private Task SimplifiedTransferRequest(TransferMethod method, string fileName, string directory, string channelPassword, bool overwrite, bool resume, CancellationToken cancellationToken)
{
TaskCompletionSource <Error> taskCompletionSource = new TaskCompletionSource <Error>();
// check if task is already canceled.
if (cancellationToken.IsCancellationRequested)
{
// if yes, exit early.
taskCompletionSource.SetCanceled();
return(taskCompletionSource.Task);
}
// the return code can show up in FileTransferStatusReceived, and ServerError.
// and both can signal the end of the operation.
// that is why ServerError is mapped on to the handler for FileTransferStatusReceived
// this way, the clean up code has to be written once.
// CancellationToken does not directly signal the abort, but instead calls TryHaltTransfer.
// which will result in a FileTransferStatusReceived.
FileTransfer self = null;
Task startTask;
string returnCode = Connection.GetNextReturnCode(out startTask);
// = null, to make the c# compiler happy.
FileTransferStatusEventHandler eventHandler = null;
eventHandler = (transfer, status) =>
{
if (transfer != self)
{
return;
}
// any event for transfer signals the end of the operation
Connection.FileTransferStatusReceived -= eventHandler;
// translate the error code into task state
switch (status)
{
case Error.FileTransferComplete: taskCompletionSource.SetResult(Error.Ok); break;
case Error.FileTransferCanceled: taskCompletionSource.SetCanceled(); break;
default: taskCompletionSource.SetException(Library.CreateException(status)); break;
}
};
startTask.ContinueWith(antecendent =>
{
// failed to initiate a transfer
Connection.FileTransferStatusReceived -= eventHandler;
// pass exception to user
taskCompletionSource.SetException(antecendent.Exception);
}, cancellationToken, TaskContinuationOptions.OnlyOnFaulted, TaskScheduler.Current);
Connection.FileTransferStatusReceived += eventHandler;
self = method(this, channelPassword, fileName, overwrite, resume, directory, returnCode);
if (cancellationToken != CancellationToken.None)
{
// register cancellationToken
cancellationToken.Register(() => Library.Api.TryHaltTransfer(self, true, null));
}
return(taskCompletionSource.Task);
}