Kutum OCR – Intelligent Document Extraction & Processing

// Multi-model OCR orchestrator
interface OcrResult {
  documentType: DocumentType;
  confidence: number;
  extractedFields: Record<string, ExtractedField>;
  rawText: string;
  validationErrors: string[];
}

interface ExtractedField {
  value: string;
  confidence: number;
  boundingBox?: BoundingBox;
  source: 'tesseract' | 'vision_api' | 'gpt4_vision' | 'mrz_parser' | 'qr_decode';
}

async function processDocument(imageBuffer: Buffer): Promise<OcrResult> {
  // Stage 1: Preprocessing
  const enhancedImage = await preprocessImage(imageBuffer);
  
  // Stage 2: Classification
  const documentType = await classifyDocument(enhancedImage);
  
  // Stage 3: Route to specialized extractor
  let extractedFields: Record<string, ExtractedField>;
  
  switch (documentType) {
    case 'passport':
      extractedFields = await extractPassport(enhancedImage);
      break;
    case 'aadhaar':
      extractedFields = await extractAadhaar(enhancedImage);
      break;
    case 'health_report':
      extractedFields = await extractWithGPT4Vision(enhancedImage, HEALTH_REPORT_SCHEMA);
      break;
    default:
      extractedFields = await extractGeneric(enhancedImage);
  }
  
  // Stage 4: Validation
  const validationErrors = validateExtraction(documentType, extractedFields);
  
  return {
    documentType,
    confidence: calculateOverallConfidence(extractedFields),
    extractedFields,
    rawText: await tesseractExtract(enhancedImage),
    validationErrors
  };
}

// Passport-specific extraction with MRZ parsing
async function extractPassport(image: Buffer): Promise<Record<string, ExtractedField>> {
  const fields: Record<string, ExtractedField> = {};
  
  // Try MRZ extraction first (most reliable)
  const mrzData = await parseMRZ(image);
  if (mrzData.isValid) {
    fields['holder_name'] = { value: mrzData.name, confidence: 0.99, source: 'mrz_parser' };
    fields['passport_number'] = { value: mrzData.documentNumber, confidence: 0.99, source: 'mrz_parser' };
    fields['nationality'] = { value: mrzData.nationality, confidence: 0.99, source: 'mrz_parser' };
    fields['date_of_birth'] = { value: mrzData.dob, confidence: 0.99, source: 'mrz_parser' };
    fields['expiry_date'] = { value: mrzData.expiry, confidence: 0.99, source: 'mrz_parser' };
  }
  
  // Fall back to Vision API for visual details
  const visualData = await extractWithVisionAPI(image, 'passport');
  fields['place_of_issue'] = visualData.placeOfIssue;
  fields['photo'] = visualData.photoRegion;
  
  return fields;
}

// Aadhaar-specific extraction with QR decoding
async function extractAadhaar(image: Buffer): Promise<Record<string, ExtractedField>> {
  const fields: Record<string, ExtractedField> = {};
  
  // Try QR code extraction (cryptographically verified)
  const qrData = await decodeAadhaarQR(image);
  if (qrData.isValid) {
    fields['aadhaar_number'] = { value: qrData.uid, confidence: 1.0, source: 'qr_decode' };
    fields['holder_name'] = { value: qrData.name, confidence: 1.0, source: 'qr_decode' };
    fields['date_of_birth'] = { value: qrData.dob, confidence: 1.0, source: 'qr_decode' };
    fields['gender'] = { value: qrData.gender, confidence: 1.0, source: 'qr_decode' };
    fields['address'] = { value: qrData.address, confidence: 1.0, source: 'qr_decode' };
  }
  
  // Visual extraction for non-QR data
  const visualData = await extractWithOCR(image, 'aadhaar');
  fields['vid'] = visualData.vid; // Virtual ID if present
  
  return fields;
}