add infinite scroll to entries

lib/components/pages/legs.dart

@@ -14,6 +14,10 @@ class LegsPage extends StatefulWidget {
 }
 
 class _LegsPageState extends State<LegsPage> {
+  static const int _pageSize = 100;
+  static const double _loadMoreTriggerExtent = 400;
+  static double _persistedScrollOffset = 0;
+
   int _sortDirection = 0;
   DateTime? _startDate;
   DateTime? _endDate;
@@ -23,6 +27,18 @@ class _LegsPageState extends State<LegsPage> {
   bool _loadingNetworks = false;
   List<String> _availableNetworks = [];
   List<String> _selectedNetworks = [];
+  String? _lastQuerySignature;
+  late final ScrollController _scrollController;
+  bool _showBackToTop = false;
+  bool _isAutoLoadingMore = false;
+
+  @override
+  void initState() {
+    super.initState();
+    _scrollController = ScrollController(
+      initialScrollOffset: _persistedScrollOffset,
+    )..addListener(_onScroll);
+  }
 
   @override
   void didChangeDependencies() {
@@ -34,6 +50,49 @@ class _LegsPageState extends State<LegsPage> {
     }
   }
 
+  @override
+  void dispose() {
+    _persistedScrollOffset =
+        _scrollController.hasClients ? _scrollController.offset : 0;
+    _scrollController.removeListener(_onScroll);
+    _scrollController.dispose();
+    super.dispose();
+  }
+
+  void _onScroll() {
+    if (!_scrollController.hasClients) return;
+    _persistedScrollOffset = _scrollController.offset;
+    final shouldShow = _scrollController.offset > 500;
+    if (shouldShow != _showBackToTop) {
+      setState(() => _showBackToTop = shouldShow);
+    }
+    _maybeAutoLoadMore();
+  }
+
+  Future<void> _maybeAutoLoadMore() async {
+    if (!mounted || !_scrollController.hasClients || _isAutoLoadingMore) return;
+    final position = _scrollController.position;
+    if (position.extentAfter > _loadMoreTriggerExtent) return;
+    final data = context.read<DataService>();
+    if (data.isLegsLoading || !data.legsHasMore) return;
+
+    _isAutoLoadingMore = true;
+    try {
+      await _loadMore();
+    } finally {
+      _isAutoLoadingMore = false;
+    }
+  }
+
+  Future<void> _scrollToTop() async {
+    if (!_scrollController.hasClients) return;
+    await _scrollController.animateTo(
+      0,
+      duration: const Duration(milliseconds: 250),
+      curve: Curves.easeOutCubic,
+    );
+  }
+
   Future<void> _loadNetworks() async {
     setState(() => _loadingNetworks = true);
     final data = context.read<DataService>();
@@ -47,7 +106,16 @@ class _LegsPageState extends State<LegsPage> {
 
   Future<void> _refreshLegs() async {
     final data = context.read<DataService>();
+    final signature = _legsQuerySignature();
+    final queryChanged =
+        _lastQuerySignature != null && signature != _lastQuerySignature;
+    _lastQuerySignature = signature;
+
+    final currentCount = data.legs.length;
+    final shouldPreserveLoadedCount = !queryChanged && currentCount > _pageSize;
+    final limit = shouldPreserveLoadedCount ? currentCount : _pageSize;
     await data.fetchLegs(
+      limit: limit,
       sortDirection: _sortDirection,
       dateRangeStart: _formatDate(_startDate),
       dateRangeEnd: _formatDate(_endDate),
@@ -58,17 +126,30 @@ class _LegsPageState extends State<LegsPage> {
 
   Future<void> _loadMore() async {
     final data = context.read<DataService>();
+    final offset = data.legs.length;
     await data.fetchLegs(
       sortDirection: _sortDirection,
       dateRangeStart: _formatDate(_startDate),
       dateRangeEnd: _formatDate(_endDate),
-      offset: data.legs.length,
+      offset: offset,
+      limit: _pageSize,
       append: true,
       unallocatedOnly: _unallocatedOnly,
       networkFilter: _selectedNetworks,
     );
   }
 
+  String _legsQuerySignature() {
+    final networks = [..._selectedNetworks]..sort();
+    return [
+      'sort=$_sortDirection',
+      'start=${_formatDate(_startDate) ?? ''}',
+      'end=${_formatDate(_endDate) ?? ''}',
+      'unallocated=$_unallocatedOnly',
+      'networks=${networks.join(',')}',
+    ].join(';');
+  }
+
   double _pageMileage(List legs) {
     return legs.fold<double>(
       0,
@@ -120,12 +201,15 @@ class _LegsPageState extends State<LegsPage> {
     final legs = data.legs;
     final pageMileage = _pageMileage(legs);
 
-    return RefreshIndicator(
+    return Stack(
-      onRefresh: _refreshLegs,
+      children: [
-      child: ListView(
+        RefreshIndicator(
-        padding: const EdgeInsets.all(16),
+          onRefresh: _refreshLegs,
-        physics: const AlwaysScrollableScrollPhysics(),
+          child: ListView(
-        children: [
+            controller: _scrollController,
+            padding: const EdgeInsets.all(16),
+            physics: const AlwaysScrollableScrollPhysics(),
+            children: [
           Row(
             mainAxisAlignment: MainAxisAlignment.spaceBetween,
             children: [
@@ -298,28 +382,62 @@ class _LegsPageState extends State<LegsPage> {
               children: [
                 ..._buildLegsWithDividers(context, legs, distanceUnits),
                 const SizedBox(height: 8),
-                if (data.legsHasMore || data.isLegsLoading)
+                if (data.isLegsLoading)
-                  Align(
+                  const Align(
                     alignment: Alignment.center,
-                    child: OutlinedButton.icon(
+                    child: Padding(
-                      onPressed:
+                      padding: EdgeInsets.symmetric(vertical: 12),
-                          data.isLegsLoading ? null : () => _loadMore(),
+                      child: SizedBox(
-                      icon: data.isLegsLoading
+                        height: 18,
-                          ? const SizedBox(
+                        width: 18,
-                              height: 14,
+                        child: CircularProgressIndicator(strokeWidth: 2),
-                              width: 14,
-                              child: CircularProgressIndicator(strokeWidth: 2),
-                            )
-                          : const Icon(Icons.expand_more),
-                      label: Text(
-                        data.isLegsLoading ? 'Loading...' : 'Load more',
                       ),
                     ),
                   ),
+                if (data.legsHasMore && !data.isLegsLoading)
+                  Padding(
+                    padding: const EdgeInsets.symmetric(vertical: 12),
+                    child: Row(
+                      mainAxisAlignment: MainAxisAlignment.center,
+                      children: [
+                        const SizedBox(
+                          height: 18,
+                          width: 18,
+                          child: CircularProgressIndicator(strokeWidth: 2),
+                        ),
+                        const SizedBox(width: 10),
+                        Text(
+                          'Loading',
+                          style: Theme.of(context).textTheme.bodySmall,
+                        ),
+                      ],
+                    ),
+                  ),
               ],
             ),
-        ],
+            ],
-      ),
+          ),
+        ),
+        Positioned(
+          right: 16,
+          bottom: 16,
+          child: AnimatedSlide(
+            offset: _showBackToTop ? Offset.zero : const Offset(0, 1.2),
+            duration: const Duration(milliseconds: 180),
+            curve: Curves.easeOut,
+            child: AnimatedOpacity(
+              opacity: _showBackToTop ? 1 : 0,
+              duration: const Duration(milliseconds: 180),
+              child: FloatingActionButton.small(
+                heroTag: 'legsBackToTop',
+                tooltip: 'Back to top',
+                onPressed: _scrollToTop,
+                child: const Icon(Icons.arrow_upward),
+              ),
+            ),
+          ),
+        ),
+      ],
     );
   }
 

lib/services/data_service/data_service_core.dart

@@ -18,6 +18,26 @@ class _LegFetchOptions {
     this.unallocatedOnly = false,
     this.networkFilter = const [],
   });
+
+  _LegFetchOptions copyWith({
+    int? limit,
+    String? sortBy,
+    int? sortDirection,
+    String? dateRangeStart,
+    String? dateRangeEnd,
+    bool? unallocatedOnly,
+    List<String>? networkFilter,
+  }) {
+    return _LegFetchOptions(
+      limit: limit ?? this.limit,
+      sortBy: sortBy ?? this.sortBy,
+      sortDirection: sortDirection ?? this.sortDirection,
+      dateRangeStart: dateRangeStart ?? this.dateRangeStart,
+      dateRangeEnd: dateRangeEnd ?? this.dateRangeEnd,
+      unallocatedOnly: unallocatedOnly ?? this.unallocatedOnly,
+      networkFilter: networkFilter ?? this.networkFilter,
+    );
+  }
 }
 
 class DataService extends ChangeNotifier {
@@ -397,11 +417,11 @@ class DataService extends ChangeNotifier {
     List<String> networkFilter = const [],
   }) async {
     _isLegsLoading = true;
+    final normalizedNetworks = networkFilter
+        .map((network) => network.trim())
+        .where((network) => network.isNotEmpty)
+        .toList();
     if (!append) {
-      final normalizedNetworks = networkFilter
-          .map((network) => network.trim())
-          .where((network) => network.isNotEmpty)
-          .toList();
       _lastLegsFetch = _LegFetchOptions(
         limit: limit,
         sortBy: sortBy,
@@ -437,6 +457,17 @@ class DataService extends ChangeNotifier {
       if (json is List) {
         final newLegs = json.map((e) => Leg.fromJson(e)).toList();
         _legs = append ? [..._legs, ...newLegs] : newLegs;
+        if (append) {
+          _lastLegsFetch = _lastLegsFetch.copyWith(
+            limit: _legs.length,
+            sortBy: sortBy,
+            sortDirection: sortDirection,
+            dateRangeStart: dateRangeStart,
+            dateRangeEnd: dateRangeEnd,
+            unallocatedOnly: unallocatedOnly,
+            networkFilter: normalizedNetworks,
+          );
+        }
         // Keep "load more" available as long as the server returns items; hide only on empty.
         _legsHasMore = newLegs.isNotEmpty;
       } else {