/**
 * @file
 * Enable Parallax effect for any block created by the user
 *
 * This module enables the user to select none, Same, or Opposite directions
 * when creating a block. Selecting Same or Opposite places a data attribute
 * which is ready by the attached javascript file, and then targeted for
 * calculations causing parallax effect based on 'same' or 'opposite' value.
 */

(function ($, Drupal, window, document, undefined) {

  Drupal.behaviors.parallax_admin = {
    attach: function(context, settings) {

    $(function() {

      // Enable parallax only if not mobile device
      if (/Android|webOS|iPhone|iPad|iPod|BlackBerry|IEMobile|Opera Mini/i.test(navigator.userAgent) === false) {
        enableParallax(parallaxItems);
      }
    });
    }
  };

  // This function currently accepts an array of target selectors in the form
  // of strings, cycled through for parallax effects.
  function enableParallax(targetsObj) {
    $.each(targetsObj, function() {

      var currentObj = this;

      // check if object exists on page
      if ($(currentObj[0]).length > 0) {
        $(window).load(function() {
          parallaxCalculation(currentObj);
        });
        $(window).scroll(function() {
          parallaxCalculation(currentObj);
        });
        $(window).resize(function() {
          parallaxCalculation(currentObj);
        });
      }
    });
  }

  // Determines if each element passed to enableParallax is in the viewport and
  // passes through TRUE when element dimensions first are visible in viewport
  function isScrolledIntoView(elem) {
    var docViewTop = $(window).scrollTop();
    var docViewBottom = docViewTop + $(window).height();

    if (elem.offset() !== null) {
      var elemTop = elem.offset().top;
      var elemBottom = elemTop + elem.height();
      return ((elemTop <= docViewBottom) && (elemBottom >= docViewTop));
    } else {
      return true;
    }
  }

  function parallaxCalculation(currentObj) {
    var $currentSelector = $(currentObj[0]);
    var verticalValue = currentObj[1];
    var horizontalValue = currentObj[2];

    if (isScrolledIntoView($currentSelector)) {   //On Scroll or Load, check if object is in view
      // Calculate position of top of target element relative to top of page
      // and height of target element
      var divTop = $currentSelector.offset().top;
      var divHeight = $currentSelector.height();

      // Calculate distance scrolled from top, the center of the viewport
      // (necessary for calculations), and the height of the viewport
      var docViewTop = $(window).scrollTop();
      var docViewSize = $(window).height();
      var docViewCenter = docViewTop + (docViewSize / 2);

      // Calculate the full range of effective parallax movement on the page
      var fullRange = docViewSize + divHeight;

      // My head hurts too much to explain this one. Ask Kyle.
      var currPosition = docViewCenter - (divTop - (docViewSize / 2));

      // Calculate percentage location of current position baseed on full range of parallax movement
      var currVerticalPercentage = (currPosition / fullRange) * 100;
      var currHorizontalPercentage = (currPosition / fullRange) * 100;

      // Determines if vertical parallax direction is opposite, and invertes the value
      // on a scale of 1-100
      if (verticalValue.indexOf("bottom-to-top") > -1) {
        $currentSelector.attr("data-position-vertical", currVerticalPercentage);
        currVerticalPercentage = 100 - $currentSelector.attr("data-position-vertical");
      }
      if (horizontalValue.indexOf("right-to-left") > -1) {
        $currentSelector.attr("data-position-horizontal", currHorizontalPercentage);
        currHorizontalPercentage = 100 - $currentSelector.attr("data-position-horizontal");
      }

      // Horizontal Background Percentage
      if (horizontalValue != "none") {
        coords = currHorizontalPercentage + "%";
      } else {
        coords = "50%";
      }

      // Vertical Background Percentage
      if (verticalValue != "none") {
        coords += " " + currVerticalPercentage + "%";
      } else {
        coords += " 50%";
      }

      // Apply background Position and apply background-size: Cover to avoid image tiling
      $currentSelector.css({ "backgroundPosition": coords });
    }
  }
})(jQuery, Drupal, this, this.document);