// This file contains common Javascript functions organized alphabetically
// INDEX:
//  isEmail(s)    -- checks to ensure a string is an email address
//  isEmpty()     -- checks to see if a string is null or empty
//  isWhitespace  -- checks to see if a string is empty or contains only whitespace
//	trim(string)  -- removes leading and trailing spaces

// DEFINE VARIABLES
// whitespace characters
var whitespace = " \t\n\r";

/****************************************************************/

// isEmail (STRING s [, BOOLEAN emptyOK])
// 
// Email address must be of form a@b.c ... in other words:
// * there must be at least one character before the @
// * there must be at least one character before and after the .
// * the characters @ and . are both required
//
// For explanation of optional argument emptyOK,
// see comments of function isInteger.

function isEmail (s)
{   if (isEmpty(s)) 
       if (isEmail.arguments.length == 1) return defaultEmptyOK;
       else return (isEmail.arguments[1] == true);
   
    // is s whitespace?
    if (isWhitespace(s)) return false;
    
    // there must be >= 1 character before @, so we
    // start looking at character position 1 
    // (i.e. second character)
    var i = 1;
    var sLength = s.length;

    // look for @
    while ((i < sLength) && (s.charAt(i) != "@"))
    { i++;
    }

    if ((i >= sLength) || (s.charAt(i) != "@")) 
	   return false;
    else i += 2;

    // look for .
    while ((i < sLength) && (s.charAt(i) != "."))
    { i++
    }

    // there must be at least one character after the .
    if ((i >= sLength - 1) || (s.charAt(i) != ".")) return false;
    else return true;
}

/****************************************************************/

// Check whether string s is empty.

function isEmpty(s)
{   return ((s == null) || (s.length == 0))
}

/****************************************************************/

// Returns true if string s is empty or 
// whitespace characters only.

function isWhitespace (s)

{   var i;

    // Is s empty?
    if (isEmpty(s)) return true;

    // Search through string's characters one by one
    // until we find a non-whitespace character.
    // When we do, return false; if we don't, return true.

    for (i = 0; i < s.length; i++)
    {   
	// Check that current character isn't whitespace.
	var c = s.charAt(i);

	if (whitespace.indexOf(c) == -1) return false;
    }

    // All characters are whitespace.
    return true;
}


// ************************************************************************************

// This function trims the spaces from the beginning and end
// of string s and returns the string with no spaces
function trim(s){
  while (s.charAt(0) == ' ') {
    s = s.substring(1,s.length);
  };
  while (s.charAt(s.length - 1) == ' ') {
    s = s.substring(0, (s.length - 1));
  };
  return s;
};