defmodule Liaison.Application do
  @moduledoc false

  @ type child :: pid | :undefined
  @type on_start_child ::
    {:ok, child}
    | {:ok, child, info :: term}
    | {:error, {:already_started, child} | :already_present | term}


  defp sup_name(), do: Liaison.Supervisor

  @spec start(any, any) :: {:error, any} | {:ok, pid}
  def start(_type, _args) do
    children = strategies()

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

  defp strategies() do
    Application.get_env(:liaison, :strategies, [])
    |> Enum.reduce(%{}, fn strat_config, acc ->
      Map.put(acc, strat_config[:strategy], strat_config)
    end)
    |> Map.to_list()
  end

  defp strategy_to_child(strat_config) do
    {strat_config[:strategy], strat_config}
  end

  @spec add_child(list()) :: on_start_child
  def add_child(strat_config) do
    child =
      strat_config
      |> strategy_to_child()

    Supervisor.start_child(sup_name(), child)
  end
end