Fixing UX issue with unsynchronized clocks.

TextSecure messages don’t get assigned a timestamp by the server. All
of it is done end-to-end between both clients. A client could have a
misconfigured clock or might want to forge a timestamp. Therefore, we
address this issue by introducing a new receivedAt timestamp for
incoming messages that will be used to sort the messages.

Signal/src/textsecure/Messages/TSIncomingMessage.h

@@ -42,9 +42,10 @@
                          inThread:(TSGroupThread*)thread
                          authorId:(NSString*)authorId
                       messageBody:(NSString*)body
-                     attachments:(NSArray*)attachments;
+                      attachments:(NSArray*)attachments;
 
 @property (nonatomic, readonly) NSString *authorId;
 @property (nonatomic, getter = wasRead) BOOL read;
+@property (nonatomic, readonly) NSDate   *receivedAt;
 
 @end

Signal/src/textsecure/Messages/TSIncomingMessage.m

@@ -19,8 +19,9 @@
     self = [super initWithTimestamp:timestamp inThread:thread messageBody:body attachments:attachments];
     
     if (self) {
-        _authorId = authorId;
-        _read     = NO;
+        _authorId   = authorId;
+        _read       = NO;
+        _receivedAt = [NSDate date];
     }
     
     return self;
@@ -34,8 +35,9 @@
     self = [super initWithTimestamp:timestamp inThread:thread messageBody:body attachments:attachments];
     
     if (self) {
-        _authorId = nil;
-        _read     = NO;
+        _authorId   = nil;
+        _read       = NO;
+        _receivedAt = [NSDate date];
     }
     
     return self;

Signal/src/textsecure/Storage/TSDatabaseView.m

@@ -163,11 +163,42 @@ NSString *TSUnreadDatabaseViewExtensionName  = @"TSUnreadDatabaseViewExtensionNa
             TSInteraction *message1 = (TSInteraction*)object1;
             TSInteraction *message2 = (TSInteraction*)object2;
             
-            return [message1.date compare:message2.date];
+            NSDate *date1 = [self localTimeReceiveDateForInteraction:message1];
+            NSDate *date2 = [self localTimeReceiveDateForInteraction:message2];
+            
+            NSComparisonResult result = [date1 compare:date2];
+            
+            // NSDates are only accurate to the second, we might want finer precision
+            if (result != NSOrderedSame) {
+                return result;
+            }
+            
+            if (message1.timestamp > message2.timestamp) {
+                return NSOrderedDescending;
+            } else if (message1.timestamp < message2.timestamp){
+                return NSOrderedAscending;
+            } else{
+                return NSOrderedSame;
+            }
         }
         
         return NSOrderedSame;
     }];
 }
 
++ (NSDate*)localTimeReceiveDateForInteraction:(TSInteraction*)interaction{
+    NSDate *interactionDate = interaction.date;
+    
+    if ([interaction isKindOfClass:[TSIncomingMessage class]]) {
+        TSIncomingMessage *message = (TSIncomingMessage*)interaction;
+        
+        if (message.receivedAt) {
+            interactionDate = message.receivedAt;
+        }
+        
+    }
+    
+    return interactionDate;
+}
+
 @end