// add, remove cell
( function( window, factory ) {
  // universal module definition
  /* jshint strict: false */
  if ( typeof define == 'function' && define.amd ) {
    // AMD
    define( [
      './flickity',
      'fizzy-ui-utils/utils'
    ], function( Flickity, utils ) {
      return factory( window, Flickity, utils );
    });
  } else if ( typeof module == 'object' && module.exports ) {
    // CommonJS
    module.exports = factory(
      window,
      require('./flickity'),
      require('fizzy-ui-utils')
    );
  } else {
    // browser global
    factory(
      window,
      window.Flickity,
      window.fizzyUIUtils
    );
  }

}( window, function factory( window, Flickity, utils ) {

'use strict';

// append cells to a document fragment
function getCellsFragment( cells ) {
  var fragment = document.createDocumentFragment();
  cells.forEach( function( cell ) {
    fragment.appendChild( cell.element );
  });
  return fragment;
}

// -------------------------- add/remove cell prototype -------------------------- //

var proto = Flickity.prototype;

/**
 * Insert, prepend, or append cells
 * @param {Element, Array, NodeList} elems
 * @param {Integer} index
 */
proto.insert = function( elems, index ) {
  var cells = this._makeCells( elems );
  if ( !cells || !cells.length ) {
    return;
  }
  var len = this.cells.length;
  // default to append
  index = index === undefined ? len : index;
  // add cells with document fragment
  var fragment = getCellsFragment( cells );
  // append to slider
  var isAppend = index == len;
  if ( isAppend ) {
    this.slider.appendChild( fragment );
  } else {
    var insertCellElement = this.cells[ index ].element;
    this.slider.insertBefore( fragment, insertCellElement );
  }
  // add to this.cells
  if ( index === 0 ) {
    // prepend, add to start
    this.cells = cells.concat( this.cells );
  } else if ( isAppend ) {
    // append, add to end
    this.cells = this.cells.concat( cells );
  } else {
    // insert in this.cells
    var endCells = this.cells.splice( index, len - index );
    this.cells = this.cells.concat( cells ).concat( endCells );
  }

  this._sizeCells( cells );

  var selectedIndexDelta = index > this.selectedIndex ? 0 : cells.length;
  this._cellAddedRemoved( index, selectedIndexDelta );
};

proto.append = function( elems ) {
  this.insert( elems, this.cells.length );
};

proto.prepend = function( elems ) {
  this.insert( elems, 0 );
};

/**
 * Remove cells
 * @param {Element, Array, NodeList} elems
 */
proto.remove = function( elems ) {
  var cells = this.getCells( elems );
  var selectedIndexDelta = 0;
  var len = cells.length;
  var i, cell;
  // calculate selectedIndexDelta, easier if done in seperate loop
  for ( i=0; i < len; i++ ) {
    cell = cells[i];
    var wasBefore = this.cells.indexOf( cell ) < this.selectedIndex;
    selectedIndexDelta -= wasBefore ? 1 : 0;
  }

  for ( i=0; i < len; i++ ) {
    cell = cells[i];
    cell.remove();
    // remove item from collection
    utils.removeFrom( this.cells, cell );
  }

  if ( cells.length ) {
    // update stuff
    this._cellAddedRemoved( 0, selectedIndexDelta );
  }
};

// updates when cells are added or removed
proto._cellAddedRemoved = function( changedCellIndex, selectedIndexDelta ) {
  // TODO this math isn't perfect with grouped slides
  selectedIndexDelta = selectedIndexDelta || 0;
  this.selectedIndex += selectedIndexDelta;
  this.selectedIndex = Math.max( 0, Math.min( this.slides.length - 1, this.selectedIndex ) );

  this.cellChange( changedCellIndex, true );
  // backwards compatibility
  this.emitEvent( 'cellAddedRemoved', [ changedCellIndex, selectedIndexDelta ] );
};

/**
 * logic to be run after a cell's size changes
 * @param {Element} elem - cell's element
 */
proto.cellSizeChange = function( elem ) {
  var cell = this.getCell( elem );
  if ( !cell ) {
    return;
  }
  cell.getSize();

  var index = this.cells.indexOf( cell );
  this.cellChange( index );
};

/**
 * logic any time a cell is changed: added, removed, or size changed
 * @param {Integer} changedCellIndex - index of the changed cell, optional
 */
proto.cellChange = function( changedCellIndex, isPositioningSlider ) {
  var prevSlideableWidth = this.slideableWidth;
  this._positionCells( changedCellIndex );
  this._getWrapShiftCells();
  this.setGallerySize();
  this.emitEvent( 'cellChange', [ changedCellIndex ] );
  // position slider
  if ( this.options.freeScroll ) {
    // shift x by change in slideableWidth
    // TODO fix position shifts when prepending w/ freeScroll
    var deltaX = prevSlideableWidth - this.slideableWidth;
    this.x += deltaX * this.cellAlign;
    this.positionSlider();
  } else {
    // do not position slider after lazy load
    if ( isPositioningSlider ) {
      this.positionSliderAtSelected();
    }
    this.select( this.selectedIndex );
  }
};

// -----  ----- //

return Flickity;

}));