third commit

lib/presentation/payment/providers/payment_controller.dart

@@ -74,11 +74,31 @@ class PaymentController extends StateNotifier<PaymentState> {
     return diff > 0 ? diff.asMoney : 0;
   }
 
+  /// Whether Complete Sale should be enabled.
+  ///
+  /// Cash is the strict case: the drawer cannot be reconciled and no change can
+  /// be calculated unless the cashier states what was handed over. Card, UPI
+  /// and wallet settle on the external terminal, so they need no amount here.
   bool get canConfirm {
+    if (_billTotal <= 0) return false;
+
+    // Staged splits already cover the bill.
+    if (balanceDue <= 0.01) return true;
+
     if (state.activeMethod.needsChange) {
-      return state.cashTendered >= balanceDue && balanceDue > 0;
+      return state.cashTendered >= balanceDue;
     }
-    return balanceDue > 0;
+    return true;
+  }
+
+  /// Why the button is disabled, for display next to it.
+  String? get blockedReason {
+    if (_billTotal <= 0) return 'Add at least one item before charging.';
+    if (canConfirm) return null;
+    if (state.activeMethod.needsChange) {
+      return 'Enter the cash received, or tap Exact.';
+    }
+    return null;
   }
 
   void selectMethod(PaymentMethod method) {
@@ -156,10 +176,10 @@ class PaymentController extends StateNotifier<PaymentState> {
 
       state = state.copyWith(isProcessing: false, result: result);
 
-      // Fire and forget — printing must never block the next sale.
-      final receipts = _ref.read(receiptServiceProvider);
-      unawaited(receipts.printDirect(result.transaction));
-      unawaited(receipts.openCashDrawer());
+      // No auto-print: with no roll printer attached this silently failed and
+      // looked like a bug. The receipt screen shows the bill on the terminal
+      // and offers Print, WhatsApp and Share explicitly.
+      unawaited(_ref.read(receiptServiceProvider).openCashDrawer());
       unawaited(_ref.read(soundServiceProvider).saleComplete());
 
       // Stock changed, so the grid must refresh; the new order changes the