/*
    * 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.library;
  
  import java.util.Iterator;
  
  import org.apache.giraph.block_app.framework.api.BlockMasterApi;
  import org.apache.giraph.block_app.framework.block.Block;
  import org.apache.giraph.block_app.framework.block.SequenceBlock;
  import org.apache.giraph.combiner.MessageCombiner;
  import org.apache.giraph.function.Consumer;
  import org.apache.giraph.function.Function;
  import org.apache.giraph.function.ObjectTransfer;
  import org.apache.giraph.function.PairConsumer;
  import org.apache.giraph.function.vertex.ConsumerWithVertex;
  import org.apache.giraph.function.vertex.FunctionWithVertex;
  import org.apache.giraph.function.vertex.SupplierFromVertex;
  import org.apache.giraph.graph.Vertex;
  import org.apache.giraph.reducers.ReduceOperation;
  import org.apache.hadoop.io.Writable;
  import org.apache.hadoop.io.WritableComparable;
  
  /**
   * Utility class for creating sequences of sending replies to received
   * messages. Current instance of this object represents partial chain,
   * where we have specified which messages will be send at the lastly defined
   * link in the chain thus far, but we haven't specified yet what to do when
   * vertices receive them.
   *
   * Contains set of:
   * - static startX methods, used to create the chain
   * - thenX methods, used to add one more Piece to the chain, can be
   *   "chained" arbitrary number of times.
   * - endX methods, used to finish the chain, returning
   *   the Block representing the whole chain
   *
   * If messageSupplier or targetsSupplier returns null, current vertex
   * is not going to send any messages.
   *
   * @param <I> Vertex id type
   * @param <V> Vertex value type
   * @param <E> Edge value type
   * @param <P> Previous value
   */
  public class SendMessageChain<I extends WritableComparable, V extends Writable,
      E extends Writable, P> {
    /**
     * Represent current partial chain. Given a way to consume messages
     * received in lastly defined link in this chain, it will produce block
     * representing a chain created thus far.
     */
    private final Function<ConsumerWithVertex<I, V, E, P>, Block> blockCreator;
  
    private SendMessageChain(
        Function<ConsumerWithVertex<I, V, E, P>, Block> blockCreator) {
      this.blockCreator = blockCreator;
    }
  
    /**
     * Start chain with sending message provided by messageSupplier to all
     * targets provided by targetsSupplier.
     */
    public static <I extends WritableComparable, V extends Writable,
    E extends Writable, M extends Writable>
    SendMessageChain<I, V, E, Iterable<M>> startSend(
        final String name,
        final Class<M> messageClass,
        final SupplierFromVertex<I, V, E, M> messageSupplier,
        final SupplierFromVertex<I, V, E, Iterator<I>> targetsSupplier) {
      return new SendMessageChain<>(
          new Function<ConsumerWithVertex<I, V, E, Iterable<M>>, Block>() {
            @Override
            public Block apply(
                ConsumerWithVertex<I, V, E, Iterable<M>> messagesConsumer) {
              return Pieces.sendMessage(
                  name, messageClass, messageSupplier,
                  targetsSupplier, messagesConsumer);
            }
          });
    }
  
    /**
     * Start chain with sending message provided by messageSupplier to all
     * targets provided by targetsSupplier, and use given messageCombiner to
    * combine messages together.
    */
   public static <I extends WritableComparable, V extends Writable,
   E extends Writable, M extends Writable>
   SendMessageChain<I, V, E, M> startSend(
       final String name,
       final MessageCombiner<? super I, M> messageCombiner,
       final SupplierFromVertex<I, V, E, M> messageSupplier,
       final SupplierFromVertex<I, V, E, Iterator<I>> targetsSupplier) {
     return new SendMessageChain<>(
         new Function<ConsumerWithVertex<I, V, E, M>, Block>() {
           @Override
           public Block apply(ConsumerWithVertex<I, V, E, M> messagesConsumer) {
             return Pieces.sendMessage(
                 name, messageCombiner, messageSupplier,
                 targetsSupplier, messagesConsumer);
           }
         });
   }
 
   /**
    * Start chain with sending message provided by messageSupplier to all
    * neighbors of a current vertex.
    */
   public static <I extends WritableComparable, V extends Writable,
   E extends Writable, M extends Writable>
   SendMessageChain<I, V, E, Iterable<M>> startSendToNeighbors(
       final String name,
       final Class<M> messageClass,
       final SupplierFromVertex<I, V, E, M> messageSupplier) {
     return startSend(name, messageClass, messageSupplier,
         VertexSuppliers.<I, V, E>vertexNeighborsSupplier());
   }
 
   /**
    * Start chain with sending message provided by messageSupplier to all
    * neighbors of a current vertex, and use given messageCombiner to
    * combine messages together.
    */
   public static <I extends WritableComparable, V extends Writable,
   E extends Writable, M extends Writable>
   SendMessageChain<I, V, E, M> startSendToNeighbors(
       final String name,
       final MessageCombiner<? super I, M> messageCombiner,
       final SupplierFromVertex<I, V, E, M> messageSupplier) {
     return startSend(name, messageCombiner, messageSupplier,
         VertexSuppliers.<I, V, E>vertexNeighborsSupplier());
   }
 
   /**
    * Start chain by providing a function that will produce Block representing
    * beginning of the chain, given a consumer of messages send
    * by the last link in the created block.
    */
   public static <I extends WritableComparable, V extends Writable,
   E extends Writable, P extends Writable>
   SendMessageChain<I, V, E, P> startCustom(
       Function<ConsumerWithVertex<I, V, E, P>, Block> createStartingBlock) {
     return new SendMessageChain<>(createStartingBlock);
   }
 
   /**
    * Give previously received message(s) to messageSupplier, and send message
    * it returns to all targets provided by targetsSupplier.
    */
   public <M extends Writable>
   SendMessageChain<I, V, E, Iterable<M>> thenSend(
       final String name,
       final Class<M> messageClass,
       final FunctionWithVertex<I, V, E, P, M> messageSupplier,
       final SupplierFromVertex<I, V, E, Iterator<I>> targetsSupplier) {
     final ObjectTransfer<P> prevMessagesTransfer = new ObjectTransfer<>();
 
     return new SendMessageChain<>(
         new Function<ConsumerWithVertex<I, V, E, Iterable<M>>, Block>() {
           @Override
           public Block apply(
               ConsumerWithVertex<I, V, E, Iterable<M>> messagesConsumer) {
             return new SequenceBlock(
               blockCreator.apply(
                   prevMessagesTransfer.<I, V, E>castToConsumer()),
               Pieces.sendMessage(
                 name, messageClass,
                 new SupplierFromVertex<I, V, E, M>() {
                   @Override
                   public M get(Vertex<I, V, E> vertex) {
                     return messageSupplier.apply(
                         vertex, prevMessagesTransfer.get());
                   }
                 },
                 targetsSupplier, messagesConsumer));
           }
         });
   }
 
   /**
    * Give previously received message(s) to messageSupplier, and send message
    * it returns to all neighbors of current vertex.
    */
   public <M extends Writable>
   SendMessageChain<I, V, E, Iterable<M>> thenSendToNeighbors(
       final String name,
       final Class<M> messageClass,
       final FunctionWithVertex<I, V, E, P, M> messageSupplier) {
     return thenSend(name, messageClass, messageSupplier,
         VertexSuppliers.<I, V, E>vertexNeighborsSupplier());
   }
 
   /**
    * Give previously received message(s) to messageSupplier, and send message
    * it returns to all targets provided by targetsSupplier, and use given
    * messageCombiner to combine messages together.
    */
   public <M extends Writable>
   SendMessageChain<I, V, E, M> thenSend(
       final String name,
       final MessageCombiner<? super I, M> messageCombiner,
       final FunctionWithVertex<I, V, E, P, M> messageSupplier,
       final SupplierFromVertex<I, V, E, Iterator<I>> targetsSupplier) {
     final ObjectTransfer<P> prevMessagesTransfer = new ObjectTransfer<>();
 
     return new SendMessageChain<>(
         new Function<ConsumerWithVertex<I, V, E, M>, Block>() {
           @Override
           public Block apply(ConsumerWithVertex<I, V, E, M> messagesConsumer) {
             return new SequenceBlock(
               blockCreator.apply(
                   prevMessagesTransfer.<I, V, E>castToConsumer()),
               Pieces.sendMessage(
                 name, messageCombiner,
                 new SupplierFromVertex<I, V, E, M>() {
                   @Override
                   public M get(Vertex<I, V, E> vertex) {
                     return messageSupplier.apply(
                         vertex, prevMessagesTransfer.get());
                   }
                 },
                 targetsSupplier, messagesConsumer));
           }
         });
   }
 
   /**
    * Give previously received message(s) to messageSupplier, and send message
    * it returns to all neighbors of current vertex, and use given
    * messageCombiner to combine messages together.
    */
   public <M extends Writable>
   SendMessageChain<I, V, E, M> thenSendToNeighbors(
       final String name,
       final MessageCombiner<? super I, M> messageCombiner,
       final FunctionWithVertex<I, V, E, P, M> messageSupplier) {
     return thenSend(name, messageCombiner, messageSupplier,
         VertexSuppliers.<I, V, E>vertexNeighborsSupplier());
   }
 
   /**
    * End chain by giving received messages to valueSupplier,
    * to produce value that should be reduced, and consumed on master
    * by reducedValueConsumer.
    */
   public <S, R extends Writable>
   Block endReduce(final String name, final ReduceOperation<S, R> reduceOp,
       final FunctionWithVertex<I, V, E, P, S> valueSupplier,
       final Consumer<R> reducedValueConsumer) {
     return endCustom(new Function<SupplierFromVertex<I, V, E, P>, Block>() {
       @Override
       public Block apply(final SupplierFromVertex<I, V, E, P> prevMessages) {
         return Pieces.reduce(
             name,
             reduceOp,
             new SupplierFromVertex<I, V, E, S>() {
               @Override
               public S get(Vertex<I, V, E> vertex) {
                 return valueSupplier.apply(vertex, prevMessages.get(vertex));
               }
             },
             reducedValueConsumer);
       }
     });
   }
 
   /**
    * End chain by giving received messages to valueSupplier,
    * to produce value that should be reduced, and consumed on master
    * by reducedValueConsumer.
    */
   public <S, R extends Writable>
   Block endReduceWithMaster(
       final String name, final ReduceOperation<S, R> reduceOp,
       final FunctionWithVertex<I, V, E, P, S> valueSupplier,
       final PairConsumer<R, BlockMasterApi> reducedValueConsumer) {
     return endCustom(new Function<SupplierFromVertex<I, V, E, P>, Block>() {
       @Override
       public Block apply(final SupplierFromVertex<I, V, E, P> prevMessages) {
         return Pieces.reduceWithMaster(
             name,
             reduceOp,
             new SupplierFromVertex<I, V, E, S>() {
               @Override
               public S get(Vertex<I, V, E> vertex) {
                 return valueSupplier.apply(vertex, prevMessages.get(vertex));
               }
             },
             reducedValueConsumer);
       }
     });
   }
 
   /**
    * End chain by processing messages received within the last link
    * in the chain.
    */
   public Block endConsume(ConsumerWithVertex<I, V, E, P> messagesConsumer) {
     return blockCreator.apply(messagesConsumer);
   }
 
   /**
    * End chain by providing a function that will produce Block to be attached
    * to the end of current chain, given a supplier of messages received
    * within the last link in the chain.
    */
   public Block endCustom(
       Function<SupplierFromVertex<I, V, E, P>, Block> createBlockToAttach) {
     final ObjectTransfer<P> prevMessagesTransfer = new ObjectTransfer<>();
     return new SequenceBlock(
         blockCreator.apply(prevMessagesTransfer.<I, V, E>castToConsumer()),
         createBlockToAttach.apply(
             prevMessagesTransfer.<I, V, E>castToSupplier()));
   }
 }