refactor: improve MultiStreamBuilder and snapshot handling

finance_app/lib/screens/expenses_screen.dart

@@ -227,31 +227,13 @@ class _ExpensesScreenState extends State<ExpensesScreen> with TickerProviderStat
           _totalExpensesStream,   // Stream<double> for total expenses
         ],
         builder: (context, snapshots) {
-          // Handle loading states for all streams
-          if (snapshots.any((s) => s.connectionState == ConnectionState.waiting && !s.hasData)) {
+          if (snapshots.length < 3) {
             return const Center(child: CircularProgressIndicator());
           }
 
-          // Handle error states for all streams
-          final errorSnapshots = snapshots.where((s) => s.hasError).toList();
-          if (errorSnapshots.isNotEmpty) {
-            return Center(
-              child: Text(
-                'Error loading data:\n${errorSnapshots.map((s) => s.error).join('\n')}',
-                textAlign: TextAlign.center,
-              ),
-            );
-          }
-
-          // Safely extract data with proper type checking
-          try {
-            final combinedData = snapshots.data; // First access the List<dynamic> data
-            if (combinedData == null || combinedData.length < 3) {
-              return const Center(child: Text('Missing data streams'));
-            }
-            final expenseCategories = (combinedData[0] as List<Category>?) ?? [];
-            final totalIncome = (combinedData[1] as double?) ?? 0.0;
-            final totalExpenses = (combinedData[2] as double?) ?? 0.0;
+          final expenseCategories = snapshots[0].data as List<Category>? ?? [];
+          final totalIncome = snapshots[1].data as double? ?? 0.0;
+          final totalExpenses = snapshots[2].data as double? ?? 0.0;
 
           // Main column layout
           return Column(
@@ -590,16 +572,11 @@ class _ExpensesScreenState extends State<ExpensesScreen> with TickerProviderStat
   }
 }
 
-extension on AsyncSnapshot<List<AsyncSnapshot>> {
-  where(Function(dynamic s) param0) {}
-
-  any(bool Function(AsyncSnapshot s) param0) {}
-}
 
 // Helper widget to manage multiple streams for the main body
 class MultiStreamBuilder extends StatelessWidget {
   final List<Stream<dynamic>> streams;
-  final AsyncWidgetBuilder<List<AsyncSnapshot<dynamic>>> builder;
+  final Widget Function(BuildContext, List<AsyncSnapshot<dynamic>>) builder;
 
   const MultiStreamBuilder({
     Key? key,
@@ -609,42 +586,27 @@ class MultiStreamBuilder extends StatelessWidget {
 
   @override
   Widget build(BuildContext context) {
-    return StreamBuilder<List<dynamic>>(
-      stream: StreamZip(streams),
-      builder: (context, snapshot) {
-        // Handle loading state
-        if (snapshot.connectionState == ConnectionState.waiting) {
+    return StreamBuilder<List<AsyncSnapshot<dynamic>>>(
+      stream: _combineStreams(),
+      builder: (context, combinedSnapshot) {
+        if (combinedSnapshot.connectionState == ConnectionState.waiting) {
           return const Center(child: CircularProgressIndicator());
         }
-        
-        // Handle errors
-        if (snapshot.hasError) {
-          return Center(child: Text('Error: ${snapshot.error}'));
+
+        if (combinedSnapshot.hasError) {
+          return Center(child: Text('Error: ${combinedSnapshot.error}'));
         }
 
-        // Ensure we have data
-        if (!snapshot.hasData) {
-          return const Center(child: Text('No data available'));
-        }
-
-        final data = snapshot.data!;
-        if (data.length != streams.length) {
-          return const Center(child: Text('Unexpected data format'));
-        }
-
-        // Create snapshots list
-        final snapshots = streams.asMap().entries.map((entry) {
-          final index = entry.key;
-          return AsyncSnapshot.withData(
-            ConnectionState.done,
-            data[index],
-          );
-        }).toList();
-
-        return builder(context, snapshots);
+        return builder(context, combinedSnapshot.data ?? []);
       },
     );
   }
+
+  Stream<List<AsyncSnapshot<dynamic>>> _combineStreams() {
+    return StreamZip(streams.map((stream) {
+      return stream.map((data) => AsyncSnapshot.withData(ConnectionState.done, data));
+    }));
+  }
 }