telegex_plug

defmodule Telegex.Plug.Presets.Commander do
  @moduledoc """
  Command processing plug-in.
  """

  @typedoc "Match results."
  @type match_result :: {:match | :nomatch, Telegex.Plug.state()}

  defmacro __using__(command) when is_atom(command) do
    quote do
      use Telegex.Plug

      @behaviour Telegex.Plug.Presets.Commander
      @command "/#{unquote(command)}"

      @impl true
      def __preset__, do: :commander

      unquote(def_match())
      unquote(def_ignore_calls())

      @impl true
      def call(%{message: %{text: text} = message} = _update, state) do
        case match(text, state) do
          {:match, state} ->
            handle(message, state)

          {:nomatch, state} ->
            {:ignored, state}
        end
      end

      defoverridable match: 2
    end
  end

  defp def_match do
    quote do
      @impl true
      def match(text, state) do
        if text == @command || text == "#{@command}@#{Telegex.Plug.get_usename()}" do
          {:match, state}
        else
          {:nomatch, state}
        end
      end
    end
  end

  defp def_ignore_calls do
    quote do
      @impl true
      def call(%{message: nil} = _update, state), do: {:ignored, state}

      @impl true
      def call(%{message: %{text: nil}} = _update, state), do: {:ignored, state}
    end
  end

  @doc """
  Match commands.

  This function can be automatically generated by `use` this module.
  """
  @callback match(text :: String.t(), state :: Telegex.Plug.state()) :: match_result()

  @doc """
  Handle commands.
  """
  @callback handle(message :: Telegex.Model.Message.t(), state :: Telegex.Plug.state()) ::
              Telegex.Plug.stateful()
end