/*
 * Avahi mDNS backend, with libevent polling
 *
 * Copyright (C) 2009-2011 Julien BLACHE <jb@jblache.org>
 *
 * Pieces coming from mt-daapd:
 * Copyright (C) 2005 Sebastian Dröge <slomo@ubuntu.com>
 *
 * 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, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */

#ifdef HAVE_CONFIG_H
# include <config.h>
#endif

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <net/if.h>

#include <event2/event.h>

#include <avahi-common/watch.h>
#include <avahi-common/malloc.h>
#include <avahi-common/error.h>
#include <avahi-client/client.h>
#include <avahi-client/publish.h>
#include <avahi-client/lookup.h>

#include "logger.h"
#include "mdns.h"

#define MDNSERR avahi_strerror(avahi_client_errno(mdns_client))

/* Main event base, from main.c */
extern struct event_base *evbase_main;

static AvahiClient *mdns_client = NULL;
static AvahiEntryGroup *mdns_group = NULL;


struct AvahiWatch
{
  struct event *ev;

  AvahiWatchCallback cb;
  void *userdata;

  AvahiWatch *next;
};

struct AvahiTimeout
{
  struct event *ev;

  AvahiTimeoutCallback cb;
  void *userdata;

  AvahiTimeout *next;
};

static AvahiWatch *all_w;
static AvahiTimeout *all_t;

/* libevent callbacks */

static void
evcb_watch(int fd, short ev_events, void *arg)
{
  AvahiWatch *w;
  AvahiWatchEvent a_events;

  w = (AvahiWatch *)arg;

  a_events = 0;
  if (ev_events & EV_READ)
    a_events |= AVAHI_WATCH_IN;
  if (ev_events & EV_WRITE)
    a_events |= AVAHI_WATCH_OUT;

  event_add(w->ev, NULL);

  w->cb(w, fd, a_events, w->userdata);
}

static void
evcb_timeout(int fd, short ev_events, void *arg)
{
  AvahiTimeout *t;

  t = (AvahiTimeout *)arg;

  t->cb(t, t->userdata);
}

/* AvahiPoll implementation for libevent */

static int
_ev_watch_add(AvahiWatch *w, int fd, AvahiWatchEvent a_events)
{
  short ev_events;

  ev_events = 0;
  if (a_events & AVAHI_WATCH_IN)
    ev_events |= EV_READ;
  if (a_events & AVAHI_WATCH_OUT)
    ev_events |= EV_WRITE;

  if (w->ev)
    event_free(w->ev);

  w->ev = event_new(evbase_main, fd, ev_events, evcb_watch, w);
  if (!w->ev)
    {
      DPRINTF(E_LOG, L_MDNS, "Could not make new event in _ev_watch_add\n");
      return -1;
    }

  return event_add(w->ev, NULL);
}

static AvahiWatch *
ev_watch_new(const AvahiPoll *api, int fd, AvahiWatchEvent a_events, AvahiWatchCallback cb, void *userdata)
{
  AvahiWatch *w;
  int ret;

  w = calloc(1, sizeof(AvahiWatch));
  if (!w)
    return NULL;

  w->cb = cb;
  w->userdata = userdata;

  ret = _ev_watch_add(w, fd, a_events);
  if (ret != 0)
    {
      free(w);
      return NULL;
    }

  w->next = all_w;
  all_w = w;

  return w;
}

static void
ev_watch_update(AvahiWatch *w, AvahiWatchEvent a_events)
{
  if (w->ev)
    event_del(w->ev);

  _ev_watch_add(w, (int)event_get_fd(w->ev), a_events);
}

static AvahiWatchEvent
ev_watch_get_events(AvahiWatch *w)
{
  AvahiWatchEvent a_events;

  a_events = 0;

  if (event_pending(w->ev, EV_READ, NULL))
    a_events |= AVAHI_WATCH_IN;
  if (event_pending(w->ev, EV_WRITE, NULL))
    a_events |= AVAHI_WATCH_OUT;

  return a_events;
}

static void
ev_watch_free(AvahiWatch *w)
{
  AvahiWatch *prev;
  AvahiWatch *cur;

  if (w->ev)
    {
      event_free(w->ev);
      w->ev = NULL;
    }

  prev = NULL;
  for (cur = all_w; cur; prev = cur, cur = cur->next)
    {
      if (cur != w)
	continue;

      if (prev == NULL)
	all_w = w->next;
      else
	prev->next = w->next;

      break;
    }

  free(w);
}


static int
_ev_timeout_add(AvahiTimeout *t, const struct timeval *tv)
{
  struct timeval e_tv;
  struct timeval now;
  int ret;

  if (t->ev)
    event_free(t->ev);

  t->ev = evtimer_new(evbase_main, evcb_timeout, t);
  if (!t->ev)
    {
      DPRINTF(E_LOG, L_MDNS, "Could not make event in _ev_timeout_add - out of memory?\n");
      return -1;
    }

  if ((tv->tv_sec == 0) && (tv->tv_usec == 0))
    {
      evutil_timerclear(&e_tv);
    }
  else
    {
      ret = gettimeofday(&now, NULL);
      if (ret != 0)
	return -1;

      evutil_timersub(tv, &now, &e_tv);
    }

  return evtimer_add(t->ev, &e_tv);
}

static AvahiTimeout *
ev_timeout_new(const AvahiPoll *api, const struct timeval *tv, AvahiTimeoutCallback cb, void *userdata)
{
  AvahiTimeout *t;
  int ret;

  t = calloc(1, sizeof(AvahiTimeout));
  if (!t)
    return NULL;

  t->cb = cb;
  t->userdata = userdata;

  if (tv != NULL)
    {
      ret = _ev_timeout_add(t, tv);
      if (ret != 0)
	{
	  free(t);

	  return NULL;
	}
    }

  t->next = all_t;
  all_t = t;

  return t;
}

static void
ev_timeout_update(AvahiTimeout *t, const struct timeval *tv)
{
  if (t->ev)
    event_del(t->ev);

  if (tv)
    _ev_timeout_add(t, tv);
}

static void
ev_timeout_free(AvahiTimeout *t)
{
  AvahiTimeout *prev;
  AvahiTimeout *cur;

  if (t->ev)
    {
      event_free(t->ev);
      t->ev = NULL;
    }

  prev = NULL;
  for (cur = all_t; cur; prev = cur, cur = cur->next)
    {
      if (cur != t)
	continue;

      if (prev == NULL)
	all_t = t->next;
      else
	prev->next = t->next;

      break;
    }

  free(t);
}

static struct AvahiPoll ev_poll_api =
  {
    .userdata = NULL,
    .watch_new = ev_watch_new,
    .watch_update = ev_watch_update,
    .watch_get_events = ev_watch_get_events,
    .watch_free = ev_watch_free,
    .timeout_new = ev_timeout_new,
    .timeout_update = ev_timeout_update,
    .timeout_free = ev_timeout_free
  };


/* Avahi client callbacks & helpers */

struct mdns_browser
{
  char *type;
  AvahiProtocol protocol;
  mdns_browse_cb cb;

  struct mdns_browser *next;
};

struct mdns_group_entry
{
  char *name;
  char *type;
  int port;
  AvahiStringList *txt;

  struct mdns_group_entry *next;
};

static struct mdns_browser *browser_list;
static struct mdns_group_entry *group_entries;

// Note: This will only return the first DNS record. Should be enough, but
// should more be needed, then a record browser needs to be added.
static void
browse_resolve_callback(AvahiServiceResolver *r, AvahiIfIndex intf, AvahiProtocol proto, AvahiResolverEvent event,
			const char *name, const char *type, const char *domain, const char *hostname, const AvahiAddress *addr,
			uint16_t port, AvahiStringList *txt, AvahiLookupResultFlags flags, void *userdata)
{
  struct mdns_browser *mb;
  struct keyval txt_kv;
  char address[AVAHI_ADDRESS_STR_MAX];
  char *key;
  char *value;
  int family;
  int ret;

  if (event == AVAHI_RESOLVER_FAILURE)
    {
      DPRINTF(E_LOG, L_MDNS, "Avahi Resolver failure: service '%s' type '%s': %s\n", name, type, MDNSERR);
      goto out_free_resolver;
    }
  else if (event != AVAHI_RESOLVER_FOUND)
    {
      DPRINTF(E_LOG, L_MDNS, "Avahi Resolver empty callback\n");
      goto out_free_resolver;
    }

  DPRINTF(E_DBG, L_MDNS, "Avahi Resolver: resolved service '%s' type '%s' proto %d\n", name, type, proto);

  memset(&txt_kv, 0, sizeof(struct keyval));

  while (txt)
    {
      ret = avahi_string_list_get_pair(txt, &key, &value, NULL);
      txt = avahi_string_list_get_next(txt);

      if (ret < 0)
	continue;

      if (value)
	{
	  keyval_add(&txt_kv, key, value);
	  avahi_free(value);
	}

      avahi_free(key);
    }

  avahi_address_snprint(address, sizeof(address), addr);

  // For some reason, the proto returned by the callback will not always be the
  // protocol of the address - so we use addr->proto instead
  family = avahi_proto_to_af(addr->proto);

  mb = (struct mdns_browser *)userdata;

  if (family != AF_UNSPEC)
    mb->cb(name, type, domain, hostname, family, address, port, &txt_kv);

  keyval_clear(&txt_kv);

 out_free_resolver:
  avahi_service_resolver_free(r);
}

static void
browse_callback(AvahiServiceBrowser *b, AvahiIfIndex intf, AvahiProtocol proto, AvahiBrowserEvent event,
		const char *name, const char *type, const char *domain, AvahiLookupResultFlags flags, void *userdata)
{
  struct mdns_browser *mb;
  AvahiServiceResolver *res;
  int family;

  mb = (struct mdns_browser *)userdata;

  switch (event)
    {
      case AVAHI_BROWSER_FAILURE:
	DPRINTF(E_LOG, L_MDNS, "Avahi Browser failure: %s\n", MDNSERR);

	avahi_service_browser_free(b);

	b = avahi_service_browser_new(mdns_client, AVAHI_IF_UNSPEC, mb->protocol, mb->type, NULL, 0, browse_callback, mb);
	if (!b)
	  DPRINTF(E_LOG, L_MDNS, "Failed to recreate service browser (service type %s): %s\n", mb->type, MDNSERR);

	return;

      case AVAHI_BROWSER_NEW:
	DPRINTF(E_DBG, L_MDNS, "Avahi Browser: NEW service '%s' type '%s' proto %d\n", name, type, proto);

	res = avahi_service_resolver_new(mdns_client, intf, proto, name, type, domain, proto, 0, browse_resolve_callback, mb);
	if (!res)
	  DPRINTF(E_LOG, L_MDNS, "Failed to create service resolver: %s\n", MDNSERR);

	break;

      case AVAHI_BROWSER_REMOVE:
	DPRINTF(E_DBG, L_MDNS, "Avahi Browser: REMOVE service '%s' type '%s' proto %d\n", name, type, proto);

	family = avahi_proto_to_af(proto);
	if (family != AF_UNSPEC)
	  mb->cb(name, type, domain, NULL, family, NULL, -1, NULL);
	break;

      case AVAHI_BROWSER_ALL_FOR_NOW:
      case AVAHI_BROWSER_CACHE_EXHAUSTED:
	DPRINTF(E_DBG, L_MDNS, "Avahi Browser (%s): no more results (%s)\n", mb->type,
		(event == AVAHI_BROWSER_CACHE_EXHAUSTED) ? "CACHE_EXHAUSTED" : "ALL_FOR_NOW");
	break;
    }
}


static void
entry_group_callback(AvahiEntryGroup *g, AvahiEntryGroupState state, AVAHI_GCC_UNUSED void *userdata)
{
  if (!g || (g != mdns_group))
    return;

  switch (state)
    {
      case AVAHI_ENTRY_GROUP_ESTABLISHED:
        DPRINTF(E_DBG, L_MDNS, "Successfully added mDNS services\n");
        break;

      case AVAHI_ENTRY_GROUP_COLLISION:
        DPRINTF(E_DBG, L_MDNS, "Group collision\n");
        break;

      case AVAHI_ENTRY_GROUP_FAILURE:
        DPRINTF(E_DBG, L_MDNS, "Group failure\n");
        break;

      case AVAHI_ENTRY_GROUP_UNCOMMITED:
        DPRINTF(E_DBG, L_MDNS, "Group uncommitted\n");
	break;

      case AVAHI_ENTRY_GROUP_REGISTERING:
        DPRINTF(E_DBG, L_MDNS, "Group registering\n");
        break;
    }
}

static void
_create_services(void)
{
  struct mdns_group_entry *pentry;
  int ret;

  DPRINTF(E_DBG, L_MDNS, "Creating service group\n");

  if (!group_entries)
    {
      DPRINTF(E_DBG, L_MDNS, "No entries yet... skipping service create\n");
      return;
    }

    if (mdns_group == NULL)
      {
        mdns_group = avahi_entry_group_new(mdns_client, entry_group_callback, NULL);
	if (!mdns_group)
	  {
            DPRINTF(E_WARN, L_MDNS, "Could not create Avahi EntryGroup: %s\n", MDNSERR);
            return;
	  }
      }

    pentry = group_entries;
    while (pentry)
      {
        DPRINTF(E_DBG, L_MDNS, "Re-registering %s/%s\n", pentry->name, pentry->type);

        ret = avahi_entry_group_add_service_strlst(mdns_group, AVAHI_IF_UNSPEC, AVAHI_PROTO_UNSPEC, 0,
						   pentry->name, pentry->type,
						   NULL, NULL, pentry->port, pentry->txt);
	if (ret < 0)
	  {
	    DPRINTF(E_WARN, L_MDNS, "Could not add mDNS services: %s\n", avahi_strerror(ret));
	    return;
	  }

	pentry = pentry->next;
      }

    ret = avahi_entry_group_commit(mdns_group);
    if (ret < 0)
      DPRINTF(E_WARN, L_MDNS, "Could not commit mDNS services: %s\n", MDNSERR);
}

static void
client_callback(AvahiClient *c, AvahiClientState state, AVAHI_GCC_UNUSED void * userdata)
{
  struct mdns_browser *mb;
  AvahiServiceBrowser *b;
  int error;

  switch (state)
    {
      case AVAHI_CLIENT_S_RUNNING:
        DPRINTF(E_LOG, L_MDNS, "Avahi state change: Client running\n");
        if (!mdns_group)
	  _create_services();

	for (mb = browser_list; mb; mb = mb->next)
	  {
	    b = avahi_service_browser_new(mdns_client, AVAHI_IF_UNSPEC, mb->protocol, mb->type, NULL, 0, browse_callback, mb);
	    if (!b)
	      DPRINTF(E_LOG, L_MDNS, "Failed to recreate service browser (service type %s): %s\n", mb->type, MDNSERR);
	  }
        break;

      case AVAHI_CLIENT_S_COLLISION:
        DPRINTF(E_LOG, L_MDNS, "Avahi state change: Client collision\n");
        if(mdns_group)
	  avahi_entry_group_reset(mdns_group);
        break;

      case AVAHI_CLIENT_FAILURE:
        DPRINTF(E_LOG, L_MDNS, "Avahi state change: Client failure\n");

	error = avahi_client_errno(c);
	if (error == AVAHI_ERR_DISCONNECTED)
	  {
	    DPRINTF(E_LOG, L_MDNS, "Avahi Server disconnected, reconnecting\n");

	    avahi_client_free(mdns_client);
	    mdns_group = NULL;

	    mdns_client = avahi_client_new(&ev_poll_api, AVAHI_CLIENT_NO_FAIL, client_callback, NULL, &error);
	    if (!mdns_client)
	      DPRINTF(E_LOG, L_MDNS, "Failed to create new Avahi client: %s\n", avahi_strerror(error));
	  }
	else
	  {
	    DPRINTF(E_LOG, L_MDNS, "Avahi client failure: %s\n", avahi_strerror(error));
	  }
        break;

      case AVAHI_CLIENT_S_REGISTERING:
        DPRINTF(E_LOG, L_MDNS, "Avahi state change: Client registering\n");
        if (mdns_group)
	  avahi_entry_group_reset(mdns_group);
        break;

      case AVAHI_CLIENT_CONNECTING:
        DPRINTF(E_LOG, L_MDNS, "Avahi state change: Client connecting\n");
        break;
    }
}


/* mDNS interface - to be called only from the main thread */

int
mdns_init(void)
{
  int error;

  DPRINTF(E_DBG, L_MDNS, "Initializing Avahi mDNS\n");

  all_w = NULL;
  all_t = NULL;
  group_entries = NULL;
  browser_list = NULL;

  mdns_client = avahi_client_new(&ev_poll_api, AVAHI_CLIENT_NO_FAIL,
				 client_callback, NULL, &error);
  if (!mdns_client)
    {
      DPRINTF(E_WARN, L_MDNS, "mdns_init: Could not create Avahi client: %s\n", MDNSERR);

      return -1;
    }

  return 0;
}

void
mdns_deinit(void)
{
  struct mdns_group_entry *ge;
  struct mdns_browser *mb;
  AvahiWatch *w;
  AvahiTimeout *t;

  for (t = all_t; t; t = t->next)
    if (t->ev)
      {
	event_free(t->ev);
	t->ev = NULL;
      }

  for (w = all_w; w; w = w->next)
    if (w->ev)
      {
	event_free(w->ev);
	w->ev = NULL;
      }

  for (ge = group_entries; group_entries; ge = group_entries)
    {
      group_entries = ge->next;

      free(ge->name);
      free(ge->type);
      avahi_string_list_free(ge->txt);

      free(ge);
    }

  for (mb = browser_list; browser_list; mb = browser_list)
    {
      browser_list = mb->next;

      free(mb->type);
      free(mb);
    }

  if (mdns_client)
    avahi_client_free(mdns_client);
}

int
mdns_register(char *name, char *type, int port, char **txt)
{
  struct mdns_group_entry *ge;
  AvahiStringList *txt_sl;
  int i;

  DPRINTF(E_DBG, L_MDNS, "Adding mDNS service %s/%s\n", name, type);

  ge = calloc(1, sizeof(struct mdns_group_entry));
  if (!ge)
    {
      DPRINTF(E_LOG, L_MDNS, "Out of memory for mdns register\n");
      return -1;
    }

  ge->name = strdup(name);
  ge->type = strdup(type);
  ge->port = port;

  txt_sl = NULL;
  if (txt)
    {
      for (i = 0; txt[i]; i++)
	{
	  txt_sl = avahi_string_list_add(txt_sl, txt[i]);

	  DPRINTF(E_DBG, L_MDNS, "Added key %s\n", txt[i]);
	}
    }

  ge->txt = txt_sl;

  ge->next = group_entries;
  group_entries = ge;

  if (mdns_group)
    {
      DPRINTF(E_DBG, L_MDNS, "Resetting mDNS group\n");
      avahi_entry_group_reset(mdns_group);
    }

  DPRINTF(E_DBG, L_MDNS, "Creating service group\n");
  _create_services();

  return 0;
}

int
mdns_browse(char *type, int family, mdns_browse_cb cb)
{
  struct mdns_browser *mb;
  AvahiServiceBrowser *b;

  DPRINTF(E_DBG, L_MDNS, "Adding service browser for type %s\n", type);

  mb = calloc(1, sizeof(struct mdns_browser));
  if (!mb)
    {
      DPRINTF(E_LOG, L_MDNS, "Out of memory for new mdns browser\n");
      return -1;
    }

  mb->protocol = avahi_af_to_proto(family);
  mb->type = strdup(type);
  mb->cb = cb;

  mb->next = browser_list;
  browser_list = mb;

  b = avahi_service_browser_new(mdns_client, AVAHI_IF_UNSPEC, mb->protocol, mb->type, NULL, 0, browse_callback, mb);
  if (!b)
    {
      DPRINTF(E_LOG, L_MDNS, "Failed to create service browser: %s\n", MDNSERR);

      browser_list = mb->next;
      free(mb->type);
      free(mb);

      return -1;
    }

  return 0;
}