/* (C) 2022 by sysmocom - s.f.m.c. GmbH <info@sysmocom.de>
 * Author: Oliver Smith <osmith@sysmocom.de>
 * All Rights Reserved
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU Affero General Public License as published by
 * the Free Software Foundation; either version 3 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 Affero General Public License for more details.
 *
 * You should have received a copy of the GNU Affero General Public License
 * along with this program.  If not, see <http://www.gnu.org/lienses/>.
 *
 */

#include "config.h"
#include <osmocom/core/msgb.h>
#include <osmocom/gsm/gsm0808.h>
#include <osmocom/sigtran/sccp_helpers.h>
#include <osmocom/sigtran/sccp_sap.h>
#include <osmocom/bsc_nat/bsc.h>
#include <osmocom/bsc_nat/bsc_nat.h>
#include <osmocom/bsc_nat/logging.h>
#include <osmocom/bsc_nat/msc.h>

int bssap_tx_reset(struct bsc_nat_sccp_inst *sccp_inst, struct osmo_sccp_addr *addr)
{
	enum bsc_nat_net net = sccp_inst == g_bsc_nat->cn.sccp_inst ? BSC_NAT_NET_CN : BSC_NAT_NET_RAN;

	LOGP(DMAIN, LOGL_NOTICE, "Tx RESET to %s\n", bsc_nat_print_addr(net, addr));

	struct msgb *msg = gsm0808_create_reset();

	return osmo_sccp_tx_unitdata_msg(sccp_inst->scu, &sccp_inst->addr, addr, msg);
}

static int bssap_cn_handle_reset_ack(struct osmo_sccp_addr *addr, struct msgb *msg, unsigned int length)
{
	struct msc *msc = msc_get();

	if (msc->addr.pc != addr->pc) {
		LOGP(DMAIN, LOGL_ERROR, "Unexpected Rx RESET ACK in CN from %s, which is not %s\n",
		     osmo_ss7_pointcode_print(NULL, addr->pc), talloc_get_name(msc));
		return -1;
	}

	LOGP(DMAIN, LOGL_NOTICE, "Rx RESET ACK from %s\n", talloc_get_name(msc));
	msc_rx_reset_ack(msc);

	return 0;
}

static int bssap_cn_rcvmsg_udt(struct osmo_sccp_addr *addr, struct msgb *msg, unsigned int length)
{
	int ret = 0;

	switch (msg->l3h[0]) {
	case BSS_MAP_MSG_RESET_ACKNOWLEDGE:
		ret = bssap_cn_handle_reset_ack(addr, msg, length);
		break;
	default:
		LOGP(DMAIN, LOGL_ERROR, "%s(%s) is not implemented!\n", __func__, gsm0808_bssmap_name(msg->l3h[0]));
		break;
	}

	return ret;
}

static int bssap_ran_handle_reset(struct osmo_sccp_addr *addr, struct msgb *msg, unsigned int length)
{
	struct bsc_nat_sccp_inst *sccp_inst = g_bsc_nat->ran.sccp_inst;
	struct bsc *bsc;

	/* Store the BSC, since RESET was done the BSCNAT should accept its messages */
	bsc = bsc_get_by_pc(addr->pc);
	if (!bsc)
		bsc = bsc_alloc(addr);

	LOGP(DMAIN, LOGL_NOTICE, "Rx RESET from %s\n", bsc_nat_print_addr_ran(addr));

	LOGP(DMAIN, LOGL_NOTICE, "Tx RESET ACK to %s\n", bsc_nat_print_addr_ran(addr));
	msg = gsm0808_create_reset_ack();
	return osmo_sccp_tx_unitdata_msg(sccp_inst->scu, &sccp_inst->addr, addr, msg);
}

static int bssap_ran_rcvmsg_udt(struct osmo_sccp_addr *addr, struct msgb *msg, unsigned int length)
{
	int ret = 0;

	switch (msg->l3h[0]) {
	case BSS_MAP_MSG_RESET:
		ret = bssap_ran_handle_reset(addr, msg, length);
		break;
	default:
		LOGP(DMAIN, LOGL_ERROR, "%s(%s) is not implemented!\n", __func__, gsm0808_bssmap_name(msg->l3h[0]));
		break;
	}

	return ret;
}

static int bssap_rcvmsg_udt(struct bsc_nat_sccp_inst *sccp_inst, struct osmo_sccp_addr *addr, struct msgb *msg,
			    unsigned int length)
{
	if (length < 1) {
		LOGP(DMAIN, LOGL_ERROR, "Not enough room: %u\n", length);
		return -1;
	}

	LOGP(DMAIN, LOGL_NOTICE, "Rx UDT BSSMAP %s\n", gsm0808_bssmap_name(msg->l3h[0]));

	if (sccp_inst == g_bsc_nat->cn.sccp_inst)
		return bssap_cn_rcvmsg_udt(addr, msg, length);
	return bssap_ran_rcvmsg_udt(addr, msg, length);
}

int bssap_handle_udt(struct bsc_nat_sccp_inst *sccp_inst, struct osmo_sccp_addr *addr, struct msgb *msgb,
		      unsigned int length)
{
	struct bssmap_header *bs;
	int rc = -1;

	LOGP(DMAIN, LOGL_DEBUG, "Rx UDT: %s\n", osmo_hexdump(msgb->l2h, length));

	if (length < sizeof(*bs)) {
		LOGP(DMAIN, LOGL_ERROR, "The header is too short\n");
		return -1;
	}

	bs = (struct bssmap_header *)msgb->l2h;
	if (bs->length < length - sizeof(*bs)) {
		LOGP(DMAIN, LOGL_ERROR, "Failed to parse BSSMAP header\n");
		return -1;
	}

	switch (bs->type) {
	case BSSAP_MSG_BSS_MANAGEMENT:
		msgb->l3h = &msgb->l2h[sizeof(*bs)];
		rc = bssap_rcvmsg_udt(sccp_inst, addr, msgb, length - sizeof(*bs));
		break;
	default:
		LOGP(DMAIN, LOGL_ERROR, "%s(%s) is not implemented!\n", __func__, gsm0808_bssap_name(bs->type));
	}

	return rc;
}