wip: add platform channels

mobile-v2/ios/Runner/AppDelegate.swift

@@ -8,6 +8,11 @@ import Flutter
     didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?
   ) -> Bool {
     GeneratedPluginRegistrant.register(with: self)
+
+    // Register piegon handler
+    let controller: FlutterViewController = window?.rootViewController as! FlutterViewController
+    ImmichHostServiceSetup.setUp(binaryMessenger: controller.binaryMessenger, api: ImmichHostServiceImpl())
+    
     return super.application(application, didFinishLaunchingWithOptions: launchOptions)
   }
 }

mobile-v2/ios/Runner/Platform/MessagesImpl.swift

@@ -0,0 +1,39 @@
+import CryptoKit
+
+class ImmichHostServiceImpl: ImmichHostService {
+    func digestFiles(paths: [String], completion: @escaping (Result<[FlutterStandardTypedData?]?, Error>) -> Void) {
+        let bufsize = 2 * 1024 * 1024
+        // Private error to throw if file cannot be read
+        enum DigestError: String, LocalizedError {
+            case NoFileHandle = "Cannot Open File Handle"
+
+            public var errorDescription: String? { self.rawValue }
+        }
+        
+        // Compute hash in background thread
+        DispatchQueue.global(qos: .background).async {
+            var hashes: [FlutterStandardTypedData?] = Array(repeating: nil, count: paths.count)
+            for i in (0 ..< paths.count) {
+                do {
+                    guard let file = FileHandle(forReadingAtPath: paths[i]) else { throw DigestError.NoFileHandle }
+                    var hasher = Insecure.SHA1.init();
+                    while autoreleasepool(invoking: {
+                        let chunk = file.readData(ofLength: bufsize)
+                        guard !chunk.isEmpty else { return false } // EOF
+                        hasher.update(data: chunk)
+                        return true // continue
+                    }) { }
+                    let digest = hasher.finalize()
+                    hashes[i] = FlutterStandardTypedData(bytes: Data(Array(digest.makeIterator())))
+                } catch {
+                    print("Cannot calculate the digest of the file \(paths[i]) due to \(error.localizedDescription)")
+                }
+            }
+            
+            // Return result in main thread
+            DispatchQueue.main.async {
+                completion(.success(Array(hashes)))
+            }
+        }
+    }
+}