/*
 * This file is part of the Wildfire Chat package.
 * (c) Heavyrain2012 <heavyrain.lee@gmail.com>
 *
 * For the full copyright and license information, please view the LICENSE
 * file that was distributed with this source code.
 */

package win.liyufan.im;

import java.util.Date;

public class MessageShardingUtil {
    private static SpinLock mLock = new SpinLock();
    private static int rotateId = 0;
    private static int nodeId = 0;

    private static int rotateIdWidth = 15;
    private static int rotateIdMask = 0x7FFF;

    private static int nodeIdWidth = 6;
    private static int nodeIdMask = 0x3F;

    private static final long T201801010000 = 1514736000000L;

    public static void setNodeId(int nodeId) {
        MessageShardingUtil.nodeId = nodeId;
    }

    /**
     * ID = timestamp(43) + nodeId(6) + rotateId(15)
     * 所以时间限制是到2157/5/15（2的42次幂代表的时间 + (2018-1970)）。节点数限制是小于64，每台服务器每毫秒最多发送32768条消息
     * @return
     */
    public static long generateId() {
        mLock.lock();
        rotateId = (rotateId + 1)&rotateIdMask;
        mLock.unLock();

        long id = System.currentTimeMillis() - T201801010000;


        id <<= nodeIdWidth;
        id += (nodeId & nodeIdMask);

        id <<= rotateIdWidth;
        id += rotateId;
        return id;
    }

    public static String getMessageTable(long mid) {
        if (DBUtil.IsEmbedDB) {
            return "t_messages";
        }

        mid >>= (nodeIdWidth + rotateIdWidth);
        Date date = new Date(mid + T201801010000);
        int month = date.getMonth();
        int year = date.getYear();
        year %= 3;
        return "t_messages_" + (year * 12 + month);
    }
}
