// simirid.c -- simulate iridium delays between two serial ports

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

# include <sys/time.h>  // for timeval
# include <time.h>      // for timeval, gettimeofday
# include <ctype.h>     // for isprint()
# include <sys/stat.h>  // to check if pid is running
# include <termio.h>    // for settty() gettty() args
# include <fcntl.h>     // for open() args
# include <sys/types.h>

double now(void)
{
	struct timeval tv;
	struct timezone tz;

	static time_t s0 = 0;

	gettimeofday(&tv,&tz);

	if(s0 == 0)
		s0 = tv.tv_sec;

	return (double)(tv.tv_sec - s0) + (double)(tv.tv_usec) * 1.0e-6;
}

void sleep_us(long us)
{
	struct timeval timeout;
	if(us <= 0)
		return;
	timeout.tv_sec  = us/1000000L;
	timeout.tv_usec = us%1000000L;
	select(1, NULL, NULL, NULL, &timeout);
	return;
}

int opentty(char *tty, long baud)
{
	static struct termios settty;
	int ret;
	int baudflag;
	int fdtty;
	char ttydev[100];

	// open first with no delay in order to change the bits to ignore
	// handshaking lines, then open again for real.

	sprintf(ttydev,"/dev/%s",tty);

	if((fdtty=open(ttydev,O_RDWR | O_NDELAY))<0){
		perror("first serial port open failed");
		fprintf(stderr,"ttydev=\"%s\"\n",ttydev);
		return -1;
	}

	if     (baud == 110) baudflag = B110;
	else if(baud == 300) baudflag = B300;
	else if(baud == 600) baudflag = B600;
	else if(baud == 1200) baudflag = B1200;
	else if(baud == 2400) baudflag = B2400;
	else if(baud == 4800) baudflag = B4800;
	else if(baud == 9600) baudflag = B9600;
	else if(baud == 19200) baudflag = B19200;
	else if(baud == 38400) baudflag = B38400;
	else if(baud == 57600) baudflag = B57600;
	else if(baud == 115200) baudflag = B115200;
	else if(baud == 230400) baudflag = B230400;
	else if(baud == 460800) baudflag = B460800;
	else{
		fprintf(stderr,"opentty(): bad baudrate=%ld\n",baud);
		return -2;
	}

# if 0
	if((tcgetattr(fdtty, &settty)) < 0){
		perror("tcgetattr() serial port failed");
		fprintf(stderr,"ttydev=\"%s\" fdtty=%d\n",ttydev,fdtty);
		return -6;
	}
# endif

	settty.c_iflag = 0;
	settty.c_oflag = 0;
	settty.c_cflag = 0;
	settty.c_lflag = 0;
	cfmakeraw(&settty);
	settty.c_cflag |= CLOCAL;		// ignore modem control lines
	settty.c_cflag &= ~CRTSCTS;   // no flow control
	settty.c_cflag |= CREAD;		// added June 21, 2002 per new tty driver
	cfsetispeed(&settty,baudflag);
	cfsetospeed(&settty,baudflag);

	ret=tcsetattr(fdtty,TCSANOW,&settty);
	if(ret<0){
		perror("tcsetattr() serial port failed");
		fprintf(stderr,"ttydev=\"%s\"\n",ttydev);
		return -3;
	}

# if 0
	if(close(fdtty) < 0){
		perror("error: close() serial port open failed");
		fprintf(stderr,"ttydev=\"%s\"\n",ttydev);
		return -4;
	}

	if((fdtty=open(ttydev,O_RDWR)) < 0){
		perror("second serial port open failed");
		fprintf(stderr,"ttydev=\"%s\"\n",ttydev);
		return -5;
	}
# endif

	return fdtty;
}

int main(int argc, char** argv)
{
	# define MBUF 10000
	char buf1[MBUF], buf2[MBUF];
	double time1[MBUF],time2[MBUF];
	int head1=0, tail1=0;
	int head2=0, tail2=0;
	unsigned char kar, kar1, kar2;
	int seq1,seq2;
	int n1 = 0, n2 = 0;

	char *ttydev1; // leafname of tty device
	char *ttydev2; // leafname of tty device
	long baud;     // baudrate in both directions
	double delay_min;  // minimum seconds of one-way path delay
	double delay_max;  // maximum seconds of one-way path delay
	double delay;
	long usbc;     // microseconds between characters

	char tmp[100];
	pid_t pid;
	FILE *fplock2;
	FILE *fplock1;
	char lockfile1[100];
	char lockfile2[100];
	int fdtty1;
	int fdtty2;
	int selret;
	double error_rate;
	long error_thresh;

	if(argc != 8){
		fprintf(stderr,"usage: simirid tty1 tty2 baud delay_min delay_max "
			"usbc error_rate\n");
		exit(1);
	}

	ttydev1 = *++argv;
	ttydev2 = *++argv;
	baud    = atol(*++argv);
	delay_min   = atof(*++argv);
	delay_max   = atof(*++argv);
	usbc    = atol(*++argv);
	error_rate  = atof(*++argv);

	error_thresh = (double)RAND_MAX * error_rate;

	sprintf(lockfile1,"/var/lock/LCK..%s",ttydev1);
	if((fplock1 = fopen(lockfile1,"r"))!=NULL){
		struct stat statbuf;
//		fprintf(stderr,"lock file found: %s\n",lockfile1);
		fscanf(fplock1,"%10d\n",&pid);
		fclose(fplock1);
		sprintf(tmp,"/proc/%d",pid);
//		fprintf(stderr,"checking process %s\n",tmp);
		if(stat(tmp,&statbuf) == -1){
//			fprintf(stderr,"it is not running\n");
			if(unlink(lockfile1) == -1){
				perror("cannot remove lockfile1");
				fprintf(stderr,"lockfile1=%s\n",lockfile1);
				exit(1);
			}
			fprintf(stderr,"removed stale lockfile1=%s\n",lockfile1);
		}
		else{
			fprintf(stderr,"lockfile1=%s indicates processs %d is using %s\n",
					lockfile1,pid,ttydev1);
			fprintf(stderr,"exiting\n");
			exit(1);
		}
	}

	sprintf(lockfile2,"/var/lock/LCK..%s",ttydev2);
	if((fplock2 = fopen(lockfile2,"r"))!=NULL){
		struct stat statbuf;
//		fprintf(stderr,"lock file found: %s\n",lockfile2);
		fscanf(fplock2,"%10d\n",&pid);
		fclose(fplock2);
		sprintf(tmp,"/proc/%d",pid);
//		fprintf(stderr,"checking process %s\n",tmp);
		if(stat(tmp,&statbuf) == -1){
//			fprintf(stderr,"it is not running\n");
			if(unlink(lockfile2) == -1){
				perror("cannot remove lockfile2 2");
				fprintf(stderr,"lockfile2 %s\n",lockfile2);
				exit(1);
			}
			fprintf(stderr,"removed stale lockfile2 %s\n",lockfile2);
		}
		else{
			fprintf(stderr,"lockfile2 %s indicates processs %d is using %s\n",
					lockfile2,pid,ttydev2);
			fprintf(stderr,"exiting\n");
			exit(1);
		}
	}

	if((fdtty1 = opentty(ttydev1, baud)) < 0){
		fprintf(stderr,"opentty failed ");
		fprintf(stderr,"ttydev1=%s fdtty1=%d\n",ttydev1,fdtty1);
		unlink(lockfile1);
		exit(1);
	}

	if((fdtty2 = opentty(ttydev2, baud)) < 0){
		fprintf(stderr,"opentty failed ");
		fprintf(stderr,"ttydev2=%s fdtty2=%d\n",ttydev2,fdtty2);
		unlink(lockfile1);
		unlink(lockfile2);
		exit(1);
	}

	while(1){
		int nfds;
		fd_set readfds;
		struct timeval timeout;

		if(fdtty1 > fdtty2) nfds = fdtty1 + 1;
		else                nfds = fdtty2 + 1;

		FD_ZERO(&readfds);
		FD_SET(fdtty1,&readfds);
		FD_SET(fdtty2,&readfds);

		timeout.tv_sec  = 0;
		timeout.tv_usec = 1000L;   // 1 ms timeout

		selret = select(nfds, &readfds, NULL, NULL, &timeout);

		if(selret < 0){
			perror("select failed");
			fprintf(stderr,"  selret=%d\n",selret);
			goto cleanupandexit;
		}

		if(selret > 0){  // something's available

			// this sleep_us simulates slow bit rate over RF link
			// by causing time1 and time2 to be increased in order
			// to delay output
			sleep_us(usbc);

			if(FD_ISSET(fdtty1,&readfds)){
				if(read(fdtty1, (char*)(&kar), 1) != 1){
					perror("read fdtty1 failed");
					goto cleanupandexit;
				}
				if(0 && kar == 0xFF){
					perror("fdtty1 read 0xFF character -- cannot use with telnet\n");
					goto cleanupandexit;
				}
				if((long)(rand()) < error_thresh)
					kar = rand() & 0xFF;
				buf1[head1] = kar;
				delay = delay_min +
					(delay_max - delay_min) * (double)rand() / (double)(RAND_MAX);
				time1[head1] = now() + delay;
				head1++; if(head1 >= MBUF) head1=0;
			}

			if(FD_ISSET(fdtty2,&readfds)){
				if(read(fdtty2, (char*)(&kar), 1) != 1){
					perror("read fdtty2 failed");
					goto cleanupandexit;
				}
				if(0 && kar == 0xFF){
					perror("fdtty1 read 0xFF character -- cannot use with telnet\n");
					goto cleanupandexit;
				}
				if((long)(rand()) < error_thresh)
					kar = rand() & 0xFF;
				buf2[head2] = kar;
				delay = delay_min +
					(delay_max - delay_min) * (double)rand() / (double)(RAND_MAX);
				time2[head2] = now() + delay;
				head2++; if(head2 >= MBUF) head2=0;
			}
		}

		// the following is executed every input character or select timeout

		if(head1 != tail1 && now() > time1[tail1]){
			kar = buf1[tail1];
			tail1++; if(tail1 >= MBUF) tail1=0;

			n1++;
			if(n1 == 2) seq1=kar-32;
			if(n1 == 3){
				if(kar!='Y' && kar!='N') fprintf(stderr,"\n");
				fprintf(stderr,"h1: %2d-%c ",seq1,kar);
				kar1=kar;
			}
			if(kar == 0x01) n1=0;
			if(kar == 0x0d){
//				fprintf(stderr,"h1: %2d-%c ",seq1,kar1);
				fprintf(stderr,"n1: %4d ",n1);
			}

			if(write(fdtty2,&kar,1) != 1){
				perror("write fdtty2 failed");
				goto cleanupandexit;
			}
		}

		if(head2 != tail2 && now() > time2[tail2]){
			kar = buf2[tail2];
			tail2++; if(tail2 >= MBUF) tail2=0;

			n2++;
			if(n2 == 2) seq2=kar-32;
			if(n2 == 3){
				if(kar!='Y' && kar!='N') fprintf(stderr,"\n");
				fprintf(stderr,"h2: %2d-%c ",seq2,kar);
				kar2=kar;
			}
			if(kar == 0x01) n2=0;
			if(kar == 0x0d){
//				fprintf(stderr,"h2: %2d-%c ",seq2,kar2);
				fprintf(stderr,"n2: %4d ",n2);
			}

			if(write(fdtty1,&kar,1) != 1){
				perror("write fdtty1 failed");
				goto cleanupandexit;
			}
		}
	}
	
	unlink(lockfile1);
	unlink(lockfile2);
	fprintf(stderr,"simirid normal exit\n");
	exit(0);

cleanupandexit:
	unlink(lockfile1);
	unlink(lockfile2);
	fprintf(stderr,"simirid cleanup and exit\n");
	exit(1);
}