// ==UserScript==
// @name           UltimateGuitar Library Downloader
// @description    It adds a "Download as JSON" button to the mytabs page on UltimateGuitar.
// @author         Fabio "Blacklight" Manganiello
// @version        1.0
// @grant          none
// @match          https://www.ultimate-guitar.com/user/mytabs
// ==/UserScript==

/**
 * There are two ways to use this script:
 *
 * 1. Install it as a Greasemonkey script (or whatever extension you use for custom UserScript).
 *    Every time you browse to your UltimateGuitar page, the Download button will appear next to
 *    the header.
 *
 * 2. Manually paste the code in the browser developer console - the button will be added on the
 *    fly. You can also manually call `getTabs` from the developer console to access, filter
 *    and manipulate the list of objects.
 */


function getTabs() {
  let artist = null;
  return [
    ...document.querySelector('article[isdesktop=true] div').childNodes
  ].slice(1).map(item => {
    const childNodes = [...item.childNodes];
    const parsedItem = {};

    if (childNodes.length > 0) {
      const cellContent = childNodes[0].innerText.trim();
      if (cellContent.length)
        artist = cellContent;
    }

    if (childNodes.length > 1) {
      const cellContent = childNodes[1].innerText.trim();
      if (cellContent.length)
        parsedItem.title = cellContent;

      const link = childNodes[1].querySelector('a').getAttribute('href');
      if (link.length)
        parsedItem.link = link;
    }

    if (!artist && parsedItem.title)
      return;

    parsedItem.artist = artist;
    return parsedItem;
  }).filter(item => item)
}

function addDownloadButton() {
  const header = document.querySelector('main section header');
  if (!header)
    return;

  if (header.querySelector('button.__download-btn'))
    return;

  const tabs = 'data:application/json,' + encodeURIComponent(JSON.stringify(getTabs()));
  const btn = document.createElement('a');
  btn.download = 'tabs.json';
  btn.innerHTML = 'Download tabs as JSON';
  btn.style = 'color: #ffc600; text-decoration: underline';
  btn.href = tabs;
  header.querySelector('section').appendChild(btn);
}

window.onload = addDownloadButton;