defmodule Mix.Tasks.Nebulex.Gen.Cache do
  use Mix.Task

  import Mix.Nebulex
  import Mix.Generator

  alias Mix.Project

  @shortdoc "Generates a new cache"

  @moduledoc """
  Generates a new cache.

  The cache will be placed in the `lib` directory.

  ## Examples

      mix nebulex.gen.cache -c Custom.Cache -a Nebulex.Adapters.Local

  ## Command line options

    * `-c`, `--cache` - the cache to generate
    * `-a`, `--adapter` - the cache adapter to use (optional)
  """

  @doc false
  def run(args) do
    no_umbrella!("nebulex.gen.cache")
    switches = [cache: :atom, adapter: :adapter]
    aliases = [c: :cache, a: :adapter]

    {parsed, _, _} = OptionParser.parse(args, switches: switches, aliases: aliases)

    unless cache = parsed[:cache] do
      Mix.raise("""
      nebulex.gen.cache expects the cache to be given as -c MyApp.Cache,
      for example:

          mix nebulex.gen.cache -c MyApp.Cache

      To specify other adapter different than default, use -a option:

          mix nebulex.gen.cache -c MyApp.Cache -a Nebulex.Adapters.Partitioned
      """)
    end

    cache = Module.concat([cache])
    adapter = Module.concat([parsed[:adapter] || Nebulex.Adapters.Local])

    config = Project.config()
    underscored = Macro.underscore(inspect(cache))

    base = Path.basename(underscored)
    file = Path.join("lib", underscored) <> ".ex"
    app = config[:app] || :YOUR_APP_NAME
    opts = %{mod: cache, adapter: adapter, app: app, base: base}

    create_directory(Path.dirname(file))
    create_file(file, cache_template(opts))

    case File.read("config/config.exs") do
      {:ok, contents} ->
        Mix.shell().info([:green, "* updating ", :reset, "config/config.exs"])

        File.write!(
          "config/config.exs",
          String.replace(contents, "use Mix.Config", config_template(opts))
        )

      {:error, _} ->
        create_file("config/config.exs", config_template(opts))
    end

    Mix.shell().info("""
    Don't forget to add your new cache to your supervision tree
    (typically in lib/#{app}/application.ex):

        # For Elixir v1.5 and later
        {#{inspect(cache)}, []}

        # For Elixir v1.4 and earlier
        supervisor(#{inspect(cache)}, [])

    And for more information about cache config options, check the adapter
    documentation and Nebulex.Cache shared options.
    """)
  end

  defp config_template(opts) do
    case opts[:adapter] do
      Nebulex.Adapters.Local ->
        local_config_template(opts)

      Nebulex.Adapters.Partitioned ->
        partitioned_config_template(opts)

      Nebulex.Adapters.Multilevel ->
        multilevel_config_template(opts)

      _ ->
        local_config_template(opts)
    end
  end

  embed_template(:cache, """
  defmodule <%= inspect @mod %> do
    use Nebulex.Cache,
      otp_app: <%= inspect @app %>,
      adapter: <%= inspect @adapter %>
  end
  """)

  embed_template(:local_config, """
  use Mix.Config

  config <%= inspect @app %>, <%= inspect @mod %>,
    gc_interval: 86_400 # 24 hrs
  """)

  embed_template(:partitioned_config, """
  use Mix.Config

  config <%= inspect @app %>, <%= inspect @mod %>,
    primary: :YOUR_LOCAL_CACHE
  """)

  embed_template(:multilevel_config, """
  use Mix.Config

  config <%= inspect @app %>, <%= inspect @mod %>,
    cache_model: :inclusive,
    levels: []
  """)
end