'use strict';

/**
 * @ngdoc directive
 * @name ngAnimateSwap
 * @restrict A
 * @scope
 *
 * @description
 *
 * ngAnimateSwap is a animation-oriented directive that allows for the container to
 * be removed and entered in whenever the associated expression changes. A
 * common usecase for this directive is a rotating banner or slider component which
 * contains one image being present at a time. When the active image changes
 * then the old image will perform a `leave` animation and the new element
 * will be inserted via an `enter` animation.
 *
 * @animations
 * | Animation                        | Occurs                               |
 * |----------------------------------|--------------------------------------|
 * | {@link ng.$animate#enter enter}  | when the new element is inserted to the DOM  |
 * | {@link ng.$animate#leave leave}  | when the old element is removed from the DOM |
 *
 * @example
 * <example name="ngAnimateSwap-directive" module="ngAnimateSwapExample"
 *          deps="angular-animate.js"
 *          animations="true" fixBase="true">
 *   <file name="index.html">
 *     <div class="container" ng-controller="AppCtrl">
 *       <div ng-animate-swap="number" class="cell swap-animation" ng-class="colorClass(number)">
 *         {{ number }}
 *       </div>
 *     </div>
 *   </file>
 *   <file name="script.js">
 *     angular.module('ngAnimateSwapExample', ['ngAnimate'])
 *       .controller('AppCtrl', ['$scope', '$interval', function($scope, $interval) {
 *         $scope.number = 0;
 *         $interval(function() {
 *           $scope.number++;
 *         }, 1000);
 *
 *         var colors = ['red','blue','green','yellow','orange'];
 *         $scope.colorClass = function(number) {
 *           return colors[number % colors.length];
 *         };
 *       }]);
 *   </file>
 *  <file name="animations.css">
 *  .container {
 *    height:250px;
 *    width:250px;
 *    position:relative;
 *    overflow:hidden;
 *    border:2px solid black;
 *  }
 *  .container .cell {
 *    font-size:150px;
 *    text-align:center;
 *    line-height:250px;
 *    position:absolute;
 *    top:0;
 *    left:0;
 *    right:0;
 *    border-bottom:2px solid black;
 *  }
 *  .swap-animation.ng-enter, .swap-animation.ng-leave {
 *    transition:0.5s linear all;
 *  }
 *  .swap-animation.ng-enter {
 *    top:-250px;
 *  }
 *  .swap-animation.ng-enter-active {
 *    top:0px;
 *  }
 *  .swap-animation.ng-leave {
 *    top:0px;
 *  }
 *  .swap-animation.ng-leave-active {
 *    top:250px;
 *  }
 *  .red { background:red; }
 *  .green { background:green; }
 *  .blue { background:blue; }
 *  .yellow { background:yellow; }
 *  .orange { background:orange; }
 *  </file>
 * </example>
 */
var ngAnimateSwapDirective = ['$animate', function($animate) {
  return {
    restrict: 'A',
    transclude: 'element',
    terminal: true,
    priority: 550, // We use 550 here to ensure that the directive is caught before others,
                   // but after `ngIf` (at priority 600).
    link: function(scope, $element, attrs, ctrl, $transclude) {
      var previousElement, previousScope;
      scope.$watchCollection(attrs.ngAnimateSwap || attrs['for'], function(value) {
        if (previousElement) {
          $animate.leave(previousElement);
        }
        if (previousScope) {
          previousScope.$destroy();
          previousScope = null;
        }
        if (value || value === 0) {
          $transclude(function(clone, childScope) {
            previousElement = clone;
            previousScope = childScope;
            $animate.enter(clone, null, $element);
          });
        }
      });
    }
  };
}];
