var BraCalculator = {
  
  /**
   * The string to be returned when the result could not be calculated.  Overwrite to change this
   */
  unknownString: "Unknown",
  
  cupSizes: ["A", "B", "C", "D", "DD", "E", "EE", "F", "FF", "G", "GG", "H", "HH", 
             "J", "JJ", "K", "KK", "L", "LL", "M", "MM", "N", "NN"],
  
  /**
   * Returns the correct bra size for given under bust and over bust measurements
   * @param {Number} underBust The measurement taken under the bust (in inches)
   * @param {Number} overBust The measurement taken over the bust (in inches)
   * @return {String} The correct bra size for the given measurements (e.g. 32C, 40DD, etc)
   */
  calculateSize: function(underBust, overBust) {
    var bandSize = this.calculateBandSize(underBust);
    var cupSize  = this.calculateCupSize(bandSize, overBust);
    
    if (bandSize && cupSize) {
      return bandSize + cupSize;
    } else {
      return this.unknownString;
    };
  },
  
  /**
   * Calculates the correct band size for a given under bust measurement
   * @param {Number} underBust The measurement under the bust
   * @return {Number} The correct band size
   */
  calculateBandSize: function(underBust) {
    var underBust = parseInt(underBust, 10);
    return underBust + (underBust % 2) + 2;
  },
  
  /**
   * Calculates the Cup size required given the band size and the over bust measurement
   * @param {Number} bandSize The measured band size (should be an even number)
   * @param {Number} overBust The measurement taken over the bust
   * @return {String} The appropriate alphabetical cup size
   */
  calculateCupSize: function(bandSize, overBust) {
    var bandSize = parseInt(bandSize, 10);
    var overBust = parseInt(overBust, 10);
    var diff     = overBust - bandSize;
    
    var result   = this.cupSizes[diff];
    
    //return false if we couldn't lookup a cup size
    return result ? result : false;
  }
};

jQuery(document).ready(function(){
  //add listeners to band and cup measurement text boxes
  jQuery('#back').keyup(Honeys.updateBraSizeCalculation);
  jQuery('#cup').keyup(Honeys.updateBraSizeCalculation);
});

var Honeys = {
  updateBraSizeCalculation: function() {
    var back = jQuery('#back')[0].value;
    var cup  = jQuery('#cup')[0].value;
    
    if (back.length > 0 && cup.length > 0) {
      jQuery('#fit')[0].value = BraCalculator.calculateSize(back, cup);
    };
  }
};