Move common streams in barback to their own class.

pkg/barback/lib/src/asset_cascade.dart

 // Copyright (c) 2013, 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.asset_cascade;
 
 import 'dart:async';
 
 import 'asset.dart';
 import 'asset_id.dart';
 import 'asset_node.dart';
 import 'asset_set.dart';
 import 'log.dart';
 import 'cancelable_future.dart';
 import 'errors.dart';
+import 'node_streams.dart';
 import 'package_graph.dart';
 import 'phase.dart';
-import 'stream_pool.dart';
 import 'transformer.dart';
 
 /// The asset cascade for an individual package.
 ///
 /// This keeps track of which [Transformer]s are applied to which assets, and
 /// re-runs those transformers when their dependencies change. The transformed
 /// asset nodes are accessible via [getAssetNode].
 ///
 /// A cascade consists of one or more [Phases], each of which has one or more
 /// [Transformer]s that run in parallel, potentially on the same inputs. The
@@ skipping 31 matching lines @@
   StreamSubscription _phaseOnDoneSubscription;
 
   /// A stream that emits any errors from the cascade or the transformers.
   ///
   /// This emits errors as they're detected. If an error occurs in one part of
   /// the cascade, unrelated parts will continue building.
   Stream<BarbackException> get errors => _errorsController.stream;
   final _errorsController =
       new StreamController<BarbackException>.broadcast(sync: true);
 
-  /// A stream that emits an event whenever any transforms in this cascade logs
-  /// an entry.
-  Stream<LogEntry> get onLog => _onLogPool.stream;
-  final _onLogPool = new StreamPool<LogEntry>.broadcast();
-
   /// Whether [this] is dirty and still has more processing to do.
   bool get isDirty {
     // Just check the last phase, since it will check all the previous phases
     // itself.
     return _phases.last.isDirty;
   }
 
-  /// A stream that emits an event whenever [this] is no longer dirty.
-  ///
-  /// This is synchronous in order to guarantee that it will emit an event as
-  /// soon as [isDirty] flips from `true` to `false`.
-  Stream get onDone => _onDoneController.stream;
-  final _onDoneController = new StreamController.broadcast(sync: true);
+  /// The streams exposed by this cascade.
+  final _streams = new NodeStreams();
+  Stream<LogEntry> get onLog => _streams.onLog;
+  Stream get onDone => _streams.onDone;
 
   /// Returns all currently-available output assets from this cascade.
   AssetSet get availableOutputs =>
     new AssetSet.from(_phases.last.availableOutputs.map((node) => node.asset));
 
   /// Creates a new [AssetCascade].
   ///
   /// It loads source assets within [package] using [provider].
   AssetCascade(this.graph, this.package) {
     _addPhase(new Phase(this, package));
@@ skipping 94 matching lines @@
       phase.updateTransformers(transformers[i]);
     }
 
     for (var i = transformers.length + 1; i < _phases.length; i++) {
       _phases[i].remove();
     }
     _phases.removeRange(transformers.length + 1, _phases.length);
 
     _phaseOnDoneSubscription.cancel();
     _phaseOnDoneSubscription = _phases.last.onDone
-        .listen(_onDoneController.add);
+        .listen(_streams.onDoneController.add);
   }
 
   /// Force all [LazyTransformer]s' transforms in this cascade to begin
   /// producing concrete assets.
   void forceAllTransforms() {
     for (var phase in _phases) {
       phase.forceAllTransforms();
     }
   }
 
   void reportError(BarbackException error) {
     _errorsController.add(error);
   }
 
   /// Add [phase] to the end of [_phases] and watch its streams.
   void _addPhase(Phase phase) {
-    _onLogPool.add(phase.onLog);
+    _streams.onLogPool.add(phase.onLog);
     if (_phaseOnDoneSubscription != null) _phaseOnDoneSubscription.cancel();
-    _phaseOnDoneSubscription = phase.onDone.listen(_onDoneController.add);
+    _phaseOnDoneSubscription =
+        phase.onDone.listen(_streams.onDoneController.add);
 
     _phases.add(phase);
   }
 
   String toString() => "cascade for $package";
 }