blob: ff5b14f9a9d166511935b06417646c47820bfdad [file] [log] [blame]
// Copyright (c) 2014, the Dart project authors. Please see the AUTHORS file
// for details. All rights reserved. Use of this source code is governed by a
// BSD-style license that can be found in the LICENSE file.
import 'handler.dart';
import 'middleware.dart';
/// A helper that makes it easy to compose a set of [Middleware] and a
/// [Handler].
/// var handler = const Pipeline()
/// .addMiddleware(loggingMiddleware)
/// .addMiddleware(cachingMiddleware)
/// .addHandler(application);
class Pipeline {
final Pipeline _parent;
final Middleware _middleware;
const Pipeline()
: _middleware = null,
_parent = null;
Pipeline._(this._middleware, this._parent);
/// Returns a new [Pipeline] with [middleware] added to the existing set of
/// [Middleware].
/// [middleware] will be the last [Middleware] to process a request and
/// the first to process a response.
Pipeline addMiddleware(Middleware middleware) =>
new Pipeline._(middleware, this);
/// Returns a new [Handler] with [handler] as the final processor of a
/// [Request] if all of the middleware in the pipeline have passed the request
/// through.
Handler addHandler(Handler handler) {
if (_middleware == null) return handler;
return _parent.addHandler(_middleware(handler));
/// Exposes this pipeline of [Middleware] as a single middleware instance.
Middleware get middleware => addHandler;