feat(mobile): hash assets in isolate (#18924)

mobile/ios/Runner/Sync/MessagesImpl.swift

@@ -1,4 +1,5 @@
 import Photos
+import CryptoKit
 
 struct AssetWrapper: Hashable, Equatable {
   let asset: PlatformAsset
@@ -34,6 +35,8 @@ class NativeSyncApiImpl: NativeSyncApi {
   private let changeTokenKey = "immich:changeToken"
   private let albumTypes: [PHAssetCollectionType] = [.album, .smartAlbum]
   
+  private let hashBufferSize = 2 * 1024 * 1024
+  
   init(with defaults: UserDefaults = .standard) {
     self.defaults = defaults
   }
@@ -243,4 +246,24 @@ class NativeSyncApiImpl: NativeSyncApi {
     }
     return assets
   }
+  
+  func hashPaths(paths: [String]) throws -> [FlutterStandardTypedData?] {
+      return paths.map { path in
+          guard let file = FileHandle(forReadingAtPath: path) else {
+              print("Cannot open file: \(path)")
+              return nil
+          }
+          
+          var hasher = Insecure.SHA1()
+          while autoreleasepool(invoking: {
+              let chunk = file.readData(ofLength: hashBufferSize)
+              guard !chunk.isEmpty else { return false }
+              hasher.update(data: chunk)
+              return true
+          }) { }
+          
+          let digest = hasher.finalize()
+          return FlutterStandardTypedData(bytes: Data(digest))
+      }
+  }
 }