import pyparsing
import math
import operator
import numpy as np

from pyparsing import (
    Literal,
    CaselessLiteral,
    Word,
    Optional,
    Group,
    Forward,
    nums,
    ParseException,
)


class Dice:

    exprStack = []

    def __init__(self):
        pass

    def roll(self, roll_params):
        self.exprStack[:] = []  # Reset the stack
        try:
            results = self.BNF().parseString(roll_params, parseAll=True)
        except ParseException as pe:
            print("Parse exception ", str(pe))
            return
        except Exception as e:
            print("Exception ", str(e), self.exprStack)

        return results

    def push_first(self, tokens):
        self.exprStack.append(tokens[0])

    def BNF(self):

        integer = Word(nums)
        plus, minus = map(Literal, "+-")

        addop = plus | minus
        rollop = CaselessLiteral('d')
        # lowop = CaselessLiteral('l')
        # highop = CaselessLiteral('h')

        # Define roll as a group
        roll = Group(Optional(integer, default=1) + rollop + integer)

        expression = Forward()

        operand = (
                addop[...]
                + (
                    # Numbers as a fallback, add everything else as (roll | exception | ...)
                    (roll).setParseAction(self.push_first)
                    | integer
                )
        )

        term = operand + (rollop + operand).setParseAction(self.push_first)[...]
        expression <<= term + (addop + term).setParseAction(self.push_first)[...]
        bnf = expression

        return bnf