defmodule JuliaPort.GenFunction do
  @moduledoc """
  extensible interface of julia function definition in elixir using macro 
  """

  @doc ~S"""
  the macro to define functions with dynamic name and arity 
  """
  defmacro __using__(opts) do
    Enum.map(opts, fn {name, arity} ->
      args = Enum.map(0..arity+1, &Macro.var(:"a#{&1}", __MODULE__))
      quote do
        @doc """
        helper function defined in GenFunction
        """
        def unquote(name)(unquote_splicing(args)) do
          [a0 | [ a1 | args ]] = [unquote_splicing(args)]
          s1 = 
            cond do
              is_tuple(a1) ->
                "(" <> (Tuple.to_list(a1) |> Enum.map(&(to_string(&1))) |> Enum.join(",")) <> ")"
              true ->
                to_string(a1)
            end
          s2 = "=#{unquote(name)}("
          s3 = 
            case unquote(arity) do
              0 -> ""
              _ -> 
                args
                |> Enum.map(fn arg -> 
                    cond do
                      is_list(arg) ->
                        "[" <> (Enum.map(arg, &(to_string(&1))) |> Enum.join(",")) <> "]"
                      is_bitstring(arg) ->
                        "\"" <> arg <> "\""
                      true -> 
                        to_string(arg)                    
                    end
                  end) 
                |> Enum.join(",")
            end
          s4 = ")"
          s = s1 <> s2 <> s3 <> s4
          send a0, {self(), {:command, s <> "\n"}}
        end
      end
    end)
  end
end