fix: parse version number with multiple digits

lib/app_version/app_version.dart

@@ -1,5 +1,6 @@
 import 'dart:convert';
 
+import 'package:flutter/foundation.dart';
 import 'package:http/http.dart' as http;
 import 'package:package_info_plus/package_info_plus.dart';
 import 'package:pub_semver/pub_semver.dart' as semver;
@@ -41,13 +42,22 @@ class AppVersion {
       final data = List<Map>.from(json);
       final tag = data.firstWhere((element) => element['prerelease'] == false);
       final tagName = tag['tag_name'] as String;
-      // Strip the leading `v` and anything trailing.
-      // May need to be updated if we starting using postfixes like `beta`.
-      _latest = tagName.substring(1, 6);
+      _latest = parseVersionTag(tagName);
     } else {
       log.w('Issue getting latest version info from GitHub, '
           'status code: ${response.statusCode}\n');
     }
     return _latest;
   }
+
+  /// Returns the version number without the leading `v` or any postfix.
+  ///
+  /// Examples:
+  /// `v1.2.3` becomes `1.2.3`.
+  /// `v1.2.3-beta` becomes `1.2.3`.
+  @visibleForTesting
+  String parseVersionTag(String tag) {
+    final version = tag.split('v').last.split('-').first;
+    return version;
+  }
 }

test/app_version/app_version_test.dart

@@ -0,0 +1,50 @@
+import 'package:mocktail/mocktail.dart';
+import 'package:nyrna/app_version/app_version.dart';
+import 'package:package_info_plus/package_info_plus.dart';
+import 'package:test/test.dart';
+
+class MockPackageInfo extends Mock implements PackageInfo {}
+
+final packageInfo = MockPackageInfo();
+
+AppVersion appVersion = AppVersion(packageInfo);
+
+void main() {
+  setUp(() {
+    appVersion = AppVersion(packageInfo);
+  });
+
+  group('AppVersion:', () {
+    group('parseVersionTag:', () {
+      test('parses versions with 1 digit in each place', () {
+        final version = appVersion.parseVersionTag('v1.2.3');
+        expect(version, '1.2.3');
+      });
+
+      test('parses versions with 2 digits in each place', () {
+        final version = appVersion.parseVersionTag('v12.23.34');
+        expect(version, '12.23.34');
+      });
+
+      test('parses versions with 3 digits in each place', () {
+        final version = appVersion.parseVersionTag('v123.234.345');
+        expect(version, '123.234.345');
+      });
+
+      test('parses versions with 1 digit in each place and a postfix', () {
+        final version = appVersion.parseVersionTag('v1.2.3-beta');
+        expect(version, '1.2.3');
+      });
+
+      test('parses versions with 2 digits in each place and a postfix', () {
+        final version = appVersion.parseVersionTag('v12.23.34-beta');
+        expect(version, '12.23.34');
+      });
+
+      test('parses versions with 3 digits in each place and a postfix', () {
+        final version = appVersion.parseVersionTag('v123.234.345-beta');
+        expect(version, '123.234.345');
+      });
+    });
+  });
+}