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/*
 * Copyright (C) 2016 The Guava Authors
 *
 * Licensed 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 com.google.common.graph;

import static com.google.common.base.Preconditions.checkNotNull;
import static com.google.common.graph.Graphs.checkNonNegative;

import com.google.common.annotations.Beta;
import com.google.common.base.Optional;

/**
 * A builder for constructing instances of {@link MutableValueGraph} with user-defined properties.
 *
 * A graph built by this class will have the following properties by default:
 *
 * 

 *   does not allow self-loops
 *   
orders {@link Graph#nodes()} in the order in which the elements were added
 * 
 *
 * Example of use:
 *
 * 
{@code
 * MutableValueGraph graph =
 *     ValueGraphBuilder.undirected().allowsSelfLoops(true).build();
 * graph.putEdgeValue("San Francisco", "San Francisco", 0.0);
 * graph.putEdgeValue("San Jose", "San Jose", 0.0);
 * graph.putEdgeValue("San Francisco", "San Jose", 48.4);
 * }
 *
 * @author James Sexton
 * @author Joshua O'Madadhain
 * @param  The most general node type this builder will support. This is normally {@code Object}
 *     unless it is constrained by using a method like {@link #nodeOrder}, or the builder is
 *     constructed based on an existing {@code ValueGraph} using {@link #from(ValueGraph)}.
 * @param  The most general value type this builder will support. This is normally {@code Object}
 *     unless the builder is constructed based on an existing {@code Graph} using {@link
 *     #from(ValueGraph)}.
 * @since 20.0
 */
@Beta
public final class ValueGraphBuilder extends AbstractGraphBuilder {

  /** Creates a new instance with the specified edge directionality. */
  private ValueGraphBuilder(boolean directed) {
    super(directed);
  }

  /** Returns a {@link ValueGraphBuilder} for building directed graphs. */
  public static ValueGraphBuilder directed() {
    return new ValueGraphBuilder<>(true);
  }

  /** Returns a {@link ValueGraphBuilder} for building undirected graphs. */
  public static ValueGraphBuilder undirected() {
    return new ValueGraphBuilder<>(false);
  }

  /**
   * Returns a {@link ValueGraphBuilder} initialized with all properties queryable from {@code
   * graph}.
   *
   * The "queryable" properties are those that are exposed through the {@link ValueGraph}
   * interface, such as {@link ValueGraph#isDirected()}. Other properties, such as {@link
   * #expectedNodeCount(int)}, are not set in the new builder.
   */
  public static  ValueGraphBuilder from(ValueGraph graph) {
    return new ValueGraphBuilder(graph.isDirected())
        .allowsSelfLoops(graph.allowsSelfLoops())
        .nodeOrder(graph.nodeOrder());
  }

  /**
   * Specifies whether the graph will allow self-loops (edges that connect a node to itself).
   * Attempting to add a self-loop to a graph that does not allow them will throw an {@link
   * UnsupportedOperationException}.
   */
  public ValueGraphBuilder allowsSelfLoops(boolean allowsSelfLoops) {
    this.allowsSelfLoops = allowsSelfLoops;
    return this;
  }

  /**
   * Specifies the expected number of nodes in the graph.
   *
   * @throws IllegalArgumentException if {@code expectedNodeCount} is negative
   */
  public ValueGraphBuilder expectedNodeCount(int expectedNodeCount) {
    this.expectedNodeCount = Optional.of(checkNonNegative(expectedNodeCount));
    return this;
  }

  /** Specifies the order of iteration for the elements of {@link Graph#nodes()}. */
  public  ValueGraphBuilder nodeOrder(ElementOrder nodeOrder) {
    ValueGraphBuilder newBuilder = cast();
    newBuilder.nodeOrder = checkNotNull(nodeOrder);
    return newBuilder;
  }

  /**
   * Returns an empty {@link MutableValueGraph} with the properties of this {@link
   * ValueGraphBuilder}.
   */
  public  MutableValueGraph build() {
    return new ConfigurableMutableValueGraph<>(this);
  }

  @SuppressWarnings("unchecked")
  private  ValueGraphBuilder cast() {
    return (ValueGraphBuilder) this;
  }
}