$(function(){
	form = $('#signinform');
	if( !focus_field )
		focus_field = "username";
	$('input[name=' + focus_field + ']', form).focus();
	
	form.bind("submit", function(e) {
		//username check...
		var username = $.trim( $('input[name=username]', form).val() );
		if( username == '' ) {
			alert('Please fill in the username field!');
			$('input[name=username]', form).focus();
			return false;
		}
		if( username.length < 3){
			alert( "Too short username! It must contain at least 3 symbols." );
			$('input[name=username]', form).focus();
			return false;
		}
		if( !is_valid_str(username) ){
			alert( "Username must contain only [a-zA-Z0-9_] symbols!" );
			$('input[name=username]', form).focus();
			return false;
		}

		//password check...
		var password = $.trim( $('input[name=password]', form).val() );
		if( password == '' ) {
			alert('Please fill in the password field!');
			$('input[name=password]', form).focus();
			return false;
		}
		if( password.length < 5){
			alert( "Too short password! It must contain at least 5 symbols." );
			$('input[name=password]', form).focus();
			return false;
		}

		return true;
	});
});


function is_valid_str(str) {
	return ( str.match(/[^a-zA-Z0-9_]/) ) ? false : true;
}

function is_valid_email(str) { 
	return str.match(/^(\w|-|\d|_)+(\.(\w|-|\d|_)+)*@(\w|-|\d)+(\.(\w|-|\d)+)+$/);
}