123 lines
3.2 KiB
JavaScript
123 lines
3.2 KiB
JavaScript
import { syntaxError } from '../error/syntaxError.mjs';
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import { Token } from './ast.mjs';
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import { isNameStart } from './characterClasses.mjs';
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import { createToken, printCodePointAt, readName } from './lexer.mjs';
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import { TokenKind } from './tokenKind.mjs';
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/**
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* Given a Source schema coordinate, creates a Lexer for that source.
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* A SchemaCoordinateLexer is a stateful stream generator in that every time
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* it is advanced, it returns the next token in the Source. Assuming the
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* source lexes, the final Token emitted by the lexer will be of kind
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* EOF, after which the lexer will repeatedly return the same EOF token
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* whenever called.
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*/
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export class SchemaCoordinateLexer {
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/**
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* The previously focused non-ignored token.
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*/
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/**
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* The currently focused non-ignored token.
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*/
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/**
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* The (1-indexed) line containing the current token.
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* Since a schema coordinate may not contain newline, this value is always 1.
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*/
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line = 1;
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/**
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* The character offset at which the current line begins.
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* Since a schema coordinate may not contain newline, this value is always 0.
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*/
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lineStart = 0;
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constructor(source) {
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const startOfFileToken = new Token(TokenKind.SOF, 0, 0, 0, 0);
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this.source = source;
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this.lastToken = startOfFileToken;
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this.token = startOfFileToken;
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}
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get [Symbol.toStringTag]() {
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return 'SchemaCoordinateLexer';
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}
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/**
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* Advances the token stream to the next non-ignored token.
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*/
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advance() {
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this.lastToken = this.token;
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const token = (this.token = this.lookahead());
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return token;
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}
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/**
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* Looks ahead and returns the next non-ignored token, but does not change
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* the current Lexer token.
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*/
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lookahead() {
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let token = this.token;
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if (token.kind !== TokenKind.EOF) {
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// Read the next token and form a link in the token linked-list.
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const nextToken = readNextToken(this, token.end); // @ts-expect-error next is only mutable during parsing.
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token.next = nextToken; // @ts-expect-error prev is only mutable during parsing.
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nextToken.prev = token;
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token = nextToken;
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}
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return token;
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}
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}
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/**
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* Gets the next token from the source starting at the given position.
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*/
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function readNextToken(lexer, start) {
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const body = lexer.source.body;
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const bodyLength = body.length;
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const position = start;
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if (position < bodyLength) {
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const code = body.charCodeAt(position);
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switch (code) {
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case 0x002e:
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// .
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return createToken(lexer, TokenKind.DOT, position, position + 1);
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case 0x0028:
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// (
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return createToken(lexer, TokenKind.PAREN_L, position, position + 1);
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case 0x0029:
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// )
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return createToken(lexer, TokenKind.PAREN_R, position, position + 1);
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case 0x003a:
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// :
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return createToken(lexer, TokenKind.COLON, position, position + 1);
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case 0x0040:
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// @
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return createToken(lexer, TokenKind.AT, position, position + 1);
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} // Name
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if (isNameStart(code)) {
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return readName(lexer, position);
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}
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throw syntaxError(
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lexer.source,
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position,
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`Invalid character: ${printCodePointAt(lexer, position)}.`,
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);
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}
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return createToken(lexer, TokenKind.EOF, bodyLength, bodyLength);
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}
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