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Bolts is a collection of low-level libraries designed to make developing mobile apps easier.

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/*
 *  Copyright (c) 2014, Facebook, Inc.
 *  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 bolts;

import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.List;
import java.util.concurrent.Callable;
import java.util.concurrent.CancellationException;
import java.util.concurrent.Executor;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.ScheduledExecutorService;
import java.util.concurrent.ScheduledFuture;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicBoolean;
import java.util.concurrent.atomic.AtomicInteger;

/**
 * Represents the result of an asynchronous operation.
 * 
 * @param 
 *          The type of the result of the task.
 */
public class Task {
  /**
   * An {@link java.util.concurrent.Executor} that executes tasks in parallel.
   */
  public static final ExecutorService BACKGROUND_EXECUTOR = BoltsExecutors.background();

  /**
   * An {@link java.util.concurrent.Executor} that executes tasks in the current thread unless
   * the stack runs too deep, at which point it will delegate to {@link Task#BACKGROUND_EXECUTOR} in
   * order to trim the stack.
   */
  private static final Executor IMMEDIATE_EXECUTOR = BoltsExecutors.immediate();

  /**
   * An {@link java.util.concurrent.Executor} that executes tasks on the UI thread.
   */
  public static final Executor UI_THREAD_EXECUTOR = AndroidExecutors.uiThread();

  private final Object lock = new Object();
  private boolean complete;
  private boolean cancelled;
  private TResult result;
  private Exception error;
  private List> continuations = new ArrayList<>();

  /* package */ Task() {
  }

  private Task(TResult result) {
    trySetResult(result);
  }

  private Task(boolean cancelled) {
    if (cancelled) {
      trySetCancelled();
    } else {
      trySetResult(null);
    }
  }

  /**
   * @deprecated Please use {@link bolts.TaskCompletionSource()} instead.
   */
  public static  Task.TaskCompletionSource create() {
    Task task = new Task<>();
    return task.new TaskCompletionSource();
  }

  /**
   * @return {@code true} if the task completed (has a result, an error, or was cancelled.
   *         {@code false} otherwise.
   */
  public boolean isCompleted() {
    synchronized (lock) {
      return complete;
    }
  }

  /**
   * @return {@code true} if the task was cancelled, {@code false} otherwise.
   */
  public boolean isCancelled() {
    synchronized (lock) {
      return cancelled;
    }
  }

  /**
   * @return {@code true} if the task has an error, {@code false} otherwise.
   */
  public boolean isFaulted() {
    synchronized (lock) {
      return error != null;
    }
  }

  /**
   * @return The result of the task, if set. {@code null} otherwise.
   */
  public TResult getResult() {
    synchronized (lock) {
      return result;
    }
  }

  /**
   * @return The error for the task, if set. {@code null} otherwise.
   */
  public Exception getError() {
    synchronized (lock) {
      return error;
    }
  }

  /**
   * Blocks until the task is complete.
   */
  public void waitForCompletion() throws InterruptedException {
    synchronized (lock) {
      if (!isCompleted()) {
        lock.wait();
      }
    }
  }

  /**
   * Creates a completed task with the given value.
   */
  @SuppressWarnings("unchecked")
  public static  Task forResult(TResult value) {
    if (value == null) {
      return (Task) TASK_NULL;
    }
    if (value instanceof Boolean) {
      return (Task) ((Boolean) value ? TASK_TRUE : TASK_FALSE);
    }
    bolts.TaskCompletionSource tcs = new bolts.TaskCompletionSource<>();
    tcs.setResult(value);
    return tcs.getTask();
  }

  /**
   * Creates a faulted task with the given error.
   */
  public static  Task forError(Exception error) {
    bolts.TaskCompletionSource tcs = new bolts.TaskCompletionSource<>();
    tcs.setError(error);
    return tcs.getTask();
  }

  /**
   * Creates a cancelled task.
   */
  @SuppressWarnings("unchecked")
  public static  Task cancelled() {
    return (Task) TASK_CANCELLED;
  }

  /**
   * Creates a task that completes after a time delay.
   *
   * @param delay The number of milliseconds to wait before completing the returned task. Zero and
   *              negative values are treated as requests for immediate execution.
   */
  public static Task delay(long delay) {
    return delay(delay, BoltsExecutors.scheduled(), null);
  }

  /**
   * Creates a task that completes after a time delay.
   *
   * @param delay The number of milliseconds to wait before completing the returned task. Zero and
   *              negative values are treated as requests for immediate execution.
   * @param cancellationToken The optional cancellation token that will be checked prior to
   *                          completing the returned task.
   */
  public static Task delay(long delay, CancellationToken cancellationToken) {
    return delay(delay, BoltsExecutors.scheduled(), cancellationToken);
  }

  /* package */ static Task delay(long delay, ScheduledExecutorService executor, final CancellationToken cancellationToken) {
    if (cancellationToken != null && cancellationToken.isCancellationRequested()) {
      return Task.cancelled();
    }

    if (delay <= 0) {
      return Task.forResult(null);
    }

    final bolts.TaskCompletionSource tcs = new bolts.TaskCompletionSource<>();
    final ScheduledFuture scheduled = executor.schedule(new Runnable() {
      @Override
      public void run() {
        tcs.trySetResult(null);
      }
    }, delay, TimeUnit.MILLISECONDS);

    if (cancellationToken != null) {
      cancellationToken.register(new Runnable() {
        @Override
        public void run() {
          scheduled.cancel(true);
          tcs.trySetCancelled();
        }
      });
    }

    return tcs.getTask();
  }

  /**
   * Makes a fluent cast of a Task's result possible, avoiding an extra continuation just to cast
   * the type of the result.
   */
  public  Task cast() {
    @SuppressWarnings("unchecked")
    Task task = (Task) this;
    return task;
  }

  /**
   * Turns a Task into a Task, dropping any result.
   */
  public Task makeVoid() {
    return this.continueWithTask(new Continuation>() {
      @Override
      public Task then(Task task) throws Exception {
        if (task.isCancelled()) {
          return Task.cancelled();
        }
        if (task.isFaulted()) {
          return Task.forError(task.getError());
        }
        return Task.forResult(null);
      }
    });
  }

  /**
   * Invokes the callable on a background thread, returning a Task to represent the operation.
   *
   * If you want to cancel the resulting Task throw a {@link java.util.concurrent.CancellationException}
   * from the callable.
   */
  public static  Task callInBackground(Callable callable) {
    return call(callable, BACKGROUND_EXECUTOR, null);
  }

  /**
   * Invokes the callable on a background thread, returning a Task to represent the operation.
   */
  public static  Task callInBackground(Callable callable, CancellationToken ct) {
    return call(callable, BACKGROUND_EXECUTOR, ct);
  }

  /**
   * Invokes the callable using the given executor, returning a Task to represent the operation.
   *
   * If you want to cancel the resulting Task throw a {@link java.util.concurrent.CancellationException}
   * from the callable.
   */
  public static  Task call(final Callable callable, Executor executor) {
    return call(callable, executor, null);
  }

  /**
   * Invokes the callable using the given executor, returning a Task to represent the operation.
   */
  public static  Task call(final Callable callable, Executor executor,
      final CancellationToken ct) {
    final bolts.TaskCompletionSource tcs = new bolts.TaskCompletionSource<>();
    executor.execute(new Runnable() {
      @Override
      public void run() {
        if (ct != null && ct.isCancellationRequested()) {
          tcs.setCancelled();
          return;
        }

        try {
          tcs.setResult(callable.call());
        } catch (CancellationException e) {
          tcs.setCancelled();
        } catch (Exception e) {
          tcs.setError(e);
        }
      }
    });
    return tcs.getTask();
  }

  /**
   * Invokes the callable on the current thread, producing a Task.
   *
   * If you want to cancel the resulting Task throw a {@link java.util.concurrent.CancellationException}
   * from the callable.
   */
  public static  Task call(final Callable callable) {
    return call(callable, IMMEDIATE_EXECUTOR, null);
  }

  /**
   * Invokes the callable on the current thread, producing a Task.
   */
  public static  Task call(final Callable callable, CancellationToken ct) {
    return call(callable, IMMEDIATE_EXECUTOR, ct);
  }

  /**
   * Creates a task that will complete when any of the supplied tasks have completed.
   * 

   * The returned task will complete when any of the supplied tasks has completed. The returned task
   * will always end in the completed state with its result set to the first task to complete. This
   * is true even if the first task to complete ended in the canceled or faulted state.
   *
   * @param tasks
   *          The tasks to wait on for completion.
   * @return A task that represents the completion of one of the supplied tasks. 
   *         The return task's result is the task that completed.
   */
  public static  Task> whenAnyResult(Collection> tasks) {
    if (tasks.size() == 0) {
      return Task.forResult(null);
    }

    final bolts.TaskCompletionSource> firstCompleted = new bolts.TaskCompletionSource<>();
    final AtomicBoolean isAnyTaskComplete = new AtomicBoolean(false);

    for (Task task : tasks) {
      task.continueWith(new Continuation() {
        @Override
        public Void then(Task task) {
          if (isAnyTaskComplete.compareAndSet(false, true)) {
            firstCompleted.setResult(task);
          }
          return null;
        }
      });
    }
    return firstCompleted.getTask();
  }

   /**
   * Creates a task that will complete when any of the supplied tasks have completed.
   * 

   * The returned task will complete when any of the supplied tasks has completed. The returned task
   * will always end in the completed state with its result set to the first task to complete. This
   * is true even if the first task to complete ended in the canceled or faulted state.
   *
   * @param tasks
   *          The tasks to wait on for completion.
   * @return A task that represents the completion of one of the supplied tasks. 
   *         The return task's Result is the task that completed.
   */
  @SuppressWarnings("unchecked")
  public static Task> whenAny(Collection> tasks) {
    if (tasks.size() == 0) {
      return Task.forResult(null);
    }
      
    final bolts.TaskCompletionSource> firstCompleted = new bolts.TaskCompletionSource<>();
    final AtomicBoolean isAnyTaskComplete = new AtomicBoolean(false);
      
    for (Task task : tasks) {
      ((Task) task).continueWith(new Continuation() {
        @Override
        public Void then(Task task) {
          if (isAnyTaskComplete.compareAndSet(false, true)) {
            firstCompleted.setResult(task);
          }
          return null;
        }
      });
    }
    return firstCompleted.getTask();
  }

  /**
   * Creates a task that completes when all of the provided tasks are complete.
   * 

   * If any of the supplied tasks completes in a faulted state, the returned task will also complete
   * in a faulted state, where its exception will resolve to that {@link java.lang.Exception} if a
   * single task fails or an {@link AggregateException} of all the {@link java.lang.Exception}s
   * if multiple tasks fail.
   * 

   * If none of the supplied tasks faulted but at least one of them was cancelled, the returned
   * task will end as cancelled.
   * 

   * If none of the tasks faulted and none of the tasks were cancelled, the resulting task will end
   * completed. The result of the returned task will be set to a list containing all of the results
   * of the supplied tasks in the same order as they were provided (e.g. if the input tasks collection
   * contained t1, t2, t3, the output task's result will return an {@code List<TResult>}
   * where {@code list.get(0) == t1.getResult(), list.get(1) == t2.getResult(), and
   * list.get(2) == t3.getResult()}).
   * 

   * If the supplied collection contains no tasks, the returned task will immediately transition to
   * a completed state before it's returned to the caller.
   * The returned {@code List<TResult>} will contain 0 elements.
   *
   * @param tasks The tasks that the return value will wait for before completing.
   * @return A Task that will resolve to {@code List<TResult>} when all the tasks are resolved.
   */
  public static  Task> whenAllResult(final Collection> tasks) {
    return whenAll(tasks).onSuccess(new Continuation>() {
      @Override
      public List then(Task task) throws Exception {
        if (tasks.size() == 0) {
          return Collections.emptyList();
        }

        List results = new ArrayList<>();
        for (Task individualTask : tasks) {
          results.add(individualTask.getResult());
        }
        return results;
      }
    });
  }

  /**
   * Creates a task that completes when all of the provided tasks are complete.
   * 

   * If any of the supplied tasks completes in a faulted state, the returned task will also complete
   * in a faulted state, where its exception will resolve to that {@link java.lang.Exception} if a
   * single task fails or an {@link AggregateException} of all the {@link java.lang.Exception}s
   * if multiple tasks fail.
   * 

   * If none of the supplied tasks faulted but at least one of them was cancelled, the returned
   * task will end as cancelled.
   * 

   * If none of the tasks faulted and none of the tasks were canceled, the resulting task will
   * end in the completed state.
   * 

   * If the supplied collection contains no tasks, the returned task will immediately transition
   * to a completed state before it's returned to the caller.
   *
   * @param tasks The tasks that the return value will wait for before completing.
   * @return A Task that will resolve to {@code Void} when all the tasks are resolved.
   */
  public static Task whenAll(Collection> tasks) {
    if (tasks.size() == 0) {
      return Task.forResult(null);
    }

    final bolts.TaskCompletionSource allFinished = new bolts.TaskCompletionSource<>();
    final ArrayList causes = new ArrayList<>();
    final Object errorLock = new Object();
    final AtomicInteger count = new AtomicInteger(tasks.size());
    final AtomicBoolean isCancelled = new AtomicBoolean(false);

    for (Task task : tasks) {
      @SuppressWarnings("unchecked")
      Task t = (Task) task;
      t.continueWith(new Continuation() {
        @Override
        public Void then(Task task) {
          if (task.isFaulted()) {
            synchronized (errorLock) {
              causes.add(task.getError());
            }
          }

          if (task.isCancelled()) {
            isCancelled.set(true);
          }

          if (count.decrementAndGet() == 0) {
            if (causes.size() != 0) {
              if (causes.size() == 1) {
                allFinished.setError(causes.get(0));
              } else {
                Exception error = new AggregateException(
                    String.format("There were %d exceptions.", causes.size()),
                    causes);
                allFinished.setError(error);
              }
            } else if (isCancelled.get()) {
              allFinished.setCancelled();
            } else {
              allFinished.setResult(null);
            }
          }
          return null;
        }
      });
    }

    return allFinished.getTask();
  }

  /**
   * Continues a task with the equivalent of a Task-based while loop, where the body of the loop is
   * a task continuation.
   */
  public Task continueWhile(Callable predicate,
      Continuation> continuation) {
    return continueWhile(predicate, continuation, IMMEDIATE_EXECUTOR, null);
  }

  /**
   * Continues a task with the equivalent of a Task-based while loop, where the body of the loop is
   * a task continuation.
   */
  public Task continueWhile(Callable predicate,
      Continuation> continuation, CancellationToken ct) {
    return continueWhile(predicate, continuation, IMMEDIATE_EXECUTOR, ct);
  }

  /**
   * Continues a task with the equivalent of a Task-based while loop, where the body of the loop is
   * a task continuation.
   */
  public Task continueWhile(final Callable predicate,
      final Continuation> continuation, final Executor executor) {
    return continueWhile(predicate, continuation, executor, null);
  }

  /**
   * Continues a task with the equivalent of a Task-based while loop, where the body of the loop is
   * a task continuation.
   */
  public Task continueWhile(final Callable predicate,
      final Continuation> continuation, final Executor executor,
      final CancellationToken ct) {
    final Capture>> predicateContinuation =
        new Capture<>();
    predicateContinuation.set(new Continuation>() {
      @Override
      public Task then(Task task) throws Exception {
        if (ct != null && ct.isCancellationRequested()) {
          return Task.cancelled();
        }

        if (predicate.call()) {
          return Task. forResult(null).onSuccessTask(continuation, executor)
              .onSuccessTask(predicateContinuation.get(), executor);
        }
        return Task.forResult(null);
      }
    });
    return makeVoid().continueWithTask(predicateContinuation.get(), executor);
  }

  /**
   * Adds a continuation that will be scheduled using the executor, returning a new task that
   * completes after the continuation has finished running. This allows the continuation to be
   * scheduled on different thread.
   */
  public  Task continueWith(
      final Continuation continuation, final Executor executor) {
    return continueWith(continuation, executor, null);
  }

  /**
   * Adds a continuation that will be scheduled using the executor, returning a new task that
   * completes after the continuation has finished running. This allows the continuation to be
   * scheduled on different thread.
   */
  public  Task continueWith(
      final Continuation continuation, final Executor executor,
      final CancellationToken ct) {
    boolean completed;
    final bolts.TaskCompletionSource tcs = new bolts.TaskCompletionSource<>();
    synchronized (lock) {
      completed = this.isCompleted();
      if (!completed) {
        this.continuations.add(new Continuation() {
          @Override
          public Void then(Task task) {
            completeImmediately(tcs, continuation, task, executor, ct);
            return null;
          }
        });
      }
    }
    if (completed) {
      completeImmediately(tcs, continuation, this, executor, ct);
    }
    return tcs.getTask();
  }

  /**
   * Adds a synchronous continuation to this task, returning a new task that completes after the
   * continuation has finished running.
   */
  public  Task continueWith(
      Continuation continuation) {
    return continueWith(continuation, IMMEDIATE_EXECUTOR, null);
  }

  /**
   * Adds a synchronous continuation to this task, returning a new task that completes after the
   * continuation has finished running.
   */
  public  Task continueWith(
      Continuation continuation, CancellationToken ct) {
    return continueWith(continuation, IMMEDIATE_EXECUTOR, ct);
  }

  /**
   * Adds an Task-based continuation to this task that will be scheduled using the executor,
   * returning a new task that completes after the task returned by the continuation has completed.
   */
  public  Task continueWithTask(
      final Continuation> continuation, final Executor executor) {
    return continueWithTask(continuation, executor, null);
  }

  /**
   * Adds an Task-based continuation to this task that will be scheduled using the executor,
   * returning a new task that completes after the task returned by the continuation has completed.
   */
  public  Task continueWithTask(
      final Continuation> continuation, final Executor executor,
      final CancellationToken ct) {
    boolean completed;
    final bolts.TaskCompletionSource tcs = new bolts.TaskCompletionSource<>();
    synchronized (lock) {
      completed = this.isCompleted();
      if (!completed) {
        this.continuations.add(new Continuation() {
          @Override
          public Void then(Task task) {
            completeAfterTask(tcs, continuation, task, executor, ct);
            return null;
          }
        });
      }
    }
    if (completed) {
      completeAfterTask(tcs, continuation, this, executor, ct);
    }
    return tcs.getTask();
  }

  /**
   * Adds an asynchronous continuation to this task, returning a new task that completes after the
   * task returned by the continuation has completed.
   */
  public  Task continueWithTask(
      Continuation> continuation) {
    return continueWithTask(continuation, IMMEDIATE_EXECUTOR, null);
  }

  /**
   * Adds an asynchronous continuation to this task, returning a new task that completes after the
   * task returned by the continuation has completed.
   */
  public  Task continueWithTask(
      Continuation> continuation, CancellationToken ct) {
    return continueWithTask(continuation, IMMEDIATE_EXECUTOR, ct);
  }

  /**
   * Runs a continuation when a task completes successfully, forwarding along
   * {@link java.lang.Exception} or cancellation.
   */
  public  Task onSuccess(
      final Continuation continuation, Executor executor) {
    return onSuccess(continuation, executor, null);
  }

  /**
   * Runs a continuation when a task completes successfully, forwarding along
   * {@link java.lang.Exception} or cancellation.
   */
  public  Task onSuccess(
      final Continuation continuation, Executor executor,
      final CancellationToken ct) {
    return continueWithTask(new Continuation>() {
      @Override
      public Task then(Task task) {
        if (ct != null && ct.isCancellationRequested()) {
          return Task.cancelled();
        }

        if (task.isFaulted()) {
          return Task.forError(task.getError());
        } else if (task.isCancelled()) {
          return Task.cancelled();
        } else {
          return task.continueWith(continuation);
        }
      }
    }, executor);
  }

  /**
   * Runs a continuation when a task completes successfully, forwarding along
   * {@link java.lang.Exception}s or cancellation.
   */
  public  Task onSuccess(
      final Continuation continuation) {
    return onSuccess(continuation, IMMEDIATE_EXECUTOR, null);
  }

  /**
   * Runs a continuation when a task completes successfully, forwarding along
   * {@link java.lang.Exception}s or cancellation.
   */
  public  Task onSuccess(
      final Continuation continuation, CancellationToken ct) {
    return onSuccess(continuation, IMMEDIATE_EXECUTOR, ct);
  }

  /**
   * Runs a continuation when a task completes successfully, forwarding along
   * {@link java.lang.Exception}s or cancellation.
   */
  public  Task onSuccessTask(
      final Continuation> continuation, Executor executor) {
    return onSuccessTask(continuation, executor, null);
  }

  /**
   * Runs a continuation when a task completes successfully, forwarding along
   * {@link java.lang.Exception}s or cancellation.
   */
  public  Task onSuccessTask(
      final Continuation> continuation, Executor executor,
      final CancellationToken ct) {
    return continueWithTask(new Continuation>() {
      @Override
      public Task then(Task task) {
        if (ct != null && ct.isCancellationRequested()) {
          return Task.cancelled();
        }

        if (task.isFaulted()) {
          return Task.forError(task.getError());
        } else if (task.isCancelled()) {
          return Task.cancelled();
        } else {
          return task.continueWithTask(continuation);
        }
      }
    }, executor);
  }

  /**
   * Runs a continuation when a task completes successfully, forwarding along
   * {@link java.lang.Exception}s or cancellation.
   */
  public  Task onSuccessTask(
      final Continuation> continuation) {
    return onSuccessTask(continuation, IMMEDIATE_EXECUTOR);
  }

  /**
   * Runs a continuation when a task completes successfully, forwarding along
   * {@link java.lang.Exception}s or cancellation.
   */
  public  Task onSuccessTask(
      final Continuation> continuation,
      CancellationToken ct) {
    return onSuccessTask(continuation, IMMEDIATE_EXECUTOR, ct);
  }

  /**
   * Handles the non-async (i.e. the continuation doesn't return a Task) continuation case, passing
   * the results of the given Task through to the given continuation and using the results of that
   * call to set the result of the TaskContinuationSource.
   *
   * @param tcs
   *          The TaskContinuationSource that will be orchestrated by this call.
   * @param continuation
   *          The non-async continuation.
   * @param task
   *          The task being completed.
   * @param executor
   *          The executor to use when running the continuation (allowing the continuation to be
   *          scheduled on a different thread).
   */
  private static  void completeImmediately(
      final bolts.TaskCompletionSource tcs,
      final Continuation continuation, final Task task,
      Executor executor, final CancellationToken ct) {
    executor.execute(new Runnable() {
      @Override
      public void run() {
        if (ct != null && ct.isCancellationRequested()) {
          tcs.setCancelled();
          return;
        }

        try {
          TContinuationResult result = continuation.then(task);
          tcs.setResult(result);
        } catch (CancellationException e) {
          tcs.setCancelled();
        } catch (Exception e) {
          tcs.setError(e);
        }
      }
    });
  }

  /**
   * Handles the async (i.e. the continuation does return a Task) continuation case, passing the
   * results of the given Task through to the given continuation to get a new Task. The
   * TaskCompletionSource's results are only set when the new Task has completed, unwrapping the
   * results of the task returned by the continuation.
   *
   * @param tcs
   *          The TaskContinuationSource that will be orchestrated by this call.
   * @param continuation
   *          The async continuation.
   * @param task
   *          The task being completed.
   * @param executor
   *          The executor to use when running the continuation (allowing the continuation to be
   *          scheduled on a different thread).
   */
  private static  void completeAfterTask(
      final bolts.TaskCompletionSource tcs,
      final Continuation> continuation,
      final Task task, final Executor executor,
      final CancellationToken ct) {
    executor.execute(new Runnable() {
      @Override
      public void run() {
        if (ct != null && ct.isCancellationRequested()) {
          tcs.setCancelled();
          return;
        }

        try {
          Task result = continuation.then(task);
          if (result == null) {
            tcs.setResult(null);
          } else {
            result.continueWith(new Continuation() {
              @Override
              public Void then(Task task) {
                if (ct != null && ct.isCancellationRequested()) {
                  tcs.setCancelled();
                  return null;
                }

                if (task.isCancelled()) {
                  tcs.setCancelled();
                } else if (task.isFaulted()) {
                  tcs.setError(task.getError());
                } else {
                  tcs.setResult(task.getResult());
                }
                return null;
              }
            });
          }
        } catch (CancellationException e) {
          tcs.setCancelled();
        } catch (Exception e) {
          tcs.setError(e);
        }
      }
    });
  }

  private void runContinuations() {
    synchronized (lock) {
      for (Continuation continuation : continuations) {
        try {
          continuation.then(this);
        } catch (RuntimeException e) {
          throw e;
        } catch (Exception e) {
          throw new RuntimeException(e);
        }
      }
      continuations = null;
    }
  }

  /**
   * Sets the cancelled flag on the Task if the Task hasn't already been completed.
   */
  /* package */ boolean trySetCancelled() {
    synchronized (lock) {
      if (complete) {
        return false;
      }
      complete = true;
      cancelled = true;
      lock.notifyAll();
      runContinuations();
      return true;
    }
  }

  /**
   * Sets the result on the Task if the Task hasn't already been completed.
   */
  /* package */ boolean trySetResult(TResult result) {
    synchronized (lock) {
      if (complete) {
        return false;
      }
      complete = true;
      Task.this.result = result;
      lock.notifyAll();
      runContinuations();
      return true;
    }
  }

  /**
   * Sets the error on the Task if the Task hasn't already been completed.
   */
  /* package */ boolean trySetError(Exception error) {
    synchronized (lock) {
      if (complete) {
        return false;
      }
      complete = true;
      Task.this.error = error;
      lock.notifyAll();
      runContinuations();
      return true;
    }
  }

  /**
   * @deprecated Please use {@link bolts.TaskCompletionSource} instead.
   */
  public class TaskCompletionSource extends bolts.TaskCompletionSource {

    /* package */ TaskCompletionSource() {
    }
  }

  private static Task TASK_NULL = new Task<>(null);
  private static Task TASK_TRUE = new Task<>((Boolean) true);
  private static Task TASK_FALSE = new Task<>((Boolean) false);
  private static Task TASK_CANCELLED = new Task(true);
}
    

    

    

            

    

            



    
    






    
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