Re-added APKMirror as a Track-Only source

lib/app_sources/apkmirror.dart

@@ -0,0 +1,55 @@
+import 'package:html/parser.dart';
+import 'package:http/http.dart';
+import 'package:obtainium/custom_errors.dart';
+import 'package:obtainium/providers/source_provider.dart';
+
+class APKMirror extends AppSource {
+  APKMirror() {
+    host = 'apkmirror.com';
+    enforceTrackOnly = true;
+  }
+
+  @override
+  String standardizeURL(String url) {
+    RegExp standardUrlRegEx = RegExp('^https?://$host/apk/[^/]+/[^/]+');
+    RegExpMatch? match = standardUrlRegEx.firstMatch(url.toLowerCase());
+    if (match == null) {
+      throw InvalidURLError(runtimeType.toString());
+    }
+    return url.substring(0, match.end);
+  }
+
+  @override
+  String? changeLogPageFromStandardUrl(String standardUrl) =>
+      '$standardUrl/#whatsnew';
+
+  @override
+  Future<APKDetails> getLatestAPKDetails(
+      String standardUrl, List<String> additionalData) async {
+    Response res = await get(Uri.parse('$standardUrl/feed'));
+    if (res.statusCode == 200) {
+      String? titleString = parse(res.body)
+          .querySelector('item')
+          ?.querySelector('title')
+          ?.innerHtml;
+      String? version = titleString
+          ?.substring(0,
+              RegExp(' build ( |[0-9])+').firstMatch(titleString)?.start ?? 0)
+          .split(' ')
+          .last;
+      if (version == null) {
+        throw NoVersionError();
+      }
+      return APKDetails(version, []);
+    } else {
+      throw NoReleasesError();
+    }
+  }
+
+  @override
+  AppNames getAppNames(String standardUrl) {
+    String temp = standardUrl.substring(standardUrl.indexOf('://') + 3);
+    List<String> names = temp.substring(temp.indexOf('/') + 1).split('/');
+    return AppNames(names[1], names[2]);
+  }
+}