import { Queue, QueueEvents } from 'bullmq';
// import { getLogger } from '@stock-bot/logger';

// const logger = getLogger('queue-metrics');

export interface QueueMetrics {
  // Job counts
  waiting: number;
  active: number;
  completed: number;
  failed: number;
  delayed: number;
  paused?: number;
  
  // Performance metrics
  processingTime: {
    avg: number;
    min: number;
    max: number;
    p95: number;
    p99: number;
  };
  
  // Throughput
  throughput: {
    completedPerMinute: number;
    failedPerMinute: number;
    totalPerMinute: number;
  };
  
  // Job age
  oldestWaitingJob: Date | null;
  
  // Health
  isHealthy: boolean;
  healthIssues: string[];
}

export class QueueMetricsCollector {
  private processingTimes: number[] = [];
  private completedTimestamps: number[] = [];
  private failedTimestamps: number[] = [];
  private jobStartTimes = new Map<string, number>();
  private readonly maxSamples = 1000;
  private readonly metricsInterval = 60000; // 1 minute

  constructor(
    private queue: Queue,
    private queueEvents: QueueEvents
  ) {
    this.setupEventListeners();
  }

  /**
   * Setup event listeners for metrics collection
   */
  private setupEventListeners(): void {
    this.queueEvents.on('completed', () => {
      // Record completion
      this.completedTimestamps.push(Date.now());
      this.cleanupOldTimestamps();
    });

    this.queueEvents.on('failed', () => {
      // Record failure
      this.failedTimestamps.push(Date.now());
      this.cleanupOldTimestamps();
    });

    // Track processing times
    this.queueEvents.on('active', ({ jobId }) => {
      this.jobStartTimes.set(jobId, Date.now());
    });

    this.queueEvents.on('completed', ({ jobId }) => {
      const startTime = this.jobStartTimes.get(jobId);
      if (startTime) {
        const processingTime = Date.now() - startTime;
        this.recordProcessingTime(processingTime);
        this.jobStartTimes.delete(jobId);
      }
    });
  }

  /**
   * Record processing time
   */
  private recordProcessingTime(time: number): void {
    this.processingTimes.push(time);
    
    // Keep only recent samples
    if (this.processingTimes.length > this.maxSamples) {
      this.processingTimes = this.processingTimes.slice(-this.maxSamples);
    }
  }

  /**
   * Clean up old timestamps
   */
  private cleanupOldTimestamps(): void {
    const cutoff = Date.now() - this.metricsInterval;
    
    this.completedTimestamps = this.completedTimestamps.filter(ts => ts > cutoff);
    this.failedTimestamps = this.failedTimestamps.filter(ts => ts > cutoff);
  }

  /**
   * Collect current metrics
   */
  async collect(): Promise<QueueMetrics> {
    // Get job counts
    const [waiting, active, completed, failed, delayed] = await Promise.all([
      this.queue.getWaitingCount(),
      this.queue.getActiveCount(),
      this.queue.getCompletedCount(),
      this.queue.getFailedCount(),
      this.queue.getDelayedCount(),
    ]);
    
    // BullMQ doesn't have getPausedCount, check if queue is paused
    const paused = await this.queue.isPaused() ? waiting : 0;

    // Calculate processing time metrics
    const processingTime = this.calculateProcessingTimeMetrics();
    
    // Calculate throughput
    const throughput = this.calculateThroughput();
    
    // Get oldest waiting job
    const oldestWaitingJob = await this.getOldestWaitingJob();
    
    // Check health
    const { isHealthy, healthIssues } = this.checkHealth({
      waiting,
      active,
      failed,
      processingTime,
    });

    return {
      waiting,
      active,
      completed,
      failed,
      delayed,
      paused,
      processingTime,
      throughput,
      oldestWaitingJob,
      isHealthy,
      healthIssues,
    };
  }

  /**
   * Calculate processing time metrics
   */
  private calculateProcessingTimeMetrics(): QueueMetrics['processingTime'] {
    if (this.processingTimes.length === 0) {
      return { avg: 0, min: 0, max: 0, p95: 0, p99: 0 };
    }

    const sorted = [...this.processingTimes].sort((a, b) => a - b);
    const sum = sorted.reduce((acc, val) => acc + val, 0);
    
    return {
      avg: sorted.length > 0 ? Math.round(sum / sorted.length) : 0,
      min: sorted[0] || 0,
      max: sorted[sorted.length - 1] || 0,
      p95: sorted[Math.floor(sorted.length * 0.95)] || 0,
      p99: sorted[Math.floor(sorted.length * 0.99)] || 0,
    };
  }

  /**
   * Calculate throughput metrics
   */
  private calculateThroughput(): QueueMetrics['throughput'] {
    const now = Date.now();
    const oneMinuteAgo = now - 60000;
    
    const completedPerMinute = this.completedTimestamps.filter(ts => ts > oneMinuteAgo).length;
    const failedPerMinute = this.failedTimestamps.filter(ts => ts > oneMinuteAgo).length;
    
    return {
      completedPerMinute,
      failedPerMinute,
      totalPerMinute: completedPerMinute + failedPerMinute,
    };
  }

  /**
   * Get oldest waiting job
   */
  private async getOldestWaitingJob(): Promise<Date | null> {
    const waitingJobs = await this.queue.getWaiting(0, 1);
    
    if (waitingJobs.length > 0) {
      return new Date(waitingJobs[0].timestamp);
    }
    
    return null;
  }

  /**
   * Check queue health
   */
  private checkHealth(metrics: {
    waiting: number;
    active: number;
    failed: number;
    processingTime: QueueMetrics['processingTime'];
  }): { isHealthy: boolean; healthIssues: string[] } {
    const issues: string[] = [];
    
    // Check for high failure rate
    const failureRate = metrics.failed / (metrics.failed + this.completedTimestamps.length);
    if (failureRate > 0.1) {
      issues.push(`High failure rate: ${(failureRate * 100).toFixed(1)}%`);
    }
    
    // Check for queue backlog
    if (metrics.waiting > 1000) {
      issues.push(`Large queue backlog: ${metrics.waiting} jobs waiting`);
    }
    
    // Check for slow processing
    if (metrics.processingTime.avg > 30000) { // 30 seconds
      issues.push(`Slow average processing time: ${(metrics.processingTime.avg / 1000).toFixed(1)}s`);
    }
    
    // Check for stalled active jobs
    if (metrics.active > 100) {
      issues.push(`High number of active jobs: ${metrics.active}`);
    }
    
    return {
      isHealthy: issues.length === 0,
      healthIssues: issues,
    };
  }

  /**
   * Get formatted metrics report
   */
  async getReport(): Promise<string> {
    const metrics = await this.collect();
    
    return `
Queue Metrics Report
===================
Status: ${metrics.isHealthy ? '✅ Healthy' : '⚠️ Issues Detected'}

Job Counts:
- Waiting: ${metrics.waiting}
- Active: ${metrics.active}
- Completed: ${metrics.completed}
- Failed: ${metrics.failed}
- Delayed: ${metrics.delayed}
- Paused: ${metrics.paused}

Performance:
- Avg Processing Time: ${(metrics.processingTime.avg / 1000).toFixed(2)}s
- Min/Max: ${(metrics.processingTime.min / 1000).toFixed(2)}s / ${(metrics.processingTime.max / 1000).toFixed(2)}s
- P95/P99: ${(metrics.processingTime.p95 / 1000).toFixed(2)}s / ${(metrics.processingTime.p99 / 1000).toFixed(2)}s

Throughput:
- Completed/min: ${metrics.throughput.completedPerMinute}
- Failed/min: ${metrics.throughput.failedPerMinute}
- Total/min: ${metrics.throughput.totalPerMinute}

${metrics.oldestWaitingJob ? `Oldest Waiting Job: ${metrics.oldestWaitingJob.toISOString()}` : 'No waiting jobs'}

${metrics.healthIssues.length > 0 ? `\nHealth Issues:\n${metrics.healthIssues.map(issue => `- ${issue}`).join('\n')}` : ''}
    `.trim();
  }

  /**
   * Export metrics in Prometheus format
   */
  async getPrometheusMetrics(): Promise<string> {
    const metrics = await this.collect();
    const queueName = this.queue.name;
    
    return `
# HELP queue_jobs_total Total number of jobs by status
# TYPE queue_jobs_total gauge
queue_jobs_total{queue="${queueName}",status="waiting"} ${metrics.waiting}
queue_jobs_total{queue="${queueName}",status="active"} ${metrics.active}
queue_jobs_total{queue="${queueName}",status="completed"} ${metrics.completed}
queue_jobs_total{queue="${queueName}",status="failed"} ${metrics.failed}
queue_jobs_total{queue="${queueName}",status="delayed"} ${metrics.delayed}
queue_jobs_total{queue="${queueName}",status="paused"} ${metrics.paused}

# HELP queue_processing_time_seconds Job processing time in seconds
# TYPE queue_processing_time_seconds summary
queue_processing_time_seconds{queue="${queueName}",quantile="0.5"} ${(metrics.processingTime.avg / 1000).toFixed(3)}
queue_processing_time_seconds{queue="${queueName}",quantile="0.95"} ${(metrics.processingTime.p95 / 1000).toFixed(3)}
queue_processing_time_seconds{queue="${queueName}",quantile="0.99"} ${(metrics.processingTime.p99 / 1000).toFixed(3)}
queue_processing_time_seconds_sum{queue="${queueName}"} ${(metrics.processingTime.avg * this.processingTimes.length / 1000).toFixed(3)}
queue_processing_time_seconds_count{queue="${queueName}"} ${this.processingTimes.length}

# HELP queue_throughput_per_minute Jobs processed per minute
# TYPE queue_throughput_per_minute gauge
queue_throughput_per_minute{queue="${queueName}",status="completed"} ${metrics.throughput.completedPerMinute}
queue_throughput_per_minute{queue="${queueName}",status="failed"} ${metrics.throughput.failedPerMinute}
queue_throughput_per_minute{queue="${queueName}",status="total"} ${metrics.throughput.totalPerMinute}

# HELP queue_health Queue health status
# TYPE queue_health gauge
queue_health{queue="${queueName}"} ${metrics.isHealthy ? 1 : 0}
    `.trim();
  }
}