/* This script is Copyright (c) Paul McFedries and 
Logophilia Limited (http://www.mcfedries.com/).
Permission is granted to use this script as long as 
this Copyright notice remains in place.*/

//Note: script was modified with help from member: MWinter at http://www.dynamicdrive.com/forums/

function CalculateTotal(form) {
  var subTotal = 0,
      discount, field, fieldName, price, quantity, total;

  for(var i = 0, n = form.elements.length; i < n; ++i) {
    field = form.elements[i];
    fieldName = field.name;

    if('PROD' == fieldName.substring(0, 4)) {
      price = parseFloat(fieldName.substring(fieldName.lastIndexOf("_") + 1));
      quantity = parseInt(field.value, 10);

      if(quantity) {
        subTotal += quantity * price;
      }
    }
  }
  form.elements.TOTAL.value = round_decimals(subTotal, 2);

  if(30 <= subTotal) {
    discount = 0.1;
  } else if(100 <= subTotal) {
    discount = 0.2;
  } else {
    discount = 0;
  }
  discount *= subTotal;
  form.elements.discount.value = round_decimals(discount, 2);

  form.elements.FTOTAL.value = round_decimals(subTotal - discount, 2);
}


function round_decimals(original_number, decimals) {
    var result1 = original_number * Math.pow(10, decimals)
    var result2 = Math.round(result1)
    var result3 = result2 / Math.pow(10, decimals)
    return pad_with_zeros(result3, decimals)
}

function pad_with_zeros(rounded_value, decimal_places) {

    // Convert the number to a string
    var value_string = rounded_value.toString()
    
    // Locate the decimal point
    var decimal_location = value_string.indexOf(".")

    // Is there a decimal point?
    if (decimal_location == -1) {
        
        // If no, then all decimal places will be padded with 0s
        decimal_part_length = 0
        
        // If decimal_places is greater than zero, tack on a decimal point
        value_string += decimal_places > 0 ? "." : ""
    }
    else {

        // If yes, then only the extra decimal places will be padded with 0s
        decimal_part_length = value_string.length - decimal_location - 1
    }
    
    // Calculate the number of decimal places that need to be padded with 0s
    var pad_total = decimal_places - decimal_part_length
    
    if (pad_total > 0) {
        
        // Pad the string with 0s
        for (var counter = 1; counter <= pad_total; counter++) 
            value_string += "0"
        }
    return value_string
}