const JsBarcode = require('jsbarcode');
const QRCode = require('qrcode');
const { createCanvas } = require('canvas');

/**
 * Service for generating barcodes and QR codes for inventory products
 */
class CodeGenerationService {
  constructor() {
    this.supportedBarcodeFormats = ['CODE128', 'CODE39', 'EAN13', 'EAN8', 'UPC'];
    this.defaultBarcodeOptions = {
      format: 'CODE128',
      width: 2,
      height: 100,
      displayValue: true,
      fontSize: 20,
      textAlign: 'center',
      textPosition: 'bottom',
      textMargin: 2,
      fontOptions: '',
      font: 'monospace',
      background: '#ffffff',
      lineColor: '#000000',
      margin: 10
    };
    
    this.defaultQROptions = {
      errorCorrectionLevel: 'M',
      type: 'image/png',
      quality: 0.92,
      margin: 1,
      color: {
        dark: '#000000',
        light: '#FFFFFF'
      },
      width: 200
    };
  }

  /**
   * Generate barcode for a product code
   * @param {string} productCode - The product code to encode
   * @param {string} format - Barcode format (CODE128, CODE39, EAN13, etc.)
   * @param {Object} options - Additional barcode options
   * @returns {Promise<string>} Base64 encoded barcode image
   */
  async generateBarcode(productCode, format = 'CODE128', options = {}) {
    try {
      if (!productCode || typeof productCode !== 'string') {
        throw new Error('Product code must be a non-empty string');
      }

      if (!this.supportedBarcodeFormats.includes(format.toUpperCase())) {
        throw new Error(`Unsupported barcode format: ${format}. Supported formats: ${this.supportedBarcodeFormats.join(', ')}`);
      }

      // Validate product code for specific formats
      let processedCode = this._validateProductCodeForFormat(productCode, format);

      const barcodeOptions = {
        ...this.defaultBarcodeOptions,
        ...options,
        format: format.toUpperCase()
      };

      // Create canvas for barcode generation
      const canvas = createCanvas(400, 200);
      
      // Generate barcode
      JsBarcode(canvas, processedCode, barcodeOptions);
      
      // Convert to base64
      const base64Image = canvas.toDataURL('image/png');
      
      return {
        success: true,
        data: base64Image,
        format: format.toUpperCase(),
        productCode: productCode,
        metadata: {
          width: canvas.width,
          height: canvas.height,
          format: 'PNG'
        }
      };
    } catch (error) {
      return {
        success: false,
        error: error.message,
        productCode: productCode,
        format: format
      };
    }
  }

  /**
   * Generate QR code with embedded product data
   * @param {Object} productData - Product information to embed
   * @param {Object} options - QR code generation options
   * @returns {Promise<string>} Base64 encoded QR code image
   */
  async generateQRCode(productData, options = {}) {
    try {
      if (!productData || typeof productData !== 'object') {
        throw new Error('Product data must be an object');
      }

      if (!productData.product_code) {
        throw new Error('Product data must include product_code');
      }

      // Create structured data for QR code
      const qrData = {
        code: productData.product_code,
        desc: productData.description || '',
        cat: productData.category || '',
        uom: productData.unit_of_measure || '',
        ts: new Date().toISOString()
      };

      const qrOptions = {
        ...this.defaultQROptions,
        ...options
      };

      // Generate QR code
      const qrCodeDataURL = await QRCode.toDataURL(JSON.stringify(qrData), qrOptions);
      
      return {
        success: true,
        data: qrCodeDataURL,
        productCode: productData.product_code,
        embeddedData: qrData,
        metadata: {
          format: 'PNG',
          errorCorrectionLevel: qrOptions.errorCorrectionLevel,
          width: qrOptions.width
        }
      };
    } catch (error) {
      return {
        success: false,
        error: error.message,
        productData: productData
      };
    }
  }

  /**
   * Generate both barcode and QR code for a product
   * @param {Object} productData - Product information
   * @param {Object} options - Generation options
   * @returns {Promise<Object>} Object containing both codes
   */
  async generateBothCodes(productData, options = {}) {
    const barcodeOptions = options.barcode || {};
    const qrOptions = options.qr || {};
    const barcodeFormat = options.barcodeFormat || 'CODE128';

    const [barcodeResult, qrResult] = await Promise.all([
      this.generateBarcode(productData.product_code, barcodeFormat, barcodeOptions),
      this.generateQRCode(productData, qrOptions)
    ]);

    return {
      productCode: productData.product_code,
      barcode: barcodeResult,
      qrCode: qrResult,
      timestamp: new Date().toISOString()
    };
  }

  /**
   * Get supported barcode formats
   * @returns {Array<string>} List of supported formats
   */
  getSupportedFormats() {
    return [...this.supportedBarcodeFormats];
  }

  /**
   * Validate product code for specific barcode format
   * @private
   * @param {string} productCode - Product code to validate
   * @param {string} format - Barcode format
   * @returns {string} Processed product code for barcode generation
   */
  _validateProductCodeForFormat(productCode, format) {
    const upperFormat = format.toUpperCase();
    
    switch (upperFormat) {
      case 'EAN13':
        if (!/^\d{12,13}$/.test(productCode)) {
          throw new Error('EAN13 format requires 12-13 digits');
        }
        // For 13-digit codes, remove the last digit (check digit) for jsbarcode
        // jsbarcode will calculate the check digit automatically
        return productCode.length === 13 ? productCode.substring(0, 12) : productCode;
      case 'EAN8':
        if (!/^\d{7,8}$/.test(productCode)) {
          throw new Error('EAN8 format requires 7-8 digits');
        }
        // For 8-digit codes, remove the last digit (check digit) for jsbarcode
        return productCode.length === 8 ? productCode.substring(0, 7) : productCode;
      case 'UPC':
        if (!/^\d{11,12}$/.test(productCode)) {
          throw new Error('UPC format requires 11-12 digits');
        }
        // For 12-digit codes, remove the last digit (check digit) for jsbarcode
        return productCode.length === 12 ? productCode.substring(0, 11) : productCode;
      case 'CODE39':
        if (!/^[A-Z0-9\-. $\/+%]+$/.test(productCode)) {
          throw new Error('CODE39 format supports only uppercase letters, digits, and specific symbols');
        }
        return productCode;
      case 'CODE128':
        // CODE128 supports most ASCII characters, so minimal validation
        if (productCode.length === 0) {
          throw new Error('Product code cannot be empty');
        }
        return productCode;
      default:
        return productCode;
    }
  }

  /**
   * Parse QR code data back to product information
   * @param {string} qrData - Raw QR code data
   * @returns {Object} Parsed product data
   */
  parseQRCodeData(qrData) {
    try {
      const parsed = JSON.parse(qrData);
      return {
        success: true,
        productCode: parsed.code,
        description: parsed.desc,
        category: parsed.cat,
        unitOfMeasure: parsed.uom,
        timestamp: parsed.ts
      };
    } catch (error) {
      return {
        success: false,
        error: 'Invalid QR code data format',
        rawData: qrData
      };
    }
  }
}

module.exports = CodeGenerationService;