/*
 * (C) 2021-2022 by sysmocom - s.f.m.c. GmbH <info@sysmocom.de>
 * All Rights Reserved.
 *
 * Author: Neels Janosch Hofmeyr <nhofmeyr@sysmocom.de>
 *
 * SPDX-License-Identifier: GPL-2.0+
 *
 *  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, see <http://www.gnu.org/licenses/>.
 *
 */

#include <osmocom/core/utils.h>
#include <osmocom/core/talloc.h>
#include <osmocom/core/sockaddr_str.h>

#include <osmocom/pfcp/pfcp_endpoint.h>

#include <osmocom/upf/upf.h>
#include <osmocom/upf/up_endpoint.h>
#include <osmocom/upf/up_peer.h>
#include <osmocom/upf/up_session.h>
#include <osmocom/upf/up_gtp_action.h>
#include <osmocom/upf/upf_gtp.h>

struct g_upf *g_upf = NULL;

struct osmo_tdef_group g_upf_tdef_groups[] = {
	{ "pfcp", "PFCP endpoint timers", osmo_pfcp_tdefs, },
	{}
};

void g_upf_alloc(void *ctx)
{
	OSMO_ASSERT(g_upf == NULL);
	g_upf = talloc_zero(ctx, struct g_upf);

	*g_upf = (struct g_upf){
		.pfcp = {
			.vty_cfg = {
				.local_addr = talloc_strdup(g_upf, UPF_PFCP_LISTEN_DEFAULT),
				.local_port = OSMO_PFCP_PORT,
			},
		},
		.tunmap = {
			.priority_pre = -300,
			.priority_post = 400,
		},
		.tunend = {
			/* TODO: recovery count state file; use lower byte of current time, poor person's random. */
			.recovery_count = time(NULL),
		},
	};

	INIT_LLIST_HEAD(&g_upf->tunend.vty_cfg.devs);
	INIT_LLIST_HEAD(&g_upf->tunend.devs);
	INIT_LLIST_HEAD(&g_upf->netinst);
}

int upf_pfcp_init(void)
{
	struct osmo_sockaddr_str local_addr_str;
	struct osmo_sockaddr local_addr;

	OSMO_ASSERT(g_upf);
	OSMO_ASSERT(g_upf->pfcp.ep == NULL);

	/* Translate address string from VTY config to osmo_sockaddr: first read into osmo_sockaddr_str, then write to
	 * osmo_sockaddr. */
	osmo_sockaddr_str_from_str(&local_addr_str, g_upf->pfcp.vty_cfg.local_addr, g_upf->pfcp.vty_cfg.local_port);
	osmo_sockaddr_str_to_sockaddr(&local_addr_str, &local_addr.u.sas);

	g_upf->pfcp.ep = up_endpoint_alloc(g_upf, &local_addr);
	if (!g_upf->pfcp.ep) {
		fprintf(stderr, "Failed to allocate PFCP endpoint.\n");
		return -1;
	}
	return 0;
}

int upf_pfcp_listen(void)
{
	int rc;
	if (!g_upf->pfcp.ep) {
		rc = upf_pfcp_init();
		if (rc)
			return rc;
	}

	rc = up_endpoint_bind(g_upf->pfcp.ep);
	if (rc) {
		LOGP(DLPFCP, LOGL_ERROR, "PFCP: failed to listen on %s\n",
		     osmo_sockaddr_to_str_c(OTC_SELECT, osmo_pfcp_endpoint_get_local_addr(g_upf->pfcp.ep->pfcp_ep)));
		return rc;
	}
	LOGP(DLPFCP, LOGL_NOTICE, "PFCP: Listening on %s\n",
	     osmo_sockaddr_to_str_c(OTC_SELECT, osmo_pfcp_endpoint_get_local_addr(g_upf->pfcp.ep->pfcp_ep)));
	return 0;
}

int upf_gtp_devs_open()
{
	struct tunend_vty_cfg *c = &g_upf->tunend.vty_cfg;
	struct tunend_vty_cfg_dev *d;

	llist_for_each_entry(d, &c->devs, entry) {
		if (upf_gtp_dev_open(d->dev_name, d->create, d->local_addr, false, false))
			return -1;
	}
	return 0;
}

static bool upf_is_local_teid_in_use(uint32_t teid)
{
	struct up_peer *peer;
	llist_for_each_entry(peer, &g_upf->pfcp.ep->peers, entry) {
		struct up_session *session = up_session_find_by_local_teid(peer, teid);
		if (session)
			return true;
	}
	return false;
}

static uint32_t upf_next_local_teid_inc(void)
{
	g_upf->gtp.next_local_teid_state++;
	if (!g_upf->gtp.next_local_teid_state)
		g_upf->gtp.next_local_teid_state++;
	return g_upf->gtp.next_local_teid_state;
}

uint32_t upf_next_local_teid(void)
{
	uint32_t sanity;
	for (sanity = 2342; sanity; sanity--) {
		uint32_t next_teid = upf_next_local_teid_inc();
		if (upf_is_local_teid_in_use(next_teid))
			continue;
		return next_teid;
	}
	return 0;
}

static uint32_t upf_next_chain_id_inc(void)
{
	g_upf->tunmap.next_chain_id_state++;
	if (!g_upf->tunmap.next_chain_id_state)
		g_upf->tunmap.next_chain_id_state++;
	return g_upf->tunmap.next_chain_id_state;
}

/* Return an unused chain_id, or 0 if none is found with sane effort. */
uint32_t upf_next_chain_id(void)
{
	uint32_t sanity;

	/* Make sure the new chain_id is not used anywhere */
	for (sanity = 2342; sanity; sanity--) {
		struct up_peer *peer;
		uint32_t chain_id = upf_next_chain_id_inc();
		bool taken = false;

		if (!g_upf->pfcp.ep)
			return chain_id;

		llist_for_each_entry(peer, &g_upf->pfcp.ep->peers, entry) {
			struct up_session *session;
			int bkt;
			hash_for_each(peer->sessions_by_up_seid, bkt, session, node_by_up_seid) {
				struct up_gtp_action *a;
				llist_for_each_entry(a, &session->active_gtp_actions, entry) {
					if (a->kind != UP_GTP_U_TUNMAP)
						continue;
					if (a->tunmap.access.chain_id == chain_id
					    || a->tunmap.core.chain_id == chain_id) {
						taken = true;
						break;
					}
				}
				if (taken)
					break;
			}
			if (taken)
				break;
		}

		if (!taken)
			return chain_id;
	}

	/* finding a chain_id became insane, return invalid = 0 */
	return 0;
}