defmodule ExUrlbox.Config do
  @moduledoc """
  Retrieve config variables that are used with Urlbox's API.

  All settings also accept `{:system, "ENV_VAR_NAME"}` to read their
  values from environment variables at runtime.

  """

  # Config pattern inspired from https://github.com/danielberkompas/ex_twilio

  @doc """
    Returns the default API endpoint. Used with POST requests
  """
  def base_endpoint, do: "https://api.urlbox.io/v1/"

  @doc """
  Returns the *URLBOX_API_KEY*
      config :ex_urlbox, api_key: "URLBOX_API_KEY"
  """
  def api_key, do: from_env(:ex_urlbox, :api_key)

  @doc """
  Returns the *URLBOX_API_SECRET*
      config :ex_urlbox, api_secret: "URLBOX_API_SECRET"
  """
  def api_secret, do: from_env(:ex_urlbox, :api_secret)

  @doc """
  Returns the API endpoint with api_key for the following HTTP methods: GET, DELETE, HEAD
  """
  def api_key_endpoint, do: base_endpoint() <> api_key()

  @doc """
    Urlbox's API path for POST requests
  """
  def api_post_endpoint, do: "render"


  @doc """
  A light wrapper around `Application.get_env/2`, providing automatic support for
  `{:system, "VAR"}` tuples.
  """
  def from_env(otp_app, key, default \\ nil)

  def from_env(otp_app, key, default) do
    otp_app
    |> Application.get_env(key, default)
    |> read_from_system(default)
  end

  defp read_from_system({:system, env}, default), do: System.get_env(env) || default
  defp read_from_system(value, _default), do: value


  # Determine the Tesla adapter to use
  @doc """
  Returns the appropriate Tesla adapter based on the environment.
  In test environment, returns Tesla.Mock.
  In other environments, returns the configured adapter or defaults to Hackney.
  """
  def get_client_adapter(opts \\ []) do
    env = Application.get_env(:ex_urlbox, :env, :prod)

    case env do
      :test -> Tesla.Mock
      _ -> {Application.get_env(:tesla, ExUrlbox, [])[:adapter] || Tesla.Adapter.Hackney, opts}
    end
  end

end