defmodule Credo.Code.TokenAstCorrelation do
  if Version.match?(System.version(), ">= 1.6.0-rc") do
    # Elixir >= 1.6.0
    def find_tokens_in_ast(wanted_token, ast) do
      Credo.Code.prewalk(ast, &traverse_ast_for_token(&1, &2, wanted_token))
    end

    defp traverse_ast_for_token({:., meta, arguments} = ast, acc, token)
         when is_list(arguments) do
      {line_no_start, col_start, _line_no_end, _col_end} = Credo.Code.Token.position(token)

      if meta[:line] == line_no_start && meta[:column] == col_start - 1 do
        {nil, acc ++ [ast]}
      else
        {ast, acc}
      end
    end

    defp traverse_ast_for_token({_name, meta, _arguments} = ast, acc, token) do
      {line_no_start, col_start, _line_no_end, _col_end} = Credo.Code.Token.position(token)

      if meta[:line] == line_no_start && meta[:column] == col_start do
        {nil, acc ++ [ast]}
      else
        {ast, acc}
      end
    end

    defp traverse_ast_for_token(ast, acc, _token) do
      {ast, acc}
    end
  else
    # Elixir <= 1.5.x
    def find_tokens_in_ast(_wanted_token, _ast) do
      nil
    end
  end
end