/**
 * webtrees: online genealogy
 * Copyright (C) 2019 webtrees development team
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 * GNU General Public License for more details.
 * You should have received a copy of the GNU General Public License
 * along with this program. If not, see <http://www.gnu.org/licenses/>.
 */

"use strict";

const GOOGLE_CHARTS_LIB = "https://www.gstatic.com/charts/loader.js";

/**
 * Statistics class.
 */
class Statistics
{
    /**
     * Constructor.
     *
     * @returns {Statistics}
     */
    constructor()
    {
        // Create singleton instance
        if (!Statistics.instance) {
            Statistics.instance = this;

            this.callbacks   = [];
            this.initialized = false;
            this.loading     = false;
        }

        return Statistics.instance;
    }

    /**
     * Initializes the google chart engine. Loads the chart lib only once.
     *
     * @param {String} locale Locale, e.g. en, de, ...
     */
    init(locale)
    {
        if (this.loading || this.initialized) {
            return;
        }

        var that = this;

        Promise.all([
            this.load(GOOGLE_CHARTS_LIB)
        ]).then(function () {
            google.charts.load(
                "current",
                {
                    "packages": [
                        "corechart",
                        "geochart",
                        "bar"
                    ],
                    "language": locale,
                    // Note: you will need to get a mapsApiKey for your project.
                    // See: https://developers.google.com/chart/interactive/docs/basic_load_libs#load-settings
                    "mapsApiKey": ""
                }
            );

            google.charts.setOnLoadCallback(function () {
                that.callbacks.forEach(function(element) {
                    element();
                });
            });

            that.initialized = true;
        }).catch(function (error) {
            console.log(error);
        });
    }

    /**
     * Dynamically loads a script by the given URL.
     *
     * @param {String} url
     *
     * @returns {Promise}
     */
    load(url)
    {
        if (this.loading) {
            return;
        }

        this.loading = true;

        return new Promise(function (resolve, reject) {
            let script = document.createElement("script");

            script.async = true;
            script.onload = function () {
                resolve(url);
            }
            script.onerror = function () {
                reject(url);
            }

            script.src = url;
            document.body.appendChild(script);
        });
    }

    /**
     * Adds the given callback method to the callback stack or add it directly to
     * the google charts interface once the chart engine is up and running.
     *
     * @param {Function} callback
     */
    addCallback(callback)
    {
        if (this.initialized) {
            google.charts.setOnLoadCallback(callback);
        } else {
            this.callbacks.push(callback);
        }

        $(window).resize(function () {
            callback();
        });
    }

    /**
     * Draws a google chart.
     *
     * @param {String} containerId
     * @param {String} chartType
     * @param {Array}  dataTable
     * @param {Object} options
     */
    drawChart(containerId, chartType, data, options)
    {
        let dataTable = google.visualization.arrayToDataTable(data);

        let wrapper = new google.visualization.ChartWrapper({
            chartType: chartType,
            dataTable: dataTable,
            options: options,
            containerId: containerId
        });

        wrapper.draw();
    }

    /**
     * Draws a pie chart.
     *
     * @param {String} elementId The element id of the HTML element the chart is rendered too
     * @param {Array}  data      The chart data array
     * @param {Object} options   The chart specific options to overwrite the default ones
     */
    drawPieChart(elementId, data, options)
    {
        // Default chart options
        let defaults = {
            title: "",
            height: "100%",
            width: "100%",
            pieStartAngle: 0,
            pieSliceText: "none",
            pieSliceTextStyle: {
                color: "#777"
            },
            pieHole: 0.4,  // Donut
            //is3D: true,  // 3D (not together with pieHole)
            legend: {
                alignment: "center",
                // Flickers on mouseover :(
                labeledValueText: "value",
                position: "labeled"
            },
            chartArea: {
                left: 0,
                top: "5%",
                height: "90%",
                width: "100%"
            },
            tooltip: {
                trigger: "none",
                text: "both"
            },
            backgroundColor: "transparent",
            colors: []
        };

        // Merge default with provided options
        options = Object.assign(defaults, options);

        // Create and draw the chart
        this.drawChart(elementId, "PieChart", data, options);
    }

    /**
     * Draws a column chart.
     *
     * @param {String} elementId The element id of the HTML element the chart is rendered too
     * @param {Array}  data      The chart data array
     * @param {Object} options   The chart specific options to overwrite the default ones
     */
    drawColumnChart(elementId, data, options)
    {
        // Default chart options
        let defaults = {
            title: "",
            subtitle: "",
            titleTextStyle: {
                color: "#757575",
                fontName: "Roboto",
                fontSize: "16px",
                bold: false,
                italic: false
            },
            height: "100%",
            width: "100%",
            vAxis: {
                title: ""
            },
            hAxis: {
                title: ""
            },
            legend: {
                position: "none"
            },
            backgroundColor: "transparent"
        };

        // Merge default with provided options
        options = Object.assign(defaults, options);

        // Create and draw the chart
        this.drawChart(elementId, "ColumnChart", data, options);
    }

    /**
     * Draws a combo chart.
     *
     * @param {String} elementId The element id of the HTML element the chart is rendered too
     * @param {Array}  data      The chart data array
     * @param {Object} options   The chart specific options to overwrite the default ones
     */
    drawComboChart(elementId, data, options)
    {
        // Default chart options
        let defaults = {
            title: "",
            subtitle: "",
            titleTextStyle: {
                color: "#757575",
                fontName: "Roboto",
                fontSize: "16px",
                bold: false,
                italic: false
            },
            height: "100%",
            width: "100%",
            vAxis: {
                title: ""
            },
            hAxis: {
                title: ""
            },
            legend: {
                position: "none"
            },
            seriesType: "bars",
            series: {
                2: {
                    type: "line"
                }
            },
            colors: [],
            backgroundColor: "transparent"
        };

        // Merge default with provided options
        options = Object.assign(defaults, options);

        // Create and draw the chart
        this.drawChart(elementId, "ComboChart", data, options);
    }

    /**
     * Draws a geo chart.
     *
     * @param {String} elementId The element id of the HTML element the chart is rendered too
     * @param {Array}  data      The chart data array
     * @param {Object} options   The chart specific options to overwrite the default ones
     */
    drawGeoChart(elementId, data, options)
    {
        // Default chart options
        let defaults = {
            title: "",
            subtitle: "",
            height: "100%",
            width: "100%"
        };

        // Merge default with provided options
        options = Object.assign(defaults, options);

        // Create and draw the chart
        this.drawChart(elementId, "GeoChart", data, options);
    }
}

// Create singleton instance of class
const statistics = new Statistics();
