markdown-it/lib/rules_inline/entity.mjs

// Process html entity - {, ¯, ", ...

import { decodeHTML } from 'entities';
import { isValidEntityCode, fromCodePoint } from '../common/utils.mjs';


const DIGITAL_RE = /^&#((?:x[a-f0-9]{1,6}|[0-9]{1,7}));/i;
const NAMED_RE   = /^&([a-z][a-z0-9]{1,31});/i;


export default function entity(state, silent) {
  const pos = state.pos;
  const max = state.posMax;

  if (state.src.charCodeAt(pos) !== 0x26/* & */) return false;

  if (pos + 1 >= max) return false;

  const ch = state.src.charCodeAt(pos + 1);

  if (ch === 0x23 /* # */) {
    const match = state.src.slice(pos).match(DIGITAL_RE);
    if (match) {
      if (!silent) {
        const code = match[1][0].toLowerCase() === 'x' ? parseInt(match[1].slice(1), 16) : parseInt(match[1], 10);

        const token   = state.push('text_special', '', 0);
        token.content = isValidEntityCode(code) ? fromCodePoint(code) : fromCodePoint(0xFFFD);
        token.markup  = match[0];
        token.info    = 'entity';
      }
      state.pos += match[0].length;
      return true;
    }
  } else {
    const match = state.src.slice(pos).match(NAMED_RE);
    if (match) {
      const decoded = decodeHTML(match[0]);
      if (decoded !== match[0]) {
        if (!silent) {
          const token   = state.push('text_special', '', 0);
          token.content = decoded;
          token.markup  = match[0];
          token.info    = 'entity';
        }
        state.pos += match[0].length;
        return true;
      }
    }
  }

  return false;
}