#!/usr/bin/env node
// tj-snapshot.mjs — capture a live snapshot of the TransJakarta bus feed (MQTT over WSS).
//
// The broker (wss://mqtt.tj.co.id:8084/mqtt) is anonymous. This tool connects,
// subscribes, and records the last known state of every bus it sees.
//
// Setup:  npm install mqtt        (in this directory, or a parent dir)
// Usage:  node tj-snapshot.mjs [--topic /mobile_armada/#] [--seconds 60] [--out snapshot.json]
//
// Output: summary on stdout; with --out, a JSON file:
//   { capturedAt, durationSec, topic, messages, busCount, buses: { <bus_body_no>: {...} } }
//
// Notes: undocumented infrastructure — be gentle; one connection is enough.
//        Whole fleet: '/mobile_armada/#'. One area: '/mobile_armada/0018-0022/#'.

import mqtt from 'mqtt';
import fs from 'fs';

const args = process.argv.slice(2);
const getArg = (name, fallback) => {
  const i = args.indexOf(name);
  return i >= 0 && args[i + 1] ? args[i + 1] : fallback;
};

const topic = getArg('--topic', '/mobile_armada/#');
const seconds = parseInt(getArg('--seconds', '60'), 10) || 60;
const outFile = getArg('--out', '');

const out = { capturedAt: new Date().toISOString(), durationSec: seconds, topic, messages: 0, buses: {} };

const client = mqtt.connect('wss://mqtt.tj.co.id:8084/mqtt', {
  protocolVersion: 4, keepalive: 30, clean: true, connectTimeout: 15000, reconnectPeriod: 0
});

client.on('connect', () => client.subscribe(topic, { qos: 0 }));
client.on('error', (e) => console.error('MQTT error:', e.message));

client.on('message', (t, payload) => {
  out.messages++;
  try {
    const d = JSON.parse(payload.toString());
    if (!d.bus_body_no) return;
    out.buses[d.bus_body_no] = {
      lat: d.latitude, lng: d.longitude, bearing: d.bearing,
      route: d.route_code, trip: d.trip_id, headsign: d.trip_headsign,
      type: d.type, direction: d.direction,
      currStop: d.curr_stops, nextStop: d.next_stops,
      etaNextStopMin: d.estimated_time_next_stops,
      lastUpdate: d.timestamp, mqttTopic: t
    };
  } catch { /* skip malformed */ }
});

setTimeout(() => {
  out.busCount = Object.keys(out.buses).length;
  console.log(`Captured ${out.messages} messages, ${out.busCount} unique buses in ${seconds}s`);
  if (outFile) {
    fs.writeFileSync(outFile, JSON.stringify(out));
    console.log(`Snapshot written to ${outFile}`);
  }
  client.end(true);
  process.exit(0);
}, seconds * 1000);