Ole André Vadla Ravnås
9a545579f7
A rejected response became a file-does-not-exist error, and both libraries then threw the cause away and guessed at it: a refused agent was reported as one nobody had published. Name the status the server answered, and carry it through.
86 lines
2.8 KiB
Swift
86 lines
2.8 KiB
Swift
import Foundation
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#if canImport(FoundationNetworking)
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import FoundationNetworking
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#endif
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final class ProgressiveDownload: NSObject, URLSessionDownloadDelegate, @unchecked Sendable {
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static func fetch(
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_ url: URL,
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reporting report: @escaping @Sendable (Double?) -> Void
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) async throws -> URL {
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let delegate = ProgressiveDownload(report: report)
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let session = URLSession(configuration: .default, delegate: delegate, delegateQueue: nil)
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defer { session.finishTasksAndInvalidate() }
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return try await withCheckedThrowingContinuation { continuation in
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delegate.continuation = continuation
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session.downloadTask(with: url).resume()
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}
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}
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private let report: @Sendable (Double?) -> Void
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private var continuation: CheckedContinuation<URL, any Error>?
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private var lastReported: Double = 0
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private init(report: @escaping @Sendable (Double?) -> Void) {
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self.report = report
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}
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func urlSession(
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_ session: URLSession,
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downloadTask: URLSessionDownloadTask,
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didWriteData bytesWritten: Int64,
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totalBytesWritten: Int64,
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totalBytesExpectedToWrite: Int64
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) {
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guard totalBytesExpectedToWrite > 0 else {
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report(nil)
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return
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}
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let fraction = Double(totalBytesWritten) / Double(totalBytesExpectedToWrite)
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guard fraction - lastReported >= 0.01 || fraction == 1 else { return }
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lastReported = fraction
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report(fraction)
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}
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func urlSession(
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_ session: URLSession,
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downloadTask: URLSessionDownloadTask,
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didFinishDownloadingTo location: URL
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) {
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let result: Result<URL, any Error>
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if let http = downloadTask.response as? HTTPURLResponse, http.statusCode != 200 {
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result = .failure(DownloadError.rejected(status: http.statusCode))
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} else {
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let kept = FileManager.default.temporaryDirectory
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.appendingPathComponent(UUID().uuidString, isDirectory: false)
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result = Result { try FileManager.default.moveItem(at: location, to: kept) }
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.map { kept }
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}
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continuation?.resume(with: result)
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continuation = nil
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}
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func urlSession(
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_ session: URLSession,
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task: URLSessionTask,
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didCompleteWithError error: (any Error)?
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) {
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guard let error else { return }
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continuation?.resume(throwing: error)
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continuation = nil
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}
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}
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enum DownloadError: Swift.Error, LocalizedError {
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case rejected(status: Int)
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var errorDescription: String? {
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switch self {
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case .rejected(let status):
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return "the server answered \(status) \(HTTPURLResponse.localizedString(forStatusCode: status))"
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}
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}
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}
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