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

struct snake* add_snake(struct snake* head, int x, int y) {
    struct snake* new_head = (struct snake*)malloc(sizeof(struct snake));
    new_head->x = x;
    new_head->y = y;
    new_head->next = head;
    return new_head;
}
struct snake* remove_snake(struct snake* head) {
    if (head == NULL || head->next == NULL) {
        free(head);
        return NULL;
    }
    struct snake* current = head;
    while (current->next->next != NULL) {
        current = current->next;
    }
    free(current->next);
    current->next = NULL;
    return head;
}
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) {
    struct snake* current = snake;
    while (current != NULL) {
        struct snake* next = current->next;
        free(current);
        current = 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_y < 0 || new_x >= state->width || 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) {
                    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;
}