#ifndef NTP_H
#define NTP_H

#include <Arduino.h>
#include <TimeLib.h>
#include <WiFiUdp.h>

#define LOCALPORT     5000 // Local port to listen for UDP packets
#define NTP_PACKET_SIZE 48 // NTP time stamp is in the first 48 bytes of the message

// A UDP instance to let us send and receive packets over UDP
WiFiUDP udp;

byte packetBuffer[NTP_PACKET_SIZE]; // Buffer to hold incoming and outgoing packets

// Don't hardwire the IP address or we won't get the benefits of the time server pool.
const char *ntpServerName ;//= "time.windows.com";//"1.cn.pool.ntp.org";
IPAddress timeServerIP(120,25,108,11);  //ONENET -- NTP
//IPAddress timeServerIP(183,230,40,42);  //ONENET -- NTP


// Send an NTP request to the time server at the given address
unsigned long sendNTPpacket(IPAddress& address) {

  // Set all bytes in the buffer to 0
  memset(packetBuffer, 0, NTP_PACKET_SIZE);

  // Initialize values needed to form NTP request
  packetBuffer[0] = 0b11100011;   // LI, Version, Mode
  packetBuffer[1] = 0;     // Stratum, or type of clock
  packetBuffer[2] = 6;     // Polling Interval
  packetBuffer[3] = 0xEC;  // Peer Clock Precision
  // 8 bytes of zero for Root Delay & Root Dispersion
  packetBuffer[12]  = 49;
  packetBuffer[13]  = 0x4E;
  packetBuffer[14]  = 49;
  packetBuffer[15]  = 52;

  // All NTP fields have been given values, now
  // you can send a packet requesting a timestamp:
  udp.beginPacket(address, 123); // NTP requests are to port 123
  udp.write(packetBuffer, NTP_PACKET_SIZE);
  udp.endPacket();
}

// NTP Time Provider Code
time_t getNTPTime() {

  int attempts = 10;

  // Try multiple attempts to return the NTP time
  while (attempts--) {

    // Get a server from the pool
    if(ntpServerName != NULL){
        WiFi.hostByName(ntpServerName, timeServerIP);
    }
    Serial.printf("Time server IP address: ");
    Serial.println(timeServerIP);

    while (udp.parsePacket() > 0); // Discard any previously received packets

    Serial.println("Transmitted NTP Request");
    sendNTPpacket(timeServerIP);

    uint32_t beginWait = millis();
    while (millis() - beginWait < 1500) {
      int size = udp.parsePacket();
      if (size >= NTP_PACKET_SIZE) {
        Serial.println("Received NTP Response");
        udp.read(packetBuffer, NTP_PACKET_SIZE);  // Read packet into the buffer
        unsigned long secsSince1900;

        // Convert four bytes starting at location 40 to a long integer
        secsSince1900 =  (unsigned long) packetBuffer[40] << 24;
        secsSince1900 |= (unsigned long) packetBuffer[41] << 16;
        secsSince1900 |= (unsigned long) packetBuffer[42] << 8;
        secsSince1900 |= (unsigned long) packetBuffer[43];

        Serial.println("Got the time");

        return secsSince1900 - 2208988800UL;
      }
      delay(10);
    }
    Serial.println("Retrying NTP request");
    delay(4000);
  }
  Serial.println("No NTP Response");
  return 0;
}

// Login to WiFi network and assign the time sync provider
void initNTP() {

  // Login suceeded so set UDP local port
  udp.begin(LOCALPORT);

  // Set the time provider to NTP
  setSyncProvider(getNTPTime);
}

#endif