const marker_fill_alpha = 1.0;
const marker_edge_colour = 'white';

// Size of the arrow markers used on the map
const marker_scale = 7;
// Offset for the place type icon (multiplier for marker scale)
const marker_label_offset = 0.27 * marker_scale;
// Width and transparency for the edges of the markers
const marker_edge_alpha = 1.0;
const marker_edge_width = 1.0;

let map = null;
let selected_marker = null;
let selected_marker_info = null;
let markers = [];

function createMarker(map, marker_data) {
    // Get the lat-long position from the data
    let lat_lng;
    if (marker_data.lat != null && marker_data.lng != null) {
        lat_lng = new google.maps.LatLng(marker_data.lat, marker_data.lng);

    } else if (marker_data.org_lat != null && marker_data.org_lng != null) {
        lat_lng = new google.maps.LatLng(marker_data.org_lat, marker_data.org_lng);

    } else {
        throw new Error(`No lat/lng set for marker '${marker_data.name}'`)
    }

    const marker = new google.maps.Marker({
        position: lat_lng,
        map: map,
        icon: {
            path: google.maps.SymbolPath.BACKWARD_CLOSED_ARROW,
            strokeColor: marker_edge_colour,
            strokeWeight: marker_edge_width,
            strokeOpacity: marker_edge_alpha,
            fillColor: marker_data.type === 'Organisation' ? '#669933' : '#0099cc',
            fillOpacity: marker_fill_alpha,
            scale: marker_scale,
            labelOrigin: new google.maps.Point(0, -marker_label_offset)
        },
    });

    marker.type = marker_data.type;

    marker.info = new google.maps.InfoWindow({
        content: "<div id='content'>" +
            "<h3><a href=" + marker_data.url + ">" + marker_data.name.replace('&apos;', "'") + "</a></h3>" +
            "</div>"
    });

    // We bind a listener to the current marker so that if it's clicked, it checks for an open info window,
    // closes it, then opens the info window attached to it specifically. Then sets that as the last window.
    google.maps.event.addListener(marker, 'click', function () {
        if (selected_marker_info) {
            selected_marker_info.close();
        }

        selected_marker_info = this.info;
        this.info.open(map, this);
    })

    return marker;
}

// The function called when Google Maps starts up
function initMap() {
    map = new google.maps.Map(
        document.getElementById('map'));

    const bounds = new google.maps.LatLngBounds()
    const markers_data = JSON.parse(
        document.getElementById('map-markers').textContent)

    let markers_loaded = false

    // For each data entry in the json...
    for (const marker_data of markers_data) {
        try {
            const marker = createMarker(map, marker_data);
            markers.push(marker);

            bounds.extend(marker.position);

            if (markers_data.length === 1) {
                selected_marker = marker;
            }

            markers_loaded = true

        } catch (exc) {
            // Just skip and move on to next
        }
    }

    map.fitBounds(bounds)
    if (!markers_loaded) {
        map.panTo({lat: 0, lng: 0})
    }
    setMaxZoom()

    setTimeout(setMaxZoom, 100)

    return map
}

/**
 * Zoom to set level if map is zoomed in more than this.
 */
function setMaxZoom() {
    const max_zoom = 4
    const min_zoom = 2
    const zoom = Math.min(Math.max(min_zoom, map.getZoom()), max_zoom)
    map.setZoom(zoom)
}