// 性能优化工具 - 提升小程序性能和用户体验
class PerformanceOptimizer {
  constructor() {
    this.imageCache = new Map();
    this.requestCache = new Map();
    this.lazyLoadObserver = null;
    this.performanceMetrics = {
      pageLoadTimes: [],
      apiResponseTimes: [],
      imageLoadTimes: []
    };
  }

  // 🔥 ===== 图片优化 =====

  // 图片懒加载
  initLazyLoad() {
    // 创建懒加载观察器
    this.lazyLoadObserver = wx.createIntersectionObserver();
    
    this.lazyLoadObserver.observe('.lazy-image', (res) => {
      if (res.intersectionRatio > 0) {
        // 图片进入视口，开始加载
        const dataset = res.dataset;
        if (dataset && dataset.src) {
          this.loadImage(dataset.src, res.id);
        }
      }
    });
  }

  // 优化图片加载
  async loadImage(src, elementId) {
    try {
      const startTime = Date.now();
      
      // 检查缓存
      if (this.imageCache.has(src)) {
        const cachedImage = this.imageCache.get(src);
        this.updateImageElement(elementId, cachedImage);
        return cachedImage;
      }

      // 预加载图片
      const imageInfo = await this.preloadImage(src);
      
      // 缓存图片信息
      this.imageCache.set(src, imageInfo);
      
      // 更新元素
      this.updateImageElement(elementId, imageInfo);
      
      // 记录性能指标
      const loadTime = Date.now() - startTime;
      this.recordImageLoadTime(loadTime);
      
      return imageInfo;
      
    } catch (error) {
      console.error('图片加载失败:', error);
      // 使用默认图片
      this.updateImageElement(elementId, { path: '/assets/images/placeholder.png' });
    }
  }

  // 预加载图片
  preloadImage(src) {
    return new Promise((resolve, reject) => {
      wx.getImageInfo({
        src: src,
        success: resolve,
        fail: reject
      });
    });
  }

  // 更新图片元素
  updateImageElement(elementId, imageInfo) {
    // 这里需要页面配合实现具体的更新逻辑
    console.log('更新图片元素:', elementId, imageInfo);
  }

  // 🔥 ===== 请求优化 =====

  // 请求缓存
  async cacheRequest(key, requestFn, ttl = 300000) { // 默认5分钟缓存
    const now = Date.now();
    
    // 检查缓存
    if (this.requestCache.has(key)) {
      const cached = this.requestCache.get(key);
      if (now - cached.timestamp < ttl) {
        console.log('使用缓存数据:', key);
        return cached.data;
      }
    }

    try {
      const startTime = Date.now();
      const data = await requestFn();
      const responseTime = Date.now() - startTime;
      
      // 缓存数据
      this.requestCache.set(key, {
        data: data,
        timestamp: now
      });
      
      // 记录性能指标
      this.recordApiResponseTime(responseTime);
      
      return data;
      
    } catch (error) {
      console.error('请求失败:', error);
      throw error;
    }
  }

  // 清除过期缓存
  clearExpiredCache() {
    const now = Date.now();
    const maxAge = 600000; // 10分钟
    
    for (const [key, value] of this.requestCache.entries()) {
      if (now - value.timestamp > maxAge) {
        this.requestCache.delete(key);
      }
    }
  }

  // 🔥 ===== 内存优化 =====

  // 清理内存
  cleanupMemory() {
    // 清理图片缓存
    if (this.imageCache.size > 50) {
      const entries = Array.from(this.imageCache.entries());
      const toDelete = entries.slice(0, entries.length - 30);
      toDelete.forEach(([key]) => {
        this.imageCache.delete(key);
      });
    }

    // 清理请求缓存
    this.clearExpiredCache();

    // 触发垃圾回收（如果可用）
    if (wx.triggerGC) {
      wx.triggerGC();
    }
  }

  // 监控内存使用
  monitorMemory() {
    if (wx.getPerformance) {
      const performance = wx.getPerformance();
      const memory = performance.memory;
      
      if (memory) {
        console.log('内存使用情况:', {
          used: this.formatBytes(memory.usedJSHeapSize),
          total: this.formatBytes(memory.totalJSHeapSize),
          limit: this.formatBytes(memory.jsHeapSizeLimit)
        });
        
        // 如果内存使用超过80%，触发清理
        if (memory.usedJSHeapSize / memory.jsHeapSizeLimit > 0.8) {
          console.warn('内存使用过高，开始清理');
          this.cleanupMemory();
        }
      }
    }
  }

  // 🔥 ===== 性能监控 =====

  // 记录页面加载时间
  recordPageLoadTime(loadTime) {
    this.performanceMetrics.pageLoadTimes.push(loadTime);
    
    // 只保留最近100条记录
    if (this.performanceMetrics.pageLoadTimes.length > 100) {
      this.performanceMetrics.pageLoadTimes.shift();
    }
  }

  // 记录API响应时间
  recordApiResponseTime(responseTime) {
    this.performanceMetrics.apiResponseTimes.push(responseTime);
    
    if (this.performanceMetrics.apiResponseTimes.length > 100) {
      this.performanceMetrics.apiResponseTimes.shift();
    }
  }

  // 记录图片加载时间
  recordImageLoadTime(loadTime) {
    this.performanceMetrics.imageLoadTimes.push(loadTime);
    
    if (this.performanceMetrics.imageLoadTimes.length > 100) {
      this.performanceMetrics.imageLoadTimes.shift();
    }
  }

  // 获取性能报告
  getPerformanceReport() {
    const report = {
      pageLoad: this.calculateStats(this.performanceMetrics.pageLoadTimes),
      apiResponse: this.calculateStats(this.performanceMetrics.apiResponseTimes),
      imageLoad: this.calculateStats(this.performanceMetrics.imageLoadTimes),
      cacheStats: {
        imageCache: this.imageCache.size,
        requestCache: this.requestCache.size
      }
    };
    
    console.log('性能报告:', report);
    return report;
  }

  // 计算统计数据
  calculateStats(times) {
    if (times.length === 0) {
      return { avg: 0, min: 0, max: 0, count: 0 };
    }
    
    const sum = times.reduce((a, b) => a + b, 0);
    const avg = sum / times.length;
    const min = Math.min(...times);
    const max = Math.max(...times);
    
    return {
      avg: Math.round(avg),
      min: min,
      max: max,
      count: times.length
    };
  }

  // 🔥 ===== 工具方法 =====

  // 格式化字节数
  formatBytes(bytes) {
    if (bytes === 0) return '0 B';
    
    const k = 1024;
    const sizes = ['B', 'KB', 'MB', 'GB'];
    const i = Math.floor(Math.log(bytes) / Math.log(k));
    
    return parseFloat((bytes / Math.pow(k, i)).toFixed(2)) + ' ' + sizes[i];
  }

  // 防抖函数
  debounce(func, wait) {
    let timeout;
    return function executedFunction(...args) {
      const later = () => {
        clearTimeout(timeout);
        func(...args);
      };
      clearTimeout(timeout);
      timeout = setTimeout(later, wait);
    };
  }

  // 节流函数
  throttle(func, limit) {
    let inThrottle;
    return function executedFunction(...args) {
      if (!inThrottle) {
        func.apply(this, args);
        inThrottle = true;
        setTimeout(() => inThrottle = false, limit);
      }
    };
  }

  // 🔥 ===== 初始化和清理 =====

  // 初始化性能优化
  init() {
    console.log('初始化性能优化器');
    
    // 初始化懒加载
    this.initLazyLoad();
    
    // 定期清理内存
    setInterval(() => {
      this.cleanupMemory();
    }, 300000); // 5分钟清理一次
    
    // 定期监控内存
    setInterval(() => {
      this.monitorMemory();
    }, 60000); // 1分钟监控一次
  }

  // 销毁优化器
  destroy() {
    console.log('销毁性能优化器');
    
    // 清理懒加载观察器
    if (this.lazyLoadObserver) {
      this.lazyLoadObserver.disconnect();
      this.lazyLoadObserver = null;
    }
    
    // 清理缓存
    this.imageCache.clear();
    this.requestCache.clear();
    
    // 清理性能指标
    this.performanceMetrics = {
      pageLoadTimes: [],
      apiResponseTimes: [],
      imageLoadTimes: []
    };
  }
}

// 创建全局单例
const performanceOptimizer = new PerformanceOptimizer();

module.exports = performanceOptimizer;