// uses socket demo code from https://beej.us/guide/bgnet/html/single/bgnet.html
// and getstdin() uses getLine() from https://stackoverflow.com/questions/4023895/

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <errno.h>
#include <string.h>
#include <netdb.h>
#include <sys/types.h>
#include <netinet/in.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <sys/select.h>

#define MAXDATASIZE 513 // max number of bytes we can get at once (RFC2812 says 512, plus one for null terminator)
#define STDIN 0 // stdin is fd 0
#define BACKLOG 10 // maximum length to which the queue of pending connections for sockfd may grow

#define BOUNCERLISTENPORT "1234" // TODO: change this to a config option!

// getstdin() return codes
#define OK       0
#define NO_INPUT 1
#define TOO_LONG 2

// Get stdin line with buffer overrun protection
static int getstdin(char *prompt, char *buff, size_t sz) {
  int ch, extra;

  // Print optional prompt
  if (prompt != NULL) {
    printf ("%s", prompt);
    fflush (stdout);
  }

  // Get the intput from stdin
  if (fgets (buff, sz, stdin) == NULL) {
    return NO_INPUT;
  }

  // If it was too long, there'll be no newline. In that case, we flush
  // to end of line so that excess doesn't affect the next call.
  if (buff[strlen(buff) - 1] != '\n') { // strlen of the actually entered line, not the original array size
    extra = 0;
    while (((ch = getchar()) != '\n') && (ch != EOF)) {
      extra = 1;
    }
    return (extra == 1) ? TOO_LONG : OK;
  }

  // Otherwise remove newline and give string back to caller.
  buff[strlen(buff) - 1] = '\0';
  return OK;
}

// Append CR-LF to the end of a string
void appendcrlf(char *string) {
  // Make sure it doesn't already end with CR or LF
  while (string[strlen(string) - 1] == '\r' || string[strlen(string) - 1] == '\r') {
    string[strlen(string) - 1] = '\0';
  }

  int startlen = strlen(string);
  string[startlen] = '\r';
  string[startlen + 1] = '\n';
  string[startlen + 2] = '\0';
}

// get sockaddr, IPv4 or IPv6:
void *get_in_addr(struct sockaddr *sa) {
  if (sa->sa_family == AF_INET) {
    return &(((struct sockaddr_in*)sa)->sin_addr);
  }

  return &(((struct sockaddr_in6*)sa)->sin6_addr);
}

int createserversocket(char *host, char *port) {
  int sockfd;
  struct addrinfo hints, *servinfo, *p;
  int rv;// return value for getaddrinfo (for error message)
  char s[INET6_ADDRSTRLEN];

  memset(&hints, 0, sizeof hints);
  hints.ai_family = AF_UNSPEC;
  hints.ai_socktype = SOCK_STREAM;

  if ((rv = getaddrinfo(host, port, &hints, &servinfo)) != 0) {
    fprintf(stderr, "getaddrinfo: %s\n", gai_strerror(rv));
    return 1;
  }

  // loop through all the results and connect to the first we can
  for (p = servinfo; p != NULL; p = p->ai_next) {
    if ((sockfd = socket(p->ai_family, p->ai_socktype, p->ai_protocol)) == -1) {
      perror("bouncer-server: socket");
      continue;
    }

    if (connect(sockfd, p->ai_addr, p->ai_addrlen) == -1) {
      close(sockfd);
      perror("bouncer-server: connect");
      continue;
    }

    break;
  }

  if (p == NULL) {
    fprintf(stderr, "bouncer-server: failed to connect\n");
    return 2;
  }

  inet_ntop(p->ai_family, get_in_addr((struct sockaddr *)p->ai_addr), s, sizeof s);
  printf("bouncer-server: connecting to %s\n", s);

  freeaddrinfo(servinfo); // all done with this structure

  return sockfd;
}

int createclientsocket(char *listenport) {
  listenport = BOUNCERLISTENPORT;

  int listener;     // listening socket descriptor

  int rv; // return value for getaddrinfo (for error message)

	struct addrinfo hints, *ai, *p;

	// get us a socket and bind it
	memset(&hints, 0, sizeof hints);
	hints.ai_family = AF_UNSPEC;
	hints.ai_socktype = SOCK_STREAM;
	hints.ai_flags = AI_PASSIVE;

	if ((rv = getaddrinfo(NULL, listenport, &hints, &ai)) != 0) {
		fprintf(stderr, "selectserver: %s\n", gai_strerror(rv));
		exit(1);
	}

  // Try for IPv6
	for (p = ai; p != NULL; p = p->ai_next) {
    if (p->ai_family == AF_INET6) {
      listener = socket(p->ai_family, p->ai_socktype, p->ai_protocol);
      if (listener != -1) {
        // success, got IPv6!
        printf("success, got IPv6!  ai_family: %d\n", p->ai_family);
        break;
      }
    }
  }

  // Try for IPv4 if IPv6 failed
  if (listener < 0) {
    for (p = ai; p != NULL; p = p->ai_next) {
      if (p->ai_family == AF_INET) {
        listener = socket(p->ai_family, p->ai_socktype, p->ai_protocol);
        if (listener != -1) {
          // moderate success, got IPv4!
          printf("moderate success, got IPv4!  ai_family: %d\n", p->ai_family);
          break;
        }
      }
    }
  }

  if (bind(listener, p->ai_addr, p->ai_addrlen) < 0) {
    // failed to bind
    close(listener);
    printf("bouncer-client: failed to bind, exiting...\n");
    exit(1);
  }

	// if we got here, it means we didn't get bound
	if (p == NULL) {
		fprintf(stderr, "selectserver: failed to bind\n");
		exit(2);
	}

	freeaddrinfo(ai); // all done with this

    // listen
    if (listen(listener, BACKLOG) == -1) {
        perror("listen");
        exit(1);
    }

  return listener;
}

void dochat(int *serversockfd, int *clientsockfd) {
  char serverbuf[MAXDATASIZE];
  int numbytes; // Number of bytes received from remote server
  char outgoingmsg[MAXDATASIZE]; // String to send to server
  int outgoingmsgrc; // Return code from getstdin() for outgoing message

  fd_set rfds;

  while (1) {
    FD_ZERO(&rfds); // clear entries from fd set

    FD_SET(STDIN, &rfds); // add STDIN (fd 0) to read fds to monitor
    FD_SET(*serversockfd, &rfds); // add our network socket to monitor

    // TODO - Change this to use number of fds + 1 instead of sockfd + 1 (I don't think they will be the same with multiple sockets/connections)
    if (select(*serversockfd + 1, &rfds, NULL, NULL, NULL) < 0) { // network socket + 1, rfds, no writes, no exceptions/errors, no timeout
      printf("receive error, exiting!?\n");
      perror("select");
      // TODO exit here?  let's try it.
      exit(1);
    }

    if (FD_ISSET(*serversockfd, &rfds)) {
      printf("reading socket!\n");

      if ((numbytes = recv(*serversockfd, serverbuf, MAXDATASIZE - 1, 0)) == -1) {
        printf("receive error (-1), exiting...\n");
        perror("recv");
        exit(1);
      } else if (numbytes == 0) {
        printf("socket closed (or no data received) (0), exiting...\n");
        perror("recv");
        exit(1);
      }
      serverbuf[numbytes] = '\0';

      printf("RECEIVED: %s\n", serverbuf);
    }

    if (FD_ISSET(STDIN, &rfds)) {
      printf("reading stdin!\n");

      outgoingmsgrc = getstdin(NULL, outgoingmsg, sizeof(outgoingmsg));

      if (outgoingmsgrc == NO_INPUT) {
        printf("\nError!  No input.\n");
      } else if (outgoingmsgrc == TOO_LONG) {
        printf ("Error!  Too long.  Would have allowed up to: [%s]\n", outgoingmsg);
      }

      appendcrlf(outgoingmsg);

      if (send(*serversockfd, outgoingmsg, strlen(outgoingmsg), 0) == -1) {
        printf("send error, exiting...\n");
        perror("send");
      }
    }
  }
}

int main(int argc, char *argv[]) {
  if (argc != 3) {
    fprintf(stderr,"usage: %s [hostname] [port]\n", argv[0]);
    exit(1);
  }

  // TODO: see if any of this can be shared (i.e. 1. avoid code duplication, and 2. see if variables can be shared between client/server sockets)

  // TODO: track fdmax

  // I will try to keep to the notation of "server" meaning the real IRCd, "bouncer" meaning the bouncer, and "client" meaning the real IRC client

  // BOUNCER-TO-SERVER socket things

  int serversockfd = createserversocket(argv[1], argv[2]);
  int clientsockfd = createclientsocket(BOUNCERLISTENPORT);

  dochat(&serversockfd, &clientsockfd);

  printf("dochat() complete, closing socket...\n");

  close(serversockfd);

  return 0;
}