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Filename : shuffle.js
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(function (global, factory) {
  typeof exports === 'object' && typeof module !== 'undefined' ? module.exports = factory() :
  typeof define === 'function' && define.amd ? define(factory) :
  (global = typeof globalThis !== 'undefined' ? globalThis : global || self, global.Shuffle = factory());
})(this, (function () { 'use strict';

  var tinyEmitter = {exports: {}};

  function E() {// Keep this empty so it's easier to inherit from
    // (via https://github.com/lipsmack from https://github.com/scottcorgan/tiny-emitter/issues/3)
  }

  E.prototype = {
    on: function (name, callback, ctx) {
      var e = this.e || (this.e = {});
      (e[name] || (e[name] = [])).push({
        fn: callback,
        ctx: ctx
      });
      return this;
    },
    once: function (name, callback, ctx) {
      var self = this;

      function listener() {
        self.off(name, listener);
        callback.apply(ctx, arguments);
      }
      listener._ = callback;
      return this.on(name, listener, ctx);
    },
    emit: function (name) {
      var data = [].slice.call(arguments, 1);
      var evtArr = ((this.e || (this.e = {}))[name] || []).slice();
      var i = 0;
      var len = evtArr.length;

      for (i; i < len; i++) {
        evtArr[i].fn.apply(evtArr[i].ctx, data);
      }

      return this;
    },
    off: function (name, callback) {
      var e = this.e || (this.e = {});
      var evts = e[name];
      var liveEvents = [];

      if (evts && callback) {
        for (var i = 0, len = evts.length; i < len; i++) {
          if (evts[i].fn !== callback && evts[i].fn._ !== callback) liveEvents.push(evts[i]);
        }
      } // Remove event from queue to prevent memory leak
      // Suggested by https://github.com/lazd
      // Ref: https://github.com/scottcorgan/tiny-emitter/commit/c6ebfaa9bc973b33d110a84a307742b7cf94c953#commitcomment-5024910


      liveEvents.length ? e[name] = liveEvents : delete e[name];
      return this;
    }
  };
  tinyEmitter.exports = E;
  tinyEmitter.exports.TinyEmitter = E;

  var arrayParallel = function parallel(fns, context, callback) {
    if (!callback) {
      if (typeof context === 'function') {
        callback = context;
        context = null;
      } else {
        callback = noop;
      }
    }

    var pending = fns && fns.length;
    if (!pending) return callback(null, []);
    var finished = false;
    var results = new Array(pending);
    fns.forEach(context ? function (fn, i) {
      fn.call(context, maybeDone(i));
    } : function (fn, i) {
      fn(maybeDone(i));
    });

    function maybeDone(i) {
      return function (err, result) {
        if (finished) return;

        if (err) {
          callback(err, results);
          finished = true;
          return;
        }

        results[i] = result;
        if (! --pending) callback(null, results);
      };
    }
  };

  function noop() {}

  /**
   * Always returns a numeric value, given a value. Logic from jQuery's `isNumeric`.
   * @param {*} value Possibly numeric value.
   * @return {number} `value` or zero if `value` isn't numeric.
   */
  function getNumber(value) {
    return parseFloat(value) || 0;
  }

  class Point {
    /**
     * Represents a coordinate pair.
     * @param {number} [x=0] X.
     * @param {number} [y=0] Y.
     */
    constructor(x, y) {
      this.x = getNumber(x);
      this.y = getNumber(y);
    }
    /**
     * Whether two points are equal.
     * @param {Point} a Point A.
     * @param {Point} b Point B.
     * @return {boolean}
     */


    static equals(a, b) {
      return a.x === b.x && a.y === b.y;
    }

  }

  class Rect {
    /**
     * Class for representing rectangular regions.
     * https://github.com/google/closure-library/blob/master/closure/goog/math/rect.js
     * @param {number} x Left.
     * @param {number} y Top.
     * @param {number} w Width.
     * @param {number} h Height.
     * @param {number} id Identifier
     * @constructor
     */
    constructor(x, y, w, h, id) {
      this.id = id;
      /** @type {number} */

      this.left = x;
      /** @type {number} */

      this.top = y;
      /** @type {number} */

      this.width = w;
      /** @type {number} */

      this.height = h;
    }
    /**
     * Returns whether two rectangles intersect.
     * @param {Rect} a A Rectangle.
     * @param {Rect} b A Rectangle.
     * @return {boolean} Whether a and b intersect.
     */


    static intersects(a, b) {
      return a.left < b.left + b.width && b.left < a.left + a.width && a.top < b.top + b.height && b.top < a.top + a.height;
    }

  }

  var Classes = {
    BASE: 'shuffle',
    SHUFFLE_ITEM: 'shuffle-item',
    VISIBLE: 'shuffle-item--visible',
    HIDDEN: 'shuffle-item--hidden'
  };

  let id$1 = 0;

  class ShuffleItem {
    constructor(element, isRTL) {
      id$1 += 1;
      this.id = id$1;
      this.element = element;
      /**
       * Set correct direction of item
       */

      this.isRTL = isRTL;
      /**
       * Used to separate items for layout and shrink.
       */

      this.isVisible = true;
      /**
       * Used to determine if a transition will happen. By the time the _layout
       * and _shrink methods get the ShuffleItem instances, the `isVisible` value
       * has already been changed by the separation methods, so this property is
       * needed to know if the item was visible/hidden before the shrink/layout.
       */

      this.isHidden = false;
    }

    show() {
      this.isVisible = true;
      this.element.classList.remove(Classes.HIDDEN);
      this.element.classList.add(Classes.VISIBLE);
      this.element.removeAttribute('aria-hidden');
    }

    hide() {
      this.isVisible = false;
      this.element.classList.remove(Classes.VISIBLE);
      this.element.classList.add(Classes.HIDDEN);
      this.element.setAttribute('aria-hidden', true);
    }

    init() {
      this.addClasses([Classes.SHUFFLE_ITEM, Classes.VISIBLE]);
      this.applyCss(ShuffleItem.Css.INITIAL);
      this.applyCss(this.isRTL ? ShuffleItem.Css.DIRECTION.rtl : ShuffleItem.Css.DIRECTION.ltr);
      this.scale = ShuffleItem.Scale.VISIBLE;
      this.point = new Point();
    }

    addClasses(classes) {
      classes.forEach(className => {
        this.element.classList.add(className);
      });
    }

    removeClasses(classes) {
      classes.forEach(className => {
        this.element.classList.remove(className);
      });
    }

    applyCss(obj) {
      Object.keys(obj).forEach(key => {
        this.element.style[key] = obj[key];
      });
    }

    dispose() {
      this.removeClasses([Classes.HIDDEN, Classes.VISIBLE, Classes.SHUFFLE_ITEM]);
      this.element.removeAttribute('style');
      this.element = null;
    }

  }

  ShuffleItem.Css = {
    INITIAL: {
      position: 'absolute',
      top: 0,
      visibility: 'visible',
      willChange: 'transform'
    },
    DIRECTION: {
      ltr: {
        left: 0
      },
      rtl: {
        right: 0
      }
    },
    VISIBLE: {
      before: {
        opacity: 1,
        visibility: 'visible'
      },
      after: {
        transitionDelay: ''
      }
    },
    HIDDEN: {
      before: {
        opacity: 0
      },
      after: {
        visibility: 'hidden',
        transitionDelay: ''
      }
    }
  };
  ShuffleItem.Scale = {
    VISIBLE: 1,
    HIDDEN: 0.001
  };

  let value = null;
  var testComputedSize = (() => {
    if (value !== null) {
      return value;
    }

    const element = document.body || document.documentElement;
    const e = document.createElement('div');
    e.style.cssText = 'width:10px;padding:2px;box-sizing:border-box;';
    element.appendChild(e);
    const {
      width
    } = window.getComputedStyle(e, null); // Fix for issue #314

    value = Math.round(getNumber(width)) === 10;
    element.removeChild(e);
    return value;
  });

  /**
   * Retrieve the computed style for an element, parsed as a float.
   * @param {Element} element Element to get style for.
   * @param {string} style Style property.
   * @param {CSSStyleDeclaration} [styles] Optionally include clean styles to
   *     use instead of asking for them again.
   * @return {number} The parsed computed value or zero if that fails because IE
   *     will return 'auto' when the element doesn't have margins instead of
   *     the computed style.
   */

  function getNumberStyle(element, style) {
    let styles = arguments.length > 2 && arguments[2] !== undefined ? arguments[2] : window.getComputedStyle(element, null);
    let value = getNumber(styles[style]); // Support IE<=11 and W3C spec.

    if (!testComputedSize() && style === 'width') {
      value += getNumber(styles.paddingLeft) + getNumber(styles.paddingRight) + getNumber(styles.borderLeftWidth) + getNumber(styles.borderRightWidth);
    } else if (!testComputedSize() && style === 'height') {
      value += getNumber(styles.paddingTop) + getNumber(styles.paddingBottom) + getNumber(styles.borderTopWidth) + getNumber(styles.borderBottomWidth);
    }

    return value;
  }

  /**
   * Fisher-Yates shuffle.
   * http://stackoverflow.com/a/962890/373422
   * https://bost.ocks.org/mike/shuffle/
   * @param {Array} array Array to shuffle.
   * @return {Array} Randomly sorted array.
   */
  function randomize(array) {
    let n = array.length;

    while (n) {
      n -= 1;
      const i = Math.floor(Math.random() * (n + 1));
      const temp = array[i];
      array[i] = array[n];
      array[n] = temp;
    }

    return array;
  }

  const defaults = {
    // Use array.reverse() to reverse the results
    reverse: false,
    // Sorting function
    by: null,
    // Custom sort function
    compare: null,
    // If true, this will skip the sorting and return a randomized order in the array
    randomize: false,
    // Determines which property of each item in the array is passed to the
    // sorting method.
    key: 'element'
  };
  /**
   * You can return `undefined` from the `by` function to revert to DOM order.
   * @param {Array<T>} arr Array to sort.
   * @param {SortOptions} options Sorting options.
   * @return {Array<T>}
   */

  function sorter(arr, options) {
    const opts = { ...defaults,
      ...options
    };
    const original = Array.from(arr);
    let revert = false;

    if (!arr.length) {
      return [];
    }

    if (opts.randomize) {
      return randomize(arr);
    } // Sort the elements by the opts.by function.
    // If we don't have opts.by, default to DOM order


    if (typeof opts.by === 'function') {
      arr.sort((a, b) => {
        // Exit early if we already know we want to revert
        if (revert) {
          return 0;
        }

        const valA = opts.by(a[opts.key]);
        const valB = opts.by(b[opts.key]); // If both values are undefined, use the DOM order

        if (valA === undefined && valB === undefined) {
          revert = true;
          return 0;
        }

        if (valA < valB || valA === 'sortFirst' || valB === 'sortLast') {
          return -1;
        }

        if (valA > valB || valA === 'sortLast' || valB === 'sortFirst') {
          return 1;
        }

        return 0;
      });
    } else if (typeof opts.compare === 'function') {
      arr.sort(opts.compare);
    } // Revert to the original array if necessary


    if (revert) {
      return original;
    }

    if (opts.reverse) {
      arr.reverse();
    }

    return arr;
  }

  const transitions = {};
  const eventName = 'transitionend';
  let count = 0;

  function uniqueId() {
    count += 1;
    return eventName + count;
  }

  function cancelTransitionEnd(id) {
    if (transitions[id]) {
      transitions[id].element.removeEventListener(eventName, transitions[id].listener);
      transitions[id] = null;
      return true;
    }

    return false;
  }
  function onTransitionEnd(element, callback) {
    const id = uniqueId();

    const listener = evt => {
      if (evt.currentTarget === evt.target) {
        cancelTransitionEnd(id);
        callback(evt);
      }
    };

    element.addEventListener(eventName, listener);
    transitions[id] = {
      element,
      listener
    };
    return id;
  }

  function arrayMax(array) {
    return Math.max(...array);
  }

  function arrayMin(array) {
    return Math.min(...array);
  }

  /**
   * Determine the number of columns an items spans.
   * @param {number} itemWidth Width of the item.
   * @param {number} columnWidth Width of the column (includes gutter).
   * @param {number} columns Total number of columns
   * @param {number} threshold A buffer value for the size of the column to fit.
   * @return {number}
   */

  function getColumnSpan(itemWidth, columnWidth, columns, threshold) {
    let columnSpan = itemWidth / columnWidth; // If the difference between the rounded column span number and the
    // calculated column span number is really small, round the number to
    // make it fit.

    if (Math.abs(Math.round(columnSpan) - columnSpan) < threshold) {
      // e.g. columnSpan = 4.0089945390298745
      columnSpan = Math.round(columnSpan);
    } // Ensure the column span is not more than the amount of columns in the whole layout.


    return Math.min(Math.ceil(columnSpan), columns);
  }
  /**
   * Retrieves the column set to use for placement.
   * @param {number} columnSpan The number of columns this current item spans.
   * @param {number} columns The total columns in the grid.
   * @return {Array.<number>} An array of numbers represeting the column set.
   */

  function getAvailablePositions(positions, columnSpan, columns) {
    // The item spans only one column.
    if (columnSpan === 1) {
      return positions;
    } // The item spans more than one column, figure out how many different
    // places it could fit horizontally.
    // The group count is the number of places within the positions this block
    // could fit, ignoring the current positions of items.
    // Imagine a 2 column brick as the second item in a 4 column grid with
    // 10px height each. Find the places it would fit:
    // [20, 10, 10, 0]
    //  |   |   |
    //  *   *   *
    //
    // Then take the places which fit and get the bigger of the two:
    // max([20, 10]), max([10, 10]), max([10, 0]) = [20, 10, 10]
    //
    // Next, find the first smallest number (the short column).
    // [20, 10, 10]
    //      |
    //      *
    //
    // And that's where it should be placed!
    //
    // Another example where the second column's item extends past the first:
    // [10, 20, 10, 0] => [20, 20, 10] => 10


    const available = []; // For how many possible positions for this item there are.

    for (let i = 0; i <= columns - columnSpan; i++) {
      // Find the bigger value for each place it could fit.
      available.push(arrayMax(positions.slice(i, i + columnSpan)));
    }

    return available;
  }
  /**
   * Find index of short column, the first from the left where this item will go.
   *
   * @param {Array.<number>} positions The array to search for the smallest number.
   * @param {number} buffer Optional buffer which is very useful when the height
   *     is a percentage of the width.
   * @return {number} Index of the short column.
   */

  function getShortColumn(positions, buffer) {
    const minPosition = arrayMin(positions);

    for (let i = 0, len = positions.length; i < len; i++) {
      if (positions[i] >= minPosition - buffer && positions[i] <= minPosition + buffer) {
        return i;
      }
    }

    return 0;
  }
  /**
   * Determine the location of the next item, based on its size.
   * @param {Object} itemSize Object with width and height.
   * @param {Array.<number>} positions Positions of the other current items.
   * @param {number} gridSize The column width or row height.
   * @param {number} total The total number of columns or rows.
   * @param {number} threshold Buffer value for the column to fit.
   * @param {number} buffer Vertical buffer for the height of items.
   * @return {Point}
   */

  function getItemPosition(_ref) {
    let {
      itemSize,
      positions,
      gridSize,
      total,
      threshold,
      buffer
    } = _ref;
    const span = getColumnSpan(itemSize.width, gridSize, total, threshold);
    const setY = getAvailablePositions(positions, span, total);
    const shortColumnIndex = getShortColumn(setY, buffer); // Position the item

    const point = new Point(gridSize * shortColumnIndex, setY[shortColumnIndex]); // Update the columns array with the new values for each column.
    // e.g. before the update the columns could be [250, 0, 0, 0] for an item
    // which spans 2 columns. After it would be [250, itemHeight, itemHeight, 0].

    const setHeight = setY[shortColumnIndex] + itemSize.height;

    for (let i = 0; i < span; i++) {
      positions[shortColumnIndex + i] = setHeight;
    }

    return point;
  }
  /**
   * This method attempts to center items. This method could potentially be slow
   * with a large number of items because it must place items, then check every
   * previous item to ensure there is no overlap.
   * @param {Array.<Rect>} itemRects Item data objects.
   * @param {number} containerWidth Width of the containing element.
   * @return {Array.<Point>}
   */

  function getCenteredPositions(itemRects, containerWidth) {
    const rowMap = {}; // Populate rows by their offset because items could jump between rows like:
    // a   c
    //  bbb

    itemRects.forEach(itemRect => {
      if (rowMap[itemRect.top]) {
        // Push the point to the last row array.
        rowMap[itemRect.top].push(itemRect);
      } else {
        // Start of a new row.
        rowMap[itemRect.top] = [itemRect];
      }
    }); // For each row, find the end of the last item, then calculate
    // the remaining space by dividing it by 2. Then add that
    // offset to the x position of each point.

    let rects = [];
    const rows = [];
    const centeredRows = [];
    Object.keys(rowMap).forEach(key => {
      const itemRects = rowMap[key];
      rows.push(itemRects);
      const lastItem = itemRects[itemRects.length - 1];
      const end = lastItem.left + lastItem.width;
      const offset = Math.round((containerWidth - end) / 2);
      let finalRects = itemRects;
      let canMove = false;

      if (offset > 0) {
        const newRects = [];
        canMove = itemRects.every(r => {
          const newRect = new Rect(r.left + offset, r.top, r.width, r.height, r.id); // Check all current rects to make sure none overlap.

          const noOverlap = !rects.some(r => Rect.intersects(newRect, r));
          newRects.push(newRect);
          return noOverlap;
        }); // If none of the rectangles overlapped, the whole group can be centered.

        if (canMove) {
          finalRects = newRects;
        }
      } // If the items are not going to be offset, ensure that the original
      // placement for this row will not overlap previous rows (row-spanning
      // elements could be in the way).


      if (!canMove) {
        let intersectingRect;
        const hasOverlap = itemRects.some(itemRect => rects.some(r => {
          const intersects = Rect.intersects(itemRect, r);

          if (intersects) {
            intersectingRect = r;
          }

          return intersects;
        })); // If there is any overlap, replace the overlapping row with the original.

        if (hasOverlap) {
          const rowIndex = centeredRows.findIndex(items => items.includes(intersectingRect));
          centeredRows.splice(rowIndex, 1, rows[rowIndex]);
        }
      }

      rects = rects.concat(finalRects);
      centeredRows.push(finalRects);
    }); // Reduce array of arrays to a single array of points.
    // https://stackoverflow.com/a/10865042/373422
    // Then reset sort back to how the items were passed to this method.
    // Remove the wrapper object with index, map to a Point.

    return centeredRows.flat().sort((a, b) => a.id - b.id).map(itemRect => new Point(itemRect.left, itemRect.top));
  }

  /**
   * Hyphenates a javascript style string to a css one. For example:
   * MozBoxSizing -> -moz-box-sizing.
   * @param {string} str The string to hyphenate.
   * @return {string} The hyphenated string.
   */
  function hyphenate(str) {
    return str.replace(/([A-Z])/g, (str, m1) => `-${m1.toLowerCase()}`);
  }

  function arrayUnique(x) {
    return Array.from(new Set(x));
  } // Used for unique instance variables


  let id = 0;

  class Shuffle extends tinyEmitter.exports {
    /**
     * Categorize, sort, and filter a responsive grid of items.
     *
     * @param {Element} element An element which is the parent container for the grid items.
     * @param {Object} [options=Shuffle.options] Options object.
     * @constructor
     */
    constructor(element) {
      let options = arguments.length > 1 && arguments[1] !== undefined ? arguments[1] : {};
      super();
      this.options = { ...Shuffle.options,
        ...options
      };
      this.lastSort = {};
      this.group = Shuffle.ALL_ITEMS;
      this.lastFilter = Shuffle.ALL_ITEMS;
      this.isEnabled = true;
      this.isDestroyed = false;
      this.isInitialized = false;
      this._transitions = [];
      this.isTransitioning = false;
      this._queue = [];

      const el = this._getElementOption(element);

      if (!el) {
        throw new TypeError('Shuffle needs to be initialized with an element.');
      }

      this.element = el;
      this.id = `shuffle_${id}`;
      id += 1;

      this._init();

      this.isInitialized = true;
    }

    _init() {
      this.items = this._getItems();
      this.sortedItems = this.items;
      this.options.sizer = this._getElementOption(this.options.sizer); // Add class and invalidate styles

      this.element.classList.add(Shuffle.Classes.BASE); // Set initial css for each item

      this._initItems(this.items); // If the page has not already emitted the `load` event, call layout on load.
      // This avoids layout issues caused by images and fonts loading after the
      // instance has been initialized.


      if (document.readyState !== 'complete') {
        const layout = this.layout.bind(this);
        window.addEventListener('load', function onLoad() {
          window.removeEventListener('load', onLoad);
          layout();
        });
      } // Get container css all in one request. Causes reflow


      const containerCss = window.getComputedStyle(this.element, null);
      const containerWidth = Shuffle.getSize(this.element).width; // Add styles to the container if it doesn't have them.

      this._validateStyles(containerCss); // We already got the container's width above, no need to cause another
      // reflow getting it again... Calculate the number of columns there will be


      this._setColumns(containerWidth); // Kick off!


      this.filter(this.options.group, this.options.initialSort); // Bind resize events

      this._rafId = null; // This is true for all supported browsers, but just to be safe, avoid throwing
      // an error if ResizeObserver is not present. You can manually add a window resize
      // event and call `update()` if ResizeObserver is missing, or use Shuffle v5.

      if ('ResizeObserver' in window) {
        this._resizeObserver = new ResizeObserver(this._handleResizeCallback.bind(this));

        this._resizeObserver.observe(this.element);
      } // The shuffle items haven't had transitions set on them yet so the user
      // doesn't see the first layout. Set them now that the first layout is done.
      // First, however, a synchronous layout must be caused for the previous
      // styles to be applied without transitions.


      this.element.offsetWidth; // eslint-disable-line no-unused-expressions

      this.setItemTransitions(this.items);
      this.element.style.transition = `height ${this.options.speed}ms ${this.options.easing}`;
    }
    /**
     * Retrieve an element from an option.
     * @param {string|jQuery|Element} option The option to check.
     * @return {?Element} The plain element or null.
     * @private
     */


    _getElementOption(option) {
      // If column width is a string, treat is as a selector and search for the
      // sizer element within the outermost container
      if (typeof option === 'string') {
        return this.element.querySelector(option);
      } // Check for an element


      if (option && option.nodeType && option.nodeType === 1) {
        return option;
      } // Check for jQuery object


      if (option && option.jquery) {
        return option[0];
      }

      return null;
    }
    /**
     * Ensures the shuffle container has the css styles it needs applied to it.
     * @param {Object} styles Key value pairs for position and overflow.
     * @private
     */


    _validateStyles(styles) {
      // Position cannot be static.
      if (styles.position === 'static') {
        this.element.style.position = 'relative';
      } // Overflow has to be hidden.


      if (styles.overflow !== 'hidden') {
        this.element.style.overflow = 'hidden';
      }
    }
    /**
     * Filter the elements by a category.
     * @param {string|string[]|function(Element):boolean} [category] Category to
     *     filter by. If it's given, the last category will be used to filter the items.
     * @param {Array} [collection] Optionally filter a collection. Defaults to
     *     all the items.
     * @return {{visible: ShuffleItem[], hidden: ShuffleItem[]}}
     * @private
     */


    _filter() {
      let category = arguments.length > 0 && arguments[0] !== undefined ? arguments[0] : this.lastFilter;
      let collection = arguments.length > 1 && arguments[1] !== undefined ? arguments[1] : this.items;

      const set = this._getFilteredSets(category, collection); // Individually add/remove hidden/visible classes


      this._toggleFilterClasses(set); // Save the last filter in case elements are appended.


      this.lastFilter = category; // This is saved mainly because providing a filter function (like searching)
      // will overwrite the `lastFilter` property every time its called.

      if (typeof category === 'string') {
        this.group = category;
      }

      return set;
    }
    /**
     * Returns an object containing the visible and hidden elements.
     * @param {string|string[]|function(Element):boolean} category Category or function to filter by.
     * @param {ShuffleItem[]} items A collection of items to filter.
     * @return {{visible: ShuffleItem[], hidden: ShuffleItem[]}}
     * @private
     */


    _getFilteredSets(category, items) {
      let visible = [];
      const hidden = []; // category === 'all', add visible class to everything

      if (category === Shuffle.ALL_ITEMS) {
        visible = items; // Loop through each item and use provided function to determine
        // whether to hide it or not.
      } else {
        items.forEach(item => {
          if (this._doesPassFilter(category, item.element)) {
            visible.push(item);
          } else {
            hidden.push(item);
          }
        });
      }

      return {
        visible,
        hidden
      };
    }
    /**
     * Test an item to see if it passes a category.
     * @param {string|string[]|function():boolean} category Category or function to filter by.
     * @param {Element} element An element to test.
     * @return {boolean} Whether it passes the category/filter.
     * @private
     */


    _doesPassFilter(category, element) {
      if (typeof category === 'function') {
        return category.call(element, element, this);
      } // Check each element's data-groups attribute against the given category.


      const attr = element.dataset[Shuffle.FILTER_ATTRIBUTE_KEY];
      const keys = this.options.delimiter ? attr.split(this.options.delimiter) : JSON.parse(attr);

      function testCategory(category) {
        return keys.includes(category);
      }

      if (Array.isArray(category)) {
        if (this.options.filterMode === Shuffle.FilterMode.ANY) {
          return category.some(testCategory);
        }

        return category.every(testCategory);
      }

      return keys.includes(category);
    }
    /**
     * Toggles the visible and hidden class names.
     * @param {{visible, hidden}} Object with visible and hidden arrays.
     * @private
     */


    _toggleFilterClasses(_ref) {
      let {
        visible,
        hidden
      } = _ref;
      visible.forEach(item => {
        item.show();
      });
      hidden.forEach(item => {
        item.hide();
      });
    }
    /**
     * Set the initial css for each item
     * @param {ShuffleItem[]} items Set to initialize.
     * @private
     */


    _initItems(items) {
      items.forEach(item => {
        item.init();
      });
    }
    /**
     * Remove element reference and styles.
     * @param {ShuffleItem[]} items Set to dispose.
     * @private
     */


    _disposeItems(items) {
      items.forEach(item => {
        item.dispose();
      });
    }
    /**
     * Updates the visible item count.
     * @private
     */


    _updateItemCount() {
      this.visibleItems = this._getFilteredItems().length;
    }
    /**
     * Sets css transform transition on a group of elements. This is not executed
     * at the same time as `item.init` so that transitions don't occur upon
     * initialization of a new Shuffle instance.
     * @param {ShuffleItem[]} items Shuffle items to set transitions on.
     * @protected
     */


    setItemTransitions(items) {
      const {
        speed,
        easing
      } = this.options;
      const positionProps = this.options.useTransforms ? ['transform'] : ['top', 'left']; // Allow users to transtion other properties if they exist in the `before`
      // css mapping of the shuffle item.

      const cssProps = Object.keys(ShuffleItem.Css.HIDDEN.before).map(k => hyphenate(k));
      const properties = positionProps.concat(cssProps).join();
      items.forEach(item => {
        item.element.style.transitionDuration = `${speed}ms`;
        item.element.style.transitionTimingFunction = easing;
        item.element.style.transitionProperty = properties;
      });
    }

    _getItems() {
      return Array.from(this.element.children).filter(el => el.matches(this.options.itemSelector)).map(el => new ShuffleItem(el, this.options.isRTL));
    }
    /**
     * Combine the current items array with a new one and sort it by DOM order.
     * @param {ShuffleItem[]} items Items to track.
     * @return {ShuffleItem[]}
     */


    _mergeNewItems(items) {
      const children = Array.from(this.element.children);
      return sorter(this.items.concat(items), {
        by(element) {
          return children.indexOf(element);
        }

      });
    }

    _getFilteredItems() {
      return this.items.filter(item => item.isVisible);
    }

    _getConcealedItems() {
      return this.items.filter(item => !item.isVisible);
    }
    /**
     * Returns the column size, based on column width and sizer options.
     * @param {number} containerWidth Size of the parent container.
     * @param {number} gutterSize Size of the gutters.
     * @return {number}
     * @private
     */


    _getColumnSize(containerWidth, gutterSize) {
      let size; // If the columnWidth property is a function, then the grid is fluid

      if (typeof this.options.columnWidth === 'function') {
        size = this.options.columnWidth(containerWidth); // columnWidth option isn't a function, are they using a sizing element?
      } else if (this.options.sizer) {
        size = Shuffle.getSize(this.options.sizer).width; // if not, how about the explicitly set option?
      } else if (this.options.columnWidth) {
        size = this.options.columnWidth; // or use the size of the first item
      } else if (this.items.length > 0) {
        size = Shuffle.getSize(this.items[0].element, true).width; // if there's no items, use size of container
      } else {
        size = containerWidth;
      } // Don't let them set a column width of zero.


      if (size === 0) {
        size = containerWidth;
      }

      return size + gutterSize;
    }
    /**
     * Returns the gutter size, based on gutter width and sizer options.
     * @param {number} containerWidth Size of the parent container.
     * @return {number}
     * @private
     */


    _getGutterSize(containerWidth) {
      let size;

      if (typeof this.options.gutterWidth === 'function') {
        size = this.options.gutterWidth(containerWidth);
      } else if (this.options.sizer) {
        size = getNumberStyle(this.options.sizer, 'marginLeft');
      } else {
        size = this.options.gutterWidth;
      }

      return size;
    }
    /**
     * Calculate the number of columns to be used. Gets css if using sizer element.
     * @param {number} [containerWidth] Optionally specify a container width if
     *    it's already available.
     */


    _setColumns() {
      let containerWidth = arguments.length > 0 && arguments[0] !== undefined ? arguments[0] : Shuffle.getSize(this.element).width;

      const gutter = this._getGutterSize(containerWidth);

      const columnWidth = this._getColumnSize(containerWidth, gutter);

      let calculatedColumns = (containerWidth + gutter) / columnWidth; // Widths given from getStyles are not precise enough...

      if (Math.abs(Math.round(calculatedColumns) - calculatedColumns) < this.options.columnThreshold) {
        // e.g. calculatedColumns = 11.998876
        calculatedColumns = Math.round(calculatedColumns);
      }

      this.cols = Math.max(Math.floor(calculatedColumns || 0), 1);
      this.containerWidth = containerWidth;
      this.colWidth = columnWidth;
    }
    /**
     * Adjust the height of the grid
     */


    _setContainerSize() {
      this.element.style.height = `${this._getContainerSize()}px`;
    }
    /**
     * Based on the column heights, it returns the biggest one.
     * @return {number}
     * @private
     */


    _getContainerSize() {
      return arrayMax(this.positions);
    }
    /**
     * Get the clamped stagger amount.
     * @param {number} index Index of the item to be staggered.
     * @return {number}
     */


    _getStaggerAmount(index) {
      return Math.min(index * this.options.staggerAmount, this.options.staggerAmountMax);
    }
    /**
     * Emit an event from this instance.
     * @param {string} name Event name.
     * @param {Object} [data={}] Optional object data.
     */


    _dispatch(name) {
      let data = arguments.length > 1 && arguments[1] !== undefined ? arguments[1] : {};

      if (this.isDestroyed) {
        return;
      }

      data.shuffle = this;
      this.emit(name, data);
    }
    /**
     * Zeros out the y columns array, which is used to determine item placement.
     * @private
     */


    _resetCols() {
      let i = this.cols;
      this.positions = [];

      while (i) {
        i -= 1;
        this.positions.push(0);
      }
    }
    /**
     * Loops through each item that should be shown and calculates the x, y position.
     * @param {ShuffleItem[]} items Array of items that will be shown/layed
     *     out in order in their array.
     */


    _layout(items) {
      const itemPositions = this._getNextPositions(items);

      let count = 0;
      items.forEach((item, i) => {
        function callback() {
          item.applyCss(ShuffleItem.Css.VISIBLE.after);
        } // If the item will not change its position, do not add it to the render
        // queue. Transitions don't fire when setting a property to the same value.


        if (Point.equals(item.point, itemPositions[i]) && !item.isHidden) {
          item.applyCss(ShuffleItem.Css.VISIBLE.before);
          callback();
          return;
        }

        item.point = itemPositions[i];
        item.scale = ShuffleItem.Scale.VISIBLE;
        item.isHidden = false; // Clone the object so that the `before` object isn't modified when the
        // transition delay is added.

        const styles = this.getStylesForTransition(item, ShuffleItem.Css.VISIBLE.before);
        styles.transitionDelay = `${this._getStaggerAmount(count)}ms`;

        this._queue.push({
          item,
          styles,
          callback
        });

        count += 1;
      });
    }
    /**
     * Return an array of Point instances representing the future positions of
     * each item.
     * @param {ShuffleItem[]} items Array of sorted shuffle items.
     * @return {Point[]}
     * @private
     */


    _getNextPositions(items) {
      // If position data is going to be changed, add the item's size to the
      // transformer to allow for calculations.
      if (this.options.isCentered) {
        const itemsData = items.map((item, i) => {
          const itemSize = Shuffle.getSize(item.element, true);

          const point = this._getItemPosition(itemSize);

          return new Rect(point.x, point.y, itemSize.width, itemSize.height, i);
        });
        return this.getTransformedPositions(itemsData, this.containerWidth);
      } // If no transforms are going to happen, simply return an array of the
      // future points of each item.


      return items.map(item => this._getItemPosition(Shuffle.getSize(item.element, true)));
    }
    /**
     * Determine the location of the next item, based on its size.
     * @param {{width: number, height: number}} itemSize Object with width and height.
     * @return {Point}
     * @private
     */


    _getItemPosition(itemSize) {
      return getItemPosition({
        itemSize,
        positions: this.positions,
        gridSize: this.colWidth,
        total: this.cols,
        threshold: this.options.columnThreshold,
        buffer: this.options.buffer
      });
    }
    /**
     * Mutate positions before they're applied.
     * @param {Rect[]} itemRects Item data objects.
     * @param {number} containerWidth Width of the containing element.
     * @return {Point[]}
     * @protected
     */


    getTransformedPositions(itemRects, containerWidth) {
      return getCenteredPositions(itemRects, containerWidth);
    }
    /**
     * Hides the elements that don't match our filter.
     * @param {ShuffleItem[]} collection Collection to shrink.
     * @private
     */


    _shrink() {
      let collection = arguments.length > 0 && arguments[0] !== undefined ? arguments[0] : this._getConcealedItems();
      let count = 0;
      collection.forEach(item => {
        function callback() {
          item.applyCss(ShuffleItem.Css.HIDDEN.after);
        } // Continuing would add a transitionend event listener to the element, but
        // that listener would not execute because the transform and opacity would
        // stay the same.
        // The callback is executed here because it is not guaranteed to be called
        // after the transitionend event because the transitionend could be
        // canceled if another animation starts.


        if (item.isHidden) {
          item.applyCss(ShuffleItem.Css.HIDDEN.before);
          callback();
          return;
        }

        item.scale = ShuffleItem.Scale.HIDDEN;
        item.isHidden = true;
        const styles = this.getStylesForTransition(item, ShuffleItem.Css.HIDDEN.before);
        styles.transitionDelay = `${this._getStaggerAmount(count)}ms`;

        this._queue.push({
          item,
          styles,
          callback
        });

        count += 1;
      });
    }
    /**
     * Resize handler.
     * @param {ResizeObserverEntry[]} entries
     */


    _handleResizeCallback(entries) {
      // If shuffle is disabled, destroyed, don't do anything.
      // You can still manually force a shuffle update with shuffle.update({ force: true }).
      if (!this.isEnabled || this.isDestroyed) {
        return;
      } // The reason ESLint disables this is because for..of generates a lot of extra
      // code using Babel, but Shuffle no longer supports browsers that old, so
      // nothing to worry about.
      // eslint-disable-next-line no-restricted-syntax


      for (const entry of entries) {
        if (Math.round(entry.contentRect.width) !== Math.round(this.containerWidth)) {
          // If there was already an animation waiting, cancel it.
          cancelAnimationFrame(this._rafId); // Offload updating the DOM until the browser is ready.

          this._rafId = requestAnimationFrame(this.update.bind(this));
        }
      }
    }
    /**
     * Returns styles which will be applied to the an item for a transition.
     * @param {ShuffleItem} item Item to get styles for. Should have updated
     *   scale and point properties.
     * @param {Object} styleObject Extra styles that will be used in the transition.
     * @return {!Object} Transforms for transitions, left/top for animate.
     * @protected
     */


    getStylesForTransition(item, styleObject) {
      // Clone the object to avoid mutating the original.
      const styles = { ...styleObject
      };

      if (this.options.useTransforms) {
        const sign = this.options.isRTL ? '-' : '';
        const x = this.options.roundTransforms ? Math.round(item.point.x) : item.point.x;
        const y = this.options.roundTransforms ? Math.round(item.point.y) : item.point.y;
        styles.transform = `translate(${sign}${x}px, ${y}px) scale(${item.scale})`;
      } else {
        if (this.options.isRTL) {
          styles.right = `${item.point.x}px`;
        } else {
          styles.left = `${item.point.x}px`;
        }

        styles.top = `${item.point.y}px`;
      }

      return styles;
    }
    /**
     * Listen for the transition end on an element and execute the itemCallback
     * when it finishes.
     * @param {Element} element Element to listen on.
     * @param {function} itemCallback Callback for the item.
     * @param {function} done Callback to notify `parallel` that this one is done.
     */


    _whenTransitionDone(element, itemCallback, done) {
      const id = onTransitionEnd(element, evt => {
        itemCallback();
        done(null, evt);
      });

      this._transitions.push(id);
    }
    /**
     * Return a function which will set CSS styles and call the `done` function
     * when (if) the transition finishes.
     * @param {Object} opts Transition object.
     * @return {function} A function to be called with a `done` function.
     */


    _getTransitionFunction(opts) {
      return done => {
        opts.item.applyCss(opts.styles);

        this._whenTransitionDone(opts.item.element, opts.callback, done);
      };
    }
    /**
     * Execute the styles gathered in the style queue. This applies styles to elements,
     * triggering transitions.
     * @private
     */


    _processQueue() {
      if (this.isTransitioning) {
        this._cancelMovement();
      }

      const hasSpeed = this.options.speed > 0;
      const hasQueue = this._queue.length > 0;

      if (hasQueue && hasSpeed && this.isInitialized) {
        this._startTransitions(this._queue);
      } else if (hasQueue) {
        this._styleImmediately(this._queue);

        this._dispatch(Shuffle.EventType.LAYOUT); // A call to layout happened, but none of the newly visible items will
        // change position or the transition duration is zero, which will not trigger
        // the transitionend event.

      } else {
        this._dispatch(Shuffle.EventType.LAYOUT);
      } // Remove everything in the style queue


      this._queue.length = 0;
    }
    /**
     * Wait for each transition to finish, the emit the layout event.
     * @param {Object[]} transitions Array of transition objects.
     */


    _startTransitions(transitions) {
      // Set flag that shuffle is currently in motion.
      this.isTransitioning = true; // Create an array of functions to be called.

      const callbacks = transitions.map(obj => this._getTransitionFunction(obj));
      arrayParallel(callbacks, this._movementFinished.bind(this));
    }

    _cancelMovement() {
      // Remove the transition end event for each listener.
      this._transitions.forEach(cancelTransitionEnd); // Reset the array.


      this._transitions.length = 0; // Show it's no longer active.

      this.isTransitioning = false;
    }
    /**
     * Apply styles without a transition.
     * @param {Object[]} objects Array of transition objects.
     * @private
     */


    _styleImmediately(objects) {
      if (objects.length) {
        const elements = objects.map(obj => obj.item.element);

        Shuffle._skipTransitions(elements, () => {
          objects.forEach(obj => {
            obj.item.applyCss(obj.styles);
            obj.callback();
          });
        });
      }
    }

    _movementFinished() {
      this._transitions.length = 0;
      this.isTransitioning = false;

      this._dispatch(Shuffle.EventType.LAYOUT);
    }
    /**
     * The magic. This is what makes the plugin 'shuffle'
     * @param {string|string[]|function(Element):boolean} [category] Category to filter by.
     *     Can be a function, string, or array of strings.
     * @param {SortOptions} [sortOptions] A sort object which can sort the visible set
     */


    filter(category, sortOptions) {
      if (!this.isEnabled) {
        return;
      }

      if (!category || category && category.length === 0) {
        category = Shuffle.ALL_ITEMS; // eslint-disable-line no-param-reassign
      }

      this._filter(category); // Shrink each hidden item


      this._shrink(); // How many visible elements?


      this._updateItemCount(); // Update transforms on visible elements so they will animate to their new positions.


      this.sort(sortOptions);
    }
    /**
     * Gets the visible elements, sorts them, and passes them to layout.
     * @param {SortOptions} [sortOptions] The options object to pass to `sorter`.
     */


    sort() {
      let sortOptions = arguments.length > 0 && arguments[0] !== undefined ? arguments[0] : this.lastSort;

      if (!this.isEnabled) {
        return;
      }

      this._resetCols();

      const items = sorter(this._getFilteredItems(), sortOptions);
      this.sortedItems = items;

      this._layout(items); // `_layout` always happens after `_shrink`, so it's safe to process the style
      // queue here with styles from the shrink method.


      this._processQueue(); // Adjust the height of the container.


      this._setContainerSize();

      this.lastSort = sortOptions;
    }
    /**
     * Reposition everything.
     * @param {object} options options object
     * @param {boolean} [options.recalculateSizes=true] Whether to calculate column, gutter, and container widths again.
     * @param {boolean} [options.force=false] By default, `update` does nothing if the instance is disabled. Setting this
     *    to true forces the update to happen regardless.
     */


    update() {
      let {
        recalculateSizes = true,
        force = false
      } = arguments.length > 0 && arguments[0] !== undefined ? arguments[0] : {};

      if (this.isEnabled || force) {
        if (recalculateSizes) {
          this._setColumns();
        } // Layout items


        this.sort();
      }
    }
    /**
     * Use this instead of `update()` if you don't need the columns and gutters updated
     * Maybe an image inside `shuffle` loaded (and now has a height), which means calculations
     * could be off.
     */


    layout() {
      this.update({
        recalculateSizes: true
      });
    }
    /**
     * New items have been appended to shuffle. Mix them in with the current
     * filter or sort status.
     * @param {Element[]} newItems Collection of new items.
     */


    add(newItems) {
      const items = arrayUnique(newItems).map(el => new ShuffleItem(el, this.options.isRTL)); // Add classes and set initial positions.

      this._initItems(items); // Determine which items will go with the current filter.


      this._resetCols();

      const allItems = this._mergeNewItems(items);

      const sortedItems = sorter(allItems, this.lastSort);

      const allSortedItemsSet = this._filter(this.lastFilter, sortedItems);

      const isNewItem = item => items.includes(item);

      const applyHiddenState = item => {
        item.scale = ShuffleItem.Scale.HIDDEN;
        item.isHidden = true;
        item.applyCss(ShuffleItem.Css.HIDDEN.before);
        item.applyCss(ShuffleItem.Css.HIDDEN.after);
      }; // Layout all items again so that new items get positions.
      // Synchonously apply positions.


      const itemPositions = this._getNextPositions(allSortedItemsSet.visible);

      allSortedItemsSet.visible.forEach((item, i) => {
        if (isNewItem(item)) {
          item.point = itemPositions[i];
          applyHiddenState(item);
          item.applyCss(this.getStylesForTransition(item, {}));
        }
      });
      allSortedItemsSet.hidden.forEach(item => {
        if (isNewItem(item)) {
          applyHiddenState(item);
        }
      }); // Cause layout so that the styles above are applied.

      this.element.offsetWidth; // eslint-disable-line no-unused-expressions
      // Add transition to each item.

      this.setItemTransitions(items); // Update the list of items.

      this.items = this._mergeNewItems(items); // Update layout/visibility of new and old items.

      this.filter(this.lastFilter);
    }
    /**
     * Disables shuffle from updating dimensions and layout on resize
     */


    disable() {
      this.isEnabled = false;
    }
    /**
     * Enables shuffle again
     * @param {boolean} [isUpdateLayout=true] if undefined, shuffle will update columns and gutters
     */


    enable() {
      let isUpdateLayout = arguments.length > 0 && arguments[0] !== undefined ? arguments[0] : true;
      this.isEnabled = true;

      if (isUpdateLayout) {
        this.update();
      }
    }
    /**
     * Remove 1 or more shuffle items.
     * @param {Element[]} elements An array containing one or more
     *     elements in shuffle
     * @return {Shuffle} The shuffle instance.
     */


    remove(elements) {
      if (!elements.length) {
        return;
      }

      const collection = arrayUnique(elements);
      const oldItems = collection.map(element => this.getItemByElement(element)).filter(item => !!item);

      const handleLayout = () => {
        this._disposeItems(oldItems); // Remove the collection in the callback


        collection.forEach(element => {
          element.parentNode.removeChild(element);
        });

        this._dispatch(Shuffle.EventType.REMOVED, {
          collection
        });
      }; // Hide collection first.


      this._toggleFilterClasses({
        visible: [],
        hidden: oldItems
      });

      this._shrink(oldItems);

      this.sort(); // Update the list of items here because `remove` could be called again
      // with an item that is in the process of being removed.

      this.items = this.items.filter(item => !oldItems.includes(item));

      this._updateItemCount();

      this.once(Shuffle.EventType.LAYOUT, handleLayout);
    }
    /**
     * Retrieve a shuffle item by its element.
     * @param {Element} element Element to look for.
     * @return {?ShuffleItem} A shuffle item or undefined if it's not found.
     */


    getItemByElement(element) {
      return this.items.find(item => item.element === element);
    }
    /**
     * Dump the elements currently stored and reinitialize all child elements which
     * match the `itemSelector`.
     */


    resetItems() {
      // Remove refs to current items.
      this._disposeItems(this.items);

      this.isInitialized = false; // Find new items in the DOM.

      this.items = this._getItems(); // Set initial styles on the new items.

      this._initItems(this.items);

      this.once(Shuffle.EventType.LAYOUT, () => {
        // Add transition to each item.
        this.setItemTransitions(this.items);
        this.isInitialized = true;
      }); // Lay out all items.

      this.filter(this.lastFilter);
    }
    /**
     * Destroys shuffle, removes events, styles, and classes
     */


    destroy() {
      this._cancelMovement();

      if (this._resizeObserver) {
        this._resizeObserver.unobserve(this.element);

        this._resizeObserver = null;
      } // Reset container styles


      this.element.classList.remove('shuffle');
      this.element.removeAttribute('style'); // Reset individual item styles

      this._disposeItems(this.items);

      this.items.length = 0;
      this.sortedItems.length = 0;
      this._transitions.length = 0; // Null DOM references

      this.options.sizer = null;
      this.element = null; // Set a flag so if a debounced resize has been triggered,
      // it can first check if it is actually isDestroyed and not doing anything

      this.isDestroyed = true;
      this.isEnabled = false;
    }
    /**
     * Returns the outer width of an element, optionally including its margins.
     *
     * There are a few different methods for getting the width of an element, none of
     * which work perfectly for all Shuffle's use cases.
     *
     * 1. getBoundingClientRect() `left` and `right` properties.
     *   - Accounts for transform scaled elements, making it useless for Shuffle
     *   elements which have shrunk.
     * 2. The `offsetWidth` property.
     *   - This value stays the same regardless of the elements transform property,
     *   however, it does not return subpixel values.
     * 3. getComputedStyle()
     *   - This works great Chrome, Firefox, Safari, but IE<=11 does not include
     *   padding and border when box-sizing: border-box is set, requiring a feature
     *   test and extra work to add the padding back for IE and other browsers which
     *   follow the W3C spec here.
     *
     * @param {Element} element The element.
     * @param {boolean} [includeMargins=false] Whether to include margins.
     * @return {{width: number, height: number}} The width and height.
     */


    static getSize(element) {
      let includeMargins = arguments.length > 1 && arguments[1] !== undefined ? arguments[1] : false;
      // Store the styles so that they can be used by others without asking for it again.
      const styles = window.getComputedStyle(element, null);
      let width = getNumberStyle(element, 'width', styles);
      let height = getNumberStyle(element, 'height', styles);

      if (includeMargins) {
        const marginLeft = getNumberStyle(element, 'marginLeft', styles);
        const marginRight = getNumberStyle(element, 'marginRight', styles);
        const marginTop = getNumberStyle(element, 'marginTop', styles);
        const marginBottom = getNumberStyle(element, 'marginBottom', styles);
        width += marginLeft + marginRight;
        height += marginTop + marginBottom;
      }

      return {
        width,
        height
      };
    }
    /**
     * Change a property or execute a function which will not have a transition
     * @param {Element[]} elements DOM elements that won't be transitioned.
     * @param {function} callback A function which will be called while transition
     *     is set to 0ms.
     * @private
     */


    static _skipTransitions(elements, callback) {
      const zero = '0ms'; // Save current duration and delay.

      const data = elements.map(element => {
        const {
          style
        } = element;
        const duration = style.transitionDuration;
        const delay = style.transitionDelay; // Set the duration to zero so it happens immediately

        style.transitionDuration = zero;
        style.transitionDelay = zero;
        return {
          duration,
          delay
        };
      });
      callback(); // Cause forced synchronous layout.

      elements[0].offsetWidth; // eslint-disable-line no-unused-expressions
      // Put the duration back

      elements.forEach((element, i) => {
        element.style.transitionDuration = data[i].duration;
        element.style.transitionDelay = data[i].delay;
      });
    }

  }

  Shuffle.ShuffleItem = ShuffleItem;
  Shuffle.ALL_ITEMS = 'all';
  Shuffle.FILTER_ATTRIBUTE_KEY = 'groups';
  /** @enum {string} */

  Shuffle.EventType = {
    LAYOUT: 'shuffle:layout',
    REMOVED: 'shuffle:removed'
  };
  /** @enum {string} */

  Shuffle.Classes = Classes;
  /** @enum {string} */

  Shuffle.FilterMode = {
    ANY: 'any',
    ALL: 'all'
  }; // Overrideable options

  Shuffle.options = {
    // Initial filter group.
    group: Shuffle.ALL_ITEMS,
    // Transition/animation speed (milliseconds).
    speed: 250,
    // CSS easing function to use.
    easing: 'cubic-bezier(0.4, 0.0, 0.2, 1)',
    // e.g. '.picture-item'.
    itemSelector: '*',
    // Element or selector string. Use an element to determine the size of columns
    // and gutters.
    sizer: null,
    // A static number or function that tells the plugin how wide the gutters
    // between columns are (in pixels).
    gutterWidth: 0,
    // A static number or function that returns a number which tells the plugin
    // how wide the columns are (in pixels).
    columnWidth: 0,
    // If your group is not json, and is comma delimited, you could set delimiter
    // to ','.
    delimiter: null,
    // Useful for percentage based heights when they might not always be exactly
    // the same (in pixels).
    buffer: 0,
    // Reading the width of elements isn't precise enough and can cause columns to
    // jump between values.
    columnThreshold: 0.01,
    // Shuffle can be initialized with a sort object. It is the same object
    // given to the sort method.
    initialSort: null,
    // Transition delay offset for each item in milliseconds.
    staggerAmount: 15,
    // Maximum stagger delay in milliseconds.
    staggerAmountMax: 150,
    // Whether to use transforms or absolute positioning.
    useTransforms: true,
    // Affects using an array with filter. e.g. `filter(['one', 'two'])`. With "any",
    // the element passes the test if any of its groups are in the array. With "all",
    // the element only passes if all groups are in the array.
    // Note, this has no effect if you supply a custom filter function.
    filterMode: Shuffle.FilterMode.ANY,
    // Attempt to center grid items in each row.
    isCentered: false,
    // Attempt to align grid items to right.
    isRTL: false,
    // Whether to round pixel values used in translate(x, y). This usually avoids
    // blurriness.
    roundTransforms: true
  };
  Shuffle.Point = Point;
  Shuffle.Rect = Rect; // Expose for testing. Hack at your own risk.

  Shuffle.__sorter = sorter;
  Shuffle.__getColumnSpan = getColumnSpan;
  Shuffle.__getAvailablePositions = getAvailablePositions;
  Shuffle.__getShortColumn = getShortColumn;
  Shuffle.__getCenteredPositions = getCenteredPositions;

  return Shuffle;

}));
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