Reorganize barback's source files.

pkg/barback/lib/src/node_streams.dart

-// 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.
-
-library barback.node_streams;
-
-import 'dart:async';
-
-import 'asset_node.dart';
-import 'log.dart';
-import 'node_status.dart';
-import 'stream_pool.dart';
-
-/// A collection of streams that are common to nodes in barback's package graph.
-class NodeStreams {
-  /// A stream that emits an event every time the node's status changes.
-  ///
-  /// This will emit the new status. It's guaranteed to emit an event only when
-  /// the status changes from the previous value. To ensure this, callers should
-  /// emit status changes using [changeStatus]. The initial status is assumed to
-  /// be [NodeStatus.RUNNING].
-  Stream<NodeStatus> get onStatusChange => _onStatusChangeController.stream;
-  final _onStatusChangeController =
-      new StreamController<NodeStatus>.broadcast(sync: true);
-
-  /// A stream that emits any new assets produced by the node.
-  ///
-  /// Assets are emitted synchronously to ensure that any changes are thoroughly
-  /// propagated as soon as they occur.
-  Stream<AssetNode> get onAsset => onAssetPool.stream;
-  final onAssetPool = new StreamPool<AssetNode>.broadcast();
-  final onAssetController =
-      new StreamController<AssetNode>.broadcast(sync: true);
-
-  /// A stream that emits an event whenever any the node logs an entry.
-  Stream<LogEntry> get onLog => onLogPool.stream;
-  final onLogPool = new StreamPool<LogEntry>.broadcast();
-  final onLogController = new StreamController<LogEntry>.broadcast(sync: true);
-
-  var _previousStatus = NodeStatus.RUNNING;
-
-  /// Whether [this] has been closed.
-  bool get isClosed => onAssetController.isClosed;
-
-  NodeStreams() {
-    onAssetPool.add(onAssetController.stream);
-    onLogPool.add(onLogController.stream);
-  }
-
-  /// Emits a status change notification via [onStatusChange].
-  ///
-  /// This guarantees that a change notification won't be emitted if the status
-  /// didn't actually change.
-  void changeStatus(NodeStatus status) {
-    if (_previousStatus != status) _onStatusChangeController.add(status);
-  }
-
-  /// Closes all the streams.
-  void close() {
-    _onStatusChangeController.close();
-    onAssetController.close();
-    onAssetPool.close();
-    onLogController.close();
-    onLogPool.close();
-  }
-}