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A combination of the Try monad and the Either monad, to help tame complex business flows.

There is a newer version: 10.3.0

/*
 * Copyright 2016 Liam Williams .
 *
 * This file is part of business-flows.
 *
 * Licensed 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 io.github.theangrydev.businessflows;

import java.util.Optional;
import java.util.function.Function;

/**
 * A {@link BusinessCase} is either a {@link HappyCase}, a {@link SadCase} or a {@link TechnicalFailure}.
 *
 * @param  The type of happy object this case may represent
 * @param  The type of sad object this case may represent
 */
interface BusinessCase {

    /**
     * Join to a common result type. No matter what the {@link BusinessCase} actually is, the result type is the same.
     *
     * @param happyJoiner What to do if this is a {@link HappyCase}
     * @param sadJoiner What to do if this is a {@link SadCase}
     * @param technicalFailureJoiner What to do if this is a {@link TechnicalFailureCase}
     * @param  The type of the result
     * @return The result after applying the joiner that corresponds to the underlying business case
     */
     Result join(Mapping happyJoiner, Mapping sadJoiner, Function technicalFailureJoiner);

    /**
     * Same as {@link #join(Mapping, Mapping, Function)} but if the {@link BusinessCase} is a
     * {@link TechnicalFailureCase}, then the underlying exception will be thrown instead of joined.
     *
     * @param happyJoiner What to do if this is a {@link HappyCase}
     * @param sadJoiner What to do if this is a {@link SadCase}
     * @param  The type of the result
     * @return The result after applying the joiner that corresponds to the underlying business case
     * @throws Exception If this is a {@link TechnicalFailureCase}.
     */
     Result join(Mapping happyJoiner, Mapping sadJoiner) throws Exception;

    /**
     * @return {@link Optional#of(Object) Optional.of(Happy)} if this is a {@link HappyCase}, otherwise {@link Optional#empty()}
     */
    Optional happyOptional();

    /**
     * @return {@link Optional#of(Object) Optional.of(Sad)} if this is a {@link SadCase}, otherwise {@link Optional#empty()}
     */
    Optional sadOptional();

    /**
     * @return {@link Optional#of(Object) Optional.of(Exception)} if this is a {@link TechnicalFailureCase}, otherwise {@link Optional#empty()}
     */
    Optional technicalFailureOptional();
}