iOS Share Extension: pick the destination inside the share sheet

SwiftUI folder picker in the extension (WebDAV PROPFIND), account shared via
a Keychain group, upload on a background session that outlives the extension
and is finished by the app. The inbox + notification hand-off remains as the
fallback (no account / 'choose later'). Shared code moves to ios/Shared.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

ios/Runner/Native/NativeServices.swift

@@ -75,6 +75,35 @@ enum NativeServices {
     }
     TransferManager.shared.reconnect()
     registerShare(messenger: messenger)
+    registerShareAccount(messenger: messenger)
+  }
+
+  // MARK: - Account for the Share Extension
+
+  /// `share_account`: Dart tells native which account is active so the Share
+  /// Extension - a separate process with no Flutter engine - can list folders
+  /// and upload as it. Stored in the shared Keychain group.
+  private static func registerShareAccount(messenger: FlutterBinaryMessenger) {
+    FlutterMethodChannel(name: "dev.ayushya.noo/share_account", binaryMessenger: messenger)
+      .setMethodCallHandler { call, result in
+        switch call.method {
+        case "setAccount":
+          handle(call, result) { args in
+            try SharedAccountStore.save(
+              SharedAccount(
+                serverUrl: try string(args, "serverUrl"),
+                username: try string(args, "username"),
+                authHeader: try string(args, "authHeader"),
+                displayName: (args["displayName"] as? String) ?? ""
+              ))
+          }
+        case "clearAccount":
+          SharedAccountStore.clear()
+          result(nil)
+        default:
+          result(FlutterMethodNotImplemented)
+        }
+      }
   }
 
   // MARK: - Share Extension inbox

ios/Runner/Native/TransferManager.swift

@@ -1,43 +1,11 @@
 import Foundation
 import UserNotifications
 
-/// What a background upload/download task is, stored in the task's
-/// `taskDescription` so it's still known if the app was relaunched by the
-/// system to deliver the result.
-struct TransferTaskInfo: Codable {
-  enum Kind: String, Codable { case upload, download }
-
-  let kind: Kind
-  let batch: String
-  let name: String
-  let remoteFolder: String?
-  let stagedPath: String?
-}
-
-/// Running totals for one "upload these 3 files" / "download these 2 files"
-/// request, persisted so the one summary notification (and the Dart-side
-/// "folder changed" event) fires exactly once, on the last file, even across
-/// an app relaunch.
-struct TransferBatch: Codable {
-  let kind: TransferTaskInfo.Kind
-  let remoteFolder: String?
-  let total: Int
-  var succeeded: Int
-  var failed: Int
-
-  var finished: Int { succeeded + failed }
-}
-
 struct UploadFile {
   let uri: String
   let name: String
 }
 
-struct TransferError: LocalizedError {
-  let message: String
-  var errorDescription: String? { message }
-}
-
 /// Uploads and downloads on a background `URLSession`, so a transfer keeps
 /// going - and finishes - after the app is suspended or closed. The iOS
 /// counterpart of Android's `ShareUploadService`/`DownloadService`
@@ -61,9 +29,6 @@ final class TransferManager: NSObject {
   /// session has delivered every pending event.
   var backgroundCompletionHandler: (() -> Void)?
 
-  private let defaults = UserDefaults.standard
-  private let lock = NSLock()
-
   private lazy var session: URLSession = {
     let config = URLSessionConfiguration.background(withIdentifier: Self.sessionIdentifier)
     config.sessionSendsLaunchEvents = true
@@ -72,10 +37,17 @@ final class TransferManager: NSObject {
     return URLSession(configuration: config, delegate: self, delegateQueue: nil)
   }()
 
-  /// Touch the session at launch so a system relaunch for finished
+  /// The session the Share Extension's uploads run on (see `ShareUpload`).
+  /// The extension is gone by the time they finish, so the app recreates it -
+  /// same identifier and shared container - to receive the results.
+  private lazy var shareSession = URLSession(
+    configuration: ShareUpload.configuration(), delegate: self, delegateQueue: nil)
+
+  /// Touch both sessions at launch so a system relaunch for finished
   /// background transfers reconnects to them.
   func reconnect() {
     _ = session
+    _ = shareSession
   }
 
   // MARK: - Starting transfers
@@ -130,7 +102,7 @@ final class TransferManager: NSObject {
       )
       tasks.append(task)
     }
-    saveBatch(
+    TransferBatchStore.save(
       TransferBatch(kind: .upload, remoteFolder: remoteFolder, total: tasks.count, succeeded: 0, failed: 0),
       id: batch
     )
@@ -158,7 +130,7 @@ final class TransferManager: NSObject {
       )
       tasks.append(task)
     }
-    saveBatch(
+    TransferBatchStore.save(
       TransferBatch(kind: .download, remoteFolder: nil, total: tasks.count, succeeded: 0, failed: 0),
       id: batch
     )
@@ -195,30 +167,9 @@ final class TransferManager: NSObject {
       .flatMap { try? JSONDecoder().decode(TransferTaskInfo.self, from: $0) }
   }
 
-  private func key(_ id: String) -> String { "transfer.batch.\(id)" }
-
-  private func saveBatch(_ batch: TransferBatch, id: String) {
-    lock.lock()
-    defer { lock.unlock() }
-    if let data = try? JSONEncoder().encode(batch) { defaults.set(data, forKey: key(id)) }
-  }
-
   /// Counts one file's outcome; fires the batch summary when it was the last.
   private func record(_ info: TransferTaskInfo, success: Bool) {
-    lock.lock()
-    let storageKey = key(info.batch)
-    var batch =
-      (defaults.data(forKey: storageKey).flatMap { try? JSONDecoder().decode(TransferBatch.self, from: $0) })
-      ?? TransferBatch(kind: info.kind, remoteFolder: info.remoteFolder, total: 1, succeeded: 0, failed: 0)
-    if success { batch.succeeded += 1 } else { batch.failed += 1 }
-    let done = batch.finished >= batch.total
-    if done {
-      defaults.removeObject(forKey: storageKey)
-    } else if let data = try? JSONEncoder().encode(batch) {
-      defaults.set(data, forKey: storageKey)
-    }
-    lock.unlock()
-    if done { finish(batch) }
+    if let batch = TransferBatchStore.record(info, success: success) { finish(batch) }
   }
 
   private func finish(_ batch: TransferBatch) {

ios/Runner/Native/WebDAV.swift

@@ -1,53 +0,0 @@
-import Foundation
-
-/// URL building for a Nextcloud account's WebDAV files root. Pure functions
-/// (no networking), so they're unit-tested in `RunnerTests`.
-enum WebDAV {
-  /// `urlPathAllowed` minus "/", so a file name containing a slash-like
-  /// character can't introduce an extra path segment.
-  private static let segmentAllowed: CharacterSet = {
-    var set = CharacterSet.urlPathAllowed
-    set.remove(charactersIn: "/")
-    return set
-  }()
-
-  static func encodeSegment(_ segment: String) -> String {
-    segment.addingPercentEncoding(withAllowedCharacters: segmentAllowed) ?? segment
-  }
-
-  /// `<server>/remote.php/dav/files/<user>/<remotePath>` - [remotePath] is
-  /// relative to the user's root, with or without a leading slash. A server
-  /// installed under a sub-path (`https://host/nextcloud`) keeps it.
-  static func fileURL(serverUrl: String, username: String, remotePath: String) -> URL? {
-    var base = serverUrl
-    while base.hasSuffix("/") { base.removeLast() }
-    let segments = remotePath.split(separator: "/").map { encodeSegment(String($0)) }
-    var url = base + "/remote.php/dav/files/" + encodeSegment(username)
-    if !segments.isEmpty { url += "/" + segments.joined(separator: "/") }
-    return URL(string: url)
-  }
-
-  /// `folder` + `name` with exactly one slash between them.
-  static func join(_ folder: String, _ name: String) -> String {
-    folder.hasSuffix("/") ? folder + name : folder + "/" + name
-  }
-}
-
-enum LocalFiles {
-  /// A URL in [directory] for [name] that doesn't exist yet: "a.txt", then
-  /// "a (1).txt", "a (2).txt"... - so a second download of the same file
-  /// never overwrites the first.
-  static func uniqueURL(in directory: URL, name: String, fileManager: FileManager = .default) -> URL {
-    let candidate = directory.appendingPathComponent(name)
-    if !fileManager.fileExists(atPath: candidate.path) { return candidate }
-    let ext = (name as NSString).pathExtension
-    let stem = (name as NSString).deletingPathExtension
-    var index = 1
-    while true {
-      let numbered = ext.isEmpty ? "\(stem) (\(index))" : "\(stem) (\(index)).\(ext)"
-      let url = directory.appendingPathComponent(numbered)
-      if !fileManager.fileExists(atPath: url.path) { return url }
-      index += 1
-    }
-  }
-}