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package jrummikub.ai.fdsolver.constraint;
import static jrummikub.ai.fdsolver.Satisfiability.*;
import java.util.Arrays;
import java.util.Collection;
import java.util.Collections;
import java.util.Comparator;
import java.util.NoSuchElementException;
import jrummikub.ai.fdsolver.Constraint;
import jrummikub.ai.fdsolver.Propagator;
import jrummikub.ai.fdsolver.Satisfiability;
import jrummikub.ai.fdsolver.Var;
public class ComparatorConstraint<T> extends Constraint {
Var<T> x, y;
Comparator<T> comparator, reverseComparator;
ComparatorPropagator<T> trueX, trueY, falseX, falseY;
boolean allowEqual;
ComparatorConstraint(final Comparator<T> comparator, boolean allowEqual,
Var<T> x, Var<T> y) {
this.x = x;
this.y = y;
this.comparator = comparator;
this.allowEqual = allowEqual;
reverseComparator = new Comparator<T>() {
@Override
public int compare(T o1, T o2) {
return comparator.compare(o2, o1);
}
};
trueX = new ComparatorPropagator<T>(comparator, allowEqual, x, y);
trueY = new ComparatorPropagator<T>(reverseComparator, allowEqual, y, x);
falseX = new ComparatorPropagator<T>(reverseComparator, !allowEqual, x,
y);
falseY = new ComparatorPropagator<T>(comparator, !allowEqual, y, x);
}
@Override
public Collection<Var<?>> getWatchedVars() {
return Arrays.<Var<?>> asList(x, y);
}
@Override
public Collection<Propagator> getPropagators(boolean negate) {
if (negate) {
return Arrays.<Propagator> asList(falseX, falseY);
} else {
return Arrays.<Propagator> asList(trueX, trueY);
}
}
@Override
public Satisfiability getSatisfiability() {
try {
T maxX = Collections.max(x.getRange(), comparator);
T minY = Collections.min(y.getRange(), comparator);
if (comparator.compare(maxX, minY) < (allowEqual ? 1 : 0)) {
return TAUT;
}
T minX = Collections.min(x.getRange(), comparator);
T maxY = Collections.max(y.getRange(), comparator);
if (comparator.compare(maxY, minX) < (allowEqual ? 0 : 1)) {
return UNSAT;
}
return SAT;
} catch (NoSuchElementException e) {
return UNSAT;
}
}
}
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