/*
    * 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.giraph.block_app.migration;
  
  import static org.apache.giraph.utils.ReflectionUtils.getTypeArguments;
  
  import java.io.IOException;
  import java.util.Collections;
  import java.util.List;
  
  import org.apache.giraph.block_app.framework.api.BlockMasterApi;
  import org.apache.giraph.block_app.framework.api.BlockWorkerContextReceiveApi;
  import org.apache.giraph.block_app.framework.api.BlockWorkerContextSendApi;
  import org.apache.giraph.block_app.framework.api.BlockWorkerReceiveApi;
  import org.apache.giraph.block_app.framework.api.BlockWorkerSendApi;
  import org.apache.giraph.block_app.framework.piece.PieceWithWorkerContext;
  import org.apache.giraph.block_app.framework.piece.interfaces.VertexReceiver;
  import org.apache.giraph.block_app.framework.piece.interfaces.VertexSender;
  import org.apache.giraph.block_app.migration.MigrationAbstractComputation.MigrationFullAbstractComputation;
  import org.apache.giraph.block_app.migration.MigrationMasterCompute.MigrationFullMasterCompute;
  import org.apache.giraph.block_app.migration.MigrationWorkerContext.MigrationFullWorkerContext;
  import org.apache.giraph.combiner.MessageCombiner;
  import org.apache.giraph.conf.DefaultMessageClasses;
  import org.apache.giraph.conf.GiraphConfiguration;
  import org.apache.giraph.conf.GiraphConstants;
  import org.apache.giraph.conf.ImmutableClassesGiraphConfiguration;
  import org.apache.giraph.conf.MessageClasses;
  import org.apache.giraph.conf.TypesHolder;
  import org.apache.giraph.factories.DefaultMessageValueFactory;
  import org.apache.giraph.function.Consumer;
  import org.apache.giraph.function.ObjectTransfer;
  import org.apache.giraph.function.Supplier;
  import org.apache.giraph.graph.Vertex;
  import org.apache.giraph.utils.ReflectionUtils;
  import org.apache.hadoop.io.Writable;
  import org.apache.hadoop.io.WritableComparable;
  
  import com.google.common.base.Preconditions;
  
  
  /**
   * Piece used when migrating applications to Blocks Framework.
   *
   * There are two migration levels:
   * <ul>
   * <li>
   * drop-in replacement migration is completely compatible with previous code.
   * Only necessary thing is to change parent classes from (AbstractComputation,
   * MasterCompute, WorkerContext) to (MigrationFullAbstractComputation,
   * MigrationFullMasterCompute and MigrationFullWorkerContext).
   * After that, all you need to do is extend MigrationBlockFactory, and pass
   * appropriate types and call createMigrationAppBlock with initial computations.
   * <br>
   * You can now combine multiple applications, or use any library written in the
   * framework, but your application is left as one whole indivisible block.
   * </li>
   * <li>
   * Piece-wise migration - which gives a set of independent pieces, which can
   * then be combined with appropriate ordering logic within a BlockFactory.
   * You need to modify parent classes in your code to
   * (MigrationAbstractComputation, MigrationMasterCompute and
   * MigrationWorkerContext), which don't have any methods that affect computation
   *  ordering - and so calling those methods should be
   * moved to logic within BlockFactory.
   * Calling MigrationPiece.createMigrationPiece and passing appropriate
   * computations, gives you an independent piece, that you can then use in the
   * same way as before, but also combine it in any other way with other pieces
   * you have or are written within a library.
   * </li>
   * </ul>
   *
   * Generally, migration path can be to first move to drop-in replacement without
   * any effort, and then see which parts need to be modified to be able to use
   * piece-wise migration. At the end, it should be trivial to move from
   * piece-wise migration to directly using pieces, by just moving code around,
   * if you want to.
   *
   * @param <I> Vertex id type
   * @param <V> Vertex value type
   * @param <E> Edge value type
   * @param <MPrev> Previous piece message type
   * @param <M> Message type
   */
  @SuppressWarnings("rawtypes")
 public final class MigrationPiece<I extends WritableComparable,
     V extends Writable, E extends Writable, MPrev extends Writable,
     M extends Writable> extends PieceWithWorkerContext<I, V, E, M,
     MigrationWorkerContext, Writable, MigrationSuperstepStage> {
 
   private final Class<? extends MigrationAbstractComputation<I, V, E, MPrev, M>>
   computationClass;
 
   private final transient MigrationMasterCompute masterCompute;
   private final Supplier<Iterable<MPrev>> previousMessagesSupplier;
   private final Consumer<Iterable<M>> currentMessagesConsumer;
   private final transient Class<M> messageClass;
   private final transient Class<? extends MessageCombiner<? super I, M>>
   messageCombinerClass;
 
   private final boolean isFullMigration;
   private final boolean isFirstStep;
 
   private transient MigrationPiece nextPiece;
   private boolean isHalted;
 
   private MigrationPiece(
       Class<? extends MigrationAbstractComputation<I, V, E, MPrev, M>>
         computationClass,
       MigrationMasterCompute masterCompute, Supplier<Iterable<MPrev>>
         previousMessagesSupplier,
       Consumer<Iterable<M>> currentMessagesConsumer, Class<M> messageClass,
       Class<? extends MessageCombiner<? super I, M>> messageCombinerClass,
       boolean isFullMigration, boolean isFirstStep) {
     this.computationClass = computationClass;
     this.masterCompute = masterCompute;
     this.previousMessagesSupplier = previousMessagesSupplier;
     this.currentMessagesConsumer = currentMessagesConsumer;
     this.messageClass = messageClass;
     this.messageCombinerClass = messageCombinerClass;
     this.isFullMigration = isFullMigration;
     this.isFirstStep = isFirstStep;
     isHalted = false;
     nextPiece = null;
     sanityChecks();
   }
 
 
   @SuppressWarnings("unchecked")
   static <I extends WritableComparable, V extends Writable, E extends Writable,
   MR extends Writable, MS extends Writable>
   MigrationPiece<I, V, E, MR, MS> createFirstFullMigrationPiece(
       Class<? extends MigrationAbstractComputation<I, V, E, MR, MS>>
         computationClass,
       MigrationFullMasterCompute masterCompute,
       Class<MS> messageClass,
       Class<? extends MessageCombiner<? super I, MS>> messageCombinerClass) {
     ObjectTransfer transfer = new ObjectTransfer();
     return new MigrationPiece<>(
         computationClass, masterCompute, transfer, transfer, messageClass,
         messageCombinerClass,
         true, true);
   }
 
   public static <I extends WritableComparable, V extends Writable,
   E extends Writable, MR extends Writable, MS extends Writable>
   MigrationPiece<I, V, E, MR, MS> createMigrationPiece(
       Class<? extends MigrationAbstractComputation<I, V, E, MR, MS>>
         computationClass,
       MigrationMasterCompute masterCompute,
       Supplier<Iterable<MR>> previousMessagesSupplier,
       Consumer<Iterable<MS>> currentMessagesConsumer,
       Class<MS> messageClass,
       Class<? extends MessageCombiner<? super I, MS>> messageCombinerClass) {
     return new MigrationPiece<>(
         computationClass, masterCompute, previousMessagesSupplier,
         currentMessagesConsumer, messageClass, messageCombinerClass,
         false, false);
   }
 
 
   private void sanityChecks() {
     Preconditions.checkState(isFullMigration ==
         MigrationFullAbstractComputation.class
           .isAssignableFrom(computationClass));
   }
 
   void sanityTypeChecks(
       GiraphConfiguration conf, Class<?> previousMessageClass) {
     if (computationClass != null) {
       final Class<?> vertexIdClass = GiraphConstants.VERTEX_ID_CLASS.get(conf);
       final Class<?> vertexValueClass =
           GiraphConstants.VERTEX_VALUE_CLASS.get(conf);
       final Class<?> edgeValueClass =
           GiraphConstants.EDGE_VALUE_CLASS.get(conf);
 
       Class<?>[] classList = getTypeArguments(
           TypesHolder.class, computationClass);
       Preconditions.checkArgument(classList.length == 5);
 
       ReflectionUtils.verifyTypes(
           vertexIdClass, classList[0], "vertexId", computationClass);
       ReflectionUtils.verifyTypes(
           vertexValueClass, classList[1], "vertexValue", computationClass);
       ReflectionUtils.verifyTypes(
           edgeValueClass, classList[2], "edgeValue", computationClass);
       if (previousMessageClass != null) {
         ReflectionUtils.verifyTypes(
             previousMessageClass, classList[3], "recvMessage",
             computationClass);
       }
       ReflectionUtils.verifyTypes(
           messageClass, classList[4], "sendMessage", computationClass);
     }
   }
 
   @Override
   public void registerAggregators(BlockMasterApi masterApi)
       throws InstantiationException, IllegalAccessException {
     if (masterCompute != null) {
       masterCompute.init(masterApi);
       masterCompute.initialize();
     }
   }
 
   @Override
   public VertexSender<I, V, E> getVertexSender(
       BlockWorkerSendApi<I, V, E, M> workerApi,
       MigrationSuperstepStage executionStage) {
     if (computationClass == null || isFirstStep) {
       return null;
     }
 
     final MigrationAbstractComputation<I, V, E, MPrev, M> computation =
         ReflectionUtils.newInstance(computationClass);
     computation.init(
         workerApi, getWorkerValue(workerApi),
         executionStage.getMigrationSuperstep() - 1);
     computation.preSuperstep();
 
     return new InnerVertexSender() {
       @Override
       public void vertexSend(Vertex<I, V, E> vertex) {
         try {
           Iterable<MPrev> messages = null;
           if (previousMessagesSupplier != null) {
             messages = previousMessagesSupplier.get();
           }
           if (messages == null) {
             messages = Collections.<MPrev>emptyList();
           }
           computation.compute(vertex, messages);
         } catch (IOException e) {
           throw new RuntimeException(e);
         }
       }
 
       @Override
       public void postprocess() {
         computation.postSuperstep();
       }
     };
   }
 
   @Override
   public void workerContextSend(
       BlockWorkerContextSendApi<I, Writable> workerContextApi,
       MigrationSuperstepStage executionStage,
       MigrationWorkerContext workerValue) {
     if (workerValue != null && !isFirstStep) {
       workerValue.setApi(workerContextApi);
       workerValue.postSuperstep();
     }
   }
 
   @SuppressWarnings("unchecked")
   @Override
   public void masterCompute(BlockMasterApi masterApi,
       MigrationSuperstepStage executionStage) {
     MigrationFullMasterCompute masterComputeF =
         isFullMigration ? (MigrationFullMasterCompute) masterCompute : null;
 
     if (masterCompute != null) {
       masterCompute.init(masterApi);
 
       if (masterComputeF != null) {
         masterComputeF.init(
             executionStage.getMigrationSuperstep(),
             computationClass, messageClass, messageCombinerClass);
       }
 
       masterCompute.compute();
     }
 
     if (isFullMigration) {
       if (masterComputeF != null) {
         isHalted = masterComputeF.isHalted();
         if (masterComputeF.isHalted()) {
           nextPiece = null;
         } else {
           if (masterComputeF.getNewComputationClass() != null ||
               masterComputeF.getNewMessage() != null ||
                   masterComputeF.getNewMessageCombiner() != null) {
             nextPiece = new MigrationPiece(
                 masterComputeF.getComputationClass(),
                 masterComputeF,
                 previousMessagesSupplier,
                 currentMessagesConsumer,
                 masterComputeF.getOutgoingMessage(),
                 masterComputeF.getMessageCombiner(),
                 true, false);
           } else {
             nextPiece = this;
           }
         }
       } else {
         nextPiece = this;
       }
       if (nextPiece != null) {
         if (nextPiece.isFirstStep) {
           nextPiece = new MigrationPiece<>(
               computationClass,
               masterComputeF,
               previousMessagesSupplier,
               currentMessagesConsumer,
               messageClass,
               messageCombinerClass,
               true, false);
         }
         nextPiece.sanityTypeChecks(masterApi.getConf(), messageClass);
       }
     } else {
       Preconditions.checkState(!isHalted);
       Preconditions.checkState(nextPiece == null);
     }
   }
 
   @Override
   public void workerContextReceive(
       BlockWorkerContextReceiveApi workerContextApi,
       MigrationSuperstepStage executionStage,
       MigrationWorkerContext workerValue, List<Writable> workerMessages) {
     if (workerValue != null) {
       workerValue.setApi(workerContextApi);
       workerValue.setReceivedMessages(workerMessages);
 
       if (isFirstStep && workerValue instanceof MigrationFullWorkerContext) {
         try {
           ((MigrationFullWorkerContext) workerValue).preApplication();
         } catch (InstantiationException | IllegalAccessException e) {
           throw new RuntimeException(e);
         }
       }
 
       if (!isHalted) {
         workerValue.preSuperstep();
       }
 
       if (isHalted && workerValue instanceof MigrationFullWorkerContext) {
         ((MigrationFullWorkerContext) workerValue).postApplication();
       }
     }
   }
 
   @Override
   public VertexReceiver<I, V, E, M> getVertexReceiver(
       BlockWorkerReceiveApi<I> workerApi,
       MigrationSuperstepStage executionStage) {
     if (currentMessagesConsumer == null || isHalted) {
       return null;
     }
 
     return new InnerVertexReceiver() {
       @Override
       public void vertexReceive(Vertex<I, V, E> vertex, Iterable<M> messages) {
         currentMessagesConsumer.apply(messages);
       }
     };
   }
 
   @Override
   public MessageClasses<I, M> getMessageClasses(
       ImmutableClassesGiraphConfiguration conf) {
     return new DefaultMessageClasses(
         messageClass,
         DefaultMessageValueFactory.class,
         messageCombinerClass,
         GiraphConstants.MESSAGE_ENCODE_AND_STORE_TYPE.get(conf));
   }
 
   @Override
   public MigrationSuperstepStage nextExecutionStage(
       MigrationSuperstepStage executionStage) {
     return executionStage.changedMigrationSuperstep(
         executionStage.getMigrationSuperstep() + 1);
   }
 
   public MigrationPiece getNextPiece() {
     Preconditions.checkState(isFullMigration);
     MigrationPiece res = nextPiece;
     nextPiece = null;
     return res;
   }
 
 }