More fixes in the Fixes service.

pkg/analysis_services/lib/src/correction/source_buffer.dart

+// 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.
+
+// This code was auto-generated, is not intended to be edited, and is subject to
+// significant change. Please see the README file for more information.
+
+library services.src.correction.source_buffer;
+
+import 'package:analysis_services/correction/change.dart';
+import 'package:analyzer/src/generated/source.dart';
+
+
+/**
+ * Helper for building Dart source with linked positions.
+ */
+class SourceBuilder {
+  final String file;
+  final int offset;
+  final StringBuffer _buffer = new StringBuffer();
+
+  final List<PositionGroup> positionGroups = <PositionGroup>[];
+  PositionGroup _currentPositionGroup;
+  int _currentPositionStart;
+
+  SourceBuilder(this.file, this.offset);
+
+  void addProposal(String proposal) {
+    // TODO(scheglov) implement
+//    _currentPositionGroup.addProposal();
+  }
+
+  void addProposals(List<String> proposals) {
+    proposals.forEach((proposal) => addProposal(proposal));
+  }
+
+  /**
+   * Appends [s] to the buffer.
+   */
+  SourceBuilder append(String s) {
+    _buffer.write(s);
+    return this;
+  }
+
+  /**
+   * Ends position started using [startPosition].
+   */
+  void endPosition() {
+    assert(_currentPositionGroup != null);
+    _addPosition();
+    _currentPositionGroup = null;
+  }
+
+  /**
+   * Marks start of a new linked position for the group with the given ID.
+   */
+  void startPosition(String groupId) {
+    assert(_currentPositionGroup == null);
+    for (PositionGroup position in positionGroups) {
+      if (position.id == groupId) {
+        _currentPositionGroup = position;
+        break;
+      }
+    }
+    if (_currentPositionGroup == null) {
+      _currentPositionGroup = new PositionGroup(groupId);
+      positionGroups.add(_currentPositionGroup);
+    }
+    _currentPositionStart = _buffer.length;
+  }
+
+  @override
+  String toString() => _buffer.toString();
+
+  /**
+   * Adds position location [SourceRange] using current fields.
+   */
+  void _addPosition() {
+    int start = offset + _currentPositionStart;
+    int end = offset + _buffer.length;
+    Position position = new Position(file, start, end - start);
+    _currentPositionGroup.add(position);
+  }
+}