#pragma once

#include <atomic>
#include <mutex>

class CUniqueId
{
public:
	CUniqueId();
	CUniqueId(const unsigned char &workerId, const unsigned char &datacenterId)
	{
		_workerId = workerId;
		_datacenterId = datacenterId;
	}
	~CUniqueId();

private:
	// 开始utc时间戳(2018-01-01 00:00:00.000);
	const unsigned long long _twepoch = 1514736000000;
	// 工作者占用位数;
	const unsigned char _workerIdBits = 5;
	// 支持的最大工作者id，结果是31;
	const unsigned char _maxWorkerId = -1L ^ (-1L << _workerIdBits);
	// 数据中心占用位数;
	const unsigned char _datacenterIdBits = 5;
	// 支持的最大数据中心id，结果是31;
	const unsigned char _maxDatacenterId = -1L ^ (-1L << _datacenterIdBits);
	// 序列占用位数;
	const unsigned char _sequenceBits = 12;

	// 工作者向左移12位;
	const unsigned char _workerIdShift = _sequenceBits;
	// 数据中心向左移17位;
	const unsigned char _datacenterIdShift = _workerIdShift + _workerIdBits;
	// 时间戳向左移22位;
	const unsigned char _timestampleftShift = _datacenterIdShift + _datacenterIdBits;
	// 生成的序列掩码,4095;
	const unsigned short _sequenceMask = -1L ^ (-1L << _sequenceBits);

	// 工作id; 
	unsigned char _workerId;
	// 数据中心id;
	unsigned char _datacenterId;
	// 序列值;
	unsigned short _sequence;
	// 上一次的时间戳;
	static unsigned long long _lasttimestamp;

#ifndef USE_C0X
	// 如果不是c++11的话,不能使用atomic;
	std::mutex _mutex;
#endif
private:
	unsigned long long next_timestamp();

public:
	void setWorkerId(const unsigned char &workerId);
	void setDatacenterId(const unsigned char &datacenterId);
	unsigned long long get_unique_id();
};