Be explicit about receivedAt time

We were often using `timestampForLegacySorting`, which is convoluted for when
we actually just want received time.

In some sense this is a superficial change, but it's part of auditing that
we've completed moved away from timestampForLegacySorting.

Signal/src/ViewControllers/ConversationView/Cells/OWSMessageHeaderView.m

@@ -126,8 +126,7 @@ const CGFloat OWSMessageHeaderViewDateHeaderVMargin = 23;
 {
     OWSAssertDebug(viewItem);
 
-    // MJK FIXME - use receivedDate for clarity
-    NSDate *date = viewItem.interaction.dateForLegacySorting;
+    NSDate *date = viewItem.interaction.receivedAtDate;
     NSString *dateString = [DateUtil formatDateForConversationDateBreaks:date].localizedUppercaseString;
 
     // Update cell to reflect changes in dynamic text.

Signal/src/ViewControllers/ConversationView/ConversationViewController.m

@@ -4926,9 +4926,7 @@ typedef enum : NSUInteger {
                 break;
         }
 
-        // MJK FIXME - should this be sentTime or receivedTime?
-        // we sorted by received time, but we should display sent time
-        uint64_t viewItemTimestamp = viewItem.interaction.timestampForLegacySorting;
+        uint64_t viewItemTimestamp = viewItem.interaction.receivedAtTimestamp;
         OWSAssertDebug(viewItemTimestamp > 0);
 
         BOOL shouldShowDate = NO;

Signal/src/ViewControllers/DebugUI/DebugUIDiskUsage.m

@@ -93,9 +93,8 @@ NS_ASSUME_NONNULL_BEGIN
                                                           TSInteraction *interaction,
                                                           NSUInteger index,
                                                           BOOL *stop) {
-                                                          // MJK FIXME - use receivedTime?
-                                                          NSTimeInterval ageSeconds = fabs(
-                                                              interaction.dateForLegacySorting.timeIntervalSinceNow);
+                                                          NSTimeInterval ageSeconds
+                                                              = fabs(interaction.receivedAtDate.timeIntervalSinceNow);
                                                           if (ageSeconds < maxAgeSeconds) {
                                                               *stop = YES;
                                                               return;

Signal/src/ViewControllers/MediaGalleryViewController.swift

@@ -54,8 +54,7 @@ public struct GalleryDate: Hashable, Comparable, Equatable {
     let month: Int
 
     init(message: TSMessage) {
-        // MJK FIXME - use `receivedTime` semantics are the same but would be clearer
-        let date = message.dateForLegacySorting()
+        let date = message.receivedAtDate()
 
         self.year = Calendar.current.component(.year, from: date)
         self.month = Calendar.current.component(.month, from: date)

Signal/src/ViewControllers/MessageDetailViewController.swift

@@ -292,10 +292,9 @@ class MessageDetailViewController: OWSViewController, MediaGalleryDataSourceDele
         rows.append(sentRow)
 
         if message as? TSIncomingMessage != nil {
-            // MJK FIXME - expose and use `receivedTime`?
             rows.append(valueRow(name: NSLocalizedString("MESSAGE_METADATA_VIEW_RECEIVED_DATE_TIME",
                                                          comment: "Label for the 'received date & time' field of the 'message metadata' view."),
-                                 value: DateUtil.formatPastTimestampRelativeToNow(message.timestampForLegacySorting())))
+                                 value: DateUtil.formatPastTimestampRelativeToNow(message.receivedAtTimestamp)))
         }
 
         rows += addAttachmentMetadataRows()

SignalServiceKit/src/Messages/Interactions/TSInteraction.h

@@ -34,6 +34,8 @@ NSString *NSStringFromOWSInteractionType(OWSInteractionType value);
 @property (nonatomic, readonly) TSThread *thread;
 @property (nonatomic, readonly) uint64_t timestamp;
 @property (nonatomic, readonly) uint64_t sortId;
+@property (nonatomic, readonly) uint64_t receivedAtTimestamp;
+- (NSDate *)receivedAtDate;
 
 - (OWSInteractionType)interactionType;
 

SignalServiceKit/src/Messages/Interactions/TSInteraction.m

@@ -92,6 +92,37 @@ NSString *NSStringFromOWSInteractionType(OWSInteractionType value)
 
     _timestamp = timestamp;
     _uniqueThreadId = thread.uniqueId;
+    _receivedAtTimestamp = [NSDate ows_millisecondTimeStamp];
+
+    return self;
+}
+
+- (nullable instancetype)initWithCoder:(NSCoder *)coder
+{
+    self = [super initWithCoder:coder];
+    if (!self) {
+        return nil;
+    }
+
+    // Previously the receivedAtTimestamp field lived on TSMessage, but we've moved it up
+    // to the TSInteraction superclass.
+    if (_receivedAtTimestamp == 0) {
+        // Upgrade from the older "TSMessage.receivedAtDate" and "TSMessage.receivedAt" properties if
+        // necessary.
+        NSDate *receivedAtDate = [coder decodeObjectForKey:@"receivedAtDate"];
+        if (!receivedAtDate) {
+            receivedAtDate = [coder decodeObjectForKey:@"receivedAt"];
+        }
+
+        if (receivedAtDate) {
+            _receivedAtTimestamp = [NSDate ows_millisecondsSince1970ForDate:receivedAtDate];
+        }
+
+        // For TSInteractions which are not TSMessage's, the timestamp *is* the receivedAtTimestamp
+        if (_receivedAtTimestamp == 0) {
+            _receivedAtTimestamp = _timestamp;
+        }
+    }
 
     return self;
 }
@@ -126,6 +157,11 @@ NSString *NSStringFromOWSInteractionType(OWSInteractionType value)
     return self.timestamp;
 }
 
+- (NSDate *)receivedAtDate
+{
+    return [NSDate ows_dateWithMillisecondsSince1970:self.receivedAtTimestamp];
+}
+
 - (NSComparisonResult)compareForSorting:(TSInteraction *)other
 {
     OWSAssertDebug(other);

SignalServiceKit/src/Messages/Interactions/TSMessage.m

@@ -47,14 +47,6 @@ static const NSUInteger OWSMessageSchemaVersion = 4;
  */
 @property (nonatomic, readonly) NSUInteger schemaVersion;
 
-// MJK FIXME - update this comment
-// The timestamp property is populated by the envelope,
-// which is created by the sender.
-//
-// We typically want to order messages locally by when
-// they were received & decrypted, not by when they were sent.
-@property (nonatomic) uint64_t receivedAtTimestamp;
-
 @end
 
 #pragma mark -
@@ -83,7 +75,6 @@ static const NSUInteger OWSMessageSchemaVersion = 4;
     _expiresInSeconds = expiresInSeconds;
     _expireStartedAt = expireStartedAt;
     [self updateExpiresAt];
-    _receivedAtTimestamp = [NSDate ows_millisecondTimeStamp];
     _quotedMessage = quotedMessage;
     _contactShare = contactShare;
 
@@ -136,18 +127,6 @@ static const NSUInteger OWSMessageSchemaVersion = 4;
         _attachmentIds = [NSMutableArray new];
     }
 
-    if (_receivedAtTimestamp == 0) {
-        // Upgrade from the older "receivedAtDate" and "receivedAt" properties if
-        // necessary.
-        NSDate *receivedAtDate = [coder decodeObjectForKey:@"receivedAtDate"];
-        if (!receivedAtDate) {
-            receivedAtDate = [coder decodeObjectForKey:@"receivedAt"];
-        }
-        if (receivedAtDate) {
-            _receivedAtTimestamp = [NSDate ows_millisecondsSince1970ForDate:receivedAtDate];
-        }
-    }
-
     _schemaVersion = OWSMessageSchemaVersion;
 
     return self;

SignalServiceKit/src/Messages/OWSDisappearingMessagesJob.m

@@ -393,8 +393,7 @@ void AssertIsOnDisappearingMessagesQueue()
             OWSFailDebug(@"starting old timer for message timestamp: %lu", (unsigned long)message.timestamp);
 
             // We don't know when it was actually read, so assume it was read as soon as it was received.
-            // MJK FIXME - this needs to use sortId
-            uint64_t readTimeBestGuess = message.timestampForLegacySorting;
+            uint64_t readTimeBestGuess = message.receivedAtTimestamp;
             [self startAnyExpirationForMessage:message expirationStartedAt:readTimeBestGuess transaction:transaction];
         }
                                                  transaction:transaction];