rollex

defmodule Rollex do
  # NOTE: Order Matters! If an item matches in Rollex.Lexer._do_tokenize/0, the lexer will skip the rest of the tokens
  # This is why number is after dice tokens, since number will very frequently match on what should be dice input
  @default_tokens [%Rollex.Tokens.Division{},
                    %Rollex.Tokens.Multiplication{},
                    %Rollex.Tokens.Subtraction{},
                    %Rollex.Tokens.Addition{},
                    %Rollex.Tokens.TakeTopDice{},
                    %Rollex.Tokens.TakeBottomDice{},
                    %Rollex.Tokens.RegularDice{},
                    %Rollex.Tokens.Number{},
                    %Rollex.Tokens.LeftParenthesis{},
                    %Rollex.Tokens.RightParenthesis{}]

  # Use built-in defaults
  def roll(roll_expr, options \\ [token_list: @default_tokens, lexer: Rollex.Lexer, validator: Rollex.Validator, evaluator: Rollex.Evaluator])
  def roll(roll_expr, options) when is_list(options) do
    _roll(roll_expr, options)
  end

  defp _roll(roll_expr, options) do
    {:ok, roll_expr}
    |> _apply_roll_step(options[:lexer], :tokenize, options[:token_list])
    |> _apply_roll_step(options[:validator], :validate)
    |> _apply_roll_step(options[:evaluator], :evaluate)
    |> _build_final_output(roll_expr)
  end

  defp _apply_roll_step(input, module, function_atom, additional_options \\ [])
  defp _apply_roll_step(input, module, function_atom, additional_options) when is_atom(function_atom) and is_list(additional_options) do
    apply(module, function_atom, [input | [additional_options]])
  end
  defp _apply_roll_step({:error, _error_msg} = input, _module, _function_atom, _additional_options) do
    input
  end

  defp _build_final_output({:error, %{} = result}, input_roll_string) do
    %{status: :error, error_msg: result.error_msg, raw_input: input_roll_string}
  end
  defp _build_final_output({:ok, %{} = result}, input_roll_string) do
    %{status: :ok, total: result.total, tokenized_input: result.tokenized_input, raw_input: input_roll_string}
  end
  defp _build_final_output({:error, msg}, input_roll_string) when is_binary(msg) do
    %{status: :error, error_msg: msg, tokenized_input: [], raw_input: input_roll_string}
  end
end