/**
 *
 * \section COPYRIGHT
 *
 * Copyright 2013-2017 Software Radio Systems Limited
 *
 * \section LICENSE
 *
 * This file is part of srsLTE.
 *
 * srsLTE is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Affero General Public License as
 * published by the Free Software Foundation, either version 3 of
 * the License, or (at your option) any later version.
 *
 * srsLTE is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Affero General Public License for more details.
 *
 * A copy of the GNU Affero General Public License can be found in
 * the LICENSE file in the top-level directory of this distribution
 * and at http://www.gnu.org/licenses/.
 *
 */

#include <iostream> 
#include <algorithm>
#include <boost/thread/mutex.hpp>
#include <fcntl.h>
#include <sys/ioctl.h>
#include <netinet/in.h>
#include <sys/socket.h>
#include <linux/if.h>
#include <linux/if_tun.h>
#include "spgw/spgw.h"

namespace srsepc{

spgw*          spgw::m_instance = NULL;
boost::mutex  spgw_instance_mutex;

const uint16_t SPGW_BUFFER_SIZE = 2500;

spgw::spgw():
  m_running(false),
  m_sgi_up(false),
  m_s1u_up(false)
{
  m_pool = srslte::byte_buffer_pool::get_instance();     
  return;
}

spgw::~spgw()
{
  return;
}

spgw*
spgw::get_instance(void)
{
  boost::mutex::scoped_lock lock(spgw_instance_mutex);
  if(NULL == m_instance) {
    m_instance = new spgw();
  }
  return(m_instance);
}

void
spgw::cleanup(void)
{
  boost::mutex::scoped_lock lock(spgw_instance_mutex);
  if(NULL != m_instance) {
    delete m_instance;
    m_instance = NULL;
  }
}

int
spgw::init(spgw_args_t* args, srslte::log_filter *spgw_log)
{
  srslte::error_t err;

  //Init log
  m_spgw_log = spgw_log;
    
  //Init SGi interface
  err = init_sgi_if(args);
  if (err != srslte::ERROR_NONE)
  {
    m_spgw_log->console("Could not initialize the SGi interface.\n");
    return -1;
  }

  //Init S1-U
  err = init_s1u(args);
  if (err != srslte::ERROR_NONE)
  {
    m_spgw_log->console("Could not initialize the S1-U interface.\n");
    return -1;
  }
  m_spgw_log->info("SP-GW Initialized.\n");
  m_spgw_log->console("SP-GW Initialized.\n");
  return 0;
}

void
spgw::stop()
{
  if(m_running)
  {
    m_running = false;
    thread_cancel();
    wait_thread_finish();
 
    //Clean up SGi interface
    if(m_sgi_up)
    {
      close(m_sgi_if);
      close(m_sgi_sock);
    }
    //Clean up S1-U socket
    if(m_s1u_up)
    {
      close(m_s1u);
    }
  }
  return;
}

void
spgw::run_thread()
{
  //Mark the thread as running
  m_running=true;
  srslte::byte_buffer_t *msg;
  msg = m_pool->allocate();
  
  struct sockaddr src_addr;
  socklen_t addrlen;

  int sgi = m_sgi_if;

  fd_set set;
  //struct timeval to;
  int max_fd = std::max(m_s1u,sgi);
  while (m_running)
  {
    msg->reset();
    FD_ZERO(&set);
    FD_SET(m_s1u, &set);
    FD_SET(sgi, &set);
    
    m_spgw_log->info("Waiting for S1-U or SGi packets.\n");
    int n = select(max_fd+1, &set, NULL, NULL, NULL);
    if (n == -1)
    {
      m_spgw_log->error("Error from select\n");
    }
    else if (n)
    {
      m_spgw_log->info("Data is available now.\n");
      if (FD_ISSET(m_s1u, &set))
      {
          msg->N_bytes = recvfrom(m_s1u, msg->msg, SRSLTE_MAX_BUFFER_SIZE_BYTES, 0, &src_addr, &addrlen );
          m_spgw_log->console("Received PDU from S1-U. Bytes %d\n", msg->N_bytes);
          m_spgw_log->debug("Received PDU from S1-U. Bytes %d\n", msg->N_bytes);
      }
      if (FD_ISSET(m_sgi_if, &set))
      {
          m_spgw_log->console("Received PDU from SGi\n");
          msg->N_bytes = read(sgi, msg->msg, SRSLTE_MAX_BUFFER_SIZE_BYTES);
          m_spgw_log->console("Received PDU from SGi. Bytes %d\n", msg->N_bytes);
          m_spgw_log->debug("Received PDU from SGi. Bytes %d\n", msg->N_bytes);
      }
    }
    else
    {
      m_spgw_log->debug("No data from select.\n");
    }
  }
  m_pool->deallocate(msg);
  return;
}

srslte::error_t
spgw::init_sgi_if(spgw_args_t *args)
{
  char dev[IFNAMSIZ] = "srs_spgw_sgi";
  struct ifreq ifr;

  if(m_sgi_up)
  {
    return(srslte::ERROR_ALREADY_STARTED);
  }


  // Construct the TUN device
  m_sgi_if = open("/dev/net/tun", O_RDWR);
  m_spgw_log->info("TUN file descriptor = %d\n", m_sgi_if);
  if(m_sgi_if < 0)
  {
      m_spgw_log->error("Failed to open TUN device: %s\n", strerror(errno));
      return(srslte::ERROR_CANT_START);
  }
  
  memset(&ifr, 0, sizeof(ifr));
  ifr.ifr_flags = IFF_TUN | IFF_NO_PI; 
  strncpy(ifr.ifr_ifrn.ifrn_name, dev, IFNAMSIZ);
  if(ioctl(m_sgi_if, TUNSETIFF, &ifr) < 0)
  {
      m_spgw_log->error("Failed to set TUN device name: %s\n", strerror(errno));
      close(m_sgi_if);
      return(srslte::ERROR_CANT_START);
  }

  // Bring up the interface
  m_sgi_sock = socket(AF_INET, SOCK_DGRAM, 0);

  if(ioctl(m_sgi_sock, SIOCGIFFLAGS, &ifr) < 0)
  {
      m_spgw_log->error("Failed to bring up socket: %s\n", strerror(errno));
      close(m_sgi_if);
      return(srslte::ERROR_CANT_START);
  }
  ifr.ifr_flags |= IFF_UP | IFF_RUNNING;
  if(ioctl(m_sgi_sock, SIOCSIFFLAGS, &ifr) < 0)
  {
      m_spgw_log->error("Failed to set socket flags: %s\n", strerror(errno));
      close(m_sgi_if);
      return(srslte::ERROR_CANT_START);
  }
  
  //Set IP of the interface
  struct sockaddr_in *addr = (struct sockaddr_in*)&ifr.ifr_addr;
  addr->sin_family = AF_INET;
  addr->sin_addr.s_addr = inet_addr(args->sgi_if_addr.c_str());
  addr->sin_port = 0;  
  
  if (ioctl(m_sgi_sock, SIOCSIFADDR, &ifr) < 0) {
    m_spgw_log->error("Failed to set TUN interface IP. Address: %s, Error: %s\n", args->sgi_if_addr.c_str(), strerror(errno));
    close(m_sgi_if);
    close(m_sgi_sock);
    return srslte::ERROR_CANT_START;
  }

  ifr.ifr_netmask.sa_family                                 = AF_INET;
  ((struct sockaddr_in *)&ifr.ifr_netmask)->sin_addr.s_addr = inet_addr("255.255.255.0");
  if (ioctl(m_sgi_sock, SIOCSIFNETMASK, &ifr) < 0) {
    m_spgw_log->error("Failed to set TUN interface Netmask. Error: %s\n", strerror(errno));
    close(m_sgi_if);
    close(m_sgi_sock);
    return srslte::ERROR_CANT_START;
  }
 
  m_sgi_up = true;
  return(srslte::ERROR_NONE);
}

srslte::error_t
spgw::init_s1u(spgw_args_t *args)
{
  //Open S1-U socket
  m_s1u = socket(AF_INET,SOCK_DGRAM,0);
  if (m_s1u == -1)
  {
    m_spgw_log->error("Failed to open socket: %s\n", strerror(errno));
    return srslte::ERROR_CANT_START;
  }
  m_s1u_up = true;

  //Bind the socket
  struct sockaddr_in servaddr;
  servaddr.sin_family = AF_INET;
  servaddr.sin_addr.s_addr=inet_addr(args->gtpu_bind_addr.c_str());
  servaddr.sin_port=htons(GTPU_RX_PORT);

  if (bind(m_s1u,(struct sockaddr *)&servaddr,sizeof(struct sockaddr_in))) {
    m_spgw_log->error("Failed to bind socket: %s\n", strerror(errno));
    return srslte::ERROR_CANT_START;
  }
  m_spgw_log->info("S1-U socket = %d\n", m_s1u);
  return srslte::ERROR_NONE;
}

} //namespace srsepc