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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.checkArgument;
import static com.google.common.base.Preconditions.checkNotNull;
import static com.google.common.base.Preconditions.checkState;
import static com.google.common.graph.GraphConstants.SELF_LOOPS_NOT_ALLOWED;
import static com.google.common.graph.Graphs.checkNonNegative;
import static com.google.common.graph.Graphs.checkPositive;
import static java.util.Objects.requireNonNull;
import com.google.common.collect.ImmutableList;
import com.google.errorprone.annotations.CanIgnoreReturnValue;
import javax.annotation.CheckForNull;
/**
* Standard implementation of {@link MutableValueGraph} that supports both directed and undirected
* graphs. Instances of this class should be constructed with {@link ValueGraphBuilder}.
*
* Time complexities for mutation methods are all O(1) except for {@code removeNode(N node)},
* which is in O(d_node) where d_node is the degree of {@code node}.
*
* @author James Sexton
* @author Joshua O'Madadhain
* @author Omar Darwish
* @param Node parameter type
* @param Value parameter type
*/
@ElementTypesAreNonnullByDefault
final class StandardMutableValueGraph extends StandardValueGraph
implements MutableValueGraph {
private final ElementOrder incidentEdgeOrder;
/** Constructs a mutable graph with the properties specified in {@code builder}. */
StandardMutableValueGraph(AbstractGraphBuilder builder) {
super(builder);
incidentEdgeOrder = builder.incidentEdgeOrder.cast();
}
@Override
public ElementOrder incidentEdgeOrder() {
return incidentEdgeOrder;
}
@Override
@CanIgnoreReturnValue
public boolean addNode(N node) {
checkNotNull(node, "node");
if (containsNode(node)) {
return false;
}
addNodeInternal(node);
return true;
}
/**
* Adds {@code node} to the graph and returns the associated {@link GraphConnections}.
*
* @throws IllegalStateException if {@code node} is already present
*/
@CanIgnoreReturnValue
private GraphConnections addNodeInternal(N node) {
GraphConnections connections = newConnections();
checkState(nodeConnections.put(node, connections) == null);
return connections;
}
@Override
@CanIgnoreReturnValue
@CheckForNull
public V putEdgeValue(N nodeU, N nodeV, V value) {
checkNotNull(nodeU, "nodeU");
checkNotNull(nodeV, "nodeV");
checkNotNull(value, "value");
if (!allowsSelfLoops()) {
checkArgument(!nodeU.equals(nodeV), SELF_LOOPS_NOT_ALLOWED, nodeU);
}
GraphConnections connectionsU = nodeConnections.get(nodeU);
if (connectionsU == null) {
connectionsU = addNodeInternal(nodeU);
}
V previousValue = connectionsU.addSuccessor(nodeV, value);
GraphConnections connectionsV = nodeConnections.get(nodeV);
if (connectionsV == null) {
connectionsV = addNodeInternal(nodeV);
}
connectionsV.addPredecessor(nodeU, value);
if (previousValue == null) {
checkPositive(++edgeCount);
}
return previousValue;
}
@Override
@CanIgnoreReturnValue
@CheckForNull
public V putEdgeValue(EndpointPair endpoints, V value) {
validateEndpoints(endpoints);
return putEdgeValue(endpoints.nodeU(), endpoints.nodeV(), value);
}
@Override
@CanIgnoreReturnValue
public boolean removeNode(N node) {
checkNotNull(node, "node");
GraphConnections connections = nodeConnections.get(node);
if (connections == null) {
return false;
}
if (allowsSelfLoops()) {
// Remove self-loop (if any) first, so we don't get CME while removing incident edges.
if (connections.removeSuccessor(node) != null) {
connections.removePredecessor(node);
--edgeCount;
}
}
for (N successor : ImmutableList.copyOf(connections.successors())) {
// requireNonNull is safe because the node is a successor.
requireNonNull(nodeConnections.getWithoutCaching(successor)).removePredecessor(node);
requireNonNull(connections.removeSuccessor(successor));
--edgeCount;
}
if (isDirected()) { // In undirected graphs, the successor and predecessor sets are equal.
// Since views are returned, we need to copy the predecessors that will be removed.
// Thus we avoid modifying the underlying view while iterating over it.
for (N predecessor : ImmutableList.copyOf(connections.predecessors())) {
// requireNonNull is safe because the node is a predecessor.
checkState(
requireNonNull(nodeConnections.getWithoutCaching(predecessor)).removeSuccessor(node)
!= null);
connections.removePredecessor(predecessor);
--edgeCount;
}
}
nodeConnections.remove(node);
checkNonNegative(edgeCount);
return true;
}
@Override
@CanIgnoreReturnValue
@CheckForNull
public V removeEdge(N nodeU, N nodeV) {
checkNotNull(nodeU, "nodeU");
checkNotNull(nodeV, "nodeV");
GraphConnections connectionsU = nodeConnections.get(nodeU);
GraphConnections connectionsV = nodeConnections.get(nodeV);
if (connectionsU == null || connectionsV == null) {
return null;
}
V previousValue = connectionsU.removeSuccessor(nodeV);
if (previousValue != null) {
connectionsV.removePredecessor(nodeU);
checkNonNegative(--edgeCount);
}
return previousValue;
}
@Override
@CanIgnoreReturnValue
@CheckForNull
public V removeEdge(EndpointPair endpoints) {
validateEndpoints(endpoints);
return removeEdge(endpoints.nodeU(), endpoints.nodeV());
}
private GraphConnections newConnections() {
return isDirected()
? DirectedGraphConnections.of(incidentEdgeOrder)
: UndirectedGraphConnections.of(incidentEdgeOrder);
}
}