// A read-only connection to a Bambu Lab printer on your network.
//
// The printer runs an MQTT broker on port 8883 — TLS with a self-signed
// certificate, username "bblp", and the access code from its screen as the
// password. Printhive only subscribes to the printer's reports and asks once for
// a full one ("pushall"); it never sends anything that changes what the printer
// is doing.
const mqtt = require('mqtt');

const PORT = 8883;

// An id the printer sends as all zeros means no RFID tag was read.
const realId = (v) => (v && !/^0+$/.test(String(v)) ? String(v) : null);

// One tray, as the printer describes it. `remain` is a percentage; the printer
// sends -1 when it can't tell. An AMS lite only knows full or empty, so its
// figure isn't a measurement — callers decide whether to trust it.
function describeTray(tray, unit = null) {
  const loaded = Boolean(tray && tray.tray_type);
  return {
    unit,
    slot: tray && tray.id != null ? Number(tray.id) : null,
    empty: !loaded,
    material: loaded ? tray.tray_type : null,
    colour: loaded && tray.tray_color ? `#${String(tray.tray_color).slice(0, 6).toUpperCase()}` : null,
    profile: loaded ? tray.tray_info_idx || null : null, // Bambu's filament profile, e.g. GFA00
    brand: loaded ? tray.tray_sub_brands || null : null,
    remain: loaded && Number(tray.remain) >= 0 ? Number(tray.remain) : null,
    // A Bambu spool's RFID tag: tray_uuid names the spool, tag_uid the tag.
    uuid: loaded ? realId(tray.tray_uuid) : null,
    tagUid: loaded ? realId(tray.tag_uid) : null,
    idName: loaded ? tray.tray_id_name || null : null, // e.g. "A00-W1", on firmware that sends it
  };
}

// Every tray in every AMS unit, in order.
function describeAms(units) {
  const trays = [];
  for (const unit of Array.isArray(units) ? units : []) {
    for (const tray of unit.tray || []) trays.push(describeTray(tray, Number(unit.id)));
  }
  return trays;
}

// The messages the MQTT library gives are terse; say what they mean.
function friendlyError(err) {
  const m = String((err && err.message) || err || '');
  if (/not authori[sz]ed|bad user ?name or password/i.test(m)) return 'The printer refused the access code.';
  if (/ECONNREFUSED/.test(m)) return 'Nothing answered on port 8883 at that address.';
  if (/ETIMEDOUT|EHOSTUNREACH|ENETUNREACH|timed? ?out/i.test(m)) return 'Couldn’t reach the printer from the server.';
  return m.slice(0, 200) || 'The connection failed.';
}

// Connects, asks for a full report, and gathers what arrives for a few seconds.
// Resolves with what was seen — never with the access code.
// With `debug`, also returns one loaded tray exactly as the printer sent it, to
// see which fields a given printer and firmware actually provide.
function probe({ host, serial, accessCode, waitMs = 8000, debug = false }) {
  return new Promise((resolve) => {
    const started = Date.now();
    const seen = { connected: false, reports: 0, printer: null, ams: null, external: null, error: null, raw: null };
    let done = false;
    let timer = null;
    const client = mqtt.connect(`mqtts://${host}:${PORT}`, {
      username: 'bblp',
      password: accessCode,
      rejectUnauthorized: false, // the printer's certificate is self-signed
      connectTimeout: 6000,
      reconnectPeriod: 0, // one attempt: this is a test, not a session
      clientId: `printhive-${Math.random().toString(16).slice(2, 10)}`,
    });
    const finish = () => {
      if (done) return;
      done = true;
      clearTimeout(timer);
      client.end(true);
      resolve({ ...seen, ms: Date.now() - started });
    };
    timer = setTimeout(finish, waitMs);

    client.on('connect', () => {
      seen.connected = true;
      client.subscribe(`device/${serial}/report`, (err) => {
        if (err) { seen.error = `The printer wouldn’t let Printhive listen: ${err.message}`; return; }
        // The printer only sends everything when asked.
        client.publish(`device/${serial}/request`,
          JSON.stringify({ pushing: { sequence_id: '0', command: 'pushall' } }));
      });
    });
    client.on('message', (_topic, payload) => {
      seen.reports += 1;
      let msg;
      try { msg = JSON.parse(payload.toString()); } catch { return; }
      const p = msg && msg.print;
      if (!p) return;
      if (p.gcode_state) seen.printer = { ...(seen.printer || {}), state: p.gcode_state };
      if (p.mc_percent != null) seen.printer = { ...(seen.printer || {}), progress: Number(p.mc_percent) };
      if (p.ams && Array.isArray(p.ams.ams)) {
        seen.ams = describeAms(p.ams.ams);
        if (debug) {
          const unit = p.ams.ams[0] || {};
          seen.raw = {
            amsKeys: Object.keys(p.ams),
            unitKeys: Object.keys(unit),
            unitInfo: { info: unit.info, humidity: unit.humidity, temp: unit.temp },
            tray: (unit.tray || []).find((t) => t && t.tray_type) || null,
          };
        }
      }
      if (p.vt_tray) seen.external = describeTray(p.vt_tray, null);
    });
    client.on('error', (err) => {
      seen.error = friendlyError(err);
      finish();
    });
    client.on('close', () => { if (!seen.connected) finish(); });
  });
}

module.exports = { probe, describeAms, describeTray, friendlyError };