#include <arpa/inet.h>
#include <assert.h>
#include <errno.h>
#include <netdb.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <unistd.h>
#include <iostream>

void Usage(char *progname);
void PrintOut(int fd, struct sockaddr *addr, size_t addrlen);

int main(int argc, char **argv) {
  // Expect the port number as a command line argument.
  if (argc != 2) {
    Usage(argv[0]);
  }

  // Populate the "hints" addrinfo structure for getaddrinfo().
  // ("man addrinfo")
  struct addrinfo hints;
  memset(&hints, 0, sizeof(struct addrinfo));
  hints.ai_family = AF_INET6;       // IPv6 (also handles IPv4 clients)
  hints.ai_socktype = SOCK_STREAM;  // stream
  hints.ai_flags = AI_PASSIVE;      // use wildcard "in6addr_any" address
  hints.ai_flags |= AI_V4MAPPED;    // use v4-mapped v6 if no v6 found
  hints.ai_protocol = IPPROTO_TCP;  // tcp protocol
  hints.ai_canonname = nullptr;
  hints.ai_addr = nullptr;
  hints.ai_next = nullptr;

  // Use argv[1] as the string representation of our portnumber to
  // pass in to getaddrinfo().  getaddrinfo() returns a list of
  // address structures via the output parameter "result".
  struct addrinfo *result;
  int res = getaddrinfo(nullptr, argv[1], &hints, &result);

  // Did addrinfo() fail?
  if (res != 0) {
    std::cerr << "getaddrinfo() failed: ";
    std::cerr << gai_strerror(res) << std::endl;
    return EXIT_FAILURE;
  }

  // Loop through the returned address structures until we are able
  // to create a socket and bind to one.  The address structures are
  // linked in a list through the "ai_next" field of result.
  int listen_fd = -1;
  for (struct addrinfo *rp = result; rp != nullptr; rp = rp->ai_next) {
    listen_fd = socket(rp->ai_family,
                       rp->ai_socktype,
                       rp->ai_protocol);
    if (listen_fd == -1) {
      // Creating this socket failed.  So, loop to the next returned
      // result and try again.
      std::cerr << "socket() failed: " << strerror(errno) << std::endl;
      listen_fd = 0;
      continue;
    }

    // Configure the socket; we're setting a socket "option."  In
    // particular, we set "SO_REUSEADDR", which tells the TCP stack
    // so make the port we bind to available again as soon as we
    // exit, rather than waiting for a few tens of seconds to recycle it.
    int optval = 1;
    setsockopt(listen_fd, SOL_SOCKET, SO_REUSEADDR,
               &optval, sizeof(optval));

    // Try binding the socket to the address and port number returned
    // by getaddrinfo().
    if (bind(listen_fd, rp->ai_addr, rp->ai_addrlen) == 0) {
      // Bind worked!  Print out the information about what
      // we bound to.
      PrintOut(listen_fd, rp->ai_addr, rp->ai_addrlen);
      break;
    }

    // The bind failed.  Close the socket, then loop back around and
    // try the next address/port returned by getaddrinfo().
    close(listen_fd);
    listen_fd = -1;
  }

  // Free the structure returned by getaddrinfo().
  freeaddrinfo(result);

  // Did we succeed in binding to any addresses?
  if (listen_fd == -1) {
    // No.  Quit with failure.
    std::cerr << "Couldn't bind to any addresses." << std::endl;
    return EXIT_FAILURE;
  }

  // Success. Tell the OS that we want this to be a listening socket.
  if (listen(listen_fd, SOMAXCONN) != 0) {
    std::cerr << "Failed to mark socket as listening: ";
    std::cerr << strerror(errno) << std::endl;
    close(listen_fd);
    return EXIT_FAILURE;
  }

  // Sleep for 20 seconds, then close house.
  sleep(20);
  close(listen_fd);
  return EXIT_SUCCESS;
}

void Usage(char *progname) {
  std::cerr << "usage: " << progname << " port" << std::endl;
  exit(EXIT_FAILURE);
}

void PrintOut(int fd, struct sockaddr *addr, size_t addrlen) {
  std::cout << "Socket [" << fd << "] is bound to:" << std::endl;
  if (addr->sa_family == AF_INET) {
    // Print out the IPV4 address and port

    char astring[INET_ADDRSTRLEN];
    struct sockaddr_in *in4 = reinterpret_cast<struct sockaddr_in *>(addr);
    inet_ntop(AF_INET, &(in4->sin_addr), astring, INET_ADDRSTRLEN);
    std::cout << " IPv4 address " << astring;
    std::cout << " and port " << ntohs(in4->sin_port) << std::endl;

  } else if (addr->sa_family == AF_INET6) {
    // Print out the IPV6 address and port

    char astring[INET6_ADDRSTRLEN];
    struct sockaddr_in6 *in6 = reinterpret_cast<struct sockaddr_in6 *>(addr);
    inet_ntop(AF_INET6, &(in6->sin6_addr), astring, INET6_ADDRSTRLEN);
    std::cout << " IPv6 address " << astring;
    std::cout << " and port " << ntohs(in6->sin6_port) << std::endl;

  } else {
    std::cout << " ???? address and port ????" << std::endl;
  }
}