/* GSM 04.08 System Information (SI) encoding and decoding
 * 3GPP TS 04.08 version 7.21.0 Release 1998 / ETSI TS 100 940 V7.21.0 */

/* (C) 2008-2009 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 <errno.h>
#include <string.h>
#include <sys/types.h>
#include <netinet/in.h>

#include <openbsc/gsm_04_08.h>
#include <openbsc/gsm_data.h>
#include <openbsc/abis_rsl.h>
#include <openbsc/rest_octets.h>

#define GSM48_CELL_CHAN_DESC_SIZE	16
#define GSM_MACBLOCK_LEN 		23
#define GSM_MACBLOCK_PADDING		0x2b

static int cchan_list_bm0_set_arfcn(u_int8_t *chan_list, unsigned int arfcn)
{
	unsigned int byte, bit;

	if (arfcn > 124)
		return -EINVAL;

	byte = arfcn / 8;
	bit = arfcn % 8;

	chan_list[GSM48_CELL_CHAN_DESC_SIZE-byte] |= (1 << bit);

	return 0;
}

static int cchan_list_bmrel_set_arfcn(u_int8_t *chan_list, unsigned int arfcn)
{
	unsigned int byte, bit;
	unsigned int min_arfcn;
	unsigned int bitno;

	min_arfcn = (chan_list[0] & 1) << 9;
	min_arfcn |= chan_list[1] << 1;
	min_arfcn |= (chan_list[2] >> 7) & 1;

	/* The lower end of our bitmaks is always implicitly included */
	if (arfcn == min_arfcn)
		return 0;

	if (arfcn < min_arfcn)
		return -EINVAL;
	if (arfcn > min_arfcn + 111)
		return -EINVAL;

	bitno = (arfcn - min_arfcn);
	byte = bitno / 8;
	bit = bitno % 8;

	chan_list[2 + byte] |= 1 << (7 - bit);

	return 0;
}

/* generate a cell channel list as per Section 10.5.2.1b of 04.08 */
static int generate_cell_chan_list(u_int8_t *chan_list, const struct gsm_bts *bts)
{
	struct gsm_bts_trx *trx;
	int rc, min = 1024, max = 0;

	memset(chan_list, 0, 16);

	/* GSM900-only handsets only support 'bit map 0 format' */
	if (bts->band == GSM_BAND_900) {
		chan_list[0] = 0;
		llist_for_each_entry(trx, &bts->trx_list, list) {
			rc = cchan_list_bm0_set_arfcn(chan_list, trx->arfcn);
			if (rc < 0)
				return rc;
		}
		return 0;
	}

	/* We currently only support the 'Variable bitmap format' */
	chan_list[0] = 0x8e;

	llist_for_each_entry(trx, &bts->trx_list, list) {
		if (trx->arfcn < min)
			min = trx->arfcn;
		if (trx->arfcn > max)
			max = trx->arfcn;
	}

	if ((max - min) > 111)
		return -EINVAL;

	chan_list[0] |= (min >> 9) & 1;
	chan_list[1] = (min >> 1);
	chan_list[2] = (min & 1) << 7;

	llist_for_each_entry(trx, &bts->trx_list, list) {
		rc = cchan_list_bmrel_set_arfcn(chan_list, trx->arfcn);
		if (rc < 0)
			return rc;
	}

	return 0;
}

/* generate a cell channel list as per Section 10.5.2.1b of 04.08 */
static int generate_bcch_chan_list(u_int8_t *chan_list, const struct gsm_bts *bts)
{
	struct gsm_bts *cur_bts;
	struct gsm_bts_trx *trx;
	int rc, min = 1024, max = 0;

	memset(chan_list, 0, 16);

	/* GSM900-only handsets only support 'bit map 0 format' */
	if (bts->band == GSM_BAND_900) {
		chan_list[0] = 0;
		llist_for_each_entry(cur_bts, &bts->list, list) {
			trx = cur_bts->c0;
			rc = cchan_list_bm0_set_arfcn(chan_list, trx->arfcn);
			if (rc < 0)
				return rc;
		}
		return 0;
	}

	/* We currently only support the 'Variable bitmap format' */
	chan_list[0] = 0x8e;

	llist_for_each_entry(cur_bts, &bts->list, list) {
		if (&cur_bts->list == &bts->network->bts_list)
			continue;
		trx = cur_bts->c0;
		if (trx->arfcn < min)
			min = trx->arfcn;
		if (trx->arfcn > max)
			max = trx->arfcn;
	}

	if ((max - min) > 111)
		return -EINVAL;

	chan_list[0] |= (min >> 9) & 1;
	chan_list[1] = (min >> 1);
	chan_list[2] = (min & 1) << 7;

	llist_for_each_entry(cur_bts, &bts->list, list) {
		if (&cur_bts->list == &bts->network->bts_list)
			continue;
		trx = cur_bts->c0;
		rc = cchan_list_bmrel_set_arfcn(chan_list, trx->arfcn);
		if (rc < 0)
			return rc;
	}

	return 0;
}

static int generate_si1(u_int8_t *output, const struct gsm_bts *bts)
{
	int rc;
	struct gsm48_system_information_type_1 *si1 =
		(struct gsm48_system_information_type_1 *) output;

	memset(si1, GSM_MACBLOCK_PADDING, GSM_MACBLOCK_LEN);

	si1->header.l2_plen = (21 << 2) | 1;
	si1->header.rr_protocol_discriminator = GSM48_PDISC_RR;
	si1->header.skip_indicator = 0;
	si1->header.system_information = GSM48_MT_RR_SYSINFO_1;

	rc = generate_cell_chan_list(si1->cell_channel_description, bts);
	if (rc < 0)
		return rc;

	si1->rach_control = bts->si_common.rach_control;

	/* SI1 Rest Octets (10.5.2.32), contains NCH position */
	rest_octets_si1(si1->rest_octets, NULL);

	return GSM_MACBLOCK_LEN;
}

static int generate_si2(u_int8_t *output, const struct gsm_bts *bts)
{
	int rc;
	struct gsm48_system_information_type_2 *si2 =
		(struct gsm48_system_information_type_2 *) output;

	memset(si2, GSM_MACBLOCK_PADDING, GSM_MACBLOCK_LEN);

	si2->header.l2_plen = (22 << 2) | 1;
	si2->header.rr_protocol_discriminator = GSM48_PDISC_RR;
	si2->header.skip_indicator = 0;
	si2->header.system_information = GSM48_MT_RR_SYSINFO_2;

	rc = generate_bcch_chan_list(si2->bcch_frequency_list, bts);
	if (rc < 0)
		return rc;

	si2->ncc_permitted = bts->si_common.ncc_permitted;
	si2->rach_control = bts->si_common.rach_control;

	return GSM_MACBLOCK_LEN;
}

struct gsm48_si_ro_info si_info = {
	.selection_params = {
		.present = 0,
	},
	.power_offset = {
		.present = 0,
	},
	.si2ter_indicator = 0,
	.early_cm_ctrl = 1,
	.scheduling = {
		.present = 0,
	},
	.gprs_ind = {
		.si13_position = 0,
		.ra_colour = 0,
		.present = 0,
	},
	.lsa_params = {
		.present = 0,
	},
	.cell_id = 0,	/* FIXME: doesn't the bts have this? */
	.break_ind = 0,
};

static int generate_si3(u_int8_t *output, const struct gsm_bts *bts)
{
	struct gsm48_system_information_type_3 *si3 =
		(struct gsm48_system_information_type_3 *) output;

	memset(si3, GSM_MACBLOCK_PADDING, GSM_MACBLOCK_LEN);

	si3->header.l2_plen = (18 << 2) | 1;
	si3->header.rr_protocol_discriminator = GSM48_PDISC_RR;
	si3->header.skip_indicator = 0;
	si3->header.system_information = GSM48_MT_RR_SYSINFO_3;

	si3->cell_identity = htons(bts->cell_identity);
	gsm0408_generate_lai(&si3->lai, bts->network->country_code,
			     bts->network->network_code,
			     bts->location_area_code);
	si3->control_channel_desc = bts->si_common.chan_desc;
	si3->cell_options = bts->si_common.cell_options;
	si3->cell_sel_par = bts->si_common.cell_sel_par;
	si3->rach_control = bts->si_common.rach_control;

	/* SI3 Rest Octets (10.5.2.34), containing
		CBQ, CELL_RESELECT_OFFSET, TEMPORARY_OFFSET, PENALTY_TIME
		Power Offset, 2ter Indicator, Early Classmark Sending,
		Scheduling if and WHERE, GPRS Indicator, SI13 position */
	rest_octets_si3(si3->rest_octets, &si_info);

	return GSM_MACBLOCK_LEN;
}

static int generate_si4(u_int8_t *output, const struct gsm_bts *bts)
{
	struct gsm48_system_information_type_4 *si4 =
		(struct gsm48_system_information_type_4 *) output;

	/* length of all IEs present except SI4 rest octets and l2_plen */
	int l2_plen = sizeof(*si4) - 1;

	memset(si4, GSM_MACBLOCK_PADDING, GSM_MACBLOCK_LEN);

	si4->header.rr_protocol_discriminator = GSM48_PDISC_RR;
	si4->header.skip_indicator = 0;
	si4->header.system_information = GSM48_MT_RR_SYSINFO_4;

	gsm0408_generate_lai(&si4->lai, bts->network->country_code,
			     bts->network->network_code,
			     bts->location_area_code);
	si4->cell_sel_par = bts->si_common.cell_sel_par;
	si4->rach_control = bts->si_common.rach_control;

	/* Optional: CBCH Channel Description + CBCH Mobile Allocation */

	si4->header.l2_plen = (l2_plen << 2) | 1;

	/* SI4 Rest Octets (10.5.2.35), containing
		Optional Power offset, GPRS Indicator,
		Cell Identity, LSA ID, Selection Parameter */
	rest_octets_si4(si4->data, &si_info);

	return GSM_MACBLOCK_LEN;
}

static int generate_si5(u_int8_t *output, const struct gsm_bts *bts)
{
	struct gsm48_system_information_type_5 *si5 =
		(struct gsm48_system_information_type_5 *) output;
	int rc;

	memset(si5, GSM_MACBLOCK_PADDING, GSM_MACBLOCK_LEN);

	/* l2 pseudo length, not part of msg: 18 */
	si5->rr_protocol_discriminator = GSM48_PDISC_RR;
	si5->skip_indicator = 0;
	si5->system_information = GSM48_MT_RR_SYSINFO_5;
	rc = generate_bcch_chan_list(si5->bcch_frequency_list, bts);
	if (rc < 0)
		return rc;

	/* 04.08 9.1.37: L2 Pseudo Length of 18 */
	return 18;
}

static int generate_si6(u_int8_t *output, const struct gsm_bts *bts)
{
	struct gsm48_system_information_type_6 *si6 =
		(struct gsm48_system_information_type_6 *) output;

	memset(si6, GSM_MACBLOCK_PADDING, GSM_MACBLOCK_LEN);

	/* l2 pseudo length, not part of msg: 11 */
	si6->rr_protocol_discriminator = GSM48_PDISC_RR;
	si6->skip_indicator = 0;
	si6->system_information = GSM48_MT_RR_SYSINFO_6;
	si6->cell_identity = htons(bts->cell_identity);
	gsm0408_generate_lai(&si6->lai, bts->network->country_code,
			     bts->network->network_code,
			     bts->location_area_code);
	si6->cell_options = bts->si_common.cell_options;
	si6->ncc_permitted = bts->si_common.ncc_permitted;

	/* SI6 Rest Octets: 10.5.2.35a: PCH / NCH info, VBS/VGCS options */

	return 18;
}

static struct gsm48_si13_info si13_default = {
	.cell_opts = {
		.nmo 		= GPRS_NMO_III,
		.t3168		= 1000,
		.t3192		= 1000,
		.drx_timer_max	= 1,
		.bs_cv_max	= 15,
	},
	.pwr_ctrl_pars = {
		.alpha		= 10,	/* a = 1.0 */
		.t_avg_w	= 25,
		.t_avg_t	= 25,
		.pc_meas_chan	= 0, 	/* downling measured on CCCH */
		.n_avg_i	= 15,
	},
	.bcch_change_mark	= 0,
	.si_change_field	= 0,
	.pbcch_present		= 0,
	{
		.no_pbcch = {
			.rac		= 0,
			.spgc_ccch_sup 	= 0,
			.net_ctrl_ord	= 0,
			.prio_acc_thr	= 0,
		},
	},
};

static int generate_si13(u_int8_t *output, const struct gsm_bts *bts)
{
	struct gsm48_system_information_type_13 *si13 =
		(struct gsm48_system_information_type_13 *) output;
	int ret;

	memset(si13, GSM_MACBLOCK_PADDING, GSM_MACBLOCK_LEN);

	si13->header.rr_protocol_discriminator = GSM48_PDISC_RR;
	si13->header.skip_indicator = 0;
	si13->header.system_information = GSM48_MT_RR_SYSINFO_13;

	ret = rest_octets_si13(si13->rest_octets, &si13_default);
	if (ret < 0)
		return ret;

	si13->header.l2_plen = ret & 0xff;

	return GSM_MACBLOCK_LEN;
}

int gsm_generate_si(u_int8_t *output, struct gsm_bts *bts, int type)
{
	switch (type) {
	case RSL_SYSTEM_INFO_1:
		return generate_si1(output, bts);
	case RSL_SYSTEM_INFO_2:
		return generate_si2(output, bts);
	case RSL_SYSTEM_INFO_3:
		return generate_si3(output, bts);
	case RSL_SYSTEM_INFO_4:
		return generate_si4(output, bts);
	case RSL_SYSTEM_INFO_5:
		return generate_si5(output, bts);
	case RSL_SYSTEM_INFO_6:
		return generate_si6(output, bts);
	case RSL_SYSTEM_INFO_13:
		return generate_si13(output, bts);
	default:
		return -EINVAL;
	}

	return 0;
}