Implement diff algorithm for libraries.

dart/site/try/poi/diff.dart

Index: dart/site/try/poi/diff.dart
diff --git a/dart/site/try/poi/diff.dart b/dart/site/try/poi/diff.dart
new file mode 100644
index 0000000000000000000000000000000000000000..a2e17eb420156146bf4600b96cd7d64d4d8fe94e
--- /dev/null
+++ b/dart/site/try/poi/diff.dart
@@ -0,0 +1,134 @@
+// Copyright (c) 2014, 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 trydart.poi.diff;
+
+import 'dart:async' show
+    Completer,
+    Future,
+    Stream;
+
+import 'dart:convert' show
+    LineSplitter,
+    UTF8;
+
+import 'package:compiler/compiler.dart' as api;
+
+import 'package:compiler/implementation/dart2jslib.dart' show
+    Compiler,
+    Enqueuer,
+    QueueFilter,
+    Script,
+    WorkItem;
+
+import 'package:compiler/implementation/elements/visitor.dart' show
+    ElementVisitor;
+
+import 'package:compiler/implementation/elements/elements.dart' show
+    AbstractFieldElement,
+    ClassElement,
+    CompilationUnitElement,
+    Element,
+    ElementCategory,
+    FunctionElement,
+    LibraryElement,
+    ScopeContainerElement;
+
+import 'package:compiler/implementation/elements/modelx.dart' as modelx;
+
+import 'package:compiler/implementation/dart_types.dart' show
+    DartType;
+
+import 'package:compiler/implementation/scanner/scannerlib.dart' show
+    EOF_TOKEN,
+    ErrorToken,
+    IDENTIFIER_TOKEN,
+    KEYWORD_TOKEN,
+    PartialClassElement,
+    PartialElement,
+    Token;
+
+import 'package:compiler/implementation/source_file.dart' show
+    StringSourceFile;
+
+class Difference {
+  final Element before;
+  final Element after;
+  Token token;
+
+  Difference(this.before, this.after);
+
+  String toString() {
+    if (before == null) return 'Added($after)';
+    if (after == null) return 'Removed($before)';
+    return 'Modified($after -> $before)';
+  }
+}
+
+List<Difference> computeDifference(
+    ScopeContainerElement before,
+    ScopeContainerElement after) {
+  Map<String, Element> beforeMap = <String, Element>{};
+  before.forEachLocalMember((Element element) {
+    beforeMap[element.name] = element;
+  });
+  List<Difference> modifications = <Difference>[];
+  List<Difference> potentiallyChanged = <Difference>[];
+  after.forEachLocalMember((Element element) {
+    Element existing = beforeMap.remove(element.name);
+    if (existing == null) {
+      modifications.add(new Difference(null, element));
+    } else {
+      potentiallyChanged.add(new Difference(existing, element));
+    }
+  });
+
+  modifications.addAll(
+      beforeMap.values.map((Element element) => new Difference(element, null)));
+
+  modifications.addAll(
+      potentiallyChanged.where(areDifferentElements));
+
+  return modifications;
+}
+
+bool areDifferentElements(Difference diff) {
+  Element beforeElement = diff.before;
+  Element afterElement = diff.after;
+  var before = (beforeElement is modelx.VariableElementX)
+      ? beforeElement.variables : beforeElement;
+  var after = (afterElement is modelx.VariableElementX)
+      ? afterElement.variables : afterElement;
+  if (before is PartialElement && after is PartialElement) {
+    Token beforeToken = before.beginToken;
+    Token afterToken = after.beginToken;
+    Token stop = before.endToken;
+    int beforeKind = beforeToken.kind;
+    int afterKind = afterToken.kind;
+    while (beforeKind != EOF_TOKEN && afterKind != EOF_TOKEN) {
+
+      if (beforeKind != afterKind) {
+        diff.token = afterToken;
+        return true;
+      }
+
+      if (beforeToken is! ErrorToken && afterToken is! ErrorToken) {
+        if (beforeToken.value != afterToken.value) {
+          diff.token = afterToken;
+          return true;
+        }
+      }
+
+      if (beforeToken == stop) return false;
+
+      beforeToken = beforeToken.next;
+      afterToken = afterToken.next;
+      beforeKind = beforeToken.kind;
+      afterKind = afterToken.kind;
+    }
+    return beforeKind != afterKind;
+  }
+  print("$before isn't a PartialElement");
+  return true;
+}