cm-tarnation/lib/grammar/matchers/string.js

An alternative parser for CodeMirror 6

/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
import { pointsMatch, toPoints } from "../../util";
/** Matcher that takes a string pattern, and matches that against an input. */
export class StringMatcher {
    /**
     * @param str - The source string.
     * @param ignoreCase - If `true`, matches will be case-insensitive.
     * @param variables - A variable table to use when expanding variables.
     */
    constructor(str, ignoreCase = false, variables) {
        if (variables)
            str = expandVariables(str, variables);
        if (ignoreCase)
            str = str.toLowerCase();
        this.cased = ignoreCase && str.toLowerCase() !== str.toUpperCase();
        this.length = str.length;
        this.points = toPoints(str);
    }
    /**
     * Tests to see if this pattern matches the given string.
     *
     * @param str - The string to match.
     * @param pos - The position to start matching at.
     */
    test(str, pos) {
        if (this.length > str.length)
            return false;
        if (pointsMatch(this.points, str, pos))
            return true;
        // less optimized code path due to lowercasing requirement
        if (this.cased) {
            const lowered = str.slice(pos, pos + this.length).toLowerCase();
            return pointsMatch(this.points, lowered, 0);
        }
        return false;
    }
    /**
     * Returns the results of attempting to match a string against this pattern.
     *
     * @param str - The string to match.
     * @param pos - The position to start matching at.
     */
    match(str, pos) {
        if (this.test(str, pos)) {
            return {
                total: str.slice(pos, pos + this.length),
                captures: null,
                length: this.length
            };
        }
        return null;
    }
}
/**
 * Expands the variables in a pattern source using a variable table.
 *
 * @param src - The source to expand.
 * @param variables - The variable table to use.
 */
function expandVariables(src, variables) {
    let depth = 0;
    while (/@\w/.test(src) && depth < 5) {
        depth++;
        src = src.replace(/@(\w+)/g, (_, ident) => {
            const value = variables[ident];
            if (typeof value !== "string") {
                throw new Error(`Variable ${ident} is not a string`);
            }
            return value;
        });
    }
    return src;
}
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