(async () => {

    const topology = await fetch(
        'https://code.highcharts.com/mapdata/custom/world.topo.json'
    ).then(response => response.json());

    const csv = await fetch(
        'https://cdn.jsdelivr.net/gh/highcharts/[email protected]/samples/data/world-population-history.csv'
    ).then(response => response.text());

    // Very simple and case-specific CSV string splitting
    const CSVtoArray = text => text.replace(/^"/, '')
        .replace(/",$/, '')
        .split('","');

    const csvArr = csv.split(/\n/),
        countries = {},
        numRegex = /^[0-9\.]+$/,
        lastCommaRegex = /,\s$/,
        quoteRegex = /\"/g,
        categories = CSVtoArray(csvArr[2]).slice(4);

    let countryChart;

    // Parse the CSV into arrays, one array each country
    csvArr.slice(3).forEach(function (line) {
        var row = CSVtoArray(line),
            data = row.slice(4);

        data.forEach(function (val, i) {
            val = val.replace(quoteRegex, '');
            if (numRegex.test(val)) {
                val = parseInt(val, 10);
            } else if (!val || lastCommaRegex.test(val)) {
                val = null;
            }
            data[i] = val;
        });

        countries[row[1]] = {
            name: row[0],
            code3: row[1],
            data: data
        };
    });

    // For each country, use the latest value for current population
    const data = [];
    for (const code3 in countries) {
        if (Object.hasOwnProperty.call(countries, code3)) {
            const itemData = countries[code3].data;
            let value = null,
                i = itemData.length,
                year;

            while (i--) {
                if (typeof itemData[i] === 'number') {
                    value = itemData[i];
                    year = categories[i];
                    break;
                }
            }
            data.push({
                name: countries[code3].name,
                code3: code3,
                value: value,
                year: year
            });
        }
    }

    // Add lower case codes to the data set for inclusion in the tooltip.pointFormat
    const mapData = Highcharts.geojson(topology);
    mapData.forEach(function (country) {
        country.id = country.properties['hc-key']; // for Chart.get()
        country.flag = country.id.replace('UK', 'GB').toLowerCase();
    });

    // Wrap point.select to get to the total selected points
    Highcharts.wrap(Highcharts.Point.prototype, 'select', function (proceed) {

        proceed.apply(this, Array.prototype.slice.call(arguments, 1));

        const points = mapChart.getSelectedPoints();
        if (points.length) {
            if (points.length === 1) {
                document.querySelector('#info #flag')
                    .className = 'flag ' + points[0].flag;
                document.querySelector('#info h2').innerHTML = points[0].name;
            } else {
                document.querySelector('#info #flag')
                    .className = 'flag';
                document.querySelector('#info h2').innerHTML = 'Comparing countries';

            }
            document.querySelector('#info .subheader')
                .innerHTML = '<h4>Historical population</h4><small><em>Shift + Click on map to compare countries</em></small>';

            if (!countryChart) {
                countryChart = Highcharts.chart('country-chart', {
                    chart: {
                        height: 250,
                        spacingLeft: 0
                    },
                    credits: {
                        enabled: false
                    },
                    title: {
                        text: null
                    },
                    subtitle: {
                        text: null
                    },
                    xAxis: {
                        tickPixelInterval: 50,
                        crosshair: true
                    },
                    yAxis: {
                        title: null,
                        opposite: true
                    },
                    tooltip: {
                        split: true
                    },
                    plotOptions: {
                        series: {
                            animation: {
                                duration: 500
                            },
                            marker: {
                                enabled: false
                            },
                            threshold: 0,
                            pointStart: parseInt(categories[0], 10)
                        }
                    }
                });
            }

            countryChart.series.slice(0).forEach(function (s) {
                s.remove(false);
            });
            points.forEach(function (p) {
                countryChart.addSeries({
                    name: p.name,
                    data: countries[p.code3].data,
                    type: points.length > 1 ? 'line' : 'area'
                }, false);
            });
            countryChart.redraw();

        } else {
            document.querySelector('#info #flag').className = '';
            document.querySelector('#info h2').innerHTML = '';
            document.querySelector('#info .subheader').innerHTML = '';
            if (countryChart) {
                countryChart = countryChart.destroy();
            }
        }
    });

    // Initiate the map chart
    const mapChart = Highcharts.mapChart('container', {

        chart: {
            map: topology
        },

        title: {
            text: 'Population history by country'
        },

        subtitle: {
            text: 'Source: <a href="http://data.worldbank.org/indicator/SP.POP.TOTL/countries/1W?display=default">The World Bank</a>'
        },

        mapNavigation: {
            enabled: true,
            buttonOptions: {
                verticalAlign: 'bottom'
            }
        },

        colorAxis: {
            type: 'logarithmic',
            endOnTick: false,
            startOnTick: false,
            min: 50000
        },

        tooltip: {
            footerFormat: '<span style="font-size: 10px">(Click for details)</span>'
        },

        series: [{
            data: data,
            mapData: mapData,
            joinBy: ['iso-a3', 'code3'],
            name: 'Current population',
            allowPointSelect: true,
            cursor: 'pointer',
            states: {
                select: {
                    color: '#a4edba',
                    borderColor: 'black',
                    dashStyle: 'shortdot'
                }
            },
            borderWidth: 0.5
        }]
    });

    // Pre-select a country
    mapChart.get('us').select();

})();