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

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

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

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

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

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

    // skontroluje jedlo
    for (int i = 0; i < FOOD_COUNT; ++i) {
        if (st->foodx[i] == nx && st->foody[i] == ny) {
            // zje
            st->foodx[i] = -1;
            st->foody[i] = -1;
            // hlava
            st->snake = add_snake(st->snake, nx, ny);

            // skontroluje ci ostalo jedlo
            int food_left = 0;
            for (int j = 0; j < FOOD_COUNT; ++j) {
                if (st->foodx[j] >= 0 && st->foody[j] >= 0) {
                    food_left = 1;
                    break;
                }
            }

            return food_left ? END_CONTINUE : END_FOOD;
        }
    }

    // Regular move (no food)
    st->snake = add_snake(st->snake, nx, ny);
    st->snake = remove_snake(st->snake);
    return END_CONTINUE;
}