Add bidirectional refresh physics

lib/widgets/common/bidirectional_refresh.dart

@@ -0,0 +1,176 @@
+import 'package:flutter/material.dart';
+
+enum _RefreshEdge { top, bottom }
+
+class BidirectionalRefresh extends StatefulWidget {
+  static const double defaultTriggerDistance = 90;
+
+  final Widget child;
+  final Future<void> Function() onRefresh;
+  final double triggerDistance;
+
+  const BidirectionalRefresh({
+    super.key,
+    required this.child,
+    required this.onRefresh,
+    this.triggerDistance = defaultTriggerDistance,
+  });
+
+  @override
+  State<BidirectionalRefresh> createState() => _BidirectionalRefreshState();
+}
+
+class _BidirectionalRefreshState extends State<BidirectionalRefresh> {
+  double _topPullDistance = 0;
+  double _bottomPullDistance = 0;
+  bool _isRefreshing = false;
+
+  bool _handleScrollNotification(ScrollNotification notification) {
+    if (_isRefreshing) {
+      return false;
+    }
+
+    if (notification is ScrollStartNotification) {
+      _resetPullDistance();
+      return false;
+    }
+
+    if (notification is OverscrollNotification) {
+      final metrics = notification.metrics;
+      final isAtTop = metrics.extentBefore == 0;
+      final isAtBottom = metrics.extentAfter == 0;
+
+      if (!isAtTop && !isAtBottom) {
+        return false;
+      }
+
+      var shouldRefresh = false;
+      setState(() {
+        if (isAtTop) {
+          _topPullDistance += notification.overscroll.abs();
+          shouldRefresh = _topPullDistance >= widget.triggerDistance;
+        }
+        if (isAtBottom) {
+          _bottomPullDistance += notification.overscroll.abs();
+          shouldRefresh =
+              shouldRefresh || _bottomPullDistance >= widget.triggerDistance;
+        }
+      });
+      if (shouldRefresh) {
+        _runRefresh();
+      }
+      return false;
+    }
+
+    if (notification is ScrollEndNotification) {
+      _resetPullDistance();
+    }
+
+    return false;
+  }
+
+  Future<void> _runRefresh() async {
+    if (_isRefreshing) {
+      return;
+    }
+
+    setState(() {
+      _isRefreshing = true;
+    });
+
+    try {
+      await widget.onRefresh();
+    } finally {
+      if (!mounted) {
+        return;
+      }
+      setState(() {
+        _isRefreshing = false;
+        _topPullDistance = 0;
+        _bottomPullDistance = 0;
+      });
+    }
+  }
+
+  void _resetPullDistance() {
+    if (_topPullDistance == 0 && _bottomPullDistance == 0) {
+      return;
+    }
+
+    setState(() {
+      _topPullDistance = 0;
+      _bottomPullDistance = 0;
+    });
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    final topProgress = (_topPullDistance / widget.triggerDistance).clamp(
+      0.0,
+      1.0,
+    );
+    final bottomProgress = (_bottomPullDistance / widget.triggerDistance).clamp(
+      0.0,
+      1.0,
+    );
+
+    return NotificationListener<ScrollNotification>(
+      onNotification: _handleScrollNotification,
+      child: Stack(
+        children: [
+          widget.child,
+          _RefreshIndicatorOverlay(
+            alignment: Alignment.topCenter,
+            progress: _isRefreshing ? 1 : topProgress,
+            visible: _isRefreshing || _topPullDistance > 0,
+            edge: _RefreshEdge.top,
+          ),
+          _RefreshIndicatorOverlay(
+            alignment: Alignment.bottomCenter,
+            progress: _isRefreshing ? 1 : bottomProgress,
+            visible: _isRefreshing || _bottomPullDistance > 0,
+            edge: _RefreshEdge.bottom,
+          ),
+        ],
+      ),
+    );
+  }
+}
+
+class _RefreshIndicatorOverlay extends StatelessWidget {
+  final Alignment alignment;
+  final double progress;
+  final bool visible;
+  final _RefreshEdge edge;
+
+  const _RefreshIndicatorOverlay({
+    required this.alignment,
+    required this.progress,
+    required this.visible,
+    required this.edge,
+  });
+
+  @override
+  Widget build(BuildContext context) {
+    if (!visible) {
+      return const SizedBox.shrink();
+    }
+
+    final indicator = RefreshProgressIndicator(value: progress);
+    final padding = edge == _RefreshEdge.top
+        ? const EdgeInsets.only(top: 12)
+        : const EdgeInsets.only(bottom: 12);
+
+    return Positioned.fill(
+      child: IgnorePointer(
+        child: Align(
+          alignment: alignment,
+          child: Padding(
+            padding: padding,
+            child: SizedBox.square(dimension: 28, child: indicator),
+          ),
+        ),
+      ),
+    );
+  }
+}