Add QR scan to app bar to handle LNURL withdraw requests

closes #78

lib/routes/receive_payment/receive_payment_page.dart

@@ -1,9 +1,14 @@
 import 'package:breez_translations/breez_translations_locales.dart';
 import 'package:flutter/material.dart';
+import 'package:flutter_bloc/flutter_bloc.dart';
+import 'package:flutter_breez_liquid/flutter_breez_liquid.dart';
+import 'package:l_breez/cubit/cubit.dart';
+import 'package:l_breez/routes/qr_scan/qr_scan.dart';
 import 'package:l_breez/routes/receive_payment/lightning/receive_lightning_page.dart';
 import 'package:l_breez/routes/receive_payment/ln_address/receive_lightning_address_page.dart';
 import 'package:l_breez/routes/receive_payment/onchain/bitcoin_address/receive_bitcoin_address_payment_page.dart';
 import 'package:l_breez/widgets/back_button.dart' as back_button;
+import 'package:l_breez/widgets/flushbar.dart';
 
 class ReceivePaymentPage extends StatefulWidget {
   static const routeName = "/receive_payment";
@@ -24,10 +29,29 @@ class _ReceivePaymentPageState extends State<ReceivePaymentPage> {
 
   @override
   Widget build(BuildContext context) {
+    final texts = context.texts();
+    final themeData = Theme.of(context);
+
     return Scaffold(
       appBar: AppBar(
         leading: const back_button.BackButton(),
         title: Text(_getTitle()),
+        actions: widget.initialPageIndex == ReceiveLightningPaymentPage.pageIndex
+            ? [
+                IconButton(
+                  alignment: Alignment.center,
+                  icon: Image(
+                    image: const AssetImage("assets/icons/qr_scan.png"),
+                    color: themeData.iconTheme.color,
+                    fit: BoxFit.contain,
+                    width: 24.0,
+                    height: 24.0,
+                  ),
+                  tooltip: texts.invoice_action_scan_barcode,
+                  onPressed: () => _scanBarcode(),
+                )
+              ]
+            : [],
       ),
       body: Padding(
         padding: const EdgeInsets.symmetric(horizontal: 16.0, vertical: 0.0),
@@ -40,7 +64,7 @@ class _ReceivePaymentPageState extends State<ReceivePaymentPage> {
     final texts = context.texts();
     switch (widget.initialPageIndex) {
       case ReceiveLightningPaymentPage.pageIndex:
-        return texts.invoice_lightning_title;
+        return texts.invoice_title;
       case ReceiveLightningAddressPage.pageIndex:
         return texts.invoice_ln_address_title;
       case ReceiveBitcoinAddressPaymentPage.pageIndex:
@@ -49,4 +73,41 @@ class _ReceivePaymentPageState extends State<ReceivePaymentPage> {
         return texts.invoice_lightning_title;
     }
   }
+
+  void _scanBarcode() {
+    final texts = context.texts();
+
+    Focus.maybeOf(context)?.unfocus();
+    Navigator.pushNamed<String>(context, QRScan.routeName).then((barcode) async {
+      if (barcode == null || barcode.isEmpty) {
+        if (context.mounted) showFlushbar(context, message: texts.payment_info_dialog_error_qrcode);
+        return;
+      }
+
+      await _validateInput(barcode);
+    });
+  }
+
+  Future<void> _validateInput(String barcode) async {
+    final texts = context.texts();
+    final inputCubit = context.read<InputCubit>();
+
+    var errMsg = "";
+    try {
+      final inputType = await inputCubit.parseInput(input: barcode);
+      if (inputType is! InputType_LnUrlWithdraw) {
+        errMsg = texts.payment_info_dialog_error_unsupported_input;
+      }
+      if (mounted) {
+        Navigator.pop(context);
+      }
+      inputCubit.addIncomingInput(barcode, InputSource.qrcodeReader);
+    } catch (error) {
+      var errStr = error.toString();
+      errMsg = errStr.contains("Unrecognized") ? texts.payment_info_dialog_error_unsupported_input : errStr;
+      if (mounted) {
+        showFlushbar(context, message: errMsg);
+      }
+    }
+  }
 }