/*
    * 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.test_setup.graphs;
  
  import org.apache.giraph.block_app.test_setup.NumericTestGraph;
  import org.apache.giraph.block_app.test_setup.TestGraphModifier;
  import org.apache.giraph.function.Supplier;
  import org.apache.hadoop.io.Writable;
  import org.apache.hadoop.io.WritableComparable;
  
  
  /**
   * Create a directed forest that looks like:
   *
   *   0      4     6
   *  / \     |    / \
   * 1   2    5   7   8
   *     |
   *     3
   *
   * Edges are directed from top to bottom.
   * Vertices with no edges are created.
   *
   * @param <I> Vertex id type
   * @param <V> Vertex value type
   * @param <E> Edge value type
   */
  public class SmallDirectedForestGraphInit<I extends WritableComparable,
      V extends Writable, E extends Writable>
      implements TestGraphModifier<I, V, E> {
  
    private final Supplier<E> edgeSupplier;
  
    public SmallDirectedForestGraphInit() {
      this(null);
    }
  
    public SmallDirectedForestGraphInit(Supplier<E> edgeSupplier) {
      this.edgeSupplier = edgeSupplier;
    }
  
    @Override
    public void modifyGraph(NumericTestGraph<I, V, E> graph) {
      graph.addEdge(0, 1, createEdgeValue());
      graph.addEdge(0, 2, createEdgeValue());
      graph.addEdge(2, 3, createEdgeValue());
      graph.addEdge(4, 5, createEdgeValue());
      graph.addEdge(6, 7, createEdgeValue());
      graph.addEdge(6, 8, createEdgeValue());
  
      graph.addVertex(1);
      graph.addVertex(3);
      graph.addVertex(5);
      graph.addVertex(7);
      graph.addVertex(8);
    }
  
    private E createEdgeValue() {
      return edgeSupplier != null ? edgeSupplier.get() : null;
    }
  }