extension CloudConfiguration {
    
    static var baidu: CloudConfiguration? {
        // fulfill your baidu app info
        return nil
    }
    
    static var box: CloudConfiguration? {
        return nil
    }
    
    static var dropbox: CloudConfiguration? {
        return nil
    }
    
    static var googleDrive: CloudConfiguration? {
        return nil
    }
    
    static var oneDrive: CloudConfiguration? {
        return nil
    }
    
    static var pCloud: CloudConfiguration? {
        return nil
    }
}

let connector = DropboxConnector(appId: "your_app_id", appSecret: "your_app_secret", callbackUrl: "your_app_redirect_url")

func application(_ app: UIApplication, open url: URL, options: [UIApplication.OpenURLOptionsKey  : Any] = [:]) -> Bool {
  if url.host == "oauth-callback" {
    OAuthSwift.handle(url: url)
  }
  return true
}

import OAuthSwift

class SceneDelegate: UIResponder, UIWindowSceneDelegate {

    // ...

    func scene(_ scene: UIScene, openURLContexts URLContexts: Set
   ) {
        
        
   guard 
   let url 
   = URLContexts.
   first
   ?.
   url 
   else {
            
   return
        }
        
   if url.
   host 
   == 
   "oauth-callback" {
            OAuthSwift.
   handle(
   url: url)
        }    
    }
  

connector.connect(viewController: self) { result in
    switch result {
    case .success(let token):
        let credential = URLCredential(user: "user", password: token.credential.oauthToken, persistence: .permanent)
        // You can save token for next use.
        let provider = DropboxServiceProvider(credential: credential)
        let vc = DriveBrowserViewController(provider: provider, directory: provider.rootItem)
        self.navigationController?.pushViewController(vc, animated: true)
    case .failure(let error):
        print(error)
    }
}

    /// Get attributes of cloud item.
    /// - Parameters:
    ///   - item: The target item.
    ///   - completion: Completion callback.
    func attributesOfItem(_ item: CloudItem, completion: @escaping (Result
   Error>) 
   -> 
   Void)
    
    
   /// Load the contents at directory.

       
   /// - Parameters:

       
   ///   - directory: The target directory to load.

       
   ///   - completion: Completion callback.

       
   func 
   contentsOfDirectory(
   _ 
   directory: CloudItem, 
   completion: 
   @escaping (Result<[CloudItem], 
   Error>) 
   -> 
   Void)
    
    
   /// Copy item to directory

       
   /// - Parameters:

       
   ///   - item: The item to be copied.

       
   ///   - directory: The destination directory.

       
   ///   - completion: Completion callback.

       
   func 
   copyItem(
   _ 
   item: CloudItem, 
   to 
   directory: CloudItem, 
   completion: 
   @escaping CloudCompletionHandler)
    
    
   /// Create folder at directory.

       
   /// - Parameters:

       
   ///   - folderName: The folder to be created.

       
   ///   - directory: The destination directory.

       
   ///   - completion: Completion callback. The completion block will called in main-thread.

       
   func 
   createFolder(
   _ 
   folderName: 
   String, 
   at 
   directory: CloudItem, 
   completion: 
   @escaping CloudCompletionHandler)
    
    
   /// Get the space usage information for the current user's account.

       
   /// - Parameter completion: Completion block.

       
   func 
   getCloudSpaceInformation(
   completion: 
   @escaping (Result
   
    Error>) 
    -> 
    Void)
    
    
    /// Get information about the current user's account.

        
    /// - Parameter completion: Completion block.

        
    func 
    getCurrentUserInfo(
    completion: 
    @escaping (Result
    
     Error>) 
     -> 
     Void)
    
    
     /// Move item to target directory.

         
     /// - Parameters:

         
     ///   - item: The item to be moved.

         
     ///   - directory: The target directory.

         
     ///   - completion: Completion block.

         
     func 
     moveItem(
     _ 
     item: CloudItem, 
     to 
     directory: CloudItem, 
     completion: 
     @escaping CloudCompletionHandler)
    
    
     /// Remove cloud file/folder item.

         
     /// - Parameters:

         
     ///   - item: The item to be removed.

         
     ///   - completion: Completion block.

         
     func 
     removeItem(
     _ 
     item: CloudItem, 
     completion: 
     @escaping CloudCompletionHandler)
    
    
     /// Rename cloud file/folder to a new name.

         
     /// - Parameters:

         
     ///   - item: The item to be renamed.

         
     ///   - newName: The new name.

         
     ///   - completion: Completion block.

         
     func 
     renameItem(
     _ 
     item: CloudItem, 
     newName: 
     String, 
     completion: 
     @escaping CloudCompletionHandler)
    
    
     /// Search files with provided keyword.

         
     /// - Parameters:

         
     ///   - keyword: The keyword.

         
     ///   - completion: Completion block.

         
     func 
     searchFiles(
     keyword: 
     String, 
     completion: 
     @escaping (Result<[CloudItem], 
     Error>) 
     -> 
     Void)
    
    
     /// Upload file data to target directory.

         
     /// - Parameters:

         
     ///   - data: The data to be uploaded.

         
     ///   - filename: The filename to be created.

         
     ///   - directory: The target directory.

         
     ///   - progressHandler: The upload progress reporter. Called in main thread.

         
     ///   - completion: Completion block.

         
     func 
     uploadData(
     _ 
     data: Data, 
     filename: 
     String, 
     to 
     directory: CloudItem, 
     progressHandler: 
     @escaping ((Progress) 
     -> 
     Void), 
     completion: 
     @escaping CloudCompletionHandler)
    
    
     /// Upload file to target directory with local file url.

         
     /// Note: remote file url is not supported.

         
     /// - Parameters:

         
     ///   - fileURL: The local file url.

         
     ///   - directory: The target directory.

         
     ///   - progressHandler: The upload progress reporter. Called in main thread.

         
     ///   - completion: Completion block.

         
     func 
     uploadFile(
     _ 
     fileURL: URL, 
     to 
     directory: CloudItem, 
     progressHandler: 
     @escaping ((Progress) 
     -> 
     Void), 
     completion: 
     @escaping CloudCompletionHandler)
    
   
  

let connector = DropboxConnector(appId: "{you_app_id}", 
                                 appSecret: "{your_app_secret}", 
                                 callbackUrl: "{your_redirect_url}")

extension DropboxServiceProvider {
    
    func export(file: CloudItem, completion: @escaping CloudCompletionHandler) {
        let url = apiURL.appendingPathComponents("files/export")
        let dict = ["path": file.path]
        var headers: [String: String] = [:]
        headers["Dropbox-API-Arg"] = dropboxAPIArg(from: dict)
        post(url: url, headers: headers) { response in
            switch response.result {
            case .success(let result):
                print(result)
            case .failure(let error):
                print(error)
            }
        }
    }
}