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 static java.util.Objects.requireNonNull;
020
021import com.google.common.annotations.Beta;
022import com.google.common.collect.Maps;
023import java.util.Map;
024import java.util.Optional;
025import java.util.Set;
026import javax.annotation.CheckForNull;
027
028/**
029 * This class provides a skeletal implementation of {@link ValueGraph}. It is recommended to extend
030 * this class rather than implement {@link ValueGraph} directly.
031 *
032 * <p>The methods implemented in this class should not be overridden unless the subclass admits a
033 * more efficient implementation.
034 *
035 * @author James Sexton
036 * @param <N> Node parameter type
037 * @param <V> Value parameter type
038 * @since 20.0
039 */
040@Beta
041@ElementTypesAreNonnullByDefault
042public abstract class AbstractValueGraph<N, V> extends AbstractBaseGraph<N>
043    implements ValueGraph<N, V> {
044
045  @Override
046  public Graph<N> asGraph() {
047    return new AbstractGraph<N>() {
048      @Override
049      public Set<N> nodes() {
050        return AbstractValueGraph.this.nodes();
051      }
052
053      @Override
054      public Set<EndpointPair<N>> edges() {
055        return AbstractValueGraph.this.edges();
056      }
057
058      @Override
059      public boolean isDirected() {
060        return AbstractValueGraph.this.isDirected();
061      }
062
063      @Override
064      public boolean allowsSelfLoops() {
065        return AbstractValueGraph.this.allowsSelfLoops();
066      }
067
068      @Override
069      public ElementOrder<N> nodeOrder() {
070        return AbstractValueGraph.this.nodeOrder();
071      }
072
073      @Override
074      public ElementOrder<N> incidentEdgeOrder() {
075        return AbstractValueGraph.this.incidentEdgeOrder();
076      }
077
078      @Override
079      public Set<N> adjacentNodes(N node) {
080        return AbstractValueGraph.this.adjacentNodes(node);
081      }
082
083      @Override
084      public Set<N> predecessors(N node) {
085        return AbstractValueGraph.this.predecessors(node);
086      }
087
088      @Override
089      public Set<N> successors(N node) {
090        return AbstractValueGraph.this.successors(node);
091      }
092
093      @Override
094      public int degree(N node) {
095        return AbstractValueGraph.this.degree(node);
096      }
097
098      @Override
099      public int inDegree(N node) {
100        return AbstractValueGraph.this.inDegree(node);
101      }
102
103      @Override
104      public int outDegree(N node) {
105        return AbstractValueGraph.this.outDegree(node);
106      }
107    };
108  }
109
110  @Override
111  public Optional<V> edgeValue(N nodeU, N nodeV) {
112    return Optional.ofNullable(edgeValueOrDefault(nodeU, nodeV, null));
113  }
114
115  @Override
116  public Optional<V> edgeValue(EndpointPair<N> endpoints) {
117    return Optional.ofNullable(edgeValueOrDefault(endpoints, null));
118  }
119
120  @Override
121  public final boolean equals(@CheckForNull Object obj) {
122    if (obj == this) {
123      return true;
124    }
125    if (!(obj instanceof ValueGraph)) {
126      return false;
127    }
128    ValueGraph<?, ?> other = (ValueGraph<?, ?>) obj;
129
130    return isDirected() == other.isDirected()
131        && nodes().equals(other.nodes())
132        && edgeValueMap(this).equals(edgeValueMap(other));
133  }
134
135  @Override
136  public final int hashCode() {
137    return edgeValueMap(this).hashCode();
138  }
139
140  /** Returns a string representation of this graph. */
141  @Override
142  public String toString() {
143    return "isDirected: "
144        + isDirected()
145        + ", allowsSelfLoops: "
146        + allowsSelfLoops()
147        + ", nodes: "
148        + nodes()
149        + ", edges: "
150        + edgeValueMap(this);
151  }
152
153  private static <N, V> Map<EndpointPair<N>, V> edgeValueMap(final ValueGraph<N, V> graph) {
154    return Maps.asMap(
155        graph.edges(),
156        edge ->
157            // requireNonNull is safe because the endpoint pair comes from the graph.
158            requireNonNull(graph.edgeValueOrDefault(edge.nodeU(), edge.nodeV(), null)));
159  }
160}