defmodule Protobuf.Protoc.CLI do
  def main(_) do
    # https://groups.google.com/forum/#!topic/elixir-lang-talk/T5enez_BBTI
    :io.setopts(:standard_io, encoding: :latin1)
    bin = IO.binread(:all)
    request = Protobuf.Decoder.decode(bin, Google.Protobuf.Compiler.CodeGeneratorRequest)

    namespace = System.get_env("PROTO_NAMESPACE")

    ctx =
      if namespace != nil do
        %Protobuf.Protoc.Context{custom_namespace: [namespace]}
      else
        %Protobuf.Protoc.Context{}
      end

    ctx = parse_params(ctx, request.parameter)
    ctx = find_package_names(ctx, request.proto_file)

    files =
      request.proto_file
      |> Enum.filter(fn desc -> Enum.member?(request.file_to_generate, desc.name) end)
      |> Enum.map(fn desc -> Protobuf.Protoc.Generator.generate(ctx, desc) end)

    response = Google.Protobuf.Compiler.CodeGeneratorResponse.new(file: files)

    IO.binwrite(Protobuf.Encoder.encode(response))
  end

  def parse_params(ctx, params_str) when is_binary(params_str) do
    params = String.split(params_str, ",")
    parse_params(ctx, params)
  end

  def parse_params(ctx, ["plugins=" <> plugins | t]) do
    plugins = String.split(plugins, "+")
    ctx = %{ctx | plugins: plugins}
    parse_params(ctx, t)
  end

  def parse_params(ctx, _), do: ctx

  defp find_package_names(ctx, descs) do
    find_package_names(ctx, descs, %{})
  end

  defp find_package_names(ctx, [], acc), do: %{ctx | pkg_mapping: acc}

  defp find_package_names(ctx, [desc | t], acc) do
    find_package_names(ctx, t, Map.put(acc, desc.name, desc.package))
  end
end