var survey = {}

function getInput(form, inputName) {
	var input = form.elements[inputName];

	if (input.length && input[0].tagName.toLowerCase() == "input") {
		for (var i = 0 ; i < input.length; i++) {
			if (input[i].checked) {
				return input[i];
			}
		}
		return null;
	}
	
	return input;
}

function getValue(form, inputName) {
	var input = getInput(form, inputName);
	if (!input) return null;
	return input.value;	
}

function byId(id) {
	if (typeof(id) == "string") {
		return document.getElementById(id);
	}
	return id;
}

survey.Validator = function(formId) {
	this.form = byId(formId)
}

survey.Validator.prototype.required = function(inputName, message) {
	var input = getInput(this.form, inputName);
	var value = getValue(this.form, inputName);
	if (value == null || value == '') {
		if (input) {
			input.focus();
		}
		alert(message);
		return false;
	}
	return true
}