var validationHandlers = new Array();
function register_validation_handler ( validation_handler ) {
	// Add `function` to the list of functions that will be called when validating
	// the page.
	validationHandlers.push( validation_handler );
	return validation_handler;
}
function validate_form () {
	/* Global function for validating a form. This examines the validationHandlers
	 * array and produces an aggregate result. If there were failures then the user
	 * is prompted and the function returns false else it returns true.
	 *
	 * This function is the only intended interface to the validation functions here
	 * beyond the register_validation_handler( ... ) function.
	 */
	// Get an object to hold everything for us.
	var overall = new ValidationResult();
	// Loop through each installed validation handler and add the individual result to the
	// cumulative total.
	for (var ix = 0; ix < validationHandlers.length; ix++) {
		// Retrieve each handler in turn.
		var handler = validationHandlers[ ix ];
		// And execute it.
		var result = handler();
		// Maintain an overall failure state
		if (result.failed)
			overall.failed = result.failed;
		// Copy over the focus field if it hasn't been set before
		if (overall.focus_field == null && result.focus_field != null)
			overall.focus_field = result.focus_field;
		// Pass in the bad field failure messages.
		overall.bad_fields = overall.bad_fields.concat( result.bad_fields );
		// And any other errors.
		overall.errors = overall.errors.concat( result.errors );
	}
	// Validation is now complete.
	// Generate a 'bad fields' message if there are any.
	if (overall.bad_fields[0] != null) {
		if (overall.bad_fields.length > 1)
			overall.error("Please check the following fields for accuracy:\n"+
				overall.bad_fields.join("\n") );
		else
			overall.error("Please check the " + overall.bad_fields[0] + " field for accuracy.");
	}
	// Report any and all error messages
	if (overall.errors[0] != null)
		alert(overall.errors.join("\n\n"));
	// Since success is the opposite of failure... negate failure to return the success value.
	return ! overall.failed
}
function ValidationResult () { 
	/*
	 * The ValidationResult constructor.
	 * For normal validation see the function validate_form().
	 *
	 * Execute ` ... = new ValidationResult(); ` to create a new object.
	 *
	 * By default, validation objects are considered to have passed muster. Your validation
	 * code is expected to signal a failure by logging an error message with error(...) or bad data
	 * with bad_field( ... ).
	 *
	 * The end result can be examined by looking at the failed property.
	 */
	// Create a new generic object
	var result = new Object;
	// Set all of the properties to their default values.
	result.failed = false;
	result.bad_fields = new Array();
	result.errors = new Array();
	result.exit_immediately = false;
	result.focus_field = null;
	// Install methods into the new object.
	result.bad_field = validation_bad_field_method;
	result.error = validation_error_method;
	result.debug = validation_debug_method;
	result.debug = validation_debug_method;
	return result;
}
function validation_bad_field_method ( field_name, message ) {
	// Mark this field as a failure with a message
	if ( this.focus_field == null)
		this.focus_field = field_name;
	// Do some auto-defaulting.
	if ( message == null || message == '' )
		message = field_name;
	this.bad_fields.push( message );
	this.failed = true;
	return this;
}
function validation_error_method ( message ) {
	// Add 'message' to the list of errors, mark the object as failing validation
	this.errors.push( message );
	this.failed = true;
	return this;
};
function validation_debug_method () {
	// Prompt the user with the internal state of the validation object.
	alert(
		'failed:'+this.failed+
		"\nbad_fields:"+this.bad_fields.join(",")+
		"\nerrors:"+this.errors.join(",")+
		"\nexit_immediately:"+this.exit_immediately+
		"\nfocus_field:"+this.focus_field);
	return this;
}