import { EventEmitter } from 'events';
import { createHash } from 'crypto';

/**
 * Global CDN Manager for ZAI Platform
 * Handles worldwide content delivery, caching, and performance optimization
 */
export class GlobalCDNManager extends EventEmitter {
  constructor() {
    super();
    
    this.cdnNodes = new Map();
    this.cacheStorage = new Map();
    this.performanceMetrics = new Map();
    this.geoRouting = new Map();
    
    // CDN configuration
    this.config = {
      defaultTTL: 3600, // 1 hour
      maxCacheSize: 1000, // MB per node
      compressionEnabled: true,
      geoRoutingEnabled: true,
      performanceMonitoring: true
    };
    
    this.initializeCDNNodes();
    this.startPerformanceMonitoring();
    
    console.log('🌍 Global CDN Manager initialized');
  }

  /**
   * Initialize CDN nodes worldwide
   */
  initializeCDNNodes() {
    const nodes = [
      { id: 'us-east-1', region: 'North America', location: 'Virginia, USA', latency: 50 },
      { id: 'us-west-1', region: 'North America', location: 'California, USA', latency: 45 },
      { id: 'eu-west-1', region: 'Europe', location: 'Ireland', latency: 60 },
      { id: 'eu-central-1', region: 'Europe', location: 'Frankfurt, Germany', latency: 55 },
      { id: 'ap-southeast-1', region: 'Asia Pacific', location: 'Singapore', latency: 70 },
      { id: 'ap-northeast-1', region: 'Asia Pacific', location: 'Tokyo, Japan', latency: 65 },
      { id: 'ap-south-1', region: 'Asia Pacific', location: 'Mumbai, India', latency: 80 },
      { id: 'sa-east-1', region: 'South America', location: 'São Paulo, Brazil', latency: 90 }
    ];
    
    nodes.forEach(node => {
      const cdnNode = {
        ...node,
        status: 'ACTIVE',
        cacheHitRatio: 0.85,
        bandwidth: 1000, // Mbps
        connections: 0,
        cache: new Map(),
        cacheSize: 0, // MB
        lastHealthCheck: new Date().toISOString(),
        metrics: {
          requests: 0,
          cacheHits: 0,
          cacheMisses: 0,
          bytesServed: 0,
          averageResponseTime: 0
        }
      };
      
      this.cdnNodes.set(node.id, cdnNode);
    });
    
    console.log(`🌍 Initialized ${nodes.length} CDN nodes worldwide`);
  }

  /**
   * Get optimal CDN node for client
   */
  getOptimalNode(clientIP, userAgent = '') {
    // Simplified geo-location based on IP (in production, use real geo-IP service)
    const geoLocation = this.getGeoLocation(clientIP);
    
    // Find closest nodes by region
    const regionalNodes = Array.from(this.cdnNodes.values())
      .filter(node => node.status === 'ACTIVE')
      .map(node => ({
        ...node,
        distance: this.calculateDistance(geoLocation, node),
        load: this.calculateNodeLoad(node)
      }))
      .sort((a, b) => {
        // Sort by distance and load
        const aScore = a.distance + (a.load * 0.3);
        const bScore = b.distance + (b.load * 0.3);
        return aScore - bScore;
      });
    
    const optimalNode = regionalNodes[0];
    
    if (optimalNode) {
      console.log(`🎯 Optimal node for ${clientIP}: ${optimalNode.id} (${optimalNode.location})`);
      return optimalNode;
    }
    
    // Fallback to first available node
    return Array.from(this.cdnNodes.values()).find(node => node.status === 'ACTIVE');
  }

  /**
   * Cache content on CDN nodes
   */
  async cacheContent(contentKey, content, options = {}) {
    const {
      ttl = this.config.defaultTTL,
      regions = 'all',
      contentType = 'application/json',
      compress = this.config.compressionEnabled
    } = options;
    
    const cacheEntry = {
      key: contentKey,
      content: compress ? this.compressContent(content) : content,
      contentType,
      compressed: compress,
      size: this.calculateContentSize(content),
      ttl,
      createdAt: Date.now(),
      expiresAt: Date.now() + (ttl * 1000),
      hitCount: 0,
      lastAccessed: Date.now()
    };
    
    // Determine which nodes to cache on
    const targetNodes = regions === 'all' 
      ? Array.from(this.cdnNodes.keys())
      : this.getRegionalNodes(regions);
    
    const cacheResults = [];
    
    for (const nodeId of targetNodes) {
      const node = this.cdnNodes.get(nodeId);
      if (node && node.status === 'ACTIVE') {
        // Check cache capacity
        if (node.cacheSize + cacheEntry.size <= this.config.maxCacheSize) {
          node.cache.set(contentKey, { ...cacheEntry });
          node.cacheSize += cacheEntry.size;
          
          cacheResults.push({
            nodeId,
            success: true,
            size: cacheEntry.size
          });
          
          console.log(`💾 Content cached on ${nodeId}: ${contentKey} (${cacheEntry.size}MB)`);
        } else {
          // Evict old content to make space
          await this.evictOldContent(node);
          
          if (node.cacheSize + cacheEntry.size <= this.config.maxCacheSize) {
            node.cache.set(contentKey, { ...cacheEntry });
            node.cacheSize += cacheEntry.size;
            
            cacheResults.push({
              nodeId,
              success: true,
              size: cacheEntry.size,
              evicted: true
            });
          } else {
            cacheResults.push({
              nodeId,
              success: false,
              reason: 'Insufficient cache space'
            });
          }
        }
      }
    }
    
    this.emit('contentCached', { contentKey, results: cacheResults });
    return cacheResults;
  }

  /**
   * Serve content from CDN
   */
  async serveContent(contentKey, clientIP, userAgent = '') {
    const optimalNode = this.getOptimalNode(clientIP, userAgent);
    
    if (!optimalNode) {
      throw new Error('No CDN nodes available');
    }
    
    const startTime = Date.now();
    
    // Check if content is cached
    const cacheEntry = optimalNode.cache.get(contentKey);
    
    if (cacheEntry && cacheEntry.expiresAt > Date.now()) {
      // Cache hit
      cacheEntry.hitCount++;
      cacheEntry.lastAccessed = Date.now();
      
      optimalNode.metrics.requests++;
      optimalNode.metrics.cacheHits++;
      optimalNode.metrics.bytesServed += cacheEntry.size;
      
      const responseTime = Date.now() - startTime;
      this.updateResponseTime(optimalNode, responseTime);
      
      console.log(`⚡ Cache HIT: ${contentKey} from ${optimalNode.id} (${responseTime}ms)`);
      
      this.emit('cacheHit', {
        contentKey,
        nodeId: optimalNode.id,
        responseTime,
        size: cacheEntry.size
      });
      
      return {
        content: cacheEntry.compressed ? this.decompressContent(cacheEntry.content) : cacheEntry.content,
        contentType: cacheEntry.contentType,
        cacheHit: true,
        nodeId: optimalNode.id,
        responseTime
      };
    } else {
      // Cache miss - would fetch from origin server
      optimalNode.metrics.requests++;
      optimalNode.metrics.cacheMisses++;
      
      const responseTime = Date.now() - startTime + 200; // Simulate origin fetch time
      this.updateResponseTime(optimalNode, responseTime);
      
      console.log(`❌ Cache MISS: ${contentKey} from ${optimalNode.id} (${responseTime}ms)`);
      
      this.emit('cacheMiss', {
        contentKey,
        nodeId: optimalNode.id,
        responseTime
      });
      
      // In production, this would fetch from origin and cache the result
      return {
        content: null,
        contentType: 'application/json',
        cacheHit: false,
        nodeId: optimalNode.id,
        responseTime,
        error: 'Content not found in cache'
      };
    }
  }

  /**
   * Invalidate cached content
   */
  async invalidateContent(contentKey, regions = 'all') {
    const targetNodes = regions === 'all' 
      ? Array.from(this.cdnNodes.keys())
      : this.getRegionalNodes(regions);
    
    const invalidationResults = [];
    
    for (const nodeId of targetNodes) {
      const node = this.cdnNodes.get(nodeId);
      if (node) {
        const cacheEntry = node.cache.get(contentKey);
        if (cacheEntry) {
          node.cache.delete(contentKey);
          node.cacheSize -= cacheEntry.size;
          
          invalidationResults.push({
            nodeId,
            success: true,
            size: cacheEntry.size
          });
          
          console.log(`🗑️ Content invalidated on ${nodeId}: ${contentKey}`);
        } else {
          invalidationResults.push({
            nodeId,
            success: false,
            reason: 'Content not found'
          });
        }
      }
    }
    
    this.emit('contentInvalidated', { contentKey, results: invalidationResults });
    return invalidationResults;
  }

  /**
   * Get CDN performance metrics
   */
  getPerformanceMetrics() {
    const globalMetrics = {
      totalNodes: this.cdnNodes.size,
      activeNodes: 0,
      totalRequests: 0,
      totalCacheHits: 0,
      totalCacheMisses: 0,
      globalCacheHitRatio: 0,
      totalBytesServed: 0,
      averageResponseTime: 0,
      nodeMetrics: {}
    };
    
    let totalResponseTime = 0;
    let totalNodes = 0;
    
    for (const [nodeId, node] of this.cdnNodes.entries()) {
      if (node.status === 'ACTIVE') {
        globalMetrics.activeNodes++;
      }
      
      globalMetrics.totalRequests += node.metrics.requests;
      globalMetrics.totalCacheHits += node.metrics.cacheHits;
      globalMetrics.totalCacheMisses += node.metrics.cacheMisses;
      globalMetrics.totalBytesServed += node.metrics.bytesServed;
      
      if (node.metrics.averageResponseTime > 0) {
        totalResponseTime += node.metrics.averageResponseTime;
        totalNodes++;
      }
      
      globalMetrics.nodeMetrics[nodeId] = {
        region: node.region,
        location: node.location,
        status: node.status,
        cacheHitRatio: node.metrics.requests > 0 
          ? (node.metrics.cacheHits / node.metrics.requests) 
          : 0,
        averageResponseTime: node.metrics.averageResponseTime,
        cacheSize: node.cacheSize,
        connections: node.connections
      };
    }
    
    globalMetrics.globalCacheHitRatio = globalMetrics.totalRequests > 0
      ? (globalMetrics.totalCacheHits / globalMetrics.totalRequests)
      : 0;
    
    globalMetrics.averageResponseTime = totalNodes > 0
      ? (totalResponseTime / totalNodes)
      : 0;
    
    return globalMetrics;
  }

  /**
   * Start performance monitoring
   */
  startPerformanceMonitoring() {
    // Monitor performance every 30 seconds
    setInterval(() => {
      this.performHealthChecks();
      this.optimizeCacheDistribution();
      this.cleanupExpiredContent();
    }, 30000);
    
    console.log('📊 CDN performance monitoring started');
  }

  /**
   * Utility methods
   */
  getGeoLocation(clientIP) {
    // Simplified geo-location (in production, use real geo-IP service)
    const ipHash = createHash('md5').update(clientIP).digest('hex');
    const regions = ['us', 'eu', 'ap', 'sa'];
    const region = regions[parseInt(ipHash.charAt(0), 16) % regions.length];
    
    return { region, country: region.toUpperCase() };
  }
  
  calculateDistance(geoLocation, node) {
    // Simplified distance calculation
    const regionDistances = {
      'us': { 'us-east-1': 1, 'us-west-1': 2, 'eu-west-1': 8, 'ap-southeast-1': 10 },
      'eu': { 'eu-west-1': 1, 'eu-central-1': 2, 'us-east-1': 8, 'ap-southeast-1': 9 },
      'ap': { 'ap-southeast-1': 1, 'ap-northeast-1': 2, 'eu-west-1': 9, 'us-west-1': 8 },
      'sa': { 'sa-east-1': 1, 'us-east-1': 6, 'eu-west-1': 10, 'ap-southeast-1': 12 }
    };
    
    return regionDistances[geoLocation.region]?.[node.id] || 10;
  }
  
  calculateNodeLoad(node) {
    return (node.connections / 1000) + (node.cacheSize / this.config.maxCacheSize);
  }
  
  compressContent(content) {
    // Simplified compression (in production, use real compression)
    return JSON.stringify(content);
  }
  
  decompressContent(content) {
    // Simplified decompression
    return JSON.parse(content);
  }
  
  calculateContentSize(content) {
    // Calculate size in MB
    return JSON.stringify(content).length / (1024 * 1024);
  }
  
  getRegionalNodes(regions) {
    return Array.from(this.cdnNodes.values())
      .filter(node => regions.includes(node.region))
      .map(node => node.id);
  }
  
  async evictOldContent(node) {
    // Simple LRU eviction
    const entries = Array.from(node.cache.entries())
      .sort((a, b) => a[1].lastAccessed - b[1].lastAccessed);
    
    if (entries.length > 0) {
      const [key, entry] = entries[0];
      node.cache.delete(key);
      node.cacheSize -= entry.size;
      console.log(`🗑️ Evicted old content: ${key} from ${node.id}`);
    }
  }
  
  updateResponseTime(node, responseTime) {
    if (node.metrics.averageResponseTime === 0) {
      node.metrics.averageResponseTime = responseTime;
    } else {
      node.metrics.averageResponseTime = 
        (node.metrics.averageResponseTime * 0.9) + (responseTime * 0.1);
    }
  }
  
  performHealthChecks() {
    // Simplified health checks
    for (const [nodeId, node] of this.cdnNodes.entries()) {
      node.lastHealthCheck = new Date().toISOString();
      // In production, perform actual health checks
    }
  }
  
  optimizeCacheDistribution() {
    // Simplified cache optimization
    console.log('🔄 Optimizing cache distribution...');
  }
  
  cleanupExpiredContent() {
    const now = Date.now();
    let totalCleaned = 0;
    
    for (const [nodeId, node] of this.cdnNodes.entries()) {
      const expiredKeys = [];
      
      for (const [key, entry] of node.cache.entries()) {
        if (entry.expiresAt <= now) {
          expiredKeys.push(key);
        }
      }
      
      for (const key of expiredKeys) {
        const entry = node.cache.get(key);
        node.cache.delete(key);
        node.cacheSize -= entry.size;
        totalCleaned++;
      }
    }
    
    if (totalCleaned > 0) {
      console.log(`🧹 Cleaned up ${totalCleaned} expired cache entries`);
    }
  }
}
