const generateButton = document.getElementById("generate-pow");
generateButton.style.display = "block";

const usernameField = document.getElementById("username");
const messageField = document.getElementById("message");
const powField = document.getElementById("proof-of-work");

const hash = (message) =>
	crypto.subtle.digest("SHA-1",
		(new TextEncoder()).encode(message)
	);
const isValidHash = (hashBuffer) =>
	Array.from(new Uint8Array(hashBuffer))
		.map(byte => byte.toString(16).padStart(2, "0"))
		.join("").startsWith("00000");

const messageBase = () => usernameField.value + "\0" + messageField.value + "\0";

generateButton.onclick = async (event) => {
	event.preventDefault();
	const base = messageBase();
	let currentNonce = 0;

	powField.disabled = true;
	powField.value = "Generating... Please wait";

	console.log("Starting PoW generation, this may take a while....");
	while (!isValidHash(await hash(base + currentNonce)))
		++currentNonce;
	console.log("Done!");
	powField.value = currentNonce;
	powField.disabled = false;
};