railyard

defmodule Railyard.Dsl do
  @moduledoc """
  Use `Railyard.Dsl` in a module to turn it into a **resource module**.
  """
  defmacro __using__(_opts \\ []) do
    quote do
      require Railyard.Util.BlockMap
      require Railyard.Dsl
      import Railyard.Dsl, only: [resource: 3, resource: 4]

      @dsl_resources %{}
      @ship_before []
      @ship_after []

      @before_compile Railyard.Dsl

      :ok
    end
  end

  defmacro __before_compile__(_env) do
    quote do
      def ship(bindings) do
        before_results =
          @ship_before
          |> Enum.map(fn mod -> {mod, apply(mod, :ship, bindings)} end)

        results =
          @dsl_resources
          |> Enum.reject(fn {_rc_name, rc} ->
            case Railyard.ResourceSpec.eval_property(rc, :skip_if, bindings) do
              {:skip_if, value} -> true
              _ -> false
            end
          end)
          |> Enum.map(fn {_k, v} -> v end)
          |> Railyard.ship(bindings)

        after_results =
          @ship_after
          |> Enum.map(fn mod -> {mod, apply(mod, :ship, bindings)} end)
      end
    end
  end

  @doc """
  Defines a **resource spec** within the module.

  Name
  """
  defmacro resource(name, type, attributes_or_block, block_if_no_attributes \\ nil) do
    unnamed_resource =
      build_resource_spec(
        name,
        type,
        attributes_or_block,
        block_if_no_attributes
      )

    quote do
      @dsl_resources Map.put(
                       @dsl_resources,
                       unquote(name),
                       %Railyard.ResourceSpec{
                         unquote(unnamed_resource)
                         | module: __MODULE__
                       }
                     )

      def unquote(name)() do
        Map.get(@dsl_resources, unquote(name))
      end
    end
  end

  defmacro ship_before(module) do
    quote do
      @ship_before [module | @ship_before]
    end
  end

  defmacro ship_after(module) do
    quote do
      @ship_after [module | @ship_after]
    end
  end

  defp build_resource_spec(name, type, attributes, do: block) do
    quote do
      %Railyard.ResourceSpec{
        name: unquote(name),
        type: unquote(type),
        attributes: unquote(attributes),
        block: Railyard.Util.BlockMap.create_block(do: unquote(block))
      }
    end
  end

  defp build_resource_spec(name, type, [do: block], nil) do
    quote do
      %Railyard.ResourceSpec{
        name: unquote(name),
        type: unquote(type),
        attributes: [],
        block: Railyard.Util.BlockMap.create_block(do: unquote(block))
      }
    end
  end
end