#include "snake.h"
#include <stdlib.h>

struct snake* add_snake(struct snake* snake, int x, int y) {
    struct snake* nova_hlava = malloc(sizeof(struct snake));
    nova_hlava->x = x;
    nova_hlava->y = y;
    nova_hlava->next = snake;
    return nova_hlava;
}

struct snake* remove_snake(struct snake* snake) {
    if (snake == NULL) return NULL;
    if (snake->next == NULL) {
        free(snake);
        return NULL;
    }
    struct snake* aktualny = snake;
    while (aktualny->next->next != NULL) {
        aktualny = aktualny->next;
    }
    free(aktualny->next);
    aktualny->next = NULL;
    return snake;
}

void free_snake(struct snake* sn) {
    while (sn != NULL) {
        struct snake* dalsi = sn->next;
        free(sn);
        sn = dalsi;
    }
}

int is_snake(struct snake* snake, int x, int y) {
    struct snake* aktualny = snake;
    while (aktualny != NULL) {
        if (aktualny->x == x && aktualny->y == y) return 1;
        aktualny = aktualny->next;
    }
    return 0;
}

int step_state(struct state* st) {
    int nx = (st->snake->x + st->sx);
    int ny = (st->snake->y + st->sy);

    if (nx < 0 || nx >= st->width ||
        ny < 0 || ny >= st->height) {
        return END_WALL;
    }

    if (is_snake(st->snake, nx, ny)) {
        return END_SNAKE;
    }

    for (int i = 0; i < FOOD_COUNT; i++) {
        if (st->foodx[i] == nx && st->foody[i] == ny) {
            st->snake = add_snake(st->snake, nx, ny);
            st->foodx[i] = -1;
            st->foody[i] = -1;
            for (int j = 0; j < FOOD_COUNT; j++) {
                if (st->foodx[j] >= 0) return END_CONTINUE;
            }
            return END_FOOD;
        }
    }

    st->snake = add_snake(st->snake, nx, ny);
    st->snake = remove_snake(st->snake);
    return END_CONTINUE;
}