new: controller command of newStack(int length) to allow for expansion and deletion of card stack data

lib/src/controller/card_swiper_controller.dart

@@ -15,16 +15,36 @@ class CardSwiperController {
     _eventController.add(ControllerSwipeEvent(direction));
   }
 
-  // Undo the last swipe
+  /// Undo the last swipe
   void undo() {
     _eventController.add(const ControllerUndoEvent());
   }
 
-  // Change the top card to a specific index.
+  /// Change the top card to a specific index.
   void moveTo(int index) {
     _eventController.add(ControllerMoveEvent(index));
   }
 
+  /// We have a new list of card data for this state machine to handle
+  /// 1. Set the length of the card list
+  /// 2. Move index to 0 (restart stack to first card)
+  void newStack(int length) {
+    _eventController.add(ControllerNewStackEvent(length));
+  }
+
+  /// We have a new added cards to the end
+  /// 0. Keep internal index the same (undo will work, can go backwards)
+  /// 1. Set the internal length of the card list
+  /// 2. Check if we need to redraw, if we are at end of card list
+  // void appendStack(int length) {
+  //   _eventController.add(ControllerNewStackEvent(length));
+  // }
+
+  /// Set the length only, user can moveTo(0), or other actions
+  // void modifiedStack(int length) {
+  //   _eventController.add(ControllerNewStackEvent(length));
+  // }
+
   Future<void> dispose() async {
     await _eventController.close();
   }

lib/src/controller/controller_event.dart

@@ -17,3 +17,8 @@ class ControllerMoveEvent extends ControllerEvent {
   final int index;
   const ControllerMoveEvent(this.index);
 }
+
+class ControllerNewStackEvent extends ControllerEvent {
+  final int length;
+  const ControllerNewStackEvent(this.length);
+}

lib/src/widget/card_swiper_state.dart

@@ -22,10 +22,20 @@ class _CardSwiperState<T extends Widget> extends State<CardSwiper>
 
   StreamSubscription<ControllerEvent>? controllerSubscription;
 
+  late NullableCardBuilder _cardBuilder;
+  late int _cardsCount;
+
   @override
   void initState() {
     super.initState();
 
+    debugPrint('[WTF] _CardSwiperState.initState !!!');
+    debugPrint('[WTF] _CardSwiperState.initState !!!');
+    debugPrint('[WTF] _CardSwiperState.initState !!!');
+
+    _cardBuilder = widget.cardBuilder;
+    _cardsCount  = widget.cardsCount;
+
     _undoableIndex.state = widget.initialIndex;
 
     controllerSubscription =
@@ -67,6 +77,11 @@ class _CardSwiperState<T extends Widget> extends State<CardSwiper>
 
   @override
   void dispose() {
+
+    debugPrint('[WTF] _CardSwiperState.dispose !!!');
+    debugPrint('[WTF] _CardSwiperState.dispose !!!');
+    debugPrint('[WTF] _CardSwiperState.dispose !!!');
+
     _animationController.dispose();
     controllerSubscription?.cancel();
     super.dispose();
@@ -104,7 +119,7 @@ class _CardSwiperState<T extends Widget> extends State<CardSwiper>
           angle: _cardAnimation.angle,
           child: ConstrainedBox(
             constraints: constraints,
-            child: widget.cardBuilder(
+            child: _cardBuilder(
               context,
               _currentIndex!,
               (100 * _cardAnimation.left / widget.threshold).ceil(),
@@ -155,7 +170,7 @@ class _CardSwiperState<T extends Widget> extends State<CardSwiper>
         scale: _cardAnimation.scale - ((1 - widget.scale) * (index - 1)),
         child: ConstrainedBox(
           constraints: constraints,
-          child: widget.cardBuilder(context, getValidIndexOffset(index)!, 0, 0),
+          child: _cardBuilder(context, getValidIndexOffset(index)!, 0, 0),
         ),
       ),
     );
@@ -166,6 +181,8 @@ class _CardSwiperState<T extends Widget> extends State<CardSwiper>
       ControllerSwipeEvent(:final direction) => _swipe(direction),
       ControllerUndoEvent() => _undo(),
       ControllerMoveEvent(:final index) => _moveTo(index),
+      // controller 
+      ControllerNewStackEvent(:final length) => _newCardStack(length)
     };
   }
 
@@ -189,7 +206,7 @@ class _CardSwiperState<T extends Widget> extends State<CardSwiper>
   }
 
   Future<void> _handleCompleteSwipe() async {
-    final isLastCard = _currentIndex! == widget.cardsCount - 1;
+    final isLastCard = _currentIndex! == _cardsCount - 1;
     final shouldCancelSwipe = await widget.onSwipe
             ?.call(_currentIndex!, _nextIndex, _detectedDirection) ==
         false;
@@ -286,14 +303,20 @@ class _CardSwiperState<T extends Widget> extends State<CardSwiper>
   }
 
   void _moveTo(int index) {
+    debugPrint('[WTF]  _moveTo()  index: $index  currentIndex: $_currentIndex  cardsCount: $_cardsCount');
     if (index == _currentIndex) return;
-    if (index < 0 || index >= widget.cardsCount) return;
+    if (index < 0 || index >= _cardsCount) return;
 
     setState(() {
       _undoableIndex.state = index;
     });
   }
 
+  void _newCardStack(int length) {
+    _cardsCount  = length;
+    _moveTo(0);  // move to first card, and force redraw if necessary
+  }
+
   int numberOfCardsOnScreen() {
     if (widget.isLoop) {
       return widget.numberOfCardsDisplayed;
@@ -304,7 +327,7 @@ class _CardSwiperState<T extends Widget> extends State<CardSwiper>
 
     return math.min(
       widget.numberOfCardsDisplayed,
-      widget.cardsCount - _currentIndex!,
+      _cardsCount - _currentIndex!,
     );
   }
 
@@ -314,9 +337,9 @@ class _CardSwiperState<T extends Widget> extends State<CardSwiper>
     }
 
     final index = _currentIndex! + offset;
-    if (!widget.isLoop && !index.isBetween(0, widget.cardsCount - 1)) {
+    if (!widget.isLoop && !index.isBetween(0, _cardsCount - 1)) {
       return null;
     }
-    return index % widget.cardsCount;
+    return index % _cardsCount;
   }
 }