/*
 * Copyright 2019 The Android Open Source Project
 *
 * 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 androidx.camera.core.impl.utils.futures;

import androidx.annotation.Nullable;
import androidx.annotation.RequiresApi;

import com.google.common.util.concurrent.ListenableFuture;

import java.util.concurrent.ExecutionException;
import java.util.concurrent.Future;

/**
 * Cloned from concurrent-futures package in Guava to AndroidX namespace since we would need
 * ListenableFuture related implementation but not want to include whole Guava library.
 *
 * A callback for accepting the results of a {@link java.util.concurrent.Future} computation
 * asynchronously.
 *
 * <p>To attach to a {@link ListenableFuture} use {@link Futures#addCallback}.
 *
 * @author Anthony Zana
 * @since 10.0
 * @param <V>
 */
@RequiresApi(21) // TODO(b/200306659): Remove and replace with annotation on package-info.java
public interface FutureCallback<V> {
    /** Invoked with the result of the {@code Future} computation when it is successful. */
    void onSuccess(@Nullable V result);

    /**
     * Invoked when a {@code Future} computation fails or is canceled.
     *
     * <p>If the future's {@link Future#get() get} method throws an {@link ExecutionException}, then
     * the cause is passed to this method. Any other thrown object is passed unaltered.
     */
    void onFailure(Throwable t);
}