001package org.cpsolver.ifs.assignment.context;
002
003import org.cpsolver.ifs.assignment.Assignment;
004import org.cpsolver.ifs.assignment.InheritedAssignment;
005import org.cpsolver.ifs.model.Value;
006import org.cpsolver.ifs.model.Variable;
007
008/**
009 * A variant of the {@link AssignmentContextHolderMap} that is used by the {@link InheritedAssignment}
010 * class. If a {@link HasAssignmentContext} class implements the {@link CanInheritContext} interface, 
011 * this class will use the {@link CanInheritContext#inheritAssignmentContext(Assignment, AssignmentContext)} method 
012 * instead of the {@link HasAssignmentContext#createAssignmentContext(Assignment)} method to create
013 * a new context.   
014 * 
015 * @see HasAssignmentContext
016 * @see InheritedAssignment
017 * @see CanInheritContext
018 * 
019 * @author  Tomáš Müller
020 * @version IFS 1.3 (Iterative Forward Search)<br>
021 *          Copyright (C) 2014 Tomáš Müller<br>
022 *          <a href="mailto:muller@unitime.org">muller@unitime.org</a><br>
023 *          <a href="http://muller.unitime.org">http://muller.unitime.org</a><br>
024 * <br>
025 *          This library is free software; you can redistribute it and/or modify
026 *          it under the terms of the GNU Lesser General Public License as
027 *          published by the Free Software Foundation; either version 3 of the
028 *          License, or (at your option) any later version. <br>
029 * <br>
030 *          This library is distributed in the hope that it will be useful, but
031 *          WITHOUT ANY WARRANTY; without even the implied warranty of
032 *          MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
033 *          Lesser General Public License for more details. <br>
034 * <br>
035 *          You should have received a copy of the GNU Lesser General Public
036 *          License along with this library; if not see <a href='http://www.gnu.org/licenses'>http://www.gnu.org/licenses</a>.
037 * @param <V> Variable
038 * @param <T> Value
039 **/
040public class InheritedAssignmentContextHolder<V extends Variable<V, T>, T extends Value<V, T>> extends DefaultParallelAssignmentContextHolder<V, T> {
041    private long iVersion;
042    
043    public InheritedAssignmentContextHolder(int index, long version) {
044        super(index);
045        iVersion = version;
046    }
047
048    /**
049     * If the {@link AssignmentContextReference#getParent()} implements the {@link CanInheritContext} interface, this 
050     * method will use the {@link CanInheritContext#inheritAssignmentContext(Assignment, AssignmentContext)} instead of the
051     * {@link HasAssignmentContext#createAssignmentContext(Assignment)} to create a new context. 
052     * @param assignment current assignment (must be {@link InheritedAssignment})
053     * @param reference assignment context reference
054     * @return assignment context for the given assignment and reference
055     */
056    @Override
057    @SuppressWarnings("unchecked")
058    public <U extends AssignmentContext> U getAssignmentContext(Assignment<V, T> assignment, AssignmentContextReference<V, T, U> reference) {
059        if (iIndex >= 0 && iIndex < CanHoldContext.sMaxSize && reference.getParent() instanceof CanHoldContext) {
060            AssignmentContext[] contexts = ((CanHoldContext)reference.getParent()).getContext();
061
062            VersionedContext<U> context = (VersionedContext<U>)contexts[iIndex];
063            if (context == null) {
064                context = new VersionedContext<U>();
065                if (reference.getParent() instanceof CanInheritContext)
066                    context.setContent(((CanInheritContext<V, T, U>)reference.getParent()).inheritAssignmentContext(assignment,
067                            ((InheritedAssignment<V, T>)assignment).getParentAssignment().getAssignmentContext(reference)), iVersion);
068                else
069                    context.setContent(reference.getParent().createAssignmentContext(assignment), iVersion);
070                contexts[iIndex] = context;
071            } else if (!context.isCurrent(iVersion)) {
072                if (reference.getParent() instanceof CanInheritContext)
073                    context.setContent(((CanInheritContext<V, T, U>)reference.getParent()).inheritAssignmentContext(assignment,
074                            ((InheritedAssignment<V, T>)assignment).getParentAssignment().getAssignmentContext(reference)), iVersion);
075                else
076                    context.setContent(reference.getParent().createAssignmentContext(assignment), iVersion);
077            }
078            
079            return context.getContent();
080        } else {
081            U context = (U) iContexts.get(reference.getIndex());
082            if (context != null) return context;
083            
084            if (reference.getParent() instanceof CanInheritContext)
085                context = ((CanInheritContext<V, T, U>)reference.getParent()).inheritAssignmentContext(assignment,
086                        ((InheritedAssignment<V, T>)assignment).getParentAssignment().getAssignmentContext(reference));
087            else
088                context = reference.getParent().createAssignmentContext(assignment);
089            iContexts.put(reference.getIndex(), context);
090            
091            return context;
092        }
093    }
094    
095    public static class VersionedContext<U extends AssignmentContext> implements AssignmentContext {
096        U iContent = null;
097        long iContentVersion = -1;
098        
099        VersionedContext() {}
100        
101        public U getContent() {
102            return iContent;
103        }
104        
105        public void setContent(U content, long version) {
106            iContent = content;
107            iContentVersion = version;
108        }
109        
110        public boolean isCurrent(long version) {
111            return iContentVersion == version;
112        }
113    }
114}