pkg/barback/lib/src/group_runner.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.group_runner;

import 'dart:async';

import 'asset_cascade.dart';
import 'asset_node.dart';
import 'log.dart';
import 'phase.dart';
import 'stream_pool.dart';
import 'transformer_group.dart';

/// A class that processes all of the phases in a single transformer group.
///
/// A group takes many inputs, processes them, and emits many outputs.
class GroupRunner {
  /// The group this runner runs.
  final TransformerGroup _group;

  /// A string describing the location of [this] in the transformer graph.
  final String _location;

  /// The phases defined by this group.
  final _phases = new List<Phase>();

  /// 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);

  /// A stream that emits any new assets emitted by [this].
  ///
  /// 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>();

  /// A stream that emits an event whenever any transforms in this group logs
  /// an entry.
  Stream<LogEntry> get onLog => _onLogPool.stream;
  final _onLogPool = new StreamPool<LogEntry>.broadcast();

  GroupRunner(AssetCascade cascade, this._group, this._location) {
    _addPhase(new Phase(cascade, _location), _group.phases.first);
    for (var phase in _group.phases.skip(1)) {
      _addPhase(_phases.last.addPhase(), phase);
    }
  }

  /// Add a phase with [contents] to [this]'s list of phases.
  ///
  /// [contents] should be an inner [Iterable] from a [TransformGroup.phases]
  /// value.
  void _addPhase(Phase phase, Iterable contents) {
    _phases.add(phase);
    _onAssetPool.add(phase.onAsset);
    _onLogPool.add(phase.onLog);
    phase.onDone.listen((_) {
      if (!isDirty) _onDoneController.add(null);
    });
    phase.updateTransformers(contents);
  }

  /// Force all [LazyTransformer]s' transforms in this group to begin producing
  /// concrete assets.
  void forceAllTransforms() {
    for (var phase in _phases) {
      phase.forceAllTransforms();
    }
  }

  /// Adds a new asset as an input for this group.
  void addInput(AssetNode node) {
    _phases.first.addInput(node);
  }

  /// Removes this group and all sub-phases within it.
  void remove() {
    _phases.first.remove();
  }

  String toString() => "group in phase $_location for $_group";
}