'use strict';

const crypto = require('crypto')

const ALGORITHM = 'aes-256-gcm'
const BLOCK_SIZE_BYTES = 16; // 128 bit

/**
 * Provides easy encryption/decryption methods using AES 256 GCM.
 */
class Aes256Gcm {
  /**
   * No need to run the constructor. The class only has static methods.
   */
  constructor() { }

  /**
   * Encrypts text with AES 256 GCM.
   * @param {string} text - Cleartext to encode.
   * @param {string} secret - Shared secret key, must be 32 bytes.
   * @returns {object}
   */
  static encrypt(text, secret) {
    const iv = crypto.randomBytes(BLOCK_SIZE_BYTES);
    const cipher = crypto.createCipheriv(ALGORITHM, secret, iv);

    let ciphertext = cipher.update(text, 'utf8', 'base64');
    ciphertext  += cipher.final('base64');
    let finaltext  = ciphertext.substr(0, 32);
    console.log()
    return {
      finaltext,
      iv: iv.toString('base64'),
      tag: cipher.getAuthTag().toString('base64'),
    };
  }

  /**
   * Decrypts AES 256 CGM encrypted text.
   * @param {string} ciphertext - Base64-encoded ciphertext.
   * @param {string} iv - The base64-encoded initialization vector.
   * @param {string} tag - The base64-encoded authentication tag generated by getAuthTag().
   * @param {string} secret - Shared secret key, must be 32 bytes.
   * @returns {string}
   */
  static decrypt(ciphertext, iv, tag, secret) {
    const decipher = crypto.createDecipheriv(ALGORITHM, secret, Buffer.from(iv, 'base64'));
    decipher.setAuthTag(Buffer.from(tag, 'base64'));

    let cleartext = decipher.update(ciphertext, 'base64', 'utf8');
    cleartext += decipher.final('utf8');

    return cleartext;
  }
}

// Must be 32 bytes.
const SHARED_SECRET = '4d885c79-7c5e-41de-80eb-7c1e636b2ff4';
 
// Encrypt:
let test = Aes256Gcm.encrypt('hi', SHARED_SECRET.replace(/-/g, ""));
let test2 = JSON.stringify(test)
console.log(test)
console.log(test2)

let test3 = JSON.parse(test2)
console.log(test3)

let cleartext = Aes256Gcm.decrypt(test.ciphertext, test.iv, test.tag, SHARED_SECRET);
console.log(cleartext)


// module.exports = Aes256Gcm;