/*
 * 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.
 */
package org.apache.geode.kafka.source;

import static org.apache.geode.kafka.utils.GeodeSourceConfigurationConstants.REGION_PARTITION;

import java.util.ArrayList;
import java.util.Collection;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.stream.Collectors;

import org.apache.kafka.connect.errors.ConnectException;
import org.apache.kafka.connect.source.SourceRecord;
import org.apache.kafka.connect.source.SourceTask;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import org.apache.geode.cache.client.ClientCache;
import org.apache.geode.cache.query.CqAttributes;
import org.apache.geode.cache.query.CqAttributesFactory;
import org.apache.geode.cache.query.CqQuery;
import org.apache.geode.cache.query.CqResults;
import org.apache.geode.cache.query.Struct;
import org.apache.geode.kafka.GeodeContext;
import org.apache.geode.kafka.Version;

public class GeodeKafkaSourceTask extends SourceTask {

  private static final Logger logger = LoggerFactory.getLogger(GeodeKafkaSourceTask.class);

  private static final String TASK_PREFIX = "TASK";
  private static final String DOT = ".";

  // property string to pass in to identify task
  private static final Map<String, Long> OFFSET_DEFAULT = createOffset();

  private GeodeContext geodeContext;
  private EventBufferSupplier eventBufferSupplier;
  private Map<String, List<String>> regionToTopics;
  private Map<String, Map<String, String>> sourcePartitions;
  private int batchSize;


  private static Map<String, Long> createOffset() {
    Map<String, Long> offset = new HashMap<>();
    offset.put("OFFSET", 0L);
    return offset;
  }

  @Override
  public String version() {
    return Version.getVersion();
  }

  @Override
  public void start(Map<String, String> props) {
    logger.info("Starting Apache Geode source task");
    try {
      GeodeSourceConnectorConfig geodeConnectorConfig = new GeodeSourceConnectorConfig(props);
      logger.debug("GeodeKafkaSourceTask id:" + geodeConnectorConfig.getTaskId() + " starting");
      geodeContext = new GeodeContext();
      ClientCache clientCache =
          geodeContext.connectClient(geodeConnectorConfig.getLocatorHostPorts(),
              geodeConnectorConfig.getDurableClientId(),
              geodeConnectorConfig.getDurableClientTimeout(),
              geodeConnectorConfig.getSecurityClientAuthInit(),
              geodeConnectorConfig.getSecurityUserName(),
              geodeConnectorConfig.getSecurityPassword(),
              geodeConnectorConfig.usesSecurity());
      if (clientCache == null) {
        throw new ConnectException("Unable to create client cache in the source task");
      }
      batchSize = geodeConnectorConfig.getBatchSize();
      eventBufferSupplier = new SharedEventBufferSupplier(geodeConnectorConfig.getQueueSize());

      regionToTopics = geodeConnectorConfig.getRegionToTopics();
      sourcePartitions = createSourcePartitionsMap(regionToTopics.keySet());

      String cqPrefix = geodeConnectorConfig.getCqPrefix();
      boolean loadEntireRegion = geodeConnectorConfig.getLoadEntireRegion();
      installOnGeode(geodeConnectorConfig, geodeContext, eventBufferSupplier, cqPrefix,
          loadEntireRegion);
      logger.info("Started Apache Geode source task");
    } catch (Exception e) {
      logger.error("Unable to start source task", e);
      if (e instanceof ConnectException) {
        throw e;
      } else {
        throw new ConnectException(e);
      }
    }
  }

  @Override
  public List<SourceRecord> poll() {
    logger.trace("Polling for new data");
    ArrayList<SourceRecord> records = new ArrayList<>(batchSize);
    ArrayList<GeodeEvent> events = new ArrayList<>(batchSize);
    if (eventBufferSupplier.get().drainTo(events, batchSize) > 0) {
      logger.debug("Geode events polled :" + events.size());
      for (GeodeEvent event : events) {
        String regionName = event.getRegionName();
        List<String> topics = regionToTopics.get(regionName);
        for (String topic : topics) {
          records.add(new SourceRecord(sourcePartitions.get(regionName), OFFSET_DEFAULT, topic,
              null, event.getKey(), null, event.getValue()));
        }
      }
      return records;
    }

    return null;
  }

  @Override
  public void stop() {
    logger.info("Stopping Apache Geode source task");
    geodeContext.close(true);
  }

  void installOnGeode(GeodeSourceConnectorConfig geodeConnectorConfig, GeodeContext geodeContext,
      EventBufferSupplier eventBuffer, String cqPrefix, boolean loadEntireRegion) {
    boolean isDurable = geodeConnectorConfig.isDurable();
    int taskId = geodeConnectorConfig.getTaskId();
    for (String region : geodeConnectorConfig.getCqsToRegister()) {
      installListenersToRegion(geodeContext, taskId, eventBuffer, region, cqPrefix,
          loadEntireRegion, isDurable);
    }
    if (isDurable) {
      geodeContext.getClientCache().readyForEvents();
    }
  }

  GeodeKafkaSourceListener installListenersToRegion(GeodeContext geodeContext, int taskId,
      EventBufferSupplier eventBuffer, String regionName, String cqPrefix, boolean loadEntireRegion,
      boolean isDurable) {
    CqAttributesFactory cqAttributesFactory = new CqAttributesFactory();
    GeodeKafkaSourceListener listener = new GeodeKafkaSourceListener(eventBuffer, regionName);
    cqAttributesFactory.addCqListener(listener);
    CqAttributes cqAttributes = cqAttributesFactory.create();
    try {
      if (loadEntireRegion) {
        CqResults<?> events =
            geodeContext.newCqWithInitialResults(generateCqName(taskId, cqPrefix, regionName),
                "select * from /" + regionName, cqAttributes,
                isDurable);
        eventBuffer.get()
            .addAll(events.stream().map(
                e -> new GeodeEvent(regionName, ((Struct) e).get("key"), ((Struct) e).get("value")))
                .collect(Collectors.toList()));
      } else {
        final CqQuery cqQuery = geodeContext.newCq(generateCqName(taskId, cqPrefix, regionName),
            "select * from /" + regionName, cqAttributes,
            isDurable);
        if (cqQuery == null) {
          throw new ConnectException("Unable to executed queries on the Apache Geode server");
        }
      }
    } finally {
      listener.signalInitialResultsLoaded();
    }
    return listener;
  }

  /**
   * converts a list of regions names into a map of source partitions
   *
   * @param regionNames list of regionNames
   * @return Map<String, Map < String, String>> a map of source partitions, keyed by region name
   */
  Map<String, Map<String, String>> createSourcePartitionsMap(Collection<String> regionNames) {
    return regionNames.stream().map(regionName -> {
      Map<String, String> sourcePartition = new HashMap<>();
      sourcePartition.put(REGION_PARTITION, regionName);
      return sourcePartition;
    }).collect(Collectors.toMap(s -> s.get(REGION_PARTITION), s -> s));
  }

  String generateCqName(int taskId, String cqPrefix, String regionName) {
    return cqPrefix + DOT + TASK_PREFIX + taskId + DOT + regionName;
  }
}