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package org.valkyriercp.rules.constraint;

import org.springframework.util.Assert;

/**
 * "Nots" another unary constraint (the inverse) by using composition.
 *
 * @author Keith Donald
 */
public class Not implements Constraint {
    private Constraint constraint;

    /**
     * Creates a UnaryNot in temporary invalid state - please use only
     * if you have to, the well-formed constructor is much preferred.
     */
    public Not() {

    }

    /**
     * Creates a UnaryNot
     *
     * @param constraint
     *            The constraint to negate.
     */
    public Not(Constraint constraint) {
    	setConstraint(constraint);
    }

    public void setConstraint(Constraint constraint) {
        this.constraint = constraint;
    }

    /**
     * Negates the boolean result returned by testing the wrapped constraint.
     *
     * @see Constraint#test(java.lang.Object)
     */
    public boolean test(Object value) {
    	Assert.state(constraint != null, "The constraint is not set");
        return !constraint.test(value);
    }

    public String toString() {
        return "not(" + getConstraint() + ")";
    }

    public Constraint getConstraint() {
        return constraint;
    }

}