/* net_dgpsip.c -- gather and dispatch DGPS data from DGPSIP servers
 *
 * This file is Copyright (c) 2010 by the GPSD project
 * BSD terms apply: see the file COPYING in the distribution root for details.
 */
#include <sys/types.h>
#include <stdio.h>
#include <stdbool.h>
#include <stdlib.h>
#include <string.h>
#include <fcntl.h>
#ifndef S_SPLINT_S
#include <netdb.h>
#include <sys/socket.h>
#include <unistd.h>
#endif /* S_SPLINT_S */

#include "gpsd.h"

/*@ -branchstate */
int dgpsip_open(struct gps_context_t *context, const char *dgpsserver)
/* open a connection to a DGPSIP server */
{
    char hn[256], buf[BUFSIZ];
    char *colon, *dgpsport = "rtcm-sc104";
    int opts;

    if ((colon = strchr(dgpsserver, ':')) != NULL) {
	dgpsport = colon + 1;
	*colon = '\0';
    }
    if (!getservbyname(dgpsport, "tcp"))
	dgpsport = DEFAULT_RTCM_PORT;

    context->dsock =
	netlib_connectsock(AF_UNSPEC, dgpsserver, dgpsport, "tcp");
    if (context->dsock >= 0) {
	gpsd_report(LOG_PROG, "connection to DGPS server %s established.\n",
		    dgpsserver);
	(void)gethostname(hn, sizeof(hn));
	/* greeting required by some RTCM104 servers; others will ignore it */
	(void)snprintf(buf, sizeof(buf), "HELO %s gpsd %s\r\nR\r\n", hn,
		       VERSION);
	if (write(context->dsock, buf, strlen(buf)) == (ssize_t) strlen(buf))
	    context->netgnss_service = netgnss_dgpsip;
	else
	    gpsd_report(LOG_ERROR, "hello to DGPS server %s failed\n",
			dgpsserver);
    } else
	gpsd_report(LOG_ERROR,
		    "can't connect to DGPS server %s, netlib error %d.\n",
		    dgpsserver, context->dsock);
    opts = fcntl(context->dsock, F_GETFL);

    if (opts >= 0)
	(void)fcntl(context->dsock, F_SETFL, opts | O_NONBLOCK);
    return context->dsock;
}

/*@ +branchstate */

void dgpsip_report(struct gps_device_t *session)
/* may be time to ship a usage report to the DGPSIP server */
{
    /*
     * 10 is an arbitrary number, the point is to have gotten several good
     * fixes before reporting usage to our DGPSIP server.
     */
    if (session->context->fixcnt > 10 && !session->context->sentdgps) {
	session->context->sentdgps = true;
	if (session->context->dsock > -1) {
	    char buf[BUFSIZ];
	    (void)snprintf(buf, sizeof(buf), "R %0.8f %0.8f %0.2f\r\n",
			   session->gpsdata.fix.latitude,
			   session->gpsdata.fix.longitude,
			   session->gpsdata.fix.altitude);
	    if (write(session->context->dsock, buf, strlen(buf)) ==
		(ssize_t) strlen(buf))
		gpsd_report(LOG_IO, "=> dgps %s\n", buf);
	    else
		gpsd_report(LOG_IO, "write to dgps FAILED\n");
	}
    }
}

#define DGPS_THRESHOLD	1600000	/* max. useful dist. from DGPS server (m) */
#define SERVER_SAMPLE	12	/* # of servers within threshold to check */

struct dgps_server_t
{
    double lat, lon;
    char server[257];
    double dist;
};

static int srvcmp(const void *s, const void *t)
{
    return (int)(((const struct dgps_server_t *)s)->dist - ((const struct dgps_server_t *)t)->dist);	/* fixes: warning: cast discards qualifiers from pointer target type */
}

void dgpsip_autoconnect(struct gps_context_t *context,
			double lat, double lon, const char *serverlist)
/* tell the library to talk to the nearest DGPSIP server */
{
    struct dgps_server_t keep[SERVER_SAMPLE], hold, *sp, *tp;
    char buf[BUFSIZ];
    FILE *sfp = fopen(serverlist, "r");

    if (sfp == NULL) {
	gpsd_report(LOG_ERROR, "no DGPS server list found.\n");
	context->dsock = -2;	/* don't try this again */
	return;
    }

    for (sp = keep; sp < keep + SERVER_SAMPLE; sp++) {
	sp->dist = DGPS_THRESHOLD;
	sp->server[0] = '\0';
    }
    /*@ -usedef @*/
    while (fgets(buf, (int)sizeof(buf), sfp)) {
	char *cp = strchr(buf, '#');
	if (cp != NULL)
	    *cp = '\0';
	if (sscanf(buf, "%lf %lf %256s", &hold.lat, &hold.lon, hold.server) ==
	    3) {
	    hold.dist = earth_distance(lat, lon, hold.lat, hold.lon);
	    tp = NULL;
	    /*
	     * The idea here is to look for a server in the sample array
	     * that is (a) closer than the one we're checking, and (b)
	     * furtherest away of all those that are closer.  Replace it.
	     * In this way we end up with the closest possible set.
	     */
	    for (sp = keep; sp < keep + SERVER_SAMPLE; sp++)
		if (hold.dist < sp->dist
		    && (tp == NULL || hold.dist > tp->dist))
		    tp = sp;
	    if (tp != NULL)
		memcpy(tp, &hold, sizeof(struct dgps_server_t));
	}
    }
    (void)fclose(sfp);

    if (keep[0].server[0] == '\0') {
	gpsd_report(LOG_ERROR, "no DGPS servers within %dm.\n",
		    (int)(DGPS_THRESHOLD / 1000));
	context->dsock = -2;	/* don't try this again */
	return;
    }
    /*@ +usedef @*/

    /* sort them and try the closest first */
    qsort((void *)keep, SERVER_SAMPLE, sizeof(struct dgps_server_t), srvcmp);
    for (sp = keep; sp < keep + SERVER_SAMPLE; sp++) {
	if (sp->server[0] != '\0') {
	    gpsd_report(LOG_INF, "%s is %dkm away.\n", sp->server,
			(int)(sp->dist / 1000));
	    if (dgpsip_open(context, sp->server) >= 0)
		break;
	}
    }
}