function FullPic(sourceFile, caption) {
  
  this.sourceFile = sourceFile;
  this.caption = document.getElementById("ad-image").alt;
}

FullPic.prototype.open = function() {
  
  /*This element gets appended before lightbox is faded in so that elements with high z-index don't cover lightbox during fade. */
  this.lightboxWrapper = document.createElement('div');
  this.lightboxWrapper.className = 'lightbox-wrapper';
  
  this.lightbox = document.createElement('div');

  var overlayDiv = document.createElement('div');
  overlayDiv.className = 'overlay';
  
  var image = document.createElement('img');
  image.className = 'expanded';
  image.src = this.sourceFile;
  
  var captionDiv = document.createElement('div');
  captionDiv.className = 'caption';
  var captionText = document.createTextNode(this.caption);
  captionDiv.appendChild(captionText);
  
  var columnWrapper = document.querySelector('#column-wrapper');
  
  this.lightbox.appendChild(overlayDiv);
  this.lightbox.appendChild(image);
  this.lightbox.appendChild(captionDiv);

  /*Fade in lightbox overlay and image.*/
  document.body.insertBefore(this.lightboxWrapper, columnWrapper);
  this.lightbox.style.opacity = 0;
  this.lightboxWrapper.appendChild(this.lightbox);  /*Appended first for z-index fix (see comment above).*/
  var counter = 0;
  var lightBox = this.lightbox;  /* Otherwise "this" in callback function would refer to call function rather than FullPic property. */
  var fadeInt = setInterval(function() {
    if (counter < 1.05) {
      lightBox.style.opacity = counter;
      counter += 0.05;
    } else {
    	clearInterval(fadeInt);
    }
  }, 15);
  
  /* Without passing "this" to "self", "this" would refer to event listener in callback function. */
  var self = this;
  overlayDiv.addEventListener('click', function() {
    self.close();
  });

};

FullPic.prototype.close = function() {
  
  var counter = 1;
  var lightBox = this.lightbox;
  var lightWrap = this.lightboxWrapper;
  var fadeInt = setInterval(function() {
    if (counter > 0) {
      lightBox.style.opacity = counter;
      counter -= 0.05;
    } else {
    	clearInterval(fadeInt);
    	document.body.removeChild(lightWrap);
    }
  }, 15);
  
};


/* Adds event listener to each thumbnail with 'lightbox-photo' class on page */

function initLightbox() {
  
  var photos = Array.prototype.slice.call(document.querySelectorAll('.lightbox-photo'));

  photos.forEach(function(photo) {
    
    photo.addEventListener('click', function() {
      
      var currentPhoto = new FullPic(photo.src, photo.dataset.caption, photo.dataset.orientation);
      currentPhoto.open();
      
    });
    
  });

}
window.onload = initLightbox;