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barback/lib/src/graph/phase_forwarder.dart

Index: barback/lib/src/graph/phase_forwarder.dart
diff --git a/barback/lib/src/graph/phase_forwarder.dart b/barback/lib/src/graph/phase_forwarder.dart
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index e70aff310b61d86412e532f8069b1d0df1db2b6f..0000000000000000000000000000000000000000
--- a/barback/lib/src/graph/phase_forwarder.dart
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-// 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.graph.phase_forwarder;
-
-import 'dart:async';
-
-import '../asset/asset_node.dart';
-import '../asset/asset_node_set.dart';
-
-/// A class that takes care of forwarding assets within a phase.
-///
-/// Each phase contains one or more channels that process its input assets. Each
-/// non-grouped transformer for that phase is a channel, each [TransformerGroup]
-/// in that phase is another, and the source node is the final channel. For each
-/// input asset, each channel individually decides whether to forward that asset
-/// based on whether that channel uses it. If a channel does decide to forward
-/// an asset, we call that forwarded asset an "intermediate forwarded asset" to
-/// distinguish it from the output of a [PhaseForwarder].
-///
-/// All intermediate assets with a given origin are provided to a single
-/// [PhaseForwarder] via [addIntermediateAsset]. This forwarder then determines
-/// whether all channels in the phase produced intermediate assets. If so, that
-/// means the input asset wasn't consumed by any channel, so the
-/// [PhaseForwarder] forwards it again, producing an output which we'll call the
-/// "final forwarded asset".
-///
-/// A final forwarded asset will be available only if all of the intermediate
-/// forwarded assets are themselves available. If any of the intermediate assets
-/// are dirty, the final asset will also be marked dirty.
-class PhaseForwarder {
-  /// The number of channels to forward, counting the source node.
-  int _numChannels;
-
-  /// The intermediate forwarded assets.
-  final _intermediateAssets = new AssetNodeSet();
-
-  /// The final forwarded asset.
-  ///
-  /// This will be null if the asset is not being forwarded.
-  AssetNode get output =>
-      _outputController == null ? null : _outputController.node;
-  AssetNodeController _outputController;
-
-  /// A stream that emits an event whenever [this] starts producing a final
-  /// forwarded asset.
-  ///
-  /// Whenever this stream emits an event, the value will be identical to
-  /// [output].
-  Stream<AssetNode> get onAsset => _onAssetController.stream;
-  final _onAssetController =
-      new StreamController<AssetNode>.broadcast(sync: true);
-
-  /// Creates a phase forwarder forwarding nodes that come from [node] across
-  /// [numTransformers] transformers and [numGroups] groups.
-  ///
-  /// [node] is passed in explicitly so that it can be forwarded if there are no
-  /// other channels.
-  PhaseForwarder(AssetNode node, int numTransformers, int numGroups)
-      : _numChannels = numTransformers + numGroups + 1 {
-    addIntermediateAsset(node);
-  }
-
-  /// Notify the forwarder that the number of transformer and group channels has
-  /// changed.
-  void updateTransformers(int numTransformers, int numGroups) {
-    // Add one channel for the source node.
-    _numChannels = numTransformers + numGroups + 1;
-    _adjustOutput();
-  }
-
-  /// Adds an intermediate forwarded asset to [this].
-  ///
-  /// [asset] must have the same origin as all other intermediate forwarded
-  /// assets.
-  void addIntermediateAsset(AssetNode asset) {
-    if (_intermediateAssets.isNotEmpty) {
-      assert(asset.origin == _intermediateAssets.first.origin);
-    }
-
-    _intermediateAssets.add(asset);
-    asset.onStateChange.listen((_) => _adjustOutput());
-
-    _adjustOutput();
-  }
-
-  /// Mark this forwarder as removed.
-  ///
-  /// This will remove [output] if it exists.
-  void remove() {
-    if (_outputController != null) {
-      _outputController.setRemoved();
-      _outputController = null;
-    }
-    _onAssetController.close();
-  }
-
-  /// Adjusts [output] to ensure that it accurately reflects the current state
-  /// of the intermediate forwarded assets.
-  void _adjustOutput() {
-    assert(_intermediateAssets.length <= _numChannels);
-    assert(!_intermediateAssets.any((asset) => asset.state.isRemoved));
-
-    // If there are any channels that haven't forwarded an intermediate asset,
-    // we shouldn't forward a final asset. If we are currently, remove
-    // it.
-    if (_intermediateAssets.length < _numChannels) {
-      if (_outputController == null) return;
-      _outputController.setRemoved();
-      _outputController = null;
-      return;
-    }
-
-    // If there isn't a final asset being forwarded yet, we should forward one.
-    // It should be dirty iff any of the intermediate assets are dirty.
-    if (_outputController == null) {
-      var finalAsset = _intermediateAssets.firstWhere(
-          (asset) => asset.state.isDirty,
-          orElse: () => _intermediateAssets.first);
-      _outputController = new AssetNodeController.from(finalAsset);
-      _onAssetController.add(output);
-      return;
-    }
-
-    // If we're already forwarding a final asset, set it dirty iff any of the
-    // intermediate assets are dirty.
-    if (_intermediateAssets.any((asset) => asset.state.isDirty)) {
-      if (!_outputController.node.state.isDirty) _outputController.setDirty();
-    } else if (!_outputController.node.state.isAvailable) {
-      _outputController.setAvailable(_intermediateAssets.first.asset);
-    }
-  }
-}