/**
 * WebSocket Alert Server
 * Real-time alert broadcasting for call analysis events and anomalies
 * Connects to CallAnalysisEngine and pushes alerts to subscribed clients
 */

import { WebSocketServer, WebSocket } from 'ws';
import { CallAnalysisEngine, CallEvent, Anomaly, SentimentAnalysis, AnalysisResult } from '../../src/lib/inference/call-analysis-engine';
import { jwtVerify, SignJWT } from 'jose';

export type AlertType =
  | 'anomaly'
  | 'call_event'
  | 'quality_degraded'
  | 'sentiment_shift'
  | 'call_summary'
  | 'connection'
  | 'disconnection';

export type AlertSeverity = 'info' | 'low' | 'medium' | 'high' | 'critical';

export interface AlertPayload {
  id: string;
  type: AlertType;
  severity: AlertSeverity;
  timestamp: number;
  callId?: string;
  title: string;
  message: string;
  data: Record<string, unknown>;
  actionable: boolean;
}

export interface AlertServerConfig {
  port?: number;
  enableAuth?: boolean;
  jwtSecret?: string;
  allowedOrigins?: string[];
  alertCooldownMs?: number;
  maxSubscribers?: number;
  enableCallCorrelation?: boolean;
}

export interface SubscriberSession {
  ws: WebSocket;
  userId?: string;
  callIds: Set<string>;
  lastAlertTime: Map<string, number>;
  subscribedAt: number;
}

const DEFAULT_CONFIG: Required<AlertServerConfig> = {
  port: 8088,
  enableAuth: true,
  jwtSecret: process.env.ALERT_SERVER_JWT_SECRET || '',
  allowedOrigins: ['http://localhost:3000'],
  alertCooldownMs: 5000,
  maxSubscribers: 100,
  enableCallCorrelation: true,
};

/**
 * JWT verification helper
 */
async function verifyJWT(token: string, secret: string): Promise<any | null> {
  try {
    const decoded = await jwtVerify(token, new TextEncoder().encode(secret), {
      algorithms: ['HS256'],
    });
    return decoded;
  } catch (error) {
    console.error('[AlertServer] JWT verification failed:', (error as Error).message);
    return null;
  }
}

export class AlertServer {
  private wss: WebSocketServer | null = null;
  private config: Required<AlertServerConfig>;
  private subscribers: Map<string, SubscriberSession> = new Map();
  private analysisEngines: Map<string, CallAnalysisEngine> = new Map();
  private alertHistory: AlertPayload[] = [];
  private maxAlertHistory: number = 500;
  private isRunning: boolean = false;

  constructor(config: AlertServerConfig = {}) {
    this.config = { ...DEFAULT_CONFIG, ...config };
  }

  async start(): Promise<void> {
    this.wss = new WebSocketServer({
      port: this.config.port,
      maxPayload: 1024 * 1024,
    });

    this.wss.on('connection', (ws: WebSocket, req) => {
      this.handleConnection(ws, req);
    });

    this.wss.on('error', (error: Error) => {
      console.error(`[AlertServer] WebSocket error: ${error.message}`);
    });

    this.isRunning = true;
    console.log(`[AlertServer] Listening on port ${this.config.port}`);
  }

  private handleConnection(ws: WebSocket, req: import('http').IncomingMessage): void {
    const url = new URL(req.url || '', `http://${req.headers.host}`);
    const sessionId = url.searchParams.get('sessionId') || `sub-${Date.now()}-${Math.random().toString(36).slice(2)}`;
    let userId = url.searchParams.get('userId') || undefined;
    const callId = url.searchParams.get('callId') || undefined;

    // Origin validation
    const origin = req.headers.origin;
    if (origin && !this.config.allowedOrigins.includes(origin)) {
      ws.close(1008, 'Origin not allowed');
      return;
    }

    // JWT Authentication (if enabled)
    if (this.config.enableAuth && this.config.jwtSecret) {
      const authHeader = req.headers.authorization;
      if (!authHeader || !authHeader.startsWith('Bearer ')) {
        ws.close(4001, 'Missing or invalid JWT token');
        return;
      }

      const token = authHeader.substring(7);
      const decoded = verifyJWT(token, this.config.jwtSecret);
      
      if (!decoded) {
        ws.close(4002, 'Invalid or expired JWT token');
        return;
      }

      // Extract user ID from token if present
      userId = (decoded as any).sub || userId;
    }

    if (this.subscribers.size >= this.config.maxSubscribers) {
      ws.close(1013, 'Too many subscribers');
      return;
    }

    const session: SubscriberSession = {
      ws,
      userId,
      callIds: callId ? new Set([callId]) : new Set(),
      lastAlertTime: new Map(),
      subscribedAt: Date.now(),
    };

    this.subscribers.set(sessionId, session);

    ws.send(JSON.stringify({
      type: 'connected',
      payload: { sessionId, userId, timestamp: Date.now() },
    }));

    ws.on('message', (data: Buffer | ArrayBuffer) => {
      this.handleMessage(sessionId, data);
    });

    ws.on('close', () => {
      this.subscribers.delete(sessionId);
      console.log(`[AlertServer] Subscriber disconnected: ${sessionId}`);
    });

    ws.on('error', (error: Error) => {
      console.error(`[AlertServer] Subscriber error (${sessionId}): ${error.message}`);
    });

    console.log(`[AlertServer] Subscriber connected: ${sessionId}${callId ? ` (call: ${callId})` : ''}`);
  }

  private handleMessage(sessionId: string, data: Buffer | ArrayBuffer): void {
    try {
      const message = JSON.parse(data.toString());
      const session = this.subscribers.get(sessionId);
      if (!session) return;

      switch (message.type) {
        case 'subscribe':
          if (message.callId) {
            session.callIds.add(message.callId);
          }
          break;

        case 'unsubscribe':
          if (message.callId) {
            session.callIds.delete(message.callId);
          }
          break;

        case 'ping':
          session.ws.send(JSON.stringify({ type: 'pong', timestamp: Date.now() }));
          break;
      }
    } catch (error) {
      console.error(`[AlertServer] Message parse error: ${(error as Error).message}`);
    }
  }

  bindAnalysisEngine(callId: string, engine: CallAnalysisEngine): void {
    this.analysisEngines.set(callId, engine);

    engine.on('result', (result: AnalysisResult) => {
      this.processAnalysisResult(callId, result);
    });

    engine.on('events', (events: CallEvent[]) => {
      events.forEach(event => {
        this.sendAlert({
          type: 'call_event',
          severity: event.severity as AlertSeverity,
          callId,
          title: this.formatEventType(event.type),
          message: this.formatEventMessage(event),
          data: { event, timestamp: event.timestamp },
          actionable: event.severity === 'high',
        });
      });
    });

    engine.on('anomalies', (anomalies: Anomaly[]) => {
      anomalies.forEach(anomaly => {
        this.sendAlert({
          type: 'anomaly',
          severity: anomaly.severity as AlertSeverity,
          callId,
          title: this.formatAnomalyType(anomaly.type),
          message: anomaly.description,
          data: {
            anomaly,
            confidence: anomaly.confidence,
            recommendation: anomaly.recommendation,
          },
          actionable: anomaly.severity === 'high' || anomaly.severity === 'critical',
        });
      });
    });

    console.log(`[AlertServer] Bound analysis engine for call: ${callId}`);
  }

  private processAnalysisResult(callId: string, result: AnalysisResult): void {
    if (result.callQuality.mosScore < 3.0) {
      this.sendAlert({
        type: 'quality_degraded',
        severity: result.callQuality.mosScore < 2.5 ? 'high' : 'medium',
        callId,
        title: 'Call Quality Degraded',
        message: `MOS score: ${result.callQuality.mosScore.toFixed(1)} (threshold: 3.0)`,
        data: result.callQuality as unknown as Record<string, unknown>,
        actionable: true,
      });
    }

    if (result.sentiment.sentiment === 'negative' && result.sentiment.confidence > 0.7) {
      this.sendAlert({
        type: 'sentiment_shift',
        severity: 'medium',
        callId,
        title: 'Negative Sentiment Detected',
        message: `Confidence: ${(result.sentiment.confidence * 100).toFixed(0)}%`,
        data: result.sentiment as unknown as Record<string, unknown>,
        actionable: false,
      });
    }
  }

  sendAlert(options: {
    type: AlertType;
    severity: AlertSeverity;
    callId?: string;
    title: string;
    message: string;
    data: Record<string, unknown>;
    actionable: boolean;
  }): void {
    const cooldownKey = `${options.callId}:${options.type}`;
    const now = Date.now();

    const sessionKeys = Array.from(this.subscribers.keys());
    for (const key of sessionKeys) {
      const session = this.subscribers.get(key);
      if (!session) continue;

      const lastTime = session.lastAlertTime.get(cooldownKey) || 0;
      if (now - lastTime < this.config.alertCooldownMs) continue;

      if (options.callId && session.callIds.size > 0 && !session.callIds.has(options.callId)) continue;

      const alert: AlertPayload = {
        id: `alert-${Date.now()}-${Math.random().toString(36).slice(2, 8)}`,
        type: options.type,
        severity: options.severity,
        timestamp: now,
        callId: options.callId,
        title: options.title,
        message: options.message,
        data: options.data,
        actionable: options.actionable,
      };

      this.alertHistory.push(alert);
      if (this.alertHistory.length > this.maxAlertHistory) {
        this.alertHistory.shift();
      }

      if (session.ws.readyState === WebSocket.OPEN) {
        session.ws.send(JSON.stringify(alert));
      }
      session.lastAlertTime.set(cooldownKey, now);
    }
  }

  broadcastCallSummary(callId: string, summary: string): void {
    this.sendAlert({
      type: 'call_summary',
      severity: 'info',
      callId,
      title: 'Call Analysis Summary',
      message: summary,
      data: { summary },
      actionable: false,
    });
  }

  getAlertHistory(limit: number = 50, callId?: string): AlertPayload[] {
    let history = this.alertHistory;
    if (callId) {
      history = history.filter(a => a.callId === callId);
    }
    return history.slice(-limit);
  }

  getSubscriberCount(): number {
    return this.subscribers.size;
  }

  getActiveCalls(): string[] {
    return Array.from(this.analysisEngines.keys());
  }

  getEngine(callId: string): CallAnalysisEngine | undefined {
    return this.analysisEngines.get(callId);
  }

  async stop(): Promise<void> {
    this.isRunning = false;

    this.subscribers.forEach((session) => {
      if (session.ws.readyState === WebSocket.OPEN) {
        session.ws.send(JSON.stringify({
          type: 'server_shutdown',
          payload: { timestamp: Date.now() },
        }));
        session.ws.close(1001, 'Server shutting down');
      }
    });

    this.analysisEngines.forEach((engine) => {
      engine.destroy();
    });

    if (this.wss) {
      await new Promise<void>((resolve) => {
        this.wss!.close(() => resolve());
      });
      this.wss = null;
    }

    console.log('[AlertServer] Stopped');
  }

  private formatEventType(type: string): string {
    const labels: Record<string, string> = {
      interrupt: 'Speaker Interrupt',
      overlap: 'Speech Overlap',
      long_pause: 'Long Pause',
      volume_spike: 'Volume Spike',
      silence: 'Silence Detected',
      speaker_change: 'Speaker Change',
    };
    return labels[type] || type;
  }

  private formatEventMessage(event: CallEvent): string {
    const messages: Record<string, string> = {
      interrupt: `Interrupt detected (${event.duration}ms)`,
      overlap: `Speech overlap detected (${event.duration}ms)`,
      long_pause: `Pause duration: ${(event.duration / 1000).toFixed(1)}s`,
      volume_spike: `Volume spike: ${(event.metadata.level as number)?.toFixed(2) || 'unknown'}`,
      silence: `Silence detected for ${(event.duration * 1000).toFixed(0)}ms`,
      speaker_change: 'Speaker change detected',
    };
    return messages[event.type] || 'Event detected';
  }

  private formatAnomalyType(type: string): string {
    const labels: Record<string, string> = {
      background_noise: 'Background Noise',
      echo: 'Echo Detected',
      distortion: 'Audio Distortion',
      dropouts: 'Audio Dropout',
      excessive_silence: 'Excessive Silence',
      volume_inconsistency: 'Volume Inconsistency',
    };
    return labels[type] || type;
  }
}

export default AlertServer;