# dice.py
#
# This module contains a class to represent various RPG-style dice expressions.
# These can then be rolled and the results, both total and individual rolls, returned.
#
# This module assumes that the built-in python PRNG (Mersenne Twister) is acceptable.
# Support for real entropy is an RFE.

import random
import re

class Dice():
    # This builds dice out of a simple input format
    # All of the dark regex magic is contained to this function,
    # lest it corrupt innocent code
    @classmethod
    def from_str(cls, desc):
        if not re.match(r'^\d+d\d+', desc):
            raise Exception('Dice format invalid. See --help')

        (n, s) = re.match(r'^(\d+)d(\d+)', desc).groups()
        num = int(n)
        sides = int(s)
        mod = 0
        drop_low = 0
        drop_high = 0
        reroll = 0
        reroll_times = 0

        for m in re.findall(r'[lh+-]\d+', desc):
            if m[0] == '-':
                mod += int(m)
            elif m[0] == '+':
                mod += int(m[1:])
            elif m[0] == 'h':
                drop_high = int(m[1:])
            elif m[0] == 'l':
                drop_low = int(m[1:])

        m = re.search(r'r(\d+)(x\d+)?', desc)
        if m:
            (r, rt) = m.groups()
            reroll = int(r)
            if rt:
                reroll_times = int(rt[1:])

        return cls(num, sides, mod, drop_low, drop_high, reroll, reroll_times)


    def __init__(self, num, sides, mod, drop_low=0, drop_high=0, reroll=0, reroll_times=0):
        self.num = num
        self.sides = sides
        self.mod = mod
        self.drop_low = drop_low
        self.drop_high = drop_high
        self.reroll = reroll
        self.reroll_times = reroll_times
        self.times_rolled = 0


    def num_rolls(self):
        return self.times_rolled

        
    # Rolls the dice, returns a structure
    # containing the result plus metadata
    def roll(self, verbose=False):
        results = []
        rerolled = []
        dropped = []

        # Roll the actual dice, handling rerolls
        for i in range(0, self.num):
            count = 0
            result = 0
            while result <= self.reroll or result == 0:
                if self.reroll_times and count >= self.reroll_times:
                    break

                result = random.randint(1, self.sides)
                count += 1
                if result <= self.reroll:
                    rerolled.append(result)

            results.append(result)
            

        # Drop any high or low, if specified
        if self.drop_low or self.drop_high:
            results.sort()

            if self.drop_low:
                dropped.extend(results[:self.drop_low])
                results = results[self.drop_low:]

            if self.drop_high:
                dropped.extend(results[-1 * self.drop_high:])
                results = results[:-1 * self.drop_high]
            
            random.shuffle(results)
            
        # Get the results
        total = sum(results) + self.mod

        self.times_rolled += 1

        return {'total': total, 'rolls': results, 'dropped': dropped, 'rerolled': rerolled}


    def __str__(self):
        reroll_info = ''
        drop_info = ''
        mod_info = ''

        if self.reroll:
            reroll_info = ' [reroll {}'.format(self.reroll)
            if self.reroll_times:
                reroll_info = reroll_info + 'x{}'.format(self.reroll_times)
            reroll_info = reroll_info + ']'

        if self.drop_low:
            drop_info = drop_info + ' [drop low {}]'.format(self.drop_low)
        if self.drop_high:
            drop_info = drop_info + ' [drop high {}]'.format(self.drop_high)

        if self.mod > 0:
            mod_info = '+{}'.format(self.mod)
        elif self.mod < 0:
            mod_info = '-{}'.format(self.mod)

        return "{num}d{sides}{mod}{drop}{reroll}".format(num=self.num, sides=self.sides, mod=mod_info, drop=drop_info, reroll=reroll_info)