"""
dice.py: written by Scaevolus 2008, updated 2009
simulates dicerolls
"""
import re
import random

from util import hook


whitespace_re = re.compile(r'\s+')
valid_diceroll_re = re.compile(r'^[+-]?(\d+|\d*d\d+)([+-](\d+|\d*d\d+))*$', 
                               re.I)
sign_re = re.compile(r'[+-]?(?:\d*d)?\d+', re.I)
split_re = re.compile(r'([\d+-]*)d?(\d*)', re.I)


def nrolls(count, n):
    "roll an n-sided die count times"
    if n < 2: #it's a coin
        if count < 5000:
            return sum(random.randint(0, 1) for x in xrange(count))
        else: #fake it
            return int(random.normalvariate(.5*count, (.75*count)**.5))
    else:
        if count < 5000:
            return sum(random.randint(1, n) for x in xrange(count))
        else: #fake it
            return int(random.normalvariate(.5*(1+n)*count,
                (((n+1)*(2*n+1)/6.-(.5*(1+n))**2)*count)**.5))


@hook.command
@hook.command('roll')
def dice(inp):
    ".dice <diceroll> -- simulates dicerolls, e.g. .dice 2d20-d5+4 roll 2 " \
        "D20s, subtract 1D5, add 4"
    if not inp:
        return dice.__doc__

    spec = whitespace_re.sub('', inp)
    if not valid_diceroll_re.match(spec):
        return "Invalid diceroll"
    sum = 0
    groups = sign_re.findall(spec)
    for roll in groups:
        count, side = split_re.match(roll).groups()
        if side == "":
            sum += int(count)
        else:
            count = int(count) if count not in" +-" else 1
            side = int(side)
            try:
                if count > 0:
                    sum += nrolls(count, side)
                else:
                    sum -= nrolls(abs(count), side)
            except OverflowError:
                return "Thanks for overflowing a float, jerk >:["

    return str(sum)