Using an Angular factory to run data through logic across controllers

My service:

myApp.factory("MediaService", ['$http', 
function($http) {

    return {
        all: function() {
            return $http.get('/media');
        },
        save: function( data ) {
            return $http.post('/media', data);
        }
    }
}
]);

My controller:

myApp.controller("MediaController", ['$http', '$scope', '$routeParams', 'Upload', 'MediaService', 'messageService',  
function( $http, $scope, $routeParams, Upload, MediaService, messageService) {
    var media = this;

    MediaService.all().success( function (data) {
        media.versioning = []
        media.files = []
        for(i = 0, len = data[0].file.length; i< len; i++)
            if(!media.versioning[data[0].file[i].key[0]] || media.versioning[data[0].file[i].key[0]].version[0] < data[0].file[i].version[0])
                media.versioning[data[0].file[i].key[0]] = data[0].file[i]
        for(var value in media.versioning) 
            media.files.push( media.versioning[value] )
    });

I want to move the code within .success() into the MediaService factory so I can re-use it in another controller.

Obviously I do not want to simply copy and paste this into the other controller, although that would work.

I tried to $q.defer/resolve within the service but it did not work (I believe that practice is deprecated).

What is the best way to move this logic into the service? Ideally I would like to be able to use media.files = MediaService.files().