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

// pridanie na zaciatok
struct snake* add_snake(struct snake* snake, int x, int y) {
    struct snake* head = calloc(1, sizeof(struct snake));
    head->x = x;
    head->y = y;
    head->next = snake;
    return head;
}
// odstranenie posledneho
struct snake* remove_snake(struct snake* snake) {
    if (snake == NULL) return NULL;

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

    struct snake* snak = snake;

    while (snak->next->next != NULL) {
        snak = snak->next;
    }

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

    return snake;
}

// kontrola ci bod je v hadovi
int is_snake(struct snake* snake, int x, int y) {
    struct snake* snak = snake;

    while (snak != NULL) {
        if (snak->x == x && snak->y == y) return 1;
        snak = snak->next;
    }

    return 0;
}

// uvolnenie celeho hada
void free_snake(struct snake* sn) {
    struct snake* snak = sn;

    while (snak != NULL) {
        struct snake* next = snak->next;
        free(snak);
        snak = next;
    }
}

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

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

    // had
    if (is_snake(state->snake, nx, ny)) {
        return END_SNAKE;
    }

    // jedlo
    for (int i = 0; i < FOOD_COUNT; i++) {
        if (state->foodx[i] == nx && state->foody[i] == ny) {

            state->foodx[i] = -1;
            state->foody[i] = -1;

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

            int je_jedlo = 0;
            for (int j = 0; j < FOOD_COUNT; j++) {
                if (state->foodx[j] >= 0) je_jedlo = 1;
            }

            if (!je_jedlo) return END_FOOD;

            return END_CONTINUE;
        }
    }

    // normalny pohyb
    state->snake = add_snake(state->snake, nx, ny);
    state->snake = remove_snake(state->snake);

    return END_CONTINUE;
}