function checkUsername() {
	var username = document.getElementById("username").value;
	var requirements = document.getElementById("username-requirements");

	var len3 = username.length >= 3;
	var nosymbol = username.match(/["'<>/&:;\\|{}[\]()]/) == null;
	var nospace = username.match(/[ ]/) == null;

	requirements.classList[len3 ? "add" : "remove"]("len-3");
	requirements.classList[nosymbol ? "add" : "remove"]("nosymbol");
	requirements.classList[nospace ? "add" : "remove"]("nospace");

	requirements.parentElement.classList.remove("all");
	if (!len3) return false;
	if (!nosymbol) return false;
	if (!nospace) return false;
	requirements.parentElement.classList.add("all");
	return true;
}

function checkEmail() {
	var email = document.getElementById("email").value;
	var requirements = document.getElementById("email-requirements");

	// e-mail addresses can really only be verified by attempting to send a mail
	// to them, so this is pretty much useless for client-side anyways
	var valid = email.match(/.+?@.+/) != null;

	requirements.classList[valid ? "add" : "remove"]("valid");

	requirements.parentElement.classList.remove("all");
	if (!valid) return false;
	requirements.parentElement.classList.add("all");
	return true;
}

function checkPassword() {
	var password = document.getElementById("password").value;
	var requirements = document.getElementById("password-requirements");

	var len8 = password.length >= 8;
	var minnum2 = password.match(/[0-9]/g)?.length >= 2;
	var minsym2 = password.match(/[!@#$%^&*()\-=_+[\]{}\\|;:'",<.>/?`~]/g)?.length >= 2;
	var uppercase = password.match(/[A-Z]/) != null;
	var lowercase = password.match(/[a-z]/) != null;

	requirements.classList[len8 ? "add" : "remove"]("len-8");
	requirements.classList[minnum2 ? "add" : "remove"]("digit-2");
	requirements.classList[minsym2 ? "add" : "remove"]("symbol-2");
	requirements.classList[uppercase ? "add" : "remove"]("has-uppercase");
	requirements.classList[lowercase ? "add" : "remove"]("has-lowercase");

	requirements.parentElement.classList.remove("all");
	if (!len8) return false;
	if (!minnum2) return false;
	if (!minsym2) return false;
	if (!uppercase) return false;
	if (!lowercase) return false;
	requirements.parentElement.classList.add("all");
	return true;
}

function checkAllFields() {
	var username = checkUsername();
	var email = checkEmail();
	var password = checkPassword();

	if (!username) return false;
	if (!email) return false;
	if (!password) return false;
	return true;
}

function updateRegisterButton() {
	document.getElementById("register-submit").disabled = !checkAllFields();
}

// update when fields are changed
document.getElementById("username").addEventListener("input", updateRegisterButton);
document.getElementById("email").addEventListener("input", updateRegisterButton);
document.getElementById("password").addEventListener("input", updateRegisterButton);

updateRegisterButton();