#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <stddef.h>

#include <fcntl.h>
#include <arpa/inet.h>
#include <linux/if_packet.h>

#include "ip4.h"
#include "udp4.h"
#include "dhcp4.h"
#include "eth.h"
#include "packet.h"
#include "interface.h"
#include "sock.h"

int main()
{

  int sock = sock::create(67);

  char const * interface_name = "enp175s0";
  int ifa_index = sock::interface_index(sock, interface_name);
  sock::bind_interface(sock, ifa_index);

  uint8_t eth_source_address[6];
  sock::interface_address(sock, interface_name, eth_source_address);

  packet::packet p{};
  dhcp4::options options{};
  static uint8_t recvbuf[65536];
  static uint8_t sendbuf[16384];

  uint32_t ip4_client_address = ip4::fromstr("10.0.0.50");
  uint32_t ip4_server_address = ip4::fromstr("10.0.0.5");
  uint32_t ip4_subnet_mask = ip4::fromstr("255.255.255.0");
  uint32_t ip4_router = ip4::fromstr("10.0.0.5");
  uint32_t ip4_domain_name_server = ip4::fromstr("8.8.8.8");

  while (true) {
    //////////////////////////////////////////////////////////////////////
    // dhcp recv
    //////////////////////////////////////////////////////////////////////
    {
      struct sockaddr_ll recv_address;
      int flags = 0;
      socklen_t socklen = (sizeof (struct sockaddr_ll));
      ssize_t rret = recvfrom(sock, recvbuf, (sizeof (recvbuf)), flags,
                              (struct sockaddr *)&recv_address, &socklen);
      if (rret < 0) {
        perror("recvfrom");
        exit(EXIT_FAILURE);
      }

      packet::parse(recvbuf, rret, &p);
      int dhcp4_options_length = rret - (packet::dhcp4_offset + (offsetof (dhcp4::message, options)));
      dhcp4::parse_options(p.dhcp4, dhcp4_options_length, &options);

      printf("dhcp4 op: %d\n", p.dhcp4->op);
      printf("message type: %s\n", dhcp4::message_type_tostr(options.message_type));
      printf("transaction id: %08x\n", ntohl(p.dhcp4->xid));
    }

    if (options.message_type == dhcp4::message_type::dhcpdiscover) {
      dhcp4::message_parameters params = {
        .your_ip_address = ip4_client_address,
        .next_server_ip_address = ip4_server_address,
        .server_identifier = ip4_server_address,
        .subnet_mask = ip4_subnet_mask,
        .router = ip4_router,
        .domain_name_server = ip4_domain_name_server,
      };

      uint8_t const * eth_destination_address = p.eth->source_address;
      uint32_t ip4_source_address = ip4_server_address;
      uint32_t ip4_destination_address = ip4_client_address;
      uint32_t dhcp_transaction_id = ntohl(p.dhcp4->xid);
      int length = packet::make(sendbuf,
                                dhcp4::op::bootreply,
                                eth_source_address,
                                eth_destination_address,
                                eth_destination_address, // eth_client_address
                                ip4_source_address,
                                ip4_destination_address,
                                67,
                                68,
                                dhcp_transaction_id,
                                dhcp4::message_type::dhcpoffer,
                                &params);

      sock::send(sock, ifa_index, sendbuf, length, eth_destination_address);
    }
    if (options.message_type == dhcp4::message_type::dhcprequest) {
      printf("requested ip address: %s\n", ip4::tostr(options.requested_ip_address));
      if (options.requested_ip_address != ip4_client_address) {
        printf("should NAK\n");
        continue;
      }

      dhcp4::message_parameters params = {
        .your_ip_address = ip4_client_address,
        .next_server_ip_address = ip4_server_address,
        .server_identifier = ip4_server_address,
        .subnet_mask = ip4_subnet_mask,
        .router = ip4_router,
        .domain_name_server = ip4_domain_name_server,
      };

      uint8_t const * eth_destination_address = p.eth->source_address;
      uint32_t ip4_source_address = ip4_server_address;
      uint32_t ip4_destination_address = ip4_client_address;
      uint32_t dhcp_transaction_id = ntohl(p.dhcp4->xid);
      int length = packet::make(sendbuf,
                                dhcp4::op::bootreply,
                                eth_source_address,
                                eth_destination_address,
                                eth_destination_address, // eth_client_address
                                ip4_source_address,
                                ip4_destination_address,
                                67,
                                68,
                                dhcp_transaction_id,
                                dhcp4::message_type::dhcpack,
                                &params);

      sock::send(sock, ifa_index, sendbuf, length, eth_destination_address);
    }
  }
}