feat: Better support deep links with unsupported URLs (#4007)

* Better support for external links

* Change the import we use

packages/smooth_app/lib/pages/navigator/app_navigator.dart

@@ -85,6 +85,9 @@ class AppNavigator extends InheritedWidget {
 ///
 /// All our routes are prefixed with an underscore, as the [redirect] method
 /// is also called with non prefixed paths for deep links.
+///
+/// One drawback of the implementation is that we never know the base URL of the
+/// deep link (eg: es.openfoodfacts.org)
 class _SmoothGoRouter {
   _SmoothGoRouter({
     List<NavigatorObserver>? observers,
@@ -165,9 +168,9 @@ class _SmoothGoRouter {
               },
             ),
             GoRoute(
-              path: '${_InternalAppRoutes.EXTERNAL_PAGE}/:path',
+              path: _InternalAppRoutes.EXTERNAL_PAGE.path,
               builder: (BuildContext context, GoRouterState state) {
-                return ExternalPage(path: state.pathParameters['path']!);
+                return ExternalPage(path: state.queryParameters['path']!);
               },
             ),
           ],
@@ -202,16 +205,11 @@ class _SmoothGoRouter {
               } else {
                 return AppRoutes.PRODUCT_LOADER(barcode);
               }
+            } else {
+              return _openExternalLink(path);
             }
           } else if (path != _InternalAppRoutes.HOME_PAGE.path) {
-            AnalyticsHelper.trackEvent(
-              AnalyticsEvent.genericDeepLink,
-            );
-
-            // Unsupported link -> open the browser
-            return AppRoutes.EXTERNAL(
-              path[0] == '/' ? path.substring(1) : path,
-            );
+            return _openExternalLink(path);
           }
         }
 
@@ -223,6 +221,17 @@ class _SmoothGoRouter {
     );
   }
 
+  String _openExternalLink(String path) {
+    AnalyticsHelper.trackEvent(
+      AnalyticsEvent.genericDeepLink,
+    );
+
+    // Unsupported link -> open the browser
+    return AppRoutes.EXTERNAL(
+      path[0] == '/' ? path.substring(1) : path,
+    );
+  }
+
   late GoRouter router;
 
   // Indicates whether [_initAppLanguage] was already called
@@ -342,5 +351,5 @@ class AppRoutes {
 
   // Open an external link (where path is relative to the OFF website)
   static String EXTERNAL(String path) =>
-      '/${_InternalAppRoutes.EXTERNAL_PAGE}/$path';
+      '/${_InternalAppRoutes.EXTERNAL_PAGE}/?path=$path';
 }

packages/smooth_app/lib/pages/navigator/external_page.dart

@@ -1,10 +1,18 @@
 import 'package:flutter/material.dart';
+import 'package:http/http.dart' as http;
+import 'package:openfoodfacts/openfoodfacts.dart';
 import 'package:path/path.dart' as path;
 import 'package:smooth_app/helpers/launch_url_helper.dart';
 import 'package:smooth_app/pages/navigator/app_navigator.dart';
+import 'package:smooth_app/query/product_query.dart';
 
+/// This screen is only used for deep links!
+///
 /// A screen opening a [path] relative to the OFF website.
-/// Eg: if path is "contact", it will open 'https://world.openfoodfacts.org/contact'
+///
+/// Unfortunately the deep link we receive doesn't contain the base URL
+/// (eg: de.openfoodfacts.org), that's why we try to guess it with the country
+/// and the locale of the user
 class ExternalPage extends StatefulWidget {
   const ExternalPage({required this.path, Key? key})
       : assert(path != ''),
@@ -22,10 +30,34 @@ class _ExternalPageState extends State<ExternalPage> {
     super.initState();
 
     WidgetsBinding.instance.addPostFrameCallback((_) async {
-      await LaunchUrlHelper.launchURL(
-        path.join('https://world.openfoodfacts.org', widget.path),
-        false,
-      );
+      // First let's try with https://{country}.openfoodfacts.org
+      final OpenFoodFactsCountry? country = ProductQuery.getCountry();
+
+      String? url;
+      if (country != null) {
+        url = path.join(
+          'https://${country.offTag}.openfoodfacts.org',
+          widget.path,
+        );
+
+        if (await _testUrl(url)) {
+          url = null;
+        }
+      }
+
+      // If that's not OK, let's try with world.openfoodfacts.org?lc={language}
+      if (url == null) {
+        final OpenFoodFactsLanguage language = ProductQuery.getLanguage();
+
+        url = path.join(
+          'https://world.openfoodfacts.org',
+          widget.path,
+        );
+
+        url = '$url?lc=${language.offTag}';
+      }
+
+      await LaunchUrlHelper.launchURL(url, false);
 
       if (mounted) {
         AppNavigator.of(context).pop();
@@ -37,4 +69,11 @@ class _ExternalPageState extends State<ExternalPage> {
   Widget build(BuildContext context) {
     return const Scaffold();
   }
+
+  /// Check if an URL exist
+  Future<bool> _testUrl(String url) {
+    return http
+        .head(Uri.parse(url))
+        .then((http.Response value) => value.statusCode != 404);
+  }
 }