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

// Pridá nový diel hada na začiatok (hlavu)
struct snake* add_snake(struct snake* snake, int x, int y){
    struct snake* new_head = malloc(sizeof(struct snake));
    if(!new_head){
      return NULL;
    }
    new_head->x = x;
    new_head->y = y;
    new_head->next = snake;
    return new_head;
}

// Odstráni posledný diel hada (chvost)
struct snake* remove_snake(struct snake* snake){
    if(!snake || !snake->next){
        free(snake);
        return NULL;
    }

    struct snake* current = snake;
    while (current->next && current->next->next){
        current = current->next;
    }
    free(current->next);
    current->next = NULL;
    return snake;
}

// Zistí, či sa na daných súradniciach nachádza časť hada
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;
}

// Uvoľní pamäť všetkých častí hada
void free_snake(struct snake* sn){
    while(sn){
        struct snake* next = sn->next;
        free(sn);
        sn = next;
    }
}

// Spraví jeden krok hry – aktualizuje stav podľa pohybu
int step_state(struct state* state){
    if(!state || !state->snake) return END_USER;

    int new_x = state->snake->x + state->sx;
    int new_y = state->snake->y + state->sy;

    // Kontrola nárazu do steny
    if(new_x < 0 || new_x >= state->width || new_y < 0 || new_y >= state->height){
        return END_WALL;
    }

    // Kontrola nárazu do seba samého
    if(is_snake(state->snake, new_x, new_y)){
        return END_SNAKE;
    }

    // Kontrola, či had zjedol jedlo
    for(int i = 0; i < FOOD_COUNT; i++){
        if(state->foodx[i] == new_x && state->foody[i] == new_y){
            // Označí jedlo ako zjedené
            state->foodx[i] = -1;
            state->foody[i] = -1;
            // Pridá nový diel hada na pozíciu jedla
            state->snake = add_snake(state->snake, new_x, new_y);

            // Skontroluje, či ešte zostalo jedlo
            int food_left = 0;
            for(int j = 0; j < FOOD_COUNT; j++){
                if(state->foodx[j] >= 0 && state->foody[j] >= 0){
                    food_left = 1;
                    break;
                }
            }
            return food_left ? END_CONTINUE : END_FOOD;
        }
    }

    // Bežný pohyb – had sa pohne o jedno políčko
    state->snake = add_snake(state->snake, new_x, new_y);
    state->snake = remove_snake(state->snake);
    return END_CONTINUE;
}