parser-combinator/src/lib/standard/markdown/text-parser.js

Parser combinators

/**
 * Created by Simon on 14/12/2016.
 */

/**
 * This parse a text paragraph
 * text can be "simple" text; bold, italic or a mix (sequence) of those
 * a paragraph ends with a blank line("\n\n" or "\n  \t  \n") or "end of stream" (F.eos())
 */
import {F, C} from '../../parsec/index';
import stream from '../../stream/index';
import T from './token';

function trimStartingLineFeed(str) {
    return str.replace(/^[\s]*/, '');
}

function trimEndingLineFeed(str) {
    return str.replace(/[\s]*$/, '');
}

function stop() {
    return F.eos.or(T.lineFeed()).or(C.charIn('*`'));
}

function pureText() {
    return (
        F.not(stop())
            .rep() //  ['a','\n','b'] -> 'a b'
            // But on Windows, we will ignore the \r
            // inside line break will be put as space, but we clear initial or final \n
            .map(chars => {
                let allChars = chars.join('');
                return allChars.replace(/\n/g, ' ').replace(/\r/g, '');
            })
    );
}

function italic(pureTextParser) {
    return C.char('*')
        .thenRight(pureTextParser)
        .thenLeft(C.char('*'))
        .map(string => ({italic: string}));
}

function bold(pureTextParser) {
    return C.string('**')
        .thenRight(pureTextParser)
        .thenLeft(C.string('**'))
        .map(string => ({bold: string}));
}

function code(pureTextParser) {
    return C.char('`')
        .thenRight(pureTextParser)
        .thenLeft(C.char('`'))
        .map(string => ({code: string}));
}

function text(pureTextParser) {
    return pureTextParser.map(string => ({text: string}));
}

/**
 * @param pureTextParser : defines if a text accept some chars or not
 * @param stopParser : defines if text stops at the end of line
 * @returns Parser
 */
function formattedSequence(pureTextParser, stopParser) {
    return bold(pureTextParser)
        .or(italic(pureTextParser))
        .or(text(pureTextParser))
        .or(code(pureTextParser))
        .rep()
        .thenLeft(stopParser);
}

function formattedParagraph() {
    return T.blank()
        .thenRight(formattedSequence(pureText(), stop()))
        .map(list => {
            var array = list.array();
            // We trim the first and last element of the paragraph
            if (
                array.length > 0 &&
                typeof array[0] === 'object' &&
                array[0].text
            ) {
                array[0].text = trimStartingLineFeed(array[0].text);
                const last = array.length - 1;
                array[last].text = trimEndingLineFeed(array[last].text);
            }

            return {paragraph: array};
        });
}

function parseText(line, offset = 0) {
    return formattedParagraph().parse(stream.ofString(line), offset);
}

export default {
    stop,
    pureText,
    italic,
    bold,
    code,
    text,
    formattedSequence,
    formattedParagraph,
    parse(line) {
        return parseText(line, 0);
    },
};