fix: improve transfer recognition and local data safety

frontend/lib/shared/services/guest_merge_service.dart

@@ -1,3 +1,6 @@
+import 'dart:convert';
+
+import 'package:crypto/crypto.dart';
 import 'package:miaoji_zhang/shared/api/api_client.dart';
 import 'package:miaoji_zhang/shared/services/current_ledger_store.dart';
 import 'package:miaoji_zhang/shared/services/shanghai_time.dart';
@@ -17,12 +20,23 @@ class GuestMergeService {
 
   static final _dio = ApiClient.instance.dio;
 
-  static Future<GuestMergeResult> merge(Map<String, dynamic> snapshot) async {
-    final ledgerResponse = await _dio.post(
-      '/api/ledgers',
-      data: {'name': '游客数据', 'iconKey': 'wallet'},
-    );
-    final ledgerId = (ledgerResponse.data['id'] as num).toInt();
+  static Future<GuestMergeResult> merge(
+    Map<String, dynamic> snapshot, {
+    String ledgerName = '游客数据',
+  }) async {
+    final ledgersResponse = await _dio.get('/api/ledgers');
+    final existingLedger = (ledgersResponse.data as List<dynamic>)
+        .cast<Map<String, dynamic>>()
+        .where((item) => item['name'] == ledgerName)
+        .firstOrNull;
+    final ledgerId = existingLedger == null
+        ? ((await _dio.post(
+                    '/api/ledgers',
+                    data: {'name': ledgerName, 'iconKey': 'wallet'},
+                  )).data['id']
+                  as num)
+              .toInt()
+        : (existingLedger['id'] as num).toInt();
     final categoryMap = <int, int>{};
     final available = <Map<String, dynamic>>[];
     for (final type in ['expense', 'income']) {
@@ -37,6 +51,7 @@ class GuestMergeService {
 
     for (final value in snapshot['categories'] as List<dynamic>? ?? const []) {
       final category = value as Map<String, dynamic>;
+      if (category['isDeleted'] == true) continue;
       final existing = available.where(
         (item) =>
             item['type'] == category['type'] &&
@@ -45,6 +60,8 @@ class GuestMergeService {
       Map<String, dynamic> remote;
       if (existing.isNotEmpty) {
         remote = existing.first;
+      } else if (category['isCustom'] == false) {
+        continue;
       } else {
         final response = await _dio.post(
           '/api/categories',
@@ -66,14 +83,15 @@ class GuestMergeService {
       final oldId = (transaction['categoryId'] as num).toInt();
       final custom = categoryMap[oldId];
       if (custom != null) return custom;
+      final categoryType = _transactionCategoryType(transaction);
       final exact = available.where(
         (item) =>
-            item['type'] == transaction['type'] &&
+            item['type'] == categoryType &&
             item['name'] == transaction['categoryName'],
       );
       if (exact.isNotEmpty) return (exact.first['id'] as num).toInt();
       final fallback = available.firstWhere(
-        (item) => item['type'] == transaction['type'] && item['name'] == '其他',
+        (item) => item['type'] == categoryType && item['name'] == '其他',
       );
       return (fallback['id'] as num).toInt();
     }
@@ -82,6 +100,7 @@ class GuestMergeService {
     for (final value
         in snapshot['transactions'] as List<dynamic>? ?? const []) {
       final transaction = value as Map<String, dynamic>;
+      if (transaction['isDeleted'] == true) continue;
       await _dio.post(
         '/api/transactions',
         data: {
@@ -91,9 +110,12 @@ class GuestMergeService {
           'amount': transaction['amount'],
           'note': transaction['note'],
           'paymentMethod': transaction['paymentMethod'],
+          'transferDirection': transaction['transferDirection'],
+          'counterparty': transaction['counterparty'],
           'occurredAt': transaction['occurredAt'],
           'source': 'manual',
           'sourceText': null,
+          'clientRequestId': _importRequestId(transaction),
         },
       );
       transactionCount++;
@@ -136,14 +158,42 @@ class GuestMergeService {
   ) {
     final transaction = (snapshot['transactions'] as List<dynamic>? ?? const [])
         .cast<Map<String, dynamic>>()
-        .where((item) => item['categoryId'] == oldCategoryId)
+        .where(
+          (item) =>
+              item['categoryId'] == oldCategoryId && item['isDeleted'] != true,
+        )
         .firstOrNull;
     if (transaction == null) return null;
     final match = available.where(
       (item) =>
-          item['type'] == transaction['type'] &&
+          item['type'] == _transactionCategoryType(transaction) &&
           item['name'] == transaction['categoryName'],
     );
     return match.isEmpty ? null : (match.first['id'] as num).toInt();
   }
+
+  static String _transactionCategoryType(Map<String, dynamic> transaction) {
+    if (transaction['type'] != 'transfer') {
+      return transaction['type'] as String;
+    }
+    return transaction['transferDirection'] == 'in' ? 'income' : 'expense';
+  }
+
+  static String _importRequestId(Map<String, dynamic> transaction) {
+    final existing = transaction['clientRequestId']?.toString().trim();
+    if (existing != null && existing.isNotEmpty && existing.length <= 64) {
+      return existing;
+    }
+    final identity = jsonEncode([
+      transaction['id'],
+      transaction['ledgerId'],
+      transaction['categoryId'],
+      transaction['type'],
+      transaction['transferDirection'],
+      transaction['amount'],
+      transaction['occurredAt'],
+      transaction['note'],
+    ]);
+    return 'local-import-${sha256.convert(utf8.encode(identity)).toString().substring(0, 48)}';
+  }
 }