/*

 * Licensed to the Apache Software Foundation (ASF) under one or more

 * contributor license agreements.  See the NOTICE file distributed with

 * this work for additional information regarding copyright ownership.

 * The ASF licenses this file to You under the Apache License, Version 2.0

 * (the "License"); you may not use this file except in compliance with

 * the License.  You may obtain a copy of the License at

 *

 *      http://www.apache.org/licenses/LICENSE-2.0

 *

 * Unless required by applicable law or agreed to in writing, software

 * distributed under the License is distributed on an "AS IS" BASIS,

 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

 * See the License for the specific language governing permissions and

 * limitations under the License.

 */

package org.apache.commons.lang3.function;

import java.util.Objects;

import java.util.function.Function;

/**

 * A functional interface like {@link Function} that declares a {@code Throwable}.

 *

 * @param <T> Input type 1.

 * @param <R> Return type.

 * @param <E> Thrown exception.

 * @since 3.11

 */

@FunctionalInterface

public interface FailableFunction<T, R, E extends Throwable> {

    /** NOP singleton */

    @SuppressWarnings("rawtypes")

    FailableFunction NOP = t -> null;

    /**

     * Returns a function that always returns its input argument.

     *

     * @param <T> the type of the input and output objects to the function

     * @param <E> Thrown exception.

     * @return a function that always returns its input argument

     */

    static <T, E extends Throwable> FailableFunction<T, T, E> identity() {

        return t -> t;

    }

    /**

     * Returns The NOP singleton.

     *

     * @param <T> Consumed type 1.

     * @param <R> Return type.

     * @param <E> Thrown exception.

     * @return The NOP singleton.

     */

    static <T, R, E extends Throwable> FailableFunction<T, R, E> nop() {

        return NOP;

    }

    /**

     * Returns a composed {@code FailableFunction} like {@link Function#andThen(Function)}.

     *

     * @param <V> the output type of the {@code after} function, and of the composed function.

     * @return a composed {@code FailableFunction} like {@link Function#andThen(Function)}.

     * @param after the operation to perform after this one.

     * @throws NullPointerException when {@code after} is null.

     */

    default <V> FailableFunction<T, V, E> andThen(final FailableFunction<? super R, ? extends V, E> after) {

        Objects.requireNonNull(after);

        return (final T t) -> after.apply(apply(t));

    }

    /**

     * Applies this function.

     *

     * @param input the input for the function

     * @return the result of the function

     * @throws E Thrown when the function fails.

     */

    R apply(T input) throws E;

    /**

     * Returns a composed {@code FailableFunction} like {@link Function#compose(Function)}.

     *

     * @param <V> the input type to the {@code before} function, and to the composed function.

     * @param before the operator to apply before this one.

     * @return a a composed {@code FailableFunction} like {@link Function#compose(Function)}.

     * @throws NullPointerException if before is null.

     * @see #andThen(FailableFunction)

     */

    default <V> FailableFunction<V, R, E> compose(final FailableFunction<? super V, ? extends T, E> before) {

        Objects.requireNonNull(before);

        return (final V v) -> apply(before.apply(v));

    }

}