const mapStatus = document.querySelector("#map-status");
const postalLocations = fetch("/postnummer-positioner.json")
  .then((response) => {
    if (!response.ok) throw new Error("Postnummerpositioner mangler.");
    return response.json();
  }).catch(() => null);
let participantMap;
let participantMarkers;
let mapRevision = 0;
let tileError = false;

async function updateParticipantMap(visitors) {
  const revision = ++mapRevision;
  const locations = await postalLocations;
  if (revision !== mapRevision) return;
  if (!locations || typeof L === "undefined") {
    mapStatus.textContent = "Kortet kunne ikke indlæses. Deltagerlisten kan stadig bruges.";
    return;
  }
  if (!participantMap) {
    participantMap = L.map("participant-map").setView([56.1, 10.5], 6);
    L.tileLayer("https://tile.openstreetmap.org/{z}/{x}/{y}.png", {
      maxZoom: 18,
      attribution: '&copy; <a href="https://www.openstreetmap.org/copyright">OpenStreetMap</a> | Postbyer: <a href="https://www.geonames.org/">GeoNames</a>'
    }).on("tileerror", () => {
      if (!tileError) {
        tileError = true;
        mapStatus.textContent += " Baggrundskortet kunne ikke hentes; kontrollér internetforbindelsen.";
      }
    }).addTo(participantMap);
    participantMarkers = L.layerGroup().addTo(participantMap);

  }
  participantMarkers.clearLayers();
  const groups = new Map();
  let missing = 0;
  for (const visitor of visitors) {
    const code = String(visitor.postalCode ?? "").trim();
    if (!locations[code]) { missing++; continue; }
    groups.set(code, (groups.get(code) ?? 0) + 1);
  }
  const bounds = [];
  for (const [code, total] of groups) {
    const location = locations[code];
    const point = [location.lat, location.lng];
    bounds.push(point);
    const popup = document.createElement("div");
    popup.textContent = `${code} ${location.city}: ${total} ${total === 1 ? "deltager" : "deltagere"}`;
    L.circleMarker(point, {
      radius: Math.min(32, 7 + Math.sqrt(total) * 3),
      color: "#16472d", fillColor: "#1d5b39", fillOpacity: 0.65, weight: 2
    }).bindPopup(popup).bindTooltip(`${code}: ${total}`).addTo(participantMarkers);
  }
  if (bounds.length) participantMap.fitBounds(bounds, { padding: [35, 35], maxZoom: 11 });
  else participantMap.setView([56.1, 10.5], 6);
  mapStatus.textContent = visitors.length === 0 ? "Ingen deltagere registreret endnu." :
    `${visitors.length - missing} deltagere fra ${groups.size} postnumre vist.${missing ? ` ${missing} deltagere har et ukendt postnummer og vises ikke på kortet.` : ""}`;
  if (tileError) mapStatus.textContent += " Baggrundskortet kunne ikke hentes; kontrollér internetforbindelsen.";
}