/*
 * Copyright (c) 2017 Cisco and/or its affiliates.
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at:
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#ifndef TAP_POINT_TO_POINT_EPC_HELPER_H
#define TAP_POINT_TO_POINT_EPC_HELPER_H

#include <ns3/object.h>
#include <ns3/ipv4-address-helper.h>
#include <ns3/data-rate.h>
#include <ns3/epc-tft.h>
#include <ns3/eps-bearer.h>
#include <ns3/epc-helper.h>

namespace ns3 {

class Node;
class NetDevice;
class VirtualNetDevice;
class EpcSgwPgwApplication;
class EpcX2;
class EpcMme;

/**
 * \ingroup lte
 * \brief Create an EPC network with PointToPoint links
 *
 * This Helper will create an EPC network topology comprising of a
 * single node that implements both the SGW and PGW functionality, and
 * an MME node. The S1-U, X2-U and X2-C interfaces are realized over
 * PointToPoint links. 
 */

/**
 * NOTE: TapPointToPointEpcHelper is modified from PointToPointEpcHelper in ns3 lte module to support
 * tap device used with lte device and configuration of UE IP address
 */
class TapPointToPointEpcHelper : public EpcHelper
{
public:

  /** 
   * Constructor
   * \param ueSubnetAddr the ue subent ip prefix to be used for configuration, default value is "7.0.0.0"
   * \param ueSubnetMask UesubnetMask is by default "255.0.0.0"
   */
  TapPointToPointEpcHelper (std::string ueSubnetAddr="7.0.0.0", std::string ueSubnetMask="255.0.0.0", uint32_t id=1);

  /** 
   * Destructor
   */
  virtual ~TapPointToPointEpcHelper ();

  // inherited from Object
  /**
   *  Register this type.
   *  \return The object TypeId.
   */
  static TypeId GetTypeId (void);
  virtual void DoDispose ();

  // inherited from EpcHelper
  virtual void AddEnb (Ptr<Node> enbNode, Ptr<NetDevice> lteEnbNetDevice, uint16_t cellId);
  virtual void AddUe (Ptr<NetDevice> ueLteDevice, uint64_t imsi);
  virtual void AddX2Interface (Ptr<Node> enbNode1, Ptr<Node> enbNode2);
  virtual uint8_t ActivateEpsBearer (Ptr<NetDevice> ueLteDevice, uint64_t imsi, Ptr<EpcTft> tft, EpsBearer bearer);
  virtual Ptr<Node> GetPgwNode ();
  virtual Ipv4InterfaceContainer AssignUeIpv4Address (NetDeviceContainer ueDevices);
  virtual Ipv4Address GetUeDefaultGatewayAddress ();

  /** \brief explicity assign IP address to an UE device
   *  
   */
  Ipv4InterfaceContainer AssignUeIpv4Address (Ptr<NetDevice> ueLteDevice, Ipv4Address ueIpAddress);

 private:

  /** 
   * helper to assign addresses to UE devices as well as to the TUN device of the SGW/PGW
   */
  Ipv4AddressHelper m_ueAddressHelper;

  /**
   * SGW-PGW network element
   */
  Ptr<Node> m_sgwPgw;

  /**
   * SGW-PGW application
   */
  Ptr<EpcSgwPgwApplication> m_sgwPgwApp;

  /**
   * TUN device implementing tunneling of user data over GTP-U/UDP/IP
   */
  Ptr<VirtualNetDevice> m_tunDevice;

  /**
   * MME network element
   */
  Ptr<EpcMme> m_mme;

  /**
   * S1-U interfaces
   */

  /** 
   * helper to assign addresses to S1-U NetDevices 
   */
  Ipv4AddressHelper m_s1uIpv4AddressHelper;

  /**
   * The data rate to be used for the next S1-U link to be created
   */
  DataRate m_s1uLinkDataRate;

  /**
   * The delay to be used for the next S1-U link to be created
   */
  Time m_s1uLinkDelay;

  /**
   * The MTU of the next S1-U link to be created. Note that,
   * because of the additional GTP/UDP/IP tunneling overhead,
   * you need a MTU larger than the end-to-end MTU that you
   * want to support.
   */
  uint16_t m_s1uLinkMtu;

  /**
   * UDP port where the GTP-U Socket is bound, fixed by the standard as 2152
   */
  uint16_t m_gtpuUdpPort;

  /**
   * Map storing for each IMSI the corresponding eNB NetDevice
   */
  std::map<uint64_t, Ptr<NetDevice> > m_imsiEnbDeviceMap;

  /** 
   * helper to assign addresses to X2 NetDevices 
   */
  Ipv4AddressHelper m_x2Ipv4AddressHelper;

  /**
   * The data rate to be used for the next X2 link to be created
   */
  DataRate m_x2LinkDataRate;

  /**
   * The delay to be used for the next X2 link to be created
   */
  Time m_x2LinkDelay;

  /**
   * The MTU of the next X2 link to be created. Note that,
   * because of some big X2 messages, you need a big MTU.
   */
  uint16_t m_x2LinkMtu;

};

} // namespace ns3

#endif // TAP_POINT_TO_POINT_EPC_HELPER_H