use sent timestamp instead of received timestamp for sorting and UI

Session/Conversations/Message Cells/VisibleMessageCell.swift

@@ -286,7 +286,7 @@ final class VisibleMessageCell : MessageCell, LinkPreviewViewDelegate {
         dateBreakLabel.font = .boldSystemFont(ofSize: Values.verySmallFontSize)
         dateBreakLabel.textColor = Colors.text
         dateBreakLabel.textAlignment = .center
-        let date = viewItem.interaction.receivedAtDate()
+        let date = viewItem.interaction.dateForUI()
         let description = DateUtil.formatDate(forConversationDateBreaks: date)
         dateBreakLabel.text = description
         headerView.addSubview(dateBreakLabel)

Session/Media Viewing & Editing/MediaGalleryViewController.swift

@@ -120,7 +120,7 @@ public struct GalleryDate: Hashable, Comparable, Equatable {
     let month: Int
 
     init(message: TSMessage) {
-        let date = message.receivedAtDate()
+        let date = message.dateForUI()
 
         self.year = Calendar.current.component(.year, from: date)
         self.month = Calendar.current.component(.month, from: date)

SessionMessagingKit/Messages/Signal/TSInteraction.h

@@ -43,6 +43,8 @@ NSString *NSStringFromOWSInteractionType(OWSInteractionType value);
 
 - (uint64_t)timestampForUI;
 
+- (NSDate *)dateForUI;
+
 - (NSDate *)receivedAtDate;
 
 - (OWSInteractionType)interactionType;

SessionMessagingKit/Messages/Signal/TSInteraction.m

@@ -180,8 +180,14 @@ NSString *NSStringFromOWSInteractionType(OWSInteractionType value)
     return self.timestamp;
 }
 
+- (NSDate *)dateForUI
+{
+    return [NSDate ows_dateWithMillisecondsSince1970:self.timestampForUI];
+}
+
 - (NSDate *)receivedAtDate
 {
+    // This is only used for sorting threads
     return [NSDate ows_dateWithMillisecondsSince1970:self.receivedAtTimestamp];
 }
 
@@ -222,13 +228,8 @@ NSString *NSStringFromOWSInteractionType(OWSInteractionType value)
 
 - (uint64_t)sortId
 {
-    if ([self isKindOfClass:TSIncomingMessage.class] && ((TSIncomingMessage *) self).isOpenGroupMessage) {
+    if ([self isKindOfClass:TSIncomingMessage.class] && ((TSIncomingMessage *) self).isOpenGroupMessage && ((TSIncomingMessage *) self).serverTimestamp != nil) {
-        if (((TSIncomingMessage *) self).serverTimestamp != nil) {
+        return ((TSIncomingMessage *) self).serverTimestamp.unsignedLongLongValue;
-            return ((TSIncomingMessage *) self).serverTimestamp.unsignedLongLongValue;
-        }
-        // For messages that don't have a serverTimestamp, it is the same to sort by the receivedAtTimestamp,
-        // since in the open group poller we sort messages by their server timestamp.
-        return ((TSIncomingMessage *) self).receivedAtTimestamp;
     }
     return self.timestamp;
 }

SignalUtilitiesKit/Messaging/ThreadViewModel.swift

@@ -32,7 +32,7 @@ public class ThreadViewModel: NSObject {
         self.lastMessageText = thread.lastMessageText(transaction: transaction)
         let lastInteraction = thread.lastInteractionForInbox(transaction: transaction)
         self.lastMessageForInbox = lastInteraction
-        self.lastMessageDate = lastInteraction?.receivedAtDate() ?? thread.creationDate
+        self.lastMessageDate = lastInteraction?.dateForUI() ?? thread.creationDate
 
         if let contactThread = thread as? TSContactThread {
             self.contactIdentifier = contactThread.contactIdentifier()