type FetchInit = {
    headers?: Record<string, string | undefined> | Headers;
    method?: string;
    body?: FormData | string;
    [x: string]:
        | string
        | Record<string, string | undefined>
        | undefined
        | FormData
        | Headers;
};

const makeInit = async (init?: FetchInit) => {
    let defaultHeaders: Record<string, string> = {
        'Connection': 'keep-alive',
        'Accept': '*/*',
        'Accept-Language': '*',
        'Sec-Fetch-Mode': 'cors',
        'Accept-Encoding': 'gzip, deflate',
        'Cache-Control': 'max-age=0',
    };
    try {
        const { getHeaders } = await import("../index.js");
        defaultHeaders = {
            ...defaultHeaders,
            ...getHeaders()
        };
    } catch {
        // nothing to do
    }
    if (init?.headers) {
        if (init.headers instanceof Headers) {
            for (const [name, value] of Object.entries(defaultHeaders)) {
                if (!init.headers.get(name)) init.headers.set(name, value);
            }
        } else {
            init.headers = {
                ...defaultHeaders,
                ...init.headers,
            };
        }
    } else {
        init = {
            ...init,
            headers: defaultHeaders,
        };
    }
    return init;
};

/**
 * Fetch with (Android) User Agent
 * @param url
 * @param init
 * @returns response as normal fetch
 */
export async function fetchApi(url: string, init?: FetchInit) {
    init = await makeInit(init);
    // console.log(init.headers);
    // console.log(url, init);
    return await fetch(url, init as RequestInit);
}

/**
 *
 * @param url
 * @param init
 * @returns base64 string of file
 * @example fetchFile('https://avatars.githubusercontent.com/u/81222734?s=48&v=4');
 */
export const fetchFile = async function (url: string, init?: FetchInit) {
    init = await makeInit(init);
    console.log(url, init);
    try {
        const res = await fetch(url, init as RequestInit);
        if (!res.ok) return "";
        const arrayBuffer = await res.arrayBuffer();
        return Buffer.from(arrayBuffer).toString("base64");
    } catch (e) {
        return "";
    }
};

/**
 *
 * @param url
 * @param init
 * @param encoding default: `utf-8`. link: https://developer.mozilla.org/en-US/docs/Web/API/TextDecoder/encoding
 * @returns plain text
 * @example fetchText('https://github.com/LNReader/lnreader', {}, 'gbk');
 */
export const fetchText = async function (
    url: string,
    init?: FetchInit,
    encoding?: string
): Promise<string> {
    init = await makeInit(init);
    console.log(url, init);
    try {
        const res = await fetch(url, init as RequestInit);
        if (!res.ok) return "";
        const arrayBuffer = await res.arrayBuffer();
        const decoder = new TextDecoder(encoding);
        return decoder.decode(arrayBuffer);
    } catch (e) {
        return "";
    }
};