package org.beetl.sql.ext;

public class SnowflakeIDWorker {

	//日期，2010年，用到2080年
	public static long twepoch = 1288834974657L;
	private long workerId;
	private long datacenterId;
	private long sequence = 0L;
	private long workerIdBits = 5L;
	private long datacenterIdBits = 5L;
	//31
	private long maxWorkerId = -1L ^ (-1L << workerIdBits);
	//31
	private long maxDatacenterId = -1L ^ (-1L << datacenterIdBits);
	private long sequenceBits = 12L;

	private long workerIdShift = sequenceBits;
	private long datacenterIdShift = sequenceBits + workerIdBits;
	private long timestampLeftShift = sequenceBits + workerIdBits + datacenterIdBits;
	private long sequenceMask = -1L ^ (-1L << sequenceBits);

	private long lastTimestamp = -1L;

	public SnowflakeIDWorker(long workerId, long datacenterId) {
		// sanity check for workerId
		if (workerId > maxWorkerId || workerId < 0) {
			throw new IllegalArgumentException(
					String.format("worker Id can't be greater than %d or less than 0", maxWorkerId));
		}
		if (datacenterId > maxDatacenterId || datacenterId < 0) {
			throw new IllegalArgumentException(
					String.format("datacenter Id can't be greater than %d or less than 0", maxDatacenterId));
		}
		this.workerId = workerId;
		this.datacenterId = datacenterId;
	}

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

		if (timestamp < lastTimestamp) {
			throw new RuntimeException(
					String.format("Clock moved backwards.  Refusing to generate id for %d milliseconds",
							lastTimestamp - timestamp));
		}

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

		lastTimestamp = timestamp;

		return ((timestamp - twepoch) << timestampLeftShift) | (datacenterId << datacenterIdShift) | (workerId
				<< workerIdShift) | sequence;
	}

	protected long tilNextMillis(long lastTimestamp) {
		long timestamp = timeGen();
		while (timestamp <= lastTimestamp) {
			timestamp = timeGen();
		}
		return timestamp;
	}

	protected long timeGen() {
		return System.currentTimeMillis();
	}


}
