function handleClientLoad() {
	gapi.load('client:auth2', initClient);
}

function findCurrent(events) {
	const now = Date.now();
	for (const event of events) {
		const start = new Date(event.start.dateTime).getTime();
		const end = new Date(event.end.dateTime).getTime();
		if (start <= now && end >= now) {
			return event;
		}
	}

	return null;
}

function findNext(events) {
	const current = findCurrent(events);
	const currentEnd = current ? new Date(current.end.dateTime).getTime() : null;

	const now = Date.now();
	for (const event of events) {
		const start = new Date(event.start.dateTime).getTime();
		const end = new Date(event.end.dateTime).getTime();
		if (start >= now && (!current || currentEnd == start)) {
			return event;
		}
	}

	return null;
}

function render(events) {
	const curElem = document.getElementById("current");
	const curName = document.getElementById("currentName");
	const curLeft = document.getElementById("currentLeft");
	curElem.classList.remove("break", "event");

	const current = findCurrent(events);
	if (current) {
		curElem.classList.add("event");
		curName.innerText = current.summary;
		const elapsed = Date.now() - new Date(current.start.dateTime).getTime();
		const duration = new Date(current.end.dateTime).getTime() - new Date(current.start.dateTime).getTime();
		const perc = Math.round(elapsed / duration * 100000) / 1000;
		curElem.style.background = `-webkit-linear-gradient(left, #e28659 ${perc.toString()}%, transparent ${perc.toString()}%)`;
	} else {
		curElem.classList.add("break");
		curName.innerText = '😎 Break';
	}

	const nextElem = document.getElementById("next");
	const nextName = document.getElementById("nextName");
	nextElem.classList.remove("break", "event");

	const next = findNext(events);
	if (next) {
		nextElem.classList.add("event");
		nextName.innerText = next.summary;
	} else {
		nextElem.classList.add("break");
		nextName.innerText = '😎 Break';
	}
}

function initClient() {
	gapi.client.init({
		apiKey: 'AIzaSyDzNMBbLqQoSCMiug_7UbUrgaAvnoyzYYU',
		clientId: '969085949455-0vtpi7g173fi63akr1o2eakp9nm1bp4i.apps.googleusercontent.com',
		discoveryDocs: ['https://www.googleapis.com/discovery/v1/apis/calendar/v3/rest'],
		scope: 'https://www.googleapis.com/auth/calendar.readonly',
		ux_mode: 'redirect',
	}).then(() => {
		if (gapi.auth2.getAuthInstance().isSignedIn.get()) {
			return gapi.client.calendar.events.list({
				'calendarId': 'primary',
				'timeMin': (new Date()).toISOString(),
				'showDeleted': false,
				'singleEvents': true,
				'maxResults': 250,
				'orderBy': 'startTime',
			});
		} else {
			gapi.auth2.getAuthInstance().signIn();
			return;
		}
	}).then((response) => {
		setInterval(() => render(response.result.items), 250);
	});
}