'use strict';

/**
 * Vista Cues — server part.
 *
 * Vista 3 cannot say what it is playing: its OSC is input-only and it sends
 * no feedback. What it *does* have is a network MIDI session that
 * ProPresenter and the tracks rig fire cue lists through. A session sends
 * every message to every participant, so this module joins those sessions
 * as one more participant (rtpmidi.js) and hears exactly what Vista hears.
 * The admin's "Cue lists" sheet (mapping.js) turns each note into
 * "Go on Walk-in", "Release Worship 1"…, and from those the module keeps
 * which lists are live.
 *
 *   GET  /state   → { state }                     (instant paint)
 *   GET  /stream  → SSE: `state` on every change
 *   POST /clear   → forget which lists are live (when Vista was reset by hand)
 *
 * What the tile shows is what Vista was told, not what Vista confirmed: if
 * Vista is closed or someone works the desk by hand, the two can differ.
 */

const fs = require('fs');
const { spawn } = require('child_process');
const { Session } = require('./rtpmidi');
const { parseMapping, match, triggerLabel } = require('./mapping');

const HEARTBEAT_MS = 15000;
const LOG_MAX = 40;
const DNS_SD = '/usr/bin/dns-sd';

let current = null;

function emptyState(extra = {}) {
  return {
    listening: false,
    error: '',
    sessionName: '',
    port: null,
    advertised: false,
    sources: [],
    current: null,
    active: [],
    log: [],
    mappingErrors: [],
    rules: 0,
    now: Date.now(),
    ...extra,
  };
}

function endpointOf(v) {
  const ep = v && typeof v === 'object' ? v : {};
  return { host: String(ep.host || '').trim(), port: Number(ep.port) || 5004 };
}

module.exports = {
  init({ config, log }) {
    const sessionName = String(config.sessionName || '').trim() || 'ProdDash Lighting';
    const port = Math.round(Number(config.sessionPort)) || 5040;
    const middleC = config.middleC === 'C4' ? 'C4' : 'C3';
    const exclusive = config.exclusive === true;
    const headTakesOver = config.headTakesOver !== false;
    const { rules, errors: mappingErrors, groups } = parseMapping(config.cueLists, { middleC });
    if (mappingErrors.length) {
      for (const e of mappingErrors) log(`cue lists line ${e.line} skipped (${e.why}): ${e.text}`);
    }

    const senders = [
      { label: String(config.source1Name || '').trim() || 'ProPresenter', ...endpointOf(config.source1) },
      { label: String(config.source2Name || '').trim() || 'Tracks', ...endpointOf(config.source2) },
      { label: String(config.source3Name || '').trim() || 'Companion', ...endpointOf(config.source3) },
    ].filter((s) => s.host);

    const streams = new Set();
    const lists = new Map();   // lower-cased name → { name, group, state, firedAt, lastAt, lastAction, source, trigger, goes }
    const history = [];        // newest first
    let currentKey = '';
    let lastFrame = '';
    let advertiser = null;
    let advertised = false;
    let stopped = false;

    if (port < 1024 || port > 65534) throw new Error('Session port must be between 1024 and 65534');

    const session = new Session({ name: sessionName, port, log });
    const invites = senders.map((s) => ({ ...s, inv: null }));

    /* ── what Vista was told ─────────────────────────────────────── */

    function sourceLabel(p) {
      return p.label || p.name || p.address;
    }

    function record(entry) {
      history.unshift({ at: Date.now(), ...entry });
      if (history.length > LOG_MAX) history.length = LOG_MAX;
    }

    function apply(rule, source, trigger) {
      const now = Date.now();
      const key = rule.list.toLowerCase();
      record({ action: rule.action, list: rule.list, group: rule.group, source, trigger, mapped: true });
      if (rule.action === 'flash') return; // a momentary hit: in the log, never live
      if (rule.action === 'releaseAll') {
        lists.clear();
        currentKey = '';
        return;
      }
      if (rule.action === 'release') {
        lists.delete(key);
        if (currentKey === key) currentKey = newestKey();
        return;
      }
      let l = lists.get(key);
      if (rule.action === 'go') {
        // A Go replaces the other lists of its group. A Go in the first group (the
        // main scene) takes over everything, as Vista's last-takes-precedence does;
        // and with "Go releases others" on, every Go does.
        const takeover = exclusive || (headTakesOver && rule.group && rule.group === groups[0]);
        for (const [k, other] of [...lists]) {
          if (k !== key && (takeover || (rule.group && other.group === rule.group))) lists.delete(k);
        }
        if (!l) {
          l = { name: rule.list, group: rule.group, state: 'active', firedAt: now, goes: 0 };
          lists.set(key, l);
        }
        l.state = 'active';
        l.goes++;
        l.lastAt = now;
        l.lastAction = 'go';
        l.source = source;
        l.trigger = trigger;
        currentKey = key;
        return;
      }
      // pause / back act on a list that is live; on one that isn't, they only go in the log.
      if (!l) return;
      l.lastAt = now;
      l.lastAction = rule.action;
      l.source = source;
      l.trigger = trigger;
      if (rule.action === 'pause') l.state = 'paused'; // the next Go resumes it
      if (rule.action === 'back') { l.state = 'active'; l.goes = Math.max(1, l.goes - 1); }
    }

    function newestKey() {
      let best = '';
      let at = -1;
      for (const [k, l] of lists) if (l.lastAt > at) { best = k; at = l.lastAt; }
      return best;
    }

    session.on('midi', ({ participant, event }) => {
      if (event.type !== 'noteon' && event.type !== 'program') return;
      const source = sourceLabel(participant);
      const trigger = triggerLabel(event, middleC);
      const rule = match(rules, event);
      if (rule) {
        apply(rule, source, trigger);
        log(`${source}: ${trigger} → ${rule.action}${rule.list ? ` ${rule.list}` : ''}`);
      } else {
        record({ action: '', list: '', source, trigger, mapped: false });
      }
      broadcast();
    });
    session.on('change', () => broadcast());
    // Senders are joined once our ports are ours — straight away normally,
    // or a moment later when a busy port frees up.
    session.on('listening', () => {
      if (stopped) return;
      log(`session "${sessionName}" listening on UDP ${port}/${port + 1}`);
      for (const s of invites) s.inv = session.invite(s.host, s.port, s.label);
      if (!advertiser) advertise();
    });

    /* ── the view-model ──────────────────────────────────────────── */

    function sources() {
      const out = [];
      const seen = new Set();
      for (const s of invites) {
        const inv = s.inv;
        const p = inv && [...session.participants.values()].find((q) => q.connected && q.address === inv.address && q.controlPort === inv.port);
        if (p) seen.add(p.key);
        out.push({
          label: s.label,
          name: p ? p.name : '',
          address: inv?.address || s.host,
          configured: true,
          connected: Boolean(p),
          error: p ? '' : (inv?.error || ''),
          lastHeard: p ? p.lastHeard : null,
        });
      }
      for (const p of session.participants.values()) {
        if (seen.has(p.key) || !p.connected) continue;
        out.push({ label: p.label || p.name, name: p.name, address: p.address, configured: false, connected: true, error: '', lastHeard: p.lastHeard });
      }
      return out;
    }

    function groupRank(l) {
      const i = groups.indexOf(l.group);
      return i < 0 ? groups.length : i;
    }

    function buildState() {
      const live = [...lists.values()].sort((a, b) => b.lastAt - a.lastAt);
      // The headline: the live list of the sheet's first group (the scene, say,
      // rather than whichever colour changed last); without groups, the last Go.
      const head = groups[0];
      const cur = (head && live.find((l) => l.group === head))
        || (currentKey ? lists.get(currentKey) : null)
        || null;
      return {
        listening: Boolean(session.control),
        error: session.error,
        sessionName,
        port,
        advertised,
        sources: sources(),
        current: cur || null,
        // The rest in sheet order of their group, so a colour chip stays put as it changes.
        active: live.filter((l) => l !== cur).sort((a, b) => groupRank(a) - groupRank(b) || b.lastAt - a.lastAt),
        headline: head || '',
        log: history,
        mappingErrors,
        rules: rules.length,
        now: Date.now(),
      };
    }

    function send(payload) {
      for (const res of streams) {
        try { res.write(payload); } catch { streams.delete(res); }
      }
    }

    function broadcast() {
      if (stopped) return;
      const state = buildState();
      const { now, sources: src, ...rest } = state;
      // lastHeard moves with every packet; leave it out of change detection.
      const frame = JSON.stringify({ ...rest, src: src.map(({ lastHeard, ...s }) => s) });
      if (frame === lastFrame) return;
      lastFrame = frame;
      send(`event: state\ndata: ${JSON.stringify(state)}\n\n`);
    }

    const keepalive = setInterval(() => send(': ping\n\n'), HEARTBEAT_MS);
    keepalive.unref?.();

    /* ── being found: Bonjour on macOS ───────────────────────────── */

    // Advertising _apple-midi._udp puts us in Audio MIDI Setup's Directory on
    // every Mac here, so a sender can add us with a click. macOS ships the
    // dns-sd tool; we run it as a child and stop it with the module. Elsewhere
    // nothing is advertised and senders are joined by address alone.
    function advertise() {
      if (stopped || config.advertise === false || process.platform !== 'darwin' || !fs.existsSync(DNS_SD)) return;
      advertiser = spawn(DNS_SD, ['-R', sessionName, '_apple-midi._udp', 'local', String(port)], { stdio: ['ignore', 'pipe', 'pipe'] });
      advertiser.stdout.on('data', (d) => {
        if (/Name now registered and active/i.test(String(d)) && !advertised) {
          advertised = true;
          log(`advertised as "${sessionName}" on port ${port}`);
          broadcast();
        }
      });
      advertiser.stderr.on('data', () => {});
      advertiser.on('error', (e) => { log(`dns-sd: ${e.message}`); advertiser = null; });
      advertiser.on('exit', () => {
        advertiser = null;
        advertised = false;
        if (!stopped) setTimeout(advertise, 5000).unref?.();
      });
    }

    /* ── start ───────────────────────────────────────────────────── */

    session.start().then(() => broadcast());

    current = {
      streams,
      getState: buildState,
      clear() {
        lists.clear();
        currentKey = '';
        record({ action: 'cleared', list: '', source: 'Dashboard', trigger: '', mapped: true });
        broadcast();
      },
    };

    return {
      stop() {
        stopped = true;
        clearInterval(keepalive);
        session.stop();
        if (advertiser) { try { advertiser.kill(); } catch { /* gone */ } advertiser = null; }
        for (const res of streams) { try { res.end(); } catch { /* gone */ } }
        streams.clear();
        if (current && current.streams === streams) current = null;
      },
      health() {
        if (session.error) return { status: 'error', message: session.error };
        const src = sources();
        const on = src.filter((s) => s.connected);
        const lines = mappingErrors.length ? ` · ${mappingErrors.length} cue-list line${mappingErrors.length === 1 ? '' : 's'} not understood (first: line ${mappingErrors[0].line})` : '';
        const map = rules.length ? '' : ' · no cue lists mapped yet';
        if (on.length) {
          const off = src.filter((s) => !s.connected).map((s) => `${s.label} (${s.error || 'joining…'})`);
          return {
            status: off.length ? 'connecting' : 'ok',
            message: `In session with ${on.map((s) => s.label).join(', ')}${off.length ? ` · waiting for ${off.join(', ')}` : ''}${map}${lines}`,
          };
        }
        const where = advertised ? `advertised as "${sessionName}"` : `port ${port}`;
        if (src.length) {
          return { status: 'connecting', message: `Joining ${src.map((s) => `${s.label}${s.error ? ` (${s.error})` : ''}`).join(', ')} · ${where}${map}${lines}` };
        }
        return { status: 'connecting', message: `Waiting for a MIDI session to connect · ${where}${map}${lines}` };
      },
    };
  },

  routes() {
    const sendJson = (res, code, body) => {
      res.writeHead(code, { 'Content-Type': 'application/json; charset=utf-8', 'Cache-Control': 'no-store' });
      res.end(JSON.stringify(body));
    };
    return {
      'GET /state': (req, res) => sendJson(res, 200, { state: current ? current.getState() : emptyState() }),
      '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');
        res.write(`event: state\ndata: ${JSON.stringify(current ? current.getState() : emptyState())}\n\n`);
        if (!current) return void res.end();
        try { req.socket.setKeepAlive(true, 15000); } catch { /* gone */ }
        const set = current.streams;
        set.add(res);
        req.on('close', () => set.delete(res));
      },
      'POST /clear': (req, res) => {
        if (!current) return sendJson(res, 503, { error: 'Vista Cues is not running' });
        current.clear();
        return sendJson(res, 200, { ok: true });
      },
    };
  },
};