Update API [skip ci]

submodules/WebUI/Sources/FileDownload.swift

@@ -0,0 +1,75 @@
+import Foundation
+import SwiftSignalKit
+
+final class FileDownload: NSObject, URLSessionDownloadDelegate {
+    private let fileSize: Int64?
+    private var urlSession: URLSession!
+    private var completion: ((URL?, Error?) -> Void)?
+    private var progressHandler: ((Double) -> Void)?
+    
+    init(from url: URL, fileSize: Int64?, progressHandler: @escaping (Double) -> Void, completion: @escaping (URL?, Error?) -> Void) {
+        self.progressHandler = progressHandler
+        self.fileSize = fileSize
+        self.completion = completion
+        
+        
+        super.init()
+        
+        let configuration = URLSessionConfiguration.default
+        urlSession = URLSession(configuration: configuration, delegate: self, delegateQueue: OperationQueue.main)
+        
+        let downloadTask = self.urlSession.downloadTask(with: url)
+        downloadTask.resume()
+    }
+    
+    func urlSession(_ session: URLSession, downloadTask: URLSessionDownloadTask, didWriteData bytesWritten: Int64, totalBytesWritten: Int64, totalBytesExpectedToWrite: Int64) {
+        var totalBytesExpectedToWrite = totalBytesExpectedToWrite
+        if totalBytesExpectedToWrite == -1, let fileSize = self.fileSize {
+            totalBytesExpectedToWrite = fileSize
+        }
+        let progress = Double(totalBytesWritten) / Double(totalBytesExpectedToWrite)
+        progressHandler?(progress)
+    }
+    
+    func urlSession(_ session: URLSession, downloadTask: URLSessionDownloadTask, didFinishDownloadingTo location: URL) {
+        completion?(location, nil)
+    }
+    
+    func urlSession(_ session: URLSession, task: URLSessionTask, didCompleteWithError error: Error?) {
+        if let error = error {
+            completion?(nil, error)
+        }
+    }
+    
+    static func getFileSize(url: String) -> Signal<Int64?, NoError> {
+        if #available(iOS 13.0, *) {
+            guard let url = URL(string: url) else {
+                return .single(nil)
+            }
+            var request = URLRequest(url: url)
+            request.httpMethod = "HEAD"
+            
+            return Signal { subscriber in
+                let task = URLSession.shared.dataTask(with: request) { _, response, error in
+                    if let _ = error {
+                        subscriber.putNext(nil)
+                        subscriber.putCompletion()
+                        return
+                    }
+                    var fileSize: Int64?
+                    if let httpResponse = response as? HTTPURLResponse, let contentLength = httpResponse.value(forHTTPHeaderField: "Content-Length"), let size = Int64(contentLength) {
+                        fileSize = size
+                    }
+                    subscriber.putNext(fileSize)
+                    subscriber.putCompletion()
+                }
+                task.resume()
+                return ActionDisposable {
+                    task.cancel()
+                }
+            }
+        } else {
+            return .single(nil)
+        }
+    }
+}