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

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;
}

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

	}
	return snake;
}

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

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

int step_state(struct state* st){
	int nx = (st->snake->x + st->sx);
    	int ny = (st->snake->y + st->sy);
    	if (is_snake(st->snake, nx, ny)) {
		free_snake(st->snake);
		return END_SNAKE;
	}
	else {
		int food_eaten = 0;
		int remaining_food = 0;
		for (int i = 0; i<FOOD_COUNT; i++) {
			if ((st->foodx[i] == -1) || (st->foody[i] == -1)) continue;
			if ((nx == st->foodx[i]) && (ny == st->foody[i])) {
				st->snake = add_snake(st->snake, nx, ny);
				food_eaten = 1;
				st->foodx[i] = -1;
				st->foody[i] = -1;
			}
			else remaining_food++;
		}
		if ((nx > 0) && (nx < st->width) && (ny > 0) && (ny < st->height)) {
                        if ((!food_eaten)) {
				st->snake = add_snake(st->snake, nx, ny);
                   		st->snake = remove_snake(st->snake);
			}
		}
		else {
			free_snake(st->snake);
			return END_WALL;
		}
		
		if (remaining_food == 0) {
			free_snake(st->snake);
			return END_FOOD;
		}
	}
	return END_CONTINUE;

}