if (![].at) {
  Array.prototype.at = function(pos) { return this.slice(pos, pos + 1)[0] }
}

function emoji_icon(emoji) {
  var iconStyle = "<div style='background-color: white; border-radius: 50%; width: 30px; height: 30px; display: flex; justify-content: center; align-items: center; border: 1px solid black;'> <div style='font-size: 18px;'>" + emoji + "</div></div>";

  return L.divIcon({
    className: 'custom-div-icon',
    html: iconStyle,
    iconSize: [60, 60],
    iconAnchor: [15, 15],
  });
}

var icons = {
  "station": emoji_icon("🚉"),
  "airport": emoji_icon("✈️"),
  "ferry_terminal": emoji_icon("🚢"),
  "accommodation": emoji_icon("🏨"),
  "conference": emoji_icon("🎤"),
  "event": emoji_icon("🍷"),
}


function build_map(map_id, coordinates, routes) {
    var map = L.map(map_id).fitBounds(coordinates.map(station => [station.latitude, station.longitude]));

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

    var markers = [];
    var offset_lines = [];

    function getIconBounds(latlng) {
        let iconSize = 20; // Assuming the icon size as a square
        if (!latlng) return null;
        let pixel = map.project(latlng, map.getZoom());
        let sw = map.unproject([pixel.x - iconSize / 2, pixel.y + iconSize / 2], map.getZoom());
        let ne = map.unproject([pixel.x + iconSize / 2, pixel.y - iconSize / 2], map.getZoom());
        return L.latLngBounds(sw, ne);
    }

    function calculateCentroid(markers) {
        let latSum = 0, lngSum = 0, count = 0;
        markers.forEach(marker => {
            latSum += marker.getLatLng().lat;
            lngSum += marker.getLatLng().lng;
            count++;
        });
        return count > 0 ? L.latLng(latSum / count, lngSum / count) : null;
    }

    // Function to detect and group overlapping markers
    function getOverlappingGroups() {
        let groups = [];
        let visited = new Set();

        markers.forEach((marker, index) => {
            if (visited.has(marker)) {
                return;
            }
            let group = [];
            let markerBounds = getIconBounds(marker.getLatLng());

            markers.forEach((otherMarker) => {
                if (marker !== otherMarker && markerBounds.intersects(getIconBounds(otherMarker.getLatLng()))) {
                    group.push(otherMarker);
                    visited.add(otherMarker);
                }
            });

            if (group.length > 0) {
                group.push(marker); // Add the original marker to the group
                groups.push(group);
                visited.add(marker);
            }
        });

        return groups;
    }

    function displaceMarkers(group, zoom) {
        const markerPixelSize = 30; // Width/height of the marker in pixels
        let map = group[0]._map; // Assuming all markers are on the same map

        let centroid = calculateCentroid(group);
        let centroidPoint = map.project(centroid, zoom);

        const radius = markerPixelSize; // Set radius for even distribution
        const angleIncrement = (2 * Math.PI) / group.length; // Evenly space markers

        group.forEach((marker, index) => {
            let angle = index * angleIncrement;
            let newX = centroidPoint.x + radius * Math.cos(angle);
            let newY = centroidPoint.y + radius * Math.sin(angle);
            let newPoint = L.point(newX, newY);
            let newLatLng = map.unproject(newPoint, zoom);

            // Store original position for polyline
            let originalPos = marker.getLatLng();
            marker.setLatLng(newLatLng);

            marker.polyline = L.polyline([originalPos, newLatLng], {color: "gray", weight: 2}).addTo(map);
            offset_lines.push(marker.polyline);
        });
    }

    coordinates.forEach(function(item, index) {
        let latlng = L.latLng(item.latitude, item.longitude);
        let marker = L.marker(latlng, { icon: icons[item.type] }).addTo(map);
        marker.bindPopup(item.name);
        markers.push(marker);
    });

    map.on('zoomend', function() {
        markers.forEach((marker, index) => {
            marker.setLatLng([coordinates[index].latitude, coordinates[index].longitude]); // Reset position on zoom
            if (marker.polyline) {
                map.removeLayer(marker.polyline);
            }
        });

        offset_lines.forEach(polyline => {
            map.removeLayer(polyline);
        });

        let overlappingGroups = getOverlappingGroups();
        // console.log(overlappingGroups); // Process or display groups as needed

        overlappingGroups.forEach(group => displaceMarkers(group, map.getZoom()));
    });

    let overlappingGroups = getOverlappingGroups();
    // console.log(overlappingGroups); // Process or display groups as needed

    overlappingGroups.forEach(group => displaceMarkers(group, map.getZoom()));


    // Draw routes
    routes.forEach(function(route) {
        var color = {"train": "blue", "flight": "red", "unbooked_flight": "orange"}[route.type];
        var style = { weight: 3, opacity: 0.5, color: color };
        if (route.geojson) {
            L.geoJSON(JSON.parse(route.geojson), {
                style: function(feature) { return style; }
            }).addTo(map);
        } else if (route.type === "flight" || route.type === "unbooked_flight") {
            var flightPath = new L.Geodesic([[route.from, route.to]], style).addTo(map);
        } else {
            L.polyline([route.from, route.to], style).addTo(map);
        }
    });

    return map;
}