Persist Authentication in Keychain

Mastodon/Supporting Files/AppDelegate.swift

@@ -18,6 +18,7 @@ class AppDelegate: UIResponder, UIApplicationDelegate {
     let appContext = AppContext()
 
     func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?) -> Bool {
+        AuthenticationServiceProvider.shared.restore()
         
         AppSecret.default.register()
 

MastodonSDK/Sources/MastodonCore/AuthenticationServiceProvider.swift

@@ -4,13 +4,20 @@ import Foundation
 import Combine
 import CoreDataStack
 import MastodonSDK
+import KeychainAccess
+import MastodonCommon
 
 public class AuthenticationServiceProvider: ObservableObject {
     public static let shared = AuthenticationServiceProvider()
+    private static let keychain = Keychain(service: "org.joinmastodon.app.authentications", accessGroup: AppName.groupID)
 
     private init() {}
     
-    @Published public var authentications: [MastodonAuthentication] = []
+    @Published public var authentications: [MastodonAuthentication] = [] {
+        didSet {
+            persist() // todo: Is this too heavy and too often here???
+        }
+    }
         
     func update(instance: Instance, where domain: String) {
         authentications = authentications.map { authentication in
@@ -46,4 +53,23 @@ public extension AuthenticationServiceProvider {
     func sortByActivation() { // fixme: why do we need this?
         authentications = authentications.sorted(by: { $0.activedAt > $1.activedAt })
     }
+        
+    func restore() {
+        authentications = Self.keychain.allKeys().compactMap {
+            guard
+                let encoded = Self.keychain[$0],
+                    let data = Data(base64Encoded: encoded)
+            else { return nil }
+            return try? JSONDecoder().decode(MastodonAuthentication.self, from: data)
+        }
+    }
+}
+
+// MARK: - Private
+private extension AuthenticationServiceProvider {
+    func persist() {
+        for authentication in authentications {
+            Self.keychain[authentication.persistenceIdentifier] = try? JSONEncoder().encode(authentication).base64EncodedString()
+        }
+    }
 }

MastodonSDK/Sources/MastodonCore/MastodonAuthentication.swift

@@ -23,6 +23,10 @@ public struct MastodonAuthentication: Codable, Hashable {
     public private(set) var userID: String
     public private(set) var instanceObjectIdURI: URL?
     
+    internal var persistenceIdentifier: String {
+        "\(username)@\(domain)"
+    }
+    
     public static func createFrom(
         domain: String,
         userID: String,
@@ -34,7 +38,7 @@ public struct MastodonAuthentication: Codable, Hashable {
     ) -> Self {
         let now = Date()
         return MastodonAuthentication(
-            identifier: .init(), // fixme
+            identifier: .init(),
             domain: domain,
             username: username,
             appAccessToken: appAccessToken,