var map;
var markers = [];

function initMap() {
    var osu = {lat: 36.12242, lng: -97.06967};

    map = new google.maps.Map(document.getElementById('map'), {
      zoom: 6,
      center: osu,
      mapTypeId: 'terrain'
    });

    var oklahoma = new google.maps.Polyline({
        path: ok_polygon_coords,
        geodesic: true,
        strokeColor: '#FF7300',
        strokeOpacity: 1.0,
        strokeWeight: 2
    });
    oklahoma.setMap(map);

    // This event listener will call addMarker() when the map is clicked.
    map.addListener('click', function(event) {
        // only do anything for points clicked inside Oklahoma
        if(google.maps.geometry.poly.containsLocation(event.latLng, oklahoma)) {
            deleteMarkers();         // get rid of the existing marker
            addMarker(event.latLng); // add a new marker at the clicked point
            var lat = event.latLng.lat().toFixed(5);
            var lon = event.latLng.lng().toFixed(5);
            document.getElementById("lat").innerHTML = lat;
            document.getElementById("lon").innerHTML = lon;
            update_download_url(lat,lon);
        }
    });

    // Adds a marker at the center of the map.
    addMarker(osu);
    document.getElementById("lat").innerHTML = osu.lat;
    document.getElementById("lon").innerHTML = osu.lng;
    update_download_url(osu.lat,osu.lng);
}

// Adds a marker to the map and push to the array.
function addMarker(location) {
    var marker = new google.maps.Marker({
        position: location,
        map: map
    });
    markers.push(marker);
}

// Sets the map on all markers in the array.
function setMapOnAll(map) {
    for (var i = 0; i < markers.length; i++) {
        markers[i].setMap(map);
    }
}

// Removes the markers from the map, but keeps them in the array.
function clearMarkers() {
    setMapOnAll(null);
}

// Shows any markers currently in the array.
function showMarkers() {
    setMapOnAll(map);
}

// Deletes all markers in the array by removing references to them.
function deleteMarkers() {
    clearMarkers();
    markers = [];
}

function update_download_url(lat,lon) {
    var url = 'http://soilmapnik.hpc.okstate.edu/'+lat+'/'+lon+'/vwc/data_request.csv';
    var htmlstring = '<a href="'+url+'">'+url+'</a>';
    document.getElementById("download-url").innerHTML = htmlstring;
}

window.onload = function () { initMap() };