defmodule MBU.BuildTask do
  @moduledoc """
  BuildTask contains the macros that are used for making the tasks look nicer.
  """

  @doc """
  Sets up the necessary things for a build task.

  Each build task should have `use MBU.BuildTask` at its beginning. BuildTask automatically
  imports Mix.Task and Logger so they don't need to be added into the task itself.

  The following options may be passed to the use clause:

  - `:auto_path`: Set to `true` to autogenerate an `out_path/0` function for this task. Default:
    `false`. Overrides the `:auto_paths` config.
  - `:create_out_path`: Set to `true` to create the output path specified by `out_path/0` when the
    task is started. Default: `false`. Overrides the `:create_out_paths` config.
  """
  defmacro __using__(opts \\ []) do
    quote do
      use Mix.Task
      require Logger

      import MBU.BuildTask

      # Dependencies of the task that will be automatically run before it
      @deps []

      @create_out_path Keyword.get(unquote(opts), :create_out_path, nil)

      auto_path = Keyword.get(unquote(opts), :auto_path, nil)

      if auto_path || (Application.get_env(:mbu, :auto_paths, false) and auto_path == nil) do
        def out_path() do
          Path.join([tmp_path(), Mix.Task.task_name(__MODULE__)])
        end

        defp tmp_path() do
          # Get temporary directory or raise error
          case Application.get_env(:mbu, :tmp_path) do
            nil ->
              raise "MBU must be configured with a directory to put temporary files in if automatic "
              "directory handling is used! Use the `:tmp_path` key to set a desired path."

            path ->
              path
          end
        end
      end
    end
  end

  @doc """
  Replacement for Mix.Task's run/1, used similarly. Code inside will be run when the task
  is called, with @deps being run first unless `deps: false` is given in the arguments.
  """
  defmacro task(args, do: block) do
    quote do
      def run(unquote(args) = mbu_buildtask_args) do
        task = Mix.Task.task_name(__MODULE__)
        Logger.info("[#{task}] Started")

        if @create_out_path ||
             (Application.get_env(:mbu, :create_out_paths, false) and @create_out_path == nil) do
          op = apply(__MODULE__, :out_path, [])
          Logger.info("[#{task}] Creating output path #{op}...")
          :ok = File.mkdir_p!(op)
        end

        if Keyword.get(mbu_buildtask_args, :deps, true) and not Enum.empty?(@deps) do
          MBU.TaskUtils.run_tasks(@deps)
        end

        unquote(block)

        Logger.info("[#{task}] Finished")
      end
    end
  end
end