import type { DetectionResult } from './types';
import { CLASS_LABELS, VALIDATION_RULES } from './model-config';

/**
 * A temporal filter to smooth detections and reduce flickering.
 */
class TemporalFilter {
  private history: (DetectionResult | null)[] = [];
  private frameCount = 0;

  constructor(private consistencyFrames: number) {
    this.history = new Array(consistencyFrames).fill(null);
  }

  add(detection: DetectionResult | null): DetectionResult | null {
    this.history.shift();
    this.history.push(detection);

    const recentDetections = this.history.filter(d => d !== null);
    if (recentDetections.length >= this.consistencyFrames) {
      // Return the most confident detection from the recent history
      return recentDetections.reduce((prev, current) => (prev!.confidence > current!.confidence ? prev : current));
    }

    return null;
  }
}

/**
 * The InferencePipeline class handles post-processing of model outputs,
 * including filtering, validation, and temporal smoothing to prevent false positives.
 */
export class InferencePipeline {
  private temporalFilter: TemporalFilter;

  constructor() {
    this.temporalFilter = new TemporalFilter(VALIDATION_RULES.temporalConsistencyFrames);
  }

  /**
   * Processes the raw output from the TensorFlow.js model.
   * @param boxes Raw bounding boxes.
   * @param scores Raw confidence scores.
   * @param classes Raw class indices.
   * @param confidenceThreshold The current confidence threshold.
   * @returns A single, validated DetectionResult or null.
   */
  process(boxes: number[], scores: number[], classes: number[], confidenceThreshold: number): DetectionResult | null {
    const detections: DetectionResult[] = [];

    // Process up to 5 detections like the working implementation
    for (let i = 0; i < Math.min(5, scores.length); i++) {
      const score = scores[i];
      
      // Convert to percentage and check threshold like working implementation
      const scorePercent = score * 100;
      if (scorePercent < (confidenceThreshold * 100)) continue;

      // Extract bounding box [y_min, x_min, y_max, x_max] like working implementation
      const yMin = boxes[i * 4];
      const xMin = boxes[i * 4 + 1]; 
      const yMax = boxes[i * 4 + 2];
      const xMax = boxes[i * 4 + 3];
      
      // Convert to [x, y, width, height] format
      const bbox: [number, number, number, number] = [xMin, yMin, xMax - xMin, yMax - yMin];

      const detection: DetectionResult = {
        bbox,
        confidence: score,
        class: 'shoe', // Assume all detections are shoes
        timestamp: Date.now()
      };

      if (this.isValid(detection)) {
        detections.push(detection);
      }
    }

    if (detections.length === 0) {
      return this.temporalFilter.add(null);
    }

    // Get the single best detection
    const bestDetection = detections.reduce((prev, current) => (prev.confidence > current.confidence ? prev : current));
    
    return this.temporalFilter.add(bestDetection);
  }

  /**
   * Validates a detection against a set of rules.
   * @param detection The detection to validate.
   * @returns True if the detection is valid, false otherwise.
   */
  private isValid(detection: DetectionResult): boolean {
    const { bbox } = detection;
    const [, , width, height] = bbox;

    // Bounding box size validation (relative to a 320x320 input)
    const boxPixelWidth = width * 320;
    const boxPixelHeight = height * 320;
    if (boxPixelWidth < VALIDATION_RULES.minBoundingBoxSize || boxPixelHeight < VALIDATION_RULES.minBoundingBoxSize) {
      return false;
    }

    // Aspect ratio validation
    const aspectRatio = boxPixelWidth / boxPixelHeight;
    if (aspectRatio < VALIDATION_RULES.aspectRatioRange[0] || aspectRatio > VALIDATION_RULES.aspectRatioRange[1]) {
      return false;
    }

    return true;
  }
}