(function () {
    'use strict';
    var successCallBackFunction, errorCallBackFunction;

    /**
    * Callback func at successful getting position
    */
    successCallBackFunction = function (position) {
        var lng = position.coords.longitude;
        var lat = position.coords.latitude;

        // revert button element
        document.getElementById('input').innerHTML = "<button id='button'>Draw Map</button>";
        // remove dummy img
        var imgTag = document.getElementById('dummy');
        if(imgTag != null){
            imgTag.parentNode.removeChild(imgTag);
        }   

        latlng2domePolygon(lng, lat);
    };


    /**
    * Callback func at faild getting position
    */
    errorCallBackFunction = function (positionError) {
        alert(positionError.code + ': ' + positionError.message);
    };


    var option = {
        enableHighAccuracy: true, // Whether to use GPS to improve accuracy
        maximumAge: 0, // to hold cache ms
        timeout: 30000 // Timeout ms
    };


    /**
    * Processing at the end of HTML loading
    */
    window.addEventListener('load', function () {

        // Check whether Geolocation API is enabled/disabled
        if (!navigator.geolocation) {
            alert('Geolocation API is disabled');
            return;
        }

        document.getElementById('button').addEventListener('click', function () {
            document.getElementById('input').innerHTML = "<img id='loading' src='loading.gif'>";
            navigator.geolocation.getCurrentPosition(successCallBackFunction, errorCallBackFunction, option);
        }, false);
    }, false);

    
    // Generate domed polygons from [lng lat]
    function latlng2domePolygon(lng, lat) {

        mapboxgl.accessToken = 'pk.eyJ1IjoiaGlyb3NhamkiLCJhIjoiY2szOWljb210MDJxcjNjcXRwZGF6bmJnMiJ9.gin_FUY4wc61PoNKnUWL5Q';
        var center = [lng, lat];
        var radius = 0.122;
        var precision = 0.001525;
        var epsilon = 0.0001;

        var satelliteStyle = {
            "version": 8,
            "sources": {
                "satellite": {
                    "type": "raster",
                    "url": "mapbox://mapbox.satellite",
                    "tileSize": 256
                }
            },
            "layers": [{
                "id": "background",
                "type": "background",
                "paint": {
                    "background-color": "rgb(4,7,14)"
                }
            }, {
                "id": "satellite",
                "type": "raster",
                "source": "satellite"
            }]
        };

        var map = new mapboxgl.Map({
            container: 'map',
            style: satelliteStyle,
            center: center,
            zoom: 16,
            pitch: 60
        });

        var grid = turf.hexGrid(turf.bbox(turf.circle(center, radius)), precision);
        var dome = turf.featureCollection(grid.features.map(function (feature) {
            var point = turf.centroid(feature);
            var distance = turf.distance(center, point);
            if (distance > radius) { return; }

            // sphere r^2 = x^2 + y^2 + z^2
            // therefore z = Math.sqrt(r^2 - x^2 - y^2)
            //             = Math.sqrt(r^2 - (x^2 + y^2))
            // but distance^2 = x^2 + y^2
            // so z = Math.sqrt(r^2 - distance^2)
            var z = Math.sqrt(Math.pow(radius, 2) - Math.pow(distance, 2));
            var normHeight = 56.190 / 122; // to normalize height
            z = isNaN(z) ? 0 : z * normHeight;


            return turf.feature(feature.geometry, {
                base_height: z * 1000, // adopt z / m from z / km
                height: (z * 1000) + (distance * 1000 + epsilon) * 0.1,
                roof_base_height: (z * 1000) + (distance * 950 + epsilon) * 0.1,
                roof_height: (z * 1000) + (distance * 1000 + epsilon) * 0.1
            });
        }).filter(function (feature) { return feature; }));

        map.on('load', function () {
            map.addSource('dome', {
                type: 'geojson',
                data: dome
            });

            map.addLayer({
                id: 'dome',
                type: 'fill-extrusion',
                source: 'dome',
                paint: {
                    'fill-extrusion-color': 'pink',
                    'fill-extrusion-base': {
                        type: 'identity',
                        property: 'base_height'
                    },
                    'fill-extrusion-height': {
                        type: 'identity',
                        property: 'height'
                    },
                    'fill-extrusion-opacity': 0.5
                }
            });

            map.addSource('dome_roof', {
                type: 'geojson',
                data: dome
            });

            map.addLayer({
                id: 'dome_roof',
                type: 'fill-extrusion',
                source: 'dome_roof',
                paint: {
                    'fill-extrusion-color': 'red',
                    'fill-extrusion-base': {
                        type: 'identity',
                        property: 'roof_base_height'
                    },
                    'fill-extrusion-height': {
                        type: 'identity',
                        property: 'roof_height'
                    },
                    'fill-extrusion-opacity': 0.5
                }
            });
        });
    };

}());