whiteboard-app/lib/utils/markdown.js

Whiteboard - a slide-based activity presentation system

// This module contains code copied from the TagLex module, which is for
// building small markdown-like languages. In this case, it contains a minimal
// markdown dialect presently only use by the Title module

const taglex = require('taglex');

const ruleset = new taglex.TagRuleSet();
const classes = new taglex.TagClassManager();

// Let's start with a simple italic tag, specified _like this_
ruleset.add_tag({
    name: 'italic',
    open: '_',
    close: '_',

    // contained by 'style' and 'containers'
    parents: classes.get('style', 'container', 'root'),

    // payload can be in any structure we want
    payload: { start: '<em>', finish: '</em>' },
});
classes.add('italic', 'style'); // we give it the class 'style'

// Same thing for bold
ruleset.add_tag({
    name: 'bold',
    open: '*',
    close: '*',
    parents: classes.get('style', 'container', 'root'),
    payload: { start: '<strong>', finish: '</strong>' },
});
classes.add('bold', 'style');


function minimarkdown(input) {
    // Create a new parser for each input
    const parser = ruleset.new_parser();

    const results = [];
    parser.on('tag_open', (payload) => {
        results.push(payload.start);
    });

    parser.on('text_node', (text) => {
        // escape html & normalize whitespace
        const normalized = text
            .replace(/&/g, '&amp;')
            .replace(/</g, '&lt;')
            .replace(/>/g, '&lt;')
            .replace(/\r?\n/g, '<br />')
            .replace(/^\s*/, '')
            .replace(/\s*$/, '')
            .replace(/[\s]+/g, ' ');
        results.push(normalized);
    });

    parser.on('tag_close', (payload) => {
        results.push(`${payload.finish}\n`);
    });

    parser.write(input);

    // parser automatically close remaining tags when .end() is called
    parser.end();

    // Return the processed results
    return results.join('');
}

const reOps = /[|\\{}()[\]^$+*?.]/g;

// Including 'i' for macOS and win compatibility
// TODO: Possibly should check the case sensitivity of the filesystem and base
// this on that, but this is only defending against very, very unlikely bugs on
// GNU/Linux or BSD
function relativizeMarkdown(dirPath, markdown) {
    const escDirPath = dirPath.replace(reOps, '\\$&');
    const pathRegexp = new RegExp(`file://${escDirPath}`, 'gi');
    return markdown.replace(pathRegexp, 'file://./');
}

function absolutizeHtml(dirPath, html) {
    return html.replace(/file:\/\/\.\//gi, `file://${dirPath}/`);
}

function cleanMinimarkdown(text) {
    const clean = text.replace(/\W+/g, ' ');
    return clean.replace(/\s+/g, ' ').trim();
}

const MAX_PREVIEW_SIZE = 50;

function addEllipses(text) {
    const alphanum = text
        .replace(/\s+/gi, ' ')
        .replace(/\([^)]+\)/gi, '') // remove everything in parens (e.g links)
        .replace(/[^0-9a-z ]/gi, '')
        .trim();
    if (alphanum.length < MAX_PREVIEW_SIZE) {
        return alphanum;
    }
    return `${alphanum.slice(0, MAX_PREVIEW_SIZE - 3)}&#8230;`;
}

module.exports = {
    minimarkdown,
    cleanMinimarkdown,
    relativizeMarkdown,
    absolutizeHtml,
    addEllipses,
};