package com.ruoyi.project.common;

import java.net.InetAddress;
import java.util.concurrent.ThreadLocalRandom;

public class IdGeneratorUtils {
    // 机器ID（0-31）
    private static final long MACHINE_ID = getMachineId() & 31L;
    // 时间戳左移的位数（22位给计数器，5位给机器ID）
    private static final long TIMESTAMP_SHIFT = 22 + 5;
    private static final long COUNTER_BITS = 22L;
    private static final long MAX_COUNTER = (1L << COUNTER_BITS) - 1;

    private static long lastTimestamp = -1L;
    private static long counter = 0L;

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

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

        if (timestamp == lastTimestamp) {
            counter = (counter + 1) & MAX_COUNTER;
            if (counter == 0) {
                // 同一毫秒内计数器用完，等待下一毫秒
                timestamp = waitNextMillis(lastTimestamp);
            }
        } else {
            counter = 0L;
        }

        lastTimestamp = timestamp;

        return ((timestamp) << TIMESTAMP_SHIFT) |
                (MACHINE_ID << COUNTER_BITS) |
                counter;
    }

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

    private static long getMachineId() {
        try {
            // 可以根据需要获取机器标识，比如IP地址最后一段
            String hostAddress = InetAddress.getLocalHost().getHostAddress();
            return Long.parseLong(hostAddress.split("\\.")[3]);
        } catch (Exception e) {
            return ThreadLocalRandom.current().nextLong(32);
        }
    }

}