Top Secret

	defmodule TopSecret do
	  def to_ast(string) do
		# Please implement the to_ast/1 function
		{_,result}=Code.string_to_quoted(string)
		result
	  end

	  def get_function(function_name) do   
		tuple= List.first(function_name)
		params = elem(tuple, 2)
		result= tuple
		|> elem(0)
		|> to_string

		case result do
		  "when" -> guards(params) |> num_letter(params)
		  _ -> if params == [] or params == nil, do: "", else: String.slice(result, 0, length(params))
		end
	  end

	  def num_letter(value, params) do
		len = if String.last(value) != "?", do: 1 , else: length(params)
		String.slice(value,0, len)
	  end
	  def guards(params) do
		List.first(params)
		|> elem(0)
		|> to_string
	  end
	  def decode_secret_message_part({op,_,function_name}= ast_node, accumulator)when op in [:def, :defp] do
		# Please implement the decode_secret_message_part/2 function
		{ast_node, [get_function(function_name) | accumulator]}
	  end
	  def decode_secret_message_part(ast_node, accumulator) do
		# Please implement the decode_secret_message_part/2 function
			{ast_node, accumulator}

	  end

	  def decode_secret_message(string) do
		# Please implement the decode_secret_message/1 function
		ast = to_ast(string)
		{new_ast, result} = Macro.prewalk(ast, [], fn ast_node,accumulator ->
		  decode_secret_message_part(ast_node,accumulator)
		end)

		result|> Enum.reverse |> Enum.join()
	  end
	end