relation

defmodule Mix.Tasks.Gen.Json do
  use Mix.Task

  @shortdoc "Generates a controller and model for a JSON based resource"

  @moduledoc """
  Generates a Phoenix resource.

      mix phoenix.gen.json User users name:string age:integer

  The first argument is the module name followed by
  its plural name (used for resources and schema).

  The generated resource will contain:

    * a schema in web/models
    * a view in web/views
    * a controller in web/controllers
    * a migration file for the repository
    * test files for generated model and controller

  If you already have a model, the generated model can be skipped
  with `--no-model`. Read the documentation for `phoenix.gen.model`
  for more information on attributes and namespaced resources.
  """
  def run(args) do
    switches = [binary_id: :boolean, model: :boolean]

    {opts, parsed, _} = OptionParser.parse(args, switches: switches)
    [singular, plural | attrs] = validate_args!(parsed)

    default_opts = Application.get_env(:phoenix, :generators, [])
    opts = Keyword.merge(default_opts, opts)

    attrs   = Mix.Phoenix.attrs(attrs) ++ [inserted_at: :naive_datetime, updated_at: :naive_datetime]
    IO.inspect attrs
    binding = Mix.Phoenix.inflect(singular)
    path    = binding[:path]
    route   = String.split(path, "/") |> Enum.drop(-1) |> Kernel.++([plural]) |> Enum.join("/")
    binding = binding ++ [plural: plural, route: route,
                          sample_id: sample_id(opts),
                          attrs: attrs, params: Mix.Phoenix.params(attrs)]

    # Mix.Phoenix.check_module_name_availability!(binding[:module] <> "Controller")
    # Mix.Phoenix.check_module_name_availability!(binding[:module] <> "View")

    files = [
      # {:eex, "controller.ex",       "web/controllers/#{path}_controller.ex"},
      {:eex, "view.ex",             "web/views/#{path}_view.ex"},
      # {:eex, "controller_test.exs", "test/controllers/#{path}_controller_test.exs"},
    ] ++ changeset_view()

    Gen.Phoenix.copy_from paths(), "priv/templates/gen.json", "", binding, files

    instructions = """

    Add the resource to your api scope in web/router.ex:

        resources "/#{route}", #{binding[:scoped]}Controller, except: [:new, :edit]
    """

    if opts[:model] != false do
      Mix.Task.run "phoenix.gen.model", ["--instructions", instructions|args]
    else
      Mix.shell.info instructions
    end
  end

  defp sample_id(opts) do
    if Keyword.get(opts, :binary_id, false) do
      Keyword.get(opts, :sample_binary_id, "11111111-1111-1111-1111-111111111111")
    else
      -1
    end
  end

  defp changeset_view do
    if File.exists?("web/views/changeset_view.ex") do
      []
    else
      [{:eex, "changeset_view.ex", "web/views/changeset_view.ex"}]
    end
  end

  defp validate_args!([_, plural | _] = args) do
    cond do
      String.contains?(plural, ":") ->
        raise_with_help()
      plural != Phoenix.Naming.underscore(plural) ->
        Mix.raise "Expected the second argument, #{inspect plural}, to be all lowercase using snake_case convention"
      true ->
        args
    end
  end

  defp validate_args!(_) do
    raise_with_help()
  end

  @spec raise_with_help() :: no_return()
  defp raise_with_help do
    Mix.raise """
    mix phoenix.gen.json expects both singular and plural names
    of the generated resource followed by any number of attributes:

        mix phoenix.gen.json User users name:string
    """
  end

  defp paths do
    [".", :phoenix]
  end
end