third commit

lib/presentation/payment/screens/payment_screen.dart

@@ -125,7 +125,7 @@ class _PaymentScreenState extends ConsumerState<PaymentScreen> {
           );
         },
       ),
-      bottomNavigationBar: _bottomBar(cart.grandTotal, state, cart.isEmpty),
+      bottomNavigationBar: _bottomBar(controller, state, cart.grandTotal),
     );
   }
 
@@ -557,7 +557,15 @@ class _PaymentScreenState extends ConsumerState<PaymentScreen> {
   }
 
   // ------------------------------------------------------------ Bottom bar
-  Widget _bottomBar(double total, PaymentState state, bool cartEmpty) {
+  Widget _bottomBar(
+    PaymentController controller,
+    PaymentState state,
+    double total,
+  ) {
+    // A cash sale cannot complete until the cashier says what was handed over.
+    final canComplete = controller.canConfirm;
+    final reason = controller.blockedReason;
+
     return SafeArea(
       child: Container(
         padding: const EdgeInsets.fromLTRB(
@@ -599,13 +607,45 @@ class _PaymentScreenState extends ConsumerState<PaymentScreen> {
                   ],
                 ),
               ).animate().shake(duration: 300.ms, hz: 3),
+            if (reason != null && state.error == null)
+              Padding(
+                padding: const EdgeInsets.only(bottom: AppSpacing.sm),
+                child: Row(
+                  children: [
+                    const Icon(Icons.info_outline_rounded,
+                        size: 15, color: AppColors.textTertiary),
+                    const SizedBox(width: AppSpacing.sm),
+                    Expanded(
+                      child: Text(
+                        reason,
+                        style: const TextStyle(
+                          fontSize: 12.5,
+                          color: AppColors.textTertiary,
+                        ),
+                      ),
+                    ),
+                    if (state.activeMethod.needsChange)
+                      TextButton(
+                        onPressed: () => _setCash(controller.balanceDue),
+                        style: TextButton.styleFrom(
+                          minimumSize: const Size(0, 30),
+                          padding: const EdgeInsets.symmetric(
+                            horizontal: AppSpacing.md,
+                          ),
+                        ),
+                        child: const Text('Exact',
+                            style: TextStyle(fontSize: 12.5)),
+                      ),
+                  ],
+                ),
+              ),
             PrimaryButton(
               label: 'Complete Sale',
               icon: Icons.check_circle_outline_rounded,
               large: true,
               tone: ButtonTone.success,
               busy: state.isProcessing,
-              onPressed: cartEmpty ? null : _confirm,
+              onPressed: canComplete ? _confirm : null,
               trailing: Text(
                 Formatters.money(total),
                 style: AppTypography.money(19, color: Colors.white),