Add ObserveClear, ObserveReverse, ObserverSort

src/ObservableCollections.R3/ObservableCollectionR3Extensions.cs

@@ -40,11 +40,26 @@ public static class ObservableCollectionR3Extensions
         return new ObservableCollectionMove<T>(source, cancellationToken);
     }
 
-    public static Observable<Unit> ObserveReset<T>(this IObservableCollection<T> source, CancellationToken cancellationToken = default)
+    public static Observable<SortOperation<T>> ObserveReset<T>(this IObservableCollection<T> source, CancellationToken cancellationToken = default)
     {
         return new ObservableCollectionReset<T>(source, cancellationToken);
     }
 
+    public static Observable<Unit> ObserveClear<T>(this IObservableCollection<T> source, CancellationToken cancellationToken = default)
+    {
+        return new ObservableCollectionClear<T>(source, cancellationToken);
+    }
+
+    public static Observable<Unit> ObserveReverse<T>(this IObservableCollection<T> source, CancellationToken cancellationToken = default)
+    {
+        return new ObservableCollectionReverse<T>(source, cancellationToken);
+    }
+
+    public static Observable<(int Index, int Count, IComparer<T> Comparer)> ObserveSort<T>(this IObservableCollection<T> source, CancellationToken cancellationToken = default)
+    {
+        return new ObservableCollectionSort<T>(source, cancellationToken);
+    }
+
     public static Observable<int> ObserveCountChanged<T>(this IObservableCollection<T> source, bool notifyCurrentCount = false, CancellationToken cancellationToken = default)
     {
         return new ObservableCollectionCountChanged<T>(source, notifyCurrentCount, cancellationToken);
@@ -188,16 +203,39 @@ sealed class ObservableCollectionMove<T>(IObservableCollection<T> collection, Ca
         }
     }
 }
-
 sealed class ObservableCollectionReset<T>(IObservableCollection<T> collection, CancellationToken cancellationToken)
-    : Observable<Unit>
+    : Observable<SortOperation<T>>
 {
-    protected override IDisposable SubscribeCore(Observer<Unit> observer)
+    protected override IDisposable SubscribeCore(Observer<SortOperation<T>> observer)
     {
         return new _ObservableCollectionReset(collection, observer, cancellationToken);
     }
 
     sealed class _ObservableCollectionReset(
+        IObservableCollection<T> collection,
+        Observer<SortOperation<T>> observer,
+        CancellationToken cancellationToken)
+        : ObservableCollectionObserverBase<T, SortOperation<T>>(collection, observer, cancellationToken)
+    {
+        protected override void Handler(in NotifyCollectionChangedEventArgs<T> eventArgs)
+        {
+            if (eventArgs.Action == NotifyCollectionChangedAction.Reset)
+            {
+                observer.OnNext(eventArgs.SortOperation);
+            }
+        }
+    }
+}
+
+sealed class ObservableCollectionClear<T>(IObservableCollection<T> collection, CancellationToken cancellationToken)
+    : Observable<Unit>
+{
+    protected override IDisposable SubscribeCore(Observer<Unit> observer)
+    {
+        return new _ObservableCollectionClear(collection, observer, cancellationToken);
+    }
+
+    sealed class _ObservableCollectionClear(
         IObservableCollection<T> collection,
         Observer<Unit> observer,
         CancellationToken cancellationToken)
@@ -205,7 +243,7 @@ sealed class ObservableCollectionReset<T>(IObservableCollection<T> collection, C
     {
         protected override void Handler(in NotifyCollectionChangedEventArgs<T> eventArgs)
         {
-            if (eventArgs.Action == NotifyCollectionChangedAction.Reset)
+            if (eventArgs.Action == NotifyCollectionChangedAction.Reset && eventArgs.SortOperation.IsNull)
             {
                 observer.OnNext(Unit.Default);
             }
@@ -213,6 +251,52 @@ sealed class ObservableCollectionReset<T>(IObservableCollection<T> collection, C
     }
 }
 
+sealed class ObservableCollectionReverse<T>(IObservableCollection<T> collection, CancellationToken cancellationToken) : Observable<Unit>
+{
+    protected override IDisposable SubscribeCore(Observer<Unit> observer)
+    {
+        return new _ObservableCollectionReverse(collection, observer, cancellationToken);
+    }
+
+    sealed class _ObservableCollectionReverse(
+        IObservableCollection<T> collection,
+        Observer<Unit> observer,
+        CancellationToken cancellationToken)
+        : ObservableCollectionObserverBase<T, Unit>(collection, observer, cancellationToken)
+    {
+        protected override void Handler(in NotifyCollectionChangedEventArgs<T> eventArgs)
+        {
+            if (eventArgs.Action == NotifyCollectionChangedAction.Reset && eventArgs.SortOperation.IsReverse)
+            {
+                observer.OnNext(Unit.Default);
+            }
+        }
+    }
+}
+
+sealed class ObservableCollectionSort<T>(IObservableCollection<T> collection, CancellationToken cancellationToken) : Observable<(int Index, int Count, IComparer<T> Comparer)>
+{
+    protected override IDisposable SubscribeCore(Observer<(int Index, int Count, IComparer<T> Comparer)> observer)
+    {
+        return new _ObservableCollectionSort(collection, observer, cancellationToken);
+    }
+
+    sealed class _ObservableCollectionSort(
+        IObservableCollection<T> collection,
+        Observer<(int Index, int Count, IComparer<T> Comparer)> observer,
+        CancellationToken cancellationToken)
+        : ObservableCollectionObserverBase<T, (int Index, int Count, IComparer<T> Comparer)>(collection, observer, cancellationToken)
+    {
+        protected override void Handler(in NotifyCollectionChangedEventArgs<T> eventArgs)
+        {
+            if (eventArgs.Action == NotifyCollectionChangedAction.Reset && eventArgs.SortOperation.IsSort)
+            {
+                observer.OnNext(eventArgs.SortOperation.AsTuple());
+            }
+        }
+    }
+}
+
 sealed class ObservableCollectionCountChanged<T>(IObservableCollection<T> collection, bool notifyCurrentCount, CancellationToken cancellationToken)
     : Observable<int>
 {

src/ObservableCollections/NotifyCollectionChangedEventArgs.cs

@@ -2,6 +2,7 @@
 using System.Collections;
 using System.Collections.Generic;
 using System.Collections.Specialized;
+using System.Diagnostics.CodeAnalysis;
 using System.Runtime.InteropServices;
 
 namespace ObservableCollections
@@ -16,6 +17,9 @@ namespace ObservableCollections
         public bool IsReverse => Comparer == ReverseSentinel.Instance;
         public bool IsNull => Comparer == null;
 
+        [MemberNotNullWhen(true, nameof(Comparer))]
+        public bool IsSort => !IsNull && !IsReverse;
+
         public SortOperation(int index, int count, IComparer<T>? comparer)
         {
             Index = index;
@@ -23,6 +27,11 @@ namespace ObservableCollections
             Comparer = comparer ?? NullComparerSentinel.Instance;
         }
 
+        public (int Index, int Count, IComparer<T> Comparer) AsTuple()
+        {
+            return (Index, Count, Comparer!);
+        }
+
         public static SortOperation<T> CreateReverse(int index, int count)
         {
             return new SortOperation<T>(index, count, ReverseSentinel.Instance);

tests/ObservableCollections.Tests/ObservableListTest.cs

@@ -157,7 +157,7 @@ namespace ObservableCollections.Tests
         //    list.AddRange(new[] { 10, 21, 30, 44 });
 
         //    var filter1 = new TestFilter<int>((x, v) => x % 2 == 0);
-        //    view1.AttachFilter(filter1);
+        //    view1.AttachFilter((x, v) => x % 2 == 0));
 
         //    filter1.CalledOnCollectionChanged[0].Action.Should().Be(NotifyCollectionChangedAction.Add);
         //    filter1.CalledOnCollectionChanged[0].NewValue.Should().Be(10);