/*
 * This file is Copyright (c) 2010-2018 by the GPSD project
 * SPDX-License-Identifier: BSD-2-clause
 */
#include <sys/types.h>
#include <err.h>
#include <errno.h>
#include <fcntl.h>
#include <stdarg.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>  /* For nanosleep() */
#include <termios.h>
#include <unistd.h>

#define MODE_RAW 0
#define MODE_NORMAL 1
#define ASHSPD_9600 5
#define ASHSPD_57600 8

static int nmea_send(int , const char *, ... );
static void nmea_add_checksum(char *);
static void serial_speed(int, int);
static void config_raw(int);
static void config_normal(int);

int main(int argc, char **argv) {
	int i, speed, op, fd;
	int rates[] = {57600, 9600, 115200, 4800, 19200, 1200, 0}; /* RTFM */
	char buf[BUFSIZ];

	/* check number of args */
	if (argc != 3){
u:		fprintf(stderr, "usage: ashctl <port> [raw|normal]\n"
				"normal = 9600, GGA+GSA+GSV+RMC+ZDA\n"
				"raw = 57600, normal+XPG+POS+SAT+MCA+PBN+SNV\n"
				);
		return 1;
	}

	/* validate command */
	if (strcmp(argv[2], "raw") == 0)
		op = MODE_RAW;
	else if (strcmp(argv[2], "normal") == 0)
		op = MODE_NORMAL;
	else
		goto u;

	if ((fd = open(argv[1], O_RDWR | O_NONBLOCK | O_NOCTTY, 0644)) == -1)
		err(1, "open");

	i = 0;
	/* spam receiver w/ config messages */
	while((speed = rates[i++])){
		fprintf(stderr,
			"\010\010\010\010\010\010\010\010"
			"\010\010\010\010\010\010\010\010"
			"\010\010\010\010\010\010\010\010"
			"\010\010\010\010\010\010\010\010"
			"configuring at %d bps...  ", speed);
		serial_speed(fd, speed);
		if (op == MODE_NORMAL) {
			config_normal(fd);
			serial_speed(fd, 9600);
		} else if (op == MODE_RAW) {
			config_raw(fd);
			serial_speed(fd, 57600);
		}

		sleep(1);
		i = read(fd, buf, BUFSIZ-1);
		buf[i] = '\0';
		if (strstr(buf, "$PASH") || strstr(buf, "$GP"))
			goto done;
	}
done:	fprintf(stderr,
		"\010\010\010\010\010\010\010\010"
		"\010\010\010\010\010\010\010\010"
		"\010\010\010\010\010\010\010\010"
		"\010\010\010\010\010\010\010\010"
		"receiver configuration done         \n");
	return 0;
}

static void serial_speed(int fd, int speed){
	struct termios term;

	tcgetattr(fd, &term);
	cfmakeraw(&term);
	cfsetospeed(&term, speed);
	cfsetispeed(&term, speed);
	if (tcsetattr(fd, TCSANOW | TCSAFLUSH, &term) == -1)
		err(1, "tcsetattr");

	tcflush(fd, TCIOFLUSH);
	return;
}

static void config_normal(int fd){
	nmea_send(fd, "$PASHS,NME,ALL,A,OFF"); /* silence outbound chatter */
	nmea_send(fd, "$PASHS,NME,ALL,B,OFF");
	nmea_send(fd, "$PASHS,NME,GGA,A,ON");
	nmea_send(fd, "$PASHS,NME,GSA,A,ON");
	nmea_send(fd, "$PASHS,NME,GSV,A,ON");
	nmea_send(fd, "$PASHS,NME,RMC,A,ON");
	nmea_send(fd, "$PASHS,NME,ZDA,A,ON");

	nmea_send(fd, "$PASHS,INI,%d,%d,,,0,",ASHSPD_9600, ASHSPD_9600);
	sleep(6); /* it takes 4-6 sec for the receiver to reboot */
	nmea_send(fd, "$PASHS,WAS,ON"); /* enable WAAS */
}

static void config_raw(int fd){
	nmea_send(fd, "$PASHS,NME,ALL,A,OFF"); /* silence outbound chatter */
	nmea_send(fd, "$PASHS,NME,ALL,B,OFF");
	nmea_send(fd, "$PASHS,NME,GGA,A,ON");
	nmea_send(fd, "$PASHS,NME,GSA,A,ON");
	nmea_send(fd, "$PASHS,NME,GSV,A,ON");
	nmea_send(fd, "$PASHS,NME,RMC,A,ON");
	nmea_send(fd, "$PASHS,NME,ZDA,A,ON");

	nmea_send(fd, "$PASHS,INI,%d,%d,,,0,",ASHSPD_57600, ASHSPD_9600);
	sleep(6); /* it takes 4-6 sec for the receiver to reboot */
	nmea_send(fd, "$PASHS,WAS,ON"); /* enable WAAS */

	nmea_send(fd, "$PASHS,NME,POS,A,ON"); /* Ashtech PVT solution */
	nmea_send(fd, "$PASHS,NME,SAT,A,ON"); /* Ashtech Satellite status */
	nmea_send(fd, "$PASHS,NME,MCA,A,ON"); /* MCA measurements */
	nmea_send(fd, "$PASHS,NME,PBN,A,ON"); /* ECEF PVT solution */
	nmea_send(fd, "$PASHS,NME,SNV,A,ON,10"); /* Almanac data */

	nmea_send(fd, "$PASHS,NME,XMG,A,ON"); /* exception messages */
}

static void nmea_add_checksum(char *sentence)
/* add NMEA checksum to a possibly  *-terminated sentence */
{
	char *p = sentence;

	if (*p == '$') {
		unsigned char sum = '\0';
		char c;

		p++;
		while ( ((c = *p) != '*') && (c != '\0')) {
			sum ^= c;
			p++;
		}
		*p++ = '*';
		(void)snprintf(p, 5, "%02X\r\n", (unsigned int)sum);
	}
}

static int nmea_send(int fd, const char *fmt, ... )
/* ship a command to the GPS, adding * and correct checksum */
{
	size_t status;
	char buf[BUFSIZ];
	va_list ap;
	struct timespec delay;

	va_start(ap, fmt) ;
	(void)vsnprintf(buf, sizeof(buf)-5, fmt, ap);
	va_end(ap);
	(void)strncat(buf, "*", sizeof(buf)-1);
	nmea_add_checksum(buf);
	// (void)fputs(buf, stderr); /* debug output */
	tcflush(fd, TCIOFLUSH);
	status = (size_t)write(fd, buf, strlen(buf));
	tcdrain(fd);
        /* wait 100,000 uSec */
	delay.tv_sec = 0;
	delay.tv_nsec = 100000000L;
	nanosleep(&delay, NULL);

	if (status == strlen(buf)) {
		return (int)status;
	} else {
		perror("nmea_send");
		return -1;
	}
}