presence: fix possible crash when subscribe

This patch adds a queue to protect access to contact presence subscriptions.

Change-Id: I6c5cd6c0dc54c0536729d4bbcee1bae6c4a82045

Ring/Ring/Calls/Conference/ContactPickerSection.swift

@@ -30,7 +30,7 @@ struct Contact {
 
     lazy var presenceStatus: BehaviorRelay<Bool>?  = {
          self.presenceService
-            .contactPresence[self.hash]
+            .getSubscriptionsForContact(contactId: self.hash)
     }()
 
     lazy var firstLine: String! = {

Ring/Ring/Features/Conversations/Conversation/ConversationViewModel.swift

@@ -617,7 +617,7 @@ extension ConversationViewModel {
 
     private func subscribePresenceServiceContactPresence() {
         // subscribe to presence updates for the conversation's associated contact
-        if let contactPresence = self.presenceService.contactPresence[self.conversation.value.hash] {
+        if let contactPresence = self.presenceService.getSubscriptionsForContact(contactId: self.conversation.value.hash) {
             self.contactPresence = contactPresence
         } else {
             self.contactPresence.accept(false)
@@ -637,7 +637,7 @@ extension ConversationViewModel {
 
     private func subscribePresence() {
         if let contactPresence = self.presenceService
-            .contactPresence[self.conversation.value.hash] {
+            .getSubscriptionsForContact(contactId: self.conversation.value.hash) {
             self.contactPresence = contactPresence
         } else {
             self.contactPresence.accept(false)

Ring/Ring/Services/PresenceService.swift

@@ -26,7 +26,8 @@ class PresenceService {
 
     private let presenceAdapter: PresenceAdapter
     private let log = SwiftyBeaver.self
-    var contactPresence: [String: BehaviorRelay<Bool>]
+    private var contactPresence: [String: BehaviorRelay<Bool>]
+    private let presenceQueue = DispatchQueue(label: "com.presenceQueue", qos: .background) // used to protect access to contactPresence[]
 
     private let responseStream = PublishSubject<ServiceEvent>()
     var sharedResponseStream: Observable<ServiceEvent>
@@ -41,56 +42,68 @@ class PresenceService {
         PresenceAdapter.delegate = self
     }
 
+    func getSubscriptionsForContact(contactId: String) -> BehaviorRelay<Bool>? {
+        var value: BehaviorRelay<Bool>?
+        presenceQueue.sync {[weak self] in
+            value = self?.contactPresence[contactId]
+        }
+        return value
+    }
+
     func subscribeBuddies(withAccount accountId: String,
                           withContacts contacts: [ContactModel],
                           subscribe: Bool) {
-        DispatchQueue.global(qos: .background).async { [weak self] in
-            guard let self = self else { return }
         for contact in contacts where !contact.banned {
             self.subscribeBuddy(withAccountId: accountId,
                                 withUri: contact.hash,
                                 withFlag: subscribe)
         }
     }
-    }
 
     func subscribeBuddy(withAccountId accountId: String,
                         withUri uri: String,
                         withFlag flag: Bool) {
-        if flag && contactPresence[uri] != nil {
+        presenceQueue.async { [weak self] in
+            guard let self = self else { return }
+            if flag && self.contactPresence[uri] != nil {
                 // already subscribed
                 return
             }
-        presenceAdapter.subscribeBuddy(withURI: uri, withAccountId: accountId, withFlag: flag)
+            self.presenceAdapter.subscribeBuddy(withURI: uri, withAccountId: accountId, withFlag: flag)
             if !flag {
-            contactPresence[uri] = nil
+                self.contactPresence[uri] = nil
                 return
             }
-        if let presenceForContact = contactPresence[uri] {
+            if let presenceForContact = self.contactPresence[uri] {
                 presenceForContact.accept(false)
                 return
             }
             let observableValue = BehaviorRelay<Bool>(value: false)
-        contactPresence[uri] = observableValue
+            self.contactPresence[uri] = observableValue
+            DispatchQueue.global(qos: .background).async {
                 var event = ServiceEvent(withEventType: .presenseSubscribed)
                 event.addEventInput(.accountId, value: accountId)
                 event.addEventInput(.uri, value: uri)
                 self.responseStream.onNext(event)
             }
         }
+    }
+}
 
 extension PresenceService: PresenceAdapterDelegate {
     func newBuddyNotification(withAccountId accountId: String,
                               withUri uri: String,
                               withStatus status: Int,
                               withLineStatus lineStatus: String) {
+        presenceQueue.async {[weak self] in
+            guard let self = self else { return }
             let value = status > 0 ? true : false
-        if let presenceForContact = contactPresence[uri] {
+            if let presenceForContact = self.contactPresence[uri] {
                 presenceForContact.accept(value)
                 return
             }
             let observableValue = BehaviorRelay<Bool>(value: value)
-        contactPresence[uri] = observableValue
-        log.debug("newBuddyNotification: uri=\(uri), status=\(status)")
+            self.contactPresence[uri] = observableValue
+        }
     }
 }