export class NtpClockSync {
    private offsetMs = 0;

    async sync() {
        try {
            const start = performance.now();
            const res = await fetch('https://worldtimeapi.org/api/timezone/Etc/UTC');
            const data = await res.json();
            const end = performance.now();

            const rtt = end - start;
            const serverTimeMs = new Date(data.utc_datetime).getTime();

            // The server time was received at localTimeNow - (rtt/2) approximately
            // So trueTimeNow = serverTimeMs + (rtt/2)
            // offset = trueTimeNow - localTimeNow
            const localTimeNow = Date.now();
            const trueTimeNow = serverTimeMs + (rtt / 2);

            this.offsetMs = trueTimeNow - localTimeNow;
            console.log(`[Clock Sync] Local clock drift calculated: ${this.offsetMs}ms`);
        } catch (err) {
            console.warn('[Clock Sync] Failed. Processing will rely on relative starting stamps.');
            this.offsetMs = 0;
        }
    }

    getTrueTimeMs() {
        return Date.now() + this.offsetMs;
    }
}