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7 | 7 | // |
8 | 8 |
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9 | 9 | import Foundation |
10 | | -import Combine |
11 | | - |
12 | | -class Downloader: NSObject, ObservableObject { |
13 | | - private(set) var destination: URL |
14 | | - |
15 | | - enum DownloadState { |
16 | | - case notStarted |
17 | | - case downloading(Double) |
18 | | - case completed(URL) |
19 | | - case failed(Error) |
20 | | - } |
21 | | - |
22 | | - enum DownloadError: Error { |
23 | | - case invalidDownloadLocation |
24 | | - case unexpectedError |
25 | | - } |
26 | | - |
27 | | - private(set) lazy var downloadState: CurrentValueSubject<DownloadState, Never> = CurrentValueSubject(.notStarted) |
28 | | - private var stateSubscriber: Cancellable? |
29 | | - |
30 | | - private var urlSession: URLSession? = nil |
31 | | - |
32 | | - init(from url: URL, to destination: URL, using authToken: String? = nil, inBackground: Bool = false) { |
33 | | - self.destination = destination |
34 | | - super.init() |
35 | | - let sessionIdentifier = "swift-transformers.hub.downloader" |
36 | | - |
37 | | - var config = URLSessionConfiguration.default |
38 | | - if inBackground { |
39 | | - config = URLSessionConfiguration.background(withIdentifier: sessionIdentifier) |
40 | | - config.isDiscretionary = false |
41 | | - config.sessionSendsLaunchEvents = true |
42 | | - } |
43 | | - |
44 | | - self.urlSession = URLSession(configuration: config, delegate: self, delegateQueue: nil) |
45 | | - |
46 | | - setupDownload(from: url, with: authToken) |
47 | | - } |
48 | | - |
49 | | - private func setupDownload(from url: URL, with authToken: String?) { |
50 | | - downloadState.value = .downloading(0) |
51 | | - urlSession?.getAllTasks { tasks in |
52 | | - // If there's an existing pending background task with the same URL, let it proceed. |
53 | | - if let existing = tasks.filter({ $0.originalRequest?.url == url }).first { |
54 | | - switch existing.state { |
55 | | - case .running: |
56 | | - // print("Already downloading \(url)") |
57 | | - return |
58 | | - case .suspended: |
59 | | - // print("Resuming suspended download task for \(url)") |
60 | | - existing.resume() |
61 | | - return |
62 | | - case .canceling: |
63 | | - // print("Starting new download task for \(url), previous was canceling") |
64 | | - break |
65 | | - case .completed: |
66 | | - // print("Starting new download task for \(url), previous is complete but the file is no longer present (I think it's cached)") |
67 | | - break |
68 | | - @unknown default: |
69 | | - // print("Unknown state for running task; cancelling and creating a new one") |
70 | | - existing.cancel() |
71 | | - } |
72 | | - } |
73 | | - var request = URLRequest(url: url) |
74 | | - if let authToken = authToken { |
75 | | - request.setValue("Bearer \(authToken)", forHTTPHeaderField: "Authorization") |
76 | | - } |
77 | | - |
78 | | - self.urlSession?.downloadTask(with: request).resume() |
79 | | - } |
80 | | - } |
81 | | - |
82 | | - @discardableResult |
83 | | - func waitUntilDone() throws -> URL { |
84 | | - // It's either this, or stream the bytes ourselves (add to a buffer, save to disk, etc; boring and finicky) |
85 | | - let semaphore = DispatchSemaphore(value: 0) |
86 | | - stateSubscriber = downloadState.sink { state in |
87 | | - switch state { |
88 | | - case .completed: semaphore.signal() |
89 | | - case .failed: semaphore.signal() |
90 | | - default: break |
91 | | - } |
92 | | - } |
93 | | - semaphore.wait() |
94 | | - |
95 | | - switch downloadState.value { |
96 | | - case .completed(let url): return url |
97 | | - case .failed(let error): throw error |
98 | | - default: throw DownloadError.unexpectedError |
99 | | - } |
100 | | - } |
101 | | - |
102 | | - func cancel() { |
103 | | - urlSession?.invalidateAndCancel() |
104 | | - } |
105 | | -} |
106 | | - |
107 | | -extension Downloader: URLSessionDownloadDelegate { |
108 | | - func urlSession(_: URLSession, downloadTask: URLSessionDownloadTask, didWriteData _: Int64, totalBytesWritten: Int64, totalBytesExpectedToWrite: Int64) { |
109 | | - downloadState.value = .downloading(Double(totalBytesWritten) / Double(totalBytesExpectedToWrite)) |
110 | | - } |
111 | | - |
112 | | - func urlSession(_: URLSession, downloadTask _: URLSessionDownloadTask, didFinishDownloadingTo location: URL) { |
113 | | - do { |
114 | | - // If the downloaded file already exists on the filesystem, overwrite it |
115 | | - try FileManager.default.moveDownloadedFile(from: location, to: self.destination) |
116 | | - downloadState.value = .completed(destination) |
117 | | - } catch { |
118 | | - downloadState.value = .failed(error) |
119 | | - } |
120 | | - } |
121 | | - |
122 | | - func urlSession(_ session: URLSession, task: URLSessionTask, didCompleteWithError error: Error?) { |
123 | | - if let error = error { |
124 | | - downloadState.value = .failed(error) |
125 | | -// } else if let response = task.response as? HTTPURLResponse { |
126 | | -// print("HTTP response status code: \(response.statusCode)") |
127 | | -// let headers = response.allHeaderFields |
128 | | -// print("HTTP response headers: \(headers)") |
129 | | - } |
130 | | - } |
131 | | -} |
132 | 10 |
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133 | 11 | extension FileManager { |
134 | 12 | func moveDownloadedFile(from srcURL: URL, to dstURL: URL) throws { |
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