internal_link: Recognize channel operator in narrow links

Fixes: #632

Author: Khader-1

lib/model/internal_link.dart

@@ -159,6 +159,7 @@ Narrow? _interpretNarrowSegments(List<String> segments, PerAccountStore store) {
     final operand = segments[i + 1];
     switch (operator) {
       case _NarrowOperator.stream:
+      case _NarrowOperator.channel:
         if (streamElement != null) return null;
         final streamId = _parseStreamOperand(operand, store);
         if (streamId == null) return null;
@@ -207,6 +208,7 @@ enum _NarrowOperator {
   near,
   pmWith,
   stream,
+  channel,
   subject,
   topic,
   unknown;

lib/model/internal_link.g.dart

@@ -36,12 +36,19 @@ void main() {
     assert(streams != null || users != null);
     for (final testCase in testCases) {
       final String urlString = testCase.$1;
-      final Narrow? expected = testCase.$2;
-      test(urlString, () async {
-        final store = await setupStore(realmUrl: realmUrl, streams: streams, users: users);
-        final url = store.tryResolveUrl(urlString)!;
-        check(parseInternalLink(url, store)).equals(expected);
-      });
+      // This is here to avoid duplicating each test case that contains `#narrow/stream` or `#narrow/channel`
+      final urlWithChannelSyntax = urlString.replaceFirst('#narrow/stream', '#narrow/channel');
+      final urlWithStreamSyntax = urlString.replaceFirst('#narrow/channel', '#narrow/stream');
+      // Using Set instead of List in `{urlWithStreamSyntax, urlWithChannelSyntax}` to avoid any duplicated
+      // test urls. Specifically, when url is targeting `pm-with/..` or `dm/..`
+      for (final urlString in {urlWithStreamSyntax, urlWithChannelSyntax}) {
+        final Narrow? expected = testCase.$2;
+        test(urlString, () async {
+          final store = await setupStore(realmUrl: realmUrl, streams: streams, users: users);
+          final url = store.tryResolveUrl(urlString)!;
+          check(parseInternalLink(url, store)).equals(expected);
+        });
+      }
     }
   }
 
@@ -52,13 +59,21 @@ void main() {
     final testCases = [
       (true, 'legacy: stream name, no ID',
         '#narrow/stream/check', realmUrl),
+      (true, 'legacy: channel name, no ID',
+        '#narrow/channel/check', realmUrl),
       (true, 'legacy: stream name, no ID, topic',
         '#narrow/stream/check/topic/topic1', realmUrl),
+      (true, 'legacy: channel name, no ID, topic',
+        '#narrow/channel/check/topic/topic1', realmUrl),
 
       (true, 'with numeric stream ID',
         '#narrow/stream/123-check', realmUrl),
+      (true, 'with numeric channel ID',
+        '#narrow/channel/123-check', realmUrl),
       (true, 'with numeric stream ID and topic',
         '#narrow/stream/123-a/topic/topic1', realmUrl),
+      (true, 'with numeric channel ID and topic',
+        '#narrow/channel/123-a/topic/topic1', realmUrl),
 
       (true, 'with numeric pm user IDs (new operator)',
         '#narrow/dm/123-mark', realmUrl),
@@ -69,20 +84,33 @@ void main() {
         '#nope', realmUrl),
       (false, 'wrong path',
         'user_uploads/#narrow/stream/check', realmUrl),
+      (false, 'wrong path with channel syntax',
+        'user_uploads/#narrow/channel/check', realmUrl),
       (false, 'wrong domain',
         'https://another.com/#narrow/stream/check', realmUrl),
+      (false, 'wrong domain with channel syntax',
+        'https://another.com/#narrow/channel/check', realmUrl),
 
       (false, '#narrowly',
         '#narrowly/stream/check', realmUrl),
+      (false, '#narrowly with channel syntax',
+        '#narrowly/channel/check', realmUrl),
 
       (false, 'double slash',
         'https://example.com//#narrow/stream/check', realmUrl),
+      (false, 'double slash with channel syntax',
+        'https://example.com//#narrow/channel/check', realmUrl),
       (false, 'triple slash',
         'https://example.com///#narrow/stream/check', realmUrl),
+      (false, 'triple slash with channel syntax',
+        'https://example.com///#narrow/channel/check', realmUrl),
 
       (true, 'with port',
         'https://example.com:444/#narrow/stream/check',
         Uri.parse('https://example.com:444/')),
+      (true, 'with port with channel syntax',
+        'https://example.com:444/#narrow/channel/check',
+        Uri.parse('https://example.com:444/')),
 
       // Dart's [Uri] currently lacks IDNA or Punycode support:
       //   https://github.com/dart-lang/sdk/issues/26284
@@ -95,6 +123,9 @@ void main() {
       (true, 'punycodable host',
         'https://example.भारत/#narrow/stream/check',
         Uri.parse('https://example.भारत/')),
+      (true, 'punycodable host with channel syntax',
+        'https://example.भारत/#narrow/channel/check',
+        Uri.parse('https://example.भारत/')),
 
       // (true, 'same domain, IDNA-mappable',
       //   'https://ℯⅩªm🄿ₗℰ.ℭᴼⓂ/#narrow/stream/check',
@@ -103,6 +134,9 @@ void main() {
       (true, 'ipv4 address',
         'http://192.168.0.1/#narrow/stream/check',
         Uri.parse('http://192.168.0.1/')),
+      (true, 'ipv4 address with channel syntax',
+        'http://192.168.0.1/#narrow/channel/check',
+        Uri.parse('http://192.168.0.1/')),
 
       // (true, 'same IPv4 address, IDNA-mappable',
       //   'http://１𝟗𝟚。①⁶🯸．₀｡𝟭/#narrow/stream/check',
@@ -119,12 +153,21 @@ void main() {
       (false, 'wrong domain, realm-like path, narrow-like fragment',
         'https://web.archive.org/web/*/${realmUrl.resolve('#narrow/stream/check')}',
         realmUrl),
+      (false, 'wrong domain, realm-like path, narrow-like fragment with channel syntax',
+        'https://web.archive.org/web/*/${realmUrl.resolve('#narrow/channel/check')}',
+        realmUrl),
       (false, 'odd scheme, wrong domain, realm-like path, narrow-like fragment',
         'ftp://web.archive.org/web/*/${realmUrl.resolve('#narrow/stream/check')}',
         realmUrl),
+      (false, 'odd scheme, wrong domain, realm-like path, narrow-like fragment with channel syntax',
+        'ftp://web.archive.org/web/*/${realmUrl.resolve('#narrow/channel/check')}',
+        realmUrl),
       (false, 'same domain, realm-like path, narrow-like fragment',
         'web/*/${realmUrl.resolve('#narrow/stream/check')}',
         realmUrl),
+      (false, 'same domain, realm-like path, narrow-like fragment with channel syntax',
+        'web/*/${realmUrl.resolve('#narrow/channel/check')}',
+        realmUrl),
     ];
     for (final testCase in testCases) {
       final bool expected = testCase.$1;