Add support for transformer clusters to barback.

pkg/barback/lib/src/phase.dart

Index: pkg/barback/lib/src/phase.dart
diff --git a/pkg/barback/lib/src/phase.dart b/pkg/barback/lib/src/phase.dart
index 1230bea094e36970d402547ec6b386c868c33ec0..dbafc87d7f00b5721cc7cf98244906cd2a73ca4f 100644
--- a/pkg/barback/lib/src/phase.dart
+++ b/pkg/barback/lib/src/phase.dart
@@ -11,11 +11,15 @@ import 'asset_cascade.dart';
 import 'asset_id.dart';
 import 'asset_node.dart';
 import 'asset_set.dart';
+import 'cluster_runner.dart';
 import 'errors.dart';
+import 'operator.dart';
+import 'phase_forwarder.dart';
 import 'phase_input.dart';
 import 'phase_output.dart';
 import 'stream_pool.dart';
 import 'transformer.dart';
+import 'transformer_cluster.dart';
 import 'utils.dart';
 
 /// One phase in the ordered series of transformations in an [AssetCascade].
@@ -39,15 +43,38 @@ class Phase {
   /// Their outputs will be available to the next phase.
   final Set<Transformer> _transformers;
 
+  /// The clusters for this phase.
+  final _clusters = new Map<TransformerCluster, ClusterRunner>();
+
   /// The inputs for this phase.
   ///
   /// For the first phase, these will be the source assets. For all other
   /// phases, they will be the outputs from the previous phase.
   final _inputs = new Map<AssetId, PhaseInput>();
 
+  /// The forwarders for this phase.
+  final _forwarders = new Map<AssetId, PhaseForwarder>();
+
   /// The outputs for this phase.
   final _outputs = new Map<AssetId, PhaseOutput>();
 
+  // TODO(nweiz): don't re-calculate this on the fly all the time

[Bob Nystrom, 2013/10/04 21:47:50]

"." and capitalize "Don't".

[nweiz, 2013/10/07 23:21:31]

Done.

+  /// The set of all [AssetNode.origin] properties of the input assets for this
+  /// phase.
+  ///
+  /// This is used to determine which assets have been passed unmodified through
+  /// [_inputs] or [_clusters]. Eeach input asset has a PhaseInput in [_inputs].

[Bob Nystrom, 2013/10/04 21:47:50]

"Eeach" -> "Each".

[nweiz, 2013/10/07 23:21:31]

Done.

+  /// If that input isn't consumed by any transformers, it will be forwarded
+  /// through the PhaseInput. However, it's possible that it was consumed by a
+  /// cluster, and so shouldn't be forwarded through the phase as a whole.
+  ///
+  /// In order to detect whether an output has been forwarded through a cluster
+  /// or a PhaseInput, we must be able to distinguish it from other outputs with
+  /// the same id. To do so, we check if its origin is in [_inputOrigins]. If
+  /// so, it's been forwarded unmodified.
+  Set<AssetNode> get _inputOrigins =>
+    _inputs.values.map((input) => input.input.origin).toSet();
+
   /// A stream that emits an event whenever this phase becomes dirty and needs
   /// to be run.
   ///
@@ -62,6 +89,10 @@ class Phase {
   /// This is used whenever an input is added or transforms are changed.
   final _onDirtyController = new StreamController.broadcast(sync: true);
 
+  /// Whether this phase is dirty and needs to be run.
+  bool get isDirty => _inputs.values.any((input) => input.isDirty) ||
+      _clusters.values.any((cluster) => cluster.isDirty);
+
   /// The phase after this one.
   ///
   /// Outputs from this phase will be passed to it.
@@ -69,16 +100,21 @@ class Phase {
   Phase _next;
 
   /// Returns all currently-available output assets for this phase.
-  AssetSet get availableOutputs {
-    return new AssetSet.from(_outputs.values
+  Set<AssetNode> get availableOutputs {
+    return _outputs.values
         .map((output) => output.output)
         .where((node) => node.state.isAvailable)
-        .map((node) => node.asset));
+        .toSet();
   }
 
-  Phase(this.cascade, Iterable<Transformer> transformers)
-      : _transformers = transformers.toSet() {
+  Phase(this.cascade, Iterable<Operator> operators)

[Bob Nystrom, 2013/10/04 21:47:50]

We could keep this API typed if the transformers and clusters were split out
before calling this and were passed in as two separate collections. Do that?

[nweiz, 2013/10/07 23:21:31]

I think that would result in more code duplication -- we'd need to do that
splitting both places we call [new Phase].

+      : _transformers = operators.where((op) => op is Transformer).toSet() {
     _onDirtyPool.add(_onDirtyController.stream);
+
+    for (var cluster in operators.where((op) => op is TransformerCluster)) {
+      _clusters[cluster] = new ClusterRunner(cascade, cluster);
+      _onDirtyPool.add(_clusters[cluster].onDirty);
+    }
   }
 
   /// Adds a new asset as an input for this phase.
@@ -94,11 +130,27 @@ class Phase {
   void addInput(AssetNode node) {
     if (_inputs.containsKey(node.id)) _inputs[node.id].remove();
 
+    var forwarder = new PhaseForwarder(_clusters.length + 1);

[Bob Nystrom, 2013/10/04 21:47:50]

Explain what the .length + 1 represents.

[nweiz, 2013/10/07 23:21:31]

Done.

+    _forwarders[node.id] = forwarder;
+    forwarder.onForwarding.listen((asset) {
+      _addOutput(asset);
+
+      var exception = _outputs[asset.id].collisionException;
+      if (exception != null) cascade.reportError(exception);
+    });
+
     var input = new PhaseInput(this, node, _transformers);
     _inputs[node.id] = input;
-    input.input.whenRemoved.then((_) => _inputs.remove(node.id));
+    input.input.whenRemoved.then((_) {
+      _inputs.remove(node.id);
+      _forwarders.remove(node.id).remove();
+    });
     _onDirtyPool.add(input.onDirty);
     _onDirtyController.add(null);
+
+    for (var cluster in _clusters.values) {
+      cluster.addInput(node);
+    }
   }
 
   /// Gets the asset node for an input [id].
@@ -123,22 +175,42 @@ class Phase {
     });
   }
 
-  /// Set this phase's transformers to [transformers].
-  void updateTransformers(Iterable<Transformer> transformers) {
+  /// Set this phase's operators to [operators].
+  void updateOperators(Iterable<Operator> operators) {
     _onDirtyController.add(null);
+
+    var transformers = operators.where((op) => op is Transformer);
     _transformers.clear();
     _transformers.addAll(transformers);
     for (var input in _inputs.values) {
-      input.updateTransformers(_transformers);
+      input.updateTransformers(transformers);
+    }
+
+    var newClusters = operators.where((op) => op is TransformerCluster).toSet();
+    var oldClusters = _clusters.keys.toSet();
+    for (var removed in oldClusters.difference(newClusters)) {
+      _clusters.remove(removed).remove();
+    }

[Bob Nystrom, 2013/10/04 21:47:50]

Nit but add blank line after "}".

[nweiz, 2013/10/07 23:21:31]

Done.

+    for (var added in newClusters.difference(oldClusters)) {
+      var runner = new ClusterRunner(cascade, added);
+      _clusters[added] = runner;
+      _onDirtyPool.add(runner.onDirty);
+      for (var input in _inputs.values) {
+        runner.addInput(input.input);
+      }
+    }
+
+    for (var forwarder in _forwarders.values) {
+      forwarder.channels = _clusters.length + 1;
     }
   }
 
-  /// Add a new phase after this one with [transformers].
+  /// Add a new phase after this one with [operators].
   ///
   /// This may only be called on a phase with no phase following it.
-  Phase addPhase(Iterable<Transformer> transformers) {
+  Phase addPhase(Iterable<Operators> operators) {
     assert(_next == null);
-    _next = new Phase(cascade, transformers);
+    _next = new Phase(cascade, operators);
     for (var output in _outputs.values.toList()) {
       // Remove [output]'s listeners because now they should get the asset from
       // [_next], rather than this phase. Any transforms consuming [output] will
@@ -162,6 +234,9 @@ class Phase {
     for (var input in _inputs.values.toList()) {
       input.remove();
     }
+    for (var cluster in _clusters.values) {
+      cluster.remove();
+    }
     _onDirtyPool.close();
   }
 
@@ -177,26 +252,32 @@ class Phase {
   /// Returns a future that completes when processing is done. If there is
   /// nothing to process, returns `null`.
   Future process() {
-    if (!_inputs.values.any((input) => input.isDirty)) return null;
+    if (!isDirty) return null;
 
     var outputIds = new Set<AssetId>();
-    return Future.wait(_inputs.values.map((input) {
-      if (!input.isDirty) return new Future.value(new Set());
-      return input.process().then((outputs) {
-        for (var asset in outputs) {
-          outputIds.add(asset.id);
-          if (_outputs.containsKey(asset.id)) {
-            _outputs[asset.id].add(asset);
-          } else {
-            _outputs[asset.id] = new PhaseOutput(this, asset);
-            _outputs[asset.id].output.whenRemoved.then((_) {
-              _outputs.remove(asset.id);
-            });
-            if (_next != null) _next.addInput(_outputs[asset.id].output);
-          }
+    void _handleOutputs(Set<AssetNode> outputs) {
+      for (var asset in outputs) {
+        if (_inputOrigins.contains(asset.origin)) {
+          _forwarders[asset.id].add(asset);
+          continue;
         }
-      });
-    })).then((_) {
+
+        outputIds.add(asset.id);
+        _addOutput(asset);
+      }
+    }
+
+    var outputFutures = []..addAll(_inputs.values.map((input) {
+      if (!input.isDirty) return new Future.value(new Set());
+      return input.process().then(_handleOutputs);
+    }))..addAll(_clusters.values.map((input) {

[Bob Nystrom, 2013/10/04 21:47:50]

Maybe it's just me, but using ".." here feels a bit gratuitous with multi-line
maps too. How about just:

var outputFutures = _inputs.values.map(...).toList();

outputFutures.addAll(_clusters.values.map(...));

[nweiz, 2013/10/07 23:21:31]

Done.

+      if (!input.isDirty) return new Future.value(new Set());
+      return input.process().then(_handleOutputs);
+    }));
+
+    // TODO(nweiz): handle pass-through.
+
+    return Future.wait(outputFutures).then((_) {
       // Report collisions in a deterministic order.
       outputIds = outputIds.toList();
       outputIds.sort((a, b) => a.compareTo(b));
@@ -209,4 +290,17 @@ class Phase {
       }
     });
   }
+
+  /// Add [asset] as an output of this phase.
+  void _addOutput(AssetNode asset) {
+    if (_outputs.containsKey(asset.id)) {
+      _outputs[asset.id].add(asset);
+    } else {
+      _outputs[asset.id] = new PhaseOutput(this, asset);
+      _outputs[asset.id].output.whenRemoved.then((_) {
+        _outputs.remove(asset.id);
+      });
+      if (_next != null) _next.addInput(_outputs[asset.id].output);
+    }
+  }
 }