AngularJS numeric text input: Directive vs. Function

My project has a form with around 16 text fields. The input needs to be numeric, and different fields will have different min/max values. I was able to find the following jsfiddle (http://jsfiddle.net/thomporter/DwKZh/) and adapt the parsing to the following (http://jsfiddle.net/WdBju/):

angular.module('myApp', []).directive('numbersOnly', function(){  
   return {  
     require: 'ngModel',  
     link: function(scope, element, attrs, modelCtrl) {  
       modelCtrl.$parsers.push(function (inputValue) {  

           if (inputValue == undefined) {  
               return '';  
           }  

           var firstParse = inputValue.replace(/[^0-9 . -]/g, '');  

           var safeParse = firstParse.charAt(0);  
           var prepParse = firstParse.substring(1,firstParse.length);   

           var secondParse = safeParse + prepParse.replace(/[^0-9 .]/g, '');  

           var n = secondParse.indexOf(".");  
           var transformedInput;  

           if (n == -1) {  
               transformedInput = secondParse;  
           }  
           else {  
               safeParse = secondParse.substring(0,n+1);  
               firstParse = (secondParse.substring(n+1,secondParse.length)).replace(/[^0-9]/g, '');  
               n = 2;  

               if (firstParse.length <= n) {  
                   transformedInput = safeParse + firstParse;  
               }  
               else {  
                   transformedInput = safeParse + firstParse.substring(0,n);  
               }  
           }  

           var min = -25;  
           var max = 25;  

           if (transformedInput!=inputValue ||   
               transformedInput < min ||   
               transformedInput > max) {  

               var returnValue;  

               if (transformedInput < min || transformedInput > max) {  
                   returnValue = transformedInput.substring(0,transformedInput.length-1);  
               }  
               else {  
                   returnValue=transformedInput;  
               }  

               modelCtrl.$setViewValue(returnValue);  
               modelCtrl.$render();  
           }           

           return returnValue;           
       });  
     }  
   };  
});  

I am happy with the parsing, but the min/max and precision values are hard-coded in. Should I leave this as a directive and pass variables? Or would a function be more appropriate?