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/ShareExtension/Info.plist

@@ -20,6 +20,8 @@
 	<string>$(MARKETING_VERSION)</string>
 	<key>CFBundleVersion</key>
 	<string>$(CURRENT_PROJECT_VERSION)</string>
+	<key>NooKeychainAccessGroup</key>
+	<string>$(AppIdentifierPrefix)dev.ayushya.noo.shared</string>
 	<key>NSExtension</key>
 	<dict>
 		<key>NSExtensionAttributes</key>

ios/ShareExtension/ShareExtension.entitlements

@@ -6,5 +6,9 @@
 	<array>
 		<string>group.dev.ayushya.noo</string>
 	</array>
+	<key>keychain-access-groups</key>
+	<array>
+		<string>$(AppIdentifierPrefix)dev.ayushya.noo.shared</string>
+	</array>
 </dict>
 </plist>

ios/ShareExtension/SharePickerView.swift

@@ -0,0 +1,168 @@
+import SwiftUI
+
+/// State behind the share sheet's folder picker.
+@MainActor
+final class ShareModel: ObservableObject {
+  enum Stage: Equatable {
+    case preparing
+    case picking
+    case uploading
+    case noAccount
+    case failed(String)
+  }
+
+  @Published var stage: Stage = .preparing
+  @Published var items: [SharedItem] = []
+  @Published var path = "/"
+  @Published var folders: [DavFolder] = []
+  @Published var isLoadingFolders = false
+  @Published var folderError: String?
+
+  let account: SharedAccount?
+
+  /// Set by the view controller: what each button actually does.
+  var onUpload: () -> Void = {}
+  var onSaveForLater: () -> Void = {}
+  var onCancel: () -> Void = {}
+
+  init(account: SharedAccount?) {
+    self.account = account
+  }
+
+  var currentFolderName: String {
+    path == "/" ? "All files" : (path as NSString).lastPathComponent
+  }
+
+  var fileCountText: String {
+    items.count == 1 ? "1 file" : "\(items.count) files"
+  }
+
+  func open(_ path: String) async {
+    guard let account else { return }
+    self.path = path
+    isLoadingFolders = true
+    folderError = nil
+    defer { isLoadingFolders = false }
+    do {
+      folders = try await DavClient.listFolders(account: account, path: path)
+    } catch {
+      folders = []
+      folderError = error.localizedDescription
+    }
+  }
+
+  func openParent() async {
+    let parent = (path as NSString).deletingLastPathComponent
+    await open(parent.isEmpty ? "/" : parent)
+  }
+}
+
+struct SharePickerView: View {
+  @ObservedObject var model: ShareModel
+
+  var body: some View {
+    VStack(spacing: 0) {
+      header
+      Divider()
+      content
+      Divider()
+      footer
+    }
+    .background(Color(.systemBackground))
+  }
+
+  private var header: some View {
+    HStack {
+      Button("Cancel", action: model.onCancel)
+      Spacer()
+      Text("Upload to Noo").font(.headline)
+      Spacer()
+      // Balances Cancel so the title stays centred.
+      Button("Cancel", action: {}).hidden()
+    }
+    .padding(.horizontal)
+    .padding(.vertical, 12)
+  }
+
+  @ViewBuilder
+  private var content: some View {
+    switch model.stage {
+    case .preparing:
+      centered { ProgressView("Preparing \(model.items.isEmpty ? "" : model.fileCountText)…") }
+    case .uploading:
+      centered {
+        VStack(spacing: 8) {
+          ProgressView()
+          Text("Uploading \(model.fileCountText) in the background").font(.subheadline)
+        }
+      }
+    case .noAccount:
+      centered {
+        Text("Sign in to Noo first, then share again. You can also save these files and choose a folder from inside Noo.")
+          .multilineTextAlignment(.center)
+          .foregroundColor(.secondary)
+          .padding()
+      }
+    case .failed(let message):
+      centered {
+        Text(message).multilineTextAlignment(.center).foregroundColor(.secondary).padding()
+      }
+    case .picking:
+      folderList
+    }
+  }
+
+  private var folderList: some View {
+    List {
+      Section(header: Text(model.account?.displayName ?? "")) {
+        if model.path != "/" {
+          Button {
+            Task { await model.openParent() }
+          } label: {
+            Label("Up to \((model.path as NSString).deletingLastPathComponent == "/" ? "All files" : ((model.path as NSString).deletingLastPathComponent as NSString).lastPathComponent)", systemImage: "arrow.turn.left.up")
+          }
+        }
+        if model.isLoadingFolders {
+          HStack { Spacer(); ProgressView(); Spacer() }
+        } else if let error = model.folderError {
+          Text(error).foregroundColor(.secondary)
+        } else if model.folders.isEmpty {
+          Text("No folders here").foregroundColor(.secondary)
+        } else {
+          ForEach(model.folders, id: \.path) { folder in
+            Button {
+              Task { await model.open(folder.path) }
+            } label: {
+              Label(folder.name, systemImage: "folder")
+            }
+          }
+        }
+      }
+    }
+    .listStyle(.insetGrouped)
+  }
+
+  private var footer: some View {
+    VStack(spacing: 8) {
+      if model.stage == .picking {
+        Button(action: model.onUpload) {
+          Text("Upload \(model.fileCountText) to \(model.currentFolderName)")
+            .font(.headline)
+            .frame(maxWidth: .infinity)
+            .padding(.vertical, 12)
+        }
+        .buttonStyle(.borderedProminent)
+        .disabled(model.isLoadingFolders)
+      }
+      if model.stage == .picking || model.stage == .noAccount {
+        Button("Choose a folder later in Noo", action: model.onSaveForLater)
+          .font(.subheadline)
+      }
+    }
+    .padding()
+  }
+
+  private func centered<Content: View>(@ViewBuilder _ content: () -> Content) -> some View {
+    VStack { Spacer(); content(); Spacer() }.frame(maxWidth: .infinity)
+  }
+}

ios/ShareExtension/ShareViewController.swift

@@ -1,66 +1,79 @@
+import SwiftUI
 import UIKit
 import UniformTypeIdentifiers
 import UserNotifications
 
-/// "Share to Noo": copies whatever was shared into the App Group container
-/// (`SharedInbox`) and finishes. The extension can't pick a destination or
-/// upload - it has no session and a tight memory/time budget - so the app
-/// does that when it next opens, through its existing destination picker. A
-/// notification tells the user to open it, because an extension can't launch
-/// its host app.
+/// "Share to Noo". Like Reminders' or Notes' share sheet, the destination is
+/// chosen *inside* the sheet - an extension can't open its host app - so this
+/// shows a folder picker, then starts a background upload and closes:
+///
+/// 1. Copies whatever was shared into the App Group (`SharedInbox`).
+/// 2. Reads the signed-in account the app left in the shared Keychain
+///    (`SharedAccountStore`) and lists folders over WebDAV (`DavClient`).
+/// 3. "Upload" queues the files on a background session that outlives this
+///    process (`ShareUpload`); the app is relaunched to finish and notify.
+///
+/// With no account, or if the user prefers, the files are instead left in the
+/// inbox for the app to offer its own destination picker next time it opens
+/// (with a notification saying so).
 final class ShareViewController: UIViewController {
-  private let label = UILabel()
-  private let spinner = UIActivityIndicatorView(style: .large)
+  private var model: ShareModel!
+  private var batchDirectory: URL?
 
   override func viewDidLoad() {
     super.viewDidLoad()
-    view.backgroundColor = .systemBackground
-    label.text = "Saving to Noo…"
-    label.font = .preferredFont(forTextStyle: .headline)
-    label.textAlignment = .center
-    label.numberOfLines = 0
-    spinner.startAnimating()
+    model = ShareModel(account: SharedAccountStore.load())
+    model.onUpload = { [weak self] in self?.upload() }
+    model.onSaveForLater = { [weak self] in self?.saveForLater() }
+    model.onCancel = { [weak self] in self?.cancel() }
 
-    let stack = UIStackView(arrangedSubviews: [spinner, label])
-    stack.axis = .vertical
-    stack.spacing = 16
-    stack.alignment = .center
-    stack.translatesAutoresizingMaskIntoConstraints = false
-    view.addSubview(stack)
+    let host = UIHostingController(rootView: SharePickerView(model: model))
+    addChild(host)
+    host.view.translatesAutoresizingMaskIntoConstraints = false
+    view.addSubview(host.view)
     NSLayoutConstraint.activate([
-      stack.centerXAnchor.constraint(equalTo: view.centerXAnchor),
-      stack.centerYAnchor.constraint(equalTo: view.centerYAnchor),
-      stack.leadingAnchor.constraint(greaterThanOrEqualTo: view.leadingAnchor, constant: 24),
-      stack.trailingAnchor.constraint(lessThanOrEqualTo: view.trailingAnchor, constant: -24),
+      host.view.topAnchor.constraint(equalTo: view.topAnchor),
+      host.view.bottomAnchor.constraint(equalTo: view.bottomAnchor),
+      host.view.leadingAnchor.constraint(equalTo: view.leadingAnchor),
+      host.view.trailingAnchor.constraint(equalTo: view.trailingAnchor),
     ])
+    host.didMove(toParent: self)
 
-    Task { await importSharedItems() }
+    Task { await prepare() }
   }
 
-  private func importSharedItems() async {
+  // MARK: - Importing
+
+  @MainActor
+  private func prepare() async {
     guard let root = AppGroup.containerURL else {
-      return finish(message: "Noo isn't set up to receive files yet.", saved: 0)
+      model.stage = .failed("Noo isn't set up to receive files yet.")
+      return
     }
-    let providers = (extensionContext?.inputItems as? [NSExtensionItem])?
-      .flatMap { $0.attachments ?? [] } ?? []
+    let providers =
+      (extensionContext?.inputItems as? [NSExtensionItem])?.flatMap { $0.attachments ?? [] } ?? []
 
-    var saved: [SharedItem] = []
     do {
       let batch = try SharedInbox.makeBatchDirectory(in: root)
+      batchDirectory = batch
       for provider in providers where provider.hasItemConformingToTypeIdentifier(UTType.item.identifier) {
-        if let item = try? await copy(provider, into: batch) { saved.append(item) }
+        if let item = try? await copy(provider, into: batch) { model.items.append(item) }
       }
-      try SharedInbox.append(saved, in: root)
     } catch {
-      return finish(message: "Couldn't save to Noo: \(error.localizedDescription)", saved: 0)
+      model.stage = .failed("Couldn't save to Noo: \(error.localizedDescription)")
+      return
     }
 
-    if saved.isEmpty {
-      finish(message: "Noo can only receive files and photos.", saved: 0)
-    } else {
-      notify(count: saved.count)
-      finish(message: saved.count == 1 ? "Saved 1 file to Noo" : "Saved \(saved.count) files to Noo", saved: saved.count)
+    guard !model.items.isEmpty else {
+      model.stage = .failed("Noo can only receive files and photos.")
+      return
     }
+    guard model.account != nil else {
+      model.stage = .noAccount
+      return
+    }
+    model.stage = .picking
+    await model.open("/")
   }
 
   /// `loadFileRepresentation`'s URL only lives for the duration of its
@@ -72,7 +85,7 @@ final class ShareViewController: UIViewController {
           return continuation.resume(throwing: error ?? CocoaError(.fileReadUnknown))
         }
         do {
-          let destination = Self.uniqueURL(in: directory, name: url.lastPathComponent)
+          let destination = LocalFiles.uniqueURL(in: directory, name: url.lastPathComponent)
           try FileManager.default.copyItem(at: url, to: destination)
           let size = (try? FileManager.default.attributesOfItem(atPath: destination.path))?[.size] as? Int64 ?? 0
           let mime = UTType(filenameExtension: destination.pathExtension)?.preferredMIMEType
@@ -86,19 +99,42 @@ final class ShareViewController: UIViewController {
     }
   }
 
-  private static func uniqueURL(in directory: URL, name: String) -> URL {
-    var candidate = directory.appendingPathComponent(name)
-    var index = 1
-    while FileManager.default.fileExists(atPath: candidate.path) {
-      let ext = (name as NSString).pathExtension
-      let stem = (name as NSString).deletingPathExtension
-      candidate = directory.appendingPathComponent(ext.isEmpty ? "\(stem) (\(index))" : "\(stem) (\(index)).\(ext)")
-      index += 1
+  // MARK: - Actions
+
+  private func upload() {
+    guard let account = model.account else { return }
+    do {
+      try ShareUpload.enqueue(items: model.items, account: account, remoteFolder: model.path)
+      model.stage = .uploading
+      complete(after: 1.2)
+    } catch {
+      model.stage = .failed("Couldn't start the upload: \(error.localizedDescription)")
     }
-    return candidate
   }
 
-  private func notify(count: Int) {
+  private func saveForLater() {
+    guard let root = AppGroup.containerURL else { return cancel() }
+    do {
+      try SharedInbox.append(model.items, in: root)
+      notifyOpenNoo(count: model.items.count)
+      complete(after: 0)
+    } catch {
+      model.stage = .failed("Couldn't save to Noo: \(error.localizedDescription)")
+    }
+  }
+
+  private func cancel() {
+    if let batchDirectory { try? FileManager.default.removeItem(at: batchDirectory) }
+    extensionContext?.cancelRequest(withError: CocoaError(.userCancelled))
+  }
+
+  private func complete(after delay: TimeInterval) {
+    DispatchQueue.main.asyncAfter(deadline: .now() + delay) {
+      self.extensionContext?.completeRequest(returningItems: nil)
+    }
+  }
+
+  private func notifyOpenNoo(count: Int) {
     let content = UNMutableNotificationContent()
     content.title = "Noo"
     content.body =
@@ -109,14 +145,4 @@ final class ShareViewController: UIViewController {
     UNUserNotificationCenter.current().add(
       UNNotificationRequest(identifier: UUID().uuidString, content: content, trigger: nil))
   }
-
-  private func finish(message: String, saved: Int) {
-    DispatchQueue.main.async {
-      self.spinner.stopAnimating()
-      self.label.text = message
-      DispatchQueue.main.asyncAfter(deadline: .now() + (saved > 0 ? 1.2 : 2.5)) {
-        self.extensionContext?.completeRequest(returningItems: nil)
-      }
-    }
-  }
 }