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("✈️"),
  "accommodation": emoji_icon("🏨"),
  "conference": emoji_icon("🎤"),
}

function build_map(map_id, coordinates, routes) {
  // Initialize the map
  var map = L.map(map_id).fitBounds(coordinates.map(function(station) {
    return [station.latitude, station.longitude];
  }));

  // Set up the tile layer
  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);

  // Add markers with appropriate icons to the map
  coordinates.forEach(function(item) {
    var marker = L.marker([item.latitude, item.longitude], { icon: icons[item.type] }).addTo(map);
    marker.bindPopup(item.name);
  });

  // Draw routes
  routes.forEach(function(route) {
    var color = {"train": "blue", "flight": "red"}[route.type];
    var style = { weight: 3, opacity: 0.5, color: color };
    if (route.geojson) {
      // If route is defined as GeoJSON
      L.geoJSON(JSON.parse(route.geojson), {
        style: function(feature) { return style; }
      }).addTo(map);
    } else if (route.type === "flight") {
      var flightPath = new L.Geodesic([[route.from, route.to]], style).addTo(map);
    } else {
      // If route is defined by 'from' and 'to' coordinates
      L.polyline([route.from, route.to], style).addTo(map);
    }
  });

  return map;
}