#include "stdinc.h"
#include "modules.h"
#include "hook.h"
#include "client.h"
#include "ircd.h"
#include "send.h"
#include "s_conf.h"
#include "s_user.h"
#include "s_serv.h"
#include "numeric.h"

static const char ip_cloaking_desc[] = "Very old IP cloaking mechanism";

/* if you're modifying this module, you'll probably want to change this */
#define KEY 0x13748cfa

static int
_modinit(void)
{
	/* add the usermode to the available slot */
	user_modes['h'] = find_umode_slot();
	construct_umodebuf();

	return 0;
}

static void
_moddeinit(void)
{
	/* disable the umode and remove it from the available list */
	user_modes['h'] = 0;
	construct_umodebuf();
}

static void check_umode_change(void *data);
static void check_new_user(void *data);
mapi_hfn_list_av1 ip_cloaking_hfnlist[] = {
	{ "umode_changed", (hookfn) check_umode_change },
	{ "new_local_user", (hookfn) check_new_user },
	{ NULL, NULL }
};

DECLARE_MODULE_AV2(ip_cloaking, _modinit, _moddeinit, NULL, NULL,
			ip_cloaking_hfnlist, NULL, NULL, ip_cloaking_desc);

static void
distribute_hostchange(struct Client *client_p, char *newhost)
{
	if (newhost != client_p->orighost)
		sendto_one_numeric(client_p, RPL_HOSTHIDDEN, "%s :is now your hidden host",
			newhost);
	else
		sendto_one_numeric(client_p, RPL_HOSTHIDDEN, "%s :hostname reset",
			newhost);

	sendto_server(NULL, NULL,
		CAP_EUID | CAP_TS6, NOCAPS, ":%s CHGHOST %s :%s",
		use_id(&me), use_id(client_p), newhost);
	sendto_server(NULL, NULL,
		CAP_TS6, CAP_EUID, ":%s ENCAP * CHGHOST %s :%s",
		use_id(&me), use_id(client_p), newhost);

	change_nick_user_host(client_p, client_p->name, client_p->username, newhost, 0, "Changing host");

	if (newhost != client_p->orighost)
		SetDynSpoof(client_p);
	else
		ClearDynSpoof(client_p);
}

static void
do_host_cloak(const char *inbuf, char *outbuf, int ipmask)
{
	unsigned int cyc;
	unsigned int hosthash = 1, hosthash2 = 1;
	unsigned int maxcycle = strlen(inbuf);
	int len1;
	const char *rest, *next;

	for (cyc = 0; cyc < maxcycle - 2; cyc += 2)
		hosthash *= (unsigned int) inbuf[cyc];

	/* safety: decrement ourselves two steps back */
	for (cyc = maxcycle - 1; cyc >= 1; cyc -= 2)
		hosthash2 *= (unsigned int) inbuf[cyc];

	/* lets do some bitshifting -- this pretty much destroys the IP
	 * sequence, while still providing a checksum. exactly what
	 * we're shooting for. --nenolod
	 */
	hosthash += (hosthash2 / KEY);
	hosthash2 += (hosthash / KEY);

	if (ipmask == 0)
	{
		snprintf(outbuf, HOSTLEN, "%s-%X%X",
			ServerInfo.network_name, hosthash2, hosthash);
		len1 = strlen(outbuf);
		rest = strchr(inbuf, '.');
		if (rest == NULL)
			rest = ".";
		/* try to avoid truncation -- jilles */
		while (len1 + strlen(rest) >= HOSTLEN && (next = strchr(rest + 1, '.')) != NULL)
			rest = next;
		rb_strlcat(outbuf, rest, HOSTLEN);
	}
	else
		snprintf(outbuf, HOSTLEN, "%X%X.%s",
			hosthash2, hosthash, ServerInfo.network_name);
}

static void
check_umode_change(void *vdata)
{
	hook_data_umode_changed *data = (hook_data_umode_changed *)vdata;
	struct Client *source_p = data->client;

	if (!MyClient(source_p))
		return;

	/* didn't change +h umode, we don't need to do anything */
	if (!((data->oldumodes ^ source_p->umodes) & user_modes['h']))
		return;

	if (source_p->umodes & user_modes['h'])
	{
		if (IsIPSpoof(source_p) || source_p->localClient->mangledhost == NULL || (IsDynSpoof(source_p) && strcmp(source_p->host, source_p->localClient->mangledhost)))
		{
			source_p->umodes &= ~user_modes['h'];
			return;
		}
		if (strcmp(source_p->host, source_p->localClient->mangledhost))
		{
			distribute_hostchange(source_p, source_p->localClient->mangledhost);
		}
		else /* not really nice, but we need to send this numeric here */
			sendto_one_numeric(source_p, RPL_HOSTHIDDEN, "%s :is now your hidden host",
				source_p->host);
	}
	else if (!(source_p->umodes & user_modes['h']))
	{
		if (source_p->localClient->mangledhost != NULL &&
				!strcmp(source_p->host, source_p->localClient->mangledhost))
		{
			distribute_hostchange(source_p, source_p->orighost);
		}
	}
}

static void
check_new_user(void *vdata)
{
	struct Client *source_p = (void *)vdata;

	if (IsIPSpoof(source_p))
	{
		source_p->umodes &= ~user_modes['h'];
		return;
	}
	source_p->localClient->mangledhost = rb_malloc(HOSTLEN);
	if (!irccmp(source_p->orighost, source_p->sockhost))
		do_host_cloak(source_p->orighost, source_p->localClient->mangledhost, 1);
	else
		do_host_cloak(source_p->orighost, source_p->localClient->mangledhost, 0);
	if (IsDynSpoof(source_p))
		source_p->umodes &= ~user_modes['h'];
	if (source_p->umodes & user_modes['h'])
	{
		rb_strlcpy(source_p->host, source_p->localClient->mangledhost, sizeof(source_p->host));
		if (irccmp(source_p->host, source_p->orighost))
			SetDynSpoof(source_p);
	}
}