zepto

defmodule Zepto.Application do
  @moduledoc """
  The Zepto Application module.

  Starts and supervises TokenManager processes for each configured environment.
  Optionally starts the Mock Server when configured.
  """

  use Application

  alias Zepto.Client.TokenManager

  @impl true
  def start(_type, _args) do
    children = build_children()

    opts = [strategy: :one_for_one, name: Zepto.Supervisor]
    Supervisor.start_link(children, opts)
  end

  defp build_children do
    token_managers = build_token_managers()
    mock_server = maybe_mock_server()

    token_managers ++ mock_server
  end

  defp build_token_managers do
    environments = Application.get_env(:zepto, :environments, [])

    Enum.map(environments, fn {env_name, env_config} ->
      token_manager_name = token_manager_name(env_name)

      Supervisor.child_spec(
        {TokenManager,
         [
           name: token_manager_name,
           environment: env_name,
           oauth_url: env_config[:oauth_url],
           client_id: env_config[:client_id],
           client_secret: env_config[:client_secret],
           token_callback: env_config[:token_callback]
         ]},
        id: token_manager_name
      )
    end)
  end

  defp maybe_mock_server do
    mock_config = Application.get_env(:zepto, :mock_server, [])

    if mock_config[:enabled] && mock_config[:repo] do
      [Zepto.MockServer.Supervisor]
    else
      []
    end
  end

  @doc """
  Returns the TokenManager process name for a given environment.

  ## Examples

      iex> Zepto.Application.token_manager_name(:sandbox)
      Zepto.TokenManager.Sandbox

      iex> Zepto.Application.token_manager_name(:prod)
      Zepto.TokenManager.Prod
  """
  @spec token_manager_name(atom()) :: atom()
  def token_manager_name(environment) when is_atom(environment) do
    env_string =
      environment
      |> Atom.to_string()
      |> String.split("_")
      |> Enum.map(&String.capitalize/1)
      |> Enum.join("")

    Module.concat(Zepto.TokenManager, env_string)
  end
end