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/*
* Copyright (C) 2014 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 com.google.common.annotations.Beta;
import com.google.common.base.Function;
import com.google.common.collect.ImmutableMap;
import com.google.common.collect.Maps;
import com.google.errorprone.annotations.CanIgnoreReturnValue;
import com.google.errorprone.annotations.Immutable;
import java.util.Map;
/**
* A {@link Network} whose elements and structural relationships will never change. Instances of
* this class may be obtained with {@link #copyOf(Network)}.
*
* See the Guava User's Guide's discussion
* of the {@code Immutable*} types for more information on the properties and guarantees
* provided by this class.
*
* @author James Sexton
* @author Joshua O'Madadhain
* @author Omar Darwish
* @author Jens Nyman
* @param Node parameter type
* @param Edge parameter type
* @since 20.0
*/
@Beta
@Immutable(containerOf = {"N", "E"})
@SuppressWarnings("Immutable") // Extends ConfigurableNetwork but uses ImmutableMaps.
public final class ImmutableNetwork extends ConfigurableNetwork {
private ImmutableNetwork(Network network) {
super(
NetworkBuilder.from(network), getNodeConnections(network), getEdgeToReferenceNode(network));
}
/** Returns an immutable copy of {@code network}. */
public static ImmutableNetwork copyOf(Network network) {
return (network instanceof ImmutableNetwork)
? (ImmutableNetwork) network
: new ImmutableNetwork(network);
}
/**
* Simply returns its argument.
*
* @deprecated no need to use this
*/
@Deprecated
public static ImmutableNetwork copyOf(ImmutableNetwork network) {
return checkNotNull(network);
}
@Override
public ImmutableGraph asGraph() {
return new ImmutableGraph(super.asGraph()); // safe because the view is effectively immutable
}
private static Map> getNodeConnections(Network network) {
// ImmutableMap.Builder maintains the order of the elements as inserted, so the map will have
// whatever ordering the network's nodes do, so ImmutableSortedMap is unnecessary even if the
// input nodes are sorted.
ImmutableMap.Builder> nodeConnections = ImmutableMap.builder();
for (N node : network.nodes()) {
nodeConnections.put(node, connectionsOf(network, node));
}
return nodeConnections.build();
}
private static Map getEdgeToReferenceNode(Network network) {
// ImmutableMap.Builder maintains the order of the elements as inserted, so the map will have
// whatever ordering the network's edges do, so ImmutableSortedMap is unnecessary even if the
// input edges are sorted.
ImmutableMap.Builder edgeToReferenceNode = ImmutableMap.builder();
for (E edge : network.edges()) {
edgeToReferenceNode.put(edge, network.incidentNodes(edge).nodeU());
}
return edgeToReferenceNode.build();
}
private static NetworkConnections connectionsOf(Network network, N node) {
if (network.isDirected()) {
Map inEdgeMap = Maps.asMap(network.inEdges(node), sourceNodeFn(network));
Map outEdgeMap = Maps.asMap(network.outEdges(node), targetNodeFn(network));
int selfLoopCount = network.edgesConnecting(node, node).size();
return network.allowsParallelEdges()
? DirectedMultiNetworkConnections.ofImmutable(inEdgeMap, outEdgeMap, selfLoopCount)
: DirectedNetworkConnections.ofImmutable(inEdgeMap, outEdgeMap, selfLoopCount);
} else {
Map incidentEdgeMap =
Maps.asMap(network.incidentEdges(node), adjacentNodeFn(network, node));
return network.allowsParallelEdges()
? UndirectedMultiNetworkConnections.ofImmutable(incidentEdgeMap)
: UndirectedNetworkConnections.ofImmutable(incidentEdgeMap);
}
}
private static Function sourceNodeFn(final Network network) {
return new Function() {
@Override
public N apply(E edge) {
return network.incidentNodes(edge).source();
}
};
}
private static Function targetNodeFn(final Network network) {
return new Function() {
@Override
public N apply(E edge) {
return network.incidentNodes(edge).target();
}
};
}
private static Function adjacentNodeFn(final Network network, final N node) {
return new Function() {
@Override
public N apply(E edge) {
return network.incidentNodes(edge).adjacentNode(node);
}
};
}
/**
* A builder for creating {@link ImmutableNetwork} instances, especially {@code static final}
* networks. Example:
*
* {@code
* static final ImmutableNetwork TRAIN_NETWORK =
* NetworkBuilder.undirected()
* .allowsParallelEdges(true)
* .immutable()
* .addEdge(PARIS, BRUSSELS, Thalys.trainNumber("1111"))
* .addEdge(PARIS, BRUSSELS, RegionalTrain.trainNumber("2222"))
* .addEdge(LONDON, PARIS, Eurostar.trainNumber("3333"))
* .addEdge(LONDON, BRUSSELS, Eurostar.trainNumber("4444"))
* .addNode(REYKJAVIK)
* .build();
* }
*
* Builder instances can be reused; it is safe to call {@link #build} multiple times to build
* multiple networks in series. Each new network contains all the elements of the ones created
* before it.
*
* @since 28.0
*/
public static class Builder {
private final MutableNetwork mutableNetwork;
Builder(NetworkBuilder networkBuilder) {
this.mutableNetwork = networkBuilder.build();
}
/**
* Adds {@code node} if it is not already present.
*
* Nodes must be unique, just as {@code Map} keys must be. They must also be non-null.
*
* @return this {@code Builder} object
*/
@CanIgnoreReturnValue
public ImmutableNetwork.Builder addNode(N node) {
mutableNetwork.addNode(node);
return this;
}
/**
* Adds {@code edge} connecting {@code nodeU} to {@code nodeV}.
*
* If the network is directed, {@code edge} will be directed in this network; otherwise, it
* will be undirected.
*
*
{@code edge} must be unique to this network, just as a {@code Map} key must be. It
* must also be non-null.
*
*
If {@code nodeU} and {@code nodeV} are not already present in this network, this method
* will silently {@link #addNode(Object) add} {@code nodeU} and {@code nodeV} to the network.
*
*
If {@code edge} already connects {@code nodeU} to {@code nodeV} (in the specified order if
* this network {@link #isDirected()}, else in any order), then this method will have no effect.
*
* @return this {@code Builder} object
* @throws IllegalArgumentException if {@code edge} already exists in the network and does not
* connect {@code nodeU} to {@code nodeV}
* @throws IllegalArgumentException if the introduction of the edge would violate {@link
* #allowsParallelEdges()} or {@link #allowsSelfLoops()}
*/
@CanIgnoreReturnValue
public ImmutableNetwork.Builder addEdge(N nodeU, N nodeV, E edge) {
mutableNetwork.addEdge(nodeU, nodeV, edge);
return this;
}
/**
* Adds {@code edge} connecting {@code endpoints}. In an undirected network, {@code edge} will
* also connect {@code nodeV} to {@code nodeU}.
*
* If this network is directed, {@code edge} will be directed in this network; if it is
* undirected, {@code edge} will be undirected in this network.
*
*
If this network is directed, {@code endpoints} must be ordered.
*
*
{@code edge} must be unique to this network, just as a {@code Map} key must be. It
* must also be non-null.
*
*
If either or both endpoints are not already present in this network, this method will
* silently {@link #addNode(Object) add} each missing endpoint to the network.
*
*
If {@code edge} already connects an endpoint pair equal to {@code endpoints}, then this
* method will have no effect.
*
* @return this {@code Builder} object
* @throws IllegalArgumentException if {@code edge} already exists in the network and connects
* some other endpoint pair that is not equal to {@code endpoints}
* @throws IllegalArgumentException if the introduction of the edge would violate {@link
* #allowsParallelEdges()} or {@link #allowsSelfLoops()}
* @throws IllegalArgumentException if the endpoints are unordered and the network is directed
*/
@CanIgnoreReturnValue
public ImmutableNetwork.Builder addEdge(EndpointPair endpoints, E edge) {
mutableNetwork.addEdge(endpoints, edge);
return this;
}
/**
* Returns a newly-created {@code ImmutableNetwork} based on the contents of this {@code
* Builder}.
*/
public ImmutableNetwork build() {
return ImmutableNetwork.copyOf(mutableNetwork);
}
}
}