real-time-collaboration-engine

# Real-Time Collaboration Engine ## Overview Enables multiple users to collaborate in real-time on shared content with presence awareness and conflict-free updates. ## Decision Framework ### When to use - Multiple users editing same content - Live presence indicators needed - Real-time data synchronization required ### When NOT to use - Single-user applications - Batch processing workflows ## Trigger Phrases - "Real-time updates" - "Live collaboration" - "Show who's online" - "Multiple users editing" - "WebSocket connection" ## Technology Options | Technology | Best For | Complexity | Scale | |-----------|----------|------------|-------| | WebSockets | Custom solutions | High | Medium | | Socket.io | Node.js apps | Medium | Medium | | Pusher/Ably | Managed service | Low | High | | WebRTC | P2P, video | Very High | Low | | SSE | Server→Client only | Low | High | ## Presence System ```javascript class PresenceManager { constructor(channel) { this.channel = channel; this.users = new Map(); } async join(userId, metadata) { this.users.set(userId, { ...metadata, joinedAt: Date.now(), lastSeen: Date.now() }); await this.channel.broadcast('user:joined', { userId, metadata }); } async updateCursor(userId, position) { await this.channel.broadcast('cursor:moved', { userId, position }); this.users.get(userId).lastSeen = Date.now(); } async leave(userId) { this.users.delete(userId); await this.channel.broadcast('user:left', { userId }); } getActiveUsers() { const now = Date.now(); return Array.from(this.users.entries()) .filter(([_, u]) => now - u.lastSeen < 30000); } } ``` ## Conflict Resolution ### Operational Transform ```javascript class OTEngine { constructor() { this.document = ''; this.revision = 0; this.buffer = []; } apply(operation) { // Transform against concurrent operations let transformed = operation; for (const concurrent of this.buffer) { transformed = this.transform(transformed, concurrent); } this.document = this.execute(transformed); this.revision++; return transformed; } transform(op1, op2) { // Transform op1 against op2 if (op1.position <= op2.position) { return op1; } return { ...op1, position: op1.position + op2.length }; } } ``` ## Connection States ``` CONNECTING → CONNECTED → DISCONNECTED ↓ ↓ ↓ [retry] [active] [reconnect] ↓ ↓ ↓ CONNECTED SYNCING CONNECTED ``` ## Error Classification | Error Type | Severity | Recovery | |-----------|----------|----------| | Connection lost | Warning | Auto-reconnect | | Conflict detected | Info | OT/CRDT merge | | Auth expired | Error | Re-authenticate | | Server error | Critical | Fallback to local |