#40: Add UserSessionStoreProtocol.

Only log out of the specific account.
Add tests for the keychain controller.
Expand test coverage.
PR comments

ElementX/Sources/Services/UserSessionStore/KeychainController.swift

@@ -20,7 +20,7 @@ class KeychainController: KeychainControllerProtocol {
         do {
             try keychain.set(accessToken, key: username)
         } catch {
-            MXLog.error("Failed storing user restore token with error: \(error)")
+            MXLog.error("Failed storing user access token with error: \(error)")
         }
     }
     
@@ -28,7 +28,7 @@ class KeychainController: KeychainControllerProtocol {
         do {
             return try keychain.get(username)
         } catch {
-            MXLog.error("Failed retrieving user restore token")
+            MXLog.error("Failed retrieving user access token")
             return nil
         }
     }
@@ -43,6 +43,14 @@ class KeychainController: KeychainControllerProtocol {
         }
     }
     
+    func removeAccessTokenForUsername(_ username: String) {
+        do {
+            try keychain.remove(username)
+        } catch {
+            MXLog.error("Failed removing access token with error: \(error)")
+        }
+    }
+    
     func removeAllAccessTokens() {
         do {
             try keychain.removeAll()

ElementX/Sources/Services/UserSessionStore/KeychainControllerProtocol.swift

@@ -12,5 +12,6 @@ protocol KeychainControllerProtocol {
     func setAccessToken(_ accessToken: String, forUsername username: String)
     func accessTokenForUsername(_ username: String) -> String?
     func accessTokens() -> [(username: String, accessToken: String)]
+    func removeAccessTokenForUsername(_ username: String)
     func removeAllAccessTokens()
 }

ElementX/Sources/Services/UserSessionStore/UserSessionStore.swift

@@ -18,14 +18,7 @@ import Foundation
 import MatrixRustSDK
 import Kingfisher
 
-enum UserSessionStoreError: Error {
-    case missingCredentials
-    case failedRestoringLogin
-    case failedSettingUpSession
-}
-
-@MainActor
-class UserSessionStore {
+class UserSessionStore: UserSessionStoreProtocol {
     
     private let keychainController: KeychainControllerProtocol
     
@@ -70,8 +63,9 @@ class UserSessionStore {
     }
     
     func logout(userSession: UserSessionProtocol) {
-        keychainController.removeAllAccessTokens()
-        deleteBaseDirectory(for: userSession.clientProxy.userIdentifier)
+        let username = userSession.clientProxy.userIdentifier
+        keychainController.removeAccessTokenForUsername(username)
+        deleteBaseDirectory(for: username)
     }
     
     private func restorePreviousLogin(_ usernameTokenTuple: (username: String, accessToken: String)) async -> Result<ClientProxyProtocol, UserSessionStoreError> {

ElementX/Sources/Services/UserSessionStore/UserSessionStoreProtocol.swift

@@ -0,0 +1,42 @@
+//
+// Copyright 2022 New Vector Ltd
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+
+import Foundation
+import MatrixRustSDK
+
+enum UserSessionStoreError: Error {
+    case missingCredentials
+    case failedRestoringLogin
+    case failedSettingUpSession
+}
+
+@MainActor
+protocol UserSessionStoreProtocol {
+    /// Whether or not there are sessions in the store.
+    var hasSessions: Bool { get }
+    
+    /// Restores an existing user session.
+    func restoreUserSession() async -> Result<UserSession, UserSessionStoreError>
+    
+    /// Creates a user session for a new client from the SDK.
+    func userSession(for client: Client) async -> Result<UserSession, UserSessionStoreError>
+    
+    /// Logs out of the specified session.
+    func logout(userSession: UserSessionProtocol)
+    
+    /// Returns the location to store user data for a particular username.
+    func baseDirectoryPath(for username: String) -> String
+}