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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;

/**
 * Attempt to perform an action on a happy business case that will either:
 * 
 *     Succeed and return {@link PotentialFailure#success()}
 *     Fail in a known way as a {@link PotentialFailure#failure(Object) PotentialFailure.failure(sad)}
 *     
Result in a technical failure and throw any kind of {@link Exception}
 * 
 *
 * @param  The type of happy object the action will be performed on
 * @param  The type of sad object that will be returned if the action fails in a known way
 */
@FunctionalInterface
public interface ActionThatMightFail {

    /**
     * @param happy The happy object to attempt an action on
     * @return {@link PotentialFailure#success()} if the action succeeded, else a {@link PotentialFailure#failure(Object) PotentialFailure.failure(sad)}
     * @throws Exception If there was a technical failure when attempting
     */
    PotentialFailure attempt(Happy happy) throws Exception;

    /**
     * @param happy The happy object to attempt an action on
     * @return a {@link HappyPath} that will be happy on the inside if the action was {@link PotentialFailure#success()} or
     * sad on the inside if it was {@link PotentialFailure#failure(Object) PotentialFailure.failure(sad)}
     * @throws Exception If there was a technical failure when attempting
     */
    default HappyPath attemptHappyPath(Happy happy) throws Exception {
        return attempt(happy).toHappyPath(happy);
    }
}