/**
 * Copyright 2010 the original author or authors.
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
 * in compliance with the License. You may obtain a copy of the License at
 * http://www.apache.org/licenses/LICENSE-2.0
 * Unless required by applicable law or agreed to in writing, software distributed under the License
 * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
 * or implied. See the License for the specific language governing permissions and limitations under
 * the License.
 */

package org.apache.helix.zookeeper.zkclient;

import java.io.IOException;
import java.util.List;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;

import org.apache.helix.zookeeper.zkclient.exception.ZkException;
import org.apache.log4j.Logger;
import org.apache.zookeeper.CreateMode;
import org.apache.zookeeper.KeeperException;
import org.apache.zookeeper.Op;
import org.apache.zookeeper.OpResult;
import org.apache.zookeeper.Watcher;
import org.apache.zookeeper.ZooDefs.Ids;
import org.apache.zookeeper.ZooKeeper;
import org.apache.zookeeper.ZooKeeper.States;
import org.apache.zookeeper.data.ACL;
import org.apache.zookeeper.data.Stat;


public class ZkConnection implements IZkConnection {
  private static final Logger LOG = Logger.getLogger(ZkConnection.class);

  /** It is recommended to use quite large sessions timeouts for ZooKeeper. */
  private static final int DEFAULT_SESSION_TIMEOUT = 30000;

  private ZooKeeper _zk = null;
  private Lock _zookeeperLock = new ReentrantLock();

  private final String _servers;
  private final int _sessionTimeOut;

  public ZkConnection(String zkServers) {
    this(zkServers, DEFAULT_SESSION_TIMEOUT);
  }

  public ZkConnection(String zkServers, int sessionTimeOut) {
    _servers = zkServers;
    _sessionTimeOut = sessionTimeOut;
  }

  @Override
  public void connect(Watcher watcher) {
    _zookeeperLock.lock();
    try {
      if (_zk != null) {
        throw new IllegalStateException("zk client has already been started");
      }
      try {
        LOG.debug("Creating new ZookKeeper instance to connect to " + _servers + ".");
        _zk = new ZooKeeper(_servers, _sessionTimeOut, watcher);
      } catch (IOException e) {
        throw new ZkException("Unable to connect to " + _servers, e);
      }
    } finally {
      _zookeeperLock.unlock();
    }
  }

  @Override
  public void close() throws InterruptedException {
    _zookeeperLock.lock();
    try {
      if (_zk != null) {
        LOG.debug("Closing ZooKeeper connected to " + _servers);
        _zk.close();
        _zk = null;
      }
    } finally {
      _zookeeperLock.unlock();
    }
  }

  protected void reconnect(Watcher watcher) throws InterruptedException {
    _zookeeperLock.lock();
    try {
      if (_zk == null) {
        throw new IllegalStateException("zk client has not been connected or already been closed");
      }
      ZooKeeper prevZk = _zk;
      try {
        LOG.debug("Creating new ZookKeeper instance to reconnect to " + _servers + ".");
        _zk = new ZooKeeper(_servers, _sessionTimeOut, watcher);
        prevZk.close();
      } catch (IOException e) {
        throw new ZkException("Unable to connect to " + _servers, e);
      }
    } finally {
      _zookeeperLock.unlock();
    }
  }

  @Override
  public String create(String path, byte[] data, CreateMode mode)
      throws KeeperException, InterruptedException {
    return _zk.create(path, data, Ids.OPEN_ACL_UNSAFE, mode);
  }

  @Override
  public String create(String path, byte[] data, List<ACL> acl, CreateMode mode)
      throws KeeperException, InterruptedException {
    return _zk.create(path, data, acl, mode);
  }

  @Override
  public void delete(String path) throws InterruptedException, KeeperException {
    _zk.delete(path, -1);
  }

  @Override
  public boolean exists(String path, boolean watch) throws KeeperException, InterruptedException {
    return _zk.exists(path, watch) != null;
  }

  @Override
  public List<String> getChildren(final String path, final boolean watch)
      throws KeeperException, InterruptedException {
    return _zk.getChildren(path, watch);
  }

  @Override
  public byte[] readData(String path, Stat stat, boolean watch)
      throws KeeperException, InterruptedException {
    return _zk.getData(path, watch, stat);
  }

  public void writeData(String path, byte[] data) throws KeeperException, InterruptedException {
    writeData(path, data, -1);
  }

  @Override
  public void writeData(String path, byte[] data, int version)
      throws KeeperException, InterruptedException {
    _zk.setData(path, data, version);
  }

  @Override
  public Stat writeDataReturnStat(String path, byte[] data, int version)
      throws KeeperException, InterruptedException {
    return _zk.setData(path, data, version);
  }

  @Override
  public States getZookeeperState() {
    return _zk != null ? _zk.getState() : null;
  }

  public ZooKeeper getZookeeper() {
    return _zk;
  }

  @Override
  public long getCreateTime(String path) throws KeeperException, InterruptedException {
    Stat stat = _zk.exists(path, false);
    if (stat != null) {
      return stat.getCtime();
    }
    return -1;
  }

  @Override
  public String getServers() {
    return _servers;
  }

  @Override
  public List<OpResult> multi(Iterable<Op> ops) throws KeeperException, InterruptedException {
    return _zk.multi(ops);
  }

  @Override
  public void addAuthInfo(String scheme, byte[] auth) {
    _zk.addAuthInfo(scheme, auth);
  }
}
