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