Implement deletion of non-existent conversations

app/src/main/java/net/buzzert/kordophonedroid/ui/conversationlist/ConversationListViewModel.kt

@@ -26,7 +26,7 @@ class ConversationListViewModel @Inject constructor(
     init {
         // TODO: Is this the best place to put these?
         // TODO: Need error handling (exceptions thrown below)
-        
+
         viewModelScope.launch {
             repository.synchronize()
         }

backend/src/main/java/net/buzzert/kordophone/backend/db/CachedChatDatabase.kt

@@ -85,6 +85,15 @@ class CachedChatDatabase (private val realmConfig: RealmConfiguration) {
         }
     }
 
+    fun deleteConversations(conversations: List<ModelConversation>) = realm.writeBlocking {
+        conversations.forEach { inConversation ->
+            val conversation = getConversationByGuid(inConversation.guid)
+            findLatest(conversation)?.let {
+                delete(it)
+            }
+        }
+    }
+
     fun fetchConversations(): List<ModelConversation> {
         val items = realm.query(Conversation::class).find()
         return items.map { it.toConversation() }

backend/src/main/java/net/buzzert/kordophone/backend/server/ChatRepository.kt

@@ -121,10 +121,11 @@ class ChatRepository(
         Log.d(REPO_LOG, "Synchronizing conversations")
 
         // Sync conversations
-        val conversations = fetchConversations()
-        database.writeConversations(conversations)
+        val serverConversations = fetchConversations()
+        val deletedConversations = conversations.minus(serverConversations)
 
-        // TODO: Delete non-existent conversations.
+        database.deleteConversations(deletedConversations)
+        database.writeConversations(serverConversations)
 
         // Sync top N number of conversations' message content
         Log.d(REPO_LOG, "Synchronizing messages")