#!/usr/bin/env python3

import argparse
import itertools


def calculate_odds(current_hp, level, static_bonus, hp_die):
    non_rolled_hp = hp_die + static_bonus * level
    rolled_hp = current_hp - non_rolled_hp
    average_rolled = rolled_hp / (level - 1)

    possible_rolls_each_level = list(range(2, hp_die + 1))

    all_possible_rolls = itertools.product(*[
        possible_rolls_each_level
        for _ in range(level - 1)
    ])

    below_or_at_rolled_hp = 0

    for n, result in enumerate(all_possible_rolls, 1):
        if sum(result) <= rolled_hp:
            below_or_at_rolled_hp += 1

    probability_of_rolling_rolled_result_or_worse = below_or_at_rolled_hp / n

    return (
        average_rolled,
        n,
        below_or_at_rolled_hp,
        n - below_or_at_rolled_hp,
        probability_of_rolling_rolled_result_or_worse,
    )


def main():
    parser = argparse.ArgumentParser()
    parser.add_argument('--current-hp', type=int)
    parser.add_argument('--static-bonus-per-level', type=int, default=0,
                        help=('Total static bonus per level, including '
                              'CON bonus and feats'))
    parser.add_argument('--level', type=int)
    parser.add_argument('--hitpoint-die', type=int, choices=[6, 8, 10, 12])

    args = parser.parse_args()

    avg, tot, below, above, prob = calculate_odds(
        args.current_hp,
        args.level,
        args.static_bonus_per_level,
        args.hitpoint_die)

    print('Average rolled:', avg)
    print('Total rolls:', tot)
    print('Number of rolls resulting in average or below', below)
    print('Number of rolls resulting in above average', above)
    print('Probability of rolling average or below:', prob)
    print('Percent chanc rolling average or below: %.2f%%' % (prob * 100))


if __name__ == '__main__':
    main()