/**
 * Copyright (C) 2014-2016 LinkedIn Corp. (pinot-core@linkedin.com)
 *
 * 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 com.linkedin.pinot.client;

import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.Map.Entry;
import java.util.Set;

import java.util.zip.GZIPInputStream;
import org.I0Itec.zkclient.ZkClient;
import org.json.JSONObject;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * Reads brokers external view from Zookeeper
 */
public class ExternalViewReader {
  private static final Logger LOGGER = LoggerFactory.getLogger(ExternalViewReader.class);

  private ZkClient zkClient;

  public static String BROKER_EXTERNAL_VIEW_PATH = "/EXTERNALVIEW/brokerResource";
  public static String REALTIME_SUFFIX = "_REALTIME";
  public static String OFFLINE_SUFFIX = "_OFFLINE";

  public ExternalViewReader(ZkClient zkClient) {
    this.zkClient = zkClient;
  }

  public List<String> getLiveBrokers() {
    List<String> brokerUrls = new ArrayList<String>();
    try {

      byte[] brokerResourceNodeData = zkClient.readData(BROKER_EXTERNAL_VIEW_PATH, true);
      brokerResourceNodeData = unpackZnodeIfNecessary(brokerResourceNodeData);
      JSONObject jsonObject = new JSONObject(new String(brokerResourceNodeData));
      JSONObject brokerResourceNode = jsonObject.getJSONObject("mapFields");

      Iterator<String> resourceNames = brokerResourceNode.keys();
      while (resourceNames.hasNext()) {
        String resourceName = resourceNames.next();
        JSONObject resource = brokerResourceNode.getJSONObject(resourceName);

        Iterator<String> brokerNames = resource.keys();
        while (brokerNames.hasNext()) {
          String brokerName = brokerNames.next();
          if (brokerName.startsWith("Broker_") && "ONLINE".equals(resource.getString(brokerName))) {
            // Turn Broker_12.34.56.78_1234 into 12.34.56.78:1234
            String brokerHostPort = brokerName.replace("Broker_", "").replace("_", ":");
            brokerUrls.add(brokerHostPort);
          }
        }
      }
    } catch (Exception e) {
      LOGGER.warn("Exception while reading External view from zookeeper", e);
      // ignore
    }
    return brokerUrls;
  }

  @SuppressWarnings("unchecked")
  public Map<String, List<String>> getTableToBrokersMap() {
    Map<String, Set<String>> brokerUrlsMap = new HashMap<>();
    try {
      byte[] brokerResourceNodeData = zkClient.readData("/EXTERNALVIEW/brokerResource", true);
      brokerResourceNodeData = unpackZnodeIfNecessary(brokerResourceNodeData);
      JSONObject jsonObject = new JSONObject(new String(brokerResourceNodeData));
      JSONObject brokerResourceNode = jsonObject.getJSONObject("mapFields");

      Iterator<String> resourceNames = brokerResourceNode.keys();
      while (resourceNames.hasNext()) {
        String resourceName = resourceNames.next();
        String tableName = resourceName.replace(OFFLINE_SUFFIX, "").replace(REALTIME_SUFFIX, "");
        Set<String> brokerUrls = brokerUrlsMap.get(tableName);
        if (brokerUrls == null) {
          brokerUrls = new HashSet<>();
          brokerUrlsMap.put(tableName, brokerUrls);
        }
        JSONObject resource = brokerResourceNode.getJSONObject(resourceName);
        Iterator<String> brokerNames = resource.keys();
        while (brokerNames.hasNext()) {
          String brokerName = brokerNames.next();
          if (brokerName.startsWith("Broker_") && "ONLINE".equals(resource.getString(brokerName))) {
            // Turn Broker_12.34.56.78_1234 into 12.34.56.78:1234
            String brokerHostPort = brokerName.replace("Broker_", "").replace("_", ":");
            brokerUrls.add(brokerHostPort);
          }
        }
      }
    } catch (Exception e) {
      LOGGER.warn("Exception while reading External view from zookeeper", e);
      // ignore
    }
    Map<String, List<String>> tableToBrokersMap = new HashMap<>();
    for (Entry<String, Set<String>> entry : brokerUrlsMap.entrySet()) {
      tableToBrokersMap.put(entry.getKey(), new ArrayList<>(entry.getValue()));
    }
    return tableToBrokersMap;
  }

  private static byte[] unpackZnodeIfNecessary(byte[] znodeContents) {
    // Check for gzip header
    if (znodeContents[0] == 0x1F && znodeContents[1] == (byte) 0x8B) {
      try {
        GZIPInputStream inputStream = new GZIPInputStream(new ByteArrayInputStream(znodeContents));
        ByteArrayOutputStream outputStream = new ByteArrayOutputStream();
        int byteRead = inputStream.read();

        while (byteRead != -1) {
          outputStream.write(byteRead);
          byteRead = inputStream.read();
        }

        return outputStream.toByteArray();
      } catch (IOException e) {
        LOGGER.error("Failed to decompress znode contents", e);
        return znodeContents;
      }
    } else {
      // Doesn't look compressed, just return the contents verbatim
      return znodeContents;
    }
  }
}