/* Soot - a J*va Optimization Framework
 * Copyright (C) 2007 Manu Sridharan
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the
 * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
 * Boston, MA 02111-1307, USA.
 */
package soot.jimple.spark.ondemand.genericutil;

/**
 * Interface for defining an arbitrary predicate on {@link Object}s.
 */
public abstract class Predicate<T> {
    public static final Predicate FALSE = new Predicate() {

        @Override
        public boolean test(Object obj_) {
            return false;
        }
    };
    
    public static final Predicate TRUE = FALSE.not();
    
    @SuppressWarnings("unchecked")
    public static <T> Predicate<T> truePred() {
        return (Predicate<T>)TRUE;
    }

    @SuppressWarnings("unchecked")
    public static <T> Predicate<T> falsePred() {
        return (Predicate<T>)FALSE;
    }
    
    /** Test whether an {@link Object} satisfies this {@link Predicate} */
    public abstract boolean test(T obj_);

    /** Return a predicate that is a negation of this predicate */
    public Predicate<T> not() {
        final Predicate<T> originalPredicate = this;
        return new Predicate<T>() {
            public boolean test(T obj_) {
                return !originalPredicate.test(obj_);
            }
        };
    }

    /**
     * Return a predicate that is a conjunction of this predicate and another
     * predicate
     */
    public Predicate<T> and(final Predicate<T> conjunct_) {
        final Predicate<T> originalPredicate = this;
        return new Predicate<T>() {
            public boolean test(T obj_) {
                return originalPredicate.test(obj_) && conjunct_.test(obj_);
            }
        };
    }

    /**
     * Return a predicate that is a conjunction of this predicate and another
     * predicate
     */
    public Predicate<T> or(final Predicate<T> disjunct_) {
        final Predicate<T> originalPredicate = this;
        return new Predicate<T>() {
            public boolean test(T obj_) {
                return originalPredicate.test(obj_) || disjunct_.test(obj_);
            }
        };
    }
} // class Predicate