*     queryFuture.transformAsync((closer, result) -> result.getRowsClosingFuture(), executor);
   *
   * // Result.writeRowsToOutputStreamFuture() returns a ListenableFuture that resolves to the
   * // number of written rows. openOutputFile() returns a FileOutputStream (which implements
   * // Closeable).
   * ClosingFuture<Integer> rowsFuture2 =
   *     queryFuture.transformAsync(
   *         (closer, result) -> {

package com.google.common.util.concurrent;

import static com.google.common.truth.Truth.assertThat;
import static com.google.common.util.concurrent.Futures.immediateFuture;
import static com.google.common.util.concurrent.Futures.transformAsync;
import static com.google.common.util.concurrent.MoreExecutors.directExecutor;
import static com.google.common.util.concurrent.Uninterruptibles.awaitUninterruptibly;
import static org.junit.Assert.assertThrows;

package com.google.common.util.concurrent;

import static com.google.common.truth.Truth.assertThat;
import static com.google.common.util.concurrent.Futures.immediateFuture;
import static com.google.common.util.concurrent.Futures.transformAsync;
import static com.google.common.util.concurrent.MoreExecutors.directExecutor;
import static com.google.common.util.concurrent.Uninterruptibles.awaitUninterruptibly;
import static org.junit.Assert.assertThrows;

import java.util.concurrent.Future;
import org.jspecify.annotations.Nullable;

/**
 * Transforms a value, possibly asynchronously. For an example usage and more information, see
 * {@link Futures#transformAsync(ListenableFuture, AsyncFunction, Executor)}.
 *
 * @author Chris Povirk
 * @since 11.0
 */
@GwtCompatible
public interface AsyncFunction<I extends @Nullable Object, O extends @Nullable Object> {
  /**

   *     queryFuture.transformAsync((closer, result) -> result.getRowsClosingFuture(), executor);
   *
   * // Result.writeRowsToOutputStreamFuture() returns a ListenableFuture that resolves to the
   * // number of written rows. openOutputFile() returns a FileOutputStream (which implements
   * // Closeable).
   * ClosingFuture<Integer> rowsFuture2 =
   *     queryFuture.transformAsync(
   *         (closer, result) -> {

    assertClosed(closeable1, closeable2);
  }

  public void testTransformAsync() throws Exception {
    ClosingFuture<String> closingFuture =
        ClosingFuture.from(immediateFuture("value"))
            .transformAsync(
                new AsyncClosingFunction<String, TestCloseable>() {
                  @Override
                  public ClosingFuture<TestCloseable> apply(DeferredCloser closer, String v)

   *     input's failure (if not)
   */
  public final <T extends @Nullable Object> FluentFuture<T> transformAsync(
      AsyncFunction<? super V, T> function, Executor executor) {
    return (FluentFuture<T>) Futures.transformAsync(this, function, executor);
  }

  /**
   * Returns a new {@code Future} whose result is derived from the result of this {@code Future}. If

    assertThat(f.get()).isEqualTo(2);
  }

  public void testTransformAsync() throws Exception {
    FluentFuture<Integer> f =
        FluentFuture.from(immediateFuture(1))
            .transformAsync(
                new AsyncFunction<Integer, Integer>() {
                  @Override
                  public ListenableFuture<Integer> apply(Integer input) {
                    return immediateFuture(input + 1);

   * Example usage:
   *
   * {@snippet :
   * ListenableFuture<RowKey> rowKeyFuture = indexService.lookUp(query);
   * ListenableFuture<QueryResult> queryFuture =
   *     transformAsync(rowKeyFuture, dataService::readFuture, executor);
   * }
   *
   * <p>When selecting an executor, note that {@code directExecutor} is dangerous in some cases. See