update

lib/features/add_transaction/provider.dart

@@ -1,4 +1,5 @@
 import 'package:flutter_riverpod/flutter_riverpod.dart';
+import '../../core/constants.dart';
 import '../../shared/models/transaction.dart';
 
 class AddTransactionState {
@@ -8,6 +9,7 @@ class AddTransactionState {
   final DateTime date;
   final String note;
   final bool isSubmitting;
+  final String? editingId;
 
   const AddTransactionState({
     this.amount,
@@ -16,6 +18,7 @@ class AddTransactionState {
     required this.date,
     this.note = '',
     this.isSubmitting = false,
+    this.editingId,
   });
 
   AddTransactionState copyWith({
@@ -25,6 +28,7 @@ class AddTransactionState {
     DateTime? date,
     String? note,
     bool? isSubmitting,
+    String? editingId,
   }) =>
       AddTransactionState(
         amount: amount ?? this.amount,
@@ -33,7 +37,10 @@ class AddTransactionState {
         date: date ?? this.date,
         note: note ?? this.note,
         isSubmitting: isSubmitting ?? this.isSubmitting,
+        editingId: editingId ?? this.editingId,
       );
+
+  bool get isEditing => editingId != null;
 }
 
 class AddTransactionNotifier extends StateNotifier<AddTransactionState> {
@@ -41,11 +48,32 @@ class AddTransactionNotifier extends StateNotifier<AddTransactionState> {
       : super(AddTransactionState(date: DateTime.now()));
 
   void setAmount(double? v) => state = state.copyWith(amount: v);
+  
   void setCategory(String v) => state = state.copyWith(category: v);
-  void setType(TransactionType v) => state = state.copyWith(type: v);
+  
+  void setType(TransactionType v) {
+    // Reset category to first item of new type
+    final newCategory = AppCategories.forType(v).first;
+    state = state.copyWith(type: v, category: newCategory);
+  }
+  
   void setDate(DateTime v) => state = state.copyWith(date: v);
+  
   void setNote(String v) => state = state.copyWith(note: v);
+  
   void setSubmitting(bool v) => state = state.copyWith(isSubmitting: v);
+  
+  void initializeForEdit(Transaction transaction) {
+    state = AddTransactionState(
+      amount: transaction.amount,
+      category: transaction.category,
+      type: transaction.type,
+      date: transaction.date,
+      note: transaction.note ?? '',
+      editingId: transaction.id,
+    );
+  }
+  
   void reset() => state = AddTransactionState(date: DateTime.now());
 }
 
@@ -53,3 +81,9 @@ final addTransactionProvider =
     StateNotifierProvider.autoDispose<AddTransactionNotifier, AddTransactionState>(
   (ref) => AddTransactionNotifier(),
 );
+
+// Reactive categories based on selected type
+final availableCategoriesProvider = Provider.autoDispose<List<String>>((ref) {
+  final type = ref.watch(addTransactionProvider.select((s) => s.type));
+  return AppCategories.forType(type);
+});

lib/features/add_transaction/screen.dart

@@ -12,7 +12,9 @@ import 'provider.dart';
 const _uuid = Uuid();
 
 class AddTransactionScreen extends ConsumerStatefulWidget {
-  const AddTransactionScreen({super.key});
+  final Transaction? initial;
+  
+  const AddTransactionScreen({super.key, this.initial});
 
   @override
   ConsumerState<AddTransactionScreen> createState() =>
@@ -24,6 +26,18 @@ class _AddTransactionScreenState extends ConsumerState<AddTransactionScreen> {
   final _amountController = TextEditingController();
   final _noteController = TextEditingController();
 
+  @override
+  void initState() {
+    super.initState();
+    if (widget.initial != null) {
+      WidgetsBinding.instance.addPostFrameCallback((_) {
+        ref.read(addTransactionProvider.notifier).initializeForEdit(widget.initial!);
+        _amountController.text = widget.initial!.amount.toString();
+        _noteController.text = widget.initial!.note ?? '';
+      });
+    }
+  }
+
   @override
   void dispose() {
     _amountController.dispose();
@@ -37,7 +51,7 @@ class _AddTransactionScreenState extends ConsumerState<AddTransactionScreen> {
     ref.read(addTransactionProvider.notifier).setSubmitting(true);
 
     final tx = Transaction(
-      id: _uuid.v4(),
+      id: state.editingId ?? _uuid.v4(),
       amount: state.amount!,
       category: state.category,
       type: state.type,
@@ -45,7 +59,12 @@ class _AddTransactionScreenState extends ConsumerState<AddTransactionScreen> {
       note: state.note.isEmpty ? null : state.note,
     );
 
-    await ref.read(transactionsProvider.notifier).add(tx);
+    if (state.isEditing) {
+      await ref.read(transactionsProvider.notifier).update(tx);
+    } else {
+      await ref.read(transactionsProvider.notifier).add(tx);
+    }
+    
     ref.read(addTransactionProvider.notifier).setSubmitting(false);
 
     if (mounted) context.pop();
@@ -76,11 +95,12 @@ class _AddTransactionScreenState extends ConsumerState<AddTransactionScreen> {
   @override
   Widget build(BuildContext context) {
     final state = ref.watch(addTransactionProvider);
+    final categories = ref.watch(availableCategoriesProvider);
 
     return Scaffold(
       backgroundColor: AppColors.background,
       appBar: AppBar(
-        title: const Text('Add Transaction'),
+        title: Text(state.isEditing ? 'Edit Transaction' : 'Add Transaction'),
         leading: IconButton(
           icon: const Icon(Icons.close_rounded),
           onPressed: () => context.pop(),
@@ -139,6 +159,7 @@ class _AddTransactionScreenState extends ConsumerState<AddTransactionScreen> {
               _SectionLabel('Category'),
               const SizedBox(height: 8),
               _CategoryPicker(
+                categories: categories,
                 selected: state.category,
                 onChanged: (c) =>
                     ref.read(addTransactionProvider.notifier).setCategory(c),
@@ -200,7 +221,7 @@ class _AddTransactionScreenState extends ConsumerState<AddTransactionScreen> {
                           color: Colors.white,
                         ),
                       )
-                    : const Text('Save Transaction'),
+                    : Text(state.isEditing ? 'Update Transaction' : 'Save Transaction'),
               ),
             ],
           ),
@@ -309,16 +330,21 @@ class _TypeOption extends StatelessWidget {
 }
 
 class _CategoryPicker extends StatelessWidget {
+  final List<String> categories;
   final String selected;
   final ValueChanged<String> onChanged;
-  const _CategoryPicker({required this.selected, required this.onChanged});
+  const _CategoryPicker({
+    required this.categories,
+    required this.selected,
+    required this.onChanged,
+  });
 
   @override
   Widget build(BuildContext context) {
     return Wrap(
       spacing: 8,
       runSpacing: 8,
-      children: AppCategories.all.map((cat) {
+      children: categories.map((cat) {
         final isSelected = cat == selected;
         final color = AppCategories.colors[cat] ?? AppColors.accent;
         final icon = AppCategories.icons[cat] ?? Icons.category_rounded;