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

struct snake* add_snake(struct snake* snake, int x, int y) {

    struct snake* novy_uzol = calloc(1, sizeof(struct snake));

    novy_uzol->x = x;
    novy_uzol->y = y;
    novy_uzol->next = snake;
    return novy_uzol;
}

struct snake* remove_snake(struct snake* hlava) {

    if (hlava == NULL) return NULL;
    if (hlava->next == NULL) {
        free(hlava);
        return NULL;
    }

    hlava->next = remove_snake(hlava->next);
    return hlava;
}

int is_snake(struct snake* snake, int x, int y) {

    for (struct snake* clanok = snake; clanok != NULL; clanok = clanok->next) {
        if (clanok->x == x && clanok->y == y) return 1;
    }

    return 0;
}

void free_snake(struct snake* sn) {

    if (sn == NULL) return;
    free_snake(sn->next);
    free(sn);
}

int step_state(struct state* st) {

    int next_x = st->snake->x + st->sx;
    int next_y = st->snake->y + st->sy;

    if (next_x < 0 || next_x >= st->width || next_y < 0 || next_y >= st->height)
        return END_WALL;

    if (is_snake(st->snake, next_x, next_y))
        return END_SNAKE;

    for (int i = 0; i < FOOD_COUNT; i++) {

        if (st->foodx[i] == next_x && st->foody[i] == next_y) {

            st->foodx[i] = -1;
            st->foody[i] = -1;
            st->snake = add_snake(st->snake, next_x, next_y);

            int zostava_jedlo = 0;
            for (int j = 0; j < FOOD_COUNT; j++) {
                if (st->foodx[j] >= 0) zostava_jedlo = 1;
            }
            
            if (!zostava_jedlo) return END_FOOD;
            return END_CONTINUE;
        }
    }

    st->snake = add_snake(st->snake, next_x, next_y);
    st->snake = remove_snake(st->snake);
    return END_CONTINUE;
}