/*
  Copyright (c) 2012, Matthias Schiffer <mschiffer@universe-factory.net>
  All rights reserved.

  Redistribution and use in source and binary forms, with or without
  modification, are permitted provided that the following conditions are met:

    1. Redistributions of source code must retain the above copyright notice,
       this list of conditions and the following disclaimer.
    2. Redistributions in binary form must reproduce the above copyright notice,
       this list of conditions and the following disclaimer in the documentation
       and/or other materials provided with the distribution.

  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
  AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
  DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
  FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
  SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
  CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
  OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/


#include "ffd.h"
#include "neigh.h"
#include "netif.h"
#include "packet.h"
#include "queue.h"
#include "send.h"
#include "tlv.h"
#include "tlv_types.h"

#include <errno.h>
#include <poll.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

#include <netpacket/packet.h>

#include <sys/socket.h>


const eth_addr_t ffd_addr = {{0x03, 0x00, 0x00, 0x00, 0x0f, 0xfd}};


static char *mesh = "bat0";

int sockfd;
struct timespec now;

static ffd_queue_t *tasks = NULL;

ffd_node_id_t self;
ffd_iface_t *iface_list = NULL;
ffd_announce_t *announce_list = NULL;


static inline bool use_netif(const char *ifname) {
	char *if_mesh = netif_get_mesh(ifname);
	bool ret = (if_mesh && !strcmp(if_mesh, mesh));
	free(if_mesh);

	return ret;
}

static void update_time(void) {
	clock_gettime(CLOCK_MONOTONIC, &now);
}

static bool check_config(void) {
	if (!netif_is_mesh(mesh)) {
		fprintf(stderr, "error: configured interface is no mesh\n");
		return false;
	}

	return true;
}

static bool init_self(void) {
	eth_addr_t primary_addr = netif_mesh_get_primary_addr(mesh);
	if (is_eth_addr_unspec(&primary_addr))
		return false;

	self.id[0] = primary_addr.d[0]^0x02;
	self.id[1] = primary_addr.d[1];
	self.id[2] = primary_addr.d[2];
	self.id[3] = 0xff;
	self.id[4] = 0xfe;
	self.id[5] = primary_addr.d[3];
	self.id[6] = primary_addr.d[4];
	self.id[7] = primary_addr.d[5];

	ffd_announce_t *announce = ffd_announce_new();

	announce->node = self;
	announce->type = 1;
	announce->key = 1337;

	announce->nexthop_list = announce->selected = calloc(1, sizeof(ffd_nexthop_t));

	return true;
}

static bool init_socket(void) {
	sockfd = socket(AF_PACKET, SOCK_DGRAM, htons(FFD_PROTO));
	if (sockfd < 0) {
		fprintf(stderr, "error: socket: %m\n");
		return false;
	}

	return true;
}

static inline ffd_iface_t* get_iface(unsigned ifindex) {
	ffd_iface_t *iface;
	for (iface = iface_list; iface; iface = iface->next) {
		if (iface->ifindex == ifindex)
			return iface;
	}

	return NULL;
}

static void update_netif(const char *ifname, unsigned ifindex, void *arg) {
	if (!use_netif(ifname))
		return;

	/* join multicast group */
	struct packet_mreq mr;
	memset(&mr, 0, sizeof(mr));
	mr.mr_ifindex = ifindex;
	mr.mr_type = PACKET_MR_MULTICAST;
	mr.mr_alen = ETH_ALEN;
	memcpy(mr.mr_address, ffd_addr.d, ETH_ALEN);
	if (setsockopt(sockfd, SOL_PACKET, PACKET_ADD_MEMBERSHIP, &mr, sizeof(mr)) && errno != EADDRINUSE)
		fprintf(stderr, "warning: setsockopt: %m\n");

	ffd_iface_t *iface = get_iface(ifindex);

	if (!iface) {
		/* new iface */
		iface = malloc(sizeof(ffd_iface_t));
		iface->next = iface_list;
		iface_list = iface;

		iface->seqno = 0;
		iface->neigh_list = NULL;
	}

	iface->ifindex = ifindex;
	strncpy(iface->name, ifname, IF_NAMESIZE);
	iface->type = netif_get_type(ifname);
	iface->addr = netif_get_eth_addr(ifname);
}

static void update_netifs(void) {
	ffd_iface_t *iface, **cur;

	for (iface = iface_list; iface; iface = iface->next)
		iface->type = IF_UNSPEC;

	netif_foreach(update_netif, NULL);

	cur = &iface_list;
	while (*cur) {
		iface = *cur;

		if (iface->type == IF_UNSPEC) {
			*cur = iface->next;
			ffd_neigh_unref_list(iface->neigh_list);
			free(iface);
		}
		else {
			cur = &iface->next;
		}
	}
}

typedef struct _handle_tlv_arg_t {
	ffd_iface_t *iface;
	const eth_addr_t *addr;

	ffd_node_id_t node_id;
} handle_tlv_arg_t;

static inline ffd_neigh_t* get_tlv_neigh(handle_tlv_arg_t *arg) {
	return ffd_neigh_get(arg->iface, arg->addr);
}

static void handle_tlv_ack_req(const ffd_tlv_ack_req_t *tlv_req, size_t len, handle_tlv_arg_t *arg) {
	if (len < sizeof(ffd_tlv_ack_req_t)) {
		fprintf(stderr, "warn: received short acknowledement request TLV.\n");
		return;
	}

	ffd_neigh_t *neigh = get_tlv_neigh(arg);

	ffd_send_ack(neigh, ntohs(tlv_req->nonce));
}

static void handle_tlv_ack(const ffd_tlv_ack_t *tlv_ack, size_t len, handle_tlv_arg_t *arg) {
	if (len < sizeof(ffd_tlv_ack_t)) {
		fprintf(stderr, "warn: received short acknowledement TLV.\n");
		return;
	}

	ffd_ack_handle(ntohs(tlv_ack->nonce));
}

static void handle_tlv_hello(const ffd_tlv_hello_t *tlv_hello, size_t len, handle_tlv_arg_t *arg) {
	if (len < sizeof(ffd_tlv_hello_t)) {
		fprintf(stderr, "warn: received short hello TLV.\n");
		return;
	}

	fprintf(stderr, "debug: received hello with seqno %u.\n", ntohs(tlv_hello->seqno));

	ffd_neigh_t *neigh = get_tlv_neigh(arg);

	uint16_t seqno = ntohs(tlv_hello->seqno);

	if (neigh->last_hello.tv_sec) {
		int timediff = timespec_diff(&now, &neigh->last_hello);
		uint16_t seqexp = neigh->last_seqno + (timediff - neigh->hello_interval/2)/neigh->hello_interval;

		/* cast to int16_t to ensure correct handling of seqno wrapping */
		if (abs((int16_t)(seqno - seqexp)) > 16) {
			fprintf(stderr, "info: neighbour was reset.\n");
			neigh->hello_log = 0;
			neigh->txcost = 0xffff;
		}
		else {
			int16_t seqdiff = seqno - neigh->last_seqno;
			if (seqdiff <= 0) {
				fprintf(stderr, "debug: seqno already seen, ignoring.\n");
				return;
			}

			neigh->hello_log <<= seqdiff;
		}
	}
	else {
		fprintf(stderr, "info: received hello from new neighbour.\n");
	}

	neigh->hello_log |= 1;
	neigh->hello_interval = ntohs(tlv_hello->interval);
	neigh->last_seqno = seqno;
	neigh->last_hello = now;

	if (neigh->hello_log == 1) /* new or reset neighbour */
		ffd_neigh_reset(arg->iface, neigh);

	fprintf(stderr, "debug: accepted hello, log %04x, rxcost is %u, cost is %u now.\n", neigh->hello_log, ffd_neigh_get_rxcost(neigh), ffd_neigh_get_cost(neigh));
}

static void handle_tlv_ihu(const ffd_tlv_ihu_t *tlv_ihu, size_t len, handle_tlv_arg_t *arg) {
	if (len < sizeof(ffd_tlv_ihu_t)) {
		fprintf(stderr, "warn: received short IHU TLV.\n");
		return;
	}

	if (tlv_ihu->ae == ADDR_ENC_ETH) {
		if (len < sizeof(ffd_tlv_ihu_t)+sizeof(eth_addr_t)) {
			fprintf(stderr, "warn: received short IHU TLV.\n");
			return;
		}

		if (memcmp(tlv_ihu->address, &arg->iface->addr, sizeof(eth_addr_t)) != 0)
			return;
	}
	else if (tlv_ihu->ae != ADDR_ENC_UNSPEC) {
		return;
	}

	ffd_neigh_t *neigh = get_tlv_neigh(arg);
	neigh->ihu_interval = ntohs(tlv_ihu->interval);
	neigh->last_ihu = now;
	neigh->txcost = ntohs(tlv_ihu->rxcost);

	fprintf(stderr, "debug: accepted IHU, txcost is %u, cost is %u now.\n", ffd_neigh_get_txcost(neigh), ffd_neigh_get_cost(neigh));
}

static void handle_tlv_node_id(const ffd_tlv_node_id_t *tlv_node_id, size_t len, handle_tlv_arg_t *arg) {
	if (len < sizeof(ffd_tlv_node_id_t)) {
		fprintf(stderr, "warn: received short node id TLV.\n");
		return;
	}

	arg->node_id = tlv_node_id->id;
}

static void handle_tlv_update(const ffd_tlv_update_t *tlv_update, size_t len, handle_tlv_arg_t *arg) {
	if (len < sizeof(ffd_tlv_update_t)) {
		fprintf(stderr, "warn: received short update TLV.\n");
		return;
	}

	if (ffd_is_node_id_unspec(&arg->node_id)) {
		fprintf(stderr, "warn: received update TLV without node id TLV.\n");
		return;
	}

	if (ffd_are_node_ids_equal(&arg->node_id, &self)) {
		fprintf(stderr, "debug: update source is myself.\n");
		return;
	}

	fprintf(stderr, "debug: update received from %04x%04x.\n", ntohl(*(uint32_t*)arg->node_id.id), ntohl(*(uint32_t*)(arg->node_id.id+4)));

	ffd_announce_t *announce = ffd_announce_get(&arg->node_id, ntohs(tlv_update->type), ntohs(tlv_update->key));
	ffd_metric_seqno_t ms = { ntohs(tlv_update->metric), ntohs(tlv_update->seqno) };
	bool feasible = ffd_is_feasible(announce, ms);

	ffd_neigh_t *neigh = get_tlv_neigh(arg);
	ffd_nexthop_t *nexthop = ffd_announce_nexthop_find(announce, neigh);

	if (!nexthop) {
		if (feasible && tlv_update->metric != 0xffff /* no need to ntohs */)
			nexthop = ffd_announce_nexthop_new(announce, neigh);
	}
	else {
		if (!feasible && nexthop == announce->selected) {
			ffd_send_seqno_request_for(neigh, announce);
			nexthop = NULL;
		}
	}

	if (!feasible && nexthop && nexthop != announce->selected) {
		if (ms.metric + ffd_neigh_get_cost(neigh) < announce->metric.metric)
			ffd_send_seqno_request_for(neigh, announce);
	}

	if ((tlv_update->flags & FFD_UPDATE_WITH_DATA) && !announce->data) {
		if (len > sizeof(ffd_tlv_update_t)) {
			announce->len = len - sizeof(ffd_tlv_update_t);
			announce->data = malloc(announce->len);
			memcpy(announce->data, tlv_update->data, announce->len);
		}
		else {
			announce->len = 0xff;

			/* request data */
			if (nexthop)
				ffd_send_announce_request(arg->iface, neigh, announce->node, announce->type, announce->key, true);
		}
	}

	if (!nexthop)
		return;

	fprintf(stderr, "debug: the update was accepted.\n");

	ffd_announce_update_nexthop(announce, nexthop, ms, ntohs(tlv_update->interval));
}

static void handle_tlv_announce_req(const ffd_tlv_announce_req_t *tlv_req, size_t len, handle_tlv_arg_t *arg) {
	if (len < sizeof(ffd_tlv_announce_req_t)) {
		fprintf(stderr, "warn: received short announce request TLV.\n");
		return;
	}

	fprintf(stderr, "debug: received announce request\n");

	if (ffd_is_node_id_unspec(&tlv_req->node)) {
		ffd_send_update(NULL, get_tlv_neigh(arg), NULL, tlv_req->flags & FFD_UPDATE_WITH_DATA);
	}
	else {
		ffd_announce_t *announce = ffd_announce_find(&tlv_req->node, ntohs(tlv_req->type), ntohs(tlv_req->key));

		if (announce)
			ffd_send_update(NULL, get_tlv_neigh(arg), announce, tlv_req->flags & FFD_UPDATE_WITH_DATA);
		else
			ffd_send_retract(get_tlv_neigh(arg), tlv_req->node, ntohs(tlv_req->type), ntohs(tlv_req->key));
	}
}

static void handle_tlv_seqno_req(const ffd_tlv_seqno_req_t *tlv_req, size_t len, handle_tlv_arg_t *arg) {
	if (len < sizeof(ffd_tlv_seqno_req_t)) {
		fprintf(stderr, "warn: received short seqno request TLV.\n");
		return;
	}

	ffd_announce_t *announce = ffd_announce_find(&tlv_req->node, ntohs(tlv_req->type), ntohs(tlv_req->key));

	if (!announce) {
		fprintf(stderr, "debug: received seqno request for unknown announce\n");
		return;
	}

	if (!announce->selected) {
		fprintf(stderr, "debug: received seqno request for starved announce\n");
		return;
	}

	ffd_neigh_t *neigh = get_tlv_neigh(arg);

	if (announce->selected->neigh == neigh)
		return;

	uint16_t seqno = ntohs(tlv_req->seqno);

	if ((int16_t)(seqno-announce->selected->metric_seqno.seqno) <= 0) {
		fprintf(stderr, "debug: received seqno request, seqno already ok\n");
		ffd_update_enqueue(&announce->node, announce->type, announce->key, neigh, true);
		return;
	}

	if (!announce->selected->neigh) {
		fprintf(stderr, "debug: received seqno request, incrementing seqno\n");
		announce->selected->metric_seqno.seqno++;
		ffd_update_enqueue(&announce->node, announce->type, announce->key, neigh, true);
		return;
	}

	if (ffd_announce_seqno_request(announce, neigh, seqno)) {
		fprintf(stderr, "debug: received seqno request, forwarding\n");
		ffd_send_seqno_request(announce->selected->neigh, announce, seqno);
	}
	else {
		fprintf(stderr, "debug: received seqno request, not forwarding again\n");
	}
}

static void handle_tlv(ffd_tlv_type_t type, const void *data, size_t len, void *arg) {
	switch (type) {
	case TLV_ACK_REQ:
		handle_tlv_ack_req(data, len, arg);
		return;

	case TLV_ACK:
		handle_tlv_ack(data, len, arg);
		return;

	case TLV_HELLO:
		handle_tlv_hello(data, len, arg);
		return;

	case TLV_IHU:
		handle_tlv_ihu(data, len, arg);
		return;

	case TLV_NODE_ID:
		handle_tlv_node_id(data, len, arg);
		return;

	case TLV_UPDATE:
		handle_tlv_update(data, len, arg);
		return;

	case TLV_ANNOUNCE_REQ:
		handle_tlv_announce_req(data, len, arg);
		return;

	case TLV_SEQNO_REQ:
		handle_tlv_seqno_req(data, len, arg);
		return;

	default:
		fprintf(stderr, "debug: received unknown TLV %u on %s.\n", type, ((handle_tlv_arg_t*)arg)->iface->name);
		return;
	}
}

static void receive_packet(void) {
	ffd_packet_t *packet = alloca(sizeof(ffd_packet_t)+FFD_PACKET_MAX);
	struct sockaddr_ll from;
	socklen_t fromlen = sizeof(from);

	ssize_t readlen = recvfrom(sockfd, packet, sizeof(ffd_packet_t)+FFD_PACKET_MAX, 0, (struct sockaddr*)&from, &fromlen);

	if (readlen < 0) {
		fprintf(stderr, "error: recvfrom: %m\n");
		return;
	}

	if (from.sll_halen != ETH_ALEN) {
		fprintf(stderr, "error: receive_packet: strange address length\n");
		return;
	}

	if (readlen < sizeof(ffd_packet_t) || readlen < sizeof(ffd_packet_t)+ntohs(packet->len)) {
		fprintf(stderr, "debug: received short packet.\n");
		return;
	}

	handle_tlv_arg_t arg = { .iface = get_iface(from.sll_ifindex), .addr = (const eth_addr_t*)&from.sll_addr };

	if (!arg.iface)
		return;

	if (!ffd_tlv_parse(packet, handle_tlv, &arg)) {
		fprintf(stderr, "debug: received invalid packet.\n");
	}
}

static void send_updates(void) {
	fprintf(stderr, "debug: sending periodic updates.\n");

	ffd_iface_t *iface;
	for (iface = iface_list; iface; iface = iface->next) {
		ffd_send_update(iface, NULL, NULL, false);
	}
}

static void maintenance(void) {
	update_netifs();

	ffd_iface_t *iface;
	for (iface = iface_list; iface; iface = iface->next) {
		ffd_neigh_t **cur, **next;
		for (cur = &iface->neigh_list; *cur; cur = next) {
			ffd_neigh_t *neigh = *cur;
			next = &neigh->next;

			if (ffd_neigh_get_rxcost(neigh) == 0xffff && ffd_neigh_get_txcost(neigh) == 0xffff && !neigh->ref) {
				*cur = *next;
				next = cur;
				free(neigh);

				continue;
			}

			fprintf(stderr, "debug: maintenance: %02x:%02x:%02x:%02x:%02x:%02x[%s]: %u (rx %u/tx %u)\n",
				neigh->addr.d[0], neigh->addr.d[1], neigh->addr.d[2],
				neigh->addr.d[3], neigh->addr.d[4], neigh->addr.d[5],
				iface->name, ffd_neigh_get_cost(neigh), ffd_neigh_get_rxcost(neigh), ffd_neigh_get_txcost(neigh));
		}
	}

	ffd_announce_t **cur, **next;
	for (cur = &announce_list; *cur; cur = next) {
		ffd_announce_t *announce = *cur;
		next = &announce->next;

		ffd_announce_update(announce);

		if (!announce->nexthop_list) {
			*cur = *next;
			next = cur;
			ffd_announce_free(announce);

			continue;
		}

		fprintf(stderr, "debug: node %04x%04x, type %04x, announce %04x (%u, seqno=%04x):\n",
			ntohl(*(uint32_t*)announce->node.id), ntohl(*(uint32_t*)(announce->node.id+4)), announce->type, announce->key, announce->metric.metric, announce->metric.seqno);

		ffd_nexthop_t *nexthop;
		for (nexthop = announce->nexthop_list; nexthop; nexthop = nexthop->next) {
			ffd_neigh_t *neigh = nexthop->neigh;

			if (!neigh) {
				fprintf(stderr, "\tlocal\n");
				continue;
			}

			fprintf(stderr, "\tnexthop: %02x:%02x:%02x:%02x:%02x:%02x[%s] (%u, seqno=%04x, cost=%u%s)\n",
				neigh->addr.d[0], neigh->addr.d[1], neigh->addr.d[2],
				neigh->addr.d[3], neigh->addr.d[4], neigh->addr.d[5],
				neigh->iface ? neigh->iface->name : NULL,
				nexthop->metric_seqno.metric, nexthop->metric_seqno.seqno, ffd_neigh_get_cost(neigh),
				(nexthop == announce->selected) ? ", selected" : "");
		}
	}
}


typedef struct _periodic_task_info {
	void (*handle)(void);
	unsigned delay;
	unsigned interval;
} periodic_task_info;


static const periodic_task_info periodic_tasks [] = {
	{maintenance, 0, FFD_MAINTENANCE_INTERVAL},
	{ffd_send_hellos, FFD_HELLO_INTERVAL, FFD_HELLO_INTERVAL},
	{send_updates, 1, FFD_UPDATE_INTERVAL},
	{NULL}
};


static void handle_periodic_task(const struct timespec *timeout, void *arg) {
	const periodic_task_info *info = arg;

	info->handle();
	ffd_queue_put_delayed(&tasks, handle_periodic_task, timeout, info->interval, arg);
}

static void register_periodic_tasks(void) {
	const periodic_task_info *info;
	for (info = periodic_tasks; info->handle; info++)
		ffd_queue_put_delayed(&tasks, handle_periodic_task, &now, info->delay, (void*)info);
}


static inline int timeout_min(int a, int b) {
	if (a < 0)
		return b;
	else if (b < 0)
		return a;
	else
		return min(a, b);
}


int main() {
	if (!check_config())
		return 1;

	if (!init_self())
		return 1;

	if (!init_socket())
		return 1;

	update_time();
	register_periodic_tasks();

	while (true) {
		ffd_queue_run(&tasks);
		ffd_update_run();
		ffd_ack_run();

		struct pollfd fds[1];

		int timeout = 10*timeout_min(timeout_min(ffd_queue_timeout(&tasks), ffd_update_timeout()), ffd_ack_timeout());
		if (timeout < 0)
			timeout = -1;

		fds[0].fd = sockfd;
		fds[0].events = POLLIN;

		poll(fds, 1, timeout);

		update_time();

		if (fds[0].revents & POLLIN)
			receive_packet();
	}

	return 0;
}