/*
  Copyright (c) 2016-2019, 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 "respondd-common.h"

#include <libgluonutil.h>

#include <json-c/json.h>

#include <netlink/netlink.h>
#include <netlink/msg.h>

#include <glob.h>
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

#include <arpa/inet.h>
#include <net/if.h>
#include <netinet/in.h>

#include <linux/if_addr.h>
#include <linux/rtnetlink.h>


struct ip_address_information {
	unsigned int ifindex;
	struct json_object *addresses;
};

static int get_addresses_cb(struct nl_msg *msg, void *arg) {
	struct ip_address_information *info = (struct ip_address_information*) arg;

	struct nlmsghdr *nlh = nlmsg_hdr(msg);
	struct ifaddrmsg *msg_content = NLMSG_DATA(nlh);
	int remaining = nlh->nlmsg_len - NLMSG_LENGTH(sizeof(struct ifaddrmsg));
	struct rtattr *hdr;

	for (hdr = IFA_RTA(msg_content); RTA_OK(hdr, remaining); hdr = RTA_NEXT(hdr, remaining)) {
		char addr_str_buf[INET6_ADDRSTRLEN];

		/* We are only interested in IP-addresses of br-client */
		if (hdr->rta_type != IFA_ADDRESS ||
			msg_content->ifa_index != info->ifindex ||
			msg_content->ifa_flags & (IFA_F_TENTATIVE|IFA_F_DEPRECATED)) {
			continue;
		}

		if (inet_ntop(AF_INET6, (struct in6_addr *) RTA_DATA(hdr), addr_str_buf, INET6_ADDRSTRLEN)) {
			json_object_array_add(info->addresses, json_object_new_string(addr_str_buf));
		}
	}

	return NL_OK;
}

static struct json_object *get_addresses(void) {
	struct ip_address_information info = {
		.ifindex = if_nametoindex("br-client"),
		.addresses = json_object_new_array(),
	};
	int err;

	/* Open socket */
	struct nl_sock *socket = nl_socket_alloc();
	if (!socket) {
		return info.addresses;
	}

	err = nl_connect(socket, NETLINK_ROUTE);
	if (err < 0) {
		goto out_free;
	}

	/* Send message */
	struct ifaddrmsg rt_hdr = { .ifa_family = AF_INET6, };
	err = nl_send_simple(socket, RTM_GETADDR, NLM_F_REQUEST | NLM_F_ROOT, &rt_hdr, sizeof(struct ifaddrmsg));
	if (err < 0) {
		goto out_free;
	}

	/* Retrieve answer. Message is handled by get_addresses_cb */
	nl_socket_modify_cb(socket, NL_CB_VALID, NL_CB_CUSTOM, get_addresses_cb, &info);
	nl_recvmsgs_default(socket);

out_free:
	nl_socket_free(socket);
	return info.addresses;
}

static void add_if_not_empty(struct json_object *obj, const char *key, struct json_object *val) {
	if (json_object_array_length(val))
		json_object_object_add(obj, key, val);
	else
		json_object_put(val);
}

static bool interface_file_exists(const char *ifname, const char *name) {
	const char *format = "/sys/class/net/%s/%s";
	char path[strlen(format) + strlen(ifname) + strlen(name)];
	snprintf(path, sizeof(path), format, ifname, name);

	return !access(path, F_OK);
}

static void mesh_add_subif(const char *ifname, struct json_object *wireless,
			   struct json_object *tunnel, struct json_object *other) {
	struct json_object *address = gluonutil_wrap_and_free_string(gluonutil_get_interface_address(ifname));

	char lowername[IFNAMSIZ];
	strncpy(lowername, ifname, sizeof(lowername)-1);
	lowername[sizeof(lowername)-1] = 0;

	const char *format = "/sys/class/net/%s/lower_*";
	char pattern[strlen(format) + IFNAMSIZ];

	/* In case of VLAN and bridge interfaces, we want the lower interface
	 * to determine the interface type (but not for the interface address) */
	while (true) {
		snprintf(pattern, sizeof(pattern), format, lowername);
		size_t pattern_len = strlen(pattern);

		glob_t lower;
		if (glob(pattern, GLOB_NOSORT, NULL, &lower))
			break;

		strncpy(lowername, lower.gl_pathv[0] + pattern_len - 1, sizeof(lowername)-1);

		globfree(&lower);
	}

	if (interface_file_exists(lowername, "wireless"))
		json_object_array_add(wireless, address);
	else if (interface_file_exists(lowername, "tun_flags"))
		json_object_array_add(tunnel, address);
	else
		json_object_array_add(other, address);

}

static struct json_object * get_mesh_subifs(const char *ifname) {
	struct json_object *wireless = json_object_new_array();
	struct json_object *tunnel = json_object_new_array();
	struct json_object *other = json_object_new_array();

	const char *format = "/sys/class/net/%s/lower_*";
	char pattern[strlen(format) + strlen(ifname) - 1];
	snprintf(pattern, sizeof(pattern), format, ifname);

	size_t pattern_len = strlen(pattern);

	glob_t lower;
	if (!glob(pattern, GLOB_NOSORT, NULL, &lower)) {
		size_t i;
		for (i = 0; i < lower.gl_pathc; i++) {
			mesh_add_subif(lower.gl_pathv[i] + pattern_len - 1,
				       wireless, tunnel, other);
		}

		globfree(&lower);
	}

	struct json_object *ret = json_object_new_object();
	add_if_not_empty(ret, "wireless", wireless);
	add_if_not_empty(ret, "tunnel", tunnel);
	add_if_not_empty(ret, "other", other);
	return ret;
}

static struct json_object * get_mesh(void) {
	struct json_object *ret = json_object_new_object();
	struct json_object *bat0_interfaces = json_object_new_object();
	json_object_object_add(bat0_interfaces, "interfaces", get_mesh_subifs("bat0"));
	json_object_object_add(ret, "bat0", bat0_interfaces);
	return ret;
}

struct json_object * respondd_provider_nodeinfo(void) {
	struct json_object *ret = json_object_new_object();

	struct json_object *network = json_object_new_object();
	json_object_object_add(network, "addresses", get_addresses());
	json_object_object_add(network, "mesh", get_mesh());
	json_object_object_add(ret, "network", network);

	struct json_object *software = json_object_new_object();
	struct json_object *software_batman_adv = json_object_new_object();
	json_object_object_add(software_batman_adv, "version",
		gluonutil_wrap_and_free_string(gluonutil_read_line("/sys/module/batman_adv/version")));
	json_object_object_add(software_batman_adv, "compat", json_object_new_int(15));
	json_object_object_add(software, "batman-adv", software_batman_adv);
	json_object_object_add(ret, "software", software);

	return ret;
}