function trim(s){
return s.replace(/^\s*(.*?)\s*$/,"$1")
}


// email

function checkEmail (strng) {
var error="";
if (strng == "") {
   error = "- You didn't enter an email address.\n";
}

    var emailFilter=/^.+@.+\..{2,3}$/;
    if (!(emailFilter.test(strng))) { 
       error = "- Please enter a valid email address.\n";
    }
    else {
//test email for illegal characters
       var illegalChars= /[\(\)\<\>\,\;\:\\\"\[\]]/
         if (strng.match(illegalChars)) {
          error = "- The email address contains illegal characters.\n";
       }
    }
return error;    
}


function checkFormat(strng, extension, format) {
var error="";
	if (strng.indexOf(extension) == -1) {
       error = "- The file must be " + format + " format.\n";
    }
return error;
}


// phone number - strip out delimiters and check for 10 digits

function checkPhone (strng) {
var error = "";
if (strng == "") {
   error = "- You didn't enter a phone number.\n";
}

var stripped = strng.replace(/[\(\)\.\-\ ]/g, ''); //strip out acceptable non-numeric characters
    if (isNaN(parseInt(stripped))) {
       error = "- The phone number contains illegal characters.\n";
  
    }
return error;
}


// password - between 6-8 chars, uppercase, lowercase, and numeral

function checkPassword (strng) {
var error = "";
if (strng == "") {
   error = "- You didn't enter a password.\n";
}

    var illegalChars = /[\W_]/; // allow only letters and numbers
    
    if ((strng.length < 6) || (strng.length > 8)) {
       error = "- The password is the wrong length.\n";
    }
    else if (illegalChars.test(strng)) {
      error = "- The password contains illegal characters.\n";
    } 
    else if (!((strng.search(/(a-z)+/)) && (strng.search(/(A-Z)+/)) && (strng.search(/(0-9)+/)))) {
       error = "- The password must contain at least one uppercase letter, one lowercase letter, and one numeral.\n";
    }  
return error;    
}    


// username - 4-10 chars, uc, lc, and underscore only.

function checkUsername (strng) {
var error = "";
if (strng == "") {
   error = "- You didn't enter a username.\n";
}


    var illegalChars = /\W/; // allow letters, numbers, and underscores
    if ((strng.length < 4) || (strng.length > 10)) {
       error = "- The username is the wrong length.\n";
    }
    else if (illegalChars.test(strng)) {
    error = "- The username contains illegal characters.\n";
    } 
return error;
}       


// non-empty textbox

function isEmpty(strng, field) {
var error = "";
	s = trim(strng);
  if (s.length == 0) {
     error = "- The mandatory field '" + field + "' has not been entered.\n"
  }
return error;	  
}

// was textbox altered

function isDifferent(strng) {
var error = ""; 
  if (strng != "Can\'t touch this!") {
     error = "- You altered the inviolate text area.\n";
  }
return error;
}

// get radio button values
function get_radio_value()
{
for (var i=0; i < document.orderform.music.length; i++)
   {
   if (document.orderform.music[i].checked)
      {
      var rad_val = document.orderform.music[i].value;
      }
   }
}

// exactly one radio button is chosen

function checkRadio(radgroup,type) {
	var error = "";
	var radGroupChecked; 

	for (var i=0; i<radgroup.length; i++) {
		if (radgroup[i].checked) {
			radGroupChecked = radgroup[i].value;
		}
		
	}
	
	if(!radGroupChecked){ //if group1Checked does not equal null
		error = "- Please check a "+ type +".\n";
	}
  
	return error;
}

// valid selector from dropdown list

function checkDropdown(choice) {
var error = "";
    if (choice == 0) {
    error = "- You didn't choose an option from the drop-down list.\n";
    }    
return error;
}

function checkCC(s) {
var error = "";

  var i, n, c, r, t;

  // First, reverse the string and remove any non-numeric characters.

  r = "";
  for (i = 0; i < s.length; i++) {
    c = parseInt(s.charAt(i), 10);
    if (c >= 0 && c <= 9) {
      r = c + r;
	}
  }

  // Check for a bad string.

  if (r.length <= 1) {
    error = "- Please enter a valid credit card number.\n";
  }

  // Now run through each single digit to create a new string. Even digits
  // are multiplied by two, odd digits are left alone.

  t = "";
  for (i = 0; i < r.length; i++) {
    c = parseInt(r.charAt(i), 10);
    if (i % 2 != 0)
      c *= 2;
    t = t + c;
  }

  // Finally, add up all the single digits in this string.

  n = 0;
  for (i = 0; i < t.length; i++) {
    c = parseInt(t.charAt(i), 10);
    n = n + c;
  }

  // If the resulting sum is an even multiple of ten (but not zero), the
  // card number is good.

  if (n != 0 && n % 10 == 0) {
	error = "";
  } else {
    error = "- Please enter a valid credit card number.\n";
  }
	
  return error;
}