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/*
 * This file is part of ***  M y C o R e  ***
 * See http://www.mycore.de/ for details.
 *
 * MyCoRe is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * MyCoRe 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 General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with MyCoRe.  If not, see .
 */

package org.mycore.common.function;

import java.util.Objects;
import java.util.function.BiFunction;
import java.util.function.Function;

/**
 * Represents a function that accepts one argument and produces a result and throws an Exception.
 *
 * Use {@link #toFunction()} or {@link #toFunction(BiFunction, Class)} to transform this
 * MCRThrowFunction into a Function that can be handled throughout Java 8.
 *
 * @param  the type of the input to the function
 * @param  the type of the result of the function
 * @param  the exception that is throw by this function-
 *
 * @since 2015.12
 */
@FunctionalInterface
public interface MCRThrowFunction {
    /**
     * Applies this function to the given argument.
     *
     * @param t the function argument
     * @return the function result
     */
    R apply(T t) throws E;

    /**
     * Returns a composed function that first applies the {@code before}
     * function to its input, and then applies this function to the result.
     * If evaluation of either function throws an exception, it is relayed to
     * the caller of the composed function.
     *
     * @param  the type of input to the {@code before} function, and to the
     *           composed function
     * @param before the function to apply before this function is applied
     * @return a composed function that first applies the {@code before}
     * function and then applies this function
     * @throws NullPointerException if before is null
     *
     * @see #andThen(MCRThrowFunction)
     */
    default  MCRThrowFunction compose(MCRThrowFunction before) {
        Objects.requireNonNull(before);
        return (V v) -> apply(before.apply(v));
    }

    /**
     * Returns a composed function that first applies this function to
     * its input, and then applies the {@code after} function to the result.
     * If evaluation of either function throws an exception, it is relayed to
     * the caller of the composed function.
     *
     * @param  the type of output of the {@code after} function, and of the
     *           composed function
     * @param after the function to apply after this function is applied
     * @return a composed function that first applies this function and then
     * applies the {@code after} function
     * @throws NullPointerException if after is null
     *
     * @see #compose(MCRThrowFunction)
     */
    default  MCRThrowFunction andThen(MCRThrowFunction after) {
        Objects.requireNonNull(after);
        return (T t) -> after.apply(apply(t));
    }

    /**
     * Returns a function that catches <E> and forwards it to the throwableHandler together with the Exception.
     * 
     * Use this method if you want to react on the certain Exceptions and return a result
     * or rethrow a specific RuntimeExption.
     * @param throwableHandler a BiFunction that handles original Input and caught Exception
     * @param exClass class of exception to catch
     */
    default Function toFunction(BiFunction throwableHandler, Class exClass) {
        return t -> {
            try {
                return this.apply(t);
            } catch (Throwable e) {
                if (exClass.isAssignableFrom(e.getClass())) {
                    @SuppressWarnings("unchecked")
                    E handableException = (E) e;
                    return throwableHandler.apply(t, handableException);
                }
                throw (RuntimeException) e;
            }
        };
    }

    /**
     * Returns a Function that applies <T> and catches any exception and wraps it into a {@link RuntimeException} if needed.
     * Use this if you just want no specific exception handling.
     */
    default Function toFunction() {
        return toFunction((t, e) -> {
            if (e instanceof RuntimeException) {
                throw (RuntimeException) e;
            }
            throw new RuntimeException(e);
        }, Throwable.class);
    }
}