defmodule Cap.Crypto do
  @doc """
  Encrypt data

   ## Example

       encrypt("example test")
  """
  def encrypt(data) do
    key = Application.get_env(:cap, :secret_key)
    iv = :crypto.strong_rand_bytes(32)
    {ct, tag} = :crypto.block_encrypt(:aes_gcm, key, iv, {"AES128GCM", data})
    Base.encode64(iv <> tag <> ct)
  end

  @doc """
  Decrypt data

   ## Example

       decrypt("ZV05qWlhOekluMC5rTnVZVnZpOEQ1bUc3N0FvWmdHdWhCc0NXX2luLTNEWE==")
  """
  def decrypt(cipher) do
    key = Application.get_env(:cap, :secret_key)
    <<iv::binary-32, tag::binary-16, ct::binary>> = Base.decode64!(cipher)
    :crypto.block_decrypt(:aes_gcm, key, iv, {"AES128GCM", ct, tag})
  end

  def encrypt_sha(data) do
    key = Application.get_env(:cap, :secret_key)

    :crypto.mac(:hmac, :sha256, key, data)
    |> Base.encode64(padding: false)
  end

  def verify_sha(data, hash) do
    key = Application.get_env(:cap, :secret_key)

    hmac =
      :crypto.mac(:hmac, :sha256, key, data)
      |> Base.encode64(padding: false)

    hmac == hash
  end
end