markdown-it/lib/rules_inline/link.mjs

// Process [link](<to> "stuff")

import { normalizeReference, isSpace } from '../common/utils.mjs';

export default function link(state, silent) {
  let code,
      label,
      res,
      ref,
      href = '',
      title = '',
      start = state.pos,
      parseReference = true;

  if (state.src.charCodeAt(state.pos) !== 0x5B/* [ */) { return false; }

  const oldPos = state.pos;
  const max = state.posMax;
  const labelStart = state.pos + 1;
  const labelEnd = state.md.helpers.parseLinkLabel(state, state.pos, true);

  // parser failed to find ']', so it's not a valid link
  if (labelEnd < 0) { return false; }

  let pos = labelEnd + 1;
  if (pos < max && state.src.charCodeAt(pos) === 0x28/* ( */) {
    //
    // Inline link
    //

    // might have found a valid shortcut link, disable reference parsing
    parseReference = false;

    // [link](  <href>  "title"  )
    //        ^^ skipping these spaces
    pos++;
    for (; pos < max; pos++) {
      code = state.src.charCodeAt(pos);
      if (!isSpace(code) && code !== 0x0A) { break; }
    }
    if (pos >= max) { return false; }

    // [link](  <href>  "title"  )
    //          ^^^^^^ parsing link destination
    start = pos;
    res = state.md.helpers.parseLinkDestination(state.src, pos, state.posMax);
    if (res.ok) {
      href = state.md.normalizeLink(res.str);
      if (state.md.validateLink(href)) {
        pos = res.pos;
      } else {
        href = '';
      }

      // [link](  <href>  "title"  )
      //                ^^ skipping these spaces
      start = pos;
      for (; pos < max; pos++) {
        code = state.src.charCodeAt(pos);
        if (!isSpace(code) && code !== 0x0A) { break; }
      }

      // [link](  <href>  "title"  )
      //                  ^^^^^^^ parsing link title
      res = state.md.helpers.parseLinkTitle(state.src, pos, state.posMax);
      if (pos < max && start !== pos && res.ok) {
        title = res.str;
        pos = res.pos;

        // [link](  <href>  "title"  )
        //                         ^^ skipping these spaces
        for (; pos < max; pos++) {
          code = state.src.charCodeAt(pos);
          if (!isSpace(code) && code !== 0x0A) { break; }
        }
      }
    }

    if (pos >= max || state.src.charCodeAt(pos) !== 0x29/* ) */) {
      // parsing a valid shortcut link failed, fallback to reference
      parseReference = true;
    }
    pos++;
  }

  if (parseReference) {
    //
    // Link reference
    //
    if (typeof state.env.references === 'undefined') { return false; }

    if (pos < max && state.src.charCodeAt(pos) === 0x5B/* [ */) {
      start = pos + 1;
      pos = state.md.helpers.parseLinkLabel(state, pos);
      if (pos >= 0) {
        label = state.src.slice(start, pos++);
      } else {
        pos = labelEnd + 1;
      }
    } else {
      pos = labelEnd + 1;
    }

    // covers label === '' and label === undefined
    // (collapsed reference link and shortcut reference link respectively)
    if (!label) { label = state.src.slice(labelStart, labelEnd); }

    ref = state.env.references[normalizeReference(label)];
    if (!ref) {
      state.pos = oldPos;
      return false;
    }
    href = ref.href;
    title = ref.title;
  }

  //
  // We found the end of the link, and know for a fact it's a valid link;
  // so all that's left to do is to call tokenizer.
  //
  if (!silent) {
    state.pos = labelStart;
    state.posMax = labelEnd;

    const token_o = state.push('link_open', 'a', 1);
    const attrs = [ [ 'href', href ] ];
    token_o.attrs  = attrs;
    if (title) {
      attrs.push([ 'title', title ]);
    }

    state.linkLevel++;
    state.md.inline.tokenize(state);
    state.linkLevel--;

    state.push('link_close', 'a', -1);
  }

  state.pos = pos;
  state.posMax = max;
  return true;
}