// FormChek.js

// BOI, followed by one or more whitespace characters, followed by EOI.
var reWhitespace = /^\s+$/;

// BOI, followed by one or more characters, followed by @,
// followed by one or more characters, followed by ., 
// followed by one or more characters, followed by EOI.
var reEmail = /^[A-Za-z0-9]+([_\.-][A-Za-z0-9]+)*@[A-Za-z0-9]+([_\.-][A-Za-z0-9]+)*\.([A-Za-z]){2,4}$/i;

// whitespace characters as defined by this sample code
var whitespace = " \t\n\r";

// m is an abbreviation for "missing"
var mPrefix = "Please enter a value into the ";
var mSuffix = " field. This is a required field.";

// s is an abbreviation for "string"
var sEmail = "Email"
var sSubject = "Subject"
var sBody = "Email Body"

// i is an abbreviation for "invalid"
var iEmail = "This field must be a valid email address (like foo@bar.com). Please reenter it now."

// p is an abbreviation for "prompt"
var pEntryPrompt = "Please enter a "
var pEmail = "valid email address (like foo@bar.com)."
var pSubject = "subject for the email message."
var pBody = "message to send with this email."

// Global variable defaultEmptyOK defines default return value 
// for many functions when they are passed the empty string. 
// By default, they will return defaultEmptyOK.
//
// defaultEmptyOK is false, which means that by default, 
// these functions will do "strict" validation.  Function
// isInteger, for example, will only return true if it is
// passed a string containing an integer; if it is passed
// the empty string, it will return false.
//
// You can change this default behavior globally (for all 
// functions which use defaultEmptyOK) by changing the value
// of defaultEmptyOK.
//
// Most of these functions have an optional argument emptyOK
// which allows you to override the default behavior for 
// the duration of a function call.
//
// This functionality is useful because it is possible to
// say "if the user puts anything in this field, it must
// be an integer (or a phone number, or a string, etc.), 
// but it's OK to leave the field empty too."
// This is the case for fields which are optional but which
// must have a certain kind of content if filled in.

var defaultEmptyOK = false

// Attempting to make this library run on Navigator 2.0,
// so I'm supplying this array creation routine as per
// JavaScript 1.0 documentation.  If you're using 
// Navigator 3.0 or later, you don't need to do this;
// you can use the Array constructor instead.

// 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)

{   // Is s empty?
    return (isEmpty(s) || reWhitespace.test(s));
}

// 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);
    
    else {
       return reEmail.test(s)
    }
}

/* FUNCTIONS TO NOTIFY USER OF INPUT REQUIREMENTS OR MISTAKES. */

// Display prompt string s in status bar.
function prompt (s)
{   window.status = s
}

// Display data entry prompt string s in status bar.
function promptEntry (s)
{   window.status = pEntryPrompt + s
}

// Notify user that required field theField is empty.
// String s describes expected contents of theField.value.
// Put focus in theField and return false.
function warnEmpty (theField, s)
{   theField.focus()
    alert(mPrefix + s + mSuffix)
    return false
}

// Notify user that contents of field theField are invalid.
// String s describes expected contents of theField.value.
// Put select theField, pu focus in it, and return false.
function warnInvalid (theField, s)
{   theField.focus()
    theField.select()
    alert(s)
    return false
}




/* FUNCTIONS TO INTERACTIVELY CHECK VARIOUS FIELDS. */

// checkString (TEXTFIELD theField, STRING s, [, BOOLEAN emptyOK==false])
//
// Check that string theField.value is not all whitespace.
//
// For explanation of optional argument emptyOK,
// see comments of function isInteger.
function checkString (theField, s, emptyOK)
{   // Next line is needed on NN3 to avoid "undefined is not a number" error
    // in equality comparison below.
    if (checkString.arguments.length == 2) emptyOK = defaultEmptyOK;
    if ((emptyOK == true) && (isEmpty(theField.value))) return true;
    if (isWhitespace(theField.value)) 
       return warnEmpty (theField, s);
    else return true;
}

// checkEmail (TEXTFIELD theField [, BOOLEAN emptyOK==false])
//
// Check that string theField.value is a valid Email.
//
// For explanation of optional argument emptyOK,
// see comments of function isInteger.

function checkEmail (theField, emptyOK)
{   if (checkEmail.arguments.length == 1) emptyOK = defaultEmptyOK;
    if ((emptyOK == true) && (isEmpty(theField.value))) return true;
    else if (!isEmail(theField.value, false)) 
       return warnInvalid (theField, iEmail);
    else return true;
}