void NoFood(pSnakeNode pn, pSnake ps)
{
	//头插法
	pn->next = ps->_pSnake;
	ps->_pSnake = pn;

	pSnakeNode cur = ps->_pSnake;
	while (cur->next->next != NULL)
	{
		SetPos(cur->x, cur->y);
		wprintf(L"%lc", BODY);
		cur = cur->next;
	}

	//把最后一个结点打印成空格
	SetPos(cur->next->x, cur->next->y);
	printf("  ");

	//释放最后一个结点
	free(cur->next);

	//将倒数第二个结点的地址域置为NULL
	cur->next = NULL;
}

int NextIsFood(pSnakeNode pn, pSnake ps)
{
	return (ps->_pFood->x == pn->x && ps->_pFood->y == pn->y);
}

void EatFood(pSnakeNode pn, pSnake ps)
{
	//头插法
	ps->_pFood->next = ps->_pSnake;
	ps->_pSnake = ps->_pFood;

	//释放下一个位置的结点（我们设置了一个食物结点 和下一个结点 ）
	free(pn);
	pn = NULL;
	pSnakeNode cur = ps->_pSnake;
	//打印蛇
	while (cur)
	{
		SetPos(cur->x, cur->y);
		wprintf(L"%lc", BODY);
		cur = cur->next;
	}
	ps->_score += ps->_food_weight;

	//重新创建食物
	CreateFood(ps);
}

void pause()//暂停
{
	while (1)
	{
		Sleep(200);
		if (KEY_PRESS(VK_SPACE))
		{
			break;
		}
	}
}

void SnakeMove(pSnake ps)
{
	//创建一个结点 表示蛇即将到的下一个结点
	pSnakeNode pNextNode=(pSnakeNode)malloc(sizeof(Snakenode));
	if (pNextNode == NULL)
	{
		perror("SnakeMove()::malloc()");
		return;
	}
	switch (ps->_dir)
	{
	case UP:
		pNextNode->x = ps->_pSnake->x;
		pNextNode->y = ps->_pSnake->y-1;
		break;
	case DOWN:
		pNextNode->x = ps->_pSnake->x;
		pNextNode->y = ps->_pSnake->y+1;
		break;
	case LEFT:
		pNextNode->x = ps->_pSnake->x-2;
		pNextNode->y = ps->_pSnake->y;
		break;
	case RIGHT:
		pNextNode->x = ps->_pSnake->x+2;
		pNextNode->y = ps->_pSnake->y;
		break;
	}

	//检测下一个坐标处是否是食物
	if (NextIsFood(pNextNode,ps))
	{
		EatFood(pNextNode, ps);
	}
	else
	{
		NoFood(pNextNode, ps);
	}

	//检测蛇是否撞墙
	KillByWall(ps);
	//检测蛇是否撞到自己
	KillBySelf(ps);
}