Rewrite AppCheckCore in Swift (#111)

Signed-off-by: Nick Cooke <36927374+ncooke3@users.noreply.github.com>
Co-authored-by: Nick Cooke <36927374+ncooke3@users.noreply.github.com>
Co-authored-by: Nick Cooke <nickcooke@google.com>

AppCheckCore/Sources/DeviceCheckProvider/AppCheckCoreDeviceCheckProvider.swift

@@ -0,0 +1,116 @@
+// Copyright 2026 Google LLC
+//
+// 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
+#if canImport(DeviceCheck)
+  import DeviceCheck
+#endif
+
+@available(iOS 11.0, macOS 10.15, macCatalyst 13.0, tvOS 11.0, watchOS 9.0, *)
+@objc(GACDeviceCheckProvider)
+public class AppCheckCoreDeviceCheckProvider: NSObject, AppCheckCoreProvider {
+  private let apiService: AppCheckCoreDeviceCheckAPIServiceProtocol
+  private let deviceTokenGenerator: AppCheckCoreDeviceCheckTokenGenerator
+  private let backoffWrapper: AppCheckCoreBackoffWrapperProtocol
+
+  /// - Parameter requestHooks: Hooks invoked on each outgoing request. From Swift, pass
+  ///   `[AppCheckCoreAPIRequestHook]`. From Objective-C, pass an `NSArray` of blocks with the
+  ///   signature `void (^)(NSMutableURLRequest *)`; the signature is not checked at compile
+  ///   time and a mismatch will crash when the hook is invoked.
+  ///
+  ///   Typed `[Any]?` rather than `[AppCheckCoreAPIRequestHook]?` deliberately: Swift cannot
+  ///   bridge an `NSArray` into a Swift `Array` whose element is a function type, so the typed
+  ///   signature traps at runtime for any non-nil array passed from Objective-C. Do not
+  ///   "simplify" this type — see PR #111.
+  @objc(initWithServiceName:resourceName:APIKey:requestHooks:)
+  public init(serviceName: String, resourceName: String, apiKey: String,
+              requestHooks: [Any]?) {
+    let session = URLSession(configuration: .ephemeral)
+    let coreAPIService = AppCheckCoreAPIService(
+      urlSession: session,
+      baseURL: nil,
+      apiKey: apiKey,
+      requestHooks: requestHooks
+    )
+    let deviceCheckAPIService = AppCheckCoreDeviceCheckAPIService(
+      apiService: coreAPIService,
+      resourceName: resourceName
+    )
+    apiService = deviceCheckAPIService
+    deviceTokenGenerator = DCDevice.current
+    backoffWrapper = AppCheckCoreBackoffWrapper()
+    super.init()
+  }
+
+  init(apiService: AppCheckCoreDeviceCheckAPIServiceProtocol,
+       deviceTokenGenerator: AppCheckCoreDeviceCheckTokenGenerator,
+       backoffWrapper: AppCheckCoreBackoffWrapperProtocol) {
+    self.apiService = apiService
+    self.deviceTokenGenerator = deviceTokenGenerator
+    self.backoffWrapper = backoffWrapper
+    super.init()
+  }
+
+  // MARK: - AppCheckCoreProvider
+
+  public func getToken() async throws -> AppCheckCoreToken {
+    return try await getToken(limitedUse: false)
+  }
+
+  public func getLimitedUseToken() async throws -> AppCheckCoreToken {
+    return try await getToken(limitedUse: true)
+  }
+
+  public func getToken(completion handler: @escaping (AppCheckCoreToken?, Error?) -> Void) {
+    Task {
+      do {
+        let token = try await getToken(limitedUse: false)
+        AppCheckCore.deliverOnMainQueue(token, error: nil as Error?, to: handler)
+      } catch {
+        AppCheckCore.deliverOnMainQueue(nil, error: error, to: handler)
+      }
+    }
+  }
+
+  public func getLimitedUseToken(completion handler: @escaping (AppCheckCoreToken?, Error?)
+    -> Void) {
+    Task {
+      do {
+        let token = try await getToken(limitedUse: true)
+        AppCheckCore.deliverOnMainQueue(token, error: nil as Error?, to: handler)
+      } catch {
+        AppCheckCore.deliverOnMainQueue(nil, error: error, to: handler)
+      }
+    }
+  }
+
+  // MARK: - Internal
+
+  private func getToken(limitedUse: Bool) async throws -> AppCheckCoreToken {
+    return try await backoffWrapper.applyBackoffToOperation({ [weak self] in
+      guard let self = self else {
+        throw AppCheckCoreErrorUtil.error(withFailureReason: "Self is nil")
+      }
+      return try await self.getTokenPromise(limitedUse: limitedUse)
+    }, errorHandler: backoffWrapper.defaultAppCheckProviderErrorHandler())
+  }
+
+  private func getTokenPromise(limitedUse: Bool) async throws -> AppCheckCoreToken {
+    guard deviceTokenGenerator.isSupported else {
+      throw AppCheckCoreErrorUtil.unsupportedAttestationProvider("DeviceCheckProvider")
+    }
+    let deviceToken = try await deviceTokenGenerator.generateTokenAsync()
+    return try await apiService.appCheckToken(deviceToken: deviceToken, limitedUse: limitedUse)
+  }
+}