/*

  * 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.framework.block;

 import java.util.Iterator;

 import org.apache.giraph.block_app.framework.piece.AbstractPiece;

 import org.apache.giraph.function.Consumer;

 /**

  * Composable unit of execution. Used to combine other Blocks into

  * bigger units. Each Piece represents a Block itself.

  *

  * Execution is represented as an iterator across Pieces.

  *

  * The whole application run is represented by a single block at the end.

  */

 @SuppressWarnings("rawtypes")

 public interface Block extends Iterable<AbstractPiece> {

   /**

    * Create iterator representing all pieces needed to be executed

    * in this block.

    *

    * After Iterator.next call returns, master compute of returned Piece is

    * guaranteed to be called before calling hasNext/next on the iterator.

    * (allows for iterators logic to depend on the execution dynamically,

    * and not be only static)

    */

   @Override

   Iterator<AbstractPiece> iterator();

   /**

    * Calls consumer for each Piece:

    * - in no particular order

    * - potentially calling multiple times on same Piece

    * - even if Piece might never be returned in the iterator

    * - it will be called at least once for every piece that is

    *   going to be returned by iterator

    *

    * Can be used for static analysis/introspection of the block,

    * without actually executing them.

    */

   void forAllPossiblePieces(Consumer<AbstractPiece> consumer);

   /**

    * How many pieces are in this block.

    * Sometimes we don't know (eg RepeatBlock).

    *

    * @return How many pieces are in this block.

    */

   PieceCount getPieceCount();

 }