/**
 * Track Spreadsheet views with Google Analytics
 *
 * @param {string} gaaccount Google Analytics Account like UA-1234-56.
 * @param {string} spreadsheet Name of the Google Spreadsheet.
 * @param {string} sheetname Name of individual Google Sheet.
 * @return The 1x1 tracking GIF image
 * @customfunction
 */

function GOOGLEANALYTICS(gaaccount, spreadsheet, sheetname) {
  /**
   * Written by Amit Agarwal
   * Web: www.ctrlq.org
   * Email: amit@labnol.org
   */

  /* Random ID to prevent browser caching */
  var cache_buster = Math.round(Date.now() / 1000).toString();

  /* Client ID to anonymously define the device */
  var client_id = Utilities.getUuid();

  // Event Category set to Google Spreadsheets
  var event_category = encodeURIComponent('Google Spreadsheets');

  // Event Action set to spreadsheet title
  var event_action = encodeURIComponent(spreadsheet || 'Spreadsheet');

  // Event Label set to sheet title
  var event_label = encodeURIComponent(sheetname || 'Sheet');

  var imageURL = [
    'https://ssl.google-analytics.com/collect?v=1&t=event',
    '&tid=' + gaaccount,
    '&cid=' + client_id,
    '&z=' + cache_buster,
    '&ec=' + event_category,
    '&ea=' + event_action,
    '&el=' + event_label,
  ].join('');

  return imageURL;
}