#!/usr/bin/python3
"""
This module provides the Dice class (formula based random numbers)
"""
import sys
from random import randint


class Dice(object):
    """
    This class supports formula based dice rolls.
    The formulae can be described in a few (fairly standard) formats:
        - DnD style ... D100, 3D6, 3D6+4
        - ranges ... 4-12
        - simple numbers ... 50

    @ivar num_dice: (int) number of dice to be rolled, None if a range
    @ivar dice_type: (int) number of faces on each die, None if a range
    @ivar plus: (int) number to be added to the roll
    @ivar min_value: (int) lowest legal value in range, None if a formula
    @ivar max_value: (int) highest legal value range, None if a formula
    """

    def __init__(self, formula):
        """
        instantiate a roller for a specified formula

        @param formula: (string) description of roll
        @raise ValueError: illegal formula expression
        """
        # formula must be a string (or integer)
        # if it is just a number, this is simple
        # figure out what kind of expression this is
        # see if it has known form and 2 values
        # process the values
                # there might be a plus after the dice type

    def str(self):
        """
        return string representation of these dice"
        """

    def roll(self):
        """
        roll this set of dice and return result
        @return: (int) resulting value
        """