/**
* Copyright 2005 JBoss Inc
*
* 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 org.drools.conflict;
import org.drools.common.InternalFactHandle;
import org.drools.spi.Activation;
import org.drools.spi.ConflictResolver;
/**
* <code>ConflictResolver</code> that uses the mostRecentFactTimeStamp of
* rules to resolve conflict.
*
* @see #getInstance
* @see org.drools.spi.Tuple#getMostRecentFactTimeStamp
*
* @author <a href="mailto:bob@werken.com">bob mcwhirter </a>
* @author <a href="mailto:simon@redhillconsulting.com.au">Simon Harris </a>
*/
public class RecencyConflictResolver extends AbstractConflictResolver {
// ----------------------------------------------------------------------
// Class members
// ----------------------------------------------------------------------
/**
*
*/
private static final long serialVersionUID = 510l;
/** Singleton instance. */
private static final RecencyConflictResolver INSTANCE = new RecencyConflictResolver();
// ----------------------------------------------------------------------
// Class methods
// ----------------------------------------------------------------------
/**
* Retrieve the singleton instance.
*
* @return The singleton instance.
*/
public static ConflictResolver getInstance() {
return RecencyConflictResolver.INSTANCE;
}
// ----------------------------------------------------------------------
// Constructors
// ----------------------------------------------------------------------
/**
* Construct.
*/
public RecencyConflictResolver() {
// intentionally left blank
}
// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
/**
* @see ConflictResolver
*/
public int compare(final Activation lhs,
final Activation rhs) {
final InternalFactHandle[] lFacts = lhs.getTuple().getFactHandles();
final InternalFactHandle[] rFacts = rhs.getTuple().getFactHandles();
InternalFactHandle leftMostRecent = getMostRecentFact( lFacts );
InternalFactHandle rightMostRecent = getMostRecentFact( rFacts );
final int lastIndex = (lFacts.length < rFacts.length) ? lFacts.length : rFacts.length;
if ( leftMostRecent.getRecency() == rightMostRecent.getRecency() && lastIndex > 1 ) {
for ( int i = 0; i < lastIndex; i++ ) {
leftMostRecent = getMostRecentFact( lFacts,
leftMostRecent );
rightMostRecent = getMostRecentFact( rFacts,
rightMostRecent );
if ( leftMostRecent == null || rightMostRecent == null ) {
if ( leftMostRecent == null && rightMostRecent != null ) {
return (int) rightMostRecent.getRecency();
}
} else if ( leftMostRecent.getRecency() != rightMostRecent.getRecency() ) {
return (int) (rightMostRecent.getRecency() - leftMostRecent.getRecency());
}
}
} else {
return (int) (rightMostRecent.getRecency() - leftMostRecent.getRecency());
}
return rFacts.length - lFacts.length;
}
private InternalFactHandle getMostRecentFact(final InternalFactHandle[] handles) {
InternalFactHandle mostRecent = handles[0];
for ( int i = 1; i < handles.length; i++ ) {
final InternalFactHandle eachHandle = handles[i];
if ( eachHandle.getRecency() > mostRecent.getRecency() ) {
mostRecent = eachHandle;
}
}
return mostRecent;
}
private InternalFactHandle getMostRecentFact(final InternalFactHandle[] handles,
final InternalFactHandle handle) {
InternalFactHandle mostRecent = null;
for ( int i = 0; i < handles.length; i++ ) {
final InternalFactHandle eachHandle = handles[i];
if ( mostRecent == null && eachHandle.getRecency() < handle.getRecency() ) {
mostRecent = eachHandle;
}
if ( mostRecent != null && eachHandle.getRecency() > mostRecent.getRecency() && eachHandle.getRecency() < handle.getRecency() ) {
mostRecent = eachHandle;
}
}
return mostRecent;
}
}