#include <stdio.h>
#include <stdbool.h>
#include <stdlib.h>
#include <time.h>

typedef enum {
    CARD_ACE, CARD_2, CARD_3, CARD_4, CARD_5, CARD_6, CARD_7, CARD_8, CARD_9, CARD_10, CARD_J, CARD_Q, CARD_K, CARD_COUNT,
} Card_Type;

typedef struct {
    Card_Type cards[16];
    int count;
} Hand;

typedef struct {
    Card_Type cards[64];
    int count;
} Deck;

static void swapCard(Card_Type *a, Card_Type *b) {
    Card_Type tmp = *a;
    *a = *b;
    *b = tmp;
}

void shuffleDeck(Deck *d) {
    if (!d) return;
    int n = d->count;
    if (n <= 1) return;
    for (int i = n - 1; i > 0; --i) {
        int j = rand() % (i + 1); // uniform in [0,i]
        swapCard(&d->cards[i], &d->cards[j]);
    }
}

int cardValue(Card_Type card) {
    return card + 1 <= 10 ? card + 1 : 10;
}

void takeCard(Deck *deck, Hand *hand) {
    hand->cards[hand->count++] = deck->cards[--deck->count];
};

int countScore(Hand hand) {
    int score = 0;
    bool has_ace = false;
    for(int i = 0; i < hand.count; i++){
        if(hand.cards[i] == CARD_ACE) has_ace = true;
        score += cardValue(hand.cards[i]);
    }
    return score + has_ace * 10;
}

void printResult(int player_score, int dealer_score) {
    if(player_score > 21) {
        puts("player lost\n");
        return;
    } else if(player_score == 21 && dealer_score != 21) {
        puts("!!!BLACKJACK!!!\n");
        return;
    } else if(player_score == dealer_score) {
        puts("push\n");
        return;
    } else if(dealer_score > 21 || player_score > dealer_score) {
        puts("player won\n");
        return;
    } else if(dealer_score > player_score) {
        puts("player lost\n");
        return;
    }
}

int main() {
    srand((unsigned)time(NULL));
    Deck deck = {0};
    for(int i = 0; i < CARD_COUNT; i++){
        deck.cards[deck.count++] = i;
        deck.cards[deck.count++] = i;
        deck.cards[deck.count++] = i;
        deck.cards[deck.count++] = i;
    }

    shuffleDeck(&deck);
    shuffleDeck(&deck);
    shuffleDeck(&deck);

    Hand dealer = {0};
    Hand player = {0};
    takeCard(&deck, &player);
    takeCard(&deck, &player);
    takeCard(&deck, &dealer);

    char cmd;
    bool ask = true;
    if(countScore(player) == 21) ask = false;
    while(ask){
        printf("player score: %d\n", countScore(player));
        printf("dealer score: %d\n", countScore(dealer));
        puts("[H]it or [S]tand?\n");
        
        do {
            cmd = getchar();
            if (cmd == EOF) return 0;
            if (cmd == '\n') break;
        } while (cmd == ' ' || cmd == '\t');
        if (cmd == '\n') continue;

        int ch;
        while ((ch = getchar()) != EOF && ch != '\n') { /* discard */ }

        switch (cmd) {
            case 'h':
            case 'H':
                takeCard(&deck, &player);
                if(countScore(player) >= 21) ask = false;
                break;
            case 's':
            case 'S':
                ask = false;
                break;
            case 'q':
                puts("Quitting.");
                return 0;
            default:
                printf("Unknown command: %c\n", cmd);
        }
    }

    if(countScore(player) >= 21) {
        takeCard(&deck, &dealer);
    } else {
        while(countScore(dealer) < 17) takeCard(&deck, &dealer);
    }

    printf("player score: %d\n", countScore(player));
    printf("dealer score: %d\n", countScore(dealer));
    printResult(countScore(player), countScore(dealer));
    return 0;
}