'use strict';

/**
 * A stand-in for Companion's tRPC websocket, so the module can be built and
 * tested without the real thing:
 *
 *   node test/companion-mock.js 18000
 *
 * then point Companion Buttons at host 127.0.0.1, port 18000 in /admin.
 *
 * It serves the three subscriptions the module uses — pages.watch,
 * preview.graphics.controlId and controls.watchControl — over a hand-rolled
 * websocket (no deps), with three pages: a status page with a page-up
 * button, a camera page, and an unnamed page holding only navigation. Page 1's first button flips between green and red every two
 * seconds, like a status button; page 1's second button redraws the same
 * picture every 300 ms, like a button fed a variable that has not changed.
 * Every 30 s it sends PING and drops a client that does not answer PONG,
 * the way Companion does.
 *
 *   --rename-after <s>   rename page 2 after s seconds (an `update` change)
 *   --move-after <s>     move the flipping button to page 2 after s seconds
 */

const http = require('http');
const crypto = require('crypto');
const zlib = require('zlib');

/* ── a solid-colour PNG, with a lighter band so pictures differ ─────── */

const CRC_TABLE = Array.from({ length: 256 }, (_, n) => {
  let c = n;
  for (let k = 0; k < 8; k += 1) c = c & 1 ? 0xedb88320 ^ (c >>> 1) : c >>> 1;
  return c >>> 0;
});

function crc32(buf) {
  let c = 0xffffffff;
  for (const b of buf) c = CRC_TABLE[(c ^ b) & 0xff] ^ (c >>> 8);
  return (c ^ 0xffffffff) >>> 0;
}

function chunk(type, data) {
  const len = Buffer.alloc(4);
  len.writeUInt32BE(data.length);
  const body = Buffer.concat([Buffer.from(type, 'ascii'), data]);
  const crc = Buffer.alloc(4);
  crc.writeUInt32BE(crc32(body));
  return Buffer.concat([len, body, crc]);
}

function png([r, g, b], size = 72) {
  const ihdr = Buffer.alloc(13);
  ihdr.writeUInt32BE(size, 0);
  ihdr.writeUInt32BE(size, 4);
  ihdr[8] = 8; // bit depth
  ihdr[9] = 2; // RGB
  const rows = [];
  for (let y = 0; y < size; y += 1) {
    const row = Buffer.alloc(1 + size * 3);
    const band = y > size * 0.4 && y < size * 0.6;
    for (let x = 0; x < size; x += 1) {
      row[1 + x * 3] = band ? 255 : r;
      row[2 + x * 3] = band ? 255 : g;
      row[3 + x * 3] = band ? 255 : b;
    }
    rows.push(row);
  }
  const sig = Buffer.from([0x89, 0x50, 0x4e, 0x47, 0x0d, 0x0a, 0x1a, 0x0a]);
  const out = Buffer.concat([sig, chunk('IHDR', ihdr), chunk('IDAT', zlib.deflateSync(Buffer.concat(rows))), chunk('IEND', Buffer.alloc(0))]);
  return `data:image/png;base64,${out.toString('base64')}`;
}

/* ── the minimal websocket server (RFC 6455, text frames only) ────────── */

function frame(text) {
  const payload = Buffer.from(text, 'utf8');
  let head;
  if (payload.length < 126) {
    head = Buffer.from([0x81, payload.length]);
  } else if (payload.length < 65536) {
    head = Buffer.alloc(4);
    head[0] = 0x81;
    head[1] = 126;
    head.writeUInt16BE(payload.length, 2);
  } else {
    head = Buffer.alloc(10);
    head[0] = 0x81;
    head[1] = 127;
    head.writeBigUInt64BE(BigInt(payload.length), 2);
  }
  return Buffer.concat([head, payload]);
}

function readFrames(state, data, onText, onClose) {
  state.buf = Buffer.concat([state.buf, data]);
  for (;;) {
    const b = state.buf;
    if (b.length < 2) return;
    const op = b[0] & 0x0f;
    let len = b[1] & 0x7f;
    let off = 2;
    if (len === 126) {
      if (b.length < 4) return;
      len = b.readUInt16BE(2);
      off = 4;
    } else if (len === 127) {
      if (b.length < 10) return;
      len = Number(b.readBigUInt64BE(2));
      off = 10;
    }
    const masked = (b[1] & 0x80) !== 0;
    const mask = masked ? b.subarray(off, off + 4) : null;
    if (masked) off += 4;
    if (b.length < off + len) return;
    const payload = Buffer.from(b.subarray(off, off + len));
    if (mask) for (let i = 0; i < payload.length; i += 1) payload[i] ^= mask[i % 4];
    state.buf = b.subarray(off + len);
    if (op === 0x8) return onClose();
    if (op === 0x1) onText(payload.toString('utf8'));
  }
}

/* ── Companion's side ─────────────────────────────────────────────────── */

function startMock(port = 0, { renameAfter = 0, moveAfter = 0, log = () => {} } = {}) {
  const pages = {
    p1: { id: 'p1', name: '1\\nStatus', controls: { 0: { 0: 'bank:flip', 1: 'bank:steady', 2: 'bank:blue' }, 1: { 0: 'bank:up1' } } },
    p2: { id: 'p2', name: 'Cameras', controls: { 0: { 0: 'bank:cam1' }, 1: { 3: 'bank:cam2' } } },
    p3: { id: 'p3', name: 'PAGE', controls: { 0: { 0: 'bank:up3' } } },
  };
  const layered = (value, isExpression = false) => ({
    type: 'button-layered',
    style: { layers: [{ id: 'canvas', type: 'canvas' }, { id: 'text0', type: 'text', text: { value, isExpression } }] },
  });
  const configs = {
    'bank:flip': layered('FLIP'),
    'bank:steady': layered('Steady'),
    'bank:blue': layered('Blue'),
    'bank:cam1': { type: 'button', style: { text: 'CAM 1' } },
    'bank:cam2': layered('CAM 2'),
    'bank:up1': { type: 'pageup', style: {} },
    'bank:up3': { type: 'pageup', style: {} },
  };
  const order = ['p1', 'p2', 'p3'];
  const looks = {
    'bank:steady': png([200, 140, 0]),
    'bank:blue': png([20, 60, 200]),
    'bank:cam1': png([90, 90, 90]),
    'bank:cam2': png([120, 0, 120]),
  };
  const GREEN = png([0, 160, 60]);
  const RED = png([200, 20, 20]);
  let flipRed = false;
  looks['bank:flip'] = GREEN;

  const clients = new Set();
  const stats = { connections: 0, pongs: 0, subscriptions: 0, stops: 0 };

  function send(client, msg) {
    if (client.closed) return;
    try {
      client.socket.write(frame(typeof msg === 'string' ? msg : JSON.stringify(msg)));
    } catch {
      /* gone */
    }
  }

  function pageUpdate(change) {
    for (const c of clients) for (const [id, sub] of c.subs) if (sub.path === 'pages.watch') send(c, { id, result: { type: 'data', data: change } });
  }

  function redraw(controlId) {
    for (const c of clients) {
      for (const [id, sub] of c.subs) {
        if (sub.path === 'preview.graphics.controlId' && sub.input.controlId === controlId) {
          send(c, { id, result: { type: 'data', data: looks[controlId] || null } });
        }
      }
    }
  }

  function onMessage(client, text) {
    if (text === 'PONG') {
      client.awaitingPong = false;
      stats.pongs += 1;
      return;
    }
    let msg;
    try {
      msg = JSON.parse(text);
    } catch {
      return;
    }
    if (msg.method === 'subscription.stop') {
      client.subs.delete(msg.id);
      stats.stops += 1;
      return send(client, { id: msg.id, result: { type: 'stopped' } });
    }
    if (msg.method !== 'subscription') return send(client, { id: msg.id, error: { message: 'mock: only subscriptions' } });
    const { path, input } = msg.params || {};
    if (path === 'controls.watchControl') {
      const cfg = configs[input && input.controlId];
      if (!cfg) return send(client, { id: msg.id, error: { message: `Control ${input && input.controlId} not found` } });
      stats.subscriptions += 1;
      client.subs.set(msg.id, { path, input });
      send(client, { id: msg.id, result: { type: 'started' } });
      return send(client, { id: msg.id, result: { type: 'data', data: { type: 'init', config: cfg, runtime: {} } } });
    }
    if (path !== 'pages.watch' && path !== 'preview.graphics.controlId') {
      return send(client, { id: msg.id, error: { message: `No procedure found on path "${path}"` } });
    }
    stats.subscriptions += 1;
    client.subs.set(msg.id, { path, input });
    send(client, { id: msg.id, result: { type: 'started' } });
    if (path === 'pages.watch') {
      send(client, { id: msg.id, result: { type: 'data', data: { type: 'init', order: [...order], pages: JSON.parse(JSON.stringify(pages)) } } });
    } else {
      send(client, { id: msg.id, result: { type: 'data', data: looks[input.controlId] || null } });
    }
  }

  const server = http.createServer((req, res) => {
    res.writeHead(200, { 'Content-Type': 'text/plain' });
    res.end('companion mock\n');
  });

  server.on('upgrade', (req, socket) => {
    if (new URL(req.url, 'http://x').pathname !== '/trpc') {
      socket.end('HTTP/1.1 404 Not Found\r\n\r\n');
      return;
    }
    const accept = crypto.createHash('sha1').update(`${req.headers['sec-websocket-key']}258EAFA5-E914-47DA-95CA-C5AB0DC85B11`).digest('base64');
    socket.write(`HTTP/1.1 101 Switching Protocols\r\nUpgrade: websocket\r\nConnection: Upgrade\r\nSec-WebSocket-Accept: ${accept}\r\n\r\n`);
    const client = { socket, subs: new Map(), state: { buf: Buffer.alloc(0) }, closed: false, awaitingPong: false };
    clients.add(client);
    stats.connections += 1;
    log(`client connected (${clients.size})`);
    const close = () => {
      if (client.closed) return;
      client.closed = true;
      clients.delete(client);
      socket.destroy();
      log(`client gone (${clients.size})`);
    };
    socket.on('data', (d) => readFrames(client.state, d, (t) => onMessage(client, t), close));
    socket.on('close', close);
    socket.on('error', close);
  });

  const timers = [
    setInterval(() => {
      flipRed = !flipRed;
      looks['bank:flip'] = flipRed ? RED : GREEN;
      redraw('bank:flip');
    }, 2000),
    setInterval(() => redraw('bank:steady'), 300),
    setInterval(() => {
      for (const c of clients) {
        if (c.awaitingPong) {
          log('no PONG — dropping client');
          c.socket.destroy();
          continue;
        }
        c.awaitingPong = true;
        send(c, 'PING');
      }
    }, 30000),
  ];
  if (renameAfter) {
    timers.push(setTimeout(() => {
      pages.p2.name = 'Cameras Renamed';
      pageUpdate({ type: 'update', updatedOrder: null, added: [], changes: [{ id: 'p2', name: 'Cameras Renamed', controls: [] }] });
    }, renameAfter * 1000));
  }
  if (moveAfter) {
    timers.push(setTimeout(() => {
      delete pages.p1.controls[0][0];
      pages.p2.controls[1][0] = 'bank:flip';
      pageUpdate({
        type: 'update',
        updatedOrder: null,
        added: [],
        changes: [
          { id: 'p1', name: null, controls: [{ row: 0, column: 0, controlId: null }] },
          { id: 'p2', name: null, controls: [{ row: 1, column: 0, controlId: 'bank:flip' }] },
        ],
      });
    }, moveAfter * 1000));
  }

  return new Promise((resolve) => {
    server.listen(port, '127.0.0.1', () => {
      resolve({
        port: server.address().port,
        stats,
        clients,
        pageUpdate,
        redraw,
        looks,
        pages,
        configs,
        /** Drop every client without a close frame, as a crash or a cable pull would. */
        dropAll() {
          for (const c of clients) c.socket.destroy();
        },
        close() {
          for (const t of timers) clearInterval(t);
          for (const c of clients) c.socket.destroy();
          return new Promise((r) => server.close(() => r()));
        },
      });
    });
  });
}

module.exports = { startMock, png };

if (require.main === module) {
  const args = process.argv.slice(2);
  const opt = (name) => {
    const i = args.indexOf(name);
    return i >= 0 ? Number(args[i + 1]) || 0 : 0;
  };
  const port = Number(args.find((a) => /^\d+$/.test(a))) || 18000;
  startMock(port, { renameAfter: opt('--rename-after'), moveAfter: opt('--move-after'), log: (m) => console.log(`[companion-mock] ${m}`) }).then((m) => {
    console.log(`[companion-mock] listening on 127.0.0.1:${m.port} — point Companion Buttons at 127.0.0.1 port ${m.port}`);
  });
}