Use FileDownloadDelegate from the AHC package (#171)

`FileDownloadDelegate` was introduced in https://github.com/swift-server/async-http-client/pull/275, which almost directly mirrors the implementation in `carton`. Now that it's available in a released version of AHC, let's delete some code here and replace it with the version from that package.

Package.swift

@@ -13,7 +13,7 @@ let package = Package(
   name: "carton",
   platforms: [.macOS(.v10_15)],
   dependencies: [
-    .package(url: "https://github.com/swift-server/async-http-client.git", from: "1.1.1"),
+    .package(url: "https://github.com/swift-server/async-http-client.git", from: "1.2.2"),
     .package(
       url: "https://github.com/apple/swift-argument-parser.git",
       .upToNextMinor(from: "0.3.0")

Sources/SwiftToolchain/FileDownloadDelegate.swift

@@ -1,81 +0,0 @@
-// Copyright 2020 Carton contributors
-//
-// Licensed under the Apache License, Version 2.0 (the "License");
-// you may not use this file except in compliance with the License.
-// You may obtain a copy of the License at
-//
-//     http://www.apache.org/licenses/LICENSE-2.0
-//
-// Unless required by applicable law or agreed to in writing, software
-// distributed under the License is distributed on an "AS IS" BASIS,
-// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-// See the License for the specific language governing permissions and
-// limitations under the License.
-
-import AsyncHTTPClient
-import NIO
-import NIOHTTP1
-
-final class FileDownloadDelegate: HTTPClientResponseDelegate {
-  typealias Response = (totalBytes: Int?, receivedBytes: Int)
-
-  private var totalBytes: Int?
-  private var receivedBytes = 0
-
-  private let handle: NIOFileHandle
-  private let io: NonBlockingFileIO
-  private let reportHead: ((HTTPResponseHead) -> ())?
-  private let reportProgress: ((_ totalBytes: Int?, _ receivedBytes: Int) -> ())?
-
-  private var writeFuture: EventLoopFuture<()>?
-
-  init(
-    path: String,
-    pool: NIOThreadPool = NIOThreadPool(numberOfThreads: 1),
-    reportHead: ((HTTPResponseHead) -> ())? = nil,
-    reportProgress: ((_ totalBytes: Int?, _ receivedBytes: Int) -> ())? = nil
-  ) throws {
-    handle = try NIOFileHandle(path: path, mode: .write, flags: .allowFileCreation())
-    pool.start()
-    io = NonBlockingFileIO(threadPool: pool)
-
-    self.reportHead = reportHead
-    self.reportProgress = reportProgress
-  }
-
-  func didReceiveHead(
-    task: HTTPClient.Task<Response>,
-    _ head: HTTPResponseHead
-  ) -> EventLoopFuture<()> {
-    reportHead?(head)
-
-    if let totalBytesString = head.headers.first(name: "Content-Length"),
-       let totalBytes = Int(totalBytesString)
-    {
-      self.totalBytes = totalBytes
-    }
-
-    return task.eventLoop.makeSucceededFuture(())
-  }
-
-  func didReceiveBodyPart(
-    task: HTTPClient.Task<Response>,
-    _ buffer: ByteBuffer
-  ) -> EventLoopFuture<()> {
-    receivedBytes += buffer.readableBytes
-    reportProgress?(totalBytes, receivedBytes)
-
-    let writeFuture = io.write(fileHandle: handle, buffer: buffer, eventLoop: task.eventLoop)
-    self.writeFuture = writeFuture
-    return writeFuture
-  }
-
-  func didFinishRequest(task: HTTPClient.Task<Response>) throws -> Response {
-    writeFuture?.whenComplete { [weak self] _ in
-      // swiftlint:disable:next force_try
-      try! self?.handle.close()
-      self?.writeFuture = nil
-    }
-    return (totalBytes, receivedBytes)
-  }
-}

Sources/SwiftToolchain/ToolchainInstallation.swift

@@ -124,8 +124,8 @@ extension ToolchainSystem {
       },
       reportProgress: {
         subject.send(.init(
-          step: $1,
-          total: $0 ?? expectedArchiveSize,
+          step: $0.receivedBytes,
+          total: $0.totalBytes ?? expectedArchiveSize,
           text: "saving to \(path)"
         ))
       }