/* Copyright status: this file is in the public domain. */

#include <stdio.h>
#include <fcntl.h>
#include <errno.h>
#include <stdlib.h>
#include <unistd.h>
#include <termios.h>
#include <strings.h>
#include <sys/wait.h>
#include <sys/ioctl.h>
#include <sys/socket.h>
#include <sys/ttydefaults.h>

extern const char *__progname;

#include "ptyimpl.h"

static int ptypair(int *mfdp, int *sfdp, char **spathp)
{
 int i;
 int mfd;
 int sfd;
 int tfd;
 char ptyname[16];
 struct termios tio;
 struct termios tty_tio;

 tfd = open("/dev/tty",O_RDONLY,0);
 for (i=0;;i++)
  { sprintf(&ptyname[0],"/dev/pty%c%x",'p'+(i/16),i%16);
    mfd = open(&ptyname[0],O_RDWR,0);
    if (mfd < 0)
     { int e;
       e = errno;
       if (e == ENOENT)
	{ close(tfd);
	  errno = e;
	  return(-1);
	}
       continue;
     }
    ptyname[5] = 't'; /* sprintf(&ptyname[0],"/dev/tty%c%x",'p'+(i/16),i%16); */
    sfd = open(&ptyname[0],O_RDWR,0);
    if (sfd < 0)
     { close(mfd);
       continue;
     }
    if (tcgetattr(sfd,&tio) < 0)
     { close(mfd);
       close(sfd);
       continue;
     }
    tio.c_iflag = ICRNL | IXON | IXANY | IMAXBEL;
    tio.c_oflag = OPOST | ONLCR;
    tio.c_cflag = (tio.c_cflag & (CSIZE|CSTOPB|PARENB|PARODD)) | CREAD | HUPCL;
    tio.c_lflag = ICANON | ISIG | IEXTEN | ECHO | ECHOE | ECHOKE | ECHOCTL;
    tio.c_cc[VEOF] = CEOF;
    tio.c_cc[VEOL] = CEOL;
    tio.c_cc[VERASE] = CERASE;
    tio.c_cc[VINTR] = CINTR;
    tio.c_cc[VSTATUS] = CSTATUS;
    tio.c_cc[VKILL] = CKILL;
    tio.c_cc[VQUIT] = CQUIT;
    tio.c_cc[VSUSP] = CSUSP;
    tio.c_cc[VDSUSP] = CDSUSP;
    tio.c_cc[VSTART] = CSTART;
    tio.c_cc[VSTOP] = CSTOP;
    tio.c_cc[VLNEXT] = CLNEXT;
    tio.c_cc[VDISCARD] = CDISCARD;
    tio.c_cc[VWERASE] = CWERASE;
    tio.c_cc[VREPRINT] = CREPRINT;
    if (tfd >= 0)
     { if (tcgetattr(tfd,&tty_tio) == 0)
	{ for (i=(sizeof(tio.c_cc)/sizeof(tio.c_cc[0]))-1;i>=0;i--) tio.c_cc[i] = tty_tio.c_cc[i];
	}
       close(tfd);
     }
    tio.c_cc[VMIN] = CMIN;
    tio.c_cc[VTIME] = CTIME;
    tcsetattr(sfd,TCSANOW|TCSASOFT,&tio);
    *mfdp = mfd;
    *sfdp = sfd;
    *spathp = strdup(&ptyname[0]);
    return(0);
  }
}

void ptypair_setup(int *mfdp, int *sfdp, char **spathp, char **errp)
{
 char *spath;

 if (ptypair(mfdp,sfdp,&spath) < 0)
  { *errp = strdup("no pty pairs available");
    return;
  }
 if (spathp) *spathp = spath; else free(spath);
 *errp = 0;
}

void ptyexport_setup(const char *prog, int *ptymp, int *ptysp, char **errp)
{
 int mfd;
 int sfd;
 char *spath;
 pid_t kid;
 int xp[2];
 int e;
 int r;
 pid_t wk;
 int ws;

 if (ptypair(&mfd,&sfd,&spath) < 0)
  { *errp = strdup("no pty pairs available");
    return;
  }
 do
  { if (socketpair(AF_LOCAL,SOCK_STREAM,0,&xp[0]) < 0)
     { asprintf(errp,"socketpair: %s",strerror(errno));
       break;
     }
    do <"err">
     { fflush(0);
       kid = fork();
       if (kid < 0)
	{ asprintf(errp,"fork: %s",strerror(errno));
	  break;
	}
       if (kid == 0)
	{ close(xp[0]);
	  fcntl(xp[1],F_SETFD,1);
	  execlp(prog,prog,"up",spath,(char *)0);
	  e = errno;
	  send(xp[1],&e,sizeof(int),0);
	  _exit(0);
	}
       close(xp[1]);
       xp[1] = -1;
       r = recv(xp[0],&e,sizeof(int),MSG_WAITALL);
       if (r < 0)
	{ asprintf(errp,"exec pipe recv: %s",strerror(errno));
	  break;
	}
       if (r == sizeof(int))
	{ asprintf(errp,"exec: %s",strerror(e));
	  break;
	}
       if (r != 0)
	{ asprintf(errp,"exec protocol error (wanted %d, got %d)",(int)sizeof(int),r);
	  break;
	}
       close(xp[0]);
       xp[0] = -1;
       while (1)
	{ wk = waitpid(kid,&ws,0);
	  if (wk < 0)
	   { asprintf(errp,"exec protocol wait: %s",strerror(errno));
	     break <"err">;
	   }
	  if (wk == 0)
	   { *errp = strdup("exec protocol lost child");
	     break <"err">;
	   }
	  if (wk == kid) break;
	}
       if (WIFEXITED(ws))
	{ if (WEXITSTATUS(ws) == 0)
	   { *ptymp = mfd;
	     *ptysp = sfd;
	     *errp = 0;
	     return;
	   }
	  asprintf(errp,"%s: exit %d",prog,WEXITSTATUS(ws));
	}
       else if (WIFSIGNALED(ws))
	{ asprintf(errp,"%s: signal %d%s",prog,WTERMSIG(ws),WCOREDUMP(ws)?" (core dumped)":"");
	}
       else if (WIFSTOPPED(ws))
	{ asprintf(errp,"%s: stopped on signal %d",prog,WSTOPSIG(ws));
	}
       else
	{ asprintf(errp,"%s: mystery exit status %#x",prog,ws);
	}
     } while (0);
    if (xp[0] >= 0) close(xp[0]);
    if (xp[1] >= 0) close(xp[1]);
  } while (0);
 close(sfd);
 close(mfd);
}

void pty_ctty(int sfd)
{
 setsid();
 ioctl(sfd,TIOCSCTTY,0);
}