Initial service implementation for using a PIN code. (#1912)

* Initial service implementation for using a PIN code.

* Tweak Danger for commit size

600-800 lines is perfectly normal for our PRs, up it to 1000.

ElementX/Sources/Services/AppLock/AppLockService.swift

@@ -16,14 +16,33 @@
 
 import LocalAuthentication
 
+enum AppLockServiceError: Error {
+    /// The operation failed to access the keychain.
+    case keychainError
+    /// The PIN code was rejected because it isn't long enough, or contains invalid characters.
+    case invalidPIN
+    /// The PIN code was rejected as an insecure choice.
+    case weakPIN
+}
+
 @MainActor
 protocol AppLockServiceProtocol {
     /// The app has been configured to automatically lock with a PIN code.
     var isEnabled: Bool { get }
-    /// The app can additionally be unlocked using FaceID or TouchID.
-    var supportsBiometrics: Bool { get }
-    /// The app should be unlocked with a PIN code/biometrics before being presented.
-    var needsUnlock: Bool { get }
+    /// The type of biometric authentication supported by the device.
+    var biometryType: LABiometryType { get }
+    /// Whether or not the user has enabled unlock via TouchID, FaceID or (possibly) OpticID.
+    var biometricUnlockEnabled: Bool { get set }
+    
+    /// Sets the user's PIN code used to unlock the app.
+    func setupPINCode(_ pinCode: String) -> Result<Void, AppLockServiceError>
+    /// Disables the App Lock feature, removing the user's stored PIN code.
+    func disable()
+    
+    /// Informs the service that the app has entered the background.
+    func applicationDidEnterBackground()
+    /// Decides whether the app should be unlocked with a PIN code/biometrics on foregrounding.
+    func computeNeedsUnlock(willEnterForegroundAt date: Date) -> Bool
     
     /// Attempt to unlock the app with the supplied PIN code.
     func unlock(with pinCode: String) -> Bool
@@ -31,25 +50,80 @@ protocol AppLockServiceProtocol {
     func unlockWithBiometrics() -> Bool
 }
 
+/// The service responsible for locking and unlocking the app.
 class AppLockService: AppLockServiceProtocol {
     private let keychainController: KeychainControllerProtocol
     private let appSettings: AppSettings
+    private let context = LAContext()
     
-    var isEnabled: Bool { appSettings.appLockFlowEnabled }
-    var supportsBiometrics: Bool { true }
-    var needsUnlock: Bool { true }
+    private let timer: AppLockTimer
+    
+    var isEnabled: Bool {
+        do {
+            guard appSettings.appLockFlowEnabled else { return false }
+            return try keychainController.containsPINCode()
+        } catch {
+            MXLog.error("Keychain access error: \(error)")
+            MXLog.error("Locking the app.")
+            return true
+        }
+    }
+    
+    var biometryType: LABiometryType { context.biometryType }
+    var biometricUnlockEnabled = false // Needs to be stored, not sure if in the keychain or defaults yet.
     
     init(keychainController: KeychainControllerProtocol, appSettings: AppSettings) {
         self.keychainController = keychainController
         self.appSettings = appSettings
+        timer = AppLockTimer(gracePeriod: appSettings.appLockGracePeriod)
+    }
+    
+    func setupPINCode(_ pinCode: String) -> Result<Void, AppLockServiceError> {
+        guard validate(pinCode) else { return .failure(.invalidPIN) }
+        guard !appSettings.appLockPINCodeBlockList.contains(pinCode) else { return .failure(.weakPIN) }
+        
+        do {
+            try keychainController.setPINCode(pinCode)
+            return .success(())
+        } catch {
+            MXLog.error("Keychain access error: \(error)")
+            return .failure(.keychainError)
+        }
+    }
+    
+    func disable() {
+        biometricUnlockEnabled = false
+        keychainController.removePINCode()
+    }
+    
+    func applicationDidEnterBackground() {
+        timer.applicationDidEnterBackground()
+    }
+    
+    func computeNeedsUnlock(willEnterForegroundAt date: Date) -> Bool {
+        timer.computeLockState(willEnterForegroundAt: date)
     }
     
     func unlock(with pinCode: String) -> Bool {
-        true
+        guard pinCode == keychainController.pinCode() else { return false }
+        return completeUnlock()
     }
     
     func unlockWithBiometrics() -> Bool {
-        guard supportsBiometrics else { return false }
+        guard biometryType != .none, biometricUnlockEnabled else { return false }
+        return completeUnlock()
+    }
+    
+    // MARK: - Private
+    
+    /// Ensures that a provided PIN code is long enough and only contains digits.
+    private func validate(_ pinCode: String) -> Bool {
+        pinCode.count == 4 && pinCode.allSatisfy(\.isNumber)
+    }
+    
+    /// Shared logic for completing an unlock via a PIN or biometry.
+    private func completeUnlock() -> Bool {
+        timer.registerUnlock()
         return true
     }
 }