background.js

/*
# This Source Code Form is subject to the terms of the Mozilla Public
# License, v. 2.0. If a copy of the MPL was not distributed with this
# file, You can obtain one at http://mozilla.org/MPL/2.0/.
*/
'use strict';

// original: https://gist.github.com/piroor/14e42c7eeb876ab71e3202dabcd0ee9e#file-toc-js

function generate() {
  var container = document.querySelector('.markdown-body');
  var tab = document.querySelector('.preview-tab');
  tab.click();
  setTimeout(function waitPreview(retryCount) {
    container = document.querySelector('.preview-content .markdown-body');
    if (!container || (retryCount < 10 && !generateToC()))
      setTimeout(waitPreview, 250, retryCount + 1);
  }, 250, 0);

  function generateToC() {
    var headings = container.querySelectorAll('h1, h2, h3, h4, h5, h6');
    if (headings.length == 0)
      return false;
    var minLevel = 6;
    for (let heading of headings) {
      let headingLevel = parseInt(heading.localName.charAt(1));
      if (headingLevel < minLevel)
        minLevel = headingLevel;
    }
    var toc = [];
    for (let heading of headings) {
      let anchor = heading.querySelector('a.anchor[href]') || heading.parentNode.querySelector('a.anchor[href]');
      if (!anchor)
        throw new Error(`Could not find out anchor for a heading: ${heading.textContent}`);
      let href = anchor.getAttribute('href');
      let indent = '';
      let headingLevel = parseInt(heading.localName.charAt(1));
      for (let level = headingLevel - minLevel; level > 0; level--) {
        indent += '  ';
      }
      toc.push(`${indent}* [${heading.textContent.trim().replace(/\s\s+/g, ' ')}](${href})`);
    }
    var source = `<!--ToC-->
${toc.join('\n')}
 
<small>(generated by [Table of Contents Generator for GitHub Wiki](https://addons.mozilla.org/firefox/addon/toc-generator-for-github-wiki/))</small>
<!--/ToC-->`;

    let tab = document.querySelector('.write-tab');
    tab.click();
    setTimeout(function updateToC(retryCount) {
      var field = document.querySelector('#gollum-editor-body');
      if (retryCount < 10 && !field.value)
        return setTimeout(updateToC, 250, retryCount);

      var matcher = /<!--ToC-->\n(.*\n)*<!--\/ToC-->/;
      if (matcher.test(field.value))
        field.value = field.value.replace(matcher, source);
      else
        field.value = `${source}
${field.value}`;
    }, 250, 0);
  }
}

browser.browserAction.onClicked.addListener(async (aTab) => {
  var baseURL = aTab.url.split('#')[0].split('?')[0];
  var isWikiPage = /https:\/\/github.com\/[^\/]+\/[^\/]+\/wiki($|\/)/.test(baseURL);
  if (!isWikiPage)
    return;

  var isEditPage = /\/_edit$/.test(baseURL);
  if (!isEditPage) {
    var waitUntilLoaded = new Promise((aResolve, aReject) => {
      let onUpdated = (aTabId, aChangeInfo, aCompleteTab) => {
        if (aTabId != aTab.id ||
            aChangeInfo.status != 'complete')
          return;
        browser.tabs.onUpdated.removeListener(onUpdated);
        aResolve();
      };
      browser.tabs.onUpdated.addListener(onUpdated);
    });
    await browser.tabs.update(aTab.id, {
      url: baseURL += '/_edit'
    });
    await waitUntilLoaded;
  }
  browser.tabs.executeScript(aTab.id, {
    code: `(${generate.toString()})()`
  });
});