markdown-it/lib/rules_inline/links.js

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

'use strict';

var parseLinkLabel       = require('../helpers/parse_link_label');
var parseLinkDestination = require('../helpers/parse_link_destination');
var parseLinkTitle       = require('../helpers/parse_link_title');
var normalizeReference   = require('../helpers/normalize_reference');


module.exports = function links(state, silent) {
  var labelStart,
      labelEnd,
      label,
      href,
      title,
      pos,
      ref,
      code,
      isImage = false,
      oldPos = state.pos,
      max = state.posMax,
      start = state.pos,
      marker = state.src.charCodeAt(start);

  if (marker === 0x21/* ! */) {
    isImage = true;
    marker = state.src.charCodeAt(++start);
  }

  if (marker !== 0x5B/* [ */) { return false; }
  if (state.level >= state.options.maxNesting) { return false; }

  labelStart = start + 1;
  labelEnd = parseLinkLabel(state, start);

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

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

    // [link](  <href>  "title"  )
    //        ^^ skipping these spaces
    pos++;
    for (; pos < max; pos++) {
      code = state.src.charCodeAt(pos);
      if (code !== 0x20 && code !== 0x0A) { break; }
    }
    if (pos >= max) { return false; }

    // [link](  <href>  "title"  )
    //          ^^^^^^ parsing link destination
    start = pos;
    if (parseLinkDestination(state, pos)) {
      href = state.linkContent;
      pos = state.pos;
    } else {
      href = '';
    }

    // [link](  <href>  "title"  )
    //                ^^ skipping these spaces
    start = pos;
    for (; pos < max; pos++) {
      code = state.src.charCodeAt(pos);
      if (code !== 0x20 && code !== 0x0A) { break; }
    }

    // [link](  <href>  "title"  )
    //                  ^^^^^^^ parsing link title
    if (pos < max && start !== pos && parseLinkTitle(state, pos)) {
      title = state.linkContent;
      pos = state.pos;

      // [link](  <href>  "title"  )
      //                         ^^ skipping these spaces
      for (; pos < max; pos++) {
        code = state.src.charCodeAt(pos);
        if (code !== 0x20 && code !== 0x0A) { break; }
      }
    } else {
      title = '';
    }

    if (pos >= max || state.src.charCodeAt(pos) !== 0x29/* ) */) {
      state.pos = oldPos;
      return false;
    }
    pos++;
  } else {
    //
    // Link reference
    //

    // do not allow nested reference links
    if (state.linkLevel > 0) { return false; }

    // [foo]  [bar]
    //      ^^ optional whitespace (can include newlines)
    for (; pos < max; pos++) {
      code = state.src.charCodeAt(pos);
      if (code !== 0x20 && code !== 0x0A) { break; }
    }

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

    if (isImage) {
      state.push({
        type: 'image',
        src: href,
        title: title,
        alt: state.src.substr(labelStart, labelEnd - labelStart),
        level: state.level
      });
    } else {
      state.push({
        type: 'link_open',
        href: href,
        title: title,
        level: state.level++
      });
      state.linkLevel++;
      state.parser.tokenize(state);
      state.linkLevel--;
      state.push({ type: 'link_close', level: --state.level });
    }
  }

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