#include <WiFi.h>
#include <WiFiUdp.h>
#include <Ticker.h>

#define NTP_SRV "pool.ntp.org"
#define NTP_DELAY 10 //milliseconds
#define NTP_TIMEOUT 10 // seconds

Ticker tkNtp;

const timeval ntpDate() {
  timeval ntpTime = {0};
  WiFiUDP udp;
  uint8_t sendPacket[48] = {0};
  sendPacket[0] = 0x1B;
  udp.begin(123);
  udp.beginPacket(NTP_SRV, 123);
  udp.write(sendPacket, 48);
  uint64_t req_start = micros();
  udp.endPacket();
  uint32_t ntpLoops = NTP_TIMEOUT * 1000UL / NTP_DELAY;
  for (int z=0; z < ntpLoops; z++) {
    delay(NTP_DELAY);
    if (udp.parsePacket()) {
        uint64_t travel = (micros() - req_start) / 2;
        byte recvPacket[48];
        if (udp.read(recvPacket, 48) == 48) {
          udp.stop();
          int64_t sec = 0;
          uint64_t moments = 0;
          for (int x=0; x<4; x++)
            sec += (uint32_t)recvPacket[40+x] << ((3-x)*8); //get the secs
          sec -= 2208988800; // 70 years (1900-1970)
          for (int x=0; x<3; x++)
            moments += (uint32_t)recvPacket[40+4+x] << ((2-x)*8); // get the moments
          moments = moments * 1E6 / 0xFFFFFF; // convert moments to microseconds
          if (travel > moments) {
            sec--;
            moments += 1E6;
          }
          moments -= travel;
          ntpTime = {sec, (int32_t)moments};
          settimeofday((const timeval*)&ntpTime, NULL);
          break;
        }
    }
  }
  return ntpTime;
}

void setup() {
  Serial.begin(115200);
  Serial.println("Hello, ESP32!");
  WiFi.begin("Wokwi-GUEST","");
  WiFi.waitForConnectResult();
  ntpDate();
  tkNtp.attach(3600, ntpDate);
}

void loop() {
  Serial.println(time(NULL));
  delay(10000);
}