#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

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

#if UNITTEST

using NUnit.Framework;

namespace Nuclex.Support.Collections {

  /// <summary>Unit Test for the weak collection wrapper</summary>
  [TestFixture]
  internal class WeakCollectionTest {

    #region class Dummy

    /// <summary>Dummy class used to test the weakly referencing collection</summary>
    private class Dummy {

      /// <summary>Initializes a new dummy</summary>
      /// <param name="value">Value that will be stored by the dummy</param>
      public Dummy(int value) {
        this.Value = value;
      }

      /// <summary>
      ///   Determines whether the specified System.Object is equal to
      ///   the current Dummy object.
      /// </summary>
      /// <param name="otherAsObject">
      ///   The System.Object to compare with the current Dummy object
      /// </param>
      /// <returns>
      ///   True if the specified System.Object is equal to the current Dummy object;
      ///   otherwise, false.
      /// </returns>
      public override bool Equals(object otherAsObject) {
        Dummy other = otherAsObject as Dummy;
        if(other == null) {
          return false;
        }
        return this.Value.Equals(other.Value);
      }

      /// <summary>Serves as a hash function for a particular type.</summary>
      /// <returns>A hash code for the current System.Object.</returns>
      public override int GetHashCode() {
        return this.Value.GetHashCode();
      }

      /// <summary>Some value that can be used for testing</summary>
      public int Value;

    }

    #endregion // class Dummy

    #region class ListWithoutICollection

    private class ListWithoutICollection : IList<WeakReference<Dummy>> {
      public int IndexOf(WeakReference<Dummy> item) { throw new NotImplementedException(); }
      public void Insert(int index, WeakReference<Dummy> item) {
        throw new NotImplementedException();
      }
      public void RemoveAt(int index) { throw new NotImplementedException(); }
      public WeakReference<Dummy> this[int index] {
        get { throw new NotImplementedException(); }
        set { throw new NotImplementedException(); }
      }
      public void Add(WeakReference<Dummy> item) { throw new NotImplementedException(); }
      public void Clear() { throw new NotImplementedException(); }
      public bool Contains(WeakReference<Dummy> item) { throw new NotImplementedException(); }
      public void CopyTo(WeakReference<Dummy>[] array, int arrayIndex) {
        throw new NotImplementedException();
      }
      public int Count { get { return 12345; } }
      public bool IsReadOnly { get { throw new NotImplementedException(); } }
      public bool Remove(WeakReference<Dummy> item) { throw new NotImplementedException(); }
      public IEnumerator<WeakReference<Dummy>> GetEnumerator() {
        throw new NotImplementedException();
      }
      IEnumerator IEnumerable.GetEnumerator() { throw new NotImplementedException(); }
    }

    #endregion // class ListWithoutICollection

    /// <summary>Verifies that the constructor of the weak collection is working</summary>
    [Test]
    public void TestConstructor() {
      WeakCollection<Dummy> dummies = new WeakCollection<Dummy>(
        new List<WeakReference<Dummy>>()
      );
      Assert.IsNotNull(dummies);
    }

    /// <summary>
    ///   Test whether the non-typesafe Add() method of the weak collection works
    /// </summary>
    [Test]
    public void TestAddAsObject() {
      WeakCollection<Dummy> dummies = new WeakCollection<Dummy>(
        new List<WeakReference<Dummy>>()
      );

      Dummy oneTwoThreeDummy = new Dummy(12345);
      (dummies as IList).Add((object)oneTwoThreeDummy);

      CollectionAssert.Contains(dummies, oneTwoThreeDummy);
    }

    /// <summary>
    ///   Test whether the non-typesafe Add() method throws an exception if an object is
    ///   added that is not compatible to the collection's item type
    /// </summary>
    [Test]
    public void TestThrowOnAddIncompatibleObject() {
      WeakCollection<Dummy> dummies = new WeakCollection<Dummy>(
        new List<WeakReference<Dummy>>()
      );

      Assert.Throws<ArgumentException>(
        delegate() { (dummies as IList).Add(new object()); }
      );
    }

    /// <summary>
    ///   Test whether the generic Add() method of the weak collection works
    /// </summary>
    [Test]
    public void TestAdd() {
      WeakCollection<Dummy> dummies = new WeakCollection<Dummy>(
        new List<WeakReference<Dummy>>()
      );

      Dummy oneTwoThreeDummy = new Dummy(12345);
      dummies.Add(oneTwoThreeDummy);

      CollectionAssert.Contains(dummies, oneTwoThreeDummy);
    }

    /// <summary>Tests whether the Clear() method works</summary>
    [Test]
    public void TestClear() {
      WeakCollection<Dummy> dummies = new WeakCollection<Dummy>(
        new List<WeakReference<Dummy>>()
      );

      Dummy oneTwoThreeDummy = new Dummy(12345);
      dummies.Add(oneTwoThreeDummy);
      Dummy threeTwoOneDummy = new Dummy(54321);
      dummies.Add(threeTwoOneDummy);

      Assert.AreEqual(2, dummies.Count);

      dummies.Clear();

      Assert.AreEqual(0, dummies.Count);
    }

    /// <summary>Tests whether the Contains() method works</summary>
    [Test]
    public void TestContains() {
      WeakCollection<Dummy> dummies = new WeakCollection<Dummy>(
        new List<WeakReference<Dummy>>()
      );

      Dummy oneTwoThreeDummy = new Dummy(12345);
      dummies.Add(oneTwoThreeDummy);
      Dummy threeTwoOneDummy = new Dummy(54321);

      Assert.IsTrue(dummies.Contains(oneTwoThreeDummy));
      Assert.IsFalse(dummies.Contains(threeTwoOneDummy));
    }

    /// <summary>Tests whether the non-typesafe Contains() method works</summary>
    [Test]
    public void TestContainsWithObject() {
      WeakCollection<Dummy> dummies = new WeakCollection<Dummy>(
        new List<WeakReference<Dummy>>()
      );

      Dummy oneTwoThreeDummy = new Dummy(12345);
      dummies.Add(oneTwoThreeDummy);
      Dummy threeTwoOneDummy = new Dummy(54321);

      Assert.IsTrue((dummies as IList).Contains((object)oneTwoThreeDummy));
      Assert.IsFalse((dummies as IList).Contains((object)threeTwoOneDummy));
    }

    /// <summary>
    ///   Verifies that the Enumerator of the dummy collection correctly
    ///   implements the Reset() method
    /// </summary>
    [Test]
    public void TestEnumeratorReset() {
      WeakCollection<Dummy> dummies = new WeakCollection<Dummy>(
        new List<WeakReference<Dummy>>()
      );
      Dummy oneTwoThreeDummy = new Dummy(123);
      dummies.Add(oneTwoThreeDummy);
      Dummy fourFiveSixDummy = new Dummy(456);
      dummies.Add(fourFiveSixDummy);

      IEnumerator<Dummy> dummyEnumerator = dummies.GetEnumerator();
      Assert.IsTrue(dummyEnumerator.MoveNext());
      Assert.IsTrue(dummyEnumerator.MoveNext());
      Assert.IsFalse(dummyEnumerator.MoveNext());

      dummyEnumerator.Reset();

      Assert.IsTrue(dummyEnumerator.MoveNext());
      Assert.IsTrue(dummyEnumerator.MoveNext());
      Assert.IsFalse(dummyEnumerator.MoveNext());
    }

    /// <summary>Verifies that the IndexOf() method is working as intended</summary>
    [Test]
    public void TestIndexOf() {
      WeakCollection<Dummy> dummies = new WeakCollection<Dummy>(
        new List<WeakReference<Dummy>>()
      );
      Dummy oneTwoThreeDummy = new Dummy(123);
      dummies.Add(oneTwoThreeDummy);
      Dummy fourFiveSixDummy = new Dummy(456);
      dummies.Add(fourFiveSixDummy);
      Dummy sevenEightNineDummy = new Dummy(789);

      Assert.AreEqual(0, dummies.IndexOf(oneTwoThreeDummy));
      Assert.AreEqual(1, dummies.IndexOf(fourFiveSixDummy));
      Assert.AreEqual(-1, dummies.IndexOf(sevenEightNineDummy));
    }

    /// <summary>
    ///   Verifies that the non-typesafe IndexOf() method is working as intended
    /// </summary>
    [Test]
    public void TestIndexOfWithObject() {
      WeakCollection<Dummy> dummies = new WeakCollection<Dummy>(
        new List<WeakReference<Dummy>>()
      );
      Dummy oneTwoThreeDummy = new Dummy(123);
      dummies.Add(oneTwoThreeDummy);
      Dummy fourFiveSixDummy = new Dummy(456);
      dummies.Add(fourFiveSixDummy);
      Dummy sevenEightNineDummy = new Dummy(789);

      Assert.AreEqual(0, (dummies as IList).IndexOf((object)oneTwoThreeDummy));
      Assert.AreEqual(1, (dummies as IList).IndexOf((object)fourFiveSixDummy));
      Assert.AreEqual(-1, (dummies as IList).IndexOf((object)sevenEightNineDummy));
    }

    /// <summary>
    ///   Verifies that an exception is thrown if an incompatible object is passed to
    ///   the non-typesafe variant of the IndexOf() method
    /// </summary>
    [Test]
    public void TestThrowOnIndexOfWithIncompatibleObject() {
      WeakCollection<Dummy> dummies = new WeakCollection<Dummy>(
        new List<WeakReference<Dummy>>()
      );

      Assert.Throws<ArgumentException>(
        delegate() { Assert.IsNull((dummies as IList).IndexOf(new object())); }
      );
    }

    /// <summary>Test whether the IndexOf() method can cope with null references</summary>
    [Test]
    public void TestIndexOfNull() {
      WeakCollection<Dummy> dummies = new WeakCollection<Dummy>(
        new List<WeakReference<Dummy>>()
      );

      Assert.AreEqual(-1, dummies.IndexOf(null));
      dummies.Add(null);
      Assert.AreEqual(0, dummies.IndexOf(null));
    }

    /// <summary>
    ///   Verifies that the CopyTo() method of the weak collection works
    /// </summary>
    [Test]
    public void TestCopyToArray() {
      WeakCollection<Dummy> dummies = new WeakCollection<Dummy>(
        new List<WeakReference<Dummy>>()
      );
      Dummy oneTwoThreeDummy = new Dummy(123);
      dummies.Add(oneTwoThreeDummy);
      Dummy fourFiveSixDummy = new Dummy(456);
      dummies.Add(fourFiveSixDummy);

      Dummy[] inputDummies = new Dummy[] { oneTwoThreeDummy, fourFiveSixDummy };
      Dummy[] outputDummies = new Dummy[dummies.Count];

      dummies.CopyTo(outputDummies, 0);

      CollectionAssert.AreEqual(inputDummies, outputDummies);
    }

    /// <summary>
    ///   Verifies that the CopyTo() method of the weak collection throws an exception
    ///   if the target array is too small to hold the collection's contents
    /// </summary>
    [Test]
    public void TestThrowOnCopyToTooSmallArray() {
      WeakCollection<Dummy> dummies = new WeakCollection<Dummy>(
        new List<WeakReference<Dummy>>()
      );
      Dummy oneTwoThreeDummy = new Dummy(123);
      dummies.Add(oneTwoThreeDummy);
      Dummy fourFiveSixDummy = new Dummy(456);
      dummies.Add(fourFiveSixDummy);

      Dummy[] outputStrings = new Dummy[dummies.Count - 1];
      Assert.Throws<ArgumentException>(
        delegate() { dummies.CopyTo(outputStrings, 0); }
      );
    }

    /// <summary>
    ///   Verifies that the CopyTo() method of the transforming read only collection
    ///   works if invoked via the ICollection interface
    /// </summary>
    [Test]
    public void TestCopyToArrayViaICollection() {
      WeakCollection<Dummy> dummies = new WeakCollection<Dummy>(
        new List<WeakReference<Dummy>>()
      );
      Dummy oneTwoThreeDummy = new Dummy(123);
      dummies.Add(oneTwoThreeDummy);
      Dummy fourFiveSixDummy = new Dummy(456);
      dummies.Add(fourFiveSixDummy);

      Dummy[] inputDummies = new Dummy[] { oneTwoThreeDummy, fourFiveSixDummy };
      Dummy[] outputDummies = new Dummy[dummies.Count];

      (dummies as ICollection).CopyTo(outputDummies, 0);

      CollectionAssert.AreEqual(inputDummies, outputDummies);
    }

    /// <summary>
    ///   Verifies that the Insert() method correctly shifts items in the collection
    /// </summary>
    [Test]
    public void TestInsert() {
      WeakCollection<Dummy> dummies = new WeakCollection<Dummy>(
        new List<WeakReference<Dummy>>()
      );
      Dummy oneTwoThreeDummy = new Dummy(123);
      dummies.Add(oneTwoThreeDummy);

      Dummy fourFiveSixDummy = new Dummy(456);
      dummies.Insert(0, fourFiveSixDummy);

      Assert.AreEqual(2, dummies.Count);
      Assert.AreSame(fourFiveSixDummy, dummies[0]);
      Assert.AreSame(oneTwoThreeDummy, dummies[1]);
    }

    /// <summary>
    ///   Verifies that the non-typesafe Insert() method correctly shifts items in
    ///   the collection
    /// </summary>
    [Test]
    public void TestInsertObject() {
      WeakCollection<Dummy> dummies = new WeakCollection<Dummy>(
        new List<WeakReference<Dummy>>()
      );
      Dummy oneTwoThreeDummy = new Dummy(123);
      dummies.Add(oneTwoThreeDummy);

      Dummy fourFiveSixDummy = new Dummy(456);
      (dummies as IList).Insert(0, (object)fourFiveSixDummy);

      Assert.AreEqual(2, dummies.Count);
      Assert.AreSame(fourFiveSixDummy, dummies[0]);
      Assert.AreSame(oneTwoThreeDummy, dummies[1]);
    }

    /// <summary>
    ///   Verifies that the non-typesafe Insert() method correctly shifts items in
    ///   the collection
    /// </summary>
    [Test]
    public void TestThrowOnInsertIncompatibleObject() {
      WeakCollection<Dummy> dummies = new WeakCollection<Dummy>(
        new List<WeakReference<Dummy>>()
      );
      Dummy oneTwoThreeDummy = new Dummy(123);
      dummies.Add(oneTwoThreeDummy);

      Assert.Throws<ArgumentException>(
        delegate() { (dummies as IList).Insert(0, new object()); }
      );
    }

    /// <summary>
    ///   Checks whether the IsFixedSize property of the weak collection returns
    ///   the expected result for a weak collection based on a fixed array
    /// </summary>
    [Test]
    public void TestIsFixedSizeViaIList() {
      Dummy oneTwoThreeDummy = new Dummy(123);
      Dummy fourFiveSixDummy = new Dummy(456);

      WeakReference<Dummy>[] dummyReferences = new WeakReference<Dummy>[] {
        new WeakReference<Dummy>(oneTwoThreeDummy),
        new WeakReference<Dummy>(fourFiveSixDummy)
      };
      WeakCollection<Dummy> dummies = new WeakCollection<Dummy>(dummyReferences);

      Assert.IsTrue((dummies as IList).IsFixedSize);
    }

    /// <summary>
    ///   Tests whether the IsReadOnly property of the weak collection works
    /// </summary>
    [Test]
    public void TestIsReadOnly() {
      Dummy oneTwoThreeDummy = new Dummy(123);
      Dummy fourFiveSixDummy = new Dummy(456);

      List<WeakReference<Dummy>> dummyReferences = new List<WeakReference<Dummy>>();
      dummyReferences.Add(new WeakReference<Dummy>(oneTwoThreeDummy));
      dummyReferences.Add(new WeakReference<Dummy>(fourFiveSixDummy));

      ReadOnlyList<WeakReference<Dummy>> readOnlyDummyReferences =
        new ReadOnlyList<WeakReference<Dummy>>(dummyReferences);

      WeakCollection<Dummy> dummies = new WeakCollection<Dummy>(dummyReferences);
      WeakCollection<Dummy> readOnlydummies = new WeakCollection<Dummy>(
        readOnlyDummyReferences
      );

      Assert.IsFalse(dummies.IsReadOnly);
      Assert.IsTrue(readOnlydummies.IsReadOnly);
    }

    /// <summary>
    ///   Tests whether the IsSynchronized property of the weak collection works
    /// </summary>
    [Test]
    public void TestIsSynchronized() {
      WeakCollection<Dummy> dummies = new WeakCollection<Dummy>(
        new List<WeakReference<Dummy>>()
      );

      Assert.IsFalse((dummies as IList).IsSynchronized);
    }

    /// <summary>Tests the indexer of the weak collection</summary>
    [Test]
    public void TestIndexer() {
      WeakCollection<Dummy> dummies = new WeakCollection<Dummy>(
        new List<WeakReference<Dummy>>()
      );
      Dummy oneTwoThreeDummy = new Dummy(123);
      dummies.Add(oneTwoThreeDummy);
      Dummy fourFiveSixDummy = new Dummy(456);
      dummies.Add(fourFiveSixDummy);

      Assert.AreSame(oneTwoThreeDummy, dummies[0]);
      Assert.AreSame(fourFiveSixDummy, dummies[1]);

      dummies[0] = fourFiveSixDummy;

      Assert.AreSame(fourFiveSixDummy, dummies[0]);
    }

    /// <summary>Tests the non-typesafe indexer of the weak collection</summary>
    [Test]
    public void TestIndexerWithObject() {
      WeakCollection<Dummy> dummies = new WeakCollection<Dummy>(
        new List<WeakReference<Dummy>>()
      );
      Dummy oneTwoThreeDummy = new Dummy(123);
      dummies.Add(oneTwoThreeDummy);
      Dummy fourFiveSixDummy = new Dummy(456);
      dummies.Add(fourFiveSixDummy);

      Assert.AreSame((object)oneTwoThreeDummy, (dummies as IList)[0]);
      Assert.AreSame((object)fourFiveSixDummy, (dummies as IList)[1]);

      (dummies as IList)[0] = (object)fourFiveSixDummy;

      Assert.AreSame((object)fourFiveSixDummy, (dummies as IList)[0]);
    }

    /// <summary>
    ///   Tests whether the non-typesafe indexer of the weak collection throws
    ///   the correct exception if an incompatible object is assigned
    /// </summary>
    [Test]
    public void TestThrowOnIndexerWithIncompatibleObject() {
      WeakCollection<Dummy> dummies = new WeakCollection<Dummy>(
        new List<WeakReference<Dummy>>()
      );
      Dummy oneTwoThreeDummy = new Dummy(123);
      dummies.Add(oneTwoThreeDummy);

      Assert.Throws<ArgumentException>(
        delegate() { (dummies as IList)[0] = new object(); }
      );
    }

    /// <summary>Tests the Remove() method of the weak collection</summary>
    [Test]
    public void TestRemove() {
      WeakCollection<Dummy> dummies = new WeakCollection<Dummy>(
        new List<WeakReference<Dummy>>()
      );
      Dummy oneTwoThreeDummy = new Dummy(123);
      dummies.Add(oneTwoThreeDummy);
      Dummy fourFiveSixDummy = new Dummy(456);
      dummies.Add(fourFiveSixDummy);

      Assert.AreEqual(2, dummies.Count);
      Assert.IsTrue(dummies.Remove(oneTwoThreeDummy));
      Assert.AreEqual(1, dummies.Count);
      Assert.IsFalse(dummies.Remove(oneTwoThreeDummy));
    }

    /// <summary>Tests the non-typesafe Remove() method of the weak collection</summary>
    [Test]
    public void TestRemoveObject() {
      WeakCollection<Dummy> dummies = new WeakCollection<Dummy>(
        new List<WeakReference<Dummy>>()
      );
      Dummy oneTwoThreeDummy = new Dummy(123);
      dummies.Add(oneTwoThreeDummy);
      Dummy fourFiveSixDummy = new Dummy(456);
      dummies.Add(fourFiveSixDummy);

      Assert.AreEqual(2, dummies.Count);
      (dummies as IList).Remove((object)oneTwoThreeDummy);
      Assert.AreEqual(1, dummies.Count);
    }

    /// <summary>
    ///   Tests whether a null object can be managed by and removed from the weak collection
    /// </summary>
    [Test]
    public void TestRemoveNull() {
      WeakCollection<Dummy> dummies = new WeakCollection<Dummy>(
        new List<WeakReference<Dummy>>()
      );
      dummies.Add(null);

      Assert.AreEqual(1, dummies.Count);
      Assert.IsTrue(dummies.Remove(null));
      Assert.AreEqual(0, dummies.Count);
    }

    /// <summary>
    ///   Tests whether the non-typesafe Remove() method of the weak collection throws
    ///   an exception if an object is tried to be removed that is incompatible with
    ///   the collection's item type
    /// </summary>
    [Test]
    public void TestThrowOnRemoveIncompatibleObject() {
      WeakCollection<Dummy> dummies = new WeakCollection<Dummy>(
        new List<WeakReference<Dummy>>()
      );
      Assert.Throws<ArgumentException>(
        delegate() { (dummies as IList).Remove(new object()); }
      );
    }

    /// <summary>Tests the RemoveAt() method of the weak collection</summary>
    [Test]
    public void TestRemoveAt() {
      WeakCollection<Dummy> dummies = new WeakCollection<Dummy>(
        new List<WeakReference<Dummy>>()
      );
      Dummy oneTwoThreeDummy = new Dummy(123);
      dummies.Add(oneTwoThreeDummy);
      Dummy fourFiveSixDummy = new Dummy(456);
      dummies.Add(fourFiveSixDummy);

      Assert.AreSame(oneTwoThreeDummy, dummies[0]);
      dummies.RemoveAt(0);
      Assert.AreSame(fourFiveSixDummy, dummies[0]);
    }

    /// <summary>
    ///   Verifies that the IsSynchronized property and the SyncRoot property are working
    /// </summary>
    [Test]
    public void TestSynchronization() {
      WeakCollection<Dummy> dummies = new WeakCollection<Dummy>(
        new List<WeakReference<Dummy>>()
      );

      if(!(dummies as ICollection).IsSynchronized) {
        lock((dummies as ICollection).SyncRoot) {
          Assert.AreEqual(0, dummies.Count);
        }
      }
    }

    /// <summary>
    ///   Verifies that the IsSynchronized property and the SyncRoot property are working
    ///   on transforming read only collections based on IList&lt;&gt;s that do not
    ///   implement the ICollection interface
    /// </summary>
    [Test]
    public void TestSynchronizationOfIListWithoutICollection() {
      WeakCollection<Dummy> dummies = new WeakCollection<Dummy>(
        new ListWithoutICollection()
      );

      if(!(dummies as ICollection).IsSynchronized) {
        lock((dummies as ICollection).SyncRoot) {
          int count = dummies.Count;
          Assert.AreEqual(12345, count); // ;-)
        }
      }
    }

    /// <summary>Tests the RemoveDeadItems() method</summary>
    [Test]
    public void TestRemoveDeadItems() {
      List<WeakReference<Dummy>> dummyReferences = new List<WeakReference<Dummy>>();

      Dummy oneTwoThreeDummy = new Dummy(123);
      dummyReferences.Add(new WeakReference<Dummy>(oneTwoThreeDummy));

      dummyReferences.Add(new WeakReference<Dummy>(null));

      Dummy fourFiveSixDummy = new Dummy(456);
      dummyReferences.Add(new WeakReference<Dummy>(fourFiveSixDummy));

      WeakCollection<Dummy> dummies = new WeakCollection<Dummy>(dummyReferences);

      Assert.AreEqual(3, dummies.Count);

      dummies.RemoveDeadItems();

      Assert.AreEqual(2, dummies.Count);
      Assert.AreSame(oneTwoThreeDummy, dummies[0]);
      Assert.AreSame(fourFiveSixDummy, dummies[1]);
    }

  }

} // namespace Nuclex.Support.Collections

#endif // UNITTEST