package com.yoho.pay;

import com.yoho.core.common.utils.TimeUtils;

public class IdWorker{



    private long workerId;
    private long datacenterId;
    private long sequence=0;

    public IdWorker(long workerId, long datacenterId){
        // sanity check for workerId
        if (workerId > maxWorkerId || workerId < 0) {
            throw new IllegalArgumentException(String.format("worker CodeMeta can't be greater than %d or less than 0",maxWorkerId));
        }
        if (datacenterId > maxDatacenterId || datacenterId < 0) {
            throw new IllegalArgumentException(String.format("datacenter CodeMeta can't be greater than %d or less than 0",maxDatacenterId));
        }
        System.out.printf("worker starting. timestamp left shift %d, datacenter id bits %d, worker id bits %d, sequence bits %d, workerid %d",
                timestampLeftShift, datacenterIdBits, workerIdBits, sequenceBits, workerId);

        this.workerId = workerId;
        this.datacenterId = datacenterId;
    }

    private long twepoch = 1288834974657L;  // 起始时间戳

    // 1位(固定值0)  21位(时间戳) 2+2位(工作机器id=5位的datacenterId + 5位的workerId) 12位(序号位)
    // 一共64位，2的64位，最大能表示多少啊



    private long workerIdBits = 2L;
    private long datacenterIdBits = 2L;
    // 可以表示的最大正整数 2的N次方-1, 值为31
    private long maxWorkerId = -1L ^ (-1L << workerIdBits);

    // 可以标识的最大正整数 2的N次方-1,值为31
    private long maxDatacenterId = -1L ^ (-1L << datacenterIdBits);
    private long sequenceBits = 12L;

    // 左移12位
    private long workerIdShift = sequenceBits;
    // 左移 12+5位
    private long datacenterIdShift = sequenceBits + workerIdBits;
    // 左移 12+5+5 位
    private long timestampLeftShift = sequenceBits + workerIdBits + datacenterIdBits;

    private long tmp = timestampLeftShift + 41L;
    // 4095 2的n次方-1
    private long sequenceMask = -1L ^ (-1L << sequenceBits);

    private long tmpMask = -1L ^ (-1L << tmp);;

    private long lastTimestamp = -1L;

    public long getWorkerId(){
        return workerId;
    }

    public long getDatacenterId(){
        return datacenterId;
    }

    public long getTimestamp(){
        return System.currentTimeMillis();
    }

    public synchronized long nextId() {
        long timestamp = timeGen();

        if (timestamp < lastTimestamp) {
            System.err.printf("clock is moving backwards.  Rejecting requests until %d.", lastTimestamp);
            throw new RuntimeException(String.format("Clock moved backwards.  Refusing to generate id for %d milliseconds",
                    lastTimestamp - timestamp));
        }

        // 获取当前时间，如果此刻的毫秒和 上次的毫秒是同一个时间点，则序号+1
        if (lastTimestamp == timestamp) {
            // 如果原来的序号+1 以后的结果是0，则说明这一毫秒可用的序列号都用完了，sequenceMask 都为0，要结果为0, 只能说明，左边的数据是0
            // 一个数 与 一个全1的数字，不是还是等于左边的数吗？

            sequence = (sequence + 1) & sequenceMask;
            if (sequence == 0) {
                timestamp = tilNextMillis(lastTimestamp);
            }
        } else {
            sequence = 0;
        }

        lastTimestamp = timestamp;
        // 最后返回 返回的结果如下：
        return
                (((timestamp - twepoch) << timestampLeftShift) & tmpMask)|
                (datacenterId << datacenterIdShift) |
                (workerId << workerIdShift) |
                sequence;
    }

    private long tilNextMillis(long lastTimestamp) {
        // 等待下一个毫秒
        long timestamp = timeGen();
        while (timestamp <= lastTimestamp) {
            timestamp = timeGen();
        }
        return timestamp;
    }

    private long timeGen(){

        return System.currentTimeMillis();
    }

    //---------------测试---------------
    public static void main(String[] args) {
//        IdWorker worker = new IdWorker(1,1);
//        for (int i = 0; i < 30; i++) {
//            System.out.println(worker.nextId());
//        }

        // 现在的生成结果
        // 1041255103765549057



        // 生成一个时间错 左移22位， long 64位，左移以后超过64位的都被只设置未0， 毫秒需要41位来表示吗
        //  xxxxxx
        //  00000000xxxxxxx22位   则相当于时间戳位 有20位
        //  与 位数最高位，全一的数据与一下  ====> 超过最高位的左边都会与成0，从而将数限制在范围内



        System.out.println((System.currentTimeMillis() - 1288834974657L)<<22);

//        // 1000000000010
//        // 0111111111111
//        // 这样起到的作用，将位数超过的高位直接设置成0了，保证数据在 指定的位数之内，防止位数溢出
//        System.out.println(4095 & 4098);
    }

}