msglist: Separate messages after 10-min gap, with a sender row

Fixes: #1773

Author: rajveermalviya

lib/model/message_list.dart

@@ -459,8 +459,10 @@ mixin _MessageSequence {
       if (!messagesSameDay(prevMessageItem.message, message)) {
         items.add(MessageListDateSeparatorItem(message));
         canShareSender = false;
+      } else if (prevMessageItem.message.senderId == message.senderId) {
+        canShareSender = messagesWithinTenMinutes(prevMessage, message);
       } else {
-        canShareSender = prevMessageItem.message.senderId == message.senderId;
+        canShareSender = false;
       }
     }
     final item = buildItem(canShareSender);
@@ -568,6 +570,13 @@ bool messagesSameDay(MessageBase prevMessage, MessageBase message) {
   return true;
 }
 
+@visibleForTesting
+bool messagesWithinTenMinutes(MessageBase prevMessage, MessageBase message) {
+  final diffSeconds = (message.timestamp - prevMessage.timestamp).abs();
+  if (diffSeconds <= 10 * 60) return true;
+  return false;
+}
+
 bool _sameDay(DateTime date1, DateTime date2) {
   if (date1.year != date2.year) return false;
   if (date1.month != date2.month) return false;

test/model/message_list_test.dart

@@ -2948,7 +2948,14 @@ void main() {
 
     final now = clock.now();
     final t1 = eg.utcTimestamp(now.subtract(Duration(days: 1)));
-    final t2 = eg.utcTimestamp(now);
+    final t2 = eg.utcTimestamp(
+      now.subtract(Duration(days: 1))
+        .add(Duration(minutes: 1)));
+    final t3 = eg.utcTimestamp(
+      now.subtract(Duration(days: 1))
+        .add(Duration(minutes: 1))
+        .add(Duration(minutes: 10, seconds: 1)));
+    final t4 = eg.utcTimestamp(now);
     final stream = eg.stream(streamId: eg.defaultStreamMessageStreamId);
     Message streamMessage(int id, int timestamp, User sender) =>
       eg.streamMessage(id: id, sender: sender,
@@ -2964,15 +2971,17 @@ void main() {
       streamMessage(1, t1, eg.selfUser),  // first message, so show sender
       streamMessage(2, t1, eg.selfUser),  // hide sender
       streamMessage(3, t1, eg.otherUser), // no recipient header, but new sender
-      dmMessage(4,     t1, eg.otherUser), // same sender, but new recipient
-      dmMessage(5,     t2, eg.otherUser), // same sender/recipient, but new day
+      streamMessage(5, t2, eg.otherUser), // same sender, but within 10 mins of last message
+      streamMessage(6, t3, eg.otherUser), // same sender, after 10 mins of last message
+      dmMessage(7,     t3, eg.otherUser), // same sender, but new recipient
+      dmMessage(8,     t4, eg.otherUser), // same sender/recipient, but new day
     ]);
     await prepareOutboxMessagesTo([
       dmDestination([eg.selfUser, eg.otherUser]), // same day, but new sender
       dmDestination([eg.selfUser, eg.otherUser]), // hide sender
     ]);
     assert(
-      store.outboxMessages.values.every((message) => message.timestamp == t2));
+      store.outboxMessages.values.every((message) => message.timestamp == t4));
     async.elapse(kLocalEchoDebounceDuration);
 
     // We check showSender has the right values in [checkInvariants],
@@ -2982,6 +2991,8 @@ void main() {
       (it) => it.isA<MessageListMessageItem>().showSender.isTrue(),
       (it) => it.isA<MessageListMessageItem>().showSender.isFalse(),
       (it) => it.isA<MessageListMessageItem>().showSender.isTrue(),
+      (it) => it.isA<MessageListMessageItem>().showSender.isFalse(),
+      (it) => it.isA<MessageListMessageItem>().showSender.isTrue(),
       (it) => it.isA<MessageListRecipientHeaderItem>(),
       (it) => it.isA<MessageListMessageItem>().showSender.isTrue(),
       (it) => it.isA<MessageListDateSeparatorItem>(),
@@ -3072,14 +3083,14 @@ void main() {
     });
   });
 
-  test('messagesSameDay', () {
-    // These timestamps will differ depending on the timezone of the
-    // environment where the tests are run, in order to give the same results
-    // in the code under test which is also based on the ambient timezone.
-    // TODO(dart): It'd be great if tests could control the ambient timezone,
-    //   so as to exercise cases like where local time falls back across midnight.
-    int timestampFromLocalTime(String date) => DateTime.parse(date).millisecondsSinceEpoch ~/ 1000;
+  // These timestamps will differ depending on the timezone of the
+  // environment where the tests are run, in order to give the same results
+  // in the code under test which is also based on the ambient timezone.
+  // TODO(dart): It'd be great if tests could control the ambient timezone,
+  //   so as to exercise cases like where local time falls back across midnight.
+  int timestampFromLocalTime(String date) => DateTime.parse(date).millisecondsSinceEpoch ~/ 1000;
 
+  test('messagesSameDay', () {
     const t111a = '2021-01-01 00:00:00';
     const t111b = '2021-01-01 12:00:00';
     const t111c = '2021-01-01 23:59:58';
@@ -3118,6 +3129,46 @@ void main() {
       }
     }
   });
+
+  group('messagesWithinTenMinutes', () {
+    final stream = eg.stream();
+    void doTest(String time0, String time1, bool expected) {
+      test('$time0 $time1', () {
+        check(messagesWithinTenMinutes(
+          eg.streamMessage(stream: stream, topic: 'foo', timestamp: timestampFromLocalTime(time0)),
+          eg.streamMessage(stream: stream, topic: 'foo', timestamp: timestampFromLocalTime(time1)),
+        )).equals(expected);
+        check(messagesWithinTenMinutes(
+          eg.dmMessage(from: eg.selfUser, to: [], timestamp: timestampFromLocalTime(time0)),
+          eg.dmMessage(from: eg.selfUser, to: [], timestamp: timestampFromLocalTime(time1)),
+        )).equals(expected);
+        check(messagesWithinTenMinutes(
+          eg.streamOutboxMessage(timestamp: timestampFromLocalTime(time0)),
+          eg.streamOutboxMessage(timestamp: timestampFromLocalTime(time1)),
+        )).equals(expected);
+        check(messagesWithinTenMinutes(
+          eg.dmOutboxMessage(from: eg.selfUser, to: [], timestamp: timestampFromLocalTime(time0)),
+          eg.dmOutboxMessage(from: eg.selfUser, to: [], timestamp: timestampFromLocalTime(time1)),
+        )).equals(expected);
+      });
+    }
+
+    const time = '2021-01-01 00:30:00';
+
+    doTest('2021-01-01 00:19:59', time, false);
+    doTest('2021-01-01 00:20:00', time, true);
+    doTest('2021-01-01 00:20:01', time, true);
+    doTest('2021-01-01 00:25:00', time, true);
+    doTest('2021-01-01 00:29:59', time, true);
+
+    doTest(time, '2021-01-01 00:30:00', true);
+
+    doTest(time, '2021-01-01 00:30:01', true);
+    doTest(time, '2021-01-01 00:35:00', true);
+    doTest(time, '2021-01-01 00:39:59', true);
+    doTest(time, '2021-01-01 00:40:00', true);
+    doTest(time, '2021-01-01 00:40:01', false);
+  });
 }
 
 MessageListView? _lastModel;
@@ -3234,6 +3285,12 @@ void checkInvariants(MessageListView model) {
       check(model.items[i++]).isA<MessageListDateSeparatorItem>()
         .message.identicalTo(allMessages[j]);
       forcedShowSender = true;
+    } else if (allMessages[j-1].senderId == allMessages[j].senderId) {
+      if (!messagesWithinTenMinutes(allMessages[j-1], allMessages[j])) {
+        forcedShowSender = true;
+      }
+    } else if (allMessages[j-1].senderId != allMessages[j].senderId) {
+      forcedShowSender = true;
     }
     if (j < model.messages.length) {
       check(model.items[i]).isA<MessageListMessageItem>()
@@ -3244,8 +3301,7 @@ void checkInvariants(MessageListView model) {
         .message.identicalTo(model.outboxMessages[j-model.messages.length]);
     }
     check(model.items[i++]).isA<MessageListMessageBaseItem>()
-      ..showSender.equals(
-        forcedShowSender || allMessages[j].senderId != allMessages[j-1].senderId)
+      ..showSender.equals(forcedShowSender)
       ..isLastInBlock.equals(
         i == model.items.length || switch (model.items[i]) {
           MessageListMessageItem()