import {timeoutSignal} from "./Utils";

const headerUrls = ["https://api.atomiq.exchange/"];

type TimeReturnType = {delta: number, timestamp: number};

async function getHeaderTimestamp(url: string): Promise<TimeReturnType> {
    const timeStart = performance.now();
    const resp = await fetch(url, {method: "HEAD", signal: timeoutSignal(3000)});
    const timeDelta = performance.now() - timeStart;
    const dateHeaderValue = resp.headers.get("Date");
    if(dateHeaderValue==null) throw new Error("Date header not returned!");
    return {delta: timeDelta, timestamp: new Date(dateHeaderValue).getTime()};
}

async function getBinanceTimestamp(): Promise<TimeReturnType> {
    const timeStart = performance.now();
    const resp = await fetch("https://api.binance.com/api/v3/time", {signal: timeoutSignal(3000)});
    const timeDelta = performance.now() - timeStart;
    const obj: {serverTime: number} = await resp.json();
    if(obj==null || obj.serverTime==null) throw new Error("Timestamp not returned!");
    return {delta: timeDelta, timestamp: Math.floor(obj.serverTime)};
}

async function getOKXTimestamp(): Promise<TimeReturnType> {
    const timeStart = performance.now();
    const resp = await fetch("https://www.okx.com/api/v5/public/time", {signal: timeoutSignal(3000)});
    const timeDelta = performance.now() - timeStart;
    const obj: {code: number, msg: string, data: [{ts: number}]} = await resp.json();
    if(obj==null || obj.data==null || obj.data[0]==null || obj.data[0].ts==null) throw new Error("Timestamp not returned!");
    return {delta: timeDelta, timestamp: Math.floor(obj.data[0].ts)};
}

async function getAisenseApiTimestamp(): Promise<TimeReturnType> {
    const timeStart = performance.now();
    const resp = await fetch("https://aisenseapi.com/services/v1/timestamp", {signal: timeoutSignal(3000)});
    const timeDelta = performance.now() - timeStart;
    const obj = await resp.json();
    if(obj==null || obj.timestamp==null) throw new Error("Timestamp not returned!");
    return {delta: timeDelta, timestamp: Math.floor(obj.timestamp * 1000)};
}

export async function correctClock() {
    const dateNow: () => number = (Date as any)._now ?? Date.now;
    const dateStart = performance.now();

    try {
        let result: TimeReturnType = await Promise.any([
            ...headerUrls.map(url => getHeaderTimestamp(url)),
            getAisenseApiTimestamp(),
            getBinanceTimestamp(),
            getOKXTimestamp()
        ]);

        const desiredTime = result.timestamp - (result.delta / 2);
        if(Math.abs(Date.now() - desiredTime) < 2000) {
            console.log("AutomaticClockDriftCorrection: correctClock(): Time drift too small, not adjusting!");
            return;
        }

        const timeDrift = dateStart - desiredTime;
        console.log(`AutomaticClockDriftCorrection: correctClock(): Time correction perf.now: ${dateStart}, server: ${desiredTime}, time diff: ${timeDrift}`);
        (Date as any)._now = dateNow;
        (Date as any).now = () => {
            return Math.floor(performance.now() - timeDrift);
        };
    } catch (e: any) {
        if(e instanceof AggregateError) e.message = "Cannot sync time! All servers responded negatively!";
        throw e;
    }
}