001/*
002 * Copyright (C) 2016 The Guava Authors
003 *
004 * Licensed under the Apache License, Version 2.0 (the "License");
005 * you may not use this file except in compliance with the License.
006 * You may obtain a copy of the License at
007 *
008 * http://www.apache.org/licenses/LICENSE-2.0
009 *
010 * Unless required by applicable law or agreed to in writing, software
011 * distributed under the License is distributed on an "AS IS" BASIS,
012 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
013 * See the License for the specific language governing permissions and
014 * limitations under the License.
015 */
016
017package com.google.common.graph;
018
019import com.google.common.annotations.Beta;
020import com.google.common.base.Function;
021import com.google.common.collect.Maps;
022import java.util.Map;
023import java.util.Optional;
024import java.util.Set;
025import org.checkerframework.checker.nullness.compatqual.NullableDecl;
026
027/**
028 * This class provides a skeletal implementation of {@link ValueGraph}. It is recommended to extend
029 * this class rather than implement {@link ValueGraph} directly.
030 *
031 * <p>The methods implemented in this class should not be overridden unless the subclass admits a
032 * more efficient implementation.
033 *
034 * @author James Sexton
035 * @param <N> Node parameter type
036 * @param <V> Value parameter type
037 * @since 20.0
038 */
039@Beta
040public abstract class AbstractValueGraph<N, V> extends AbstractBaseGraph<N>
041    implements ValueGraph<N, V> {
042
043  @Override
044  public Graph<N> asGraph() {
045    return new AbstractGraph<N>() {
046      @Override
047      public Set<N> nodes() {
048        return AbstractValueGraph.this.nodes();
049      }
050
051      @Override
052      public Set<EndpointPair<N>> edges() {
053        return AbstractValueGraph.this.edges();
054      }
055
056      @Override
057      public boolean isDirected() {
058        return AbstractValueGraph.this.isDirected();
059      }
060
061      @Override
062      public boolean allowsSelfLoops() {
063        return AbstractValueGraph.this.allowsSelfLoops();
064      }
065
066      @Override
067      public ElementOrder<N> nodeOrder() {
068        return AbstractValueGraph.this.nodeOrder();
069      }
070
071      @Override
072      public Set<N> adjacentNodes(N node) {
073        return AbstractValueGraph.this.adjacentNodes(node);
074      }
075
076      @Override
077      public Set<N> predecessors(N node) {
078        return AbstractValueGraph.this.predecessors(node);
079      }
080
081      @Override
082      public Set<N> successors(N node) {
083        return AbstractValueGraph.this.successors(node);
084      }
085
086      @Override
087      public int degree(N node) {
088        return AbstractValueGraph.this.degree(node);
089      }
090
091      @Override
092      public int inDegree(N node) {
093        return AbstractValueGraph.this.inDegree(node);
094      }
095
096      @Override
097      public int outDegree(N node) {
098        return AbstractValueGraph.this.outDegree(node);
099      }
100    };
101  }
102
103  @Override
104  public Optional<V> edgeValue(N nodeU, N nodeV) {
105    return Optional.ofNullable(edgeValueOrDefault(nodeU, nodeV, null));
106  }
107
108  @Override
109  public final boolean equals(@NullableDecl Object obj) {
110    if (obj == this) {
111      return true;
112    }
113    if (!(obj instanceof ValueGraph)) {
114      return false;
115    }
116    ValueGraph<?, ?> other = (ValueGraph<?, ?>) obj;
117
118    return isDirected() == other.isDirected()
119        && nodes().equals(other.nodes())
120        && edgeValueMap(this).equals(edgeValueMap(other));
121  }
122
123  @Override
124  public final int hashCode() {
125    return edgeValueMap(this).hashCode();
126  }
127
128  /** Returns a string representation of this graph. */
129  @Override
130  public String toString() {
131    return "isDirected: "
132        + isDirected()
133        + ", allowsSelfLoops: "
134        + allowsSelfLoops()
135        + ", nodes: "
136        + nodes()
137        + ", edges: "
138        + edgeValueMap(this);
139  }
140
141  private static <N, V> Map<EndpointPair<N>, V> edgeValueMap(final ValueGraph<N, V> graph) {
142    Function<EndpointPair<N>, V> edgeToValueFn =
143        new Function<EndpointPair<N>, V>() {
144          @Override
145          public V apply(EndpointPair<N> edge) {
146            return graph.edgeValueOrDefault(edge.nodeU(), edge.nodeV(), null);
147          }
148        };
149    return Maps.asMap(graph.edges(), edgeToValueFn);
150  }
151}