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// 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.
/// Tools to help implement refactoring like transformations to Dart code.
/// [TextEditTransaction] supports making a series of changes to a text buffer.
/// [guessIndent] helps to guess the appropriate indentiation for the new code.
library source_maps.refactor;
import 'package:source_span/source_span.dart';
import 'printer.dart';
/// Editable text transaction.
/// Applies a series of edits using original location
/// information, and composes them into the edited string.
class TextEditTransaction {
final SourceFile file;
final String original;
final _edits = <_TextEdit>[];
/// Creates a new transaction.
TextEditTransaction(this.original, this.file);
bool get hasEdits => _edits.length > 0;
/// Edit the original text, replacing text on the range [begin] and [end]
/// with the [replacement]. [replacement] can be either a string or a
/// [NestedPrinter].
void edit(int begin, int end, replacement) {
_edits.add(new _TextEdit(begin, end, replacement));
/// Create a source map [SourceLocation] for [offset].
SourceLocation _loc(int offset) =>
file != null ? file.location(offset) : null;
/// Applies all pending [edit]s and returns a [NestedPrinter] containing the
/// rewritten string and source map information. [filename] is given to the
/// underlying printer to indicate the name of the generated file that will
/// contains the source map information.
/// Throws [UnsupportedError] if the edits were overlapping. If no edits were
/// made, the printer simply contains the original string.
NestedPrinter commit() {
var printer = new NestedPrinter();
if (_edits.length == 0) {
return printer..add(original, location: _loc(0), isOriginal: true);
// Sort edits by start location.
int consumed = 0;
for (var edit in _edits) {
if (consumed > edit.begin) {
var sb = new StringBuffer();
..write(': overlapping edits. Insert at offset ')
..write(' but have consumed ')
..write(' input characters. List of edits:');
for (var e in _edits) sb..write('\n ')..write(e);
throw new UnsupportedError(sb.toString());
// Add characters from the original string between this edit and the last
// one, if any.
var betweenEdits = original.substring(consumed, edit.begin);
..add(betweenEdits, location: _loc(consumed), isOriginal: true)
..add(edit.replace, location: _loc(edit.begin));
consumed = edit.end;
// Add any text from the end of the original string that was not replaced.
location: _loc(consumed), isOriginal: true);
return printer;
class _TextEdit implements Comparable<_TextEdit> {
final int begin;
final int end;
/// The replacement used by the edit, can be a string or a [NestedPrinter].
final replace;
_TextEdit(this.begin, this.end, this.replace);
int get length => end - begin;
String toString() => '(Edit @ $begin,$end: "$replace")';
int compareTo(_TextEdit other) {
int diff = begin - other.begin;
if (diff != 0) return diff;
return end - other.end;
/// Returns all whitespace characters at the start of [charOffset]'s line.
String guessIndent(String code, int charOffset) {
// Find the beginning of the line
int lineStart = 0;
for (int i = charOffset - 1; i >= 0; i--) {
var c = code.codeUnitAt(i);
if (c == _LF || c == _CR) {
lineStart = i + 1;
// Grab all the whitespace
int whitespaceEnd = code.length;
for (int i = lineStart; i < code.length; i++) {
var c = code.codeUnitAt(i);
if (c != _SPACE && c != _TAB) {
whitespaceEnd = i;
return code.substring(lineStart, whitespaceEnd);
const int _CR = 13;
const int _LF = 10;
const int _TAB = 9;
const int _SPACE = 32;