Twilio signature module

twilio_signature.ex

defmodule TwilioSignature do
  @moduledoc """
  Twilio signatures module.
  """

  @doc """
  Generate the Twilio signature from a request.

  See: https://www.twilio.com/docs/usage/security#validating-requests

  ## Example

      iex> url = "https://mycompany.com/myapp.php?foo=1&bar=2"
      iex> params = %{
      ...>   "CallSid" => "CA1234567890ABCDE",
      ...>   "From" => "+12349013030",
      ...>   "To" => "+18005551212",
      ...>   "Caller" => "+12349013030",
      ...>   "Digits" => "1234"
      ...> }
      iex> TwilioSignature.generate(url, params, "12345")
      "0/KCTR6DLpKmkAf8muzZqo1nDgQ="
      
  """
  @spec generate(String.t(), map(), String.t()) :: String.t()
  def generate(url, params, secret) do
    sorted_params_iolist =
      params
      |> Enum.sort_by(fn {k, v} -> [k, v] end)
      |> List.flatten()

    [url | sorted_params_iolist]
    |> then(&:crypto.mac(:hmac, :sha, secret, &1))
    |> Base.encode64()
  end
end