/**
 * 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.tez.mapreduce.common;

import java.io.IOException;
import java.util.List;
import java.util.concurrent.TimeUnit;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.apache.hadoop.classification.InterfaceAudience.Public;
import org.apache.hadoop.classification.InterfaceStability.Evolving;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.mapred.JobConf;
import org.apache.tez.common.TezUtils;
import org.apache.tez.dag.api.Vertex;
import org.apache.tez.mapreduce.hadoop.MRInputHelpers;
import org.apache.tez.mapreduce.hadoop.MRJobConfig;
import org.apache.tez.mapreduce.lib.MRInputUtils;
import org.apache.tez.mapreduce.protos.MRRuntimeProtos.MRInputUserPayloadProto;
import org.apache.tez.mapreduce.protos.MRRuntimeProtos.MRSplitProto;
import org.apache.tez.mapreduce.protos.MRRuntimeProtos.MRSplitsProto;
import org.apache.tez.runtime.api.Event;
import org.apache.tez.runtime.api.InputInitializer;
import org.apache.tez.runtime.api.InputInitializerContext;
import org.apache.tez.runtime.api.events.InputDataInformationEvent;
import org.apache.tez.runtime.api.events.InputInitializerEvent;
import org.apache.tez.runtime.api.events.InputUpdatePayloadEvent;
import org.apache.tez.util.StopWatch;

import com.google.common.collect.Lists;

/**
 * Implements an {@link InputInitializer} that distributes Map Reduce 
 * splits created by the client to tasks in the {@link Vertex}
 * This can be used when certain reasons (e.g. security) prevent splits
 * from being produced in the App Master via {@link MRInputAMSplitGenerator}
 * and splits must be produced at the client. They can still be distributed
 * intelligently among tasks at runtime using this.
 */
@Public
@Evolving
public class MRInputSplitDistributor extends InputInitializer {

  private static final Logger LOG = LoggerFactory.getLogger(MRInputSplitDistributor.class);
  
  private boolean sendSerializedEvents;

  private MRSplitsProto splitsProto;

  public MRInputSplitDistributor(InputInitializerContext initializerContext) {
    super(initializerContext);
  }

  @Override
  public List<Event> initialize() throws IOException {
    StopWatch sw = new StopWatch().start();
    MRInputUserPayloadProto userPayloadProto = MRInputHelpers
        .parseMRInputPayload(getContext().getInputUserPayload());
    sw.stop();
    if (LOG.isDebugEnabled()) {
      LOG.debug("Time to parse MRInput payload into prot: "
          + sw.now(TimeUnit.MILLISECONDS));
    }
    Configuration conf = TezUtils.createConfFromByteString(userPayloadProto
        .getConfigurationBytes());
    JobConf jobConf = new JobConf(conf);
    boolean useNewApi = jobConf.getUseNewMapper();
    sendSerializedEvents = conf.getBoolean(
        MRJobConfig.MR_TEZ_INPUT_INITIALIZER_SERIALIZE_EVENT_PAYLOAD,
        MRJobConfig.MR_TEZ_INPUT_INITIALIZER_SERIALIZE_EVENT_PAYLOAD_DEFAULT);
    LOG.info("Emitting serialized splits: " + sendSerializedEvents);

    this.splitsProto = userPayloadProto.getSplits();
    
    MRInputUserPayloadProto.Builder updatedPayloadBuilder = MRInputUserPayloadProto.newBuilder(userPayloadProto);
    updatedPayloadBuilder.clearSplits();

    List<Event> events = Lists.newArrayListWithCapacity(this.splitsProto.getSplitsCount() + 1);
    InputUpdatePayloadEvent updatePayloadEvent = InputUpdatePayloadEvent.create(
        updatedPayloadBuilder.build().toByteString().asReadOnlyByteBuffer());

    events.add(updatePayloadEvent);
    int count = 0;

    for (MRSplitProto mrSplit : this.splitsProto.getSplitsList()) {

      InputDataInformationEvent diEvent;

      if (sendSerializedEvents) {
        // Unnecessary array copy, can be avoided by using ByteBuffer instead of
        // a raw array.
        diEvent = InputDataInformationEvent.createWithSerializedPayload(count++,
            mrSplit.toByteString().asReadOnlyByteBuffer());
      } else {
        if (useNewApi) {
          org.apache.hadoop.mapreduce.InputSplit newInputSplit = MRInputUtils
              .getNewSplitDetailsFromEvent(mrSplit, conf);
          diEvent = InputDataInformationEvent.createWithObjectPayload(count++, newInputSplit);
        } else {
          org.apache.hadoop.mapred.InputSplit oldInputSplit = MRInputUtils
              .getOldSplitDetailsFromEvent(mrSplit, conf);
          diEvent = InputDataInformationEvent.createWithObjectPayload(count++, oldInputSplit);
        }
      }
      events.add(diEvent);
    }

    return events;
  }

  @Override
  public void handleInputInitializerEvent(List<InputInitializerEvent> events) throws Exception {
    throw new UnsupportedOperationException("Not expecting to handle any events");
  }
}