From 0be05b41eb83e8fd979c3626c445a3a00a8f5af7 Mon Sep 17 00:00:00 2001
From: Nora Trapp <nora@signal.org>
Date: Mon, 8 Jun 2020 18:32:16 -0700
Subject: [PATCH] Keep track of who added us to a group

---
 .../ViewModels/ThreadViewModel.swift          |  2 +-
 .../src/groups/GroupManager.swift             | 21 +++++++++++++++++++
 2 files changed, 22 insertions(+), 1 deletion(-)

diff --git a/SignalMessaging/ViewModels/ThreadViewModel.swift b/SignalMessaging/ViewModels/ThreadViewModel.swift
index 33a9d4c240..805fa9186e 100644
--- a/SignalMessaging/ViewModels/ThreadViewModel.swift
+++ b/SignalMessaging/ViewModels/ThreadViewModel.swift
@@ -56,7 +56,7 @@ public class ThreadViewModel: NSObject {
         self.hasPendingMessageRequest = thread.hasPendingMessageRequest(transaction: transaction.unwrapGrdbRead)
 
         if let groupThread = thread as? TSGroupThread, let addedByAddress = groupThread.groupModel.addedByAddress {
-            self.addedToGroupByName = Environment.shared.contactsManager.displayName(for: addedByAddress, transaction: transaction)
+            self.addedToGroupByName = Environment.shared.contactsManager.shortDisplayName(for: addedByAddress, transaction: transaction)
         } else {
             self.addedToGroupByName = nil
         }
diff --git a/SignalServiceKit/src/groups/GroupManager.swift b/SignalServiceKit/src/groups/GroupManager.swift
index b3bc2280c8..23e2287505 100644
--- a/SignalServiceKit/src/groups/GroupManager.swift
+++ b/SignalServiceKit/src/groups/GroupManager.swift
@@ -339,6 +339,9 @@ public class GroupManager: NSObject {
                 return createdGroupModel
             }
         }.then(on: .global()) { (groupModel: TSGroupModel) -> Promise<TSGroupThread> in
+            // We're creating this thread, we added ourselves
+            groupModel.addedByAddress = self.tsAccountManager.localAddress
+
             let thread = databaseStorage.write { (transaction: SDSAnyWriteTransaction) -> TSGroupThread in
                 return self.insertGroupThreadInDatabaseAndCreateInfoMessage(groupModel: groupModel,
                                                                             disappearingMessageToken: disappearingMessageToken,
@@ -1083,6 +1086,9 @@ public class GroupManager: NSObject {
             builder.groupMembership = newGroupMembership
             let newGroupModel = try builder.build(transaction: transaction)
 
+            // We're leaving, so clear out who added us. If we're re-added it may change.
+            newGroupModel.addedByAddress = nil
+
             let groupUpdateSourceAddress = localAddress
             let result = try self.updateExistingGroupThreadInDatabaseAndCreateInfoMessage(newGroupModel: newGroupModel,
                                                                                           newDisappearingMessageToken: nil,
@@ -1550,6 +1556,13 @@ public class GroupManager: NSObject {
             guard canInsert else {
                 throw OWSAssertionError("Missing groupThread.")
             }
+
+            // This thread didn't previously exist, so if we're a member we
+            // have to assume we were just added.
+            if let localAddress = tsAccountManager.localAddress, newGroupModel.groupMembers.contains(localAddress) {
+                newGroupModel.addedByAddress = groupUpdateSourceAddress
+            }
+
             let thread = insertGroupThreadInDatabaseAndCreateInfoMessage(groupModel: newGroupModel,
                                                                          disappearingMessageToken: newDisappearingMessageToken,
                                                                          groupUpdateSourceAddress: groupUpdateSourceAddress,
@@ -1630,6 +1643,14 @@ public class GroupManager: NSObject {
 
             let hasUserFacingChange = !oldGroupModel.isEqual(to: newGroupModel, ignoreRevision: true)
 
+            // If we weren't previously a member and are now a member, assume whoever
+            // triggered this update added us to the group.
+            if let localAddress = tsAccountManager.localAddress,
+                !oldGroupModel.groupMembers.contains(localAddress),
+                newGroupModel.groupMembers.contains(localAddress) {
+                newGroupModel.addedByAddress = groupUpdateSourceAddress
+            }
+
             groupThread.update(with: newGroupModel, transaction: transaction)
 
             let action: UpsertGroupResult.Action = (hasUserFacingChange