/// <summary>
/// Handles the SMTP session.
/// </summary>
/// <param name="cancellationToken">The cancellation token.</param>
/// <returns>A task which performs the operation.</returns>
async Task RunAsync(CancellationToken cancellationToken)
{
if (cancellationToken.IsCancellationRequested)
{
return;
}
await OutputGreetingAsync(cancellationToken).ConfigureAwait(false);
while (_retryCount-- > 0 && Context.IsQuitRequested == false && cancellationToken.IsCancellationRequested == false)
{
var text = await Context.Text.ReadLineAsync(cancellationToken).ConfigureAwait(false);
SmtpCommand command;
SmtpResponse errorResponse;
if (_stateMachine.TryAccept(new TokenEnumerator(new StringTokenReader(text)), out command, out errorResponse) == false)
{
await OuputErrorMessageAsync(errorResponse, cancellationToken).ConfigureAwait(false);
continue;
}
// the command was a normal command so we can reset the retry count
_retryCount = 5;
await command.ExecuteAsync(Context, cancellationToken).ConfigureAwait(false);
}
}
/// <summary>
/// Execute the command handler against the specified session context.
/// </summary>
/// <param name="context">The session context to execute the command handler against.</param>
/// <param name="cancellationToken">The cancellation token.</param>
/// <returns>A task which asynchronously performs the execution.</returns>
async Task ExecuteAsync(SmtpSessionContext context, CancellationToken cancellationToken)
{
var retries = _context.ServerOptions.MaxRetryCount;
while (retries-- > 0 && context.IsQuitRequested == false && cancellationToken.IsCancellationRequested == false)
{
try
{
var command = await ReadCommandAsync(context, cancellationToken).ConfigureAwait(false);
if (command == null)
{
return;
}
if (_stateMachine.TryAccept(command, out var errorResponse) == false)
{
throw new SmtpResponseException(errorResponse);
}
if (await ExecuteAsync(command, context, cancellationToken).ConfigureAwait(false))
{
_stateMachine.Transition(context);
}
retries = _context.ServerOptions.MaxRetryCount;
}
catch (SmtpResponseException responseException) when(responseException.IsQuitRequested)
{
await context.Pipe.Output.WriteReplyAsync(responseException.Response, cancellationToken).ConfigureAwait(false);
context.IsQuitRequested = true;
}
catch (SmtpResponseException responseException)
{
var response = CreateErrorResponse(responseException.Response, retries);
await context.Pipe.Output.WriteReplyAsync(response, cancellationToken).ConfigureAwait(false);
}
catch (OperationCanceledException)
{
await context.Pipe.Output.WriteReplyAsync(new SmtpResponse(SmtpReplyCode.ServiceClosingTransmissionChannel, "The session has be cancelled."), CancellationToken.None).ConfigureAwait(false);
}
}
}
/// <summary>
/// Advances the enumerator to the next command in the stream.
/// </summary>
/// <param name="segments">The list of array segments to read the command from.</param>
/// <param name="command">The command that was found.</param>
/// <param name="errorResponse">The error response that indicates why a command could not be accepted.</param>
/// <returns>true if a valid command was found, false if not.</returns>
bool TryAccept(IReadOnlyList <ArraySegment <byte> > segments, out SmtpCommand command, out SmtpResponse errorResponse)
{
return(_stateMachine.TryAccept(new TokenEnumerator(new ByteArrayTokenReader(segments)), out command, out errorResponse));
}
/// <summary>
/// Advances the enumerator to the next command in the stream.
/// </summary>
/// <param name="context">The session context to use when making session based transitions.</param>
/// <param name="segments">The list of array segments to read the command from.</param>
/// <param name="command">The command that was found.</param>
/// <param name="errorResponse">The error response that indicates why a command could not be accepted.</param>
/// <returns>true if a valid command was found, false if not.</returns>
bool TryAccept(SmtpSessionContext context, IReadOnlyList <ArraySegment <byte> > segments, out SmtpCommand command, out SmtpResponse errorResponse)
{
var tokenEnumerator = new TokenEnumerator(new ByteArrayTokenReader(segments));
return(_stateMachine.TryAccept(context, tokenEnumerator, out command, out errorResponse));
}