/* Compute the total duration of the run. */
function compute()
{
	const fps = parseInt(document.getElementById("framerate").value);
	const st = document.getElementById("startobj").value;
	const et = document.getElementById("endobj").value;

	if (st === undefined || et === undefined || fps === undefined)
		return;

	const frames = (et - st) * fps;
	const s = Math.round(frames / fps * 1000) / 1000;

	/* Show the time and mod message in the DOM. */
	const sf = Math.trunc(st * fps);
	const ef = Math.trunc(et * fps);
	const t = time_format(s);
	const mod_message = `Mod Note: Retimed (Start Frame: ${
		sf}, End Frame: ${ef}, FPS: ${fps}, Total Time: ${t})`;

	document.getElementById("time").value = t;
	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" : "") + s.toFixed(3);

	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.
 */
function check_fps(event)
{
	fps = event.target.value;
	if (fps > 0 && fps % 1 == 0) {
		document.getElementById("startobj").disabled = false;
		document.getElementById("endobj").disabled = false;
		document.getElementById("compute_button").disabled = false;
	} else {
		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;
	}
}

/* Get current frame from input field (either start time or end time). */
function parse_time(event)
{
	let inptext_frame;
	try {
		inptext_frame = (JSON.parse(event.target.value)).cmt;
	} catch {
		document.getElementById(event.target.id).value = "";
		return;
	}

	if (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}`;
	}

	if (document.getElementById("startobj").value
		&& document.getElementById("endobj").value)
		compute();
}

/* Change the users preferred theme. */
function change_preferance()
{
	const color_switch = document.getElementById("color_preference");

	if (color_switch.checked) {
		document.body.classList.add("dark");
		document.body.classList.remove("light");
		localStorage.setItem("preference", "dark");
	} else {
		document.body.classList.add("light");
		document.body.classList.remove("dark");
		localStorage.setItem("preference", "light");
	}
}