/*
 * ptyhelper: a utility that runs a command in a pseudoterm and then streams
 * stdio to/from it.  Intended to get around the node.js loss of C/UNIX 
 * functionality.
 * Remember to compile with -lutil.
 */
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <signal.h>
#include <pty.h>
#include <utmp.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <sys/select.h>
#include <termios.h>

int got_sighup = 0;

void handle_HUP(int signum) {
  if (signum == SIGHUP)
    got_sighup = 1;
  return;
}

int main(int argc, char *argv[]) {

  int ptymaster, ptyslave; /* File descriptors */
  int child;
  int status, selstatus;
  int w = 80, h = 24, t;
  struct sigaction sighup_act;
  fd_set readset;
  struct timeval select_time;
  char buf[4096];
  int nread;
  char *penv, *ptmp;
#if 0
  struct termios ptysettings;
#endif
  struct winsize ptysize;

  if (argc == 1) {
    fprintf(stderr, "No command given.\n");
    exit(1);
  }

  /* Set up the signal handler. */
  sighup_act.sa_handler = &handle_HUP;
  sighup_act.sa_flags = SA_RESTART;
  sigaction(SIGHUP, &sighup_act, NULL);

  /* Check the environment for configuration options. */
  penv = getenv("PTYHELPER");
  if (penv != NULL) {
    t = strtol(penv, &ptmp, 10);
    if (t > 0 && t < 256)
      h = t;
    if (*ptmp != '\0') {
      penv = ptmp + 1;
      t = strtol(penv, &ptmp, 10);
      if (t > 0 && t < 256)
        w = t;
    }
  }
  /* Set up the size. */
  ptysize.ws_row = h;
  ptysize.ws_col = w;

  /* Open a pty */
  if (openpty(&ptymaster, &ptyslave, NULL, NULL, &ptysize)) {
    return 1;
  }
#if 0
  /* Put it into raw mode. */
  tcgetattr(ptyslave, &ptysettings);
  cfmakeraw(&ptysettings);
  tcsetattr(ptyslave, TCSANOW, &ptysettings);
#endif

  /* Start the child */
  /* forkpty() might be more convenient. */
  if (!(child = fork())) {
    /* Child process */
    login_tty(ptyslave);
    close(ptymaster);
    execvp(argv[1], argv + 1);
    perror("execvp() failed");
    return 1;
  }
  close(ptyslave);

  while (1) {
    /* Now do a select() over stdin and ptymaster, and write anything that 
     * appears to ptymaster and stdout respectively. */
    FD_ZERO(&readset);
    FD_SET(0, &readset);
    FD_SET(ptymaster, &readset);
    select_time.tv_sec = 1;
    select_time.tv_usec = 0;
    selstatus = select(ptymaster + 1, &readset, NULL, NULL, &select_time);
    if (selstatus > 0) {
      /* TODO make sure it all gets written if a signal interrupts write(). */
      if (FD_ISSET(0, &readset)) {
        nread = read(0, buf, 4096);
        if (nread > 0) {
          write(ptymaster, buf, nread);
        }
      }
      if (FD_ISSET(ptymaster, &readset)) {
        nread = read(ptymaster, buf, 4096);
        if (nread > 0) {
          write(1, buf, nread);
        }
      }
    }

    /* Periodically check to see if we're done. */
    /* TODO: catch SIGCHLD and only wait() if it is delivered. */
    if (waitpid(child, &status, WNOHANG)) {
      break;
    }

    /* If node sighup's us, pass it along. */
    if (got_sighup) {
      kill(child, SIGHUP);
    }
  }

  /* Get any leftover output and clean up. */
  /* FIXME looping over select() is pointless if there's only one fd that
   * nothing's writing to.  Just loop over read() until it's empty. */
  while (1) {
    FD_ZERO(&readset);
    FD_SET(ptymaster, &readset);
    select_time.tv_sec = 0;
    select_time.tv_usec = 0;
    if (select(ptymaster + 1, &readset, NULL, NULL, &select_time) > 0) {
      nread = read(ptymaster, buf, 4096);
      if (nread > 0) {
        write(1, buf, nread);
      }
      else
        break;
    }
    else
      break;
  }
  close(ptymaster);

  /* Return the child's exit status. */
  if (WIFEXITED(status))
    return WEXITSTATUS(status);
  return 0;
}