package org.springblade.qinzhesync.utils;

public class SnowflakeIdGenerator {
	private final long workerId;
	private final long datacenterId;
	private long sequence = 0L;
	private long lastTimestamp = -1L;

	public SnowflakeIdGenerator(long workerId, long datacenterId) {
		this.workerId = workerId;
		this.datacenterId = datacenterId;
	}

	public synchronized long nextId() {
		long timestamp = System.currentTimeMillis();

		if (timestamp < lastTimestamp) {
			throw new RuntimeException("Clock moved backwards!");
		}

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

		lastTimestamp = timestamp;

		return ((timestamp - 1288834974657L) << 22) |
			(datacenterId << 17) |
			(workerId << 12) |
			sequence;
	}

	private long tilNextMillis(long lastTimestamp) {
		long timestamp = System.currentTimeMillis();
		while (timestamp <= lastTimestamp) {
			timestamp = System.currentTimeMillis();
		}
		return timestamp;
	}
}