94 lines
2.8 KiB
Dart
94 lines
2.8 KiB
Dart
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import 'dart:async';
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import 'package:string_scanner/string_scanner.dart';
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import 'package:source_span/source_span.dart';
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import 'syntax_error.dart';
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import 'token.dart';
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import 'token_type.dart';
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final RegExp _whitespace = new RegExp('[ \t\n\r]+');
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final RegExp _boolean = new RegExp(r'true|false');
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final RegExp _number = new RegExp(r'-?[0-9]+(\.[0-9]+)?(E|e(\+|-)?[0-9]+)?');
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final RegExp _string = new RegExp(
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r'"((\\(["\\/bfnrt]|(u[0-9a-fA-F][0-9a-fA-F][0-9a-fA-F][0-9a-fA-F])))|([^"\\]))*"');
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final RegExp _name = new RegExp(r'[_A-Za-z][_0-9A-Za-z]*');
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final Map<Pattern, TokenType> _patterns = {
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'@': TokenType.ARROBA,
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':': TokenType.COLON,
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',': TokenType.COMMA,
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r'$': TokenType.DOLLAR,
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'...': TokenType.ELLIPSIS,
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'=': TokenType.EQUALS,
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'!': TokenType.EXCLAMATION,
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'{': TokenType.LBRACE,
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'}': TokenType.RBRACE,
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'[': TokenType.LBRACKET,
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']': TokenType.RBRACKET,
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'(': TokenType.LPAREN,
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')': TokenType.RPAREN,
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'fragment': TokenType.FRAGMENT,
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'mutation': TokenType.MUTATION,
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'on': TokenType.ON,
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'query': TokenType.QUERY,
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_boolean: TokenType.BOOLEAN,
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_number: TokenType.NUMBER,
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_string: TokenType.STRING,
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_name: TokenType.NAME
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};
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class Lexer implements StreamTransformer<String, Token> {
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@override
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Stream<Token> bind(Stream<String> stream) {
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var ctrl = new StreamController<Token>();
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stream.listen((str) {
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var scanner = new StringScanner(str);
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int line = 1, column = 1;
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while (!scanner.isDone) {
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List<Token> potential = [];
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if (scanner.scan(_whitespace)) {
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var text = scanner.lastMatch[0];
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line += '\n'.allMatches(text).length;
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var lastNewLine = text.lastIndexOf('\n');
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if (lastNewLine != -1) {
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int len = text.substring(lastNewLine + 1).length;
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column = 1 + len;
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}
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continue;
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}
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for (var pattern in _patterns.keys) {
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if (scanner.matches(pattern)) {
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potential.add(new Token(_patterns[pattern], scanner.lastMatch[0]));
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}
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}
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if (potential.isEmpty) {
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var ch = new String.fromCharCode(scanner.readChar());
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ctrl.addError(new SyntaxError("Unexpected token '$ch'.", line, column));
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} else {
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// Choose longest token
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potential.sort((a, b) => a.text.length.compareTo(b.text.length));
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var chosen = potential.first;
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var start =
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new SourceLocation(scanner.position, line: line, column: column);
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ctrl.add(chosen);
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scanner.position += chosen.text.length;
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column += chosen.text.length;
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var end =
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new SourceLocation(scanner.position, line: line, column: column);
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chosen.span = new SourceSpan(start, end, chosen.text);
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}
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}
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})
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..onDone(ctrl.close)
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..onError(ctrl.addError);
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return ctrl.stream;
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}
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}
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