/*
  trustcode.js
  
  Forms usage:
  
  onKeyPress="return TCcheckKeyPress(this, event)"
  onKeyUp="TCcheckUpKey(this, event, loadXMLDoc)" />
  
*/

var TC_LENGTH = 12;
var TC_CHECKSUM_METHOD = 3;
var goods = '0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ';  // assume upper case
var oldTC = "";

function asciiValue (c)
{
  // restrict input to a single character
  c = c . charAt (0);

  // loop through all possible ASCII values
  var i;
  for (i = 0; i < 256; ++ i)
  {
    // convert i into a 2-digit hex string
    var h = i . toString (16);
    if (h . length == 1)
    h = "0" + h;

    // insert a % character into the string
    h = "%" + h;

    // determine the character represented by the escape code
    h = unescape (h);

    // if the characters match, we've found the ASCII value
    if (h == c)
      break;
  }
  return i;
}

function checkDigit(s)
{
    var sum = 0;
    var skip = TC_CHECKSUM_METHOD % s.length;
    for (var i=0; i<s.length-1; i++)
    {
      if (i == skip) {
        continue;
      }
      var c = s.charAt(i);
      sum += asciiValue(c);
    }
    var digit = sum % 10;
    return digit.toString();
}

function replaceChars(code)
{
  code = code.toUpperCase();
  code = code.replace(/O/g, '0');
  code = code.replace(/I/g, '1');
  code = code.replace(/B/g, '8');
  code = code.replace(/S/g, '5');
  return code;
}

function TCcheckCode(code)
{
  code = code.replace(/\s/g, '');
  if (TC_CHECKSUM_METHOD > 0){
    digit = checkDigit(code);
    lastpos = code.length - 1;
    if (digit == code.substr(lastpos, 1)){
      return true;
    }
  } else {
    return true;
  }
  return false;
}

// Forms handling

function TCcleanCode(trustcode)
{
  // Make upper case
  var cleancode = trustcode.toUpperCase();
  
  // Strip out spaces and dashes
  var newValue = "";
  for (var i=0; i<cleancode.length; i++) {
    if (goods.indexOf(cleancode.charAt(i)) != -1 && newValue.length < 12) {
      newValue += cleancode.charAt(i);
    }
  }
  return newValue;
}

function TCcheckKeyPress(tcElement, e)
{
  var key, keychar;
  key = getkey(e);

  if ( key==null || key==0 || key==8 || key==9 || key==13 || key==27 || 
    e.metaKey || e.ctrlKey) {  // control / command keys
    return true;
  }

  if (tcElement.value.length >= 12) {
    return false;
  }
  return true;
}

function TCcheckUpKey(tcElement, e, requestHandler, changeHandler)
// We have to put logic in here in case the user pastes text into the tc field
{
  tcElement.value = TCcleanCode(tcElement.value);
  key = getkey(e);

  if (tcElement.value != oldTC || key == 13) {

    // Code has changed
    oldTC = tcElement.value;
    if (changeHandler) {
      changeHandler();
    }

    // Check length
    if (tcElement.value.length < TC_LENGTH) {
      setWarning("Please enter a valid Trustcash number");
    } else if (!TCcheckCode(tcElement.value)) {
        setError("Trustcash number failed check");
    } else {
      // Submit to server
      requestHandler();
    }
  }
}

/* Don't think we need this:

function checkTrustcode(tc)
{
	var reg = /^[a-zA-Z0-9]{12}$/;
	var trustcode = tc;
	while(trustcode.indexOf(" ") > 0) {
		temp = trustcode.substring(0, trustcode.indexOf(" "));
		trustcode = temp + trustcode.substring(trustcode.indexOf(" ") + 1, trustcode.length);
	}
	while(trustcode.indexOf("-") > 0) {
		temp = trustcode.substring(0, trustcode.indexOf("-"));
		trustcode = temp + trustcode.substring(trustcode.indexOf("-") + 1, trustcode.length);
	}
	return reg.test(trustcode);
}

*/