const RBRACKET = /\[\]$/;

/*
 * Part of the `serializeQueryParams` helper function.
 */
function add(s: Array<any>, k: string, v?: string | (() => string)) {
    // Strip out keys with undefined value and replace null values with
    // empty strings (mimics jQuery.ajax)
    if (v === undefined) {
        return;
    } else if (v === null) {
        v = '';
    }

    v = typeof v === 'function' ? v() : v;
    s[s.length] = `${encodeURIComponent(k)}=${encodeURIComponent(v)}`;
}

/*
 * Part of the `serializeQueryParams` helper function.
 */
function isPlainObject(obj: any): boolean {
    return Object.prototype.toString.call(obj) === '[object Object]';
}

/*
 * Helper function that turns the data/body of a request into a query param string.
 * This is directly copied from jQuery.param.
 */
export function serializeQueryParams(queryParamsObject: object | string): string {
    var s: any[] = [];

    function buildParams(prefix: string, obj: any) {
        var i, len, key;

        if (prefix) {
            if (Array.isArray(obj)) {
                for (i = 0, len = obj.length; i < len; i++) {
                    if (RBRACKET.test(prefix)) {
                        add(s, prefix, obj[i]);
                    } else {
                        buildParams(prefix + '[' + (typeof obj[i] === 'object' ? i : '') + ']', obj[i]);
                    }
                }
            } else if (isPlainObject(obj)) {
                for (key in obj) {
                    buildParams(prefix + '[' + key + ']', obj[key]);
                }
            } else {
                add(s, prefix, obj);
            }
        } else if (Array.isArray(obj)) {
            for (i = 0, len = obj.length; i < len; i++) {
                add(s, obj[i].name, obj[i].value);
            }
        } else {
            for (key in obj) {
                buildParams(key, obj[key]);
            }
        }
        return s;
    }

    return buildParams('', queryParamsObject).join('&').replace(/%20/g, '+');
}