markdown-it/lib/rules_inline/html_inline.mjs

// Process html tags

import { HTML_TAG_RE } from '../common/html_re.mjs';


function isLinkOpen(str) {
  return /^<a[>\s]/i.test(str);
}
function isLinkClose(str) {
  return /^<\/a\s*>/i.test(str);
}


function isLetter(ch) {
  /*eslint no-bitwise:0*/
  var lc = ch | 0x20; // to lower case
  return (lc >= 0x61/* a */) && (lc <= 0x7a/* z */);
}


export default function html_inline(state, silent) {
  var ch, match, max, token,
      pos = state.pos;

  if (!state.md.options.html) { return false; }

  // Check start
  max = state.posMax;
  if (state.src.charCodeAt(pos) !== 0x3C/* < */ ||
      pos + 2 >= max) {
    return false;
  }

  // Quick fail on second char
  ch = state.src.charCodeAt(pos + 1);
  if (ch !== 0x21/* ! */ &&
      ch !== 0x3F/* ? */ &&
      ch !== 0x2F/* / */ &&
      !isLetter(ch)) {
    return false;
  }

  match = state.src.slice(pos).match(HTML_TAG_RE);
  if (!match) { return false; }

  if (!silent) {
    token         = state.push('html_inline', '', 0);
    token.content = match[0];

    if (isLinkOpen(token.content))  state.linkLevel++;
    if (isLinkClose(token.content)) state.linkLevel--;
  }
  state.pos += match[0].length;
  return true;
}