/* eslint-disable indent */
    export function getFetchPromise(request) {
        const headers = request.headers || {};

        if (request.dataType === 'json') {
            headers.accept = 'application/json';
        }

        const fetchRequest = {
            headers: headers,
            method: request.type,
            credentials: 'same-origin'
        };

        let contentType = request.contentType;

        if (request.data) {
            if (typeof request.data === 'string') {
                fetchRequest.body = request.data;
            } else {
                fetchRequest.body = paramsToString(request.data);

                contentType = contentType || 'application/x-www-form-urlencoded; charset=UTF-8';
            }
        }

        if (contentType) {
            headers['Content-Type'] = contentType;
        }

        let url = request.url;

        if (request.query) {
            const paramString = paramsToString(request.query);
            if (paramString) {
                url += `?${paramString}`;
            }
        }

        if (!request.timeout) {
            return fetch(url, fetchRequest);
        }

        return fetchWithTimeout(url, fetchRequest, request.timeout);
    }

    function fetchWithTimeout(url, options, timeoutMs) {
        console.debug(`fetchWithTimeout: timeoutMs: ${timeoutMs}, url: ${url}`);

        return new Promise(function (resolve, reject) {
            const timeout = setTimeout(reject, timeoutMs);

            options = options || {};
            options.credentials = 'same-origin';

            fetch(url, options).then(function (response) {
                clearTimeout(timeout);

                console.debug(`fetchWithTimeout: succeeded connecting to url: ${url}`);

                resolve(response);
            }, function (error) {
                clearTimeout(timeout);

                console.debug(`fetchWithTimeout: timed out connecting to url: ${url}`);

                reject(error);
            });
        });
    }

    /**
     * @param params {Record<string, string | number | boolean>}
     * @returns {string} Query string
     */
    function paramsToString(params) {
        return Object.entries(params)
            .filter(([, v]) => v !== null && v !== undefined && v !== '')
            .map(([k, v]) => `${encodeURIComponent(k)}=${encodeURIComponent(v)}`)
            .join('&');
    }

    export function ajax(request) {
        if (!request) {
            throw new Error('Request cannot be null');
        }

        request.headers = request.headers || {};

        console.debug(`requesting url: ${request.url}`);

        return getFetchPromise(request).then(function (response) {
            console.debug(`response status: ${response.status}, url: ${request.url}`);
            if (response.status < 400) {
                if (request.dataType === 'json' || request.headers.accept === 'application/json') {
                    return response.json();
                } else if (request.dataType === 'text' || (response.headers.get('Content-Type') || '').toLowerCase().startsWith('text/')) {
                    return response.text();
                } else {
                    return response;
                }
            } else {
                return Promise.reject(response);
            }
        }, function (err) {
            console.error(`request failed to url: ${request.url}`);
            throw err;
        });
    }
/* eslint-enable indent */