function addText(text) {
      if (!text) {
        return;
      }
      html.push(sanitizeText(text));
    }
@ngdoc filter
@name linky
@kind function

@description
Finds links in text input and turns them into html links. Supports `http/https/ftp/sftp/mailto` and
plain email address links.

Requires the {@link ngSanitize `ngSanitize`} module to be installed.

@param {string} text Input text.
@param {string} [target] Window (`_blank|_self|_parent|_top`) or named frame to open links in.
@param {object|function(url)} [attributes] Add custom attributes to the link element.

   Can be one of:

   - `object`: A map of attributes
   - `function`: Takes the url as a parameter and returns a map of attributes

   If the map of attributes contains a value for `target`, it overrides the value of
   the target parameter.


@returns {string} Html-linkified and {@link $sanitize sanitized} text.

@usage
   <span ng-bind-html="linky_expression | linky"></span>

@example
   <example module="linkyExample" deps="angular-sanitize.js" name="linky-filter">
     <file name="index.html">
       <div ng-controller="ExampleController">
       Snippet: <textarea ng-model="snippet" cols="60" rows="3"></textarea>
       <table>
         <tr>
           <th>Filter</th>
           <th>Source</th>
           <th>Rendered</th>
         </tr>
         <tr id="linky-filter">
           <td>linky filter</td>
           <td>
             <pre>&lt;div ng-bind-html="snippet | linky"&gt;<br>&lt;/div&gt;</pre>
           </td>
           <td>
             <div ng-bind-html="snippet | linky"></div>
           </td>
         </tr>
         <tr id="linky-target">
          <td>linky target</td>
          <td>
            <pre>&lt;div ng-bind-html="snippetWithSingleURL | linky:'_blank'"&gt;<br>&lt;/div&gt;</pre>
          </td>
          <td>
            <div ng-bind-html="snippetWithSingleURL | linky:'_blank'"></div>
          </td>
         </tr>
         <tr id="linky-custom-attributes">
          <td>linky custom attributes</td>
          <td>
            <pre>&lt;div ng-bind-html="snippetWithSingleURL | linky:'_self':{rel: 'nofollow'}"&gt;<br>&lt;/div&gt;</pre>
          </td>
          <td>
            <div ng-bind-html="snippetWithSingleURL | linky:'_self':{rel: 'nofollow'}"></div>
          </td>
         </tr>
         <tr id="escaped-html">
           <td>no filter</td>
           <td><pre>&lt;div ng-bind="snippet"&gt;<br>&lt;/div&gt;</pre></td>
           <td><div ng-bind="snippet"></div></td>
         </tr>
       </table>
     </file>
     <file name="script.js">
       angular.module('linkyExample', ['ngSanitize'])
         .controller('ExampleController', ['$scope', function($scope) {
           $scope.snippet =
             'Pretty text with some links:\n' +
             'http://angularjs.org/,\n' +
             'mailto:us@somewhere.org,\n' +
             'another@somewhere.org,\n' +
             'and one more: ftp://127.0.0.1/.';
           $scope.snippetWithSingleURL = 'http://angularjs.org/';
         }]);
     </file>
     <file name="protractor.js" type="protractor">
       it('should linkify the snippet with urls', function() {
         expect(element(by.id('linky-filter')).element(by.binding('snippet | linky')).getText()).
             toBe('Pretty text with some links: http://angularjs.org/, us@somewhere.org, ' +
                  'another@somewhere.org, and one more: ftp://127.0.0.1/.');
         expect(element.all(by.css('#linky-filter a')).count()).toEqual(4);
       });

       it('should not linkify snippet without the linky filter', function() {
         expect(element(by.id('escaped-html')).element(by.binding('snippet')).getText()).
             toBe('Pretty text with some links: http://angularjs.org/, mailto:us@somewhere.org, ' +
                  'another@somewhere.org, and one more: ftp://127.0.0.1/.');
         expect(element.all(by.css('#escaped-html a')).count()).toEqual(0);
       });

       it('should update', function() {
         element(by.model('snippet')).clear();
         element(by.model('snippet')).sendKeys('new http://link.');
         expect(element(by.id('linky-filter')).element(by.binding('snippet | linky')).getText()).
             toBe('new http://link.');
         expect(element.all(by.css('#linky-filter a')).count()).toEqual(1);
         expect(element(by.id('escaped-html')).element(by.binding('snippet')).getText())
             .toBe('new http://link.');
       });

       it('should work with the target property', function() {
        expect(element(by.id('linky-target')).
            element(by.binding("snippetWithSingleURL | linky:'_blank'")).getText()).
            toBe('http://angularjs.org/');
        expect(element(by.css('#linky-target a')).getAttribute('target')).toEqual('_blank');
       });

       it('should optionally add custom attributes', function() {
        expect(element(by.id('linky-custom-attributes')).
            element(by.binding("snippetWithSingleURL | linky:'_self':{rel: 'nofollow'}")).getText()).
            toBe('http://angularjs.org/');
        expect(element(by.css('#linky-custom-attributes a')).getAttribute('rel')).toEqual('nofollow');
       });
     </file>
   </example>