Fix minor logic issue & document friend request handling

SignalServiceKit/src/Contacts/TSThread.h

@@ -31,17 +31,17 @@ extern ConversationColorName const kConversationColorName_Default;
 
 // Loki: Friend request state
 typedef NS_ENUM(NSInteger, TSThreadFriendRequestStatus) {
-    // New conversation, no messages sent or received
+    /// New conversation, no messages sent or received
     TSThreadFriendRequestStatusNone,
-    // This state is used to lock the input early while sending
+    /// This state is used to lock the input early while sending
-    TSThreadFriendRequestStatusPendingSend,
+    TSThreadFriendRequestStatusRequestSending,
-    // Friend request sent, awaiting response
+    /// Friend request sent, awaiting response
     TSThreadFriendRequestStatusRequestSent,
-    // Friend request received, awaiting user input
+    /// Friend request received, awaiting user input
     TSThreadFriendRequestStatusRequestReceived,
-    // We are friends with the user of this thread
+    /// We are friends with the user of this thread
     TSThreadFriendRequestStatusFriends,
-    // Friend request sent but it timed out (user didn't accept within x time)
+    /// Friend request sent but it timed out (user didn't accept within x time)
     TSThreadFriendRequestStatusRequestExpired
 };
 
@@ -54,13 +54,15 @@ typedef NS_ENUM(NSInteger, TSThreadFriendRequestStatus) {
 @property (nonatomic, readonly) NSDate *creationDate;
 @property (nonatomic, readonly) BOOL isArchivedByLegacyTimestampForSorting;
 // Loki friend request handling
+// ========
 @property (nonatomic) TSThreadFriendRequestStatus friendRequestStatus;
-/// Shorthand for checking that `friendRequestStatus` is `TSThreadFriendRequestStatusPendingSend`, `TSThreadFriendRequestStatusRequestSent`
+/// Shorthand for checking that `friendRequestStatus` is `TSThreadFriendRequestStatusRequestSending`, `TSThreadFriendRequestStatusRequestSent`
 /// or `TSThreadFriendRequestStatusRequestReceived`.
 @property (nonatomic, readonly) BOOL hasPendingFriendRequest;
 @property (nonatomic, readonly) BOOL isContactFriend;
 @property (nonatomic, readonly) BOOL hasCurrentUserSentFriendRequest;
 @property (nonatomic, readonly) BOOL hasCurrentUserReceivedFriendRequest;
+// ========
 
 /**
  *  Whether the object is a group thread or not.

SignalServiceKit/src/Contacts/TSThread.m

@@ -710,7 +710,7 @@ ConversationColorName const kConversationColorName_Default = ConversationColorNa
 
 - (BOOL)hasPendingFriendRequest
 {
-    return self.friendRequestStatus == TSThreadFriendRequestStatusPendingSend || self.friendRequestStatus == TSThreadFriendRequestStatusRequestSent
+    return self.friendRequestStatus == TSThreadFriendRequestStatusRequestSending || self.friendRequestStatus == TSThreadFriendRequestStatusRequestSent
         || self.friendRequestStatus == TSThreadFriendRequestStatusRequestReceived;
 }
 

SignalServiceKit/src/Messages/Interactions/TSMessage.h

@@ -28,7 +28,7 @@ NS_ASSUME_NONNULL_BEGIN
 @property (nonatomic, readonly, nullable) TSQuotedMessage *quotedMessage;
 @property (nonatomic, readonly, nullable) OWSContact *contactShare;
 @property (nonatomic, readonly, nullable) OWSLinkPreview *linkPreview;
-@property (nonatomic) BOOL isFriendRequest;
+@property (nonatomic) BOOL isFriendRequest; // Loki
 
 - (instancetype)initInteractionWithTimestamp:(uint64_t)timestamp inThread:(TSThread *)thread NS_UNAVAILABLE;
 

SignalServiceKit/src/Messages/OWSMessageManager.m

@@ -1446,12 +1446,32 @@ NS_ASSUME_NONNULL_BEGIN
     // ========
     if (envelope.type == SSKProtoEnvelopeTypeFriendRequest) {
         if (thread.hasCurrentUserSentFriendRequest) {
+            // This can happen if Alice sent Bob a friend request, Bob declined, but then Bob changed his
+            // mind and sent a friend request to Alice. In this case we want Alice to auto-accept the request
+            // and send a friend request accepted message back to Bob. We don't check that sending the
+            // friend request accepted message succeeded. Even if it doesn't, the thread's current friend
+            // request status will be set to TSThreadFriendRequestStatusFriends for Alice making it possible
+            // for Alice to send messages to Bob. When Bob receives a message, his thread's friend request status
+            // will then be set to TSThreadFriendRequestStatusFriends. If we do check for a successful send
+            // before updating Alice's thread's friend request status to TSThreadFriendRequestStatusFriends,
+            // we can end up in a deadlock where both users' threads' friend request statuses are
+            // TSThreadFriendRequestStatusRequestSent.
             [thread setFriendRequestStatus:TSThreadFriendRequestStatusFriends withTransaction:transaction];
-        } else {
+            // The two lines below are equivalent to calling [ThreadUtil enqueueAcceptFriendRequestMessageInThread:thread]
+            TSOutgoingMessage *message = [TSOutgoingMessage createEmptyOutgoingMessageInThread:thread];
+            [self.messageSenderJobQueue addMessage:message transaction:transaction];
+        } else if (!thread.isContactFriend) {
+            // Checking that the sender of the message isn't already a friend is necessary because otherwise
+            // the following situation can occur: Alice and Bob are friends. Bob loses his database and his
+            // friend request status is reset to TSThreadFriendRequestStatusNone. Bob now sends Alice a friend
+            // request. Alice's thread's friend request status is reset to
+            // TSThreadFriendRequestStatusRequestReceived.
             [thread setFriendRequestStatus:TSThreadFriendRequestStatusRequestReceived withTransaction:transaction];
             incomingMessage.isFriendRequest = YES; // Saved below
         }
     } else if (!thread.isContactFriend) {
+        // If the thread's friend request status is not TSThreadFriendRequestStatusFriends, but we're receiving a message,
+        // it must be a friend request accepted message. Declining a friend request doesn't send a message.
         [thread setFriendRequestStatus:TSThreadFriendRequestStatusFriends withTransaction:transaction];
     }
     // ========

SignalServiceKit/src/Messages/OWSMessageSender.m

@@ -1105,13 +1105,12 @@ NSString *const OWSMessageSenderRateLimitedException = @"RateLimitedException";
 
     // Update the state to show that proof of work is being calculated
     [self setIsCalculatingProofOfWorkForMessage:messageSend];
-
     // Convert the message to a Loki message and send it using the Loki messaging API
     NSDictionary *signalMessage = deviceMessages.firstObject;
     // Update the thread's friend request status if needed
     NSInteger *messageType = ((NSNumber *)signalMessage[@"type"]).integerValue;
     if (messageType == TSFriendRequestMessageType) {
-        [message.thread setFriendRequestStatus:TSThreadFriendRequestStatusPendingSend withTransaction:nil];
+        [message.thread setFriendRequestStatus:TSThreadFriendRequestStatusRequestSending withTransaction:nil];
         [message setIsFriendRequest:YES withTransaction:nil];
     }
     BOOL isPoWRequired = YES; // TODO: Base on message type
@@ -1134,10 +1133,12 @@ NSString *const OWSMessageSenderRateLimitedException = @"RateLimitedException";
                      wasSentByWebsocket:false];
         })
         .catchOn(OWSDispatch.sendingQueue, ^(NSError *error) {
-            // Update the thread's friend request status if needed
+            // Loki
+            // ========
             if (messageType == TSFriendRequestMessageType) {
                 [message.thread setFriendRequestStatus:TSThreadFriendRequestStatusNone withTransaction:nil];
             }
+            // ========
             // Handle the error
             NSUInteger statusCode = 0;
             NSData *_Nullable responseData = nil;