep.host ?? '');
    const port = Number(config.port ?? ep.port) || 1025;
    const enabled = Boolean(host && port);
    let latest = clearedViewModel();
    let look = null; // { name, modified } or null while unknown
    let lastFrame = '';

    /** The core's view-model plus the live look — what every tile and GET /state sees. */
    const snapshot = () => ({ ...latest, look });

    function broadcast() {
      if (!streams.size) return;
      let frame;
      try {
        frame = JSON.stringify(snapshot());
      } catch {
        return;
      }
      // The poll loop emits every tick whether anything changed or not.
      // Broadcasting only real changes keeps idle tiles genuinely idle.
      if (frame === lastFrame) return;
      lastFrame = frame;
      const payload = `event: state\ndata: ${frame}\n\n`;
      for (const res of streams) {
        try {
          res.write(payload);
        } catch {
          streams.delete(res);
        }
      }
    }

    const client = createProPresenterClient({
      onData(view) {
        latest = view;
        broadcast();
      },
    });

    client.configure({
      enabled,
      host,
      port,
      password: String(config.password || ''),
    });

    /* ── audience look ──────────────────────────────────────────────
       Same reads and rules as the ProPresenter Look module. ProPresenter
       sometimes leaves the live look's name blank, so the saved list is
       consulted: the look's `index` points at the saved look it matches, or
       is past the end when someone has changed it by hand. */

    const password = String(config.password || '');
    let saved = []; // names of the saved looks, in ProPresenter's order
    let savedOk = false; // the list exists and is in `saved`
    let savedTried = false; // /v1/looks has answered (a 404 counts: do not ask again every poll)
    let lookTick = 0;
    let lookFails = 0; // consecutive failed reads of the look
    let lookStopped = false;
    let lookTimer = null;

    function lookUrl(target) {
      const built = new URL(`http://${host}:${port}${target}`);
      if (password) built.searchParams.set('password', password);
      return built;
    }

    async function lookJson(target) {
      const response = await fetch(lookUrl(target), {
        headers: { Accept: 'application/json' },
        signal: AbortSignal.timeout(LOOK_TIMEOUT_MS),
      });
      if (!response.ok) {
        const err = new Error(`ProPresenter ${response.status} ${response.statusText}`);
        err.status = response.status;
        throw err;
      }
      const text = await response.text();
      return text ? JSON.parse(text) : null;
    }

    async function refreshSaved() {
      try {
        const list = await lookJson('/v1/looks');
        // A real empty array is a valid (empty) list. Anything else that
        // answered 200 is not a list, so it names nothing — an empty list
        // would call every look modified.
        saved = Array.isArray(list) ? list.map(lookName) : [];
        savedOk = Array.isArray(list);
        savedTried = true;
      } catch (err) {
        // An older ProPresenter without the list still answers look/current;
        // the live look's own name is shown then. Remembered, so the list is
        // asked for again only on the normal cadence, not on every poll.
        if (err.status !== 404) throw err;
        saved = [];
        savedOk = false;
        savedTried = true;
      }
    }

    /** { name, modified }, or null when there is no name to show (the pill then says "Live"). */
    function resolveLook(live) {
      const index = Number(live?.id?.index);
      const own = lookName(live);
      if (savedOk && Number.isInteger(index) && index >= 0 && index < saved.length) {
        return { name: saved[index] || own || `Look ${index + 1}`, modified: false };
      }
      // Changed by hand, matching no saved look.
      if (savedOk && Number.isInteger(index) && index >= saved.length) {
        return { name: own || 'Custom look', modified: true };
      }
      // No saved list to name it from: the live look's own name, or nothing.
      return own ? { name: own, modified: false } : null;
    }

    function setLook(next) {
      if (JSON.stringify(next) === JSON.stringify(look)) return;
      look = next;
      broadcast();
    }

    async function pollLook() {
      if (lookStopped) return;
      let next = null;
      let readOk = false;
      try {
        lookTick += 1;
        if (lookTick % LOOKS_EVERY === 1 || !savedTried) await refreshSaved();
        const live = await lookJson('/v1/look/current');
        if (!live || typeof live !== 'object') throw new Error('no look in the answer');
        next = resolveLook(live);
        // A look saved since our last read: refresh the list now rather than
        // calling it "Custom" for up to ten seconds.
        if (next?.modified && !look?.modified && lookTick % LOOKS_EVERY !== 1) {
          await refreshSaved();
          next = resolveLook(live);
        }
        readOk = true;
      } catch {
        // A list that exists may have changed while ProPresenter was away:
        // re-read it first when it comes back. One that is known not to exist
        // (404) is not asked for again on every failed retry.
        if (savedOk) lookTick = 0;
      }
      if (lookStopped) return;
      if (readOk) {
        lookFails = 0;
        setLook(next);
      } else {
        // One slow or dropped read must not blank the pill: the last good look
        // stands until the reads have failed several times running. A real
        // outage shows as "Reconnecting…" through the core, not as this name.
        lookFails += 1;
        if (lookFails >= LOOK_FAILS_BEFORE_NULL) setLook(null);
      }
      lookTimer = setTimeout(pollLook, readOk ? LOOK_POLL_MS : LOOK_RETRY_MS);
    }

    if (enabled) {
      client.start();
      pollLook();
      log(`following ProPresenter at ${host}:${port}`);
    } else {
      log('no ProPresenter host configured — set one in /admin');
    }

    const heartbeat = setInterval(() => {
      for (const res of streams) {
        try {
          res.write(': ping\n\n');
        } catch {
          streams.delete(res);
        }
      }
    }, HEARTBEAT_MS);
    heartbeat.unref?.();

    current = { streams, getLatest: snapshot };

    return {
      stop() {
        lookStopped = true;
        clearTimeout(lookTimer);
        clearInterval(heartbeat);
        client.stop();
        for (const res of streams) {
          try { res.end(); } catch { /* already gone */ }
        }
        streams.clear();
        if (current && current.streams === streams) current = null;
      },
      health() {
        if (!enabled) return { status: 'error', message: 'No ProPresenter host configured' };
        if (latest.reachable) return { status: 'ok', message: `Following ${host}:${port}` };
        return {
          status: 'error',
          message: latest.lastError
            ? `ProPresenter unreachable: ${latest.lastError}`
            : 'Trying to reach ProPresenter…',
        };
      },
    };
  },

  /**
   * Two ways to place this module. "Now / Next" is the full card — what is
   * live, then the rest of the playlist. "Now" is the same live item alone,
   * edge to edge with the gradient filling the tile: a wall display that says
   * one thing. The Now entry offers only the settings it can act on, so its
   * gear carries no Next switches.
   */
  tiles() {
    return [
      {
        id: 'full',
        name: 'Now / Next',
        description: 'What is live, and the rest of the playlist',
        defaultSize: { w: 4, h: 5 },
        minSize: { w: 3, h: 3 },
        settings: { view: 'full' },
      },
      {
        id: 'now',
        name: 'Now',
        description: 'Only what is live, filling the tile',
        defaultSize: { w: 4, h: 2 },
        minSize: { w: 2, h: 1 },
        settings: { view: 'now' },
        instanceSchema: {
          cleanTitles: { type: 'switch', label: 'Tidy titles', default: true },
          showPlaylist: { type: 'switch', label: 'Playlist', default: true, group: 'Show' },
          showLive: { type: 'switch', label: 'Audience look', default: true, group: 'Show' },
          showNowLabel: { type: 'switch', label: 'Now label', default: true, group: 'Show' },
          showSlideCount: { type: 'switch', label: 'Slide count', default: true, group: 'Show' },
          showProgress: { type: 'switch', label: 'Progress bar', default: true, group: 'Show' },
        },
        instanceGroups: { Show: { collapsed: true, columns: 2 } },
      },
    ];
  },

  routes() {
    return {
      'GET /state': (req, res) => {
        res.writeHead(200, { 'Content-Type': 'application/json; charset=utf-8', 'Cache-Control': 'no-store' });
        res.end(JSON.stringify({ state: current ? current.getLatest() : { ...clearedViewModel(), look: null } }));
      },

      'GET /stream': (req, res) => {
        res.writeHead(200, {
          'Content-Type': 'text/event-stream; charset=utf-8',
          'Cache-Control': 'no-cache, no-transform',
          Connection: 'keep-alive',
          'X-Accel-Buffering': 'no',
        });
        res.write('retry: 3000\n\n');
        const view = current ? current.getLatest() : { ...clearedViewModel(), look: null };
        res.write(`event: state\ndata: ${JSON.stringify(view)}\n\n`);
        if (!current) return void res.end();
        const { streams } = current;
        // A viewer that stops reading (locked tablet, sleeping laptop) must
        // not queue frames forever; keepalive probes make the OS notice.
        try { req.socket.setKeepAlive(true, 15000); } catch { /* gone */ }
        streams.add(res);
        req.on('close', () => streams.delete(res));
      },
    };
  },
};