export class PerformanceMonitor {
  private static instance: PerformanceMonitor;
  private metrics: Map<string, number[]> = new Map();

  static getInstance(): PerformanceMonitor {
    if (!PerformanceMonitor.instance) {
      PerformanceMonitor.instance = new PerformanceMonitor();
    }
    return PerformanceMonitor.instance;
  }

  recordMetric(name: string, value: number) {
    if (!this.metrics.has(name)) {
      this.metrics.set(name, []);
    }
    this.metrics.get(name)!.push(value);
    
    if (this.metrics.get(name)!.length > 1000) {
      this.metrics.get(name)!.shift();
    }
  }

  getAverage(name: string): number {
    const values = this.metrics.get(name) || [];
    if (values.length === 0) return 0;
    return values.reduce((a, b) => a + b, 0) / values.length;
  }

  getPercentile(name: string, percentile: number): number {
    const values = this.metrics.get(name) || [];
    if (values.length === 0) return 0;
    
    const sorted = [...values].sort((a, b) => a - b);
    const index = Math.ceil((percentile / 100) * sorted.length) - 1;
    return sorted[Math.max(0, index)] ?? 0;
  }

  getCount(name: string): number {
    return this.metrics.get(name)?.length || 0;
  }

  getMin(name: string): number {
    const values = this.metrics.get(name) || [];
    if (values.length === 0) return 0;
    return Math.min(...values);
  }

  getMax(name: string): number {
    const values = this.metrics.get(name) || [];
    if (values.length === 0) return 0;
    return Math.max(...values);
  }

  getStats(name: string) {
    return {
      count: this.getCount(name),
      avg: this.getAverage(name),
      min: this.getMin(name),
      max: this.getMax(name),
      p50: this.getPercentile(name, 50),
      p95: this.getPercentile(name, 95),
      p99: this.getPercentile(name, 99),
    };
  }

  clearMetrics(name?: string) {
    if (name) {
      this.metrics.delete(name);
    } else {
      this.metrics.clear();
    }
  }
}

export const monitor = PerformanceMonitor.getInstance();