Fix duplicate request bug

SignalServiceKit/src/Loki/API/LokiDotNetAPI.swift

@@ -3,6 +3,7 @@ import SignalMetadataKit
 
 /// Base class for `LokiFileServerAPI` and `LokiPublicChatAPI`.
 public class LokiDotNetAPI : NSObject {
+    public static var getAuthTokenPromises: [String:Promise<String>] = [:]
     
     // MARK: Convenience
     internal static let storage = OWSPrimaryStorage.shared()
@@ -42,6 +43,23 @@ public class LokiDotNetAPI : NSObject {
         }
     }
     
+    internal static func getAuthToken(for server: String, in transaction: YapDatabaseReadWriteTransaction? = nil) -> Promise<String> {
+        if let promise = getAuthTokenPromises[server] { return promise }
+        if let token = getAuthTokenFromDatabase(for: server, in: transaction) {
+            return Promise.value(token)
+        } else {
+            let promise = requestNewAuthToken(for: server).then(on: DispatchQueue.global()) { submitAuthToken($0, for: server) }.map { token -> String in
+                setAuthToken(for: server, to: token, in: transaction)
+                return token
+            }
+            promise.done { _ in
+                getAuthTokenPromises[server] = nil
+            }
+            getAuthTokenPromises[server] = promise
+            return promise
+        }
+    }
+
     private static func setAuthToken(for server: String, to newValue: String, in transaction: YapDatabaseReadWriteTransaction? = nil) {
         func setAuthTokenInternal(in transaction: YapDatabaseReadWriteTransaction) {
             transaction.setObject(newValue, forKey: server, inCollection: authTokenCollection)
@@ -160,18 +178,6 @@ public class LokiDotNetAPI : NSObject {
         }
     }
 
-    // MARK: Internal API
-    internal static func getAuthToken(for server: String, in transaction: YapDatabaseReadWriteTransaction? = nil) -> Promise<String> {
-        if let token = getAuthTokenFromDatabase(for: server, in: transaction) {
-            return Promise.value(token)
-        } else {
-            return requestNewAuthToken(for: server).then(on: DispatchQueue.global()) { submitAuthToken($0, for: server) }.map { token -> String in
-                setAuthToken(for: server, to: token, in: transaction)
-                return token
-            }
-        }
-    }
-
     // MARK: Private API
     private static func requestNewAuthToken(for server: String) -> Promise<String> {
         print("[Loki] Requesting auth token for server: \(server).")