/**
 * QUIXZOOM Real-Time WebSocket Server
 *
 * Hanterar realtidskommunikation mellan Zoomers och backend.
 *
 * Flöde:
 *   Zoomer → Observation → WebSocket → Identity Engine → Knowledge Graph → Mission Generator → AI → Instruktion tillbaka
 *
 * Features:
 * - Låg fördröjning (< 100ms)
 * - Binära meddelanden för video/bilder
 * - JSON för metadata och instruktioner
 * - Heartbeat för att upptäcka frånkoppling
 * - Rum (rooms) för geografiska områden
 * - Autentisering via JWT
 */

const WebSocket = require('ws');
const http = require('http');
const crypto = require('crypto');

class RealtimeServer {
  constructor(options = {}) {
    this.port = options.port || 8080;
    this.heartbeatInterval = options.heartbeatInterval || 30000;
    this.maxMessageSize = options.maxMessageSize || 10 * 1024 * 1024; // 10MB

    this.wss = null;
    this.clients = new Map(); // clientId -> { ws, zoomerId, location, room }
    this.rooms = new Map(); // roomId -> Set(clientIds)
    this.messageHandlers = new Map();

    // Statistik
    this.stats = {
      connections: 0,
      messagesReceived: 0,
      messagesSent: 0,
      bytesReceived: 0,
      bytesSent: 0,
      errors: 0,
    };
  }

  /**
   * ============================================================
   * STARTA SERVER
   * ============================================================
   */

  start() {
    const server = http.createServer((req, res) => {
      res.writeHead(200, { 'Content-Type': 'application/json' });
      res.end(JSON.stringify({
        status: 'ok',
        service: 'quixzoom-websocket',
        stats: this.stats,
        connections: this.clients.size,
      }));
    });

    this.wss = new WebSocket.Server({
      server,
      maxPayload: this.maxMessageSize,
    });

    this.wss.on('connection', (ws, req) => this.handleConnection(ws, req));

    server.listen(this.port, () => {
      console.log(`[WS] Real-time server running on port ${this.port}`);
    });

    // Starta heartbeat
    this.startHeartbeat();

    return server;
  }

  /**
   * ============================================================
   * HANDLERS
   * ============================================================

   */

  registerHandler(messageType, handler) {
    this.messageHandlers.set(messageType, handler);
    console.log(`[WS] Registered handler: ${messageType}`);
  }

  /**
   * ============================================================
   * CONNECTION HANDLING
   * ============================================================
   */

  handleConnection(ws, req) {
    const clientId = this.generateClientId();
    const client = {
      id: clientId,
      ws,
      zoomerId: null,
      location: null,
      room: null,
      connectedAt: Date.now(),
      lastPing: Date.now(),
      messagesReceived: 0,
      messagesSent: 0,
    };

    this.clients.set(clientId, client);
    this.stats.connections++;

    console.log(`[WS] Client connected: ${clientId} (total: ${this.clients.size})`);

    // Skicka välkomstmeddelande
    this.sendToClient(clientId, {
      type: 'connected',
      clientId,
      timestamp: Date.now(),
    });

    ws.on('message', (data) => this.handleMessage(clientId, data));
    ws.on('close', () => this.handleDisconnect(clientId));
    ws.on('error', (error) => this.handleError(clientId, error));
    ws.on('pong', () => {
      client.lastPing = Date.now();
    });
  }

  handleMessage(clientId, data) {
    const client = this.clients.get(clientId);
    if (!client) return;

    this.stats.messagesReceived++;
    this.stats.bytesReceived += data.length;
    client.messagesReceived++;

    try {
      const message = JSON.parse(data);
      console.log(`[WS] [${clientId}] ${message.type}`);

      // Autentisering
      if (message.type === 'auth') {
        this.handleAuth(clientId, message.payload);
        return;
      }

      // Kräv autentisering
      if (!client.zoomerId) {
        this.sendToClient(clientId, {
          type: 'error',
          error: 'Not authenticated',
        });
        return;
      }

      // Hantera meddelande
      const handler = this.messageHandlers.get(message.type);
      if (handler) {
        handler(message.payload, client, this);
      } else {
        console.log(`[WS] No handler for: ${message.type}`);
      }
    } catch (error) {
      console.error(`[WS] Error parsing message:`, error.message);
      this.stats.errors++;
    }
  }

  handleAuth(clientId, payload) {
    const client = this.clients.get(clientId);
    if (!client) return;

    // TODO: Verifiera JWT
    const zoomerId = payload.zoomerId || `zoomer_${clientId}`;
    client.zoomerId = zoomerId;

    console.log(`[WS] Client authenticated: ${clientId} as ${zoomerId}`);

    this.sendToClient(clientId, {
      type: 'auth_success',
      zoomerId,
    });
  }

  handleDisconnect(clientId) {
    const client = this.clients.get(clientId);
    if (!client) return;

    // Ta bort från rum
    if (client.room) {
      this.leaveRoom(clientId, client.room);
    }

    this.clients.delete(clientId);
    console.log(`[WS] Client disconnected: ${clientId} (total: ${this.clients.size})`);
  }

  handleError(clientId, error) {
    console.error(`[WS] Client error: ${clientId}`, error.message);
    this.stats.errors++;
  }

  /**
   * ============================================================
   * RUM (GEOGRAFISKA OMRÅDEN)
   * ============================================================
   */

  joinRoom(clientId, roomId) {
    const client = this.clients.get(clientId);
    if (!client) return;

    // Lämna tidigare rum
    if (client.room) {
      this.leaveRoom(clientId, client.room);
    }

    // Gå med i nytt rum
    if (!this.rooms.has(roomId)) {
      this.rooms.set(roomId, new Set());
    }
    this.rooms.get(roomId).add(clientId);
    client.room = roomId;

    console.log(`[WS] ${clientId} joined room: ${roomId}`);
  }

  leaveRoom(clientId, roomId) {
    const room = this.rooms.get(roomId);
    if (room) {
      room.delete(clientId);
      if (room.size === 0) {
        this.rooms.delete(roomId);
      }
    }

    const client = this.clients.get(clientId);
    if (client) {
      client.room = null;
    }

    console.log(`[WS] ${clientId} left room: ${roomId}`);
  }

  broadcastToRoom(roomId, message, excludeClientId = null) {
    const room = this.rooms.get(roomId);
    if (!room) return;

    for (const clientId of room) {
      if (clientId !== excludeClientId) {
        this.sendToClient(clientId, message);
      }
    }
  }

  /**
   * ============================================================
   * SKICKA MEDDELANDEN
   * ============================================================
   */

  sendToClient(clientId, message) {
    const client = this.clients.get(clientId);
    if (!client || client.ws.readyState !== WebSocket.OPEN) return;

    const data = JSON.stringify(message);
    client.ws.send(data);
    client.messagesSent++;
    this.stats.messagesSent++;
    this.stats.bytesSent += data.length;
  }

  broadcast(message, excludeClientId = null) {
    for (const [clientId, client] of this.clients) {
      if (clientId !== excludeClientId && client.ws.readyState === WebSocket.OPEN) {
        const data = JSON.stringify(message);
        client.ws.send(data);
        client.messagesSent++;
        this.stats.messagesSent++;
        this.stats.bytesSent += data.length;
      }
    }
  }

  /**
   * ============================================================
   * HEARTBEAT
   * ============================================================
   */

  startHeartbeat() {
    setInterval(() => {
      const now = Date.now();
      for (const [clientId, client] of this.clients) {
        if (now - client.lastPing > this.heartbeatInterval * 2) {
          console.log(`[WS] Client timeout: ${clientId}`);
          client.ws.terminate();
          this.handleDisconnect(clientId);
        } else {
          client.ws.ping();
        }
      }
    }, this.heartbeatInterval);
  }

  /**
   * ============================================================
   * HJÄLPMETODER
   * ============================================================
   */

  generateClientId() {
    return crypto.randomBytes(8).toString('hex');
  }

  getStats() {
    return {
      ...this.stats,
      activeConnections: this.clients.size,
      activeRooms: this.rooms.size,
    };
  }
}

// Exportera
module.exports = RealtimeServer;

// Demo
if (require.main === module) {
  const server = new RealtimeServer({ port: 8080 });

  // Registrera handlers
  server.registerHandler('observation', async (payload, client, server) => {
    console.log(`[WS] Observation from ${client.zoomerId}:`, payload.objectType);

    // Simulera processing
    await new Promise(resolve => setTimeout(resolve, 50));

    // Skicka bekräftelse
    server.sendToClient(client.id, {
      type: 'observation_ack',
      observationId: payload.observationId,
      status: 'received',
    });

    // Simulera Identity Engine
    await new Promise(resolve => setTimeout(resolve, 100));

    server.sendToClient(client.id, {
      type: 'identity_result',
      observationId: payload.observationId,
      objectId: `street_lamp_${Math.floor(Math.random() * 50000).toString().padStart(6, '0')}`,
      confidence: 0.85 + Math.random() * 0.15,
    });

    // Simulera Mission Generator
    await new Promise(resolve => setTimeout(resolve, 100));

    if (Math.random() > 0.7) {
      server.sendToClient(client.id, {
        type: 'instruction',
        instruction: 'Gå två meter närmare för bättre vinkel',
        priority: 'medium',
      });
    }
  });

  server.registerHandler('location_update', (payload, client, server) => {
    client.location = payload.location;

    // Uppdatera rum baserat på plats
    const roomId = server.getRoomForLocation(payload.location);
    if (roomId !== client.room) {
      server.joinRoom(client.id, roomId);
    }
  });

  server.registerHandler('telemetry', (payload, client, server) => {
    // Spara telemetri
    // console.log(`[WS] Telemetry from ${client.zoomerId}:`, payload);
  });

  // Hjälpmetod för rum
  server.getRoomForLocation = (location) => {
    const lat = Math.floor(location.lat * 10);
    const lng = Math.floor(location.lng * 10);
    return `${lat},${lng}`;
  };

  server.start();

  console.log('\n=== WEBSOCKET SERVER DEMO ===');
  console.log('Server running on ws://localhost:8080');
  console.log('');
  console.log('Test with:');
  console.log('  wscat -c ws://localhost:8080');
  console.log('');
  console.log('Or use the client below...');
}