parjs/src/internal/parsers/regexp.ts

A parser-combinator library for JavaScript.

/**
 * @module parjs
 */
/** */

import {ParsingState} from "../state";
import {ResultKind} from "../result";
import {Parjser} from "../parjser";
import {ParjserBase} from "../parser";

/**
 * Returns a parser that will try to match the regular expression at the current
 * position and yield the result set. If it can't, the parser will fail softly.
 * The match must start at the current position. It can't skip any part of the
 * input.
 * @param origRegexp
 */
export function regexp(origRegexp: RegExp): Parjser<string[]> {
    let flags = [origRegexp.ignoreCase && "i", origRegexp.multiline && "m"].filter(x => x).join("");
    let regexp = new RegExp(origRegexp.source, `${flags}y`);
    this.reason = `expecting input matching /${origRegexp.source}/`;
    return new class Regexp extends ParjserBase {
        type = "regexp";
        expecting = `expecting input matching '${regexp.source}'`;
        _apply(ps: ParsingState) {
            let {input, position} = ps;
            regexp.lastIndex = position;
            let match = regexp.exec(input);
            if (!match) {
                ps.kind = ResultKind.SoftFail;
                return;
            }
            ps.position += match[0].length;
            ps.value = match.slice();
            ps.kind = ResultKind.Ok;
        }
    }();
}