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Tooling for reactive Domain-Driven Design projects that are highly concurrent. Includes compute grid, actor caching, spaces, cross-node cluster messaging, CQRS, and Event Sourcing support.

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// Copyright © 2012-2020 VLINGO LABS. All rights reserved.
//
// This Source Code Form is subject to the terms of the
// Mozilla Public License, v. 2.0. If a copy of the MPL
// was not distributed with this file, You can obtain
// one at https://mozilla.org/MPL/2.0/.

package io.vlingo.lattice.model;

import java.util.function.Function;

import io.vlingo.actors.CompletesEventually;

/**
 * Supports providing a latent {@code Completes} outcome by way of {@code CompletesEventually}.
 * Used by {@code StateObjectQueryActor} to provide answers from queries that complete asynchronously
 * to the original message delivery.
 * @param  the outcome value type of the internal {@code Function}.
 * @param  the return value type of the internal {@code Function}.
 */
public class CompletionTranslator {
  private final CompletesEventually completes;
  private final Function translator;

  /**
   * Answer a new instance of {@code CompletionSupplier} if the {@code supplier} is not {@code null};
   * otherwise answer null.
   * @param translator the {@code Function} of the eventual outcome, or null if none is provided
   * @param completes the CompletesEventually through which the eventual outcome is sent
   * @param  the outcome value type of the internal {@code Function}.
   * @param  the return value type of the internal {@code Function}.
   * @return {@code CompletionBiSupplier}
   */
  public static  CompletionTranslator translatorOrNull(final Function translator, final CompletesEventually completes) {
    if (translator == null) {
      return null;
    }

    return new CompletionTranslator(translator, completes);
  }

  /**
   * Completes the outcome by executing the {@code Function} translator to produce the answer.
   * @param outcome the O outcome to be translated into a completion value
   */
  public void complete(final O outcome) {
    completes.with(translator.apply(outcome));
  }

  /**
   * Construct my default state.
   * @param translator the {@code Function} to translate the eventual outcome with which to complete
   * @param completes the {@code CompletesEventually} used to complete the eventual outcome
   */
  private CompletionTranslator(final Function translator, final CompletesEventually completes) {
    this.translator = translator;
    this.completes = completes;
  }
}