function initSession() {
  // On page load, set the country to Russia and initialise the price
  fastspring.builder.country("RU");
  updatePrice();
}

function updatePrice() {
  // Use FastSpring's Secure Calls feature to pre-fill the customer's information and dynamically set the price based on the number of credits that the user wants to purchase.
  
  // Documentation: 
  // https://fastspring.com/docs/passing-sensitive-data-with-secure-requests/
  
      var price = document.getElementById("credits").value;
  
      // Secure Call
      fastspring.builder.secure({
				"contact": {
          "email":"aharvey@fastspring.com",
          "firstName":"Adam",
          "lastName":"Harvey"
				},
        "items": [{
            "product": "sms-activate",
            "quantity": 1,
            "pricing": {
                "price": {
                    "USD": price
                }
            }
        }]
    });
}

function callFastSpringCheckout() {
  // Launch FastSpring's pop-up checkout for the customer to complete their purchase.
  updatePrice();
  fastspring.builder.checkout();
}

function dataCallback(data) {
  // Callback to update the price
  // Documentation: 
  // https://fastspringexamples.com/callback/data-data-callback/
  var orderPrice = data.total;
  document.getElementById("price").innerHTML = orderPrice;
  
}

// Modal JavaScript
// ------------------------------------
var modal = document.getElementById("myModal");

// Get the button that opens the modal
var btn = document.getElementById("myBtn");

// Get the <span> element that closes the modal
var span = document.getElementsByClassName("close")[0];

// When the user clicks on the button, open the modal
btn.onclick = function() {
  modal.style.display = "block";
}

// When the user clicks on <span> (x), close the modal
span.onclick = function() {
  modal.style.display = "none";
}

// When the user clicks anywhere outside of the modal, close it
window.onclick = function(event) {
  if (event.target == modal) {
    modal.style.display = "none";
  }
}