// CREDIT CARD VALIDATION FUNCTIONS

  function ccValidate(f)
  { // Validates the credit card form used in classCredit
    var errMessage="";
    var errFound=false;

    if (empty(f.ccName.value))
    {
      errMessage+="Please enter your Name\n";
      if (!errFound) {f.ccName.focus(); errFound=true;}
    }

    e=f.cardNumber;
    var opt=f.cardType.selectedIndex; // Get index of selected option
    var ccType=f.cardType[opt].text;  // Retrieve displayed text of selected option

    if (e.value=="" || e.value==null || isblank(e.value))
    {
      errMessage+="Please enter your Card number\n";
      if (!errFound) {f.cardNumber.focus(); errFound=true;}
    }

    else
    {
      var z=IsCCNumberValid(e.value, ccType);
      if (z==0)
      {
        errMessage+="The Card number is invalid for that type\n";
        if (!errFound) {f.cardNumber.select(); errFound=true;}
      }
    }

    if (!empty(f.cardSecurityNo.value) && !isNumeric(f.cardSecurityNo.value))
    {
      errMessage+="The Card Security number must be numeric\n";
      if (!errFound) {f.cardSecurityNo.focus(); errFound=true;}
    }

    var ccTypeOption=f.cardType.selectedIndex;
    var ccTypeValue=f.cardType.options[ccTypeOption].text;

    if (ccTypeValue=="Switch" || ccTypeValue=="Solo")
    {
      if (empty(f.cardIssueNo.value))
      {
        errMessage+="Please enter your Card Issue number\n";
        if (!errFound) {f.cardIssueNo.focus(); errFound=true;}
      }
      else
      {
        if (!isNumeric(f.cardIssueNo.value))
        {
          errMessage+="The Card Issue number must be numeric\n";
          if (!errFound) {f.cardIssueNo.focus(); errFound=true;}
        }
      }
    }

    if (f.cardEndYear.value<f.cardStartYear.value ||(f.cardEndYear.value==f.cardStartYear.value && f.cardEndMonth.value<=f.cardStartMonth.value))
    {
      errMessage+="Card End date must be later than card Start date\n";
      if (!errFound) {f.cardEndMonth.focus(); errFound=true;}
    }

    if (errMessage!="")
    {
     alert (errMessage);
     return false;
    }
    else return true;
  }


  function IsCCNumberValid(ccNumber, cardType)
  { // Validates a credit card number for Mastercard, Visa, Amex & Diners Club
    ccNumber=ccNumber.replace(/ /g,"");  // Remove any blanks before validating
    if (ccNumber=="M1111") {return 1;}  // Value for testing
     var retval=0;
    if(cardType!=null)
    {
      if(cardType == "Mastercard"){retval = isMCRD(ccNumber);}
      else if(cardType == "Visa"){retval = isVISA(ccNumber);}
      else if(cardType == "American Express"){retval = isAMEX(ccNumber);}
      else if(cardType == "Diners Club"){retval = isDCCB(ccNumber);}
      else
      { // Don't know algorithm, so just ensure length> 11 & numeric
        if (ccNumber.length<12) {retval=0;}
        else {retval=isNumeric(ccNumber);}
      }
    }
    else
    {
       if(!retval){retval = isMCRD(ccNumber);}
       if(!retval){retval = isVISA(ccNumber);}
       if(!retval){retval = isAMEX(ccNumber);}
       if(!retval){retval = isDCCB(ccNumber);}
    }
    return retval;
  }

  function isMCRD(ccNum)
  { // Validates a Mastercard number
    var preFix = ccNum.substr( 0, 2);
    if(preFix == "51" ||
       preFix == "52" ||
       preFix == "53" ||
       preFix == "54" ||
       preFix == "55")
    {
      if(ccNum.length == 16){return  modTen(ccNum);}
      else {return 0;}
    }
    else
    {
      return 0;
    }
  }

  function isVISA(ccNum)
  { // Validates a Visa number
    var preFix = ccNum.substr(0, 1);
    if(preFix == "4")
    {
      if(ccNum.length == 13 || ccNum.length == 16){return  modTen(ccNum);}
    }
    else
    {
       return 0;
    }
  }

  function isAMEX(ccNum)
  { // Validates an Amex number
    var preFix = ccNum.substr(0, 2);
    if(preFix == "34" || preFix == "37")
    {
      if(ccNum.length == 15){return  modTen(ccNum);}
      else {return 0;}
    }
    else
    {
       return 0;
    }
  }

  function isDCCB(ccNum)
  { // Validates a Diners Club number
    preFix = ccNum.substr(0, 3);
    if(preFix == "300" ||
       preFix == "301" ||
       preFix == "302" ||
       preFix == "303" ||
       preFix == "304" ||
       preFix == "305")
    {
       if(ccNum.length == 14){return  modTen(ccNum);}
       else {return 0;}
    }
    preFix = ccNum.substr(0, 2);
    if(preFix == "36" || preFix == "38")
    {
      if(ccNum.length == 14) {return  modTen(ccNum);}
      else {return 0;}
    }
    else
    {
       return 0;
    }
  }


  function modTen(ccNum)
  { // Modulus 10 calculator used by all credit cards
    var numLen = ccNum.length;
    var tot=0;
    for(var x = numLen; x > 0; x-=2)
    {
      var a=ccNum.substr(x - 1, 1)-0;  // Extract alternate digits as numbers
      tot=tot+a; // and add to the checksum
    }
    for(x = numLen - 1; x > 0; x-=2)
    {
       var y = (ccNum.substr(x - 1, 1)-0) * 2;  // Extract the other alternate digits as numbers, double
                                                // and add each digit of the result to the checksum
       var z=y+"";
       if(z.length == '1'){tot+=y;}
       if(z.length == '2'){tot=tot+1; tot=tot+y-10; }
    }
    tot=tot+"";
    if(tot.substr(tot.length - 1, 1) == '0'){return 1;}
    else{return 0;}
  }


// GENERAL PURPOSE SHOP FUNCTIONS

 var selectedCat;
 function changeCategoryButton(td, categoryLevel, OnOff)
 {
   var fullLength=td.className.length;
   if (td.className.substr(fullLength-8)=="Selected") {return;}
   var newClass="categoryButton" + categoryLevel + OnOff;
   td.className=newClass;
 }

 function updateInCategoryCount(thisCheckbox)
 {
   // Updates a count of the number of Categories this item is included in so that a warning message can be given
   var e=getElement("baseItemForm");
   var catCount=Number(e.includedInCategoryCount.value);
   if (thisCheckbox.checked) {catCount++;}
   else {catCount--;}
   e.includedInCategoryCount.value=catCount;
 }