User Tagging Linkifier (#38)

Author: HSCOGT

lib/linkify.dart

@@ -1,8 +1,11 @@
 import 'package:linkify/src/email.dart';
 import 'package:linkify/src/url.dart';
+import 'package:linkify/src/user_tag.dart';
 
 export 'package:linkify/src/email.dart' show EmailLinkifier, EmailElement;
 export 'package:linkify/src/url.dart' show UrlLinkifier, UrlElement;
+export 'package:linkify/src/user_tag.dart'
+    show UserTagLinkifier, UserTagElement;
 
 abstract class LinkifyElement {
   final String text;

lib/src/user_tag.dart

@@ -0,0 +1,67 @@
+import 'package:linkify/linkify.dart';
+
+/// For details on how this RegEx works, go to this link.
+/// https://regex101.com/r/QN046t/1
+final _userTagRegex = RegExp(
+  r'^(.*?)(?<![\w@])@([\w@]+(?:[.!][\w@]+)*)',
+  caseSensitive: false,
+  dotAll: true,
+);
+
+class UserTagLinkifier extends Linkifier {
+  const UserTagLinkifier();
+
+  @override
+  List<LinkifyElement> parse(elements, options) {
+    final list = <LinkifyElement>[];
+
+    elements.forEach((element) {
+      if (element is TextElement) {
+        final match = _userTagRegex.firstMatch(element.text);
+
+        if (match == null) {
+          list.add(element);
+        } else {
+          final text = element.text.replaceFirst(match.group(0)!, '');
+
+          if (match.group(1)?.isNotEmpty == true) {
+            list.add(TextElement(match.group(1)!));
+          }
+
+          if (match.group(2)?.isNotEmpty == true) {
+            list.add(UserTagElement('@${match.group(2)!}'));
+          }
+
+          if (text.isNotEmpty) {
+            list.addAll(parse([TextElement(text)], options));
+          }
+        }
+      } else {
+        list.add(element);
+      }
+    });
+
+    return list;
+  }
+}
+
+/// Represents an element containing an user tag
+class UserTagElement extends LinkableElement {
+  final String userTag;
+
+  UserTagElement(this.userTag) : super(userTag, userTag);
+
+  @override
+  String toString() {
+    return "UserTagElement: '$userTag' ($text)";
+  }
+
+  @override
+  bool operator ==(other) => equals(other);
+
+  @override
+  bool equals(other) =>
+      other is UserTagElement &&
+      super.equals(other) &&
+      other.userTag == userTag;
+}

pubspec.yaml

@@ -1,5 +1,5 @@
 name: linkify
-description: Low-level link (text, URLs, emails) parsing library in Dart.
+description: Low-level link (text, URLs, emails, user tagging) parsing library in Dart.
 version: 4.0.0
 homepage: https://github.com/Cretezy/linkify
 

test/linkify_test.dart

@@ -212,4 +212,24 @@ void main() {
       ],
     );
   });
+
+  test('Parses user tag', () {
+    expectListEqual(
+      linkify("@example"),
+      [UserTagElement("@example")],
+    );
+  });
+
+  test('Parses email, link, and user tag', () {
+    expectListEqual(
+      linkify("[email protected] at https://google.com @example"),
+      [
+        EmailElement("[email protected]"),
+        TextElement(" at "),
+        UrlElement("https://google.com", "google.com"),
+        TextElement(" "),
+        UserTagElement("@example")
+      ],
+    );
+  });
 }