package fr.ens.biologie.genomique.eoulsan.util.locker;

import fr.ens.biologie.genomique.eoulsan.EoulsanException;
import org.apache.zookeeper.WatchedEvent;
import org.apache.zookeeper.Watcher;
import org.apache.zookeeper.ZooKeeper;

import java.io.IOException;
import java.util.concurrent.CountDownLatch;

/**
 * This class implements a locker using Zookeeper based on Twiter's DistributedLock class. See {@link <a href=
 * "https://github.com/twitter/commons/blob/master/src/java/com/twitter/common/zookeeper/DistributedLock.java">
 * Twitter Commons code</a>}
 * @author Laurent Jourdren
 * @since 2.0
 */
public class DistributedLocker implements Locker, Watcher {

    private final DistributedLock lock;
    private CountDownLatch connectSignal = new CountDownLatch(1);


    @Override
    public void lock() throws IOException {

        this.lock.lock();
    }

    @Override
    public void unlock() throws IOException {

        this.lock.unlock();
    }

    @Override
    public void process(WatchedEvent event) {

        if (event.getState() == Event.KeeperState.SyncConnected) {
            this.connectSignal.countDown();
        }
    }

    //
    // Constructor
    //

    /**
     * Public constructor.
     * @param connectString Zookeeper connection string
     * @param sessionTimeout session time out
     * @param lockBasePath lock base path
     * @param lockName lock name
     * @throws IOException if an error occurs while creating the ZooKeeper
     *           connection
     */
    public DistributedLocker(final String connectString, final int sessionTimeout,
                           final String lockBasePath, final String lockName) throws IOException {

        ZooKeeper zk = new ZooKeeper(connectString, sessionTimeout, this);
        try {
            connectSignal.await();
        } catch (InterruptedException e) {
            throw new IOException(e);
        }

        this.lock = new DistributedLock(zk,lockBasePath + '/'+ lockName);
    }

}