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

struct snake* add_snake(struct snake* snake, int x, int y) {
    struct snake* h = calloc(1, sizeof(struct snake));
    h->x = x;
    h->y = y;
    h->next = snake;
    return h;
}

struct snake* remove_snake(struct snake* snake) {
    if (!snake) return NULL;

    if (!snake->next) {
        free(snake);
        return NULL;
    }

    struct snake* cur = snake;

    while (cur->next->next)
        cur = cur->next;

    free(cur->next);
    cur->next = NULL;

    return snake;
}

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

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

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

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

    if (is_snake(s->snake, nx, ny))
        return END_SNAKE;

    int ate = 0;

    for (int i = 0; i < FOOD_COUNT; i++) {
        if (s->foodx[i] == nx && s->foody[i] == ny) {
            s->foodx[i] = -1;
            s->foody[i] = -1;
            ate = 1;
            break;
        }
    }

    s->snake = add_snake(s->snake, nx, ny);

    if (!ate) {
        s->snake = remove_snake(s->snake);
    }

    for (int i = 0; i < FOOD_COUNT; i++) {
        if (s->foodx[i] >= 0)
            return END_CONTINUE;
    }

    return END_FOOD;
}