From 253ed1b9d941c8f1e9e387787ff306ef49776bc3 Mon Sep 17 00:00:00 2001
From: Yoh Deadfall <yoh.deadfall@hotmail.com>
Date: Wed, 5 Jun 2024 23:30:19 +0300
Subject: [PATCH] Fixed OrderBy for collection changes

---
 src/Kinetic/Linq/ObservableView.OrderBy.cs | 28 ++++++++++++++++------
 test/Kinetic.Tests/ObservableViewTests.cs  |  6 ++---
 2 files changed, 24 insertions(+), 10 deletions(-)

diff --git a/src/Kinetic/Linq/ObservableView.OrderBy.cs b/src/Kinetic/Linq/ObservableView.OrderBy.cs
index 6893642..979e433 100644
--- a/src/Kinetic/Linq/ObservableView.OrderBy.cs
+++ b/src/Kinetic/Linq/ObservableView.OrderBy.cs
@@ -317,14 +317,28 @@ public void OnNext(ValueTuple<TItem> value)
             {
                 Debug.Assert(typeof(TItem) == typeof(DynamicItem));
 
-                var item = value.Item1;
-                // Old index search is based on reference equality,
-                // while the new index is key comparison based.
+                ref var item = ref value.Item1;
+                // The index search uses two separate BinarySearch calls
+                // to exclude the current item which already has a new key.
                 var oldIndex = _items.IndexOf(item);
-                var newIndex = _items.BinarySearch(item, _keyComparer.ItemComparer);
+                var newIndex = oldIndex;
 
-                if (newIndex < 0)
-                    newIndex = ~newIndex;
+                if (oldIndex > 0)
+                {
+                    newIndex = _items.BinarySearch(index: 0, count: oldIndex, item, _keyComparer.ItemComparer);
+
+                    if (newIndex < 0)
+                        newIndex = ~newIndex;
+                }
+
+                if (newIndex == oldIndex &&
+                    newIndex < _items.Count - 1)
+                {
+                    newIndex = _items.BinarySearch(newIndex + 1, _items.Count - newIndex - 1, item, _keyComparer.ItemComparer);
+
+                    if (newIndex < 0)
+                        newIndex = ~newIndex;
+                }
 
                 if (oldIndex != newIndex)
                 {
@@ -375,7 +389,7 @@ private int UpdateIndexes(int oldIndex, int newIndex)
                 {
                     foreach (ref var current in indexes)
                     {
-                        if (current > newIndex && current < oldIndex)
+                        if (current >= newIndex && current < oldIndex)
                             current += 1;
                     }
 
diff --git a/test/Kinetic.Tests/ObservableViewTests.cs b/test/Kinetic.Tests/ObservableViewTests.cs
index 577a692..a642387 100644
--- a/test/Kinetic.Tests/ObservableViewTests.cs
+++ b/test/Kinetic.Tests/ObservableViewTests.cs
@@ -79,10 +79,10 @@ public void OrderByDynamic()
         Assert.Equal(new[] { itemA, itemB, itemC, itemD }, view);
 
         itemA.Number.Set(5);
-        itemB.Number.Set(4);
+        itemC.Number.Set(0);
 
         Assert.Equal(new[] { itemA, itemC, itemD, itemB }, list);
-        Assert.Equal(new[] { itemC, itemD, itemB, itemA }, view);
+        Assert.Equal(new[] { itemC, itemB, itemD, itemA }, view);
 
         list.Remove(itemA);
         list.Remove(itemD);
@@ -111,7 +111,7 @@ public void OrderByDynamic()
         list.Add(itemB);
 
         Assert.Equal(new[] { itemA, itemC, itemD, itemB }, list);
-        Assert.Equal(new[] { itemC, itemD, itemB, itemA }, view);
+        Assert.Equal(new[] { itemC, itemB, itemD, itemA }, view);
     }
 
     [Fact]