first commit

lib/providers/account_provider.dart

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+import 'package:flutter_riverpod/flutter_riverpod.dart';
+
+import '../api/account_api.dart';
+import '../core/network/api_exception.dart';
+import '../models/account.dart';
+
+/// 账户信息（余额 / 总收入 / 总支出）
+class AccountNotifier extends AsyncNotifier<AccountInfo> {
+  @override
+  Future<AccountInfo> build() => ref.watch(accountApiProvider).getAccount();
+
+  /// 把账户余额改成 [targetBalance]。
+  ///
+  /// 后端只能写期初余额，所以这里先反算：
+  /// `initialBalance = targetBalance - totalIncome + totalExpense`
+  Future<void> setBalance(double targetBalance) async {
+    final current = state.value;
+    if (current == null) throw ApiException(-1, '账户信息尚未加载完成');
+
+    final initial = initialBalanceFor(
+      targetBalance: targetBalance,
+      totalIncome: current.totalIncome,
+      totalExpense: current.totalExpense,
+    );
+    final updated = await ref.read(accountApiProvider).updateBalance(initial);
+    state = AsyncData(updated);
+  }
+}
+
+final accountProvider =
+    AsyncNotifierProvider<AccountNotifier, AccountInfo>(AccountNotifier.new);