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.checkArgument;
020import static com.google.common.base.Preconditions.checkNotNull;
021import static com.google.common.graph.Graphs.checkNonNegative;
022
023import com.google.common.annotations.Beta;
024import com.google.common.base.Optional;
025import com.google.errorprone.annotations.DoNotMock;
026
027/**
028 * A builder for constructing instances of {@link MutableGraph} or {@link ImmutableGraph} with
029 * user-defined properties.
030 *
031 * <p>A graph built by this class will have the following properties by default:
032 *
033 * <ul>
034 *   <li>does not allow self-loops
035 *   <li>orders {@link Graph#nodes()} in the order in which the elements were added
036 * </ul>
037 *
038 * <p>Examples of use:
039 *
040 * <pre>{@code
041 * // Building a mutable graph
042 * MutableGraph<String> graph = GraphBuilder.undirected().allowsSelfLoops(true).build();
043 * graph.putEdge("bread", "bread");
044 * graph.putEdge("chocolate", "peanut butter");
045 * graph.putEdge("peanut butter", "jelly");
046 *
047 * // Building an immutable graph
048 * ImmutableGraph<String> immutableGraph =
049 *     GraphBuilder.undirected()
050 *         .allowsSelfLoops(true)
051 *         .<String>immutable()
052 *         .putEdge("bread", "bread")
053 *         .putEdge("chocolate", "peanut butter")
054 *         .putEdge("peanut butter", "jelly")
055 *         .build();
056 * }</pre>
057 *
058 * @author James Sexton
059 * @author Joshua O'Madadhain
060 * @param <N> The most general node type this builder will support. This is normally {@code Object}
061 *     unless it is constrained by using a method like {@link #nodeOrder}, or the builder is
062 *     constructed based on an existing {@code Graph} using {@link #from(Graph)}.
063 * @since 20.0
064 */
065@Beta
066@DoNotMock
067public final class GraphBuilder<N> extends AbstractGraphBuilder<N> {
068
069  /** Creates a new instance with the specified edge directionality. */
070  private GraphBuilder(boolean directed) {
071    super(directed);
072  }
073
074  /** Returns a {@link GraphBuilder} for building directed graphs. */
075  public static GraphBuilder<Object> directed() {
076    return new GraphBuilder<>(true);
077  }
078
079  /** Returns a {@link GraphBuilder} for building undirected graphs. */
080  public static GraphBuilder<Object> undirected() {
081    return new GraphBuilder<>(false);
082  }
083
084  /**
085   * Returns a {@link GraphBuilder} initialized with all properties queryable from {@code graph}.
086   *
087   * <p>The "queryable" properties are those that are exposed through the {@link Graph} interface,
088   * such as {@link Graph#isDirected()}. Other properties, such as {@link #expectedNodeCount(int)},
089   * are not set in the new builder.
090   */
091  public static <N> GraphBuilder<N> from(Graph<N> graph) {
092    return new GraphBuilder<N>(graph.isDirected())
093        .allowsSelfLoops(graph.allowsSelfLoops())
094        .nodeOrder(graph.nodeOrder());
095    // TODO(b/142723300): Add incidentEdgeOrder
096  }
097
098  /**
099   * Returns an {@link ImmutableGraph.Builder} with the properties of this {@link GraphBuilder}.
100   *
101   * <p>The returned builder can be used for populating an {@link ImmutableGraph}.
102   *
103   * <p>Note that the returned builder will always have {@link #incidentEdgeOrder} set to {@link
104   * ElementOrder#stable()}, regardless of the value that was set in this builder.
105   *
106   * @since 28.0
107   */
108  public <N1 extends N> ImmutableGraph.Builder<N1> immutable() {
109    GraphBuilder<N1> castBuilder = cast();
110    return new ImmutableGraph.Builder<>(castBuilder);
111  }
112
113  /**
114   * Specifies whether the graph will allow self-loops (edges that connect a node to itself).
115   * Attempting to add a self-loop to a graph that does not allow them will throw an {@link
116   * UnsupportedOperationException}.
117   *
118   * <p>The default value is {@code false}.
119   */
120  public GraphBuilder<N> allowsSelfLoops(boolean allowsSelfLoops) {
121    this.allowsSelfLoops = allowsSelfLoops;
122    return this;
123  }
124
125  /**
126   * Specifies the expected number of nodes in the graph.
127   *
128   * @throws IllegalArgumentException if {@code expectedNodeCount} is negative
129   */
130  public GraphBuilder<N> expectedNodeCount(int expectedNodeCount) {
131    this.expectedNodeCount = Optional.of(checkNonNegative(expectedNodeCount));
132    return this;
133  }
134
135  /**
136   * Specifies the order of iteration for the elements of {@link Graph#nodes()}.
137   *
138   * <p>The default value is {@link ElementOrder#insertion() insertion order}.
139   */
140  public <N1 extends N> GraphBuilder<N1> nodeOrder(ElementOrder<N1> nodeOrder) {
141    GraphBuilder<N1> newBuilder = cast();
142    newBuilder.nodeOrder = checkNotNull(nodeOrder);
143    return newBuilder;
144  }
145
146  /**
147   * Specifies the order of iteration for the elements of {@link Graph#edges()}, {@link
148   * Graph#adjacentNodes(Object)}, {@link Graph#predecessors(Object)}, {@link
149   * Graph#successors(Object)} and {@link Graph#incidentEdges(Object)}.
150   *
151   * <p>The default value is {@link ElementOrder#unordered() unordered} for mutable graphs. For
152   * immutable graphs, this value is ignored; they always have a {@link ElementOrder#stable()
153   * stable} order.
154   *
155   * @throws IllegalArgumentException if {@code incidentEdgeOrder} is not either {@code
156   *     ElementOrder.unordered()} or {@code ElementOrder.stable()}.
157   */
158  // TODO(b/142723300): Make this method public
159  <N1 extends N> GraphBuilder<N1> incidentEdgeOrder(ElementOrder<N1> incidentEdgeOrder) {
160    checkArgument(
161        incidentEdgeOrder.type() == ElementOrder.Type.UNORDERED
162            || incidentEdgeOrder.type() == ElementOrder.Type.STABLE,
163        "The given elementOrder (%s) is unsupported. incidentEdgeOrder() only supports"
164            + " ElementOrder.unordered() and ElementOrder.stable().",
165        incidentEdgeOrder);
166    GraphBuilder<N1> newBuilder = cast();
167    newBuilder.incidentEdgeOrder = checkNotNull(incidentEdgeOrder);
168    return newBuilder;
169  }
170
171  /** Returns an empty {@link MutableGraph} with the properties of this {@link GraphBuilder}. */
172  public <N1 extends N> MutableGraph<N1> build() {
173    return new ConfigurableMutableGraph<N1>(this);
174  }
175
176  GraphBuilder<N> copy() {
177    GraphBuilder<N> newBuilder = new GraphBuilder<>(directed);
178    newBuilder.allowsSelfLoops = allowsSelfLoops;
179    newBuilder.nodeOrder = nodeOrder;
180    newBuilder.expectedNodeCount = expectedNodeCount;
181    newBuilder.incidentEdgeOrder = incidentEdgeOrder;
182    return newBuilder;
183  }
184
185  @SuppressWarnings("unchecked")
186  private <N1 extends N> GraphBuilder<N1> cast() {
187    return (GraphBuilder<N1>) this;
188  }
189}