#include <errno.h>
#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/ioctl.h>
#include <sys/select.h>
#include <sys/stat.h>
#include <sys/time.h>
#include <sys/types.h>
#include <termios.h>
#include <time.h>
#include <unistd.h>


/*
*    This program reads data from a serial port and dumps it into a file.
*
*    Copyright (C) 2018 - 2019 R.J. van der Putten, Leiden, Holland, 
*    rob at sput dot nl.
* 
*    This program is free software; you can redistribute it and/or modify
*    it under the terms of the GNU General Public License version 3 as
*    published by the Free Software Foundation.
* 
*    This program is distributed in the hope that it will be useful,
*    but WITHOUT ANY WARRANTY; without even the implied warranty of
*    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
*    GNU General Public License for more details.
*/


#define RECTTY_VERSION "2019-01-31 17:31:28 UTC"

int fd;
struct termios oldtio;

struct my_baud {
	unsigned int rate;
	char *str;
} my_bauds[] = { \
	{    B300,    "300" }, \
	{    B600,    "600" }, \
	{   B1200,   "1200" }, \
	{   B2400,   "2400" }, \
	{   B4800,   "4800" }, \
	{   B9600,   "9600" }, \
	{  B19200,  "19200" }, \
	{  B38400,  "38400" }, \
	{  B57600,  "57600" }, \
	{ B115200, "115200" }, \
	{       0,    NULL  }  \
};

#define MY_DFLT_SPD "115200"

/*
	inspired by
	https://tldp.org/HOWTO/Serial-Programming-HOWTO/x115.html
*/


void resetty(void)
{
        tcflush(fd, TCIOFLUSH);
        tcsetattr(fd, TCSANOW, &oldtio);
        close(fd);
}


void hlp(void)
{
	fprintf(stderr, "Writes data from tty to file.\n");
	fprintf(stderr, \
	    "Usage: recvtty -d device [-b baudrate] [-f filename] [-h] [-m] [-v].\n");
	fprintf(stderr, "-h: Print help and exit.\n");
	fprintf(stderr, "-m: Enable monitoring DSR and DCD;\n");
	fprintf(stderr, \
	    "    The program will terminate when one of them is dropped.\n");
	fprintf(stderr, "-v: Print version and exit.\n");
	fprintf(stderr, "Default baudrate is %s bps.\n", MY_DFLT_SPD);
	fprintf(stderr, "Default filename is YYYYMMDD-hhmmss.dump, ");
	fprintf(stderr, "EG: 20181224-135557.dump\n");
	fprintf(stderr, "The tty is set to RAW, 8N1, RTS-CTS handshaking.\n");
}

void prtvers(void)
{
	printf("Version: %s\n", RECTTY_VERSION);
}

unsigned int findbaud(char *s)
{
	int i;

	i = 0;
	while (my_bauds[i].str != NULL) {
		if(strcmp(s, my_bauds[i].str) == 0)
			return(my_bauds[i].rate);
		i++;
	}

	return(0);
}

void listbauds(void)
{
	int i;

	fprintf(stderr, "%s", my_bauds[0].str);
	i = 1;
	while (my_bauds[i].str != NULL) {
		fprintf(stderr, ", %s", my_bauds[i].str);
		i++;
	}
}


int main(int argc, char **argv)
{
	int cont, ch, ktot, len, maxfd, opt, retval, tot, wlen;
	int modfl, modst, status;
	unsigned int baudrate;
	char baudstr[16], buf[4096], dev[256], filnam[256];
	struct termios newtio;
	FILE *f1;
	fd_set readfs;
	time_t t;
	struct tm *tim;
	struct timeval timeout;

	ch     = 0;
	ktot   = 0;
	len    = 0;
	maxfd  = 0;
	modfl  = 0;	/*  Monitor DSR and DCD if 1  */
	modst  = 0;	/*  DSR and DCD status  */
	opt    = 0;
	retval = 0;
	status = 0;
	t      = 0;
	tot    = 0;
	wlen   = 0;
	memset(buf,     0, sizeof(buf));
	memset(dev,     0, sizeof(dev));
	memset(filnam,  0, sizeof(filnam));
	memset(&newtio, 0, sizeof(newtio));	/*  This makes the tty rather raw  */
	f1   = NULL;
	tim  = NULL;

	strncpy(baudstr, MY_DFLT_SPD, 15);	/*  Default speed  */
	cont = 1;				/*  Continue  */
	timeout.tv_sec  = 2;
	timeout.tv_usec = 0;

	/*  Command line processing  */
	while ((opt = getopt(argc, argv, "b:d:f:hmv")) != -1) {
		switch (opt) {
			case 'b':
				strncpy(baudstr, optarg, 15);
				break;
			case 'd':
				strncpy(dev, optarg, 255);
				break;
			case 'f':
				strncpy(filnam, optarg, 255);
				break;
			case 'h':
				hlp();
				exit(0);
			case 'm':
				/*  Use modem control lines  */
				modfl = 1;
				break;
			case 'v':
				prtvers();
				exit(0);
			default:
				hlp();
				exit(1);
		}
	}
	if ((baudrate = findbaud(baudstr)) == 0) { 
		fprintf(stderr, "Invalid baudrate: %s.\n", baudstr);
		fprintf(stderr, "baudrate must be one of: ");
		listbauds();
		fprintf(stderr, ".\n");
		exit(1);
	}
	if (dev[0] == 0) {
		fprintf(stderr, "Must specify device. EG: -d /dev/ttyS1\n");
		exit(1);
	}

	/*  File name  */
	if (filnam[0] == 0) {
		t = time(NULL);
		tim = localtime(&t);
		snprintf(filnam, 255, "%04d%02d%02d-%02d%02d%02d.dump", \
		    tim->tm_year + 1900, tim->tm_mon + 1, tim->tm_mday, \
		    tim->tm_hour, tim->tm_min, tim->tm_sec);
	}
	if ((f1 = fopen(filnam, "a")) == NULL) {
                fprintf(stderr, "Can't open %s", filnam);
		exit(1);
	}

	/*
	Open modem device for reading and writing and not as controlling tty
	because we don't want to get killed if line noise sends CTRL-C.
	*/
	if ((fd = open(dev, O_RDWR | O_NOCTTY | O_NONBLOCK)) < 0) {
		perror(dev);
		fclose(f1);
		exit(1);
	}

	/*    save current serial port settings    */
	tcgetattr(fd, &oldtio);

	/*
	BAUDRATE: Set bps rate. You could also use cfsetispeed and cfsetospeed.
	CRTSCTS:  Output hardware flow control.
	HUPCL:    Lower modem control lines (DTR) when done.
	CLOCAL:   Ignore modem control (DSR, DCD) lines.
	CREAD:    Enable receiving characters.
	CS8:      8 bit, no parity, 1 stopbit.
	*/
	newtio.c_cflag = baudrate | CRTSCTS | HUPCL | CLOCAL | CREAD | CS8;
	/*
	Input: IGNPAR: ignore bytes with parity errors
	*/
	newtio.c_iflag = IGNPAR;
	/*
	Blocking read until 1 character arrives.
	You don't need this with a non blocking read.
	*/
	/* newtio.c_cc[VMIN] = 1; */

	/*  Clean the modem line and activate the settings for the port  */
	tcflush(fd, TCIOFLUSH);
	if (tcsetattr(fd, TCSANOW, &newtio) != 0) {
		perror(dev);
		resetty();
		fclose(f1);
		exit(1);
	}

	printf("Device: %s, speed: %s bps.\n", dev, baudstr);
	printf("Press <Enter> to quit.\n");

	while (cont != 0) {
		/*  (Re) Initialise select()  */
		FD_ZERO(&readfs);
		FD_SET(0, &readfs);
		FD_SET(fd, &readfs);
		maxfd = fd + 1;
		if(modfl == 0)
			retval = select(maxfd, &readfs, NULL, NULL, NULL);
		else
			retval = select(maxfd, &readfs, NULL, NULL, &timeout);
		if (retval < 0) {
			if (errno == EINTR) {
				fprintf(stderr, "Reinitilizing select().\n");
				continue;
			} else {
				perror("Select failed.");
				resetty();
				fflush(f1);
				fclose(f1);
				exit(1);
			}
		}

		/*  Block until read    */
		if (FD_ISSET(0, &readfs)) {
			/*  Read data from keyboard  */
			read(0, &ch, 1);
			printf("Quitting\n");
			cont = 0;	/*  Don't continue  */
		}
		if (FD_ISSET(fd, &readfs)) {
			/*  Read data from ttySx  */
			len = read(fd, buf, 4095);
			if (len < 1) {
				if (errno == EAGAIN || errno == EINTR) {
					fprintf(stderr, "Reinitilizing select().\n");
					continue;
				} else {
					perror("Can't read from tty.");
					resetty();
					fclose(f1);
					exit(1);
				}
			}
			buf[len] = 0;	/*  Terminate  */
			if ((wlen = fwrite(buf, 1, len, f1)) < 1) {
				fprintf(stderr, "Can't write to output file.\n");
				resetty();
				fclose(f1);
				exit(1);
			}
			if (wlen != len) {
				fprintf(stderr, "Write mismatch.\n");
				resetty();
				fclose(f1);
				exit(1);
			}
			tot = tot + len;
			if (tot > ktot) {
				printf("Wrote %d bytes.\n", tot);
				ktot = ktot + 1024;
			}
			/*  Done reading, check status  */
			if (modfl != 0) {
				ioctl(fd, TIOCMGET, &status);
				if ((status & TIOCM_DSR) != 0)
					modst = modst | 1;	/*  DSR High  */
				if ((status & TIOCM_CD)  != 0)
					modst = modst | 2;	/*  DCD High  */
			}
		}
		/*  Select() timedout  */
		if (modfl != 0) {
			ioctl(fd, TIOCMGET, &status);
			if ((status & TIOCM_DSR) == 0 && (modst & 1) != 0) {
				printf("DSR Dropped, terminating.\n");
				cont = 0;
			} else if ((status & TIOCM_CD) == 0 && (modst & 2) != 0) {
				printf("DCD Dropped, terminating.\n");
				cont = 0;
			}
		}
	}
	
	/*  restore the old port settings  */
	resetty();
	fflush(f1);
	fclose(f1);
	printf("Wrote %d bytes to file %s\n", tot, filnam);

	return(0);
}