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package java.util.function;

import java.util.Objects;

/**

 * Represents a predicate (boolean-valued function) of one argument.

 *

 * <p>This is a <a href="package-summary.html">functional interface</a>

 * whose functional method is {@link #test(Object)}.

 *

 * @param <T> the type of the input to the predicate

 *

 * @since 1.8

 */

@FunctionalInterface

public interface Predicate<T> {

    /**

     * Evaluates this predicate on the given argument.

     *

     * @param t the input argument

     * @return {@code true} if the input argument matches the predicate,

     * otherwise {@code false}

     */

    boolean test(T t);

    /**

     * Returns a composed predicate that represents a short-circuiting logical

     * AND of this predicate and another.  When evaluating the composed

     * predicate, if this predicate is {@code false}, then the {@code other}

     * predicate is not evaluated.

     *

     * <p>Any exceptions thrown during evaluation of either predicate are relayed

     * to the caller; if evaluation of this predicate throws an exception, the

     * {@code other} predicate will not be evaluated.

     *

     * @param other a predicate that will be logically-ANDed with this

     *              predicate

     * @return a composed predicate that represents the short-circuiting logical

     * AND of this predicate and the {@code other} predicate

     * @throws NullPointerException if other is null

     */

    default Predicate<T> and(Predicate<? super T> other) {

        Objects.requireNonNull(other);

        return (t) -> test(t) && other.test(t);

    }

    /**

     * Returns a predicate that represents the logical negation of this

     * predicate.

     *

     * @return a predicate that represents the logical negation of this

     * predicate

     */

    default Predicate<T> negate() {

        return (t) -> !test(t);

    }

    /**

     * Returns a composed predicate that represents a short-circuiting logical

     * OR of this predicate and another.  When evaluating the composed

     * predicate, if this predicate is {@code true}, then the {@code other}

     * predicate is not evaluated.

     *

     * <p>Any exceptions thrown during evaluation of either predicate are relayed

     * to the caller; if evaluation of this predicate throws an exception, the

     * {@code other} predicate will not be evaluated.

     *

     * @param other a predicate that will be logically-ORed with this

     *              predicate

     * @return a composed predicate that represents the short-circuiting logical

     * OR of this predicate and the {@code other} predicate

     * @throws NullPointerException if other is null

     */

    default Predicate<T> or(Predicate<? super T> other) {

        Objects.requireNonNull(other);

        return (t) -> test(t) || other.test(t);

    }

    /**

     * Returns a predicate that tests if two arguments are equal according

     * to {@link Objects#equals(Object, Object)}.

     *

     * @param <T> the type of arguments to the predicate

     * @param targetRef the object reference with which to compare for equality,

     *               which may be {@code null}

     * @return a predicate that tests if two arguments are equal according

     * to {@link Objects#equals(Object, Object)}

     */

    static <T> Predicate<T> isEqual(Object targetRef) {

        return (null == targetRef)

                ? Objects::isNull

                : object -> targetRef.equals(object);

    }

}