Do not request server time when page has no timers

[plack-app-gruntmaster.git] / js / 90-timers.js

let offset = 0;

function update_timer(timer){
	var start = parseInt(timer.dataset.start);
	var stop  = parseInt(timer.dataset.stop);
	var value = parseInt(timer.dataset.value);
	var now   = Math.floor(Date.now() / 1000) + offset;

	var left = stop - now;
	var total = stop - start;
	if(left < 0)
		left = 0;

	if(value) {
		value = Math.max(value * 3 / 10, value * left / total);
		timer.innerHTML = Math.floor(value);
	} else {
		var hours = Math.floor(left / 60 / 60);
		hours = hours < 10 ? '0' + hours : hours;
		var minutes = Math.floor(left / 60) % 60;
		minutes = minutes < 10 ? '0' + minutes : minutes;
		var seconds = left % 60;
		seconds = seconds < 10 ? '0' + seconds : seconds;
		timer.innerHTML = hours + ':' + minutes + ':' + seconds;
	}
}

$(() => {
	$('.timer').each(item => {
		update_timer(item);
		setInterval(() => update_timer(item), 1000);
	});
	if($('.timer').length > 0) {
		let xhr = new XMLHttpRequest();
		xhr.open('HEAD', '/');
		xhr.onload = () => {
			let srvtime = Date.parse(xhr.getResponseHeader('Date'));
			offset = Math.ceil((srvtime - Date.now()) / 1000);
			console.log("Offset from server: " + offset);
		};
		xhr.send();
	}
});