src/jrummikub/ai/fdsolver/constraint/FilterConstraint.java


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package jrummikub.ai.fdsolver.constraint;

import static jrummikub.ai.fdsolver.Satisfiability.SAT;
import static jrummikub.ai.fdsolver.Satisfiability.TAUT;
import static jrummikub.ai.fdsolver.Satisfiability.UNSAT;

import java.util.Arrays;
import java.util.Collection;

import jrummikub.ai.fdsolver.Constraint;
import jrummikub.ai.fdsolver.Propagator;
import jrummikub.ai.fdsolver.Satisfiability;
import jrummikub.ai.fdsolver.Var;

public class FilterConstraint<T> implements Constraint {
	private Var<T> var;
	private Propagator trueProp, falseProp;
	private Filter<T> filter;

	public FilterConstraint(final Filter<T> filter, Var<T> var) {
		this.var = var;
		this.filter = filter;
		trueProp = new FilterPropagator<T>(filter, var);
		falseProp = new FilterPropagator<T>(new Filter<T>() {
			@Override
			public boolean accept(T value) {
				return !filter.accept(value);
			}
		}, var);
	}

	@Override
	public Collection<Var<?>> getWatchedVars() {
		return Arrays.<Var<?>> asList(var);
	}

	@Override
	public Collection<Propagator> getPropagators(boolean negate) {
		return Arrays.asList(negate ? falseProp : trueProp);
	}

	@Override
	public Satisfiability getSatisfiability() {
		boolean any = false;
		boolean all = true;
		
		for (T value : var.getRange()) {
			boolean accepted = filter.accept(value);
			if (accepted) {
				any = true;
			} else {
				all = false;
			}
		}
		
		if (all && any) {
			return TAUT;
		} else if (any) {
			return SAT;
		} else {
			return UNSAT;
		}
	}

}