Added the HTML fallback Source

README.md

@@ -19,6 +19,8 @@ Currently supported App sources:
 - Third Party F-Droid Repos
   - Any URLs ending with `/fdroid/<word>`, where `<word>` can be anything - most often `repo`
 - [Steam](https://store.steampowered.com/mobile)
+- "HTML" (Fallback)
+  - Any other URL that returns an HTML page with links to APK files (if multiple, the last file alphabetically is picked)
 
 ## Limitations
 - App installs happen asynchronously and the success/failure of an install cannot be determined directly. This results in install statuses and versions sometimes being out of sync with the OS until the next launch or until the problem is manually corrected.

lib/app_sources/html.dart

@@ -0,0 +1,47 @@
+import 'package:easy_localization/easy_localization.dart';
+import 'package:html/parser.dart';
+import 'package:http/http.dart';
+import 'package:obtainium/custom_errors.dart';
+import 'package:obtainium/providers/source_provider.dart';
+
+class HTML extends AppSource {
+  @override
+  String standardizeURL(String url) {
+    return url;
+  }
+
+  @override
+  String? changeLogPageFromStandardUrl(String standardUrl) => null;
+
+  @override
+  Future<APKDetails> getLatestAPKDetails(
+    String standardUrl,
+    Map<String, dynamic> additionalSettings,
+  ) async {
+    var uri = Uri.parse(standardUrl);
+    Response res = await get(uri);
+    if (res.statusCode == 200) {
+      List<String> links = parse(res.body)
+          .querySelectorAll('a')
+          .map((element) => element.attributes['href'] ?? '')
+          .where((element) => element.toLowerCase().endsWith('.apk'))
+          .toList();
+      links.sort((a, b) => a.split('/').last.compareTo(b.split('/').last));
+      if (links.isEmpty) {
+        throw NoReleasesError();
+      }
+      var rel = links.last;
+      var apkName = rel.split('/').last;
+      var version = apkName.substring(0, apkName.length - 4);
+      List<String> apkUrls = [rel]
+          .map((e) => e.toLowerCase().startsWith('http://') ||
+                  e.toLowerCase().startsWith('https://')
+              ? e
+              : '${uri.origin}/$e')
+          .toList();
+      return APKDetails(version, apkUrls, AppNames(uri.host, tr('app')));
+    } else {
+      throw getObtainiumHttpError(res);
+    }
+  }
+}

lib/providers/source_provider.dart

@@ -13,6 +13,7 @@ import 'package:obtainium/app_sources/fdroidrepo.dart';
 import 'package:obtainium/app_sources/github.dart';
 import 'package:obtainium/app_sources/gitlab.dart';
 import 'package:obtainium/app_sources/izzyondroid.dart';
+import 'package:obtainium/app_sources/html.dart';
 import 'package:obtainium/app_sources/mullvad.dart';
 import 'package:obtainium/app_sources/signal.dart';
 import 'package:obtainium/app_sources/sourceforge.dart';
@@ -154,6 +155,10 @@ class App {
 
 // Ensure the input is starts with HTTPS and has no WWW
 preStandardizeUrl(String url) {
+  var firstDotIndex = url.indexOf('.');
+  if (!(firstDotIndex >= 0 && firstDotIndex != url.length - 1)) {
+    throw UnsupportedURLError();
+  }
   if (url.toLowerCase().indexOf('http://') != 0 &&
       url.toLowerCase().indexOf('https://') != 0) {
     url = 'https://$url';
@@ -277,7 +282,8 @@ class SourceProvider {
     SourceForge(),
     APKMirror(),
     FDroidRepo(),
-    SteamMobile()
+    SteamMobile(),
+    HTML() // This should ALWAYS be the last option as they are tried in order
   ];
 
   // Add more mass url source classes here so they are available via the service