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This library focuses on providing different flavors of eventsourced aggregrates

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/*
 * Copyright 2021-2024 the original author or authors.
 *
 * 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
 *
 *      https://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 dk.cloudcreate.essentials.components.eventsourced.aggregates.decider;

import java.util.Optional;

/**
 * Interface responsible for resolve the optional aggregate id associated with the type T

 * Example of usages:

 * 
 *     Command - return the aggregate id associated with the command (can return an {@link Optional#empty()})
 *     in case server generated id's are used for commands that create a new Aggregate instance)
 *     Event - return the aggregate id associated with the event
 *     State -  return the aggregate id associated with the aggregate state event projection
 *     View -  return the aggregate id associated with the View event projection
 * 
 *
 * @param   The type of object that this resolver support. Could e.g. be a COMMAND, EVENT, Aggregate STATE, VIEW, etc.
 * @param  The type of Aggregate Id
 */
public interface AggregateIdResolver {
    /**
     * Resolve the optional aggregate id associated with the type T

     * Example of usages:

     * 
     *     Command - return the aggregate id associated with the command (can return an {@link Optional#empty()})
     *     in case server generated id's are used for commands that create a new Aggregate instance)
     *     Event - return the aggregate id associated with the event
     *     State -  return the aggregate id associated with the aggregate state event projection
     *     View -  return the aggregate id associated with the View event projection
     * 
     *
     * @param t the instance of T
     * @return if the t contains an aggregate id then it MUST be returned
     * in an {@link Optional#of(Object)} otherwise an {@link Optional#empty()}
     */
    Optional resolveFrom(T t);
}