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// Copyright 2019 The Flutter team. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
import 'package:string_scanner/string_scanner.dart';
abstract class SyntaxPrehighlighter {
List<CodeSpan> format(String src);
}
class DartSyntaxPrehighlighter extends SyntaxPrehighlighter {
DartSyntaxPrehighlighter() {
_spans = <_HighlightSpan>[];
}
static const List<String> _keywords = <String>[
'abstract',
'as',
'assert',
'async',
'await',
'break',
'case',
'catch',
'class',
'const',
'continue',
'default',
'deferred',
'do',
'dynamic',
'else',
'enum',
'export',
'external',
'extends',
'factory',
'false',
'final',
'finally',
'for',
'get',
'if',
'implements',
'import',
'in',
'is',
'library',
'new',
'null',
'operator',
'part',
'rethrow',
'return',
'set',
'static',
'super',
'switch',
'sync',
'this',
'throw',
'true',
'try',
'typedef',
'var',
'void',
'while',
'with',
'yield',
];
static const List<String> _builtInTypes = <String>[
'int',
'double',
'num',
'bool',
];
String? _src;
late StringScanner _scanner;
late List<_HighlightSpan> _spans;
@override
List<CodeSpan> format(String? src) {
_src = src;
_scanner = StringScanner(_src!);
if (_generateSpans()) {
// Successfully parsed the code
final formattedText = <CodeSpan>[];
var currentPosition = 0;
for (final span in _spans) {
if (currentPosition != span.start) {
formattedText.add(
CodeSpan(text: _src!.substring(currentPosition, span.start)));
}
formattedText
.add(CodeSpan(type: span.type, text: span.textForSpan(_src!)));
currentPosition = span.end;
}
if (currentPosition != _src!.length) {
formattedText.add(
CodeSpan(text: _src!.substring(currentPosition, _src!.length)));
}
return formattedText;
} else {
// Parsing failed, return with only basic formatting
return [CodeSpan(type: _HighlightType.base, text: src)];
}
}
bool _generateSpans() {
var lastLoopPosition = _scanner.position;
while (!_scanner.isDone) {
// Skip White space
_scanner.scan(RegExp(r'\s+'));
// Block comments
if (_scanner.scan(RegExp(r'/\*(.|\n)*\*/'))) {
_spans.add(_HighlightSpan(
_HighlightType.comment,
_scanner.lastMatch!.start,
_scanner.lastMatch!.end,
));
continue;
}
// Line comments
if (_scanner.scan('//')) {
final startComment = _scanner.lastMatch!.start;
var eof = false;
int endComment;
if (_scanner.scan(RegExp(r'.*\n'))) {
endComment = _scanner.lastMatch!.end - 1;
} else {
eof = true;
endComment = _src!.length;
}
_spans.add(_HighlightSpan(
_HighlightType.comment,
startComment,
endComment,
));
if (eof) {
break;
}
continue;
}
// Raw r"String"
if (_scanner.scan(RegExp(r'r".*"'))) {
_spans.add(_HighlightSpan(
_HighlightType.string,
_scanner.lastMatch!.start,
_scanner.lastMatch!.end,
));
continue;
}
// Raw r'String'
if (_scanner.scan(RegExp(r"r'.*'"))) {
_spans.add(_HighlightSpan(
_HighlightType.string,
_scanner.lastMatch!.start,
_scanner.lastMatch!.end,
));
continue;
}
// Multiline """String"""
if (_scanner.scan(RegExp(r'"""(?:[^"\\]|\\(.|\n))*"""'))) {
_spans.add(_HighlightSpan(
_HighlightType.string,
_scanner.lastMatch!.start,
_scanner.lastMatch!.end,
));
continue;
}
// Multiline '''String'''
if (_scanner.scan(RegExp(r"'''(?:[^'\\]|\\(.|\n))*'''"))) {
_spans.add(_HighlightSpan(
_HighlightType.string,
_scanner.lastMatch!.start,
_scanner.lastMatch!.end,
));
continue;
}
// "String"
if (_scanner.scan(RegExp(r'"(?:[^"\\]|\\.)*"'))) {
_spans.add(_HighlightSpan(
_HighlightType.string,
_scanner.lastMatch!.start,
_scanner.lastMatch!.end,
));
continue;
}
// 'String'
if (_scanner.scan(RegExp(r"'(?:[^'\\]|\\.)*'"))) {
_spans.add(_HighlightSpan(
_HighlightType.string,
_scanner.lastMatch!.start,
_scanner.lastMatch!.end,
));
continue;
}
// Double
if (_scanner.scan(RegExp(r'\d+\.\d+'))) {
_spans.add(_HighlightSpan(
_HighlightType.number,
_scanner.lastMatch!.start,
_scanner.lastMatch!.end,
));
continue;
}
// Integer
if (_scanner.scan(RegExp(r'\d+'))) {
_spans.add(_HighlightSpan(_HighlightType.number,
_scanner.lastMatch!.start, _scanner.lastMatch!.end));
continue;
}
// Punctuation
if (_scanner.scan(RegExp(r'[\[\]{}().!=<>&\|\?\+\-\*/%\^~;:,]'))) {
_spans.add(_HighlightSpan(
_HighlightType.punctuation,
_scanner.lastMatch!.start,
_scanner.lastMatch!.end,
));
continue;
}
// Meta data
if (_scanner.scan(RegExp(r'@\w+'))) {
_spans.add(_HighlightSpan(
_HighlightType.keyword,
_scanner.lastMatch!.start,
_scanner.lastMatch!.end,
));
continue;
}
// Words
if (_scanner.scan(RegExp(r'\w+'))) {
_HighlightType? type;
var word = _scanner.lastMatch![0]!;
if (word.startsWith('_')) {
word = word.substring(1);
}
if (_keywords.contains(word)) {
type = _HighlightType.keyword;
} else if (_builtInTypes.contains(word)) {
type = _HighlightType.keyword;
} else if (_firstLetterIsUpperCase(word)) {
type = _HighlightType.klass;
} else if (word.length >= 2 &&
word.startsWith('k') &&
_firstLetterIsUpperCase(word.substring(1))) {
type = _HighlightType.constant;
}
if (type != null) {
_spans.add(_HighlightSpan(
type,
_scanner.lastMatch!.start,
_scanner.lastMatch!.end,
));
}
}
// Check if this loop did anything
if (lastLoopPosition == _scanner.position) {
// Failed to parse this file, abort gracefully
return false;
}
lastLoopPosition = _scanner.position;
}
_simplify();
return true;
}
void _simplify() {
for (var i = _spans.length - 2; i >= 0; i -= 1) {
if (_spans[i].type == _spans[i + 1].type &&
_spans[i].end == _spans[i + 1].start) {
_spans[i] = _HighlightSpan(
_spans[i].type,
_spans[i].start,
_spans[i + 1].end,
);
_spans.removeAt(i + 1);
}
}
}
bool _firstLetterIsUpperCase(String str) {
if (str.isNotEmpty) {
final first = str.substring(0, 1);
return first == first.toUpperCase();
}
return false;
}
}
enum _HighlightType {
number,
comment,
keyword,
string,
punctuation,
klass,
constant,
base,
}
class _HighlightSpan {
_HighlightSpan(this.type, this.start, this.end);
final _HighlightType type;
final int start;
final int end;
String textForSpan(String src) {
return src.substring(start, end);
}
}
class CodeSpan {
CodeSpan({this.type = _HighlightType.base, this.text});
final _HighlightType type;
final String? text;
@override
String toString() {
return 'TextSpan('
'style: codeStyle.${_styleNameOf(type)}, '
"text: '${_escape(text!)}'"
')';
}
}
String _styleNameOf(_HighlightType type) {
switch (type) {
case _HighlightType.number:
return 'numberStyle';
case _HighlightType.comment:
return 'commentStyle';
case _HighlightType.keyword:
return 'keywordStyle';
case _HighlightType.string:
return 'stringStyle';
case _HighlightType.punctuation:
return 'punctuationStyle';
case _HighlightType.klass:
return 'classStyle';
case _HighlightType.constant:
return 'constantStyle';
case _HighlightType.base:
return 'baseStyle';
}
}
String _escape(String text) {
final escapedText = StringBuffer();
for (final char in text.runes) {
if (char < 0x20 ||
char >= 0x7F ||
char == 0x22 ||
char == 0x24 ||
char == 0x27 ||
char == 0x5C) {
if (char <= 0xffff) {
escapedText.write('\\u${_encodeAndPad(char)}');
} else {
escapedText.write('\\u{${_encode(char)}}');
}
} else {
escapedText.write(String.fromCharCode(char));
}
}
return escapedText.toString();
}
String _encode(int charCode) {
return charCode.toRadixString(16);
}
String _encodeAndPad(int charCode) {
final encoded = _encode(charCode);
return '0' * (4 - encoded.length) + encoded;
}