Respond to CR.

// FREEBIE

src/Contacts/TSThread.m

@@ -246,14 +246,7 @@ NS_ASSUME_NONNULL_BEGIN
 }
 
 - (void)updateWithLastMessage:(TSInteraction *)lastMessage transaction:(YapDatabaseReadWriteTransaction *)transaction {
-    NSDate *lastMessageDate = lastMessage.date;
-
-    if ([lastMessage isKindOfClass:[TSMessage class]]) {
-        TSMessage *message = (TSMessage *)lastMessage;
-        if ([message bestReceivedAtDate]) {
-            lastMessageDate = [message bestReceivedAtDate];
-        }
-    }
+    NSDate *lastMessageDate = [lastMessage receiptDateForSorting];
 
     if (!_lastMessageDate || [lastMessageDate timeIntervalSinceDate:self.lastMessageDate] > 0) {
         _lastMessageDate = lastMessageDate;

src/Messages/Interactions/TSIncomingMessage.h

@@ -121,13 +121,6 @@ extern NSString *const TSIncomingMessageWasReadOnThisDeviceNotification;
 
 @property (nonatomic, readonly) NSString *authorId;
 @property (nonatomic, readonly, getter=wasRead) BOOL read;
-// _DO NOT_ access this property directly.  You almost certainly
-// want to use bestReceivedAtDate instead.
-//
-// This property has been superceded by TSMessage.receivedAtData.
-// This property only exists for backwards compatability with messages
-// received before TSMessage.receivedAtData was added.
-@property (nonatomic, readonly) NSDate *receivedAt;
 
 /*
  * Marks a message as having been read on this device (as opposed to responding to a remote read receipt).

src/Messages/Interactions/TSIncomingMessage.m

@@ -135,18 +135,6 @@ NSString *const TSIncomingMessageWasReadOnThisDeviceNotification = @"TSIncomingM
     [self touchThreadWithTransaction:transaction];
 }
 
-- (nullable NSDate *)bestReceivedAtDate
-{
-    NSDate *result = [super bestReceivedAtDate];
-    if (!result) {
-        // For backward compatibility with messages received before
-        // TSMessage.receivedAtData was added, honor TSIncomingMessage.receivedAt
-        // if TSMessage.receivedAtData is not set.
-        result = self.receivedAt;
-    }
-    return result;
-}
-
 #pragma mark - Logging
 
 + (NSString *)tag

src/Messages/Interactions/TSInteraction.h

@@ -31,5 +31,6 @@
 + (instancetype)interactionForTimestamp:(uint64_t)timestamp
                         withTransaction:(YapDatabaseReadWriteTransaction *)transaction;
 
+- (nullable NSDate *)receiptDateForSorting;
 
 @end

src/Messages/Interactions/TSInteraction.m

@@ -86,6 +86,11 @@
     return [myNumber unsignedLongLongValue];
 }
 
+- (nullable NSDate *)receiptDateForSorting
+{
+    return self.date;
+}
+
 - (NSString *)description {
     return @"Interaction description";
 }

src/Messages/Interactions/TSMessage.h

@@ -31,7 +31,7 @@ typedef NS_ENUM(NSInteger, TSGroupMetaMessage) {
 @property (nonatomic, readonly) BOOL isExpiringMessage;
 @property (nonatomic, readonly) BOOL shouldStartExpireTimer;
 // _DO NOT_ access this property directly.  You almost certainly
-// want to use bestReceivedAtDate instead.
+// want to use receiptDateForSorting instead.
 @property (nonatomic, readonly) NSDate *receivedAtDate;
 
 - (instancetype)initWithTimestamp:(uint64_t)timestamp;
@@ -64,11 +64,6 @@ typedef NS_ENUM(NSInteger, TSGroupMetaMessage) {
 
 - (BOOL)hasAttachments;
 
-// This message should return TSMessage.receivedAtDate for most messages.
-// For messages received before TSMessage.receivedAtDate was added, this
-// will try to return TSIncomingMessage.receivedAt.
-- (nullable NSDate *)bestReceivedAtDate;
-
 @end
 
 NS_ASSUME_NONNULL_END

src/Messages/Interactions/TSMessage.m

@@ -132,10 +132,13 @@ static const NSUInteger OWSMessageSchemaVersion = 3;
         _attachmentIds = [NSMutableArray new];
     }
 
-    _schemaVersion = OWSMessageSchemaVersion;
+    if (!_receivedAtDate) {
+        // TSIncomingMessage.receivedAt has been superceded by TSMessage.receivedAtDate.
+        NSDate *receivedAt = [coder decodeObjectForKey:@"receivedAt"];
+        _receivedAtDate = receivedAt;
+    }
 
-    // We _DO NOT_ set _receivedAt_ in this constructor.  We don't want to
-    // set the receivedAt time for old messages in the data store.
+    _schemaVersion = OWSMessageSchemaVersion;
 
     return self;
 }
@@ -220,9 +223,22 @@ static const NSUInteger OWSMessageSchemaVersion = 3;
     return self.expiresInSeconds > 0;
 }
 
-- (nullable NSDate *)bestReceivedAtDate
+- (nullable NSDate *)receiptDateForSorting
+{
+    // Prefer receivedAtDate if set, otherwise fallback to date.
+    return self.receivedAtDate ?: self.date;
+}
+
+#pragma mark - Logging
+
++ (NSString *)tag
+{
+    return [NSString stringWithFormat:@"[%@]", self.class];
+}
+
+- (NSString *)tag
 {
-    return self.receivedAtDate;
+    return self.class.tag;
 }
 
 @end

src/Storage/TSDatabaseView.m

@@ -264,16 +264,7 @@ NSString *TSSecondaryDevicesDatabaseViewExtensionName = @"TSSecondaryDevicesData
 }
 
 + (NSDate *)localTimeReceiveDateForInteraction:(TSInteraction *)interaction {
-    NSDate *interactionDate = interaction.date;
-
-    if ([interaction isKindOfClass:[TSMessage class]]) {
-        TSMessage *message = (TSMessage *)interaction;
-        if ([message bestReceivedAtDate]) {
-            interactionDate = [message bestReceivedAtDate];
-        }
-    }
-
-    return interactionDate;
+    return [interaction receiptDateForSorting];
 }
 
 #pragma mark - Logging