const MapView = (() => {
  let map = null;
  let trackLayers = {};  // trackId → { layer, color, markers, points }
  let currentTrackId = null;
  let hoverMarker = null;
  let stickyPoint = false;

  const COLORS = ['#e74c3c', '#3498db', '#2ecc71', '#f39c12', '#9b59b6', '#1abc9c', '#e67e22', '#34495e'];
  const HOVER_TOLERANCE_PX = 20;
  let colorIndex = 0;

  // ===== Haversine / point helpers =====

  function haversine(lat1, lon1, lat2, lon2) {
    const R = 6371000;
    const dLat = (lat2 - lat1) * Math.PI / 180;
    const dLon = (lon2 - lon1) * Math.PI / 180;
    const a = Math.sin(dLat / 2) ** 2 +
              Math.cos(lat1 * Math.PI / 180) * Math.cos(lat2 * Math.PI / 180) *
              Math.sin(dLon / 2) ** 2;
    return R * 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1 - a));
  }

  // Flatten segments [[lat,lon,ele,time], ...] into [{lat,lon,ele,time,dist}]
  function flattenPoints(trackData) {
    const pts = [];
    let dist = 0;
    for (const seg of (trackData.segments || [])) {
      for (const p of seg) {
        if (pts.length > 0) {
          const prev = pts[pts.length - 1];
          dist += haversine(prev.lat, prev.lon, p[0], p[1]);
        }
        pts.push({ lat: p[0], lon: p[1], ele: p[2] ?? null, time: p[3] ?? null, dist });
      }
    }
    return pts;
  }

  // ===== Init =====

  function init() {
    map = L.map('map');

    const osmLayer = L.tileLayer('https://{s}.tile.openstreetmap.org/{z}/{x}/{y}.png', {
      attribution: '&copy; <a href="https://www.openstreetmap.org/copyright">OpenStreetMap</a> contributors',
      maxZoom: 19
    });

    const topoLayer = L.tileLayer('https://{s}.tile.opentopomap.org/{z}/{x}/{y}.png', {
      attribution: '&copy; <a href="https://opentopomap.org">OpenTopoMap</a> contributors',
      maxZoom: 17
    });

    const satelliteLayer = L.tileLayer('https://server.arcgisonline.com/ArcGIS/rest/services/World_Imagery/MapServer/tile/{z}/{y}/{x}', {
      attribution: 'Tiles &copy; Esri &mdash; Source: Esri, USGS, AeroGRID, IGN, and the GIS User Community',
      maxZoom: 19
    });

    const baseMaps = {
      'OpenStreetMap': osmLayer,
      'Topographic': topoLayer,
      'Satellite': satelliteLayer
    };

    osmLayer.addTo(map);
    L.control.layers(baseMaps).addTo(map);
    L.control.scale({ metric: true, imperial: false }).addTo(map);

    // Hover marker (red dot, non-interactive)
    hoverMarker = L.marker([0, 0], {
      icon: L.divIcon({ className: 'hover-marker', iconSize: [14, 14], iconAnchor: [7, 7] }),
      interactive: false,
      zIndexOffset: 1000
    });

    map.on('mousemove', onMapMouseMove);
    map.on('mouseout',  onMapMouseOut);
    map.on('click',     onMapClick);

    restoreFromHash();
    map.on('moveend zoomend', saveToHash);

    return map;
  }

  // ===== Track management =====

  function getNextColor() {
    const c = COLORS[colorIndex % COLORS.length];
    colorIndex++;
    return c;
  }

  function addTrack(trackData, trackId) {
    if (trackLayers[trackId]) return trackLayers[trackId].layer;

    const color = getNextColor();
    const addedMarkers = [];

    if (!trackData.segments || trackData.segments.length === 0) return null;

    const lines = [];
    for (const seg of trackData.segments) {
      if (!seg || seg.length === 0) continue;
      lines.push(seg.map(p => [p[0], p[1]]));
    }
    if (lines.length === 0) return null;

    const layer = L.polyline(lines, { color, weight: 3, opacity: 0.8 });

    // Start marker (green)
    const firstSeg = trackData.segments.find(s => s && s.length > 0);
    if (firstSeg) {
      const first = firstSeg[0];
      const m = L.circleMarker([first[0], first[1]], {
        radius: 7, color: '#27ae60', fillColor: '#27ae60', fillOpacity: 1, weight: 2
      }).bindTooltip('Start: ' + (trackData.meta?.name || 'Track'));
      m.addTo(map);
      addedMarkers.push(m);
    }

    // End marker (red)
    const lastSeg = [...trackData.segments].reverse().find(s => s && s.length > 0);
    if (lastSeg) {
      const last = lastSeg[lastSeg.length - 1];
      const m = L.circleMarker([last[0], last[1]], {
        radius: 7, color: '#e74c3c', fillColor: '#e74c3c', fillOpacity: 1, weight: 2
      }).bindTooltip('End: ' + (trackData.meta?.name || 'Track'));
      m.addTo(map);
      addedMarkers.push(m);
    }

    layer.addTo(map);
    layer.on('dblclick', (e) => {
      L.DomEvent.stopPropagation(e);
      fitTrack(trackId);
    });
    trackLayers[trackId] = {
      layer,
      color,
      markers: addedMarkers,
      points: flattenPoints(trackData),
      meta: trackData.meta || null
    };

    return layer;
  }

  function removeTrack(trackId) {
    if (trackLayers[trackId]) {
      map.removeLayer(trackLayers[trackId].layer);
      (trackLayers[trackId].markers || []).forEach(m => map.removeLayer(m));
      delete trackLayers[trackId];
    }
  }

  function clearTracks() {
    Object.keys(trackLayers).forEach(id => removeTrack(id));
    colorIndex = 0;
  }

  function fitTrack(trackId) {
    if (!trackLayers[trackId]) return;
    try {
      const bounds = trackLayers[trackId].layer.getBounds();
      if (bounds.isValid()) map.fitBounds(bounds, { padding: [20, 20] });
    } catch (e) {
      console.warn('fitTrack error:', e);
    }
  }

  function fitAll() {
    const layers = Object.values(trackLayers).map(t => t.layer);
    if (layers.length === 0) return;
    try {
      const group = L.featureGroup(layers);
      const bounds = group.getBounds();
      if (bounds.isValid()) map.fitBounds(bounds, { padding: [20, 20] });
    } catch (e) {
      console.warn('fitAll error:', e);
    }
  }

  function hasTrack(trackId)     { return !!trackLayers[trackId]; }
  function getTrackPoints(trackId) { return trackLayers[trackId]?.points || null; }

  // ===== Track highlight (sidebar hover) =====

  let highlightedTrackId = null;

  function highlightTrack(trackId) {
    if (String(highlightedTrackId) === String(trackId)) return;
    unhighlightTrack();
    const tl = trackLayers[trackId];
    if (!tl) return;
    tl.layer.setStyle({ weight: 6, opacity: 1 });
    tl.layer.bringToFront();
    highlightedTrackId = trackId;
  }

  function unhighlightTrack() {
    if (highlightedTrackId === null) return;
    const tl = trackLayers[highlightedTrackId];
    if (tl) tl.layer.setStyle({ weight: 3, opacity: 0.8 });
    highlightedTrackId = null;
  }

  // ===== Hover =====

  function onMapMouseMove(e) {
    if (stickyPoint) return;

    const mp = map.latLngToContainerPoint(e.latlng);
    let nearest = null, nearestD = Infinity, nearestTid = null;

    for (const [tid, tl] of Object.entries(trackLayers)) {
      if (!tl.points) continue;
      for (const p of tl.points) {
        const pp = map.latLngToContainerPoint(L.latLng(p.lat, p.lon));
        const d = mp.distanceTo(pp);
        if (d < nearestD) { nearestD = d; nearest = p; nearestTid = tid; }
      }
    }

    if (nearest && nearestD <= HOVER_TOLERANCE_PX) {
      showHoverMarker(nearest.lat, nearest.lon, nearest, trackLayers[nearestTid]?.meta);
      // Update elevation chart only when hovering the current (active) track
      if (String(nearestTid) === String(currentTrackId) && typeof Elevation !== 'undefined') {
        Elevation.onMapHover(nearest);
      } else if (typeof Elevation !== 'undefined') {
        Elevation.onMapLeave();
      }
    } else {
      hideHoverMarker();
      if (typeof Elevation !== 'undefined') Elevation.onMapLeave();
    }
  }

  function onMapMouseOut() {
    if (stickyPoint) return;
    hideHoverMarker();
    if (typeof Elevation !== 'undefined') Elevation.onMapLeave();
  }

  function onMapClick() {
    if (stickyPoint) {
      stickyPoint = false;
      hideHoverMarker();
      if (typeof Elevation !== 'undefined') Elevation.onMapLeave();
    } else if (map.hasLayer(hoverMarker)) {
      stickyPoint = true;
    }
  }

  function showHoverMarker(lat, lon, point, meta, noTooltip) {
    if (!hoverMarker) return;
    hoverMarker.setLatLng([lat, lon]);
    if (!map.hasLayer(hoverMarker)) hoverMarker.addTo(map);
    hoverMarker.unbindTooltip();
    if (!noTooltip) {
      const content = typeof Elevation !== 'undefined'
        ? Elevation.formatTooltip(point, meta)
        : fallbackTooltip(point, meta);
      hoverMarker.bindTooltip(content, {
        permanent: true,
        direction: 'top',
        className: 'map-tooltip',
        offset: [0, -10]
      }).openTooltip();
    }
  }

  function hideHoverMarker() {
    if (hoverMarker && map && map.hasLayer(hoverMarker)) hoverMarker.remove();
  }

  function fallbackTooltip(p, meta) {
    const dist = p.dist >= 1000 ? (p.dist / 1000).toFixed(2) + ' km' : Math.round(p.dist) + ' m';
    let s = '';
    if (meta?.name) s += `<b>${escHtml(meta.name)}</b><br>`;
    s += `Dist: ${dist}`;
    if (p.ele != null) s += `<br>Ele: ${Math.round(p.ele)} m`;
    return s;
  }

  // ===== Hash state =====

  function saveToHash() {
    if (!map) return;
    const c = map.getCenter();
    const z = map.getZoom();
    const tracks = Object.keys(trackLayers).join(',');
    let hash = `#map=${c.lat.toFixed(5)},${c.lng.toFixed(5)},${z}`;
    if (tracks) hash += `&tracks=${tracks}`;
    if (currentTrackId !== null && currentTrackId !== undefined) hash += `&open=${currentTrackId}`;
    history.replaceState(null, '', hash);
  }

  function restoreFromHash() {
    const params = getHashParams();
    if (params.map) {
      const parts = params.map.split(',');
      if (parts.length === 3) {
        const lat = parseFloat(parts[0]), lng = parseFloat(parts[1]), zoom = parseInt(parts[2]);
        if (!isNaN(lat) && !isNaN(lng) && !isNaN(zoom)) {
          map.setView([lat, lng], zoom);
          return params;
        }
      }
    }
    map.setView([51.505, -0.09], 5);
    return params;
  }

  function getHashParams() {
    const hash = window.location.hash.slice(1);
    const params = {};
    if (!hash) return params;
    hash.split('&').forEach(part => {
      const eqIdx = part.indexOf('=');
      if (eqIdx > 0) {
        const k = part.slice(0, eqIdx), v = part.slice(eqIdx + 1);
        if (k && v) params[k] = v;
      }
    });
    return params;
  }

  function setCurrentTrack(id) {
    currentTrackId = id;
    stickyPoint = false;
    saveToHash();
  }

  function getMap() { return map; }

  return {
    init, addTrack, removeTrack, clearTracks,
    fitTrack, fitAll, hasTrack, getTrackPoints,
    showHoverMarker, hideHoverMarker,
    highlightTrack, unhighlightTrack,
    saveToHash, restoreFromHash, getHashParams,
    setCurrentTrack, getMap
  };
})();