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
co-authored by
Claude Sonnet 5.5
Claude Sonnet 5.5
parent
d008185f98
commit
469e57cca7
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import Foundation
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import UserNotifications
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/// What a background upload/download task is, stored in the task's
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/// `taskDescription` so it's still known if the app was relaunched by the
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/// system to deliver the result.
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struct TransferTaskInfo: Codable {
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enum Kind: String, Codable { case upload, download }
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let kind: Kind
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let batch: String
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let name: String
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let remoteFolder: String?
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let stagedPath: String?
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}
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/// Running totals for one "upload these 3 files" / "download these 2 files"
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/// request, persisted so the one summary notification (and the Dart-side
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/// "folder changed" event) fires exactly once, on the last file, even across
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/// an app relaunch.
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struct TransferBatch: Codable {
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let kind: TransferTaskInfo.Kind
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let remoteFolder: String?
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let total: Int
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var succeeded: Int
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var failed: Int
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var finished: Int { succeeded + failed }
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}
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struct UploadFile {
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let uri: String
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let name: String
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}
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struct TransferError: LocalizedError {
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let message: String
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var errorDescription: String? { message }
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}
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/// Uploads and downloads on a background `URLSession`, so a transfer keeps
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/// going - and finishes - after the app is suspended or closed. The iOS
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/// counterpart of Android's `ShareUploadService`/`DownloadService`
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/// foreground services, behind the same Dart channels (`NativeServices`).
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///
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/// Uploads are one `PUT` per file straight to the account's WebDAV root
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/// (no chunking), from a staged copy in Caches - a background upload task
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/// needs a file that stays put, and the picker's temp file may not. Downloads
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/// land in `Documents/Downloads`, which is visible in the Files app
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/// (`UIFileSharingEnabled` + `LSSupportsOpeningDocumentsInPlace`).
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final class TransferManager: NSObject {
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static let shared = TransferManager()
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static let sessionIdentifier = "dev.ayushya.noo.transfers"
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/// Called on the main thread when an upload batch ends with at least one
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/// file uploaded: (remote folder, succeeded, failed).
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var onUploadBatchFinished: ((String, Int, Int) -> Void)?
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/// The system's completion handler from
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/// `application(_:handleEventsForBackgroundURLSession:)`, called once the
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/// session has delivered every pending event.
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var backgroundCompletionHandler: (() -> Void)?
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private let defaults = UserDefaults.standard
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private let lock = NSLock()
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private lazy var session: URLSession = {
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let config = URLSessionConfiguration.background(withIdentifier: Self.sessionIdentifier)
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config.sessionSendsLaunchEvents = true
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config.isDiscretionary = false
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config.waitsForConnectivity = true
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return URLSession(configuration: config, delegate: self, delegateQueue: nil)
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}()
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/// Touch the session at launch so a system relaunch for finished
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/// background transfers reconnects to them.
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func reconnect() {
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_ = session
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}
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// MARK: - Starting transfers
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func startUpload(
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serverUrl: String,
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username: String,
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authHeader: String,
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files: [UploadFile],
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remoteFolder: String
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) throws {
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guard !files.isEmpty else { throw TransferError(message: "No files to upload.") }
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let batch = UUID().uuidString
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let stageDir = try Self.stagingDirectory().appendingPathComponent(batch, isDirectory: true)
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try FileManager.default.createDirectory(at: stageDir, withIntermediateDirectories: true)
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var tasks: [URLSessionUploadTask] = []
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for (index, file) in files.enumerated() {
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guard let source = URL(string: file.uri), source.isFileURL else {
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throw TransferError(message: "Can't read \(file.name).")
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}
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let staged = stageDir.appendingPathComponent("\(index)-\(file.name)")
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do {
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try FileManager.default.copyItem(at: source, to: staged)
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} catch {
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throw TransferError(message: "Can't read \(file.name): \(error.localizedDescription)")
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}
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guard let url = WebDAV.fileURL(
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serverUrl: serverUrl,
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username: username,
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remotePath: WebDAV.join(remoteFolder, file.name)
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) else {
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throw TransferError(message: "Invalid server address.")
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}
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var request = URLRequest(url: url)
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request.httpMethod = "PUT"
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request.setValue(authHeader, forHTTPHeaderField: "Authorization")
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if let modified = (try? FileManager.default.attributesOfItem(atPath: staged.path))?[.modificationDate] as? Date {
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request.setValue(String(Int(modified.timeIntervalSince1970)), forHTTPHeaderField: "X-OC-Mtime")
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}
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let task = session.uploadTask(with: request, fromFile: staged)
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task.taskDescription = Self.encode(
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TransferTaskInfo(
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kind: .upload, batch: batch, name: file.name,
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remoteFolder: remoteFolder, stagedPath: staged.path
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)
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)
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tasks.append(task)
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}
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saveBatch(
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TransferBatch(kind: .upload, remoteFolder: remoteFolder, total: tasks.count, succeeded: 0, failed: 0),
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id: batch
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)
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tasks.forEach { $0.resume() }
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}
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func startDownload(
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serverUrl: String,
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username: String,
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authHeader: String,
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items: [(path: String, name: String)]
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) throws {
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guard !items.isEmpty else { throw TransferError(message: "No files to download.") }
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let batch = UUID().uuidString
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var tasks: [URLSessionDownloadTask] = []
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for item in items {
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guard let url = WebDAV.fileURL(serverUrl: serverUrl, username: username, remotePath: item.path) else {
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throw TransferError(message: "Invalid server address.")
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}
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var request = URLRequest(url: url)
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request.setValue(authHeader, forHTTPHeaderField: "Authorization")
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let task = session.downloadTask(with: request)
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task.taskDescription = Self.encode(
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TransferTaskInfo(kind: .download, batch: batch, name: item.name, remoteFolder: nil, stagedPath: nil)
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)
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tasks.append(task)
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}
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saveBatch(
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TransferBatch(kind: .download, remoteFolder: nil, total: tasks.count, succeeded: 0, failed: 0),
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id: batch
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)
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tasks.forEach { $0.resume() }
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}
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// MARK: - Locations
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private static func stagingDirectory() throws -> URL {
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let caches = try FileManager.default.url(
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for: .cachesDirectory, in: .userDomainMask, appropriateFor: nil, create: true
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)
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return caches.appendingPathComponent("uploads", isDirectory: true)
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}
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static func downloadsDirectory() throws -> URL {
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let documents = try FileManager.default.url(
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for: .documentDirectory, in: .userDomainMask, appropriateFor: nil, create: true
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)
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let dir = documents.appendingPathComponent("Downloads", isDirectory: true)
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try FileManager.default.createDirectory(at: dir, withIntermediateDirectories: true)
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return dir
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}
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// MARK: - Batch bookkeeping
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private static func encode(_ info: TransferTaskInfo) -> String? {
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(try? JSONEncoder().encode(info)).flatMap { String(data: $0, encoding: .utf8) }
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}
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private static func info(for task: URLSessionTask) -> TransferTaskInfo? {
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task.taskDescription
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.flatMap { $0.data(using: .utf8) }
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.flatMap { try? JSONDecoder().decode(TransferTaskInfo.self, from: $0) }
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}
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private func key(_ id: String) -> String { "transfer.batch.\(id)" }
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private func saveBatch(_ batch: TransferBatch, id: String) {
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lock.lock()
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defer { lock.unlock() }
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if let data = try? JSONEncoder().encode(batch) { defaults.set(data, forKey: key(id)) }
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}
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/// Counts one file's outcome; fires the batch summary when it was the last.
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private func record(_ info: TransferTaskInfo, success: Bool) {
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lock.lock()
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let storageKey = key(info.batch)
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var batch =
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(defaults.data(forKey: storageKey).flatMap { try? JSONDecoder().decode(TransferBatch.self, from: $0) })
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?? TransferBatch(kind: info.kind, remoteFolder: info.remoteFolder, total: 1, succeeded: 0, failed: 0)
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if success { batch.succeeded += 1 } else { batch.failed += 1 }
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let done = batch.finished >= batch.total
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if done {
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defaults.removeObject(forKey: storageKey)
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} else if let data = try? JSONEncoder().encode(batch) {
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defaults.set(data, forKey: storageKey)
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}
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lock.unlock()
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if done { finish(batch) }
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}
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private func finish(_ batch: TransferBatch) {
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let verb = batch.kind == .upload ? "upload" : "download"
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let past = batch.kind == .upload ? "Uploaded" : "Downloaded"
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let body: String
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if batch.failed == 0 {
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body = "\(past) \(Self.files(batch.succeeded))"
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} else if batch.succeeded == 0 {
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body = "Couldn't \(verb) \(Self.files(batch.failed))"
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} else {
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body = "\(past) \(Self.files(batch.succeeded)), \(batch.failed) failed"
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}
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notify(body)
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if batch.kind == .upload, batch.succeeded > 0, let folder = batch.remoteFolder {
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DispatchQueue.main.async { self.onUploadBatchFinished?(folder, batch.succeeded, batch.failed) }
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}
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}
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private static func files(_ count: Int) -> String {
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count == 1 ? "1 file" : "\(count) files"
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}
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private func notify(_ body: String) {
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let content = UNMutableNotificationContent()
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content.title = "Noo"
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content.body = body
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content.sound = .default
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UNUserNotificationCenter.current().add(
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UNNotificationRequest(identifier: UUID().uuidString, content: content, trigger: nil)
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)
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}
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}
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// MARK: - URLSession delegates
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extension TransferManager: URLSessionDownloadDelegate {
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func urlSession(
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_ session: URLSession, downloadTask: URLSessionDownloadTask, didFinishDownloadingTo location: URL
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) {
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guard let info = Self.info(for: downloadTask) else { return }
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let status = (downloadTask.response as? HTTPURLResponse)?.statusCode ?? 0
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guard (200..<300).contains(status) else {
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record(info, success: false)
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return
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}
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do {
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let destination = LocalFiles.uniqueURL(in: try Self.downloadsDirectory(), name: info.name)
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try FileManager.default.moveItem(at: location, to: destination)
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record(info, success: true)
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} catch {
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record(info, success: false)
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}
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}
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func urlSession(_ session: URLSession, task: URLSessionTask, didCompleteWithError error: Error?) {
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guard let info = Self.info(for: task) else { return }
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switch info.kind {
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case .upload:
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if let staged = info.stagedPath { try? FileManager.default.removeItem(atPath: staged) }
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let status = (task.response as? HTTPURLResponse)?.statusCode ?? 0
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record(info, success: error == nil && (200..<300).contains(status))
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case .download:
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// A finished download was already counted in didFinishDownloadingTo;
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// only a transport failure arrives here.
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if error != nil { record(info, success: false) }
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}
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}
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func urlSessionDidFinishEvents(forBackgroundURLSession session: URLSession) {
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DispatchQueue.main.async {
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self.backgroundCompletionHandler?()
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self.backgroundCompletionHandler = nil
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}
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}
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}
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