const forge = require('node-forge');
const base64 = require('base64-js');

class RSACipher {
  /**
   * RSA Decryption
   * @param {string} privateKey - The private key in PEM format
   * @param {string} msg - The message to decrypt, encoded in base64
   * @returns {string} - The decrypted message
   */
  longDecrypt(privateKey, msg) {
    // Format the private key
    privateKey = `-----BEGIN RSA PRIVATE KEY-----\n${privateKey.match(/.{1,64}/g).join('\n')}\n-----END RSA PRIVATE KEY-----\n`;
    
    // Decode the base64 message
    const encryptedBytes = base64.toByteArray(msg);
    
    // Convert private key from PEM to forge object
    const privateKeyObj = forge.pki.privateKeyFromPem(privateKey);

    // Decrypt the message
    let decrypted = '';
    const blockSize = 128; // 128 bytes block size
    for (let i = 0; i < encryptedBytes.length; i += blockSize) {
      const block = encryptedBytes.slice(i, i + blockSize);
      decrypted += privateKeyObj.decrypt(forge.util.createBuffer(block), 'RSAES-PKCS1-V1_5');
    }
    
    return decrypted;
  }

  /**
   * Signature method
   * @param {string} privateKey - The private key in PEM format
   * @param {string} text - The text to sign
   * @returns {string} - Base64 encoded signature
   */
  sign(privateKey, text) {
    // Format the private key
    privateKey = `-----BEGIN RSA PRIVATE KEY-----\n${privateKey.match(/.{1,64}/g).join('\n')}\n-----END RSA PRIVATE KEY-----\n`;

    // Convert private key from PEM to forge object
    const privateKeyObj = forge.pki.privateKeyFromPem(privateKey);
    
    // Create a signature object
    const md = forge.md.md5.create();
    md.update(text, 'utf8');
    const signature = privateKeyObj.sign(md, 'RSA-SHA256');

    // Encode the signature in base64
    return base64.fromByteArray(signature);
  }
}

module.exports = RSACipher;