/*
* 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.graph.GraphConstants.GRAPH_STRING_FORMAT;
import static com.google.common.graph.GraphConstants.MULTIPLE_EDGES_CONNECTING;
import com.google.common.annotations.Beta;
import com.google.common.base.Function;
import com.google.common.base.Optional;
import com.google.common.collect.ImmutableSet;
import com.google.common.collect.Iterators;
import com.google.common.collect.Maps;
import com.google.common.collect.Sets;
import com.google.common.math.IntMath;
import java.util.AbstractSet;
import java.util.Iterator;
import java.util.Map;
import java.util.Set;
import javax.annotation.Nullable;
/**
* This class provides a skeletal implementation of {@link Network}. It is recommended to extend
* this class rather than implement {@link Network} directly.
*
* @author James Sexton
* @param <N> Node parameter type
* @param <E> Edge parameter type
* @since 20.0
*/
@Beta
public abstract class AbstractNetwork<N, E> implements Network<N, E> {
@Override
public Graph<N> asGraph() {
return new AbstractGraph<N>() {
@Override
public Set<N> nodes() {
return AbstractNetwork.this.nodes();
}
@Override
public Set<EndpointPair<N>> edges() {
if (allowsParallelEdges()) {
return super.edges(); // Defer to AbstractGraph implementation.
}
// Optimized implementation assumes no parallel edges (1:1 edge to EndpointPair mapping).
return new AbstractSet<EndpointPair<N>>() {
@Override
public Iterator<EndpointPair<N>> iterator() {
return Iterators.transform(
AbstractNetwork.this.edges().iterator(),
new Function<E, EndpointPair<N>>() {
@Override
public EndpointPair<N> apply(E edge) {
return incidentNodes(edge);
}
});
}
@Override
public int size() {
return AbstractNetwork.this.edges().size();
}
// Mostly safe: We check contains(u) before calling successors(u), so we perform unsafe
// operations only in weird cases like checking for an EndpointPair<ArrayList> in a
// Network<LinkedList>.
@SuppressWarnings("unchecked")
@Override
public boolean contains(@Nullable Object obj) {
if (!(obj instanceof EndpointPair)) {
return false;
}
EndpointPair<?> endpointPair = (EndpointPair<?>) obj;
return isDirected() == endpointPair.isOrdered()
&& nodes().contains(endpointPair.nodeU())
&& successors((N) endpointPair.nodeU()).contains(endpointPair.nodeV());
}
};
}
@Override
public ElementOrder<N> nodeOrder() {
return AbstractNetwork.this.nodeOrder();
}
@Override
public boolean isDirected() {
return AbstractNetwork.this.isDirected();
}
@Override
public boolean allowsSelfLoops() {
return AbstractNetwork.this.allowsSelfLoops();
}
@Override
public Set<N> adjacentNodes(N node) {
return AbstractNetwork.this.adjacentNodes(node);
}
@Override
public Set<N> predecessors(N node) {
return AbstractNetwork.this.predecessors(node);
}
@Override
public Set<N> successors(N node) {
return AbstractNetwork.this.successors(node);
}
// DO NOT override the AbstractGraph *degree() implementations.
};
}
@Override
public int degree(N node) {
if (isDirected()) {
return IntMath.saturatedAdd(inEdges(node).size(), outEdges(node).size());
} else {
return IntMath.saturatedAdd(incidentEdges(node).size(), edgesConnecting(node, node).size());
}
}
@Override
public int inDegree(N node) {
return isDirected() ? inEdges(node).size() : degree(node);
}
@Override
public int outDegree(N node) {
return isDirected() ? outEdges(node).size() : degree(node);
}
@Override
public Set<E> adjacentEdges(E edge) {
EndpointPair<N> endpointPair = incidentNodes(edge); // Verifies that edge is in this network.
Set<E> endpointPairIncidentEdges =
Sets.union(incidentEdges(endpointPair.nodeU()), incidentEdges(endpointPair.nodeV()));
return Sets.difference(endpointPairIncidentEdges, ImmutableSet.of(edge));
}
@Override
public Optional<E> edgeConnecting(N nodeU, N nodeV) {
Set<E> edgesConnecting = edgesConnecting(nodeU, nodeV);
switch (edgesConnecting.size()) {
case 0:
return Optional.absent();
case 1:
return Optional.of(edgesConnecting.iterator().next());
default:
throw new IllegalArgumentException(String.format(MULTIPLE_EDGES_CONNECTING, nodeU, nodeV));
}
}
@Override
public final boolean equals(@Nullable Object obj) {
if (obj == this) {
return true;
}
if (!(obj instanceof Network)) {
return false;
}
Network<?, ?> other = (Network<?, ?>) obj;
return isDirected() == other.isDirected()
&& nodes().equals(other.nodes())
&& edgeIncidentNodesMap(this).equals(edgeIncidentNodesMap(other));
}
@Override
public final int hashCode() {
return edgeIncidentNodesMap(this).hashCode();
}
/** Returns a string representation of this network. */
@Override
public String toString() {
String propertiesString =
String.format(
"isDirected: %s, allowsParallelEdges: %s, allowsSelfLoops: %s",
isDirected(), allowsParallelEdges(), allowsSelfLoops());
return String.format(
GRAPH_STRING_FORMAT, propertiesString, nodes(), edgeIncidentNodesMap(this));
}
private static <N, E> Map<E, EndpointPair<N>> edgeIncidentNodesMap(final Network<N, E> network) {
Function<E, EndpointPair<N>> edgeToIncidentNodesFn =
new Function<E, EndpointPair<N>>() {
@Override
public EndpointPair<N> apply(E edge) {
return network.incidentNodes(edge);
}
};
return Maps.asMap(network.edges(), edgeToIncidentNodesFn);
}
}