velocity-pay-flutter/lib/screens/gateway/gateway_web_screen.dart

import 'dart:js_interop';

import 'package:flutter/material.dart';
import 'package:flutter_dotenv/flutter_dotenv.dart';
import 'package:go_router/go_router.dart';
import 'package:qpay/interop.dart';
import 'package:qpay/models/responsive_policy.dart';
import 'package:qpay/screens/gateway/gateway_controller.dart';
import 'package:webview_flutter/webview_flutter.dart';
import 'package:web/web.dart' as web;

class GatewayWebScreen extends StatefulWidget {
  const GatewayWebScreen({super.key});

  @override
  State<GatewayWebScreen> createState() => _GatewayWebScreenState();
}

class _GatewayWebScreenState extends State<GatewayWebScreen> {
  late WebViewController _webViewController;
  late GatewayController controller;
  late String url;
  String? sessionID;

  bool integrationStarted = false;

  @override
  void initState() {
    super.initState();
    controller = GatewayController(context);

    url = controller.transactionController.model.receiptData?['targetUrl'];
  }

  // A function to set up the ResizeObserver
  void setupAttachmentObserver(web.Element element) {
    final observer = web.ResizeObserver(
      (JSArray entries, JSAny observer) {
        // The element has been laid out (and thus attached to the DOM)
        onElementAttached(element);

        // Disconnect the observer once the action is done
        (observer as web.ResizeObserver).disconnect();
      }.toJS,
    );

    observer.observe(element);
  }

  // Called after `element` is attached to the DOM.
  void onElementAttached(web.Element element) {
    // Your code to execute after the element is in the DOM goes here.
    print('Element with ID ${element.id} is attached to the DOM.');
    // You can now safely query the DOM or call JavaScript functions that rely
    // on the element being present.

    Future.delayed(const Duration(milliseconds: 50), () {
      initIframeView();
    });
  }

  void initIframeView() async {
    final uri = Uri.parse(url);
    // 2. The pathSegments property returns a list of the parts of the path.
    // For "checkout/pay/SESSION...", the segments are ["checkout", "pay", "SESSION..."].
    final pathSegments = uri.pathSegments;
    // 3. Check if there are any segments and return the last one,
    // which is the session ID in this URL structure.
    if (pathSegments.isNotEmpty) {
      sessionID = pathSegments.last;

      configure(sessionID!);
    }
    showEmbeddedPage();

    Future.delayed(const Duration(seconds: 10), () async {
      web.HTMLIFrameElement element = fetchIframeFromDom(
        "hc-comms-layer-iframe",
      )!;
      print(element);
      element.onload = (JSAny event) {
        // This is called every time a new page loads in the iframe
        print(event);

        try {
          final newLocation = element.contentWindow?.location.href;
          print('Iframe navigated to: $newLocation');
          // Perform actions based on the new URL

          _navigateWhenDone(newLocation!);
        } catch (e) {
          // Handle potential (though unlikely for same-origin) security errors
          print('Could not access iframe location: $e');
        }
      }.toJS;

      bool simulate = bool.parse(dotenv.env['SIMULATE_PAYMENT_SUCCESS']!);
      if (simulate) {
        await Future.delayed(Duration(milliseconds: 100));
        _navigateWhenDone("/checkout/receipt/");
      }
    });
  }

  web.HTMLIFrameElement? fetchIframeFromDom(String id) {
    final element = web.window.document.querySelector('#$id');
    if (element is web.HTMLIFrameElement) {
      print('Found iframe in DOM: ${element.id}');
      print(element.toString());
      return element;
    }

    print('Could not find iframe with id: $id in the DOM.');
    return null;
  }

  void _navigateWhenDone(String url) {
    if (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: 10),
        ),
      );

      setState(() {
        integrationStarted = true;
      });

      WidgetsBinding.instance.addPostFrameCallback((_) {
        context.go('/poll');
      });
    }
  }

  @override
  void dispose() {
    controller.dispose();
    super.dispose();
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: const Text('Complete your payment'),
        leading: context.canPop()
            ? IconButton(
                onPressed: () {
                  context.pop();
                },
                icon: const Icon(Icons.arrow_back),
              )
            : SizedBox.shrink(),
      ),
      body: ListenableBuilder(
        listenable: controller,
        builder: (context, child) {
          return LayoutBuilder(
            builder: (context, constraints) {
              return SingleChildScrollView(
                child: Center(
                  child: SizedBox(
                    width: ResponsivePolicy.md.toDouble(),
                    child: Padding(
                      padding: const EdgeInsets.all(20.0),
                      child: Column(
                        crossAxisAlignment: CrossAxisAlignment.center,
                        children: [
                          Container(
                            decoration: BoxDecoration(
                              border: Border.all(
                                color: Colors.black87.withAlpha(20),
                              ),
                              borderRadius: BorderRadius.circular(12),
                            ),
                            padding: EdgeInsets.symmetric(
                              vertical: 10,
                              horizontal: 20,
                            ),
                            child: Row(
                              crossAxisAlignment:
                                  CrossAxisAlignment.center,
                              mainAxisAlignment:
                                  MainAxisAlignment.spaceBetween,
                              children: [
                                Text(
                                  'Once done on this page, check transaction status',
                                  style: TextStyle(fontSize: 16),
                                ),
                                InkWell(
                                  onTap: () {
                                    context.push('/poll');
                                  },
                                  borderRadius: BorderRadius.circular(12),
                                  child: Container(
                                    padding: EdgeInsets.symmetric(
                                      horizontal: 12,
                                      vertical: 6,
                                    ),
                                    decoration: BoxDecoration(
                                      color: Theme.of(context)
                                          .colorScheme
                                          .primary
                                          .withValues(alpha: 0.15),
                                      borderRadius: BorderRadius.circular(
                                        12,
                                      ),
                                    ),
                                    child: Text(
                                      'Check status',
                                      style: TextStyle(fontSize: 12),
                                    ),
                                  ),
                                ),
                              ],
                            ),
                          ),
                          SizedBox(height: 10,),
                          SizedBox(
                            width: double.infinity,
                            height: constraints.maxHeight + 300,
                            child: HtmlElementView.fromTagName(
                              tagName: 'div',
                              onElementCreated: (element) {
                                final divElement =
                                    element as web.HTMLDivElement;
                                divElement.id = "embed-target";
                                setupAttachmentObserver(element);
                              },
                            ),
                          ),
                        ],
                      ),
                    ),
                  ),
                ),
              );
            },
          );
        },
      ),
    );
  }
}