'use strict';

/**
 * @ngdoc directive
 * @name angular.module.ng.$compileProvider.directive.ngInclude
 * @restrict ECA
 *
 * @description
 * Fetches, compiles and includes an external HTML fragment.
 *
 * Keep in mind that Same Origin Policy applies to included resources
 * (e.g. ngInclude won't work for cross-domain requests on all browsers and for
 *  file:// access on some browsers).
 *
 * @scope
 *
 * @param {string} ngInclude|src angular expression evaluating to URL. If the source is a string constant,
 *                 make sure you wrap it in quotes, e.g. `src="'myPartialTemplate.html'"`.
 * @param {string=} onload Expression to evaluate when a new partial is loaded.
 *
 * @param {string=} autoscroll Whether `ngInclude` should call {@link angular.module.ng.$anchorScroll
 *                  $anchorScroll} to scroll the viewport after the content is loaded.
 *
 *                  - If the attribute is not set, disable scrolling.
 *                  - If the attribute is set without value, enable scrolling.
 *                  - Otherwise enable scrolling only if the expression evaluates to truthy value.
 *
 * @example
  <example>
    <file name="index.html">
     <div ng-controller="Ctrl">
       <select ng-model="template" ng-options="t.name for t in templates">
        <option value="">(blank)</option>
       </select>
       url of the template: <tt>{{template.url}}</tt>
       <hr/>
       <div ng-include src="template.url"></div>
     </div>
    </file>
    <file name="script.js">
      function Ctrl($scope) {
        $scope.templates =
          [ { name: 'template1.html', url: 'template1.html'}
          , { name: 'template2.html', url: 'template2.html'} ];
        $scope.template = $scope.templates[0];
      }
     </file>
    <file name="template1.html">
      Content of template1.html
    </file>
    <file name="template2.html">
      Content of template2.html
    </file>
    <file name="scenario.js">
      it('should load template1.html', function() {
       expect(element('.doc-example-live [ng-include]').text()).
         toMatch(/Content of template1.html/);
      });
      it('should load template2.html', function() {
       select('template').option('1');
       expect(element('.doc-example-live [ng-include]').text()).
         toMatch(/Content of template2.html/);
      });
      it('should change to blank', function() {
       select('template').option('');
       expect(element('.doc-example-live [ng-include]').text()).toEqual('');
      });
    </file>
  </example>
 */


/**
 * @ngdoc event
 * @name angular.module.ng.$compileProvider.directive.ngInclude#$includeContentLoaded
 * @eventOf angular.module.ng.$compileProvider.directive.ngInclude
 * @eventType emit on the current ngInclude scope
 * @description
 * Emitted every time the ngInclude content is reloaded.
 */
var ngIncludeDirective = ['$http', '$templateCache', '$anchorScroll', '$compile',
                  function($http,   $templateCache,   $anchorScroll,   $compile) {
  return {
    restrict: 'ECA',
    terminal: true,
    compile: function(element, attr) {
      var srcExp = attr.ngInclude || attr.src,
          onloadExp = attr.onload || '',
          autoScrollExp = attr.autoscroll;

      return function(scope, element) {
        var changeCounter = 0,
            childScope;

        var clearContent = function() {
          if (childScope) {
            childScope.$destroy();
            childScope = null;
          }

          element.html('');
        };

        scope.$watch(srcExp, function(src) {
          var thisChangeId = ++changeCounter;

          if (src) {
            $http.get(src, {cache: $templateCache}).success(function(response) {
              if (thisChangeId !== changeCounter) return;

              if (childScope) childScope.$destroy();
              childScope = scope.$new();

              element.html(response);
              $compile(element.contents())(childScope);

              if (isDefined(autoScrollExp) && (!autoScrollExp || scope.$eval(autoScrollExp))) {
                $anchorScroll();
              }

              childScope.$emit('$includeContentLoaded');
              scope.$eval(onloadExp);
            }).error(function() {
              if (thisChangeId === changeCounter) clearContent();
            });
          } else clearContent();
        });
      };
    }
  };
}];
