/*****************************************************************
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you 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 org.apache.cayenne.graph;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.Set;
/**
* A utility class that removes redundant and mutually exclusive graph changes from the
* graph diff.
*
* @since 3.0
*/
public class GraphDiffCompressor {
public GraphDiff compress(GraphDiff diff) {
if (diff.isNoop()) {
return diff;
}
CompressAction action = new CompressAction();
diff.apply(action);
return action.getCompressedDiff();
}
final class CompressAction implements GraphChangeHandler {
private List<GraphDiff> compressed = new ArrayList<>();
private Map<Object, List<NodeDiff>> diffsByNode = new HashMap<>();
private Set<Object> deletedNodes;
private Set<Object> createdNodes;
GraphDiff getCompressedDiff() {
// remove deleted nodes...
if (deletedNodes != null) {
for (Object nodeId : deletedNodes) {
Iterator<GraphDiff> it = compressed.iterator();
// if the node was inserted in the same transaction and later deleted,
// remove all its ops. Otherwise preserve arc ops (since delete rules
// depend on them), and delete operation itself.
// TODO: andrus 2008/02/04 - this doesn't take into account a
// possibility that a deleted node was re-inserted... Although I don't
// see how this could possibly happen with the present Cayenne API.
if (createdNodes != null && createdNodes.contains(nodeId)) {
while (it.hasNext()) {
NodeDiff diff = (NodeDiff) it.next();
if (nodeId.equals(diff.getNodeId())) {
it.remove();
}
}
}
else {
while (it.hasNext()) {
NodeDiff diff = (NodeDiff) it.next();
if (nodeId.equals(diff.getNodeId())) {
if (diff instanceof NodePropertyChangeOperation) {
it.remove();
}
}
}
}
}
}
return new CompoundDiff(compressed);
}
public void arcCreated(Object nodeId, Object targetNodeId, Object arcId) {
if (targetNodeId != null) {
List<NodeDiff> diffs = diffsByNode.get(nodeId);
if (diffs != null) {
for (int i = diffs.size() - 1; i >= 0; i--) {
NodeDiff diff = diffs.get(i);
if (diff instanceof ArcDeleteOperation) {
ArcDeleteOperation arcDiff = (ArcDeleteOperation) diff;
if (arcId.equals(arcDiff.getArcId())
&& targetNodeId.equals(arcDiff.targetNodeId)) {
diffs.remove(i);
compressed.remove(arcDiff);
return;
}
}
}
}
}
registerDiff(new ArcCreateOperation(nodeId, targetNodeId, arcId));
}
public void arcDeleted(Object nodeId, Object targetNodeId, Object arcId) {
if (targetNodeId != null) {
List<NodeDiff> diffs = diffsByNode.get(nodeId);
if (diffs != null) {
for (int i = diffs.size() - 1; i >= 0; i--) {
NodeDiff diff = diffs.get(i);
if (diff instanceof ArcCreateOperation) {
ArcCreateOperation arcDiff = (ArcCreateOperation) diff;
if (arcId.equals(arcDiff.getArcId())
&& targetNodeId.equals(arcDiff.targetNodeId)) {
diffs.remove(i);
compressed.remove(arcDiff);
return;
}
}
}
}
}
registerDiff(new ArcDeleteOperation(nodeId, targetNodeId, arcId));
}
public void nodeCreated(Object nodeId) {
registerDiff(new NodeCreateOperation(nodeId));
if (createdNodes == null) {
createdNodes = new HashSet<Object>();
}
createdNodes.add(nodeId);
}
public void nodeIdChanged(Object nodeId, Object newId) {
registerDiff(new NodeIdChangeOperation(nodeId, newId));
}
public void nodeRemoved(Object nodeId) {
registerDiff(new NodeDeleteOperation(nodeId));
if (deletedNodes == null) {
deletedNodes = new HashSet<Object>();
}
deletedNodes.add(nodeId);
}
public void nodePropertyChanged(
Object nodeId,
String property,
Object oldValue,
Object newValue) {
List<NodeDiff> diffs = diffsByNode.get(nodeId);
if (diffs != null) {
for (int i = diffs.size() - 1; i >= 0; i--) {
NodeDiff diff = diffs.get(i);
if (diff instanceof NodePropertyChangeOperation) {
NodePropertyChangeOperation propertyDiff = (NodePropertyChangeOperation) diff;
if (property.equals(propertyDiff.getProperty())) {
propertyDiff.setNewValue(newValue);
return;
}
}
}
}
registerDiff(new NodePropertyChangeOperation(
nodeId,
property,
oldValue,
newValue));
}
private void registerDiff(NodeDiff diff) {
compressed.add(diff);
List<NodeDiff> diffs = diffsByNode.get(diff.getNodeId());
if (diffs == null) {
diffs = new ArrayList<>();
diffsByNode.put(diff.getNodeId(), diffs);
}
diffs.add(diff);
}
}
}