const { WebSocketServer, WebSocket } = require('ws');
const http = require('http');

const PORT = process.env.PORT || 8080;

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

const wss = new WebSocketServer({ server });

// Map<roomCode, Set<WebSocket>>
const rooms = new Map();

function generateCode() {
  let code;
  do {
    code = Math.floor(100000 + Math.random() * 900000).toString();
  } while (rooms.has(code));
  return code;
}

function broadcast(room, message, exclude) {
  const data = JSON.stringify(message);
  for (const client of room) {
    if (client !== exclude && client.readyState === WebSocket.OPEN) {
      client.send(data);
    }
  }
}

wss.on('connection', (ws) => {
  ws.roomCode = null;

  ws.on('message', (raw) => {
    let msg;
    try { msg = JSON.parse(raw); } catch { return; }

    switch (msg.type) {
      case 'create': {
        if (ws.roomCode) return;
        const code = generateCode();
        rooms.set(code, new Set([ws]));
        ws.roomCode = code;
        ws.send(JSON.stringify({ type: 'created', code }));
        break;
      }

      case 'join': {
        if (ws.roomCode) return;
        const code = String(msg.code || '');
        const room = rooms.get(code);
        if (!room) {
          ws.send(JSON.stringify({ type: 'error', message: 'Room not found' }));
          return;
        }
        if (room.size >= 2) {
          ws.send(JSON.stringify({ type: 'error', message: 'Room is full' }));
          return;
        }
        room.add(ws);
        ws.roomCode = code;
        ws.send(JSON.stringify({ type: 'joined', code, memberCount: room.size }));
        broadcast(room, { type: 'peer_joined' }, ws);
        break;
      }

      case 'sync': {
        if (!ws.roomCode) return;
        const room = rooms.get(ws.roomCode);
        if (!room) return;
        broadcast(room, { type: 'sync', action: msg.action, time: msg.time }, ws);
        break;
      }

      case 'ping':
        ws.send(JSON.stringify({ type: 'pong' }));
        break;
    }
  });

  ws.on('close', () => {
    if (!ws.roomCode) return;
    const room = rooms.get(ws.roomCode);
    if (!room) return;
    room.delete(ws);
    if (room.size === 0) {
      rooms.delete(ws.roomCode);
    } else {
      broadcast(room, { type: 'peer_left' }, null);
    }
  });
});

server.listen(PORT, () => {
  console.log(`SyncWatch server listening on port ${PORT}`);
});