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

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;
}

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

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

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;
}

void free_snake(struct snake* sn) {
    while (sn) {
        struct snake* next = sn->next;
        free(sn);
        sn = 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->snake = add_snake(state->snake, new_x, new_y);
            state->foodx[i] = -1;
            state->foody[i] = -1;

            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;
        }
    }

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