/* CCCH passive sniffer */
/* (C) 2010-2011 by Holger Hans Peter Freyther
 * (C) 2010 by Harald Welte <laforge@gnumonks.org>
 *
 * All Rights Reserved
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * 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.
 *
 * You should have received a copy of the GNU General Public License along
 * with this program; if not, write to the Free Software Foundation, Inc.,
 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 */

#include <stdint.h>
#include <errno.h>
#include <stdio.h>
#include <time.h>

#include <osmocom/core/msgb.h>
#include <osmocom/gsm/rsl.h>
#include <osmocom/gsm/tlv.h>
#include <osmocom/gsm/gsm48_ie.h>
#include <osmocom/gsm/gsm48.h>
#include <osmocom/core/signal.h>
#include <osmocom/gsm/protocol/gsm_04_08.h>

#include <osmocom/bb/common/logging.h>
#include <osmocom/bb/misc/rslms.h>
#include <osmocom/bb/misc/layer3.h>
#include <osmocom/bb/common/osmocom_data.h>
#include <osmocom/bb/common/l1ctl.h>
#include <osmocom/bb/common/l23_app.h>

#include <l1ctl_proto.h>

enum dch_state_t {
	DCH_NONE,
	DCH_WAIT_EST,
	DCH_ACTIVE,
	DCH_WAIT_REL,
};

static struct {
	int			has_si1;
	int			ccch_mode;

	enum dch_state_t	dch_state;
	uint8_t			dch_nr;
	int			dch_badcnt;

	FILE *			fh;

	struct gsm_sysinfo_freq	cell_arfcns[1024];
} app_state;


static void dump_bcch(struct osmocom_ms *ms, uint8_t tc, const uint8_t *data)
{
	struct gsm48_system_information_type_header *si_hdr;
	si_hdr = (struct gsm48_system_information_type_header *) data;

	/* GSM 05.02 §6.3.1.3 Mapping of BCCH data */
	switch (si_hdr->system_information) {
	case GSM48_MT_RR_SYSINFO_1:
#ifdef BCCH_TC_CHECK
		if (tc != 0)
			LOGP(DRR, LOGL_ERROR, "SI1 on the wrong TC: %d\n", tc);
#endif
		if (!app_state.has_si1) {
			struct gsm48_system_information_type_1 *si1 =
				(struct gsm48_system_information_type_1 *)data;

			gsm48_decode_freq_list(app_state.cell_arfcns,
			                       si1->cell_channel_description,
					       sizeof(si1->cell_channel_description),
					       0xff, 0x01);

			app_state.has_si1 = 1;
			LOGP(DRR, LOGL_ERROR, "SI1 received.\n");
		}
		break;
	case GSM48_MT_RR_SYSINFO_2:
#ifdef BCCH_TC_CHECK
		if (tc != 1)
			LOGP(DRR, LOGL_ERROR, "SI2 on the wrong TC: %d\n", tc);
#endif
		break;
	case GSM48_MT_RR_SYSINFO_3:
#ifdef BCCH_TC_CHECK
		if (tc != 2 && tc != 6)
			LOGP(DRR, LOGL_ERROR, "SI3 on the wrong TC: %d\n", tc);
#endif
		if (app_state.ccch_mode == CCCH_MODE_NONE) {
			struct gsm48_system_information_type_3 *si3 =
				(struct gsm48_system_information_type_3 *)data;

			if (si3->control_channel_desc.ccch_conf == RSL_BCCH_CCCH_CONF_1_C)
				app_state.ccch_mode = CCCH_MODE_COMBINED;
			else
				app_state.ccch_mode = CCCH_MODE_NON_COMBINED;

			l1ctl_tx_ccch_mode_req(ms, app_state.ccch_mode);
		}
		break;
	case GSM48_MT_RR_SYSINFO_4:
#ifdef BCCH_TC_CHECK
		if (tc != 3 && tc != 7)
			LOGP(DRR, LOGL_ERROR, "SI4 on the wrong TC: %d\n", tc);
#endif
		break;
	case GSM48_MT_RR_SYSINFO_5:
		break;
	case GSM48_MT_RR_SYSINFO_6:
		break;
	case GSM48_MT_RR_SYSINFO_7:
#ifdef BCCH_TC_CHECK
		if (tc != 7)
			LOGP(DRR, LOGL_ERROR, "SI7 on the wrong TC: %d\n", tc);
#endif
		break;
	case GSM48_MT_RR_SYSINFO_8:
#ifdef BCCH_TC_CHECK
		if (tc != 3)
			LOGP(DRR, LOGL_ERROR, "SI8 on the wrong TC: %d\n", tc);
#endif
		break;
	case GSM48_MT_RR_SYSINFO_9:
#ifdef BCCH_TC_CHECK
		if (tc != 4)
			LOGP(DRR, LOGL_ERROR, "SI9 on the wrong TC: %d\n", tc);
#endif
		break;
	case GSM48_MT_RR_SYSINFO_13:
#ifdef BCCH_TC_CHECK
		if (tc != 4 && tc != 0)
			LOGP(DRR, LOGL_ERROR, "SI13 on the wrong TC: %d\n", tc);
#endif
		break;
	case GSM48_MT_RR_SYSINFO_16:
#ifdef BCCH_TC_CHECK
		if (tc != 6)
			LOGP(DRR, LOGL_ERROR, "SI16 on the wrong TC: %d\n", tc);
#endif
		break;
	case GSM48_MT_RR_SYSINFO_17:
#ifdef BCCH_TC_CHECK
		if (tc != 2)
			LOGP(DRR, LOGL_ERROR, "SI17 on the wrong TC: %d\n", tc);
#endif
		break;
	case GSM48_MT_RR_SYSINFO_2bis:
#ifdef BCCH_TC_CHECK
		if (tc != 5)
			LOGP(DRR, LOGL_ERROR, "SI2bis on the wrong TC: %d\n", tc);
#endif
		break;
	case GSM48_MT_RR_SYSINFO_2ter:
#ifdef BCCH_TC_CHECK
		if (tc != 5 && tc != 4)
			LOGP(DRR, LOGL_ERROR, "SI2ter on the wrong TC: %d\n", tc);
#endif
		break;
	case GSM48_MT_RR_SYSINFO_5bis:
		break;
	case GSM48_MT_RR_SYSINFO_5ter:
		break;
	default:
		LOGP(DRR, LOGL_ERROR, "Unknown SI: %d\n",
		     si_hdr->system_information);
		break;
	};
}


/**
 * This method used to send a l1ctl_tx_dm_est_req_h0 or
 * a l1ctl_tx_dm_est_req_h1 to the layer1 to follow this
 * assignment. The code has been removed.
 */
static int gsm48_rx_imm_ass(struct msgb *msg, struct osmocom_ms *ms)
{
	struct gsm48_imm_ass *ia = msgb_l3(msg);
	uint8_t ch_type, ch_subch, ch_ts;
	int rv;

	/* Discard packet TBF assignement */
	if (ia->page_mode & 0xf0)
		return 0;

	/* If we're not ready yet, or just busy ... */
	if ((!app_state.has_si1) || (app_state.dch_state != DCH_NONE))
		return 0;

	rsl_dec_chan_nr(ia->chan_desc.chan_nr, &ch_type, &ch_subch, &ch_ts);

	if (!ia->chan_desc.h0.h) {
		/* Non-hopping */
		uint16_t arfcn;

		arfcn = ia->chan_desc.h0.arfcn_low | (ia->chan_desc.h0.arfcn_high << 8);

		LOGP(DRR, LOGL_NOTICE, "GSM48 IMM ASS (ra=0x%02x, chan_nr=0x%02x, "
			"ARFCN=%u, TS=%u, SS=%u, TSC=%u) ", ia->req_ref.ra,
			ia->chan_desc.chan_nr, arfcn, ch_ts, ch_subch,
			ia->chan_desc.h0.tsc);

		/* request L1 to go to dedicated mode on assigned channel */
		rv = l1ctl_tx_dm_est_req_h0(ms,
			arfcn, ia->chan_desc.chan_nr, ia->chan_desc.h0.tsc,
			GSM48_CMODE_SIGN, 0);
	} else {
		/* Hopping */
		uint8_t maio, hsn, ma_len;
		uint16_t ma[64], arfcn;
		int i, j, k;

		hsn = ia->chan_desc.h1.hsn;
		maio = ia->chan_desc.h1.maio_low | (ia->chan_desc.h1.maio_high << 2);

		LOGP(DRR, LOGL_NOTICE, "GSM48 IMM ASS (ra=0x%02x, chan_nr=0x%02x, "
			"HSN=%u, MAIO=%u, TS=%u, SS=%u, TSC=%u) ", ia->req_ref.ra,
			ia->chan_desc.chan_nr, hsn, maio, ch_ts, ch_subch,
			ia->chan_desc.h1.tsc);

		/* decode mobile allocation */
		ma_len = 0;
		for (i=1, j=0; i<=1024; i++) {
			arfcn = i & 1023;
			if (app_state.cell_arfcns[arfcn].mask & 0x01) {
				k = ia->mob_alloc_len - (j>>3) - 1;
				if (ia->mob_alloc[k] & (1 << (j&7))) {
					ma[ma_len++] = arfcn;
				}
				j++;
			}
		}

		/* request L1 to go to dedicated mode on assigned channel */
		rv = l1ctl_tx_dm_est_req_h1(ms,
			maio, hsn, ma, ma_len,
			ia->chan_desc.chan_nr, ia->chan_desc.h1.tsc,
			GSM48_CMODE_SIGN, 0);
	}

	LOGPC(DRR, LOGL_NOTICE, "\n");

	/* Set state */
	app_state.dch_state = DCH_WAIT_EST;
	app_state.dch_nr = ia->chan_desc.chan_nr;
	app_state.dch_badcnt = 0;

	return rv;
}

static const char *pag_print_mode(int mode)
{
	switch (mode) {
	case 0:
		return "Normal paging";
	case 1:
		return "Extended paging";
	case 2:
		return "Paging reorganization";
	case 3:
		return "Same as before";
	default:
		return "invalid";
	}
}

static char *chan_need(int need)
{
	switch (need) {
	case 0:
		return "any";
	case 1:
		return "sdch";
	case 2:
		return "tch/f";
	case 3:
		return "tch/h";
	default:
		return "invalid";
	}
}

static char *mi_type_to_string(int type)
{
	switch (type) {
	case GSM_MI_TYPE_NONE:
		return "none";
	case GSM_MI_TYPE_IMSI:
		return "imsi";
	case GSM_MI_TYPE_IMEI:
		return "imei";
	case GSM_MI_TYPE_IMEISV:
		return "imeisv";
	case GSM_MI_TYPE_TMSI:
		return "tmsi";
	default:
		return "invalid";
	}
}

/**
 * This can contain two MIs. The size checking is a bit of a mess.
 */
static int gsm48_rx_paging_p1(struct msgb *msg, struct osmocom_ms *ms)
{
	struct gsm48_paging1 *pag;
	int len1, len2, mi_type, tag;
	char mi_string[GSM48_MI_SIZE];

	/* is there enough room for the header + LV? */
	if (msgb_l3len(msg) < sizeof(*pag) + 2) {
		LOGP(DRR, LOGL_ERROR, "PagingRequest is too short.\n");
		return -1;
	}

	pag = msgb_l3(msg);
	len1 = pag->data[0];
	mi_type = pag->data[1] & GSM_MI_TYPE_MASK;

	if (msgb_l3len(msg) < sizeof(*pag) + 2 + len1) {
		LOGP(DRR, LOGL_ERROR, "PagingRequest with wrong MI\n");
		return -1;
	}

	if (mi_type != GSM_MI_TYPE_NONE) {
		gsm48_mi_to_string(mi_string, sizeof(mi_string), &pag->data[1], len1);
		LOGP(DRR, LOGL_NOTICE, "Paging1: %s chan %s to %s M(%s) \n",
		     pag_print_mode(pag->pag_mode),
		     chan_need(pag->cneed1),
		     mi_type_to_string(mi_type),
		     mi_string);
	}

	/* check if we have a MI type in here */
	if (msgb_l3len(msg) < sizeof(*pag) + 2 + len1 + 3)
		return 0;

	tag = pag->data[2 + len1 + 0];
	len2 = pag->data[2 + len1 + 1];
	mi_type = pag->data[2 + len1 + 2] & GSM_MI_TYPE_MASK;
	if (tag == GSM48_IE_MOBILE_ID && mi_type != GSM_MI_TYPE_NONE) {
		if (msgb_l3len(msg) < sizeof(*pag) + 2 + len1 + 3 + len2) {
			LOGP(DRR, LOGL_ERROR, "Optional MI does not fit here.\n");
			return -1;
		}

		gsm48_mi_to_string(mi_string, sizeof(mi_string), &pag->data[2 + len1 + 2], len2);
		LOGP(DRR, LOGL_NOTICE, "Paging2: %s chan %s to %s M(%s) \n",
		     pag_print_mode(pag->pag_mode),
		     chan_need(pag->cneed2),
		     mi_type_to_string(mi_type),
		     mi_string);
	}
	return 0;
}

static int gsm48_rx_paging_p2(struct msgb *msg, struct osmocom_ms *ms)
{
	struct gsm48_paging2 *pag;
	int tag, len, mi_type;
	char mi_string[GSM48_MI_SIZE];

	if (msgb_l3len(msg) < sizeof(*pag)) {
		LOGP(DRR, LOGL_ERROR, "Paging2 message is too small.\n");
		return -1;
	}

	pag = msgb_l3(msg);
	LOGP(DRR, LOGL_NOTICE, "Paging1: %s chan %s to TMSI M(0x%x) \n",
		     pag_print_mode(pag->pag_mode),
		     chan_need(pag->cneed1), pag->tmsi1);
	LOGP(DRR, LOGL_NOTICE, "Paging2: %s chan %s to TMSI M(0x%x) \n",
		     pag_print_mode(pag->pag_mode),
		     chan_need(pag->cneed2), pag->tmsi2);

	/* no optional element */
	if (msgb_l3len(msg) < sizeof(*pag) + 3)
		return 0;

	tag = pag->data[0];
	len = pag->data[1];
	mi_type = pag->data[2] & GSM_MI_TYPE_MASK;

	if (tag != GSM48_IE_MOBILE_ID)
		return 0;

	if (msgb_l3len(msg) < sizeof(*pag) + 3 + len) {
		LOGP(DRR, LOGL_ERROR, "Optional MI does not fit in here\n");
		return -1;
	}

	gsm48_mi_to_string(mi_string, sizeof(mi_string), &pag->data[2], len);
	LOGP(DRR, LOGL_NOTICE, "Paging3: %s chan %s to %s M(%s) \n",
	     pag_print_mode(pag->pag_mode),
	     "n/a ",
	     mi_type_to_string(mi_type),
	     mi_string);

	return 0;
}

static int gsm48_rx_paging_p3(struct msgb *msg, struct osmocom_ms *ms)
{
	struct gsm48_paging3 *pag;

	if (msgb_l3len(msg) < sizeof(*pag)) {
		LOGP(DRR, LOGL_ERROR, "Paging3 message is too small.\n");
		return -1;
	}

	pag = msgb_l3(msg);
	LOGP(DRR, LOGL_NOTICE, "Paging1: %s chan %s to TMSI M(0x%x) \n",
		     pag_print_mode(pag->pag_mode),
		     chan_need(pag->cneed1), pag->tmsi1);
	LOGP(DRR, LOGL_NOTICE, "Paging2: %s chan %s to TMSI M(0x%x) \n",
		     pag_print_mode(pag->pag_mode),
		     chan_need(pag->cneed2), pag->tmsi2);
	LOGP(DRR, LOGL_NOTICE, "Paging3: %s chan %s to TMSI M(0x%x) \n",
		     pag_print_mode(pag->pag_mode),
		     "n/a ", pag->tmsi3);
	LOGP(DRR, LOGL_NOTICE, "Paging4: %s chan %s to TMSI M(0x%x) \n",
		     pag_print_mode(pag->pag_mode),
		     "n/a ", pag->tmsi4);

	return 0;
}

int gsm48_rx_ccch(struct msgb *msg, struct osmocom_ms *ms)
{
	struct gsm48_system_information_type_header *sih = msgb_l3(msg);
	int rc = 0;

	/* CCCH marks the end of WAIT_REL */
	if (app_state.dch_state == DCH_WAIT_REL)
		app_state.dch_state = DCH_NONE;

	if (sih->rr_protocol_discriminator != GSM48_PDISC_RR)
		LOGP(DRR, LOGL_ERROR, "PCH pdisc != RR\n");

	switch (sih->system_information) {
	case GSM48_MT_RR_PAG_REQ_1:
		gsm48_rx_paging_p1(msg, ms);
		break;
	case GSM48_MT_RR_PAG_REQ_2:
		gsm48_rx_paging_p2(msg, ms);
		break;
	case GSM48_MT_RR_PAG_REQ_3:
		gsm48_rx_paging_p3(msg, ms);
		break;
	case GSM48_MT_RR_IMM_ASS:
		gsm48_rx_imm_ass(msg, ms);
		break;
	case GSM48_MT_RR_NOTIF_NCH:
		/* notification for voice call groups and such */
		break;
	case 0x07:
		/* wireshark know that this is SI2 quater and for 3G interop */
		break;
	default:
		LOGP(DRR, LOGL_NOTICE, "unknown PCH/AGCH type 0x%02x\n",
			sih->system_information);
		rc = -EINVAL;
	}

	return rc;
}

int gsm48_rx_bcch(struct msgb *msg, struct osmocom_ms *ms)
{
	/* BCCH marks the end of WAIT_REL */
	if (app_state.dch_state == DCH_WAIT_REL)
		app_state.dch_state = DCH_NONE;

	/* FIXME: we have lost the gsm frame time until here, need to store it
	 * in some msgb context */
	//dump_bcch(dl->time.tc, ccch->data);
	dump_bcch(ms, 0, msg->l3h);

	return 0;
}

static char *
gen_filename(struct osmocom_ms *ms, struct l1ctl_burst_ind *bi)
{
	static char buffer[256];
	time_t d;
	struct tm lt;

	time(&d);
	localtime_r(&d, &lt);

	snprintf(buffer, 256, "bursts_%04d%02d%02d_%02d%02d_%d_%d_%02x.dat",
		lt.tm_year + 1900, lt.tm_mon, lt.tm_mday,
		lt.tm_hour, lt.tm_min,
		ms->test_arfcn,
		ntohl(bi->frame_nr),
		bi->chan_nr
	);

	return buffer;
}

void layer3_rx_burst(struct osmocom_ms *ms, struct msgb *msg)
{
	struct l1ctl_burst_ind *bi;
	int16_t rx_dbm;
	uint16_t arfcn;
	int ul, do_rel=0;

	/* Header handling */
	bi = (struct l1ctl_burst_ind *) msg->l1h;

	arfcn = ntohs(bi->band_arfcn);
	rx_dbm = rxlev2dbm(bi->rx_level);
	ul = !!(arfcn & ARFCN_UPLINK);

	/* Check for channel start */
	if (app_state.dch_state == DCH_WAIT_EST) {
		if (bi->chan_nr == app_state.dch_nr) {
			if (bi->snr > 64) {
				/* Change state */
				app_state.dch_state = DCH_ACTIVE;
				app_state.dch_badcnt = 0;

				/* Open output */
				app_state.fh = fopen(gen_filename(ms, bi), "wb");
			} else {
				/* Abandon ? */
				do_rel = (app_state.dch_badcnt++) >= 4;
			}
		}
	}

	/* Check for channel end */
	if (app_state.dch_state == DCH_ACTIVE) {
		if (!ul) {
			/* Bad burst counting */
			if (bi->snr < 64)
				app_state.dch_badcnt++;
			else if (app_state.dch_badcnt >= 2)
				app_state.dch_badcnt -= 2;
			else
				app_state.dch_badcnt = 0;

			/* Release condition */
			do_rel = app_state.dch_badcnt >= 6;
		}
	}

	/* Release ? */
	if (do_rel) {
		/* L1 release */
		l1ctl_tx_dm_rel_req(ms);
		l1ctl_tx_fbsb_req(ms, ms->test_arfcn,
				L1CTL_FBSB_F_FB01SB, 100, 0,
				app_state.ccch_mode);

		/* Change state */
		app_state.dch_state = DCH_WAIT_REL;
		app_state.dch_badcnt = 0;

		/* Close output */
		if (app_state.fh) {
			fclose(app_state.fh);
			app_state.fh = NULL;
		}
	}

	/* Save the burst */
	if (app_state.dch_state == DCH_ACTIVE)
		fwrite(bi, sizeof(*bi), 1, app_state.fh);

}

void layer3_app_reset(void)
{
	/* Reset state */
	app_state.has_si1 = 0;
	app_state.ccch_mode = CCCH_MODE_NONE;
	app_state.dch_state = DCH_NONE;
	app_state.dch_badcnt = 0;

	if (app_state.fh)
		fclose(app_state.fh);
	app_state.fh = NULL;

	memset(&app_state.cell_arfcns, 0x00, sizeof(app_state.cell_arfcns));
}

static int signal_cb(unsigned int subsys, unsigned int signal,
		     void *handler_data, void *signal_data)
{
	struct osmocom_ms *ms;
	struct osmobb_msg_ind *mi;

	if (subsys != SS_L1CTL)
		return 0;

	switch (signal) {
	case S_L1CTL_BURST_IND:
		mi = signal_data;
		layer3_rx_burst(mi->ms, mi->msg);
		break;

	case S_L1CTL_RESET:
		ms = signal_data;
		layer3_app_reset();
		return l1ctl_tx_fbsb_req(ms, ms->test_arfcn,
		                         L1CTL_FBSB_F_FB01SB, 100, 0,
		                         CCCH_MODE_NONE, dbm2rxlev(-85));
		break;
	}
	return 0;
}


int l23_app_init(struct osmocom_ms *ms)
{
	osmo_signal_register_handler(SS_L1CTL, &signal_cb, NULL);
	l1ctl_tx_reset_req(ms, L1CTL_RES_T_FULL);
	return layer3_init(ms);
}

static struct l23_app_info info = {
	.copyright	= "Copyright (C) 2010 Harald Welte <laforge@gnumonks.org>\n",
	.contribution	= "Contributions by Holger Hans Peter Freyther\n",
};

struct l23_app_info *l23_app_info()
{
	return &info;
}