function compute()
{
	/*
	 * Get framerate, start frame, and end frame from corresponding elements
	 * Double check they all have a value
	 */
	const fps = parseInt(document.getElementById("framerate").value);
	const sframe = document.getElementById("startobj").value;
	const eframe = document.getElementById("endobj").value;

	if (typeof (sframe) === "undefined" || typeof (eframe) === "undefined"
	        || typeof (fps) === "undefined")
		return;

	const frames = (eframe - sframe) * fps;
	const s = Math.round(frames / fps * 1000) / 1000;

	/* Show the time and mod message in the DOM */
	const ftime = time_format(s);
	const mod_message = `Mod Note: Retimed (Start Frame: ${sframe * fps}, End Frame: ${
		eframe * fps}, FPS: ${fps}, Total Time: ${ftime})`;

	document.getElementById("time").value = ftime;
	document.getElementById("mod_message").disabled = false;
	document.getElementById("mod_message").innerText = mod_message;
	document.getElementById("mod_message_button").disabled = false;
}

/* Convert seconds to human readable time */
function time_format(t)
{
	const h = ~~(t / 3600);
	const m = ~~((t % 3600) / 60);
	const s = ~~t % 60;
	let ret = "";

	if (h > 0)
		ret += h + ":" + (m < 10 ? "0" : "");

	ret += m + ":" + (s < 10 ? "0" : "");
	ret += s;

	/* Milliseconds */
	const st = t.toString();
	if (!isNaN(t) && st.indexOf(".") != -1)
		ret += "." + st.split(".")[1];

	return ret;
}

/* Allow user to copy mod message to clipboard */
function copy_mod_message()
{
	const text_area = document.getElementById("mod_message");
	text_area.focus();
	text_area.select();
	document.execCommand("copy");
}

/* If framerate is invalid, show an error message and disable start and end frame fields */
const check_fps =
        (event) => {
	        if (event.target.value === "" || parseInt(event.target.value) <= 0
	                || isNaN(parseInt(event.target.value))) {
		        document.getElementById("framerate")
		                .setCustomValidity("Please enter a valid framerate.");
		        document.getElementById("framerate").reportValidity();
		        document.getElementById("startobj").disabled = true;
		        document.getElementById("endobj").disabled = true;
		        document.getElementById("compute_button").disabled = true;
	        } else {
		        document.getElementById("startobj").disabled = false;
		        document.getElementById("endobj").disabled = false;
		        document.getElementById("compute_button").disabled = false;
	        }
        }

/* Get current frame from input field (either start time or end time) */
const parse_time = (event) => {
	let inptext_frame = (JSON.parse(event.target.value)).lct;
	if (typeof inptext_frame !== "undefined") {
		const fps = parseInt(document.getElementById("framerate").value);
		const frame_from_obj = (t, fps) => Math.floor(t * fps) / fps;
		const fframe = frame_from_obj(inptext_frame, fps);
		document.getElementById(event.target.id).value = `${fframe}`;
	}
}