async function postData(url = '', data = {}) {
  document.getElementById("submitButton").setAttribute("disabled", "disabled");

  const formData = new FormData();
  formData.append('data', JSON.stringify(data));
  // Default options are marked with *
  const response = await fetch(url, {
    method: 'POST', // *GET, POST, PUT, DELETE, etc.
    mode: 'cors', // no-cors, *cors, same-origin
    cache: 'no-cache', // *default, no-cache, reload, force-cache, only-if-cached
    credentials: 'same-origin', // include, *same-origin, omit
    headers: {
      'Accept': 'application/json; charset=UTF-8',
      'Content-Type': 'application/json; charset=UTF-8',
      'Content-Length': JSON.stringify(data).length.toString(),
      'Authorization': 'Bearer token_guest'
    },
    redirect: 'follow', // manual, *follow, error
    referrerPolicy: 'no-referrer', // no-referrer, *no-referrer-when-downgrade, origin, origin-when-cross-origin, same-origin, strict-origin, strict-origin-when-cross-origin, unsafe-url
    body: JSON.stringify(data) // body data type must match "Content-Type" header
  });
  return response.json(); // parses JSON response into native JavaScript objects
}

  function saveRegistration() {
    //var passType = document.getElementById('passType');
    //var value = passType.options[passType.selectedIndex].value;
    var passType = document.querySelector('input[name="passType"]:checked').value

    const classGroup = document.querySelector('input[name="class"]:checked');
    let classId = null;
    if (classGroup != null) classId = classGroup.value;

    const typeGroup = document.querySelector('input[name="type"]:checked');
    let type = null;
    if (typeGroup != null) type = typeGroup.value;

    const promo = document.getElementById("promo");

      postData('/moja/api3/saveregistration.php', {
        id: classId,
        passType: passType, //passType.options[passType.selectedIndex].value,
        name: document.getElementById("name").value,
        surname: document.getElementById("surname").value,
        email: document.getElementById("email").value,
        partnerName: document.getElementById("partnerName").value,
        partnerSurname: document.getElementById("partnerSurname").value,
        classes: [ { id: classId, person: passType < 2 ? [0] : [0, 1], code: promo != null ? promo.value : "" } ],
        lang: document.getElementById("lang").value,
        type: type,
        web: true
       })
      .then(msg => {
        console.log(msg);
          if (msg.status === 'ok') {
              if (msg.redirectUrl != null) {
                window.location.href = msg.redirectUrl;
                fbq('track', 'CompleteRegistration', {content_name: "class" + classId});
                return;
              }

              const name =  document.getElementById("name").value;
              if (msg.paymentType == 1) {
                document.getElementById("popup").innerHTML = name + ", hvala za prijavo!<br><br> Na email naslov smo poslali podatke za plačilo. Če emaila ne najdete, prosim najprej preverite, če je slučajno zataval v mapo z nezaželeno pošto.";
              } else {
                document.getElementById("popup").innerHTML = name + ", hvala za prijavo na tečaj!<br><br> Na email smo poslali potrditev prijave. Če emaila ne najdete, prosim najprej preverite, če je slučajno zataval v mapo z neželeno pošto.";
              }
              document.getElementById("popupBackground").classList.remove("hide");
              fbq('track', 'CompleteRegistration', {content_name: "class" + classId});
          } else if (msg.status === 'fail' && msg.error != null) {
              if (msg.error == "already registered") document.getElementById("popup").innerHTML = "Oseba s tem emailom je že prijavljena. Ponovna prijava ni potrebna.";
              else if (msg.error == "invalid code") document.getElementById("popup").innerHTML = "Promocijska koda ni veljavna.";
              else if (msg.error == "invalid request") document.getElementById("popup").innerHTML = "Vnešeni podatki niso veljavni.";
              else if (msg.error == "leaders closed") document.getElementById("popup").innerHTML = "Prijave za plesalce so za ta tečaj trenutno zaprte.";
              else if (msg.error == "followers closed") document.getElementById("popup").innerHTML = "Prijave za plesalke so zaradi povečanega števila plesalk za ta tečaj trenutno zaprte. Hvala za razumevanje.";
              else if (msg.error == "couples closed") document.getElementById("popup").innerHTML = "Prijave za pare so za ta tečaj trenutno zaprte. Hvala za razumevanje.";
              else document.getElementById("popup").innerHTML = "Ne moremo zabeležiti vaše prijave. Prosimo, da nas kontaktirate.";
              document.getElementById("popupBackground").classList.remove("hide");
          } else {
              document.getElementById("popup").innerHTML = "Ne moremo zabeležiti vaše prijave. Prosimo, da nas kontaktirate.";
              document.getElementById("popupBackground").classList.remove("hide");
          }
          document.getElementById("submitButton").removeAttribute("disabled");
      })
      .catch((error) => {
          document.getElementById("popup").innerHTML = "Težave pri povezovanju na strežnik.";
          document.getElementById("popupBackground").classList.remove("hide");
          document.getElementById("submitButton").removeAttribute("disabled");
      });
  }

  function selectType() {
    const typeGroup = document.querySelector('input[name="passType"]:checked');
    let typeId = null;
    if (typeGroup != null) typeId = typeGroup.value;

    if (Number(typeId) >= 2) {
      document.getElementById('coupleForm').classList.remove("hide");
    } else {
      document.getElementById('coupleForm').classList.add("hide");
    }
  }

  function selectClass() {
    if (document.getElementById('class').selectedIndex == 0) {
      document.getElementById('passType').disabled = false;
    } else {
      document.getElementById('passType').value = '1';
      document.getElementById('passType').disabled = true;
      document.getElementById('coupleForm').classList.add("hide");
      document.getElementById('partnerName').value='';
      document.getElementById('partnerSurname').value='';
    }
  }

  function closePopup() {
    document.getElementById("popupBackground").classList.add("hide");
  }

  //document.getElementById("class").addEventListener("change", selectClass);
  document.getElementById("submitButton").addEventListener("click", saveRegistration);
  document.getElementById("popupBackground").addEventListener("click", closePopup);
  document.getElementById("popupClose").addEventListener("click", closePopup);

  var passTypeRadios = document.querySelectorAll('input[type=radio][name="passType"]');
  passTypeRadios.forEach(radio => radio.addEventListener('change', selectType));