iOS: native upload and download services (background URLSession)

Swift implementation of the upload_service/download_service channels:
background PUT/GET against the account's WebDAV root, one summary local
notification per batch, Downloads visible in the Files app. Pure helpers
covered by RunnerTests.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>
This commit is contained in:
Ayushya Amitabh
2026-10-06 19:12:15 -04:00
co-authored by Claude Sonnet 5.5
parent d008185f98
commit 469e57cca7
8 changed files with 579 additions and 9 deletions
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import Flutter
import Foundation
/// Pushes upload-batch completions to Dart's `UploadService.completions`.
final class UploadStatusStreamHandler: NSObject, FlutterStreamHandler {
var sink: FlutterEventSink?
func onListen(withArguments arguments: Any?, eventSink events: @escaping FlutterEventSink)
-> FlutterError?
{
sink = events
return nil
}
func onCancel(withArguments arguments: Any?) -> FlutterError? {
sink = nil
return nil
}
}
/// The iOS side of the `dev.ayushya.noo/*` channels `lib/services/` talks to
/// (Android's lives in `MainActivity.kt`). Only the upload and download
/// services are implemented so far; the rest still throw
/// `MissingPluginException`, which the Dart side treats as "unavailable"
/// (`lib/services/native_channel.dart`).
enum NativeServices {
private static let uploadStatus = UploadStatusStreamHandler()
static func register(messenger: FlutterBinaryMessenger) {
FlutterMethodChannel(name: "dev.ayushya.noo/upload_service", binaryMessenger: messenger)
.setMethodCallHandler { call, result in
guard call.method == "startUpload" else { return result(FlutterMethodNotImplemented) }
handle(call, result) { args in
let files = try parseJSONList(args["files"])
try TransferManager.shared.startUpload(
serverUrl: try string(args, "serverUrl"),
username: try string(args, "username"),
authHeader: try string(args, "authHeader"),
files: files.compactMap { entry in
guard let uri = entry["uri"] as? String, let name = entry["name"] as? String else {
return nil
}
return UploadFile(uri: uri, name: name)
},
remoteFolder: (args["remoteFolder"] as? String) ?? "/"
)
}
}
FlutterMethodChannel(name: "dev.ayushya.noo/download_service", binaryMessenger: messenger)
.setMethodCallHandler { call, result in
guard call.method == "startDownload" else { return result(FlutterMethodNotImplemented) }
handle(call, result) { args in
let items = try parseJSONList(args["files"])
try TransferManager.shared.startDownload(
serverUrl: try string(args, "serverUrl"),
username: try string(args, "username"),
authHeader: try string(args, "authHeader"),
items: items.compactMap { entry in
guard let path = entry["path"] as? String, let name = entry["name"] as? String else {
return nil
}
return (path: path, name: name)
}
)
}
}
FlutterEventChannel(name: "dev.ayushya.noo/upload_service/status", binaryMessenger: messenger)
.setStreamHandler(uploadStatus)
TransferManager.shared.onUploadBatchFinished = { folder, succeeded, failed in
uploadStatus.sink?(["remoteFolder": folder, "succeeded": succeeded, "failed": failed])
}
TransferManager.shared.reconnect()
}
// MARK: - Argument helpers
/// Runs [work] with the call's argument map, turning a thrown error into
/// the `FlutterError` Dart's `catch` shows the user.
private static func handle(
_ call: FlutterMethodCall,
_ result: @escaping FlutterResult,
work: ([String: Any]) throws -> Void
) {
guard let args = call.arguments as? [String: Any] else {
return result(FlutterError(code: "bad_args", message: "Missing arguments.", details: nil))
}
do {
try work(args)
result(nil)
} catch {
result(FlutterError(code: "transfer_failed", message: error.localizedDescription, details: nil))
}
}
private static func string(_ args: [String: Any], _ key: String) throws -> String {
guard let value = args[key] as? String, !value.isEmpty else {
throw TransferError(message: "Missing \(key).")
}
return value
}
/// The Dart services pass their file list as one JSON string.
private static func parseJSONList(_ value: Any?) throws -> [[String: Any]] {
guard let json = value as? String,
let data = json.data(using: .utf8),
let list = try JSONSerialization.jsonObject(with: data) as? [[String: Any]]
else {
throw TransferError(message: "Missing file list.")
}
return list
}
}
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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`
/// foreground services, behind the same Dart channels (`NativeServices`).
///
/// Uploads are one `PUT` per file straight to the account's WebDAV root
/// (no chunking), from a staged copy in Caches - a background upload task
/// needs a file that stays put, and the picker's temp file may not. Downloads
/// land in `Documents/Downloads`, which is visible in the Files app
/// (`UIFileSharingEnabled` + `LSSupportsOpeningDocumentsInPlace`).
final class TransferManager: NSObject {
static let shared = TransferManager()
static let sessionIdentifier = "dev.ayushya.noo.transfers"
/// Called on the main thread when an upload batch ends with at least one
/// file uploaded: (remote folder, succeeded, failed).
var onUploadBatchFinished: ((String, Int, Int) -> Void)?
/// The system's completion handler from
/// `application(_:handleEventsForBackgroundURLSession:)`, called once the
/// 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
config.isDiscretionary = false
config.waitsForConnectivity = true
return URLSession(configuration: config, delegate: self, delegateQueue: nil)
}()
/// Touch the session at launch so a system relaunch for finished
/// background transfers reconnects to them.
func reconnect() {
_ = session
}
// MARK: - Starting transfers
func startUpload(
serverUrl: String,
username: String,
authHeader: String,
files: [UploadFile],
remoteFolder: String
) throws {
guard !files.isEmpty else { throw TransferError(message: "No files to upload.") }
let batch = UUID().uuidString
let stageDir = try Self.stagingDirectory().appendingPathComponent(batch, isDirectory: true)
try FileManager.default.createDirectory(at: stageDir, withIntermediateDirectories: true)
var tasks: [URLSessionUploadTask] = []
for (index, file) in files.enumerated() {
guard let source = URL(string: file.uri), source.isFileURL else {
throw TransferError(message: "Can't read \(file.name).")
}
let staged = stageDir.appendingPathComponent("\(index)-\(file.name)")
do {
try FileManager.default.copyItem(at: source, to: staged)
} catch {
throw TransferError(message: "Can't read \(file.name): \(error.localizedDescription)")
}
guard let url = WebDAV.fileURL(
serverUrl: serverUrl,
username: username,
remotePath: WebDAV.join(remoteFolder, file.name)
) else {
throw TransferError(message: "Invalid server address.")
}
var request = URLRequest(url: url)
request.httpMethod = "PUT"
request.setValue(authHeader, forHTTPHeaderField: "Authorization")
if let modified = (try? FileManager.default.attributesOfItem(atPath: staged.path))?[.modificationDate] as? Date {
request.setValue(String(Int(modified.timeIntervalSince1970)), forHTTPHeaderField: "X-OC-Mtime")
}
let task = session.uploadTask(with: request, fromFile: staged)
task.taskDescription = Self.encode(
TransferTaskInfo(
kind: .upload, batch: batch, name: file.name,
remoteFolder: remoteFolder, stagedPath: staged.path
)
)
tasks.append(task)
}
saveBatch(
TransferBatch(kind: .upload, remoteFolder: remoteFolder, total: tasks.count, succeeded: 0, failed: 0),
id: batch
)
tasks.forEach { $0.resume() }
}
func startDownload(
serverUrl: String,
username: String,
authHeader: String,
items: [(path: String, name: String)]
) throws {
guard !items.isEmpty else { throw TransferError(message: "No files to download.") }
let batch = UUID().uuidString
var tasks: [URLSessionDownloadTask] = []
for item in items {
guard let url = WebDAV.fileURL(serverUrl: serverUrl, username: username, remotePath: item.path) else {
throw TransferError(message: "Invalid server address.")
}
var request = URLRequest(url: url)
request.setValue(authHeader, forHTTPHeaderField: "Authorization")
let task = session.downloadTask(with: request)
task.taskDescription = Self.encode(
TransferTaskInfo(kind: .download, batch: batch, name: item.name, remoteFolder: nil, stagedPath: nil)
)
tasks.append(task)
}
saveBatch(
TransferBatch(kind: .download, remoteFolder: nil, total: tasks.count, succeeded: 0, failed: 0),
id: batch
)
tasks.forEach { $0.resume() }
}
// MARK: - Locations
private static func stagingDirectory() throws -> URL {
let caches = try FileManager.default.url(
for: .cachesDirectory, in: .userDomainMask, appropriateFor: nil, create: true
)
return caches.appendingPathComponent("uploads", isDirectory: true)
}
static func downloadsDirectory() throws -> URL {
let documents = try FileManager.default.url(
for: .documentDirectory, in: .userDomainMask, appropriateFor: nil, create: true
)
let dir = documents.appendingPathComponent("Downloads", isDirectory: true)
try FileManager.default.createDirectory(at: dir, withIntermediateDirectories: true)
return dir
}
// MARK: - Batch bookkeeping
private static func encode(_ info: TransferTaskInfo) -> String? {
(try? JSONEncoder().encode(info)).flatMap { String(data: $0, encoding: .utf8) }
}
private static func info(for task: URLSessionTask) -> TransferTaskInfo? {
task.taskDescription
.flatMap { $0.data(using: .utf8) }
.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) }
}
private func finish(_ batch: TransferBatch) {
let verb = batch.kind == .upload ? "upload" : "download"
let past = batch.kind == .upload ? "Uploaded" : "Downloaded"
let body: String
if batch.failed == 0 {
body = "\(past) \(Self.files(batch.succeeded))"
} else if batch.succeeded == 0 {
body = "Couldn't \(verb) \(Self.files(batch.failed))"
} else {
body = "\(past) \(Self.files(batch.succeeded)), \(batch.failed) failed"
}
notify(body)
if batch.kind == .upload, batch.succeeded > 0, let folder = batch.remoteFolder {
DispatchQueue.main.async { self.onUploadBatchFinished?(folder, batch.succeeded, batch.failed) }
}
}
private static func files(_ count: Int) -> String {
count == 1 ? "1 file" : "\(count) files"
}
private func notify(_ body: String) {
let content = UNMutableNotificationContent()
content.title = "Noo"
content.body = body
content.sound = .default
UNUserNotificationCenter.current().add(
UNNotificationRequest(identifier: UUID().uuidString, content: content, trigger: nil)
)
}
}
// MARK: - URLSession delegates
extension TransferManager: URLSessionDownloadDelegate {
func urlSession(
_ session: URLSession, downloadTask: URLSessionDownloadTask, didFinishDownloadingTo location: URL
) {
guard let info = Self.info(for: downloadTask) else { return }
let status = (downloadTask.response as? HTTPURLResponse)?.statusCode ?? 0
guard (200..<300).contains(status) else {
record(info, success: false)
return
}
do {
let destination = LocalFiles.uniqueURL(in: try Self.downloadsDirectory(), name: info.name)
try FileManager.default.moveItem(at: location, to: destination)
record(info, success: true)
} catch {
record(info, success: false)
}
}
func urlSession(_ session: URLSession, task: URLSessionTask, didCompleteWithError error: Error?) {
guard let info = Self.info(for: task) else { return }
switch info.kind {
case .upload:
if let staged = info.stagedPath { try? FileManager.default.removeItem(atPath: staged) }
let status = (task.response as? HTTPURLResponse)?.statusCode ?? 0
record(info, success: error == nil && (200..<300).contains(status))
case .download:
// A finished download was already counted in didFinishDownloadingTo;
// only a transport failure arrives here.
if error != nil { record(info, success: false) }
}
}
func urlSessionDidFinishEvents(forBackgroundURLSession session: URLSession) {
DispatchQueue.main.async {
self.backgroundCompletionHandler?()
self.backgroundCompletionHandler = nil
}
}
}
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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
}
}
}