monadic-parser.ts

/**
 * Copyright (c) 2018 mol* contributors, licensed under MIT, See LICENSE file for more info.
 *
 * @author David Sehnal <david.sehnal@gmail.com>
 */

/**
 * Adapted from Parsimmon (https://github.com/jneen/parsimmon)
 * Copyright (c) 2011-present J. Adkisson (http://jneen.net).
 */

export class MonadicParser<A> {
    constructor(public _: MonadicParser.Action<A>) { }

    parse(input: string): MonadicParser.ParseResult<A> {
        const result = this.skip(MonadicParser.eof)._(input, 0);
        if (result.status) {
            return { success: true, value: result.value };
        }
        return { success: false, index: makeLineColumnIndex(input, result.furthest), expected: result.expected };
    };

    tryParse(str: string) {
        const result = this.parse(str);
        if (result.success) {
            return result.value;
        } else {
            const msg = formatError(str, result);
            const err = new Error(msg);
            throw err;
        }
    }

    or<B>(alternative: MonadicParser<B>): MonadicParser<A | B> {
        return MonadicParser.alt(this, alternative);
    }

    trim<B>(parser: MonadicParser<B> | string): MonadicParser<A> {
        return this.wrap(parser, parser);
    }

    wrap<L, R>(leftParser: MonadicParser<L> | string, rightParser: MonadicParser<R> | string): MonadicParser<A> {
        return seqPick(1,
            typeof leftParser === 'string' ? MonadicParser.string(leftParser) : leftParser,
            this,
            typeof rightParser === 'string' ? MonadicParser.string(rightParser) : rightParser);
    }

    thru<B>(wrapper: (p: MonadicParser<A>) => MonadicParser<B>) {
        return wrapper(this);
    }

    then<B>(next: MonadicParser<B>): MonadicParser<B> {
        return seqPick(1, this, next);
    }

    many() {
        return new MonadicParser((input, i) => {
            const accum: A[] = [];
            let result: MonadicParser.Result<A> | undefined = void 0;

            while (true) {
                result = mergeReplies(this._(input, i), result);
                if (result.status) {
                    if (i === result.index) {
                        throw new Error('infinite loop detected in .many() parser --- calling .many() on a parser which can accept zero characters is usually the cause');
                    }
                    i = result.index;
                    accum.push(result.value);
                } else {