(function () {
    'use strict';

    var DEFAULT_ERROR_MESSAGE = 'Request failed';

    function getErrorMessage(result) {
        if (result && (typeof result.message === 'string' || typeof result.message === 'number')) {
            return String(result.message);
        }
        if (result && (typeof result.msg === 'string' || typeof result.msg === 'number')) {
            return String(result.msg);
        }
        return DEFAULT_ERROR_MESSAGE;
    }

    function isSuccessCode(code) {
        return code === 0 || code === 200 || code === '0' || code === '200';
    }

    function parseResponse(response) {
        return response.json().catch(function () {
            return { code: -1, message: DEFAULT_ERROR_MESSAGE };
        });
    }

    /**
     * 通用 API 请求封装，统一错误处理
     * @param {string} url 请求地址
     * @param {Object} [options] fetch 选项
     * @returns {Promise<any>} 成功时返回 data / result / 响应体
     */
    function request(url, options) {
        var fetchOptions = Object.assign({ credentials: 'include' }, options || {});

        return fetch(url, fetchOptions)
            .then(function (response) {
                return parseResponse(response).then(function (result) {
                    var code = result && result.code;
                    if (!response.ok || !isSuccessCode(code)) {
                        var err = new Error(getErrorMessage(result));
                        err.code = code != null ? code : (response.status || -1);
                        err.status = response.status;
                        err.data = result;
                        throw err;
                    }
                    return result && (result.data !== undefined ? result.data : result.result !== undefined ? result.result : result);
                });
            })
            .catch(function (err) {
                if (err && err.message) {
                    throw err;
                }
                var fallback = new Error(DEFAULT_ERROR_MESSAGE);
                fallback.code = -1;
                throw fallback;
            });
    }

    /**
     * 带鉴权头的请求，自动注入当前 token
     * @param {string} url 请求地址
     * @param {Object} [options] fetch 选项
     * @param {string} [token] 可选 token，默认使用 window.WELFARE_TOKEN
     * @returns {Promise<any>}
     */
    function requestWithAuth(url, options, token) {
        var authToken = token != null ? token : (window.WELFARE_TOKEN || '');
        var headers = Object.assign({}, options && options.headers);
        if (authToken) {
            headers.Authorization = authToken;
        }
        return request(url, Object.assign({}, options, { headers: headers }));
    }

    window.BEXApi = {
        request: request,
        requestWithAuth: requestWithAuth,
        isSuccessCode: isSuccessCode,
        getErrorMessage: getErrorMessage
    };
})();