feat(boxing): handle multi-code paichan switches

lib/pages/boxing_page.dart

@@ -4,6 +4,7 @@ import 'package:pad_scanner/services/app_config_service.dart';
 import 'package:pad_scanner/services/scanner_service.dart';
 import 'package:pad_scanner/services/code_parser.dart';
 import 'package:pad_scanner/services/api_service.dart';
+import 'package:pad_scanner/services/boxing_context.dart';
 import 'package:pad_scanner/services/feedback_service.dart';
 import 'package:pad_scanner/pages/boxing_detail_page.dart';
 import 'package:pad_scanner/widgets/status_bar.dart';
@@ -101,6 +102,8 @@ class _BoxingPageState extends State<BoxingPage> {
   int? _editingPackedItemId;
   String _editingPackedQuantity = '';
   int? _deletingPackedItemId;
+  String? _lastScannedPaichanNo;
+  String? _paichanSwitchNotice;
 
   // 提交中
   bool _isSubmitting = false;
@@ -184,6 +187,8 @@ class _BoxingPageState extends State<BoxingPage> {
     _editingPackedItemId = null;
     _editingPackedQuantity = '';
     _deletingPackedItemId = null;
+    _lastScannedPaichanNo = null;
+    _paichanSwitchNotice = null;
     _isSubmitting = false;
     _lastBoxNo = null;
     _editingBox = null;
@@ -260,6 +265,9 @@ class _BoxingPageState extends State<BoxingPage> {
       _isDuplicateBoxNo = false;
       _editingBox = null;
       _statusOverrideText = null;
+      if (_mode == BoxingMode.singleCode) {
+        _paichanSwitchNotice = null;
+      }
 
       // 根据模式自动填充
       _applyAutoFill();
@@ -293,9 +301,27 @@ class _BoxingPageState extends State<BoxingPage> {
           }
         });
       case BoxingMode.multiCode:
-        if (_boxNoController.text.trim().isEmpty) {
-          _boxNoController.text = (_maxBoxNo + 1).toString();
+        final decision = decideMultiCodePaichanContext(
+          lastPaichanNo: _lastScannedPaichanNo,
+          currentPaichanNo: _paichanNo,
+          currentBoxNoText: _boxNoController.text,
+          maxBoxNo: _maxBoxNo,
+        );
+        if (decision.isSwitched) {
+          _manyToOnePackedItems.clear();
+          _editingPackedItemId = null;
+          _editingPackedQuantity = '';
+          _deletingPackedItemId = null;
+          _paichanSwitchNotice = '排产号已切换：${_paichanNo ?? "--"}';
+          _feedbackService.trigger(FeedbackEvent.paichanSwitch);
+        } else {
+          _paichanSwitchNotice = null;
         }
+        final boxNoToApply = decision.boxNoToApply;
+        if (boxNoToApply != null) {
+          _boxNoController.text = boxNoToApply.toString();
+        }
+        _lastScannedPaichanNo = _paichanNo;
         _quantityController.text = (_erpQuantity ?? 0).toString();
         _quantityController.selection = TextSelection(
           baseOffset: 0,
@@ -508,6 +534,7 @@ class _BoxingPageState extends State<BoxingPage> {
         }
 
       case BoxingMode.multiCode:
+        _lastScannedPaichanNo = _paichanNo;
         setState(() {
           if (boxItemId != null) {
             _manyToOnePackedItems.add(
@@ -643,6 +670,7 @@ class _BoxingPageState extends State<BoxingPage> {
   void _finishManyToOneBox() {
     final currentBoxNo = int.tryParse(_boxNoController.text.trim());
     setState(() {
+      _manyToOnePackedItems.clear();
       _editingPackedItemId = null;
       _editingPackedQuantity = '';
       _deletingPackedItemId = null;
@@ -913,6 +941,11 @@ class _BoxingPageState extends State<BoxingPage> {
       _statusText = '超出可装数量上限';
       return;
     }
+    if (_paichanSwitchNotice != null) {
+      _statusDot = StatusDotColor.blue;
+      _statusText = '排产号已切换，箱号已重置';
+      return;
+    }
     switch (_phase) {
       case _Phase.waiting:
         _statusDot = StatusDotColor.blue;
@@ -978,6 +1011,16 @@ class _BoxingPageState extends State<BoxingPage> {
       body: Column(
         children: [
           // 重复箱号警告条（保留，因为这是输入区关联的即时反馈）
+          if (_paichanSwitchNotice != null)
+            Container(
+              width: double.infinity,
+              padding: const EdgeInsets.symmetric(vertical: 8, horizontal: 16),
+              color: Colors.blue.shade50,
+              child: Text(
+                _paichanSwitchNotice!,
+                style: TextStyle(color: Colors.blue.shade900, fontSize: 13),
+              ),
+            ),
           if (_isDuplicateBoxNo && _phase == _Phase.scanned)
             Container(
               width: double.infinity,

lib/services/boxing_context.dart

@@ -0,0 +1,38 @@
+enum PaichanContextChange { firstScan, samePaichan, switchedPaichan }
+
+class PaichanContextDecision {
+  final PaichanContextChange change;
+  final int? boxNoToApply;
+
+  const PaichanContextDecision({required this.change, this.boxNoToApply});
+
+  bool get isSwitched => change == PaichanContextChange.switchedPaichan;
+}
+
+PaichanContextDecision decideMultiCodePaichanContext({
+  required String? lastPaichanNo,
+  required String? currentPaichanNo,
+  required String currentBoxNoText,
+  required int maxBoxNo,
+}) {
+  final recommendedBoxNo = maxBoxNo + 1;
+  if (currentPaichanNo == null || currentPaichanNo.isEmpty) {
+    return const PaichanContextDecision(change: PaichanContextChange.firstScan);
+  }
+  if (lastPaichanNo == null || lastPaichanNo.isEmpty) {
+    return PaichanContextDecision(
+      change: PaichanContextChange.firstScan,
+      boxNoToApply: currentBoxNoText.trim().isEmpty ? recommendedBoxNo : null,
+    );
+  }
+  if (lastPaichanNo == currentPaichanNo) {
+    return PaichanContextDecision(
+      change: PaichanContextChange.samePaichan,
+      boxNoToApply: currentBoxNoText.trim().isEmpty ? recommendedBoxNo : null,
+    );
+  }
+  return PaichanContextDecision(
+    change: PaichanContextChange.switchedPaichan,
+    boxNoToApply: recommendedBoxNo,
+  );
+}

lib/services/feedback_service.dart

@@ -11,6 +11,7 @@ enum FeedbackEvent {
   networkError, // Network error         → failure sound + short vibrate
   duplicateBoxNo, // Duplicate box no     → failure sound + short vibrate
   modeSwitch, // Mode toggle           → beep only
+  paichanSwitch, // Paichan changed      → beep + short vibrate
 }
 
 /// Centralized feedback dispatcher.
@@ -56,6 +57,10 @@ class FeedbackService {
 
       case FeedbackEvent.modeSwitch:
         _soundService.playBeep();
+
+      case FeedbackEvent.paichanSwitch:
+        _soundService.playBeep();
+        _vibrateShort();
     }
   }
 

test/services/boxing_context_test.dart

@@ -0,0 +1,60 @@
+import 'package:flutter_test/flutter_test.dart';
+import 'package:pad_scanner/services/boxing_context.dart';
+
+void main() {
+  group('decideMultiCodePaichanContext', () {
+    test('first scan records context and fills recommended box if empty', () {
+      final decision = decideMultiCodePaichanContext(
+        lastPaichanNo: null,
+        currentPaichanNo: 'W00009',
+        currentBoxNoText: '',
+        maxBoxNo: 3,
+      );
+
+      expect(decision.change, PaichanContextChange.firstScan);
+      expect(decision.boxNoToApply, 4);
+      expect(decision.isSwitched, isFalse);
+    });
+
+    test('same paichan keeps current box number', () {
+      final decision = decideMultiCodePaichanContext(
+        lastPaichanNo: 'W00009',
+        currentPaichanNo: 'W00009',
+        currentBoxNoText: '8',
+        maxBoxNo: 3,
+      );
+
+      expect(decision.change, PaichanContextChange.samePaichan);
+      expect(decision.boxNoToApply, isNull);
+      expect(decision.isSwitched, isFalse);
+    });
+
+    test('switched paichan resets to new paichan max box plus one', () {
+      final decision = decideMultiCodePaichanContext(
+        lastPaichanNo: 'W00009',
+        currentPaichanNo: 'W00010',
+        currentBoxNoText: '8',
+        maxBoxNo: 1,
+      );
+
+      expect(decision.change, PaichanContextChange.switchedPaichan);
+      expect(decision.boxNoToApply, 2);
+      expect(decision.isSwitched, isTrue);
+    });
+
+    test(
+      'same paichan defensively fills recommended box when box is empty',
+      () {
+        final decision = decideMultiCodePaichanContext(
+          lastPaichanNo: 'W00009',
+          currentPaichanNo: 'W00009',
+          currentBoxNoText: '',
+          maxBoxNo: 4,
+        );
+
+        expect(decision.change, PaichanContextChange.samePaichan);
+        expect(decision.boxNoToApply, 5);
+      },
+    );
+  });
+}