@woosh/meep-engine/src/core/parser/simple/readBooleanToken.js

Pure JavaScript game engine. Fully featured and production ready.

import { assert } from "../../assert.js";
import DataType from "./DataType.js";
import ParserError from "./ParserError.js";
import Token from "./Token.js";
import TokenType from "./TokenType.js";

/**
 *
 * @param {string} text
 * @param {number} cursor
 * @param {number} length
 * @returns {Token}
 */
export function readBooleanToken(text, cursor, length) {
    assert.isString(text, 'text');
    assert.isNonNegativeInteger(cursor, 'cursor');
    assert.isNonNegativeInteger(length, 'length');

    const firstChar = text.charAt(cursor);

    let value;
    let end = cursor;

    if (firstChar === 't' && length - cursor >= 4) {
        if (text.substring(cursor + 1, cursor + 4) === 'rue') {
            value = true;
            end = cursor + 4;
        } else {
            throw new ParserError(cursor, `expected 'true', instead got '${text.substring(cursor, cursor + 4)}'`, text);
        }
    } else if (firstChar === 'f' && length - cursor >= 5) {
        if (text.substring(cursor + 1, cursor + 5) === 'alse') {
            value = false;
            end = cursor + 5;
        } else {
            throw new ParserError(cursor, `expected 'false', instead got '${text.substring(cursor, cursor + 5)}'`, text);
        }
    } else {
        throw new ParserError(cursor, `expected 't' or 'f', instead got '${firstChar}'`, text);
    }

    return new Token(value, cursor, end, TokenType.LiteralBoolean, DataType.Boolean);
}