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packages/barback/test/transformer/many_to_one.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.test.transformer.many_to_one;
+
+import 'dart:async';
+
+import 'package:barback/barback.dart';
+
+import 'mock.dart';
+
+/// A transformer that uses the contents of a file to define the other inputs.
+///
+/// Outputs a file with the same name as the primary but with an "out"
+/// extension containing the concatenated contents of all non-primary inputs.
+class ManyToOneTransformer extends MockTransformer {
+  final String extension;
+
+  /// Creates a transformer that consumes assets with [extension].
+  ///
+  /// That file contains a comma-separated list of paths and it will input
+  /// files at each of those paths.
+  ManyToOneTransformer(this.extension);
+
+  bool doIsPrimary(AssetId id) => id.extension == ".$extension";
+
+  Future doApply(Transform transform) {
+    return getPrimary(transform)
+        .then((primary) => primary.readAsString())
+        .then((contents) {
+      // Get all of the included inputs.
+      return Future.wait(contents.split(",").map((path) {
+        var id;
+        if (path.contains("|")) {
+          id = new AssetId.parse(path);
+        } else {
+          id = new AssetId(transform.primaryInput.id.package, path);
+        }
+        return getInput(transform, id).then((input) => input.readAsString());
+      }));
+    }).then((outputs) {
+      var id = transform.primaryInput.id.changeExtension(".out");
+      transform.addOutput(new Asset.fromString(id, outputs.join()));
+    });
+  }
+
+  String toString() => "many->1 $extension";
+}