/* NTPClient.cpp */
/* Copyright (C) 2012 mbed.org, MIT License
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy of this software
 * and associated documentation files (the "Software"), to deal in the Software without restriction,
 * including without limitation the rights to use, copy, modify, merge, publish, distribute,
 * sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in all copies or
 * substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING
 * BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
 * DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 */

//Debug is disabled by default
#if 0
//Enable debug
#define __DEBUG__
#include <cstdio>
#define DBG(x, ...) std::printf("[NTPClient : DBG]"x"\r\n", ##__VA_ARGS__);
#define WARN(x, ...) std::printf("[NTPClient : WARN]"x"\r\n", ##__VA_ARGS__);
#define ERR(x, ...) std::printf("[NTPClient : ERR]"x"\r\n", ##__VA_ARGS__);

#else
//Disable debug
#define DBG(x, ...)
#define WARN(x, ...)
#define ERR(x, ...)

#endif

#include "NTPClient.h"

#include "UDPSocket.h"

#include "mbed.h" //time() and set_time()

#define NTP_PORT 123
#define NTP_CLIENT_PORT 0 //Random port
#define NTP_TIMESTAMP_DELTA 2208988800ull //Diff btw a UNIX timestamp (Starting Jan, 1st 1970) and a NTP timestamp (Starting Jan, 1st 1900)

NTPClient::NTPClient() : m_sock()
{


}

NTPResult NTPClient::setTime(const char* host, uint16_t port, uint32_t timeout)
{
#ifdef __DEBUG__
  time_t ctTime;
  ctTime = time(NULL);
  DBG("Time is set to (UTC): %s", ctime(&ctTime));
#endif

  //Create & bind socket
  DBG("Binding socket");
  m_sock.bind(0); //Bind to a random port

  m_sock.set_blocking(false, timeout); //Set not blocking

  struct NTPPacket pkt;

  //Now ping the server and wait for response
  DBG("Ping");
  //Prepare NTP Packet:
  pkt.li = 0; //Leap Indicator : No warning
  pkt.vn = 4; //Version Number : 4
  pkt.mode = 3; //Client mode
  pkt.stratum = 0; //Not relevant here
  pkt.poll = 0; //Not significant as well
  pkt.precision = 0; //Neither this one is

  pkt.rootDelay = 0; //Or this one
  pkt.rootDispersion = 0; //Or that one
  pkt.refId = 0; //...

  pkt.refTm_s = 0;
  pkt.origTm_s = 0;
  pkt.rxTm_s = 0;
  pkt.txTm_s = htonl( NTP_TIMESTAMP_DELTA + time(NULL) ); //WARN: We are in LE format, network byte order is BE

  pkt.refTm_f = pkt.origTm_f = pkt.rxTm_f = pkt.txTm_f = 0;

  Endpoint outEndpoint;

  if( outEndpoint.set_address(host, port) < 0)
  {
    m_sock.close();
    return NTP_DNS;
  }

  //Set timeout, non-blocking and wait using select
  int ret = m_sock.sendTo( outEndpoint, (char*)&pkt, sizeof(NTPPacket) );
  if (ret < 0 )
  {
    ERR("Could not send packet");
    m_sock.close();
    return NTP_CONN;
  }

  //Read response
  Endpoint inEndpoint;

  DBG("Pong");
  do
  {
    ret = m_sock.receiveFrom( inEndpoint, (char*)&pkt, sizeof(NTPPacket) ); //FIXME need a DNS Resolver to actually compare the incoming address with the DNS name
    if(ret < 0)
    {
      ERR("Could not receive packet");
      m_sock.close();
      return NTP_CONN;
    }
  } while( strcmp(outEndpoint.get_address(), inEndpoint.get_address()) != 0 );

  if(ret < sizeof(NTPPacket)) //TODO: Accept chunks
  {
    ERR("Receive packet size does not match");
    m_sock.close();
    return NTP_PRTCL;
  }

  if( pkt.stratum == 0)  //Kiss of death message : Not good !
  {
    ERR("Kissed to death!");
    m_sock.close();
    return NTP_PRTCL;
  }

  //Correct Endianness
  pkt.refTm_s = ntohl( pkt.refTm_s );
  pkt.refTm_f = ntohl( pkt.refTm_f );
  pkt.origTm_s = ntohl( pkt.origTm_s );
  pkt.origTm_f = ntohl( pkt.origTm_f );
  pkt.rxTm_s = ntohl( pkt.rxTm_s );
  pkt.rxTm_f = ntohl( pkt.rxTm_f );
  pkt.txTm_s = ntohl( pkt.txTm_s );
  pkt.txTm_f = ntohl( pkt.txTm_f );

  //Compute offset, see RFC 4330 p.13
  uint32_t destTm_s = (NTP_TIMESTAMP_DELTA + time(NULL));
  int64_t offset = ( (int64_t)( pkt.rxTm_s - pkt.origTm_s ) + (int64_t) ( pkt.txTm_s - destTm_s ) ) / 2; //Avoid overflow
  DBG("Sent @%ul", pkt.txTm_s);
  DBG("Offset: %lld", offset);
  //Set time accordingly
  set_time( time(NULL) + offset );

#ifdef __DEBUG__
  ctTime = time(NULL);
  DBG("Time is now (UTC): %s", ctime(&ctTime));
#endif

  m_sock.close();

  return NTP_OK;
}