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 com.google.common.base.Preconditions.checkNotNull;
020import static com.google.common.graph.Graphs.checkNonNegative;
021
022import com.google.common.annotations.Beta;
023import com.google.common.base.Optional;
024
025/**
026 * A builder for constructing instances of {@link MutableValueGraph} or {@link ImmutableValueGraph}
027 * with user-defined properties.
028 *
029 * <p>A graph built by this class will have the following properties by default:
030 *
031 * <ul>
032 *   <li>does not allow self-loops
033 *   <li>orders {@link Graph#nodes()} in the order in which the elements were added
034 * </ul>
035 *
036 * <p>Examples of use:
037 *
038 * <pre>{@code
039 * // Building a mutable value graph
040 * MutableValueGraph<String, Double> graph =
041 *     ValueGraphBuilder.undirected().allowsSelfLoops(true).build();
042 * graph.putEdgeValue("San Francisco", "San Francisco", 0.0);
043 * graph.putEdgeValue("San Jose", "San Jose", 0.0);
044 * graph.putEdgeValue("San Francisco", "San Jose", 48.4);
045 *
046 * // Building an immutable value graph
047 * ImmutableValueGraph<String, Double> immutableGraph =
048 *     ValueGraphBuilder.undirected()
049 *         .allowsSelfLoops(true)
050 *         .<String, Double>immutable()
051 *         .putEdgeValue("San Francisco", "San Francisco", 0.0)
052 *         .putEdgeValue("San Jose", "San Jose", 0.0)
053 *         .putEdgeValue("San Francisco", "San Jose", 48.4)
054 *         .build();
055 * }</pre>
056 *
057 * @author James Sexton
058 * @author Joshua O'Madadhain
059 * @param <N> The most general node type this builder will support. This is normally {@code Object}
060 *     unless it is constrained by using a method like {@link #nodeOrder}, or the builder is
061 *     constructed based on an existing {@code ValueGraph} using {@link #from(ValueGraph)}.
062 * @param <V> The most general value type this builder will support. This is normally {@code Object}
063 *     unless the builder is constructed based on an existing {@code Graph} using {@link
064 *     #from(ValueGraph)}.
065 * @since 20.0
066 */
067@Beta
068public final class ValueGraphBuilder<N, V> extends AbstractGraphBuilder<N> {
069
070  /** Creates a new instance with the specified edge directionality. */
071  private ValueGraphBuilder(boolean directed) {
072    super(directed);
073  }
074
075  /** Returns a {@link ValueGraphBuilder} for building directed graphs. */
076  public static ValueGraphBuilder<Object, Object> directed() {
077    return new ValueGraphBuilder<>(true);
078  }
079
080  /** Returns a {@link ValueGraphBuilder} for building undirected graphs. */
081  public static ValueGraphBuilder<Object, Object> undirected() {
082    return new ValueGraphBuilder<>(false);
083  }
084
085  /**
086   * Returns a {@link ValueGraphBuilder} initialized with all properties queryable from {@code
087   * graph}.
088   *
089   * <p>The "queryable" properties are those that are exposed through the {@link ValueGraph}
090   * interface, such as {@link ValueGraph#isDirected()}. Other properties, such as {@link
091   * #expectedNodeCount(int)}, are not set in the new builder.
092   */
093  public static <N, V> ValueGraphBuilder<N, V> from(ValueGraph<N, V> graph) {
094    return new ValueGraphBuilder<N, V>(graph.isDirected())
095        .allowsSelfLoops(graph.allowsSelfLoops())
096        .nodeOrder(graph.nodeOrder());
097  }
098
099  /**
100   * Returns an {@link ImmutableValueGraph.Builder} with the properties of this {@link
101   * ValueGraphBuilder}.
102   *
103   * <p>The returned builder can be used for populating an {@link ImmutableValueGraph}.
104   *
105   * @since 28.0
106   */
107  public <N1 extends N, V1 extends V> ImmutableValueGraph.Builder<N1, V1> immutable() {
108    ValueGraphBuilder<N1, V1> castBuilder = cast();
109    return new ImmutableValueGraph.Builder<>(castBuilder);
110  }
111
112  /**
113   * Specifies whether the graph will allow self-loops (edges that connect a node to itself).
114   * Attempting to add a self-loop to a graph that does not allow them will throw an {@link
115   * UnsupportedOperationException}.
116   *
117   * <p>The default value is {@code false}.
118   */
119  public ValueGraphBuilder<N, V> allowsSelfLoops(boolean allowsSelfLoops) {
120    this.allowsSelfLoops = allowsSelfLoops;
121    return this;
122  }
123
124  /**
125   * Specifies the expected number of nodes in the graph.
126   *
127   * @throws IllegalArgumentException if {@code expectedNodeCount} is negative
128   */
129  public ValueGraphBuilder<N, V> expectedNodeCount(int expectedNodeCount) {
130    this.expectedNodeCount = Optional.of(checkNonNegative(expectedNodeCount));
131    return this;
132  }
133
134  /**
135   * Specifies the order of iteration for the elements of {@link Graph#nodes()}.
136   *
137   * <p>The default value is {@link ElementOrder#insertion() insertion order}.
138   */
139  public <N1 extends N> ValueGraphBuilder<N1, V> nodeOrder(ElementOrder<N1> nodeOrder) {
140    ValueGraphBuilder<N1, V> newBuilder = cast();
141    newBuilder.nodeOrder = checkNotNull(nodeOrder);
142    return newBuilder;
143  }
144
145  /**
146   * Returns an empty {@link MutableValueGraph} with the properties of this {@link
147   * ValueGraphBuilder}.
148   */
149  public <N1 extends N, V1 extends V> MutableValueGraph<N1, V1> build() {
150    return new ConfigurableMutableValueGraph<>(this);
151  }
152
153  @SuppressWarnings("unchecked")
154  private <N1 extends N, V1 extends V> ValueGraphBuilder<N1, V1> cast() {
155    return (ValueGraphBuilder<N1, V1>) this;
156  }
157}