defmodule Mix.Tasks.Phx.Custom.Web do
  @shortdoc "Patch project with custom Web template"

  @moduledoc """
  #{@shortdoc}.

      mix phx.custom.web <project>

  """

  use Mix.Task

  alias PhxCustom.Web

  @impl Mix.Task
  def run(args) do
    parse_args(args)
    |> validate
    |> process
  end

  def parse_args(args) do
    OptionParser.parse(args, strict: [])
    |> elem(1)
    |> args_to_internal_representation()
  end

  defp args_to_internal_representation([project_root]) do
    {project_root}
  end

  defp args_to_internal_representation(_) do
    :help
  end

  defp validate(args) do
    args
    |> validate_project_root
  end

  defp validate_project_root({project_root} = args) do
    case File.lstat(project_root) do
      {:ok, %File.Stat{type: :directory}} ->
        args

      _ ->
        IO.puts("invalid project root.\n")
        System.halt(0)
    end
  end

  def process({project_root}) do
    root = Path.expand(project_root, File.cwd!())

    Web.patch(root)
  end
end