ParseTaskUtils.java

/*
 * Copyright (c) 2015-present, Parse, LLC.
 * All rights reserved.
 *
 * This source code is licensed under the BSD-style license found in the
 * LICENSE file in the root directory of this source tree. An additional grant
 * of patent rights can be found in the PATENTS file in the same directory.
 */
package com.parse;

import java.util.concurrent.CancellationException;

import bolts.AggregateException;
import bolts.Continuation;
import bolts.Task;
import bolts.TaskCompletionSource;

/** package */ class ParseTaskUtils {

  /**
   * Converts a task execution into a synchronous action.
   */
  //TODO (grantland): Task.cs actually throws an AggregateException if the task was cancelled with
  // TaskCancellationException as an inner exception or an AggregateException with the original
  // exception as an inner exception if task.isFaulted().
  // https://msdn.microsoft.com/en-us/library/dd235635(v=vs.110).aspx
  /* package */ static <T> T wait(Task<T> task) throws ParseException {
    try {
      task.waitForCompletion();
      if (task.isFaulted()) {
        Exception error = task.getError();
        if (error instanceof ParseException) {
          throw (ParseException) error;
        }
        if (error instanceof AggregateException) {
          throw new ParseException(error);
        }
        if (error instanceof RuntimeException) {
          throw (RuntimeException) error;
        }
        throw new RuntimeException(error);
      } else if (task.isCancelled()) {
        throw new RuntimeException(new CancellationException());
      }
      return task.getResult();
    } catch (InterruptedException e) {
      throw new RuntimeException(e);
    }
  }

  //region Task to Callbacks

  /**
   * Calls the callback after a task completes on the main thread, returning a Task that completes
   * with the same result as the input task after the callback has been run.
   */
  /* package */ static Task<Void> callbackOnMainThreadAsync(Task<Void> task,
      final ParseCallback1<ParseException> callback) {
    return callbackOnMainThreadAsync(task, callback, false);
  }

  /**
   * Calls the callback after a task completes on the main thread, returning a Task that completes
   * with the same result as the input task after the callback has been run. If reportCancellation
   * is false, the callback will not be called if the task was cancelled.
   */
  /* package */ static Task<Void> callbackOnMainThreadAsync(Task<Void> task,
      final ParseCallback1<ParseException> callback, final boolean reportCancellation) {
    if (callback == null) {
      return task;
    }
    return callbackOnMainThreadAsync(task, new ParseCallback2<Void, ParseException>() {
      @Override
      public void done(Void aVoid, ParseException e) {
        callback.done(e);
      }
    }, reportCancellation);
  }


  /**
   * Calls the callback after a task completes on the main thread, returning a Task that completes
   * with the same result as the input task after the callback has been run.
   */
  /* package */ static <T> Task<T> callbackOnMainThreadAsync(Task<T> task,
      final ParseCallback2<T, ParseException> callback) {
    return callbackOnMainThreadAsync(task, callback, false);
  }

  /**
   * Calls the callback after a task completes on the main thread, returning a Task that completes
   * with the same result as the input task after the callback has been run. If reportCancellation
   * is false, the callback will not be called if the task was cancelled.
   */
  /* package */ static <T> Task<T> callbackOnMainThreadAsync(Task<T> task,
      final ParseCallback2<T, ParseException> callback, final boolean reportCancellation) {
    if (callback == null) {
      return task;
    }
    final TaskCompletionSource<T> tcs = new TaskCompletionSource();
    task.continueWith(new Continuation<T, Void>() {
      @Override
      public Void then(final Task<T> task) throws Exception {
        if (task.isCancelled() && !reportCancellation) {
          tcs.setCancelled();
          return null;
        }
        ParseExecutors.main().execute(new Runnable() {
          @Override
          public void run() {
            try {
              Exception error = task.getError();
              if (error != null && !(error instanceof ParseException)) {
                error = new ParseException(error);
              }
              callback.done(task.getResult(), (ParseException) error);
            } finally {
              if (task.isCancelled()) {
                tcs.setCancelled();
              } else if (task.isFaulted()) {
                tcs.setError(task.getError());
              } else {
                tcs.setResult(task.getResult());
              }
            }
          }
        });
        return null;
      }
    });
    return tcs.getTask();
  }

  //endregion
}