document.addEventListener('DOMContentLoaded', function() {
  // params from $_GET
  const node_id = 'hoelper_frame';
  const base = 'https://hoelper.anderreihe.de';
  const lang = '';
  const app = 'index';
  const iframeId = '' || randomId();
  const hideLogo = '';

  // create iframe
  if (document.getElementById(iframeId)) {
    console.error('Element with id ' + iframeId + ' already exists');
    return;
  }

  const iframe = document.createElement('iframe');
  iframe.id = iframeId;
  iframe.src = app === 'index'
               ? (base)
               : (base + '/' + app + '.html');

  const code = window.location
      .search
      .split('?')
      .pop()
      .split('&')
      .map(keyValue => keyValue.split('='))
      .map(entry => Object.fromEntries([entry]))
      .reduce((current, prev) => Object.assign(prev, current), {})
      ?.booking_code;

  const params = {};

  if (code) {
    params.code = code;
  }

  if (lang) {
    params.lang = lang;
  }

  if (hideLogo) {
    params.hide_logo = 'yes';
  }

  const paramsString = Object.entries(params)
      .map(entry => entry.join('='))
      .join('&');

  iframe.src += '?' + paramsString;

  // append iframe
  const node = document.getElementById(node_id);
  if (!node) {
    console.error('Element with id ' + node_id + ' not found');
    return;
  }

  node.appendChild(iframe);

  // add page height listener for the appended iframe
  (function() {
    const handlers = [];

    function iframeResize(id) {
      const iframe = document.getElementById(id);

      if (!iframe) {
        return;
      }

      handlers.push(function(event) {
        if (typeof event.data !== 'object') {
          return;
        }

        if (event.source !== iframe.contentWindow) {
          return;
        }

        if (event.data.type === 'Embed.heightChange') {
          if (event.data.height > 0) {
            iframe.style.height = (event.data.height) + 'px';
          }
        }
      });
    }

    window.addEventListener('message', function(event) {
      handlers.forEach(function(handler) {
        handler(event);
      });
    }, false);

    iframeResize(iframeId);
  })();

  // create default iframe styles
  const style = document.createElement('style');
  if (!style) {
    console.error('unable to create style tag');
    return;
  }
  style.id = 'styles_' + iframeId;
  style.innerText += '#' + node_id + ' {position: relative;} ';
  style.innerText += '#' + iframeId + ' {border: none;} ';

  document.head.appendChild(style);

  // helper functions
  function randomId(min = 1000, max = 10000) { // min and max included
    const randomInt = Math.floor(Math.random() * (max - min + 1) + min);
    const randomString = btoa(randomInt.toString()).replace(/=/gi, 'x');

    return ['id', randomString].join('_');
  }
});