local echo (4.5/n): Prep for creating outbox messages on send

lib/api/model/model.dart

@@ -550,6 +550,15 @@ String? tryParseEmojiCodeToUnicode(String emojiCode) {
   }
 }
 
+/// The topic servers understand to mean "there is no topic".
+///
+/// This should match
+///   https://github.com/zulip/zulip/blob/6.0/zerver/actions/message_edit.py#L940
+/// or similar logic at the latest `main`.
+// This is hardcoded in the server, and therefore untranslated; that's
+// zulip/zulip#3639.
+const String kNoTopicTopic = '(no topic)';
+
 /// The name of a Zulip topic.
 // TODO(dart): Can we forbid calling Object members on this extension type?
 //   (The lack of "implements Object" ought to do that, but doesn't.)
@@ -604,6 +613,51 @@ extension type const TopicName(String _value) {
   /// using [canonicalize].
   bool isSameAs(TopicName other) => canonicalize() == other.canonicalize();
 
+  /// Process this topic to match how it would appear on a message object from
+  /// the server.
+  ///
+  /// This assumes that the topic is constructed from a string without
+  /// leading/trailing whitespace.
+  ///
+  /// For a client that does not support empty topics, when FL>=334, the server
+  /// converts empty topics to `store.realmEmptyTopicDisplayName`; when FL>=370,
+  /// the server converts "(no topic)" to `store.realmEmptyTopicDisplayName`
+  /// as well.
+  ///
+  /// See API docs:
+  ///   https://zulip.com/api/send-message#parameter-topic
+  TopicName processLikeServer({
+    required int zulipFeatureLevel,
+    required String? realmEmptyTopicDisplayName,
+  }) {
+    assert(_value.trim() == _value);
+    // TODO(server-10) simplify this away
+    if (zulipFeatureLevel < 334) {
+      // From the API docs:
+      // > Before Zulip 10.0 (feature level 334), empty string was not a valid
+      // > topic name for channel messages.
+      assert(_value.isNotEmpty);
+      return this;
+    }
+
+    // TODO(server-10) simplify this away
+    if (zulipFeatureLevel < 370 && _value == kNoTopicTopic) {
+      // From the API docs:
+      // > Before Zulip 10.0 (feature level 370), "(no topic)" was not
+      // > interpreted as an empty string.
+      return TopicName(kNoTopicTopic);
+    }
+
+    // TODO(#1250): This assumes that the 'empty_topic_name' client capability
+    //   is not declared. When we set 'empty_topic_name' to true,
+    //   make this return an empty topic if the value matches "(no topic)"
+    //   or realmEmptyTopicDisplayName.
+    if (_value == kNoTopicTopic || _value.isEmpty) {
+      return TopicName(realmEmptyTopicDisplayName!);
+    }
+    return TopicName(_value);
+  }
+
   TopicName.fromJson(this._value);
 
   String toJson() => apiName;

lib/api/route/messages.dart

@@ -169,15 +169,6 @@ const int kMaxTopicLengthCodePoints = 60;
 // https://zulip.com/api/send-message#parameter-content
 const int kMaxMessageLengthCodePoints = 10000;
 
-/// The topic servers understand to mean "there is no topic".
-///
-/// This should match
-///   https://github.com/zulip/zulip/blob/6.0/zerver/actions/message_edit.py#L940
-/// or similar logic at the latest `main`.
-// This is hardcoded in the server, and therefore untranslated; that's
-// zulip/zulip#3639.
-const String kNoTopicTopic = '(no topic)';
-
 /// https://zulip.com/api/send-message
 Future<SendMessageResult> sendMessage(
   ApiConnection connection, {

lib/model/binding.dart

@@ -120,6 +120,11 @@ abstract class ZulipBinding {
   /// This wraps [url_launcher.closeInAppWebView].
   Future<void> closeInAppWebView();
 
+  /// Provides access to the current UTC date and time.
+  ///
+  /// Outside tests, this just calls [DateTime.timestamp].
+  DateTime utcNow();
+
   /// Provides access to a new stopwatch.
   ///
   /// Outside tests, this just calls the [Stopwatch] constructor.
@@ -383,6 +388,9 @@ class LiveZulipBinding extends ZulipBinding {
     return url_launcher.closeInAppWebView();
   }
 
+  @override
+  DateTime utcNow() => DateTime.timestamp();
+
   @override
   Stopwatch stopwatch() => Stopwatch();
 

lib/model/store.dart

@@ -385,6 +385,12 @@ abstract class PerAccountStoreBase {
   /// This returns null if [reference] fails to parse as a URL.
   Uri? tryResolveUrl(String reference) => _tryResolveUrl(realmUrl, reference);
 
+  /// Always equal to `connection.zulipFeatureLevel`
+  /// and `account.zulipFeatureLevel`.
+  int get zulipFeatureLevel => connection.zulipFeatureLevel!;
+
+  String get zulipVersion => account.zulipVersion;
+
   ////////////////////////////////
   // Data attached to the self-account on the realm.
 
@@ -558,11 +564,6 @@ class PerAccountStore extends PerAccountStoreBase with ChangeNotifier, EmojiStor
   ////////////////////////////////
   // Data attached to the realm or the server.
 
-  /// Always equal to `connection.zulipFeatureLevel`
-  /// and `account.zulipFeatureLevel`.
-  int get zulipFeatureLevel => connection.zulipFeatureLevel!;
-
-  String get zulipVersion => account.zulipVersion;
   final RealmWildcardMentionPolicy realmWildcardMentionPolicy; // TODO(#668): update this realm setting
   final bool realmMandatoryTopics;  // TODO(#668): update this realm setting
   /// For docs, please see [InitialSnapshot.realmWaitingPeriodThreshold].

test/api/model/model_test.dart

@@ -161,6 +161,31 @@ void main() {
 
       doCheck(eg.t('✔ a'),          eg.t('✔ b'),          false);
     });
+
+    test('processLikeServer', () {
+      final emptyTopicDisplayName = eg.defaultRealmEmptyTopicDisplayName;
+      void doCheck(TopicName topic, TopicName expected, int zulipFeatureLevel) {
+        check(topic.processLikeServer(
+          zulipFeatureLevel: zulipFeatureLevel,
+          realmEmptyTopicDisplayName: emptyTopicDisplayName),
+        ).equals(expected);
+      }
+
+      check(() => eg.t('').processLikeServer(
+        zulipFeatureLevel: 333,
+        realmEmptyTopicDisplayName: emptyTopicDisplayName),
+      ).throws<void>();
+      doCheck(eg.t('(no topic)'),          eg.t('(no topic)'),          333);
+      doCheck(eg.t(emptyTopicDisplayName), eg.t(emptyTopicDisplayName), 333);
+      doCheck(eg.t('other topic'),         eg.t('other topic'),         333);
+
+      doCheck(eg.t(''),                    eg.t(emptyTopicDisplayName), 334);
+      doCheck(eg.t('(no topic)'),          eg.t('(no topic)'),          334);
+      doCheck(eg.t(emptyTopicDisplayName), eg.t(emptyTopicDisplayName), 334);
+      doCheck(eg.t('other topic'),         eg.t('other topic'),         334);
+
+      doCheck(eg.t('(no topic)'),          eg.t(emptyTopicDisplayName), 370);
+    });
   });
 
   group('DmMessage', () {

test/example_data.dart

@@ -69,6 +69,20 @@ ZulipApiException apiExceptionUnauthorized({String routeName = 'someRoute'}) {
     data: {}, message: 'Invalid API key');
 }
 
+////////////////////////////////////////////////////////////////
+// Time values.
+//
+
+final timeInPast = DateTime.utc(2025, 4, 1, 8, 30, 0);
+
+/// The UNIX timestamp, in UTC seconds.
+///
+/// This is the commonly used format in the Zulip API for timestamps.
+int utcTimestamp([DateTime? dateTime]) {
+  dateTime ??= timeInPast;
+  return dateTime.toUtc().millisecondsSinceEpoch ~/ 1000;
+}
+
 ////////////////////////////////////////////////////////////////
 // Realm-wide (or server-wide) metadata.
 //

test/model/binding.dart

@@ -241,6 +241,9 @@ class TestZulipBinding extends ZulipBinding {
     _closeInAppWebViewCallCount++;
   }
 
+  @override
+  DateTime utcNow() => clock.now().toUtc();
+
   @override
   Stopwatch stopwatch() => clock.stopwatch();