Fasta infrastructure.

pkg/fasta/lib/src/translate_uri.dart

Index: pkg/fasta/lib/src/translate_uri.dart
diff --git a/pkg/fasta/lib/src/translate_uri.dart b/pkg/fasta/lib/src/translate_uri.dart
new file mode 100644
index 0000000000000000000000000000000000000000..6af35a9b7cc804f3ab817755e9330b41f262a38d
--- /dev/null
+++ b/pkg/fasta/lib/src/translate_uri.dart
@@ -0,0 +1,51 @@
+// Copyright (c) 2016, 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 fasta.translate_uri;
+
+import 'dart:async' show
+    Future;
+
+import 'dart:io' show
+    File;
+
+import 'package:package_config/packages_file.dart' as packages_file show
+    parse;
+
+import 'errors.dart' show
+    internalError;
+
+class TranslateUri {
+  final Map<String, Uri> packages;
+
+  TranslateUri(this.packages);
+
+  Uri translate(Uri uri) {
+    if (uri.scheme == "dart") return translateDartUri(uri);
+    if (uri.scheme == "package") return translatePackageUri(uri);
+    return null;
+  }
+
+  Uri translateDartUri(Uri uri) {
+    throw internalError("dart: URIs not implemented yet.");
+  }
+
+  Uri translatePackageUri(Uri uri) {
+    int index = uri.path.indexOf("/");
+    if (index == -1) return null;
+    String name = uri.path.substring(0, index);
+    String path = uri.path.substring(index + 1);
+    Uri root = packages[name];
+    if (root == null) return null;
+    return root.resolve(path);
+  }
+
+  static Future<TranslateUri> parse([Uri uri]) async {
+    uri ??= Uri.base.resolve(".packages");
+    File file = new File.fromUri(uri);
+    List<int> bytes = await file.readAsBytes();
+    Map<String, Uri> packages = packages_file.parse(bytes, uri);
+    return new TranslateUri(packages);
+  }
+}