defmodule Mix.Tasks.Elmer.New do
  @shortdoc "Creates new elm applications"
  @moduledoc """
  This is a mix task for creating new elm applications.
  """

  use Mix.Task

  @doc """
  Creates a new elm application in directory specified by the user.

  Run with `mix elmer.new`

  Different types of apps can be generated:

  * Beginner (http://package.elm-lang.org/packages/elm-lang/html/1.0.0/Html-App#beginnerProgram) which generates:
      * Main.elm
      * elm-package.json
  * HTML (http://package.elm-lang.org/packages/elm-lang/html/1.0.0/Html-App#program) which generates:
      * Main.elm
      * Models.elm
      * Msgs.elm
      * Update.elm
      * View.elm
      * elm-package.json
  * Navigation (http://package.elm-lang.org/packages/elm-lang/navigation/1.0.0/Navigation#program) which generates:
      * Main.elm
      * Models.elm
      * Msgs.elm
      * Ports.elm
      * RouteMsgs.elm
      * Routing.Elm
      * Update.elm
      * View.elm
      * elm-package.json
  * Hop (https://github.com/sporto/hop) which generates:
      * Main.elm
      * Models.elm
      * Msgs.elm
      * Ports.elm
      * RouteMsgs.elm
      * Routing.Elm
      * Update.elm
      * View.elm
      * elm-package.json

  These types correspond to the main types of elm programs.


  """
  def run(_args) do
    Mix.shell.info "Creating new elm app..."

    # Get the path to their app
    app_path = Elmer.prompt_path

    # Make the folder if it doesn't already exist
    case File.mkdir(Path.expand(app_path)) do
      :ok ->
        # Get what type of app this is
        app_type = Mix.shell.prompt("What type of application is this?\n(B)eginner\n(H)TML\n(N)avigation\n(Ho)p\n|>")

        # Write the default Main files based on the app type
        create_main(app_path, app_type)

        Mix.shell.info "App created in #{app_path}"
      {:error, :eexist} -> Mix.shell.info "App directory already exists"
      err -> Mix.shell.error err
    end
  end

  # Copies over the specific type of file into our app_path
  defp create_main(path, type) do
    # Downcase the type to avoid inconsistencies
    type = String.downcase(type) |> String.strip

    # Map of the available templates
    templates = %{
      "b" => [{&Elmer.Templates.Beginner.render_main/0, "Main.elm"},
              {&Elmer.Templates.Beginner.render_package_json/0, "elm-package.json"}
             ],
      "h" => [{&Elmer.Templates.Html.render_main/0, "Main.elm"},
              {&Elmer.Templates.Html.render_models/0, "Models.elm"},
              {&Elmer.Templates.Html.render_msgs/0, "Msgs.elm"},
              {&Elmer.Templates.Html.render_view/0, "View.elm"},
              {&Elmer.Templates.Html.render_update/0, "Update.elm"},
              {&Elmer.Templates.Html.render_package_json/0, "elm-package.json"}
             ],
      "n" => [{&Elmer.Templates.Navigation.render_main/0, "Main.elm"},
              {&Elmer.Templates.Navigation.render_models/0, "Models.elm"},
              {&Elmer.Templates.Navigation.render_msgs/0, "Msgs.elm"},
              {&Elmer.Templates.Navigation.render_ports/0, "Ports.elm"},
              {&Elmer.Templates.Navigation.render_routemsgs/0, "RouteMsgs.elm"},
              {&Elmer.Templates.Navigation.render_routing/0, "Routing.elm"},
              {&Elmer.Templates.Navigation.render_update/0, "Update.elm"},
              {&Elmer.Templates.Navigation.render_view/0, "View.elm"},
              {&Elmer.Templates.Navigation.render_package_json/0, "elm-package.json"}
             ],
      "ho" => [{&Elmer.Templates.Hop.render_main/0, "Main.elm"},
              {&Elmer.Templates.Hop.render_models/0, "Models.elm"},
              {&Elmer.Templates.Hop.render_msgs/0, "Msgs.elm"},
              {&Elmer.Templates.Hop.render_ports/0, "Ports.elm"},
              {&Elmer.Templates.Hop.render_routemsgs/0, "RouteMsgs.elm"},
              {&Elmer.Templates.Hop.render_routing/0, "Routing.elm"},
              {&Elmer.Templates.Hop.render_update/0, "Update.elm"},
              {&Elmer.Templates.Hop.render_view/0, "View.elm"},
              {&Elmer.Templates.Hop.render_package_json/0, "elm-package.json"}
             ]
    }

    # Write the template to our app dir
    Enum.each templates[type], fn({template, filename}) ->
      contents = template.()
      Mix.Generator.create_file("#{path}/#{filename}", contents)
    end
  end
end