comeonin_crypt.ex

defmodule Comeonin.Crypt do
  use Agent

  @callback check_pass(map(), String.t()) :: {:ok, map()} | {:error, String.t()}
  @callback hashpwsalt(String.t(), Keyword.t()) :: String.t()
  @callback checkpw(String.t(), String.t()) :: boolean()
  @callback dummy_checkpw(Keyword.t()) :: false
  @callback add_hash(String.t(), Keyword.t()) :: map()
  @callback can_verify_hash(String.t()) :: boolean()
  @callback needs_rehash(String.t(), Keyword.t()) :: boolean()

  @spec flatten([[arg]]) :: [arg] when arg: var
  defp flatten([]), do: []
  defp flatten([h|t]), do: h ++ flatten(t)
  defp flatten(h), do: h

  defmacro __using__(_opts) do
    module = Module.concat([__MODULE__, Auto, __CALLER__.module])
    quote do
      @behaviour unquote(__MODULE__)
      defmodule unquote(module) do
        def module, do: (unquote(__CALLER__.module))
      end
    end
  end

  @spec find_implementors() :: list(module())
  def find_implementors do
    pid = Process.whereis(__MODULE__)

    if pid do
      Agent.get(pid, &(&1))
    else
      {:ok, p} = Agent.start_link(&_find_implementors/0, name: __MODULE__)
      Agent.get(p, &(&1))
    end
  end

  @spec _find_implementors() :: list(module())
  defp _find_implementors do
    auto_prefix = to_string(Module.concat([__MODULE__, Auto]))
    :application.loaded_applications()
    |> Enum.map(&(elem(&1, 0) |> Application.spec(:modules)))
    |> flatten
    |> Enum.filter(&(to_string(&1) |> String.starts_with?(auto_prefix)))
    |> Enum.map(&(&1.module))
  end
end