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


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


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


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


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


int step_state(struct state* state) {
    int new_x = state->snake->x + state->sx;
    int new_y = state->snake->y + state->sy;

    if (new_x < 0 || new_x >= state->width || new_y < 0 || new_y >= state->height)
        return END_WALL; 
    if (is_snake(state->snake, new_x, new_y))
        return END_SNAKE;


    for (int i = 0; i < FOOD_COUNT; i++) {
        if (state->foodx[i] == new_x && state->foody[i] == new_y) {
            state->foodx[i] = state->foody[i] = -1;
            state->snake = add_snake(state->snake, new_x, new_y);

            int all_eaten = 1;
            for (int j = 0; j < FOOD_COUNT; j++) {
                if (state->foodx[j] != -1 || state->foody[j] != -1) {
                    all_eaten = 0;
                    break;
                }
            }
            return all_eaten ? END_FOOD : END_CONTINUE;
        }
    }


    state->snake = add_snake(state->snake, new_x, new_y);
    state->snake = remove_snake(state->snake);
    return END_CONTINUE;
}