Currency - comments

import { System } from "../../util/system";
import { Url } from "../../util/url";

/**
 * Class for currency requests on frontend side
 *
 * Singleton - access with Rum_Currency.Instance()
 */
export class Rum_Currency
{
    /**
     * Singleton instance
     */
    private static instance: Rum_Currency;

    /**
     * Default constructor (private = non-instantiable object)
     */
    private constructor()
    {

    }

    /**
     * Instance function (get object) - singleton pattern
     * @returns Object instance
     */
    public static Instance()
    {
        if (!Rum_Currency.instance)
        {
            Rum_Currency.instance = new Rum_Currency();
        }

        return Rum_Currency.instance;
    }

    /**
     * Request server to obtain list of all currencies
     * @returns JSON - result (status code), error (in case of any), currency (list of currencies)
     */
    public GetCurrencies(): Promise<any>
    {
        return Url.FetchJson(System.BaseURL() + "api/v1/rum/currency/read.php", true, {}, System.progress);
    }

    /**
     * Request server to obtain single currency
     * @param currency ID of the currency to request
     * @returns JSON - result (status code), error (in case of any), currency (array containing single element with specific currency)
     */
    public GetCurrency(currency: number): Promise<any>
    {
        var json = { "id": currency };

        return Url.FetchJson(System.BaseURL() + "api/v1/rum/currency/read.php", true, json, System.progress);
    }

    /**
     * Request currency rates from specified currency to others (base currency - EUR, or all others if requested on EUR)
     * @param from_id ID of the currency for which we request rates
     * @returns JSON - result (status code), error (in case of any), currency_rate (array containing currency rates for specified currency)
     */
    public GetRates(from_id: number): Promise<any>
    {
        var json = { "from_id": from_id };

        return Url.FetchJson(System.BaseURL() + "api/v1/rum/currency_rate/read.php", true, json, System.progress);
    }
}