const crypto = require('crypto');

/**
 * AES-256-CBC Decryption utility
 * Decrypts data encrypted with the frontend AES encrypt function
 */
function aesDecrypt(encryptedData) {
  try {
    const key = Buffer.from(process.env.KEY, 'utf8');
    const iv = Buffer.from(process.env.IV, 'utf8');
    
    // Create decipher
    const decipher = crypto.createDecipheriv('aes-256-cbc', key, iv);
    
    // Decrypt the data (encryptedData is base64 from CryptoJS)
    let decrypted = decipher.update(encryptedData, 'base64', 'utf8');
    decrypted += decipher.final('utf8');
    
    return decrypted;
  } catch (error) {
    console.error('Decryption error:', error.message);
    throw new Error('Failed to decrypt data');
  }
}

/**
 * Decrypt personal information fields in an object
 * Only decrypts specified personal info fields
 */
function decryptPersonalInfo(data, fieldsToDecrypt = []) {
  const decryptedData = { ...data };
  
  fieldsToDecrypt.forEach(field => {
    if (decryptedData[field] && typeof decryptedData[field] === 'string') {
      try {
        decryptedData[field] = aesDecrypt(decryptedData[field]);
      } catch (error) {
        console.error(`Failed to decrypt field: ${field}`);
        throw new Error(`Invalid encrypted data for field: ${field}`);
      }
    }
  });
  
  return decryptedData;
}

module.exports = { aesDecrypt, decryptPersonalInfo };