/**
 * 性能监控器 - 监控和优化前端性能
 */
class PerformanceMonitor {
    constructor() {
        this.metrics = new Map();
        this.observers = new Set();
        this.isEnabled = true;
        this.threshold = {
            renderTime: 1000, // 渲染时间阈值
            loadTime: 2000,   // 加载时间阈值
            memoryUsage: 100 * 1024 * 1024 // 内存使用阈值
        };
        
        this.init();
    }

    /**
     * 初始化性能监控
     */
    init() {
        if (typeof window !== 'undefined' && window.performance) {
            this.setupPerformanceObserver();
            this.setupMemoryMonitor();
        }
    }

    /**
     * 设置性能观察器
     */
    setupPerformanceObserver() {
        if ('PerformanceObserver' in window) {
            const observer = new PerformanceObserver((list) => {
                for (const entry of list.getEntries()) {
                    this.recordMetric(entry.name, {
                        duration: entry.duration,
                        startTime: entry.startTime,
                        type: entry.entryType
                    });
                }
            });

            observer.observe({ entryTypes: ['measure', 'navigation', 'resource'] });
        }
    }

    /**
     * 设置内存监控
     */
    setupMemoryMonitor() {
        if ('memory' in performance) {
            setInterval(() => {
                const memory = performance.memory;
                this.recordMetric('memory', {
                    used: memory.usedJSHeapSize,
                    total: memory.totalJSHeapSize,
                    limit: memory.jsHeapSizeLimit,
                    timestamp: Date.now()
                });

                // 检查内存使用是否超过阈值
                if (memory.usedJSHeapSize > this.threshold.memoryUsage) {
                    this.triggerAlert('high_memory_usage', {
                        used: memory.usedJSHeapSize,
                        limit: this.threshold.memoryUsage
                    });
                }
            }, 10000); // 每10秒检查一次
        }
    }

    /**
     * 记录性能指标
     * @param {string} name - 指标名称
     * @param {Object} data - 指标数据
     */
    recordMetric(name, data) {
        if (!this.isEnabled) return;

        if (!this.metrics.has(name)) {
            this.metrics.set(name, []);
        }

        const records = this.metrics.get(name);
        records.push({
            ...data,
            timestamp: Date.now()
        });

        // 限制记录数量
        if (records.length > 100) {
            records.shift();
        }

        // 触发观察者通知
        this.notifyObservers(name, data);
    }

    /**
     * 开始性能计时
     * @param {string} name - 计时器名称
     */
    startTimer(name) {
        if (typeof window !== 'undefined' && window.performance) {
            performance.mark(`${name}_start`);
        }
    }

    /**
     * 结束性能计时
     * @param {string} name - 计时器名称
     */
    endTimer(name) {
        if (typeof window !== 'undefined' && window.performance) {
            performance.mark(`${name}_end`);
            performance.measure(name, `${name}_start`, `${name}_end`);
        }
    }

    /**
     * 获取性能指标
     * @param {string} name - 指标名称
     */
    getMetric(name) {
        return this.metrics.get(name) || [];
    }

    /**
     * 获取平均渲染时间
     */
    getAverageRenderTime() {
        const renders = this.getMetric('template-render');
        if (renders.length === 0) return 0;

        const total = renders.reduce((sum, r) => sum + r.duration, 0);
        return total / renders.length;
    }

    /**
     * 添加性能观察者
     * @param {Function} callback - 回调函数
     */
    addObserver(callback) {
        this.observers.add(callback);
    }

    /**
     * 移除性能观察者
     * @param {Function} callback - 回调函数
     */
    removeObserver(callback) {
        this.observers.delete(callback);
    }

    /**
     * 通知观察者
     * @param {string} name - 指标名称
     * @param {Object} data - 指标数据
     */
    notifyObservers(name, data) {
        this.observers.forEach(callback => {
            try {
                callback(name, data);
            } catch (error) {
                console.error('Performance observer error:', error);
            }
        });
    }

    /**
     * 触发性能警报
     * @param {string} type - 警报类型
     * @param {Object} data - 警报数据
     */
    triggerAlert(type, data) {
        console.warn(`Performance Alert: ${type}`, data);
        
        // 可以在这里集成错误报告服务
        if (window.console && window.console.warn) {
            console.warn(`[Performance] ${type}:`, data);
        }
    }

    /**
     * 获取性能报告
     */
    getReport() {
        const report = {
            timestamp: Date.now(),
            metrics: {},
            summary: {
                totalRequests: 0,
                averageRenderTime: this.getAverageRenderTime(),
                cacheHitRate: 0
            }
        };

        // 汇总指标
        for (const [name, records] of this.metrics) {
            report.metrics[name] = {
                count: records.length,
                average: records.reduce((sum, r) => sum + (r.duration || 0), 0) / records.length,
                min: Math.min(...records.map(r => r.duration || 0)),
                max: Math.max(...records.map(r => r.duration || 0)),
                last: records[records.length - 1]
            };
        }

        return report;
    }

    /**
     * 清空性能数据
     */
    clear() {
        this.metrics.clear();
        this.observers.clear();
    }

    /**
     * 启用/禁用性能监控
     * @param {boolean} enabled - 是否启用
     */
    setEnabled(enabled) {
        this.isEnabled = enabled;
    }
}

// 全局性能监控器实例
window.performanceMonitor = new PerformanceMonitor();

// 集成到模板引擎和API客户端中
// 在template-engine.js和api-client.js中使用performanceMonitor.startTimer/endTimer