let map;
let circle;

function update() {
  get_data().then(c=> {
    const d = [c.latitude,c.longitude];
    if (!map) {
      map = L.map('map', {
        center: d,
        zoom: 13
      });
      L.tileLayer(`https://tile.openstreetmap.org/{z}/{x}/{y}.png`, {
          maxZoom: 19,
          attribution: '&copy; <a href="http://www.openstreetmap.org/copyright">OpenStreetMap</a>'
      }).addTo(map);
    }
    if (circle) {
      circle.remove();
      circle=null;
    }
    if (circle == null) {
      circle = L.circle(d, {
          color: 'red',
          fillColor: '#f03',
          fillOpacity: 0.5,
          radius: 50
      }).addTo(map).bindPopup('I\'m here.');
    }
  });
}

function get_data() {
  const res = fetch("lastloc.json").then((a)=> {
    const b = a.json().then((j) => {
      return j;
    })
    return b;
  })
  return res;
}

update();
setInterval(update,10000);