Initial commit: SyncWatch Chrome extension + WebSocket server

server/package.json

@@ -0,0 +1,15 @@
+{
+  "name": "syncwatch-server",
+  "version": "1.0.0",
+  "description": "WebSocket relay server for SyncWatch Chrome extension",
+  "main": "server.js",
+  "scripts": {
+    "start": "node server.js"
+  },
+  "engines": {
+    "node": ">=16"
+  },
+  "dependencies": {
+    "ws": "^8.18.0"
+  }
+}

server/server.js

@@ -0,0 +1,98 @@
+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}`);
+});