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/*
 * Copyright 2001-2016 Artima, Inc.
 *
 * 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 org.scalatest

import scala.concurrent.Future
import scala.concurrent.ExecutionContext
import org.scalactic.{Or, Good, Bad}
import scala.util.{Try, Success, Failure}
import exceptions.TestCanceledException
import exceptions.TestPendingException
import Suite.anExceptionThatShouldCauseAnAbort
import scala.concurrent.ExecutionException

/*
Note, the reason Outcome or Throwable is used here instead of Try[Outcome] is
to avoid confusion over the Try that comes back from the Future[Outcome]. Only
run-aborting exceptions will be contained in scala.util.Failures in this case.
Other exceptions will show up as Success(org.scalatest.Failed) or Success(org.scalatest.Canceled).
And this confusion of Success(Failed) is what the Or is intended to alleviate.
*/

/**
 * Wrapper class for Future[Outcome] that presents a more convenient API for 
 * manipulation in withFixture methods in async styles.
 *
 * 
 * This type serves as the result type of both test functions and withFixture methods
 * in ScalaTest's async styles. A Future[Outcome] is not used as this result type
 * for two reasons. First, Outcome treats exceptions specially, and as a result
 * methods on Future would usually not yield the desired Future[Outcome] result.
 * Only run-aborting exceptions should result in a failed Future[Outcome]. Any other thrown exception
 * other than TestCanceledException or TestPendingException
 * should result in a successfulFuture containing a org.scalatest.Failed.
 * A thrown TestCanceledException should result in a successful Future
 * containing an org.scalatest.Canceled; A thrown TestPendingException should result in
 * a successful Future containing a org.scalatest.Pending.
 * If manipulating a Future[Outcome] directly, by contrast, any thrown exception would result in 
 * a failed Future.
 * 
 *
 * 
 * Additionally, to be consistent with corresponding transformations in traditional testing styles, 
 * methods registering callbacks should return a new future outcome that doesn't complete until
 * both the original future outcome has completed and the subsequent callback has completed execution.
 * Additionally, if the callback itself throws an exception, that exception should determine the result
 * of the future outcome returned by the callback registration method. This behavior is rather inconvenient
 * to obtain on the current Future API, so FutureOutcome provides well-named
 * methods that have this behavior.
 * 
 *
 * 
 * Lastly, the FutureOutcome is intended to help prevent confusion by eliminating the need
 * to work with types like scala.util.Success(org.scalatest.Failed). For this purpose a
 * org.scalactic.Or is used instead of a scala.util.Try to describe results
 * of FutureOutcome.
 * 
 *
 * 
 * A FutureOutcome represents a computation that can result in an Outcome or an "abort." An abort means
 * that a run-aborting exception occurred during the computation. Any other, non-run-aborting exception will be represented
 * as an non-Succeeded Outcome: one of Failed, Canceled, or Pending.
 * 
 * 
 * 
 * The methods of FutureOutcome include the following callback registration methods:
 * 
 *
 * 
 * onSucceededThen - registers a callback to be executed if the future outcome is Succeeded.
 * onFailedThen - registers a callback to be executed if the future outcome is Failed.
 * onCanceledThen - registers a callback to be executed if the future outcome is Canceled.
 * onPendingThen - registers a callback to be executed if the future outcome is Pending.
 * onOutcomeThen - registers a callback to be executed if the future outcome is actually an Outcome
 *      and not an abort.
 * onAbortedThen - registers a callback to be executed if the future outcome aborts.
 * onCompletedThen - registers a callback to be executed upon completion no matter how the future outcome completes.
 * 
 *
 * 
 * The callback methods listed previously can be used to perform a side effect once a FutureOutcome completes. To change an
 * Outcome into a different Outcome asynchronously, use the change registration method, which takes a function
 * from Outcome to Outcome. The other methods on FutureOutcome, isCompleted and
 * value, allow you to poll a FutureOutcome. None of the methods on FutureOutcome block.
 * Lastly, because an implicit Futuristic instance is provided for
 * FutureOutcome, you can use complete-lastly syntax
 * with FutureOutcome.
 * 
 */
open class FutureOutcome(private[scalatest] val underlying: Future[Outcome]) {
  // TODO: add tests for pretty toString

  /**
   * Registers a callback function to be executed after this future completes, returning
   * a new future that completes only after the callback has finished execution.
   *
   * 
   * The resulting FutureOutcome will have the same result as this FutureOutcome, unless
   * the callback completes abruptly with an exception. In that case, the resulting FutureOutcome
   * will be determined by the type of the thrown exception:
   * 
   *
   * 
   * TestPendingException
 - Good(Pending)
   * TestCanceledException
 - Good(Canceled(<the exception>))
   * Any non-run-aborting Throwable
 - Good(Failed(<the exception>))
   * A run-aborting Throwable
 - Bad(<the run-aborting exception>)
   * 
   *
   * 
   * For more information on run-aborting exceptions, see the Run-aborting exceptions section
   * in the main Scaladoc for trait Suite.
   * 
   *
   * @param callback a side-effecting function to execute when this FutureOutcome completes
   * @param executionContext an execution context that provides a strategy for executing the callback function
   * @return a new FutureOutcome that will complete only after this FutureOutcome
   *    and, subsequently, the passed callback function have completed execution.
   */
  def onCompletedThen(callback: (Outcome Or Throwable) => Unit)(implicit executionContext: ExecutionContext): FutureOutcome = {
    FutureOutcome {
      underlying recoverWith {
        case ex =>
          try {
            callback(Bad(ex))
            Future.failed(ex)
          }
          catch {
            case _: TestPendingException => Future.successful(Pending)
            case ex: TestCanceledException => Future.successful(Canceled(ex))
            case ex: Throwable if !anExceptionThatShouldCauseAnAbort(ex) => Future.successful(Failed(ex))
            case ex: Throwable => Future.failed(new ExecutionException(ex))
          }
      } flatMap { outcome =>
        try {
          callback(Good(outcome))
          Future.successful(outcome)
        }
        catch {
          case _: TestPendingException => Future.successful(Pending)
          case ex: TestCanceledException => Future.successful(Canceled(ex))
          case ex: Throwable if !anExceptionThatShouldCauseAnAbort(ex) => Future.successful(Failed(ex))
          case ex: Throwable => Future.failed(new ExecutionException(ex))
        }
      }
    }
  }

  /**
   * Registers a callback function to be executed if this future completes with
   * Succeeded, returning a new future that completes only after the
   * callback has finished execution.
   *
   * 
   * The resulting FutureOutcome will have the same result as this FutureOutcome, unless
   * the callback completes abruptly with an exception. In that case, the resulting FutureOutcome
   * will be determined by the type of the thrown exception:
   * 
   *
   * 
   * TestPendingException
 - Good(Pending)
   * TestCanceledException
 - Good(Canceled(<the exception>))
   * Any non-run-aborting Throwable
 - Good(Failed(<the exception>))
   * A run-aborting Throwable
 - Bad(<the run-aborting exception>)
   * 
   *
   * 
   * For more information on run-aborting exceptions, see the Run-aborting exceptions section
   * in the main Scaladoc for trait Suite.
   * 
   *
   * @param callback a side-effecting function to execute if and when this FutureOutcome completes with Succeeded
   * @param executionContext an execution context that provides a strategy for executing the callback function
   * @return a new FutureOutcome that will complete only after this FutureOutcome
   *    has completed and, if this FutureOutcome completes with Succeeded, the
   *    passed callback function has completed execution.
   */
  def onSucceededThen(callback: => Unit)(implicit executionContext: ExecutionContext): FutureOutcome = {
    FutureOutcome {
      underlying flatMap { outcome =>
        if (outcome.isSucceeded) {
          try {
            callback
            Future.successful(outcome)
          }
          catch {
            case _: TestPendingException => Future.successful(Pending)
            case ex: TestCanceledException => Future.successful(Canceled(ex))
            case ex: Throwable if !anExceptionThatShouldCauseAnAbort(ex) => Future.successful(Failed(ex))
            case ex: Throwable => Future.failed(new ExecutionException(ex))
          }
        } else Future.successful(outcome)
      }
    }
  }

  /**
   * Registers a callback function to be executed if this future completes with
   * Failed, returning a new future that completes only after the
   * callback has finished execution.
   *
   * 
   * The resulting FutureOutcome will have the same result as this FutureOutcome, unless
   * the callback completes abruptly with an exception. In that case, the resulting FutureOutcome
   * will be determined by the type of the thrown exception:
   * 
   *
   * 
   * TestPendingException
 - Good(Pending)
   * TestCanceledException
 - Good(Canceled(<the exception>))
   * Any non-run-aborting Throwable
 - Good(Failed(<the exception>))
   * A run-aborting Throwable
 - Bad(<the run-aborting exception>)
   * 
   *
   * 
   * For more information on run-aborting exceptions, see the Run-aborting exceptions section
   * in the main Scaladoc for trait Suite.
   * 
   *
   * @param callback a side-effecting function to execute if and when this FutureOutcome completes with Failed
   * @param executionContext an execution context that provides a strategy for executing the callback function
   * @return a new FutureOutcome that will complete only after this FutureOutcome
   *    has completed and, if this FutureOutcome completes with Failed, the
   *    passed callback function has completed execution.
   */
  def onFailedThen(callback: Throwable => Unit)(implicit executionContext: ExecutionContext): FutureOutcome = {
    FutureOutcome {
      underlying flatMap { outcome =>
        outcome match {
          case Failed(originalEx) =>
            try {
              callback(originalEx)
              Future.successful(outcome)
            }
            catch {
              case _: TestPendingException => Future.successful(Pending)
              case ex: TestCanceledException => Future.successful(Canceled(ex))
              case ex: Throwable if !anExceptionThatShouldCauseAnAbort(ex) => Future.successful(Failed(ex))
              case ex: Throwable => Future.failed(new ExecutionException(ex))
            }
          case _ =>
            Future.successful(outcome)
        }
      }
    }
  }

  /**
   * Registers a callback function to be executed if this future completes with
   * Canceled, returning a new future that completes only after the
   * callback has finished execution.
   *
   * 
   * The resulting FutureOutcome will have the same result as this FutureOutcome, unless
   * the callback completes abruptly with an exception. In that case, the resulting FutureOutcome
   * will be determined by the type of the thrown exception:
   * 
   *
   * 
   * TestPendingException
 - Good(Pending)
   * TestCanceledException
 - Good(Canceled(<the exception>))
   * Any non-run-aborting Throwable
 - Good(Failed(<the exception>))
   * A run-aborting Throwable
 - Bad(<the run-aborting exception>)
   * 
   *
   * 
   * For more information on run-aborting exceptions, see the Run-aborting exceptions section
   * in the main Scaladoc for trait Suite.
   * 
   *
   * @param callback a side-effecting function to execute if and when this FutureOutcome completes with Canceled
   * @param executionContext an execution context that provides a strategy for executing the callback function
   * @return a new FutureOutcome that will complete only after this FutureOutcome
   *    has completed and, if this FutureOutcome completes with Canceled, the
   *    passed callback function has completed execution.
   */
  def onCanceledThen(callback: TestCanceledException => Unit)(implicit executionContext: ExecutionContext): FutureOutcome = {
    FutureOutcome {
      underlying flatMap { outcome =>
        outcome match {
          case Canceled(originalEx) =>
            try {
              callback(originalEx)
              Future.successful(outcome)
            }
            catch {
              case _: TestPendingException => Future.successful(Pending)
              case ex: TestCanceledException => Future.successful(Canceled(ex))
              case ex: Throwable if !anExceptionThatShouldCauseAnAbort(ex) => Future.successful(Failed(ex))
              case ex: Throwable => Future.failed(new ExecutionException(ex))
            }
          case _ =>
            Future.successful(outcome)
        }
      }
    }
  }

  /**
   * Registers a callback function to be executed if this future completes with
   * Pending, returning a new future that completes only after the
   * callback has finished execution.
   *
   * 
   * The resulting FutureOutcome will have the same result as this FutureOutcome, unless
   * the callback completes abruptly with an exception. In that case, the resulting FutureOutcome
   * will be determined by the type of the thrown exception:
   * 
   *
   * 
   * TestPendingException
 - Good(Pending)
   * TestCanceledException
 - Good(Canceled(<the exception>))
   * Any non-run-aborting Throwable
 - Good(Failed(<the exception>))
   * A run-aborting Throwable
 - Bad(<the run-aborting exception>)
   * 
   *
   * 
   * For more information on run-aborting exceptions, see the Run-aborting exceptions section
   * in the main Scaladoc for trait Suite.
   * 
   *
   * @param callback a side-effecting function to execute if and when this FutureOutcome completes with Pending
   * @param executionContext an execution context that provides a strategy for executing the callback function
   * @return a new FutureOutcome that will complete only after this FutureOutcome
   *    has completed and, if this FutureOutcome completes with Pending, the
   *    passed callback function has completed execution.
   */
  def onPendingThen(callback: => Unit)(implicit executionContext: ExecutionContext): FutureOutcome = {
    FutureOutcome {
      underlying flatMap { outcome =>
        if (outcome.isPending) {
          try {
            callback
            Future.successful(outcome)
          }
          catch {
            case _: TestPendingException => Future.successful(Pending)
            case ex: TestCanceledException => Future.successful(Canceled(ex))
            case ex: Throwable if !anExceptionThatShouldCauseAnAbort(ex) => Future.successful(Failed(ex))
            case ex: Throwable => Future.failed(new ExecutionException(ex))
          }
        } else Future.successful(outcome)
      }
    }
  }

  /**
   * Registers a transformation function to be executed if this future completes with any
   * Outcome (i.e., no run-aborting exception is thrown), returning
   * a new FutureOutcome representing the result of passing
   * this FutureOutcome's Outcome result to the given transformation function.
   *
   * 
   * If the passed function completes abruptly with an exception, the resulting FutureOutcome
   * will be determined by the type of the thrown exception:
   * 
   *
   * 
   * TestPendingException
 - Good(Pending)
   * TestCanceledException
 - Good(Canceled(<the exception>))
   * Any non-run-aborting Throwable
 - Good(Failed(<the exception>))
   * A run-aborting Throwable
 - Bad(<the run-aborting exception>)
   * 
   *
   * 
   * For more information on run-aborting exceptions, see the Run-aborting exceptions section
   * in the main Scaladoc for trait Suite.
   * 
   *
   * @param f a transformation function to execute if and when this FutureOutcome completes with an Outcome
   * @param executionContext an execution context that provides a strategy for executing the transformation function
   * @return a new FutureOutcome that will complete only after this FutureOutcome
   *    has completed and, if this FutureOutcome completes with a valid
   *    Outcome, the passed callback function has completed execution.
   */
  def change(f: Outcome => Outcome)(implicit executionContext: ExecutionContext): FutureOutcome = {
    FutureOutcome {
      underlying flatMap { outcome =>
        try Future.successful(f(outcome))
        catch {
          case _: TestPendingException => Future.successful(Pending)
          case ex: TestCanceledException => Future.successful(Canceled(ex))
          case ex: Throwable if !anExceptionThatShouldCauseAnAbort(ex) => Future.successful(Failed(ex))
          case ex: Throwable => Future.failed(new ExecutionException(ex))
        }
      }
    }
  }

  /**
   * Registers a callback function to be executed if this future completes because
   * a run-aborting exception was thrown, returning a new future that completes only after the
   * callback has finished execution.
   *
   * 
   * The resulting FutureOutcome will have the same result as this FutureOutcome, unless
   * the callback completes abruptly with an exception. In that case, the resulting FutureOutcome
   * will be determined by the type of the thrown exception:
   * 
   *
   * 
   * TestPendingException
 - Good(Pending)
   * TestCanceledException
 - Good(Canceled(<the exception>))
   * Any non-run-aborting Throwable
 - Good(Failed(<the exception>))
   * A run-aborting Throwable
 - Bad(<the run-aborting exception>)
   * 
   *
   * 
   * For more information on run-aborting exceptions, see the Run-aborting exceptions section
   * in the main Scaladoc for trait Suite.
   * 
   *
   * @param callback a side-effecting function to execute if and when this FutureOutcome completes with an abort.
   * @param executionContext an execution context that provides a strategy for executing the callback function
   * @return a new FutureOutcome that will complete only after this FutureOutcome
   *    has completed and, if this FutureOutcome completes abnormally with
   *    a run-aborting exception, the passed callback function has completed execution.
   */
  def onAbortedThen(callback: Throwable => Unit)(implicit executionContext: ExecutionContext): FutureOutcome = {
    FutureOutcome {
      underlying recoverWith {
        case originalEx =>
          try {
            callback(originalEx)
            Future.failed(originalEx)
          }
          catch {
            case _: TestPendingException => Future.successful(Pending)
            case ex: TestCanceledException => Future.successful(Canceled(ex))
            case ex: Throwable if !anExceptionThatShouldCauseAnAbort(ex) => Future.successful(Failed(ex))
            case ex: Throwable => Future.failed(new ExecutionException(ex))
          }
      }
    }
  }

  /**
   * Registers a callback function to be executed if this future completes with any
   * Outcome (i.e., no run-aborting exception is thrown), returning
   * a new future that completes only after the callback has finished execution.
   *
   * 
   * The resulting FutureOutcome will have the same result as this FutureOutcome, unless
   * the callback completes abruptly with an exception. In that case, the resulting FutureOutcome
   * will be determined by the type of the thrown exception:
   * 
   *
   * 
   * TestPendingException
 - Good(Pending)
   * TestCanceledException
 - Good(Canceled(<the exception>))
   * Any non-run-aborting Throwable
 - Good(Failed(<the exception>))
   * A run-aborting Throwable
 - Bad(<the run-aborting exception>)
   * 
   *
   * 
   * For more information on run-aborting exceptions, see the Run-aborting exceptions section
   * in the main Scaladoc for trait Suite.
   * 
   *
   * @param callback a side-effecting function to execute if and when this FutureOutcome completes with an Outcome
   *    (i.e., not an abort)
   * @param executionContext an execution context that provides a strategy for executing the callback function
   * @return a new FutureOutcome that will complete only after this FutureOutcome
   *    has completed and, if this FutureOutcome completes with a valid
   *    Outcome, the passed callback function has completed execution.
   */
  def onOutcomeThen(callback: Outcome => Unit)(implicit executionContext: ExecutionContext): FutureOutcome = {
    FutureOutcome {
      underlying flatMap { outcome =>
        try {
          callback(outcome)
          Future.successful(outcome)
        }
        catch {
          case _: TestPendingException => Future.successful(Pending)
          case ex: TestCanceledException => Future.successful(Canceled(ex))
          case ex: Throwable if !anExceptionThatShouldCauseAnAbort(ex) => Future.successful(Failed(ex))
          case ex: Throwable => Future.failed(new ExecutionException(ex))
        }
      }
    }
  }

  /**
   * Indicates whether this FutureOutcome has completed.
   *
   * 
   * This method does not block.
   * 
   *
   * @return true if this FutureOutcome has completed; false otherwise.
   */
  def isCompleted: Boolean = underlying.isCompleted

  /**
   * Returns a value that indicates whether this FutureOutcome has completed,
   * and if so, indicates its result.
   *
   * 
   * If this FutureOutcome has not yet completed, this method will return
   * None. Otherwise, this method will return a Some that contains
   * either a Good[Outcome], if this FutureOutcome completed with
   * a valid Outcome result, or if it completed with a thrown run-aborting
   * exception, a Bad[Throwable].
   * 
   *
   * 
   * For more information on run-aborting exceptions, see the Run-aborting exceptions section
   * in the main Scaladoc for trait Suite.
   * 
   *
   * @return a Some containing an Or value that indicates the result of this
   *    FutureOutcome if it has completed; None otherwise.
   */
  def value: Option[Outcome Or Throwable] =
    underlying.value match {
      case None => None
      case Some(Success(outcome)) => Some(Good(outcome))
      case Some(Failure(ex)) => Some(Bad(ex))
    }

  /**
   * Converts this FutureOutcome to a Future[Outcome].
   *
   * @return the underlying Future[Outcome]
   */
  def toFuture: Future[Outcome] = underlying
}

/**
 * Companion object to FutureOutcomes that contains factory methods for creating already-completed
 * FutureOutcomes.
 */
object FutureOutcome {
  // Make this private so only ScalaTest can make one, so we can "promise" that
  // you'll never need to look for things like a TestCanceledException being passed
  // to onAbortedThen.
  private[scalatest] def apply(underlying: Future[Outcome]): FutureOutcome = new FutureOutcome(underlying)

  /**
   * Factory method that creates an already completed FutureOutcome with a Canceled result.
   */
  def canceled(): FutureOutcome =
    FutureOutcome { Future.successful(Canceled()) }

  /**
   * Factory method that creates an already completed FutureOutcome with a Canceled result
   * whose TestCanceledException contains the specified message.
   *
   * @message the message string to include in the Canceled's TestCanceledException.
   */
  def canceled(message: String): FutureOutcome =
    FutureOutcome { Future.successful(Canceled(message)) }

  /**
   * Factory method that creates an already completed FutureOutcome with a Canceled result
   * whose TestCanceledException contains the specified cause.
   *
   * @cause exception to include as the Canceled's TestCanceledException cause.
   */
  def canceled(cause: Throwable): FutureOutcome =
    FutureOutcome { Future.successful(Canceled(cause)) }

  /**
   * Factory method that creates an already completed FutureOutcome with a Canceled result
   * whose TestCanceledException contains the specified message and cause.
   *
   * @message the message string to include in the Canceled's TestCanceledException.
   * @cause exception to include as the Canceled's TestCanceledException cause.
   */
  def canceled(message: String, cause: Throwable) =
    FutureOutcome { Future.successful(Canceled(message, cause)) }

  /**
   * Factory method that creates an already completed FutureOutcome with a Succeeded result.
   */
  def succeeded: FutureOutcome =
    FutureOutcome { Future.successful(Succeeded) }

  /**
   * Factory method that creates an already completed FutureOutcome with a Failed result.
   */
  def failed(): FutureOutcome =
    FutureOutcome { Future.successful(Failed()) }

  /**
   * Factory method that creates an already completed FutureOutcome with a Failed result
   * containing a TestFailedException with the specified message.
   *
   * @message the message string to include in the Failed's TestFailedException.
   */
  def failed(message: String): FutureOutcome =
    FutureOutcome { Future.successful(Failed(message)) }

  /**
   * Factory method that creates an already completed FutureOutcome with a Failed result
   * containing a TestFailedException with the specified message and cause.
   *
   * @message the message string to include in the Failed's TestFailedException.
   * @cause exception to include as the Failed's TestFailedException cause.
   */
  def failed(message: String, cause: Throwable) =
    FutureOutcome { Future.successful(Failed(message, cause)) }

  /**
   * Factory method that creates an already completed FutureOutcome with a Failed result
   * containing a TestFailedException with the specified cause.
   *
   * @cause exception to include as the Failed's TestFailedException cause.
   */
  def failed(cause: Throwable): FutureOutcome =
    FutureOutcome { Future.successful(Failed(cause)) }

  /**
   * Factory method that creates an already completed FutureOutcome with a Pending result.
   */
  def pending: FutureOutcome =
    FutureOutcome { Future.successful(Pending) }
}

/*
 FutureOutcome.fromOutcome(Canceled("..."))
*/