videofolxtv/server/face-detection-service.ts

import { spawn } from 'child_process';
import path from 'path';

export interface FaceDetectionResult {
  success: boolean;
  faces_detected: number;
  primary_face_confidence: number;
  crop_info: {
    x: number;
    y: number;
    width: number;
    height: number;
  };
  original_dimensions: {
    width: number;
    height: number;
  };
  processed_image?: string;
  processing_strategy: 'face_centered' | 'center_crop';
  error?: string;
}

export class FaceDetectionService {
  private pythonScriptPath: string;

  constructor() {
    this.pythonScriptPath = path.join(__dirname, 'face-detection.py');
  }

  /**
   * Process thumbnail URL to detect faces and create centered crop
   */
  async processThumbnail(thumbnailUrl: string): Promise<FaceDetectionResult> {
    return new Promise((resolve, reject) => {
      const python = spawn('python3', [this.pythonScriptPath, thumbnailUrl]);
      
      let stdoutData = '';
      let stderrData = '';

      python.stdout.on('data', (data) => {
        stdoutData += data.toString();
      });

      python.stderr.on('data', (data) => {
        stderrData += data.toString();
      });

      python.on('close', (code) => {
        if (code !== 0) {
          console.error(`Face detection script exited with code ${code}`);
          console.error('stderr:', stderrData);
          resolve({
            success: false,
            faces_detected: 0,
            primary_face_confidence: 0,
            crop_info: { x: 0, y: 0, width: 0, height: 0 },
            original_dimensions: { width: 0, height: 0 },
            processing_strategy: 'center_crop',
            error: `Script exited with code ${code}: ${stderrData}`
          });
          return;
        }

        try {
          const result = JSON.parse(stdoutData);
          resolve(result);
        } catch (error) {
          console.error('Error parsing face detection result:', error);
          console.error('stdout:', stdoutData);
          resolve({
            success: false,
            faces_detected: 0,
            primary_face_confidence: 0,
            crop_info: { x: 0, y: 0, width: 0, height: 0 },
            original_dimensions: { width: 0, height: 0 },
            processing_strategy: 'center_crop',
            error: `Failed to parse result: ${error}`
          });
        }
      });

      python.on('error', (error) => {
        console.error('Failed to start face detection script:', error);
        resolve({
          success: false,
          faces_detected: 0,
          primary_face_confidence: 0,
          crop_info: { x: 0, y: 0, width: 0, height: 0 },
          original_dimensions: { width: 0, height: 0 },
          processing_strategy: 'center_crop',
          error: `Failed to start script: ${error.message}`
        });
      });
    });
  }

  /**
   * Calculate CSS object-position for face-centered display
   */
  calculateObjectPosition(cropInfo: FaceDetectionResult['crop_info'], originalDimensions: { width: number; height: number }): string {
    if (!cropInfo || !originalDimensions.width || !originalDimensions.height) {
      return 'center center';
    }

    // Calculate the percentage position of the crop center
    const cropCenterX = cropInfo.x + cropInfo.width / 2;
    const cropCenterY = cropInfo.y + cropInfo.height / 2;
    
    const positionX = (cropCenterX / originalDimensions.width) * 100;
    const positionY = (cropCenterY / originalDimensions.height) * 100;
    
    return `${Math.max(0, Math.min(100, positionX))}% ${Math.max(0, Math.min(100, positionY))}%`;
  }

  /**
   * Get optimized thumbnail URL with face detection applied
   */
  async getOptimizedThumbnailInfo(thumbnailUrl: string) {
    try {
      const result = await this.processThumbnail(thumbnailUrl);
      
      return {
        originalUrl: thumbnailUrl,
        faceCenterPosition: this.calculateObjectPosition(result.crop_info, result.original_dimensions),
        facesDetected: result.faces_detected,
        confidence: result.primary_face_confidence,
        strategy: result.processing_strategy,
        processedSuccessfully: result.success
      };
    } catch (error) {
      console.error('Error optimizing thumbnail:', error);
      return {
        originalUrl: thumbnailUrl,
        faceCenterPosition: 'center center',
        facesDetected: 0,
        confidence: 0,
        strategy: 'center_crop' as const,
        processedSuccessfully: false
      };
    }
  }
}

// Export singleton instance
export const faceDetectionService = new FaceDetectionService();