injector.js

app.factory('templateRepository', [ '$injector', function($injector) {
  function lookupUrlFor(contentType) {
    // Do your translation here
  }
  
  return {
    getTemplate: function(contentType) {
      var templateCache = $injector.get('$templateCache');
      return templateCache.get(lookupUrlFor(contentType));
    }
  }
}]);