discourse/app/assets/javascripts/discourse/lib/link-mentions.js.es6

import { ajax } from 'discourse/lib/ajax';
import { userPath } from 'discourse/lib/url';

function replaceSpan($e, username, opts) {
  let extra = "";
  let extraClass = "";

  if (opts && opts.group) {
    if (opts.mentionable) {
      extra = `data-name='${username}' data-mentionable-user-count='${opts.mentionable.user_count}'`;
      extraClass = "notify";
    }
    $e.replaceWith(`<a href='${Discourse.getURL("/groups/") + username}' class='mention-group ${extraClass}' ${extra}>@${username}</a>`);
  } else {
    if (opts && opts.cannot_see) {
      extra = `data-name='${username}'`;
      extraClass = "cannot-see";
    }
    $e.replaceWith(`<a href='${userPath(username.toLowerCase())}' class='mention ${extraClass}' ${extra}>@${username}</a>`);
  }
}

const found = {};
const foundGroups = {};
const mentionableGroups = {};
const checked = {};
const cannotSee = [];

function updateFound($mentions, usernames) {
  Ember.run.scheduleOnce('afterRender', function() {
    $mentions.each((i, e) => {
      const $e = $(e);
      const username = usernames[i];
      if (found[username.toLowerCase()]) {
        replaceSpan($e, username, { cannot_see: cannotSee[username] });
      } else if (foundGroups[username]) {
        replaceSpan($e, username, { group: true, mentionable: mentionableGroups[username] });
      } else if (checked[username]) {
        $e.addClass('mention-tested');
      }
    });
  });
}

export function linkSeenMentions($elem, siteSettings) {
  const $mentions = $('span.mention:not(.mention-tested)', $elem);
  if ($mentions.length) {
    const usernames = $mentions.map((_, e) => $(e).text().substr(1));
    updateFound($mentions, usernames);
    return _.uniq(usernames).filter(u => !checked[u] && u.length >= siteSettings.min_username_length);
  }
  return [];
}

// 'Create a New Topic' scenario is not supported (per conversation with codinghorror)
// https://meta.discourse.org/t/taking-another-1-7-release-task/51986/7
export function fetchUnseenMentions(usernames, topic_id) {
  return ajax(userPath("is_local_username"), { data: { usernames, topic_id } }).then(r => {
    r.valid.forEach(v => found[v] = true);
    r.valid_groups.forEach(vg => foundGroups[vg] = true);
    r.mentionable_groups.forEach(mg => mentionableGroups[mg.name] = mg);
    r.cannot_see.forEach(cs => cannotSee[cs] = true);
    usernames.forEach(u => checked[u] = true);
    return r;
  });
}