function emoji_icon(emoji) {
  return L.divIcon({
    className: 'custom-div-icon',
    html: "<div style='font-size: 24px;'>" + emoji + "</div>",
    iconSize: [30, 42],
  });
}

var stationIcon = emoji_icon("🚉");
var airportIcon = 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 icon = item.type === "station" ? stationIcon : airportIcon;
    var marker = L.marker([item.latitude, item.longitude], { icon: icon }).addTo(map);
    marker.bindPopup(item.name);
  });

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

  return map;
}