import * as crypto from 'crypto'

export function sha256(data: string | Buffer) {
  return crypto
    .createHash('sha256')
    .update(data)
    .digest()
}

export function createEncryptionToken(
  oldTokenBuff: Buffer,
  updateToken: string
) {
  const updateTokenBuff = Buffer.from(updateToken, 'hex')
  const mergedBuffer = Buffer.concat(
    [oldTokenBuff, updateTokenBuff],
    oldTokenBuff.length + updateTokenBuff.length
  )
  return sha256(mergedBuffer)
}

export function encrypt(data: string, ivKey: Buffer) {
  if (typeof data !== 'string') {
    throw new Error('data no es un string')
  }
  if (!(ivKey instanceof Buffer)) {
    throw new Error('ivKey no es un buffer')
  }

  if (ivKey.length !== 32) {
    throw new Error('ivKey tiene que tener tamaño 32')
  }

  const stringIVKey = ivKey.toString('hex')
  const stringIV = stringIVKey.substring(0, stringIVKey.length / 2)
  const stringKey = stringIVKey.substring(
    stringIVKey.length / 2,
    stringIVKey.length
  )

  const iv = new Buffer(stringIV, 'hex')
  const key = new Buffer(stringKey, 'hex')
  const cipher = crypto.createCipheriv('aes-128-cbc', key, iv)
  return cipher.update(data, 'utf8', 'base64') + cipher.final('base64')
}

export function decrypt(data: string, ivKey: Buffer): string {
  const iv = ivKey.slice(0, ivKey.length / 2)
  const key = ivKey.slice(ivKey.length / 2, ivKey.length)

  const cipher = crypto.createDecipheriv('aes-128-cbc', key, iv)

  return Buffer.concat([
    cipher.update(data, 'base64'),
    cipher.final()
  ]).toString()
}