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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 StandardNetwork but uses ImmutableMaps. @ElementTypesAreNonnullByDefault public final class ImmutableNetwork extends StandardNetwork { 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.buildOrThrow(); } 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.buildOrThrow(); } 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(Network network) { return (E edge) -> network.incidentNodes(edge).source(); } private static Function targetNodeFn(Network network) { return (E edge) -> network.incidentNodes(edge).target(); } private static Function adjacentNodeFn(Network network, N node) { return (E edge) -> 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); } } }





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