RocketChat/Rocket.Chat

import type { Renderer } from 'markdown-it';
import MarkdownIt from 'markdown-it';

const md = new MarkdownIt({
    html: true,
    breaks: true,
    linkify: true,
    typographer: true,
});

const defaultRender = md.renderer.rules.link_open || ((tokens, idx, options, _env, self) => self.renderToken(tokens, idx, options));

md.renderer.rules.link_open = (tokens, idx, options, env, self) => {
    const targetAttrIndex = tokens[idx].attrIndex('target');
    const relAttrIndex = tokens[idx].attrIndex('rel');

    if (targetAttrIndex < 0) {
        tokens[idx].attrPush(['target', '_blank']);
    } else {
        const { attrs } = tokens[idx];

        if (attrs) {
            attrs[targetAttrIndex][1] = '_blank';
        }
    }

    if (relAttrIndex < 0) {
        tokens[idx].attrPush(['rel', 'noopener noreferrer']);
    } else {
        const { attrs } = tokens[idx];

        if (attrs) {
            attrs[relAttrIndex][1] = 'noopener noreferrer';
        }
    }

    return defaultRender(tokens, idx, options, env, self);
};

md.use((md) => {
    const renderStrong: Renderer.RenderRule = (tokens, idx, opts, _, slf) => {
        const token = tokens[idx];
        if (token.markup === '*') {
            token.tag = 'strong';
        }
        return slf.renderToken(tokens, idx, opts);
    };

    md.renderer.rules.em_open = renderStrong;
    md.renderer.rules.em_close = renderStrong;
});

md.use((md) => {
    md.inline.ruler.push('strikethrough', (state, silent) => {
        const marker = state.src.charCodeAt(state.pos);

        if (silent) {
            return false;
        }

        if (marker !== 0x7e /* ~ */) {
            return false;
        }

        const scanned = state.scanDelims(state.pos, true);

        const ch = String.fromCharCode(marker);

        const len = scanned.length;
        for (let i = 0; i < len; i += 1) {
            const token = state.push('text', '', 0);
            token.content = ch;

            state.delimiters.push({
                marker,
                length: 0,
                jump: i,
                token: state.tokens.length - 1,
                end: -1,
                open: scanned.can_open,
                close: scanned.can_close,
            });
        }

        state.pos += scanned.length;

        return true;
    });
});

export const renderMarkdown = (...args: Parameters<typeof md.render>) => md.render(...args);