imrpoving tran flow

lib/screens/gateway/gateway_screen.dart

@@ -1,4 +1,7 @@
+import 'dart:io';
+
 import 'package:flutter/material.dart';
+import 'package:flutter_dotenv/flutter_dotenv.dart';
 import 'package:go_router/go_router.dart';
 import 'package:qpay/screens/gateway/gateway_controller.dart';
 import 'package:webview_flutter/webview_flutter.dart';
@@ -15,14 +18,20 @@ class _GatewayScreenState extends State<GatewayScreen> {
   late WebViewController _webViewController;
   late GatewayController controller;
 
+  bool integrationStarted = false;
+
   @override
   void initState() {
     super.initState();
     _initWebView(widget.url);
     controller = GatewayController(context);
-    controller.pollTransaction(
-      controller.transactionController.model.receiptData?['id'],
-    );
+
+    bool simulate = bool.parse(dotenv.env['SIMULATE_PAYMENT_SUCCESS']!);
+    if(simulate) {
+      sleep(Duration(seconds: 10));
+      String url = widget.url.replaceAll("/pay/", "/receipt/");
+      _webViewController.loadRequest(Uri.parse(url));
+    }
   }
 
   void _initWebView(String url) {
@@ -42,6 +51,33 @@ class _GatewayScreenState extends State<GatewayScreen> {
               },
               onHttpError: (HttpResponseError error) {},
               onWebResourceError: (WebResourceError error) {},
+              onUrlChange: (UrlChange url) async {
+                print("URL Changed to ${url.url!}");
+
+                if(url.url!.contains("/checkout/receipt/")){
+                  if(integrationStarted) {
+                    return;
+                  }
+
+                  ScaffoldMessenger.of(context).showSnackBar(
+                    SnackBar(
+                      content: Text("Payment was successful, please wait while we process your order."),
+                      behavior: SnackBarBehavior.floating,
+                      backgroundColor: Colors.black87,
+                      duration: const Duration(seconds: 5),
+                    ),
+                  );
+
+                  setState(() {
+                    integrationStarted = true;
+                  });
+                  await controller.poll(controller.transactionController.model.receiptData?['id']);
+
+                  WidgetsBinding.instance.addPostFrameCallback((_) {
+                    context.go('/integration');
+                  });
+                }
+              }
             ),
           )
           ..loadRequest(Uri.parse(url));