import type { IThroughputSample, IThroughputData, IThroughputHistoryPoint } from './models/metrics-types.js';

/**
 * Tracks throughput data using time-series sampling
 */
export class ThroughputTracker {
  private samples: IThroughputSample[] = [];
  private readonly maxSamples: number;
  private accumulatedBytesIn: number = 0;
  private accumulatedBytesOut: number = 0;
  private lastSampleTime: number = 0;
  
  constructor(retentionSeconds: number = 3600) {
    // Keep samples for the retention period at 1 sample per second
    this.maxSamples = retentionSeconds;
  }
  
  /**
   * Record bytes transferred (called on every data transfer)
   */
  public recordBytes(bytesIn: number, bytesOut: number): void {
    this.accumulatedBytesIn += bytesIn;
    this.accumulatedBytesOut += bytesOut;
  }
  
  /**
   * Take a sample of accumulated bytes (called every second)
   */
  public takeSample(): void {
    const now = Date.now();
    
    // Record accumulated bytes since last sample
    this.samples.push({
      timestamp: now,
      bytesIn: this.accumulatedBytesIn,
      bytesOut: this.accumulatedBytesOut
    });
    
    // Reset accumulators
    this.accumulatedBytesIn = 0;
    this.accumulatedBytesOut = 0;
    this.lastSampleTime = now;
    
    // Maintain circular buffer - remove oldest samples
    if (this.samples.length > this.maxSamples) {
      this.samples.shift();
    }
  }
  
  /**
   * Get throughput rate over specified window (bytes per second)
   */
  public getRate(windowSeconds: number): IThroughputData {
    if (this.samples.length === 0) {
      return { in: 0, out: 0 };
    }
    
    const now = Date.now();
    const windowStart = now - (windowSeconds * 1000);
    
    // Find samples within the window
    const relevantSamples = this.samples.filter(s => s.timestamp > windowStart);
    
    if (relevantSamples.length === 0) {
      return { in: 0, out: 0 };
    }
    
    // Sum bytes in the window
    const totalBytesIn = relevantSamples.reduce((sum, s) => sum + s.bytesIn, 0);
    const totalBytesOut = relevantSamples.reduce((sum, s) => sum + s.bytesOut, 0);
    
    // Calculate actual window duration (might be less than requested if not enough data)
    const actualWindowSeconds = Math.min(
      windowSeconds,
      (now - relevantSamples[0].timestamp) / 1000
    );
    
    // Avoid division by zero
    if (actualWindowSeconds === 0) {
      return { in: 0, out: 0 };
    }
    
    return {
      in: Math.round(totalBytesIn / actualWindowSeconds),
      out: Math.round(totalBytesOut / actualWindowSeconds)
    };
  }
  
  /**
   * Get throughput history for specified duration
   */
  public getHistory(durationSeconds: number): IThroughputHistoryPoint[] {
    const now = Date.now();
    const startTime = now - (durationSeconds * 1000);
    
    // Filter samples within duration
    const relevantSamples = this.samples.filter(s => s.timestamp > startTime);
    
    // Convert to history points with per-second rates
    const history: IThroughputHistoryPoint[] = [];
    
    for (let i = 0; i < relevantSamples.length; i++) {
      const sample = relevantSamples[i];
      
      // For the first sample or samples after gaps, we can't calculate rate
      if (i === 0 || sample.timestamp - relevantSamples[i - 1].timestamp > 2000) {
        history.push({
          timestamp: sample.timestamp,
          in: sample.bytesIn,
          out: sample.bytesOut
        });
      } else {
        // Calculate rate based on time since previous sample
        const prevSample = relevantSamples[i - 1];
        const timeDelta = (sample.timestamp - prevSample.timestamp) / 1000;
        
        history.push({
          timestamp: sample.timestamp,
          in: Math.round(sample.bytesIn / timeDelta),
          out: Math.round(sample.bytesOut / timeDelta)
        });
      }
    }
    
    return history;
  }
  
  /**
   * Clear all samples
   */
  public clear(): void {
    this.samples = [];
    this.accumulatedBytesIn = 0;
    this.accumulatedBytesOut = 0;
    this.lastSampleTime = 0;
  }
  
  /**
   * Get sample count for debugging
   */
  public getSampleCount(): number {
    return this.samples.length;
  }
}