#region Apache License 2.0
/*
Nuclex .NET Framework
Copyright (C) 2002-2024 Markus Ewald / Nuclex Development Labs

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.
*/
#endregion // Apache License 2.0

#if !NO_CONCURRENT_COLLECTIONS

using System;
using System.Threading;
using System.Collections.Generic;

using NUnit.Framework;

namespace Nuclex.Support.Threading {

  /// <summary>Unit Test for the parallel background worker class</summary>
  [TestFixture]
  internal class ParallelBackgroundWorkerTest {

    #region class TestWorker

    /// <summary>Implementation of a background worker used for unit testing</summary>
    #pragma warning disable 0618
    private class TestWorker : ParallelBackgroundWorker<object> {
    #pragma warning restore 0618

      /// <summary>Initializes a new parallel background worker with unlimited threads</summary>
      public TestWorker() : base() { }

      /// <summary>
      ///   Initializes a new parallel background worker running the specified number
      ///   of tasks in parallel
      /// </summary>
      /// <param name="threadCount">
      ///   Number of tasks to run in parallel (if positive) or number of CPU cores to leave
      ///   unused (if negative).
      /// </param>
      /// <remarks>
      ///   If a negative number of threads is used, at least one thread will be always
      ///   be created, so specifying -2 on a single-core system will still occupy
      ///   the only core.
      /// </remarks>
      public TestWorker(int threadCount) : base(threadCount) { }

      /// <summary>
      ///   Initializes a new parallel background worker that uses the specified name for
      ///   its worker threads.
      /// </summary>
      /// <param name="name">Name that will be assigned to the worker threads</param>
      public TestWorker(string name) : base(name) { }

      /// <summary>
      ///   Initializes a new parallel background worker that uses the specified name for
      ///   its worker threads and running the specified number of tasks in parallel.
      /// </summary>
      /// <param name="name">Name that will be assigned to the worker threads</param>
      /// <param name="threadCount">
      ///   Number of tasks to run in parallel (if positive) or number of CPU cores to leave
      ///   unused (if negative).
      /// </param>
      /// <remarks>
      ///   If a negative number of threads is used, at least one thread will be always
      ///   be created, so specifying -2 on a single-core system will still occupy
      ///   the only core.
      /// </remarks>
      public TestWorker(string name, int threadCount) : base(name, threadCount) { }

      /// <summary>Called in a thread to execute a single task</summary>
      /// <param name="task">Task that should be executed</param>
      /// <param name="cancellationToken">
      ///   Cancellation token through which the method can be signalled to cancel
      /// </param>
      protected override void Run(object task, CancellationToken cancellationToken) {
        if(this.ThrowException) {
          throw new Exception("Something went wrong");
        }

        if(this.WaitEvent != null) {
          this.WaitEvent.WaitOne();
        }

        this.WasCancelled = cancellationToken.IsCancellationRequested;

        if(this.Tasks != null) {
          lock(this.Tasks) {
            this.Tasks.Add(task);
          }
        }
      }

      /// <summary>Whether the work tasks should throw exceptions</summary>
      public bool ThrowException;
      /// <summary>Event that can be used to stop work tasks from completing</summary>
      public ManualResetEvent WaitEvent;

      /// <summary>Set by work tasks if they have been cancelled</summary>
      public bool WasCancelled;
      /// <summary>Work tasks that have reached execution</summary>
      public ICollection<object> Tasks;

    }

    #endregion // class TestWorker

    /// <summary>Verifies that the background worker has a default constructor</summary>
    [Test]
    public void CanBeDefaultConstructed() {
      using(new TestWorker()) { }
    }

    /// <summary>
    ///   Verifies that a background worker can be constructed that uses a fixed number
    ///   of threads
    /// </summary>
    [Test]
    public void CanUseFixedNumberOfThreads() {
      using(new TestWorker(4)) { }
    }

    /// <summary>
    ///   Verifies that a background worker can be constructed that leaves free a fixed
    ///   number of CPU cores
    /// </summary>
    [Test]
    public void CanPreserveFixedNumberOfCores() {
      using(new TestWorker(-2)) { }
    }

    /// <summary>
    ///   Verifies that a background worker can be constructed using a specific name
    ///   for its worker threads
    /// </summary>
    [Test]
    public void CanUseNamedThreads() {
      using(new TestWorker("Test Task Thread")) { }
    }

    /// <summary>
    ///   Verifies that a background worker can be constructed that uses a fixed number
    ///   of threads using a specific name
    /// </summary>
    [Test]
    public void CanUseFixedNumberOfNamedThreads() {
      using(new TestWorker("Test Task Thread", 4)) { }
    }

    /// <summary>
    ///   Verifies that a background worker can be constructed that leaves free a fixed
    ///   number of CPU cores and uses a specific name for its worker threads.
    /// </summary>
    [Test]
    public void CanPreserveFixedNumberOfCoresAndUseNamedThreads() {
      using(new TestWorker("Test Task Thread", -2)) { }
    }

    /// <summary>
    ///   Verifies that exceptions happening inside the tasks are collected and re-thrown
    ///   in the Join() method.
    /// </summary>
    [Test]
    public void ExceptionsAreReThrownInJoin() {
      using(var testWorker = new TestWorker()) {
        testWorker.ThrowException = true;
        testWorker.AddTask(new object());
        testWorker.AddTask(new object());

        Assert.Throws<AggregateException>(
          () => {
            testWorker.Join();
          }
        );

        try {
          testWorker.Join();
          Assert.Fail(
            "Calling ParallelBackgroundWorker.Join() multiple times should re-throw " +
            "exceptions multiple times"
          );
        }
        catch(AggregateException aggregateException) {
          Assert.AreEqual(2, aggregateException.InnerExceptions.Count);
        }
      }
    }

    /// <summary>
    ///   Verifies that tasks can be cancelled while they are running
    /// </summary>
    [Test]
    public void TasksCanBeCancelled() {
      using(var waitEvent = new ManualResetEvent(false)) {
        using(var testWorker = new TestWorker()) {
          testWorker.WaitEvent = waitEvent;

          testWorker.AddTask(new object());
          testWorker.CancelRunningTasks();

          waitEvent.Set();

          Assert.IsTrue(testWorker.Wait(1000));

          Assert.IsTrue(testWorker.WasCancelled);
        }
      } // disposes waitEvent
    }

    /// <summary>Verifies that calling Join() waits for all queued tasks</summary>
    [Test]
    public void JoinWaitsForQueuedTasks() {
      var tasks = new List<object>(100);
      for(int index = 0; index < 100; ++index) {
        tasks.Add(new object());
      }

      using(var waitEvent = new ManualResetEvent(false)) {
        using(var testWorker = new TestWorker(2)) {
          testWorker.WaitEvent = waitEvent;
          testWorker.Tasks = new List<object>();
          for(int index = 0; index < 100; ++index) {
            testWorker.AddTask(tasks[index]);
          }

          CollectionAssert.IsEmpty(testWorker.Tasks);

          waitEvent.Set();
          testWorker.Join();

          lock(testWorker.Tasks) {
            CollectionAssert.AreEquivalent(tasks, testWorker.Tasks);
          }
        }
      } // disposes waitEvent
    }

  }

} // namespace Nuclex.Support.Threading

#endif // !NO_CONCURRENT_COLLECTIONS