text: // Alamofire.swift
  //
  // Copyright (c) 2014–2015 Alamofire Software Foundation (http://alamofire.org/)
  //
  // Permission is hereby granted, free of charge, to any person obtaining a copy
  // of this software and associated documentation files (the "Software"), to deal
  // in the Software without restriction, including without limitation the rights
  // to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  // copies of the Software, and to permit persons to whom the Software is
  // furnished to do so, subject to the following conditions:
  //
  // The above copyright notice and this permission notice shall be included in
  // all copies or substantial portions of the Software.
  //
  // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  // IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  // FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  // AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  // LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
  // THE SOFTWARE.
  
  import Foundation
  
  extension Manager {
      private enum Downloadable {
          case Request(NSURLRequest)
          case ResumeData(NSData)
      }
  
      private func download(downloadable: Downloadable, destination: Request.DownloadFileDestination) -> Request {
          var downloadTask: NSURLSessionDownloadTask!
  
          switch downloadable {
          case .Request(let request):
              dispatch_sync(queue) {
                  downloadTask = self.session.downloadTaskWithRequest(request)
              }
          case .ResumeData(let resumeData):
              dispatch_sync(queue) {
                  downloadTask = self.session.downloadTaskWithResumeData(resumeData)
              }
          }
  
          let request = Request(session: session, task: downloadTask)
          if let downloadDelegate = request.delegate as? Request.DownloadTaskDelegate {
              downloadDelegate.downloadTaskDidFinishDownloadingToURL = { session, downloadTask, URL in
                  return destination(URL, downloadTask.response as! NSHTTPURLResponse)
              }
          }
          delegate[request.delegate.task] = request.delegate
  
          if startRequestsImmediately {
              request.resume()
          }
  
          return request
      }
  
      // MARK: Request
  
      /**
          Creates a download request using the shared manager instance for the specified method and URL string.
  
          :param: method The HTTP method.
          :param: URLString The URL string.
          :param: destination The closure used to determine the destination of the downloaded file.
  
          :returns: The created download request.
      */
      public func download(method: Method, _ URLString: URLStringConvertible, destination: Request.DownloadFileDestination) -> Request {
          return download(URLRequest(method, URLString), destination: destination)
      }
  
      /**
          Creates a request for downloading from the specified URL request.
  
          If `startRequestsImmediately` is `true`, the request will have `resume()` called before being returned.
  
          :param: URLRequest The URL request
          :param: destination The closure used to determine the destination of the downloaded file.
  
          :returns: The created download request.
      */
      public func download(URLRequest: URLRequestConvertible, destination: Request.DownloadFileDestination) -> Request {
          return download(.Request(URLRequest.URLRequest), destination: destination)
      }
  
      // MARK: Resume Data
  
      /**
          Creates a request for downloading from the resume data produced from a previous request cancellation.
  
          If `startRequestsImmediately` is `true`, the request will have `resume()` called before being returned.
  
          :param: resumeData The resume data. This is an opaque data blob produced by `NSURLSessionDownloadTask` when a task is cancelled. See `NSURLSession -downloadTaskWithResumeData:` for additional information.
          :param: destination The closure used to determine the destination of the downloaded file.
  
          :returns: The created download request.
      */
      public func download(resumeData: NSData, destination: Request.DownloadFileDestination) -> Request {
          return download(.ResumeData(resumeData), destination: destination)
      }
  }
  
  // MARK: -
  
  extension Request {
      /**
          A closure executed once a request has successfully completed in order to determine where to move the temporary file written to during the download process. The closure takes two arguments: the temporary file URL and the URL response, and returns a single argument: the file URL where the temporary file should be moved.
      */
      public typealias DownloadFileDestination = (NSURL, NSHTTPURLResponse) -> NSURL
  
      /**
          Creates a download file destination closure which uses the default file manager to move the temporary file to a file URL in the first available directory with the specified search path directory and search path domain mask.
  
          :param: directory The search path directory. `.DocumentDirectory` by default.
          :param: domain The search path domain mask. `.UserDomainMask` by default.
  
          :returns: A download file destination closure.
      */
      public class func suggestedDownloadDestination(directory: NSSearchPathDirectory = .DocumentDirectory, domain: NSSearchPathDomainMask = .UserDomainMask) -> DownloadFileDestination {
  
          return { (temporaryURL, response) -> (NSURL) in
              if let directoryURL = NSFileManager.defaultManager().URLsForDirectory(directory, inDomains: domain)[0] as? NSURL {
                  return directoryURL.URLByAppendingPathComponent(response.suggestedFilename!)
              }
  
              return temporaryURL
          }
      }
  
      // MARK: - DownloadTaskDelegate
  
      class DownloadTaskDelegate: TaskDelegate, NSURLSessionDownloadDelegate {
          var downloadTask: NSURLSessionDownloadTask? { return task as? NSURLSessionDownloadTask }
          var downloadProgress: ((Int64, Int64, Int64) -> Void)?
  
          var resumeData: NSData?
          override var data: NSData? { return resumeData }
  
          // MARK: - NSURLSessionDownloadDelegate
  
          // MARK: Override Closures
  
          var downloadTaskDidFinishDownloadingToURL: ((NSURLSession, NSURLSessionDownloadTask, NSURL) -> NSURL)?
          var downloadTaskDidWriteData: ((NSURLSession, NSURLSessionDownloadTask, Int64, Int64, Int64) -> Void)?
          var downloadTaskDidResumeAtOffset: ((NSURLSession, NSURLSessionDownloadTask, Int64, Int64) -> Void)?
  
          // MARK: Delegate Methods
  
          func URLSession(session: NSURLSession, downloadTask: NSURLSessionDownloadTask, didFinishDownloadingToURL location: NSURL) {
              if downloadTaskDidFinishDownloadingToURL != nil {
                  let destination = downloadTaskDidFinishDownloadingToURL!(session, downloadTask, location)
                  var fileManagerError: NSError?
  
                  NSFileManager.defaultManager().moveItemAtURL(location, toURL: destination, error: &fileManagerError)
  
                  if fileManagerError != nil {
                      error = fileManagerError
                  }
              }
          }
  
          func URLSession(session: NSURLSession, downloadTask: NSURLSessionDownloadTask, didWriteData bytesWritten: Int64, totalBytesWritten: Int64, totalBytesExpectedToWrite: Int64) {
              if downloadTaskDidWriteData != nil {
                  downloadTaskDidWriteData!(session, downloadTask, bytesWritten, totalBytesWritten, totalBytesExpectedToWrite)
              } else {
                  progress.totalUnitCount = totalBytesExpectedToWrite
                  progress.completedUnitCount = totalBytesWritten
  
                  downloadProgress?(bytesWritten, totalBytesWritten, totalBytesExpectedToWrite)
              }
          }
  
          func URLSession(session: NSURLSession, downloadTask: NSURLSessionDownloadTask, didResumeAtOffset fileOffset: Int64, expectedTotalBytes: Int64) {
              if downloadTaskDidResumeAtOffset != nil {
                  downloadTaskDidResumeAtOffset!(session, downloadTask, fileOffset, expectedTotalBytes)
              } else {
                  progress.totalUnitCount = expectedTotalBytes
                  progress.completedUnitCount = fileOffset
              }
          }
      }
  }
  