lazyflat/web/static/map.js

// lazyflat — Leaflet flat map.
//
// Two important properties:
// 1. The map must only be *built* once the container has a real size, because
//    Leaflet initialised on a hidden 0×0 element never loads its tiles.
// 2. The `#wohnungen-body` partial is re-swapped by HTMX every few seconds.
//    To avoid rebuilding Leaflet (and all its tile/marker state) on every
//    poll — which caused the whitescreen + out-of-frame glitches — the map
//    container itself is preserved across swaps via `hx-preserve`, and the
//    marker data is pushed in through a sibling <script id="flats-map-data">
//    element that DOES get swapped. On each swap we diff markers against the
//    fresh data and update in place.

let mapInstance = null;
let markerLayer = null;
let currentFingerprint = "";
const BERLIN_CENTER = [52.52, 13.405];
const BERLIN_ZOOM = 11;

function readMapData() {
  const script = document.getElementById("flats-map-data");
  if (!script) return [];
  try {
    const data = JSON.parse(script.textContent || "[]");
    return Array.isArray(data) ? data : [];
  } catch (e) {
    return [];
  }
}

function fingerprintOf(data) {
  return data
    .map((f) => `${f.lat},${f.lng},${f.address || ""},${f.rent || ""}`)
    .join("|");
}

function renderMarkers(data) {
  if (!mapInstance) return;
  const fp = fingerprintOf(data);
  if (fp === currentFingerprint) return;
  currentFingerprint = fp;
  const geo = data.filter((f) => typeof f.lat === "number" && typeof f.lng === "number").length;
  console.log(`[lazyflat.map] rendering ${geo}/${data.length} markers`);

  if (markerLayer) {
    markerLayer.clearLayers();
  } else {
    markerLayer = L.layerGroup().addTo(mapInstance);
  }

  data.forEach((f) => {
    if (typeof f.lat !== "number" || typeof f.lng !== "number") return;
    const rent = f.rent ? Math.round(f.rent) + " €" : "";
    const rooms = f.rooms ? f.rooms + " Zi" : "";
    const size = f.size ? Math.round(f.size) + " m²" : "";
    const meta = [rooms, size, rent].filter(Boolean).join(" · ");
    const safeAddr = (f.address || "").replace(/</g, "&lt;");
    const safeLink = (f.link || "#").replace(/"/g, "&quot;");
    L.marker([f.lat, f.lng]).addTo(markerLayer).bindPopup(
      `<b>${safeAddr}</b>` + (meta ? `<br>${meta}` : "") +
      `<br><a href="${safeLink}" target="_blank" rel="noopener">Zur Anzeige →</a>`,
    );
  });
}

function buildMap(el) {
  console.log(`[lazyflat.map] building Leaflet instance (container ${el.clientWidth}×${el.clientHeight})`);
  mapInstance = L.map(el, {
    zoomControl: false,
    scrollWheelZoom: false,
    doubleClickZoom: false,
    boxZoom: false,
    touchZoom: false,
    keyboard: false,
  }).setView(BERLIN_CENTER, BERLIN_ZOOM);
  // CartoDB Voyager — clean, Google-Maps-ish base style.
  L.tileLayer("https://{s}.basemaps.cartocdn.com/rastertiles/voyager/{z}/{x}/{y}{r}.png", {
    attribution: "© OpenStreetMap · © CARTO",
    subdomains: "abcd",
    maxZoom: 19,
  }).addTo(mapInstance);
  markerLayer = L.layerGroup().addTo(mapInstance);
}

function ensureMap() {
  const el = document.getElementById("flats-map");
  if (!el || typeof L === "undefined") return;

  // Hidden (0×0) container → tiles would never load; retry after view toggle.
  if (el.clientHeight < 10) return;

  if (!mapInstance) {
    buildMap(el);
  } else if (mapInstance._container !== el) {
    // Container node changed (shouldn't happen thanks to hx-preserve, but
    // defensive: rebuild so Leaflet rebinds to the live element).
    try { mapInstance.remove(); } catch (e) {}
    mapInstance = null;
    markerLayer = null;
    currentFingerprint = "";
    buildMap(el);
  } else {
    try { mapInstance.invalidateSize(); } catch (e) {}
  }
  renderMarkers(readMapData());
}

function wireViewToggle() {
  document.querySelectorAll('input[name="view_mode"]').forEach((r) => {
    if (r.dataset.wired === "1") return;
    r.dataset.wired = "1";
    r.addEventListener("change", (e) => {
      try { localStorage.setItem("lazyflat_view_mode", e.target.value); } catch (err) {}
      requestAnimationFrame(() => requestAnimationFrame(ensureMap));
      setTimeout(ensureMap, 120);
      setTimeout(ensureMap, 400);
    });
  });
}

function restoreView() {
  let stored = null;
  try { stored = localStorage.getItem("lazyflat_view_mode"); } catch (e) {}
  if (!stored) return;
  const el = document.querySelector(`input[name="view_mode"][value="${stored}"]`);
  if (el && !el.checked) {
    el.checked = true;
    requestAnimationFrame(() => requestAnimationFrame(ensureMap));
    setTimeout(ensureMap, 120);
    setTimeout(ensureMap, 400);
  }
}

function onReady() {
  wireViewToggle();
  restoreView();
  ensureMap();
}

document.addEventListener("DOMContentLoaded", onReady);
document.body && document.body.addEventListener("htmx:afterSwap", onReady);