001package org.cpsolver.ifs.assignment.context;
002
003import org.cpsolver.ifs.assignment.Assignment;
004import org.cpsolver.ifs.model.Model;
005import org.cpsolver.ifs.model.Value;
006import org.cpsolver.ifs.model.Variable;
007
008/**
009 * A reference to an assignment context. A reference is created by a class requiring an assignment
010 * context {@link HasAssignmentContext} by calling {@link Model#createReference(HasAssignmentContext)}.
011 * This reference can be stored with the class implementing the {@link HasAssignmentContext}
012 * interface in place of the assignment context {@link AssignmentContext}. Assignment context
013 * can be than retrieved from an assignment by calling {@link Assignment#getAssignmentContext(AssignmentContextReference)}.
014 * This method also create a new context if there is none associated with the assignment yet for
015 * the given reference.
016 * 
017 * <br><br>
018 * 
019 * Method {@link AssignmentContextReference#getIndex()} can be used to index stored contexts. 
020 * A new assignment context can be created for a reference by calling {@link HasAssignmentContext#createAssignmentContext(Assignment)}
021 * on the {@link AssignmentContextReference#getParent()}.
022 * 
023 * @see AssignmentContext
024 * @see AssignmentContextReference
025 * @see HasAssignmentContext
026 * 
027 * @author  Tomáš Müller
028 * @version IFS 1.3 (Iterative Forward Search)<br>
029 *          Copyright (C) 2014 Tomáš Müller<br>
030 *          <a href="mailto:muller@unitime.org">muller@unitime.org</a><br>
031 *          <a href="http://muller.unitime.org">http://muller.unitime.org</a><br>
032 * <br>
033 *          This library is free software; you can redistribute it and/or modify
034 *          it under the terms of the GNU Lesser General Public License as
035 *          published by the Free Software Foundation; either version 3 of the
036 *          License, or (at your option) any later version. <br>
037 * <br>
038 *          This library is distributed in the hope that it will be useful, but
039 *          WITHOUT ANY WARRANTY; without even the implied warranty of
040 *          MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
041 *          Lesser General Public License for more details. <br>
042 * <br>
043 *          You should have received a copy of the GNU Lesser General Public
044 *          License along with this library; if not see <a href='http://www.gnu.org/licenses'>http://www.gnu.org/licenses</a>.
045 * @param <V> Variable
046 * @param <T> Value
047 * @param <C> Assignment Context
048 **/
049public class AssignmentContextReference <V extends Variable<V, T>, T extends Value<V, T>, C extends AssignmentContext> {
050    private HasAssignmentContext<V, T, C> iParent;
051    private int iIndex;
052
053    /**
054     * Create a reference context
055     * @param parent a class implementing the {@link HasAssignmentContext} interface
056     * @param index a unique index associated with the reference by the {@link Model}
057     **/
058    public AssignmentContextReference(HasAssignmentContext<V, T, C> parent, int index) {
059        iParent = parent;
060        iIndex = index;
061    }
062    
063    /**
064     * Return index, a unique number associated with the reference by the {@link Model}.
065     * @return an index
066     */
067    public int getIndex() {
068        return iIndex;
069    }
070    
071    @Override
072    public int hashCode() {
073        return iIndex;
074    }
075    
076    @Override
077    public boolean equals(Object o) {
078        if (o == null || !(o instanceof AssignmentContextReference<?,?,?>))
079            return false;
080        return getIndex() == ((AssignmentContextReference<?,?,?>)o).getIndex();
081    }
082    
083    /**
084     * Return parent class, i.e., the class implementing the {@link HasAssignmentContext} interface.
085     * @return parent
086     */
087    public HasAssignmentContext<V,T,C> getParent() {
088        return iParent;
089    }
090}