const path = require('path');
const fs = require('fs');
const crypto = require('crypto');

const licensePath = path.resolve('z32_k2.lic');
const SYM_KEY_PREFIX = Buffer.from('SYMKEY').toString('base64');

try {
  const licenseFileInput = fs.readFileSync(licensePath, 'utf-8');

  const publicKey = readPublicKey(licenseFileInput);
  console.log(publicKey);
  const licenseData = readLicenseData(licenseFileInput, publicKey);
  console.log(licenseData);

} catch(err) {
  console.log(err);
}

function readPublicKey(licenseFileInput) {
    const lines = licenseFileInput.split('\n');
    const indexKeyEnd = lines.indexOf('-----END PUBLIC KEY-----');

    var key = '';

    for (var i = 0; i <= indexKeyEnd; i++) {
      key += lines[i];
      key += i < indexKeyEnd ? '\n' : '';
    }

    return key;
}

function readLicenseData(licenseFileInput, publicKey) {
  const lines = licenseFileInput.split('\n');

  for (var i = 0; i < lines.length; i++) {
      if (lines[i].startsWith(SYM_KEY_PREFIX)) {
          const b64SymKey = lines[i];
          const b64LicenseData = lines[i + 1];

          const encSymKey = Buffer.from(b64SymKey.substring(SYM_KEY_PREFIX.length), 'base64');
          const symKey = Buffer.from(crypto.publicDecrypt(publicKey, encSymKey), 'base64');
          console.log(symKey);

          const encLicenseData = Buffer.from(b64LicenseData, 'base64');
          const decipher = crypto.createDecipher('aes-256-cbc', symKey);

          var licenseData = Buffer.concat([decipher.update(encLicenseData), decipher.final()]);
          licenseData = Buffer.from(licenseData, 'base64').toString('utf-8');
          console.log(licenseData);
          return;
      }

      else if (i + 1 === lines.length) {
          var b64LicenseData = lines[i];
          var encLicenseData = Buffer.from(b64LicenseData, 'base64');
          var licenseData = crypto.publicDecrypt(publicKey, encLicenseData);

          return Buffer.from(licenseData, 'base64').toString('utf-8');
      }
  }
}