handle approval in better way

lib/view_models/tenders_view_model.dart

@@ -353,12 +353,58 @@ class TendersViewModel with ChangeNotifier {
     required String status,
   }) async {
     _tenderApprovalErrorMessage = null;
+
+    // Get current approval for this tender
+    final existingApproval = getTenderApprovalForTender(tenderId);
+    final existingApprovalIndex = tenderApprovals.indexWhere(
+      (a) => a.tenderId == tenderId,
+    );
+
+    // Create optimistic approval data
+    TenderApprovalsData? optimisticApproval;
+
+    if (existingApproval == null) {
+      // No existing approval - create new optimistic approval
+      optimisticApproval = TenderApprovalsData(
+        id: null, // Will be filled by server
+        status: status,
+        tenderId: tenderId,
+        companyId: null, // Will be filled by server
+        submissionMode: submissionMode,
+        createdAt: DateTime.now().millisecondsSinceEpoch,
+        tender: null,
+      );
+      tenderApprovals.add(optimisticApproval);
+    } else {
+      // Existing approval - update optimistically
+      if (existingApproval.status == status) {
+        // Same status - remove approval (toggle off)
+        if (existingApprovalIndex != -1) {
+          tenderApprovals.removeAt(existingApprovalIndex);
+        }
+        optimisticApproval = null;
+      } else {
+        // Different status - update to new status
+        optimisticApproval = existingApproval.copyWith(
+          status: status,
+          submissionMode: submissionMode,
+        );
+        if (existingApprovalIndex != -1) {
+          tenderApprovals[existingApprovalIndex] = optimisticApproval;
+        }
+      }
+    }
+
+    // Notify listeners immediately for optimistic update
     notifyListeners();
+
+    // Call API
     final result = await _tendersRepository.toggleApprovals(
       tenderId: tenderId,
       submissionMode: submissionMode,
       status: status,
     );
+
     switch (result) {
       case Ok<TenderApprovalsToggleResponse>():
         _tenderApprovalToggleData = result.value.data;
@@ -382,12 +428,31 @@ class TendersViewModel with ChangeNotifier {
           } else {
             tenderApprovals.add(approvalData);
           }
+        } else {
+          // Server returned null data - remove approval
+          tenderApprovals.removeWhere((a) => a.tenderId == tenderId);
         }
         break;
       case Error<TenderApprovalsToggleResponse>():
+        // Revert optimistic update on error
+        if (existingApproval == null) {
+          // Remove the optimistic approval we added
+          tenderApprovals.removeWhere((a) => a.tenderId == tenderId);
+        } else {
+          // Restore the original approval - find current index and update, or add if not found
+          final currentIndex = tenderApprovals.indexWhere(
+            (a) => a.tenderId == tenderId,
+          );
+          if (currentIndex != -1) {
+            tenderApprovals[currentIndex] = existingApproval;
+          } else {
+            tenderApprovals.add(existingApproval);
+          }
+        }
         _tenderApprovalErrorMessage = result.error.toString();
         break;
     }
+
     notifyListeners();
     _tenderApprovalErrorMessage = null;
     notifyListeners();