package org.apache.helix.ui.util;

/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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.
 */

import com.google.common.cache.*;
import org.apache.helix.manager.zk.ZNRecordSerializer;
import org.apache.helix.manager.zk.ZkClient;
import org.apache.helix.ui.api.ClusterConnection;
import org.apache.zookeeper.ZooKeeper;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import javax.ws.rs.WebApplicationException;
import javax.ws.rs.core.Response;
import java.net.URLDecoder;
import java.util.HashSet;
import java.util.Map;
import java.util.Set;
import java.util.concurrent.TimeUnit;

public class ClientCache {
  private static final Logger LOG = LoggerFactory.getLogger(ClientCache.class);
  private static final int DEFAULT_SESSION_TIMEOUT_MILLIS = 5000;
  private static final int DEFAULT_CONNECTION_TIMEOUT_MILLIS = 5000;

  private final ZkAddressValidator zkAddressValidator;
  private final Map<String, String> zkAliases;

  public ClientCache(ZkAddressValidator zkAddressValidator, Map<String, String> zkAliases) {
    this.zkAddressValidator = zkAddressValidator;
    this.zkAliases = zkAliases;
  }

  // Manages and caches lifecycle of connections to ZK
  final LoadingCache<String, ClusterConnection> clientCache = CacheBuilder.newBuilder()
          .maximumSize(3)
          .expireAfterAccess(5, TimeUnit.MINUTES)
          .removalListener(new RemovalListener<String, ClusterConnection>() {
            @Override
            public void onRemoval(RemovalNotification<String, ClusterConnection> removalNotification) {
              if (removalNotification.getValue() != null) {
                ZkClient zkClient = removalNotification.getValue().getZkClient();
                if (zkClient != null) {
                  zkClient.close();
                  LOG.info("Disconnected from {}", removalNotification.getKey());
                }
              }
            }
          })
          .build(new CacheLoader<String, ClusterConnection>() {
            @Override
            public ClusterConnection load(String zkAddress) throws Exception {
              ZkClient zkClient = new ZkClient(
                      zkAddress,
                      DEFAULT_SESSION_TIMEOUT_MILLIS,
                      DEFAULT_CONNECTION_TIMEOUT_MILLIS,
                      new ZNRecordSerializer());
              zkClient.waitUntilConnected();
              LOG.info("Connected to {}", zkAddress);
              return new ClusterConnection(zkClient);
            }
          });

  public ClusterConnection get(String zkAddress) {
    // Map alias if exists
    if (zkAliases.containsKey(zkAddress)) {
      zkAddress = zkAliases.get(zkAddress);
    }

    try {
      zkAddress = URLDecoder.decode(zkAddress, "UTF-8");
    } catch (Exception e) {
      throw new IllegalArgumentException(e);
    }

    if (!zkAddressValidator.validate(zkAddress)) {
      throw new WebApplicationException("Cannot access " + zkAddress, Response.Status.UNAUTHORIZED);
    }

    ClusterConnection clusterConnection;
    try {
      clusterConnection = clientCache.get(zkAddress);
    } catch (Exception e) {
      throw new WebApplicationException(e, Response.Status.GATEWAY_TIMEOUT);
    }

    if (!clusterConnection.getZkClient().getConnection().getZookeeperState().equals(ZooKeeper.States.CONNECTED)) {
      clientCache.invalidate(zkAddress);
      throw new WebApplicationException("ZooKeeper connection was dead", Response.Status.GATEWAY_TIMEOUT);
    }

    return clusterConnection;
  }

  public void invalidateAll() {
    clientCache.invalidateAll();
  }

  public Set<String> getDeadConnections() {
    Set<String> deadConnections = new HashSet<String>();
    for (Map.Entry<String, ClusterConnection> entry : clientCache.asMap().entrySet()) {
      if (!entry.getValue().getZkClient().getConnection().getZookeeperState().isAlive()) {
        deadConnections.add(entry.getKey());
      }
    }
    return deadConnections;
  }
}