markdown-it/lib/rules_inline/autolink.mjs

// Process autolinks '<protocol:...>'

/*eslint max-len:0*/
const EMAIL_RE    = /^([a-zA-Z0-9.!#$%&'*+\/=?^_`{|}~-]+@[a-zA-Z0-9](?:[a-zA-Z0-9-]{0,61}[a-zA-Z0-9])?(?:\.[a-zA-Z0-9](?:[a-zA-Z0-9-]{0,61}[a-zA-Z0-9])?)*)$/;
const AUTOLINK_RE = /^([a-zA-Z][a-zA-Z0-9+.\-]{1,31}):([^<>\x00-\x20]*)$/;


export default function autolink(state, silent) {
  let pos = state.pos;

  if (state.src.charCodeAt(pos) !== 0x3C/* < */) { return false; }

  const start = state.pos;
  const max = state.posMax;

  for (;;) {
    if (++pos >= max) return false;

    const ch = state.src.charCodeAt(pos);

    if (ch === 0x3C /* < */) return false;
    if (ch === 0x3E /* > */) break;
  }

  const url = state.src.slice(start + 1, pos);

  if (AUTOLINK_RE.test(url)) {
    const fullUrl = state.md.normalizeLink(url);
    if (!state.md.validateLink(fullUrl)) { return false; }

    if (!silent) {
      const token_o   = state.push('link_open', 'a', 1);
      token_o.attrs   = [ [ 'href', fullUrl ] ];
      token_o.markup  = 'autolink';
      token_o.info    = 'auto';

      const token_t   = state.push('text', '', 0);
      token_t.content = state.md.normalizeLinkText(url);

      const token_c   = state.push('link_close', 'a', -1);
      token_c.markup  = 'autolink';
      token_c.info    = 'auto';
    }

    state.pos += url.length + 2;
    return true;
  }

  if (EMAIL_RE.test(url)) {
    const fullUrl = state.md.normalizeLink('mailto:' + url);
    if (!state.md.validateLink(fullUrl)) { return false; }

    if (!silent) {
      const token_o   = state.push('link_open', 'a', 1);
      token_o.attrs   = [ [ 'href', fullUrl ] ];
      token_o.markup  = 'autolink';
      token_o.info    = 'auto';

      const token_t   = state.push('text', '', 0);
      token_t.content = state.md.normalizeLinkText(url);

      const token_c   = state.push('link_close', 'a', -1);
      token_c.markup  = 'autolink';
      token_c.info    = 'auto';
    }

    state.pos += url.length + 2;
    return true;
  }

  return false;
}