Source selection API abstraction first cut.

pkg/analyzer_experimental/lib/src/services/formatter_impl.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 formatter_impl;
 
 import 'dart:math';
 
 import 'package:analyzer_experimental/analyzer.dart';
 import 'package:analyzer_experimental/src/generated/parser.dart';
@@ skipping 60 matching lines @@
 }
 
 /// Dart source code formatter.
 abstract class CodeFormatter {
 
   factory CodeFormatter([FormatterOptions options = const FormatterOptions()])
                         => new CodeFormatterImpl(options);
 
   /// Format the specified portion (from [offset] with [length]) of the given
   /// [source] string, optionally providing an [indentationLevel].
-  String format(CodeKind kind, String source, {int offset, int end,
-    int indentationLevel: 0});
+  FormattedSource format(CodeKind kind, String source, {int offset, int end,
+    int indentationLevel: 0, Selection selection: null});
 
 }
 
+/// Source selection state information.
+class Selection {
+  
+  /// The offset of the source selection.
+  final int offset;
+  
+  /// The length of the selection.
+  final int length;
+  
+  Selection(this.offset, this.length);
+}
+
+/// Formatted source.
+class FormattedSource {
+  
+  /// Selection state or null if unspecified.
+  final Selection selection;
+  
+  /// Formatted source string.
+  final String source;
+  
+  /// Create a formatted [source] result, with optional [selection] information.
+  FormattedSource(this.source, [this.selection = null]);
+}
+
+
 class CodeFormatterImpl implements CodeFormatter, AnalysisErrorListener {
 
   final FormatterOptions options;
   final errors = <AnalysisError>[];
   final whitespace = new RegExp(r'[\s]+');
 
   LineInfo lineInfo;
 
   CodeFormatterImpl(this.options);
 
-  String format(CodeKind kind, String source, {int offset, int end,
-      int indentationLevel: 0}) {
+  FormattedSource format(CodeKind kind, String source, {int offset, int end,
+      int indentationLevel: 0, Selection selection: null}) {
 
     var startToken = tokenize(source);
     checkForErrors();
 
     var node = parse(kind, startToken);
     checkForErrors();
 
     var formatter = new SourceVisitor(options, lineInfo);
     node.accept(formatter);
 
     var formattedSource = formatter.writer.toString();
     
     checkTokenStreams(startToken, tokenize(formattedSource));
 
-    return formattedSource;
+    return new FormattedSource(formattedSource);
   }
 
   checkTokenStreams(Token t1, Token t2) =>
       new TokenStreamComparator(lineInfo, t1, t2).verifyEquals();
 
   ASTNode parse(CodeKind kind, Token start) {
 
     var parser = new Parser(null, this);
 
     switch (kind) {
@@ skipping 1236 matching lines @@
     var lastLine =
         lineInfo.getLocation(lastOffset).lineNumber;
     var currentLine =
         lineInfo.getLocation(currentOffset).lineNumber;
     return currentLine - lastLine;
   }
 
   String toString() => writer.toString();
 
 }