/*
 * Raw DCF77 pulse clock support
 *
 * Copyright Frank Kardel <kardel <AT> ntp.org>
 * Copyright the NTPsec project contributors
 * SPDX-License-Identifier: BSD-3-Clause
 */

#include "config.h"
#include "ntp_fp.h"
#include "timespecops.h"
#include "ntp_calendar.h"

#include "parse.h"
#include "ntp_stdlib.h"

/*
 * DCF77 raw time code
 *
 * From "Zur Zeit", Physikalisch-Technische Bundesanstalt (PTB), Braunschweig
 * und Berlin, Maerz 1989
 *
 * Timecode transmission:
 * AM:
 *	time marks are send every second except for the second before the
 *	next minute mark
 *	time marks consist of a reduction of transmitter power to 25%
 *	of the nominal level
 *	the falling edge is the time indication (on time)
 *	time marks of a 100ms duration constitute a logical 0
 *	time marks of a 200ms duration constitute a logical 1
 * FM:
 *	see the spec. (basically a (non-)inverted pseudo random phase shift)
 *
 * Encoding:
 * Second	Contents
 * 0  - 10	AM: free, FM: 0
 * 11 - 14	free
 * 15		R     - "call bit" used to signalize irregularities in the control facilities
 *		        (until 2003 indicated transmission via alternate antenna)
 * 16		A1    - expect zone change (1 hour before)
 * 17 - 18	Z1,Z2 - time zone
 *		 0  0 illegal
 *		 0  1 MEZ  (MET)
 *		 1  0 MESZ (MED, MET DST)
 *		 1  1 illegal
 * 19		A2    - expect leap insertion/deletion (1 hour before)
 * 20		S     - start of time code (1)
 * 21 - 24	M1    - BCD (lsb first) Minutes
 * 25 - 27	M10   - BCD (lsb first) 10 Minutes
 * 28		P1    - Minute Parity (even)
 * 29 - 32	H1    - BCD (lsb first) Hours
 * 33 - 34      H10   - BCD (lsb first) 10 Hours
 * 35		P2    - Hour Parity (even)
 * 36 - 39	D1    - BCD (lsb first) Days
 * 40 - 41	D10   - BCD (lsb first) 10 Days
 * 42 - 44	DW    - BCD (lsb first) day of week (1: Monday -> 7: Sunday)
 * 45 - 49	MO    - BCD (lsb first) Month
 * 50           MO0   - 10 Months
 * 51 - 53	Y1    - BCD (lsb first) Years
 * 54 - 57	Y10   - BCD (lsb first) 10 Years
 * 58 		P3    - Date Parity (even)
 * 59		      - usually missing (minute indication), except for leap insertion
 */

static parse_pps_fnc_t pps_rawdcf;
static parse_cvt_fnc_t cvt_rawdcf;
static parse_inp_fnc_t inp_rawdcf;

typedef struct last_tcode {
	time_t      tcode;	/* last converted time code */
        timestamp_t tminute;	/* sample time for minute start */
        timestamp_t timeout;	/* last timeout timestamp */
} last_tcode_t;

#define BUFFER_MAX	61

clockformat_t clock_rawdcf = {
	inp_rawdcf,			/* DCF77 input handling */
	cvt_rawdcf,			/* raw dcf input conversion */
	pps_rawdcf,			/* examining PPS information */
	0,				/* no private configuration data */
	"RAW DCF77 Timecode",		/* direct decoding / time synthesis */

	BUFFER_MAX,			/* bit buffer */
	sizeof(last_tcode_t)
};

static struct dcfparam
{
	const unsigned char *onebits;
	const unsigned char *zerobits;
} dcfparameter =
{
	(const unsigned char *)"###############RADMLS1248124P124812P1248121241248112481248P??", /* 'ONE' representation */
	(const unsigned char *)"--------------------s-------p------p----------------------p__"  /* 'ZERO' representation */
};

static struct rawdcfcode {
	char offset;			/* start bit */
} rawdcfcode[] = {
	{  0 }, { 15 }, { 16 }, { 17 }, { 19 }, { 20 }, { 21 }, { 25 }, { 28 }, { 29 },
	{ 33 }, { 35 }, { 36 }, { 40 }, { 42 }, { 45 }, { 49 }, { 50 }, { 54 }, { 58 }, { 59 }
};

/* #define DCF_M 0      UNUSED */
#define DCF_R	1
#define DCF_A1	2
#define DCF_Z	3
#define DCF_A2	4
#define DCF_S	5
#define DCF_M1	6
#define DCF_M10	7
/* #define DCF_P1 8     UNUSED */
#define DCF_H1	9
#define DCF_H10	10
/* #define DCF_P2 11    UNUSED */
#define DCF_D1	12
#define DCF_D10	13
/* #define DCF_DW 14    UNUSED */
#define DCF_MO	15
#define DCF_MO0	16
#define DCF_Y1	17
#define DCF_Y10	18
/* #define DCF_P3 19    UNUSED */

static struct partab
{
	char offset;			/* start bit of parity field */
} partab[] =
{
	{ 21 }, { 29 }, { 36 }, { 59 }
};

#define DCF_P_P1	0
#define DCF_P_P2	1
#define DCF_P_P3	2

#define DCF_Z_MET 0x2
#define DCF_Z_MED 0x1

static long ext_bf(unsigned char *, int, const unsigned char *)
	__attribute__((pure));

static long
ext_bf(
	unsigned char *buf,
	int   idx,
	const unsigned char *zero
	)
{
	long sum = 0;
	int i, first;

	first = rawdcfcode[idx].offset;

	for (i = rawdcfcode[idx+1].offset - 1; i >= first; i--)
	{
		sum <<= 1;
		sum |= (buf[i] != zero[i]);
	}
	return sum;
}

static unsigned
pcheck(
       unsigned char *buf,
       int   idx,
       const unsigned char *zero
       )
{
	int i,last;
	unsigned psum = 1;

	last = partab[idx+1].offset;

	for (i = partab[idx].offset; i < last; i++) {
	    psum ^= (buf[i] != zero[i]);
	}

	return psum;
}

static unsigned long
convert_rawdcf(
	       unsigned char   *buffer,
	       int              size,
	       struct dcfparam *dcfprm,
	       clocktime_t     *clock_time
	       )
{
	unsigned char *s = buffer;
	const unsigned char *b = dcfprm->onebits;
	const unsigned char *c = dcfprm->zerobits;
	int i;

	parseprintf(DD_RAWDCF,("parse: convert_rawdcf: \"%.*s\"\n", size, buffer));

	if (size < 57)
	{
		msyslog(LOG_ERR, "ERR: parse: convert_rawdcf: INCOMPLETE DATA - time code only has %d bits", size);
		return CVT_FAIL|CVT_BADFMT;
	}

	for (i = 0; i < size; i++)
	{
		if ((*s != *b) && (*s != *c))
		{
			/*
			 * we only have two types of bytes (ones and zeros)
			 */
			msyslog(LOG_ERR, "ERR: parse: convert_rawdcf: BAD DATA - no conversion");
			return CVT_NONE;
		}
		if (*b) {
			b++;
		}
		if (*c) {
			c++;
		}
		s++;
	}

	/*
	 * check Start and Parity bits
	 */
	if ((ext_bf(buffer, DCF_S, dcfprm->zerobits) == 1) &&
	    pcheck(buffer, DCF_P_P1, dcfprm->zerobits) &&
	    pcheck(buffer, DCF_P_P2, dcfprm->zerobits) &&
	    pcheck(buffer, DCF_P_P3, dcfprm->zerobits))
	{

		/*
		 * buffer OK
		 */
		parseprintf(DD_RAWDCF,("parse: convert_rawdcf: parity check passed\n"));

		clock_time->flags  = PARSEB_S_CALLBIT|PARSEB_S_LEAP;
		clock_time->utctime= 0;
		clock_time->usecond= 0;
		clock_time->second = 0;
		clock_time->minute = ext_bf(buffer, DCF_M10, dcfprm->zerobits);
		clock_time->minute = 10*(clock_time->minute) + ext_bf(buffer, DCF_M1, dcfprm->zerobits);
		clock_time->hour   = ext_bf(buffer, DCF_H10, dcfprm->zerobits);
		clock_time->hour   = 10*(clock_time->hour) + ext_bf(buffer, DCF_H1, dcfprm->zerobits);
		clock_time->day    = ext_bf(buffer, DCF_D10, dcfprm->zerobits);
		clock_time->day    = 10*(clock_time->day) + ext_bf(buffer, DCF_D1, dcfprm->zerobits);
		clock_time->month  = ext_bf(buffer, DCF_MO0, dcfprm->zerobits);
		clock_time->month  = 10*(clock_time->month) + ext_bf(buffer, DCF_MO, dcfprm->zerobits);
		clock_time->year   = ext_bf(buffer, DCF_Y10, dcfprm->zerobits);
		clock_time->year   = 10*(clock_time->year) + ext_bf(buffer, DCF_Y1, dcfprm->zerobits);

		switch (ext_bf(buffer, DCF_Z, dcfprm->zerobits))
		{
		    case DCF_Z_MET:
			clock_time->utcoffset = -1*60*60;
			break;

		    case DCF_Z_MED:
			clock_time->flags     |= PARSEB_DST;
			clock_time->utcoffset  = -2*60*60;
			break;

		    default:
			parseprintf(DD_RAWDCF,("parse: convert_rawdcf: BAD TIME ZONE\n"));
			return CVT_FAIL|CVT_BADFMT;
		}

		if (ext_bf(buffer, DCF_A1, dcfprm->zerobits)) {
		    clock_time->flags |= PARSEB_ANNOUNCE;
		}

		if (ext_bf(buffer, DCF_A2, dcfprm->zerobits)) {
		    clock_time->flags |= PARSEB_LEAPADD; /* default: DCF77 data format deficiency */
		}

		if (ext_bf(buffer, DCF_R, dcfprm->zerobits)) {
		    clock_time->flags |= PARSEB_CALLBIT;
		}

		parseprintf(DD_RAWDCF,("parse: convert_rawdcf: TIME CODE OK: %02d:%02d, %02d.%02d.%02d, flags 0x%lx\n",
				       (int)clock_time->hour, (int)clock_time->minute, (int)clock_time->day, (int)clock_time->month,(int) clock_time->year,
				       (unsigned long)clock_time->flags));
		return CVT_OK;
	}
	else
	{
		/*
		 * bad format - not for us
		 */
	    msyslog(LOG_ERR, "ERR: parse: convert_rawdcf: parity check FAILED for \"%.*s\"", size, buffer);
		return CVT_FAIL|CVT_BADFMT;
	}
}

/*
 * parse_cvt_fnc_t cvt_rawdcf
 * raw dcf input routine - needs to fix up 50 baud
 * characters for 1/0 decision
 */
static unsigned long
cvt_rawdcf(
	   unsigned char   *buffer,
	   int              size,
	   struct format   *param,
	   clocktime_t     *clock_time,
	   void            *local
	   )
{
	last_tcode_t  *t = (last_tcode_t *)local;
	unsigned char *s = (unsigned char *)buffer;
	unsigned char *e = s + size;
	const unsigned char *b = dcfparameter.onebits;
	const unsigned char *c = dcfparameter.zerobits;
	unsigned long       rtc = CVT_NONE;
	unsigned int i, lowmax, highmax, cutoff, span;
#define BITS 9
	unsigned char     histbuf[BITS];
	/*
	 * the input buffer contains characters with runs of consecutive
	 * bits set. These set bits are an indication of the DCF77 pulse
	 * length. We assume that we receive the pulse at 50 Baud. Thus
	 * a 100ms pulse would generate a 4 bit train (20ms per bit and
	 * start bit)
	 * a 200ms pulse would create all zeroes (and probably a frame error)
	 */

	UNUSED_ARG(param);

	for (i = 0; i < BITS; i++) {
		histbuf[i] = 0;
	}

	cutoff = 0;
	lowmax = 0;

	while (s < e) {
		unsigned int ch = *s ^ 0xFF;
		/*
		 * these lines are left as an exercise to the reader 8-)
		 */
		if (!((ch+1) & ch) || !*s) {

			for (i = 0; ch; i++) {
				ch >>= 1;
			}

			*s = (unsigned char) i;
			histbuf[i]++;
			cutoff += i;
			lowmax++;
		} else {
			parseprintf(DD_RAWDCF,("parse: cvt_rawdcf: character check for 0x%x@%d FAILED\n", *s, (int)(s - (unsigned char *)buffer)));
			*s = (unsigned char)~0;
			rtc = CVT_FAIL|CVT_BADFMT;
		}
		s++;
	}

	if (lowmax) {
		cutoff /= lowmax;
	} else {
		cutoff = 4;	/* doesn't really matter - it'll fail anyway, but gives error output */
	}

	parseprintf(DD_RAWDCF,("parse: cvt_rawdcf: average bit count: %u\n",
                    cutoff));

	lowmax = 0;
	highmax = 0;

	parseprintf(DD_RAWDCF,("parse: cvt_rawdcf: histogram:"));
	for (i = 0; i <= cutoff; i++) {
		lowmax+=histbuf[i] * i;
		highmax += histbuf[i];
		parseprintf(DD_RAWDCF,(" %d", histbuf[i]));
	}
	parseprintf(DD_RAWDCF, (" <M>"));

	lowmax += highmax / 2;

	if (highmax) {
		lowmax /= highmax;
	} else {
		lowmax = 0;
	}

	highmax = 0;
	cutoff = 0;

	for (; i < BITS; i++) {
		highmax+=histbuf[i] * i;
		cutoff +=histbuf[i];
		parseprintf(DD_RAWDCF,(" %d", histbuf[i]));
	}
	parseprintf(DD_RAWDCF,("\n"));

	if (cutoff) {
		highmax /= cutoff;
	} else {
		highmax = BITS-1;
	}

	span = cutoff = lowmax;
	for (i = lowmax; i <= highmax; i++) {
		if (histbuf[cutoff] > histbuf[i]) {
			cutoff = i;
			span = i;
		} else if (histbuf[cutoff] == histbuf[i]) {
			span = i;
		}
	}

	cutoff = (cutoff + span) / 2;

	parseprintf(DD_RAWDCF, ("parse: cvt_rawdcf: "
                    "lower maximum %u, higher maximum %u, cutoff %u\n",
                    lowmax, highmax, cutoff));

	s = (unsigned char *)buffer;
	while (s < e)
	{
		if (*s == (unsigned char)~0)
		{
			*s = '?';
		}
		else
		{
			*s = (*s >= cutoff) ? *b : *c;
		}
		s++;
		if (*b) { b++;
}
		if (*c) { c++;
}
	}

	*s = '\0';

        if (rtc == CVT_NONE) {
	       rtc = convert_rawdcf(buffer, size, &dcfparameter, clock_time);
	       if (rtc == CVT_OK) {
			time_t newtime;

			newtime = parse_to_unixtime(clock_time, &rtc);
			if ((rtc == CVT_OK) && t) {
				if ((newtime - t->tcode) <= 600) /* require a successful telegram within last 10 minutes */
				{
				        parseprintf(DD_RAWDCF,("parse: cvt_rawdcf: recent timestamp check OK\n"));
					clock_time->utctime = newtime;
				}
				else
				{
					parseprintf(DD_RAWDCF,("parse: cvt_rawdcf: recent timestamp check FAIL - ignore timestamp\n"));
					rtc = CVT_SKIP;
				}
				t->tcode            = newtime;
			}
	       }
        }

    	return rtc;
}

/*
 * parse_pps_fnc_t pps_rawdcf
 *
 * currently a very stupid version - should be extended to decode
 * also ones and zeros (which is easy)
 */
/*ARGSUSED*/
static unsigned long
pps_rawdcf(
	parse_t *parseio,
	int status,
	timestamp_t *ptime
	)
{
	if (!status)		/* negative edge for simpler wiring (Rx->DCD) */
	{
		parseio->parse_dtime.parse_ptime  = *ptime;
		parseio->parse_dtime.parse_state |= PARSEB_PPS|PARSEB_S_PPS;
	}

	return CVT_NONE;
}

static long
calc_usecdiff(
	timestamp_t *ref,
	timestamp_t *base,
	long         offset
	)
{
	struct timespec delta;
	long delta_usec = 0;
	l_fp delt;

	delt = *ref;
	bumplfpsint(delt, -offset);
	delt -= *base;
	delta = lfp_uintv_to_tspec(delt);

	delta_usec = US_PER_S * (int32_t)delta.tv_sec + delta.tv_nsec / 1000;
	return delta_usec;
}

static unsigned long
snt_rawdcf(
	parse_t *parseio,
	timestamp_t *ptime
	)
{
	/*
	 * only synthesize if all of following conditions are met:
	 * - CVT_OK parse_status (we have a time stamp base)
	 * - ABS(ptime - tminute - (parse_index - 1) sec) < 500ms (spaced by 1 sec +- 500ms)
	 * - minute marker is available (confirms minute raster as base)
	 */
	last_tcode_t  *t = (last_tcode_t *)parseio->parse_pdata;
	long delta_usec = -1;

	/*
	 * 2017-01-07: Emergency repair. This guard used to test
	 * t->tminute.tv.tv_sec, but that cannot have been right as
	 * that tv_sec field was never set anywhere outside the
	 * in-kernel Sun module (long discarded) while this code was
	 * reached in userspace.  It is unknown whether replacing that
	 * test with the analogous one on an l_fp is correct.  This
	 * problem was discovered when reducing the timestamp_t union
	 * - this was one of two references to the UNIX timestamp
	 * member.
	 */
	if (t != NULL && lfpuint(t->tminute) != 0) {
		delta_usec = calc_usecdiff(ptime, &t->tminute, parseio->parse_index - 1);
		if (delta_usec < 0) {
			delta_usec = -delta_usec;
		}
	}

	parseprintf(DD_RAWDCF,("parse: snt_rawdcf: synth for offset %d seconds - absolute usec error %ld\n",
			       parseio->parse_index - 1, delta_usec));

	if (((parseio->parse_dtime.parse_status & CVT_MASK) == CVT_OK) &&
           (delta_usec < (NS_PER_S/2000) && delta_usec >= 0))
	{
		/* only if minute marker is available */
		parseio->parse_dtime.parse_stime = *ptime;

		bumplfpuint(parseio->parse_dtime.parse_time, 1);

		parseprintf(DD_RAWDCF,("parse: snt_rawdcf: time stamp synthesized offset %d seconds\n", parseio->parse_index - 1));

		return updatetimeinfo(parseio, parseio->parse_lstate);
	}
	return CVT_NONE;
}

/*
 * parse_inp_fnc_t inp_rawdcf
 *
 * grab DCF77 data from input stream
 */
static unsigned long
inp_rawdcf(
	  parse_t      *parseio,
	  char         ch,
	  timestamp_t  *tstamp
	  )
{
	/* 1.5 seconds denote second #60 */
	static struct timespec timeout = { 1, (NS_PER_S/2) };

	parseprintf(DD_PARSE, ("inp_rawdcf(0x%lx, 0x%x, ...)\n",
                    (unsigned long)parseio, (unsigned)ch));

	parseio->parse_dtime.parse_stime = *tstamp; /* collect timestamp */

	if (parse_timedout(parseio, tstamp, &timeout))
	{
		last_tcode_t *t = (last_tcode_t *)parseio->parse_pdata;
		long delta_usec;

		parseprintf(DD_RAWDCF, ("inp_rawdcf: time out seen\n"));
		/* finish collection */
		(void) parse_end(parseio);

		if (t != NULL) {
			/* remember minute start sample time if timeouts occur in minute raster */
			/*
			 * 2017-01-07: Emergency repair.  This used to test
			 * t->timeout.tv.tv_sec != 0, but that cannot have been
			 * right as the tv.tv_sec part of (what used to be) the
			 * timestamp_t union was only set in the long-discarded
			 * Sun kernel driver, and this could always be called
			 * from userspace.  Problem discovered while eliminating
			 * the timestamp_t union; this was one of only two
			 * references to the timespec member. It is unknown
			 * whether this change actually corrects the code.
			 */
			if (lfpuint(t->timeout) != 0) {
				delta_usec = calc_usecdiff(tstamp, &t->timeout, 60);
				if (delta_usec < 0) {
					delta_usec = -delta_usec;
				}
			} else {
				delta_usec = -1;
			}

			if (delta_usec < (NS_PER_S/2000) && delta_usec >= 0) {
				parseprintf(DD_RAWDCF, ("inp_rawdcf: timeout time difference %ld usec - minute marker set\n", delta_usec));
				/* collect minute markers only if spaced by 60 seconds */
				t->tminute = *tstamp;
			} else {
				parseprintf(DD_RAWDCF, ("inp_rawdcf: timeout time difference %ld usec - minute marker cleared\n", delta_usec));
				memset((char *)&t->tminute, 0, sizeof(t->tminute));
			}
			t->timeout = *tstamp;
		}
		(void) parse_addchar(parseio, ch);

		/* pass up to higher layers */
		return PARSE_INP_TIME;
	}
	else
	{
		unsigned int rtc;

		rtc = parse_addchar(parseio, ch);
		if (rtc == PARSE_INP_SKIP) {
			if (snt_rawdcf(parseio, tstamp) == CVT_OK) {
				return PARSE_INP_SYNTH;
			}
		}
		return rtc;
	}
}

/*
 * History:
 *
 * clk_rawdcf.c,v
 * Revision 4.18  2006/06/22 18:40:01  kardel
 * clean up signedness (gcc 4)
 *
 * Revision 4.17  2006/01/22 16:01:55  kardel
 * update version information
 *
 * Revision 4.16  2006/01/22 15:51:22  kardel
 * generate reasonable timecode output on invalid input
 *
 * Revision 4.15  2005/08/06 19:17:06  kardel
 * clean log output
 *
 * Revision 4.14  2005/08/06 17:39:40  kardel
 * cleanup size handling wrt/ to buffer boundaries
 *
 * Revision 4.13  2005/04/16 17:32:10  kardel
 * update copyright
 *
 * Revision 4.12  2004/11/14 15:29:41  kardel
 * support PPSAPI, upgrade Copyright to Berkeley style
 *
 * Revision 4.9  1999/12/06 13:42:23  kardel
 * transfer correctly converted time codes always into tcode
 *
 * Revision 4.8  1999/11/28 09:13:50  kardel
 * RECON_4_0_98F
 *
 * Revision 4.7  1999/04/01 20:07:20  kardel
 * added checking for minutie increment of timestamps in clk_rawdcf.c
 *
 * Revision 4.6  1998/06/14 21:09:37  kardel
 * Sun acc cleanup
 *
 * Revision 4.5  1998/06/13 12:04:16  kardel
 * fix SYSV clock name clash
 *
 * Revision 4.4  1998/06/12 15:22:28  kardel
 * fix prototypes
 *
 * Revision 4.3  1998/06/06 18:33:36  kardel
 * simplified condidional compile expression
 *
 * Revision 4.2  1998/05/24 11:04:18  kardel
 * triggering PPS on negative edge for simpler wiring (Rx->DCD)
 *
 * Revision 4.1  1998/05/24 09:39:53  kardel
 * implementation of the new IO handling model
 *
 * Revision 4.0  1998/04/10 19:45:30  kardel
 * Start 4.0 release version numbering
 *
 * from V3 3.24 log info deleted 1998/04/11 kardel
 *
 */
