correct Delete operation behavior

Core/FileOperation.cs

@@ -89,7 +89,7 @@ namespace BallanceTASEditor.Core.FileOperation {
             removedItems.Clear();
             oldPointer = mPointer;
             oldPointerIndex = mPointerIndex;
-            removeStartNode = absoluteRange.start == 1 ? null : mMem.FastGetNode(mPointer, mPointerIndex, absoluteRange.start - 1);
+            removeStartNode = absoluteRange.start == 0 ? null : mMem.FastGetNode(mPointer, mPointerIndex, absoluteRange.start - 1);
 
             // find proper pointer after remove first. but we do not apply it in there.
             // if state is true, it mean the deleted content is placed before pointer previously. we should consider pointer data and we should correct them.
@@ -100,25 +100,25 @@ namespace BallanceTASEditor.Core.FileOperation {
                 // otherwise we only need to minus index with the length of removed content.
                 if (absoluteRange.Within(mPointerIndex)) {
                     // this contains 3 situation
-                    // if full delete, mPointer is null and mPointerIndex is invalid(with wrong data: 0)
+                    // if full delete, mPointer is null and mPointerIndex is invalid(with wrong data: -1)
                     // if delete from head, mPointer and mPointerIndex all are valid. but it is the tail of removed content
                     // otherwise, just find the head of removed content and shift to it.
-                    if (absoluteRange.start == 1 && absoluteRange.end == mMem.Count) {
+                    if (absoluteRange.start == 0 && absoluteRange.end == mMem.Count - 1) {
                         // fully remove
                         newPointer = null;
-                        newPointerIndex = 0;
+                        newPointerIndex = -1;
-                    } else if (absoluteRange.start == 1) {
+                    } else if (absoluteRange.start == 0) {
                         // remove from head
-                        newPointerIndex = absoluteRange.end + 1;
+                        newPointerIndex = 0;
-                        newPointer = mMem.FastGetNode(mPointer, mPointerIndex, newPointerIndex);
+                        newPointer = mMem.FastGetNode(mPointer, mPointerIndex, absoluteRange.end + 1);
                     } else {
                         // simple remove
                         newPointerIndex = absoluteRange.start - 1;
-                        newPointer = mMem.FastGetNode(mPointer, mPointerIndex, newPointerIndex);
+                        newPointer = mMem.FastGetNode(mPointer, mPointerIndex, absoluteRange.start - 1);
                     }
                 } else {
                     newPointer = mPointer;
-                    newPointerIndex = mPointerIndex - absoluteRange.GetCount() + 1;
+                    newPointerIndex = mPointerIndex - absoluteRange.GetCount();
                 }
             } else {
                 // not affected situation
@@ -128,8 +128,8 @@ namespace BallanceTASEditor.Core.FileOperation {
 
             // the real remove operation
             foreach (var item in mMem.IterateWithSelectionRange(absoluteRange, mPointer, mPointerIndex)) {
-                removedItems.AddLast(item); // backups node first;
                 mMem.Remove(item);
+                removedItems.AddLast(item); // backups node;
             }
 
             // apply gotten new pointer
@@ -140,10 +140,12 @@ namespace BallanceTASEditor.Core.FileOperation {
 
         public override void Undo(ref LinkedList<FrameData> mMem, ref LinkedListNode<FrameData> mPointer, ref long mPointerIndex) {
             base.Undo(ref mMem, ref mPointer, ref mPointerIndex);
-            if (mPointer == null) return;
+            // may recovered from empty list
+            //if (mPointer == null) return;
 
             // re-insert data
             foreach (var item in removedItems.IterateFullReversed()) {
+                removedItems.Remove(item);
                 if (removeStartNode == null) {
                     // insert at first
                     mMem.AddFirst(item);
@@ -395,11 +397,13 @@ namespace BallanceTASEditor.Core.FileOperation {
                 // if we use overwrite mode, we need re-add lost data
                 if (isOverwritten) {
                     if (isInsertBefore) {
-                        foreach (var item in data.IterateFull()) {
+                        foreach (var item in oldItems.IterateFull()) {
+                            oldItems.Remove(item);
                             mMem.AddBefore(addStartNode, item);
                         }
                     } else {
-                        foreach (var item in data.IterateFullReversed()) {
+                        foreach (var item in oldItems.IterateFullReversed()) {
+                            oldItems.Remove(item);
                             mMem.AddAfter(addStartNode, item);
                         }
                     }

Core/Util.cs

@@ -33,21 +33,27 @@ namespace BallanceTASEditor.Core {
         //    for (int i = 0; i < count; i++) list.RemoveAt(index);
         //}
 
+        // remove safety. because it store the next node.
         public static IEnumerable<LinkedListNode<FrameData>> IterateFullReversed(this LinkedList<FrameData> ls) {
             var pos = ls.Last;
+            LinkedListNode<FrameData> cacheNextNode;
 
             while (pos != null) {
+                cacheNextNode = pos.Previous;
                 yield return pos;
-                pos = pos.Previous;
+                pos = cacheNextNode;
             }
         }
 
+        // remove safety. because it store the next node.
         public static IEnumerable<LinkedListNode<FrameData>> IterateFull(this LinkedList<FrameData> ls) {
             var pos = ls.First;
+            LinkedListNode<FrameData> cacheNextNode;
             
             while(pos != null) {
+                cacheNextNode = pos.Next;
                 yield return pos;
-                pos = pos.Next;
+                pos = cacheNextNode;
             }
         }
 

UI/TASViewer.cs

@@ -191,13 +191,23 @@ namespace BallanceTASEditor.UI {
                 case OperationEnum.DeleteAfter:
                 case OperationEnum.DeleteBefore: {
                         var pos = mSelectionHelp.GetPoint();
-                        pos += oper == OperationEnum.DeleteBefore ? -1 : 1;
+                        if (oper == OperationEnum.DeleteBefore) pos -= 1;   // delete after mean delete current selected item
-                        if (pos < 0 || pos > mFile.mFrameCount) return;
+                        if (pos < 0 || pos >= mFile.mFrameCount) return;
-                        mFile.Remove(new SelectionRange(pos, pos));
 
                         // only delete before need shift selection
+                        // delete before couldn't cause empty list, so we just need to directly shift
                         if (oper == OperationEnum.DeleteBefore)
                             mSelectionHelp.ShiftTo(false);
+                        // also, if we use delete after and delete the tail of item list, we also need to shift pos(use `else if` to prevent double shift)
+                        else if (oper == OperationEnum.DeleteAfter && pos == mFile.mFrameCount) {
+                            // but delete after may cause empty list error(delete the item within only 1 item list)
+                            // so we need prevent this situation
+                            if (mFile.mFrameCount == 1) mSelectionHelp.Reset(); //yes, reset selection to prevent error
+                            else mSelectionHelp.ShiftTo(false); //no, shift selection.
+                        }
+
+                        // do real operation
+                        mFile.Remove(new SelectionRange(pos, pos));
                         
                         updateSliderRange();
                         RefreshDisplay();