"""hand.py: the cards. A card is two letters, rank and suit: "As" is the ace of spades, "Td" the ten
of diamonds. A hand's strength is a tuple of numbers, and Python compares tuples from the left.
"""

import secrets
from collections import Counter
from itertools import combinations

RANKS = "23456789TJQKA"
SUITS = "shdc"
NAMES = ["high card", "a pair", "two pair", "three of a kind", "a straight", "a flush", "a full house", "four of a kind", "a straight flush"]


def shuffled_deck():
    """A new deck, shuffled with the system's secure random numbers: random.shuffle can be predicted."""
    deck = [rank + suit for rank in RANKS for suit in SUITS]
    secrets.SystemRandom().shuffle(deck)
    return deck


def strength(cards):
    """The strength of exactly five cards: (category, then the ranks that break a tie)."""
    ranks = sorted((RANKS.index(card[0]) for card in cards), reverse=True)
    # The biggest group first, then the highest rank: a full house reads (three's rank, pair's rank).
    groups = sorted(Counter(ranks).items(), key=lambda group: (-group[1], -group[0]))
    shape = [n for _, n in groups]
    order = [rank for rank, _ in groups]

    flush = all(card[1] == cards[0][1] for card in cards)
    high = -1  # the top card of a straight
    if len(groups) == 5:
        if ranks[0] - ranks[4] == 4:
            high = ranks[0]
        elif ranks == [12, 3, 2, 1, 0]:  # A-2-3-4-5: the ace counts low, the five is top
            high = 3

    if flush and high >= 0:
        return (8, high)
    if shape == [4, 1]:
        return (7, *order)
    if shape == [3, 2]:
        return (6, *order)
    if flush:
        return (5, *ranks)
    if high >= 0:
        return (4, high)
    if shape == [3, 1, 1]:
        return (3, *order)
    if shape == [2, 2, 1]:
        return (2, *order)
    if shape == [2, 1, 1, 1]:
        return (1, *order)
    return (0, *ranks)


def best_hand(cards):
    """The best five of a player's two cards and the board: (score, name)."""
    score = max(strength(five) for five in combinations(cards, 5))
    return score, NAMES[score[0]]