actor async/await download imge Swift 5.5

actor_dl_imge.swift

extension UIImage {
    @available(iOS 15, *)
    var thumbnail: UIImage? {
        get async {
            let size = CGSize(width: 80, height: 40)
            return await self.byPreparingThumbnail(ofSize: size)
        }
    }
}
enum FetchError:Error{
    case badID
    case badImage
    
}
actor ImageDownloader {
    
    private enum CacheEntry {
        case inProgress(Task.Handle<Image, Error>)
        case ready(Image)
    }
    
    private var cache: [URL: CacheEntry] = [:]
    
    func image(from url: URL) async throws -> Image? {
        if let cached = cache[url] {
            switch cached {
                case .ready(let image):
                    return image
                case .inProgress(let handle):
                    return try await handle.get()
            }
        }
        
        let handle = async {
            try await downloadImage(from: url)
        }
        
        cache[url] = .inProgress(handle)
        
        do {
            let image = try await handle.get()
            cache[url] = .ready(image)
            return image
        } catch {
            cache[url] = nil
            throw error
        }
    }
    //URL.init(string:"https://www.apple.com/v/home/hc/images/overview/ios15_logo__cnpdxsz7otzm_large_2x.png")!)
    func downloadImage(from url:URL) async throws -> Image{
        let request = URLRequest.init(url:url)
        let (data, response) = try await URLSession.shared.data(for: request)
        guard (response as? HTTPURLResponse)?.statusCode == 200 else { throw FetchError.badID }
        let maybeImage = UIImage(data: data)
        guard let thumbnail = await maybeImage?.thumbnail else { throw FetchError.badImage }
        return  Image(uiImage: thumbnail)
    }
}