// JavaScript Document

function formValidator(){
	// Make quick references to our fields
	var name = document.getElementById('name');
	var email = document.getElementById('email');
	var amazoncode = document.getElementById('amazoncode');
				
	// Check each input in the order that it appears in the form!
	if(isAlphabet(name, "Please enter only letters for your name")){
		if(emailValidator(email, "Please enter a valid email address")){
			if(lengthRestriction(amazoncode, 19, 19)){
				if(isNumeric(amazoncode, "Please enter a valid Amazon order number")){
					return true;
				}	
			}
		}
	}
	return false;
}

function notEmpty(elem, helperMsg){
	if(elem.value.length == 0){
		alert(helperMsg);
		elem.focus(); // set the focus to this input
		return false;
	}
	return true;
}

function isNumeric(elem, helperMsg){
	var numericExpression = /^[-0-9]+$/;
	if(elem.value.match(numericExpression)){
		return true;
	}else{
		alert(helperMsg);
		elem.focus();
		return false;
	}
}

function isAlphabet(elem, helperMsg){
	var alphaExp = /^[a-zA-Z]+$/;
	if(elem.value.match(alphaExp)){
		return true;
	}else{
		alert(helperMsg);
		elem.focus();
		return false;
	}
}

function isAlphanumeric(elem, helperMsg){
	var alphaExp = /^[0-9a-zA-Z]+$/;
	if(elem.value.match(alphaExp)){
		return true;
	}else{
		alert(helperMsg);
		elem.focus();
		return false;
	}
}

function emailValidator(elem, helperMsg){
	var emailExp = /^[\w\-\.\+]+\@[a-zA-Z0-9\.\-]+\.[a-zA-z0-9]{2,4}$/;
	if(elem.value.match(emailExp)){
		return true;
	}else{
		alert(helperMsg);
		elem.focus();
		return false;
	}
}

function lengthRestriction(elem, min, max){
	var uInput = elem.value;
	if(uInput.length >= min && uInput.length <= max){
		return true;
	}else{
		alert("Please enter a valid Amazon order number (xxx-xxx... etc.)");
		elem.focus();
		return false;
	}
}