/**
 *
 * \section COPYRIGHT
 *
 * Copyright 2013-2021 Software Radio Systems Limited
 *
 * By using this file, you agree to the terms and conditions set
 * forth in the LICENSE file which can be found at the top level of
 * the distribution.
 *
 */

#include "srsran/asn1/s1ap.h"
#include <linux/ip.h>
#include <numeric>
#include <random>

#include "srsenb/hdr/stack/upper/gtpu.h"
#include "srsenb/test/common/dummy_classes.h"
#include "srsran/common/network_utils.h"
#include "srsran/common/test_common.h"
#include "srsran/upper/gtpu.h"

namespace srsenb {

static const size_t PDU_HEADER_SIZE = 20;

class stack_tester : public stack_interface_gtpu_lte
{
public:
  int  s1u_fd;
  void add_gtpu_s1u_socket_handler(int fd) { s1u_fd = fd; }
  void add_gtpu_m1u_socket_handler(int fd) {}
};

class pdcp_tester : public pdcp_dummy
{
public:
  void write_sdu(uint16_t rnti, uint32_t lcid, srsran::unique_byte_buffer_t sdu, int pdcp_sn) override
  {
    last_sdu     = std::move(sdu);
    last_pdcp_sn = pdcp_sn;
    last_rnti    = rnti;
    last_lcid    = lcid;
  }
  std::map<uint32_t, srsran::unique_byte_buffer_t> get_buffered_pdus(uint16_t rnti, uint32_t lcid) override
  {
    return std::move(buffered_pdus);
  }
  void send_status_report(uint16_t rnti) override {}
  void send_status_report(uint16_t rnti, uint32_t lcid) override {}

  void push_buffered_pdu(uint32_t sn, srsran::unique_byte_buffer_t pdu) { buffered_pdus[sn] = std::move(pdu); }

  void clear()
  {
    last_sdu     = nullptr;
    last_pdcp_sn = -1;
    last_lcid    = 0;
    last_rnti    = SRSRAN_INVALID_RNTI;
  }

  std::map<uint32_t, srsran::unique_byte_buffer_t> buffered_pdus;
  srsran::unique_byte_buffer_t                     last_sdu;
  int                                              last_pdcp_sn = -1;
  uint16_t                                         last_rnti    = SRSRAN_INVALID_RNTI;
  uint32_t                                         last_lcid    = 0;
};

int GTPU_PORT = 2152;

srsran::unique_byte_buffer_t encode_ipv4_packet(srsran::span<uint8_t>     data,
                                                uint32_t                  teid,
                                                const struct sockaddr_in& src_sockaddr_in,
                                                const struct sockaddr_in& dest_sockaddr_in)
{
  srsran::unique_byte_buffer_t pdu = srsran::make_byte_buffer();

  struct iphdr ip_pkt = {};
  ip_pkt.version      = 4;
  ip_pkt.tot_len      = htons(data.size() + sizeof(struct iphdr));
  ip_pkt.saddr        = src_sockaddr_in.sin_addr.s_addr;
  ip_pkt.daddr        = dest_sockaddr_in.sin_addr.s_addr;
  pdu->append_bytes((uint8_t*)&ip_pkt, sizeof(struct iphdr));
  pdu->append_bytes(data.data(), data.size());

  return pdu;
}

srsran::unique_byte_buffer_t encode_gtpu_packet(srsran::span<uint8_t>     data,
                                                uint32_t                  teid,
                                                const struct sockaddr_in& src_sockaddr_in,
                                                const struct sockaddr_in& dest_sockaddr_in)
{
  srsran::unique_byte_buffer_t pdu = encode_ipv4_packet(data, teid, src_sockaddr_in, dest_sockaddr_in);

  // header
  srsran::gtpu_header_t header = {};
  header.flags                 = GTPU_FLAGS_VERSION_V1 | GTPU_FLAGS_GTP_PROTOCOL;
  header.message_type          = GTPU_MSG_DATA_PDU;
  header.length                = pdu->N_bytes;
  header.teid                  = teid;

  gtpu_write_header(&header, pdu.get(), srslog::fetch_basic_logger("GTPU"));
  return pdu;
}

srsran::unique_byte_buffer_t encode_end_marker(uint32_t teid)
{
  srsran::unique_byte_buffer_t pdu = srsran::make_byte_buffer();

  // header
  srsran::gtpu_header_t header = {};
  header.flags                 = GTPU_FLAGS_VERSION_V1 | GTPU_FLAGS_GTP_PROTOCOL;
  header.message_type          = GTPU_MSG_END_MARKER;
  header.length                = 0;
  header.teid                  = teid;

  gtpu_write_header(&header, pdu.get(), srslog::fetch_basic_logger("GTPU"));
  return pdu;
}

srsran::unique_byte_buffer_t read_socket(int fd)
{
  srsran::unique_byte_buffer_t pdu = srsran::make_byte_buffer();
  pdu->N_bytes                     = read(fd, pdu->msg, pdu->get_tailroom());
  return pdu;
}

int test_gtpu_direct_tunneling()
{
  uint16_t           rnti = 0x46, rnti2 = 0x50;
  uint32_t           drb1         = 3;
  uint32_t           sgw_teidout1 = 1, sgw_teidout2 = 2;
  const char *       sgw_addr_str = "127.0.0.1", *senb_addr_str = "127.0.1.1", *tenb_addr_str = "127.0.1.2";
  struct sockaddr_in senb_sockaddr = {}, sgw_sockaddr = {}, tenb_sockaddr = {};
  srsran::net_utils::set_sockaddr(&senb_sockaddr, senb_addr_str, GTPU_PORT);
  srsran::net_utils::set_sockaddr(&sgw_sockaddr, sgw_addr_str, GTPU_PORT);
  srsran::net_utils::set_sockaddr(&tenb_sockaddr, tenb_addr_str, GTPU_PORT);
  uint32_t tenb_addr = ntohl(tenb_sockaddr.sin_addr.s_addr);
  uint32_t senb_addr = ntohl(senb_sockaddr.sin_addr.s_addr);
  uint32_t sgw_addr  = ntohl(sgw_sockaddr.sin_addr.s_addr);

  srsran::unique_byte_buffer_t pdu;

  // Initiate layers
  srslog::basic_logger& logger1 = srslog::fetch_basic_logger("GTPU1");
  logger1.set_hex_dump_max_size(2048);
  srslog::basic_logger& logger2 = srslog::fetch_basic_logger("GTPU2");
  logger2.set_hex_dump_max_size(2048);
  srsran::task_scheduler task_sched;
  srsenb::gtpu           senb_gtpu(&task_sched, logger1), tenb_gtpu(&task_sched, logger2);
  stack_tester           senb_stack, tenb_stack;
  pdcp_tester            senb_pdcp, tenb_pdcp;
  senb_gtpu.init(senb_addr_str, sgw_addr_str, "", "", &senb_pdcp, &senb_stack, false);
  tenb_gtpu.init(tenb_addr_str, sgw_addr_str, "", "", &tenb_pdcp, &tenb_stack, false);

  // create tunnels MME-SeNB and MME-TeNB
  uint32_t senb_teid_in = senb_gtpu.add_bearer(rnti, drb1, sgw_addr, sgw_teidout1);
  uint32_t tenb_teid_in = tenb_gtpu.add_bearer(rnti2, drb1, sgw_addr, sgw_teidout2);

  // Buffer PDUs in SeNB PDCP
  for (size_t sn = 6; sn < 10; ++sn) {
    std::vector<uint8_t> data(10, sn);
    pdu = encode_ipv4_packet(data, senb_teid_in, sgw_sockaddr, senb_sockaddr);
    senb_pdcp.push_buffered_pdu(sn, std::move(pdu));
  }

  // create direct tunnel SeNB-TeNB
  gtpu::bearer_props props;
  props.flush_before_teidin_present = true;
  props.flush_before_teidin         = tenb_teid_in;
  uint32_t dl_tenb_teid_in          = tenb_gtpu.add_bearer(rnti2, drb1, senb_addr, 0, &props);
  props                             = {};
  props.forward_from_teidin_present = true;
  props.forward_from_teidin         = senb_teid_in;
  senb_gtpu.add_bearer(rnti, drb1, tenb_addr, dl_tenb_teid_in, &props);

  std::random_device   rd;
  std::mt19937         g(rd());
  std::vector<uint8_t> data_vec(10);
  std::iota(data_vec.begin(), data_vec.end(), 0);
  std::vector<uint8_t>  encoded_data;
  srsran::span<uint8_t> pdu_view{};

  // TEST: GTPU buffers incoming PDCP buffered SNs until the TEID is explicitly activated
  tenb_gtpu.handle_gtpu_s1u_rx_packet(read_socket(tenb_stack.s1u_fd), senb_sockaddr);
  TESTASSERT(tenb_pdcp.last_sdu == nullptr);
  tenb_gtpu.handle_gtpu_s1u_rx_packet(read_socket(tenb_stack.s1u_fd), senb_sockaddr);
  TESTASSERT(tenb_pdcp.last_sdu == nullptr);
  tenb_gtpu.set_tunnel_status(dl_tenb_teid_in, true);
  pdu_view = srsran::make_span(tenb_pdcp.last_sdu);
  TESTASSERT(std::count(pdu_view.begin() + PDU_HEADER_SIZE, pdu_view.end(), 7) == 10);
  TESTASSERT(tenb_pdcp.last_rnti == rnti2);
  TESTASSERT(tenb_pdcp.last_lcid == drb1);
  TESTASSERT(tenb_pdcp.last_pdcp_sn == (int)7);

  // TEST: verify that PDCP buffered SNs have been forwarded through SeNB->TeNB tunnel
  for (size_t sn = 8; sn < 10; ++sn) {
    tenb_gtpu.handle_gtpu_s1u_rx_packet(read_socket(tenb_stack.s1u_fd), senb_sockaddr);
    pdu_view = srsran::make_span(tenb_pdcp.last_sdu);
    TESTASSERT(std::count(pdu_view.begin() + PDU_HEADER_SIZE, pdu_view.end(), sn) == 10);
    TESTASSERT(tenb_pdcp.last_rnti == rnti2);
    TESTASSERT(tenb_pdcp.last_lcid == drb1);
    TESTASSERT(tenb_pdcp.last_pdcp_sn == (int)sn);
  }

  // TEST: verify that incoming DL data MME->SeNB is forwarded through SeNB->TeNB tunnel
  std::shuffle(data_vec.begin(), data_vec.end(), g);
  pdu = encode_gtpu_packet(data_vec, senb_teid_in, sgw_sockaddr, senb_sockaddr);
  encoded_data.assign(pdu->msg + 8u, pdu->msg + pdu->N_bytes);
  senb_gtpu.handle_gtpu_s1u_rx_packet(std::move(pdu), sgw_sockaddr);
  tenb_gtpu.handle_gtpu_s1u_rx_packet(read_socket(tenb_stack.s1u_fd), senb_sockaddr);
  pdu_view = srsran::make_span(tenb_pdcp.last_sdu);
  TESTASSERT(pdu_view.size() == encoded_data.size() and
             std::equal(pdu_view.begin(), pdu_view.end(), encoded_data.begin()));
  TESTASSERT(tenb_pdcp.last_rnti == rnti2 and tenb_pdcp.last_lcid == drb1);

  // TEST: verify that MME->TeNB packets are buffered until SeNB->TeNB tunnel is closed
  tenb_pdcp.clear();
  size_t N_pdus = std::uniform_int_distribution<size_t>{1, 30}(g);
  for (size_t i = 0; i < N_pdus; ++i) {
    std::fill(data_vec.begin(), data_vec.end(), i);
    pdu = encode_gtpu_packet(data_vec, senb_teid_in, sgw_sockaddr, tenb_sockaddr);
    tenb_gtpu.handle_gtpu_s1u_rx_packet(std::move(pdu), sgw_sockaddr);
    // The PDUs are being buffered
    TESTASSERT(tenb_pdcp.last_sdu == nullptr);
  }
  // PDUs coming from SeNB-TeNB tunnel are forwarded
  std::iota(data_vec.begin(), data_vec.end(), 0);
  std::shuffle(data_vec.begin(), data_vec.end(), g);
  pdu = encode_gtpu_packet(data_vec, senb_teid_in, sgw_sockaddr, senb_sockaddr);
  encoded_data.assign(pdu->msg + 8u, pdu->msg + pdu->N_bytes);
  senb_gtpu.handle_gtpu_s1u_rx_packet(std::move(pdu), sgw_sockaddr);
  tenb_gtpu.handle_gtpu_s1u_rx_packet(read_socket(tenb_stack.s1u_fd), senb_sockaddr);
  TESTASSERT(tenb_pdcp.last_sdu->N_bytes == encoded_data.size() and
             memcmp(tenb_pdcp.last_sdu->msg, encoded_data.data(), encoded_data.size()) == 0);
  tenb_pdcp.clear();
  // EndMarker is forwarded via MME->SeNB->TeNB, and TeNB buffered PDUs are flushed
  pdu = encode_end_marker(senb_teid_in);
  senb_gtpu.handle_gtpu_s1u_rx_packet(std::move(pdu), sgw_sockaddr);
  tenb_gtpu.handle_gtpu_s1u_rx_packet(read_socket(tenb_stack.s1u_fd), senb_sockaddr);
  srsran::span<uint8_t> encoded_data2{tenb_pdcp.last_sdu->msg + 20u, tenb_pdcp.last_sdu->msg + 30u};
  TESTASSERT(std::all_of(encoded_data2.begin(), encoded_data2.end(), [N_pdus](uint8_t b) { return b == N_pdus - 1; }));

  return SRSRAN_SUCCESS;
}

} // namespace srsenb

int main()
{
  // Setup logging.
  auto& logger = srslog::fetch_basic_logger("GTPU", false);
  logger.set_level(srslog::basic_levels::debug);
  logger.set_hex_dump_max_size(-1);

  // Start the log backend.
  srslog::init();

  TESTASSERT(srsenb::test_gtpu_direct_tunneling() == SRSRAN_SUCCESS);

  srslog::flush();

  srsran::console("Success");
}