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| 1 | +// |
| 2 | +// Downloader.swift |
| 3 | +// Diffusion |
| 4 | +// |
| 5 | +// Created by Pedro Cuenca on December 2022. |
| 6 | +// See LICENSE at https://github.com/huggingface/swift-coreml-diffusers/LICENSE |
| 7 | +// |
| 8 | + |
| 9 | +import Foundation |
| 10 | +import Combine |
| 11 | +import Path |
| 12 | + |
| 13 | +class Downloader: NSObject, ObservableObject { |
| 14 | + private(set) var destination: URL |
| 15 | + |
| 16 | + enum DownloadState { |
| 17 | + case notStarted |
| 18 | + case downloading(Double) |
| 19 | + case completed(URL) |
| 20 | + case failed(Error) |
| 21 | + } |
| 22 | + |
| 23 | + private(set) lazy var downloadState: CurrentValueSubject<DownloadState, Never> = CurrentValueSubject(.notStarted) |
| 24 | + private var stateSubscriber: Cancellable? |
| 25 | + |
| 26 | + init(from url: URL, to destination: URL) { |
| 27 | + self.destination = destination |
| 28 | + super.init() |
| 29 | + |
| 30 | + // .background allows downloads to proceed in the background |
| 31 | + let config = URLSessionConfiguration.background(withIdentifier: "net.pcuenca.diffusion.download") |
| 32 | + let urlSession = URLSession(configuration: config, delegate: self, delegateQueue: OperationQueue()) |
| 33 | + downloadState.value = .downloading(0) |
| 34 | + urlSession.getAllTasks { tasks in |
| 35 | + // If there's an existing pending background task, let it proceed, otherwise start a new one. |
| 36 | + // TODO: check URL when we support downloading more models. |
| 37 | + if tasks.first == nil { |
| 38 | + urlSession.downloadTask(with: url).resume() |
| 39 | + } |
| 40 | + } |
| 41 | + } |
| 42 | + |
| 43 | + @discardableResult |
| 44 | + func waitUntilDone() throws -> URL { |
| 45 | + // It's either this, or stream the bytes ourselves (add to a buffer, save to disk, etc; boring and finicky) |
| 46 | + let semaphore = DispatchSemaphore(value: 0) |
| 47 | + stateSubscriber = downloadState.sink { state in |
| 48 | + switch state { |
| 49 | + case .completed: semaphore.signal() |
| 50 | + case .failed: semaphore.signal() |
| 51 | + default: break |
| 52 | + } |
| 53 | + } |
| 54 | + semaphore.wait() |
| 55 | + |
| 56 | + switch downloadState.value { |
| 57 | + case .completed(let url): return url |
| 58 | + case .failed(let error): throw error |
| 59 | + default: throw("Should never happen, lol") |
| 60 | + } |
| 61 | + } |
| 62 | +} |
| 63 | + |
| 64 | +extension Downloader: URLSessionDelegate, URLSessionDownloadDelegate { |
| 65 | + func urlSession(_: URLSession, downloadTask: URLSessionDownloadTask, didWriteData _: Int64, totalBytesWritten _: Int64, totalBytesExpectedToWrite _: Int64) { |
| 66 | + downloadState.value = .downloading(downloadTask.progress.fractionCompleted) |
| 67 | + } |
| 68 | + |
| 69 | + func urlSession(_: URLSession, downloadTask _: URLSessionDownloadTask, didFinishDownloadingTo location: URL) { |
| 70 | + guard let path = Path(url: location) else { |
| 71 | + downloadState.value = .failed("Invalid download location received: \(location)") |
| 72 | + return |
| 73 | + } |
| 74 | + guard let toPath = Path(url: destination) else { |
| 75 | + downloadState.value = .failed("Invalid destination: \(destination)") |
| 76 | + return |
| 77 | + } |
| 78 | + do { |
| 79 | + try path.move(to: toPath, overwrite: true) |
| 80 | + downloadState.value = .completed(destination) |
| 81 | + } catch { |
| 82 | + downloadState.value = .failed(error) |
| 83 | + } |
| 84 | + } |
| 85 | + |
| 86 | + func urlSession(_: URLSession, task: URLSessionTask, didCompleteWithError error: Error?) { |
| 87 | + if let error = error { |
| 88 | + downloadState.value = .failed(error) |
| 89 | + } |
| 90 | + } |
| 91 | +} |
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