devicestate.c

Go to the documentation of this file.

/*
 * Asterisk -- An open source telephony toolkit.
 *
 * Copyright (C) 1999 - 2008, Digium, Inc.
 *
 * Mark Spencer <[email protected]>
 * Russell Bryant <[email protected]>
 *
 * See http://www.asterisk.org for more information about
 * the Asterisk project. Please do not directly contact
 * any of the maintainers of this project for assistance;
 * the project provides a web site, mailing lists and IRC
 * channels for your use.
 *
 * This program is free software, distributed under the terms of
 * the GNU General Public License Version 2. See the LICENSE file
 * at the top of the source tree.
 */

/*! \file
 *
 * \brief Device state management
 *
 * \author Mark Spencer <[email protected]>
 * \author Russell Bryant <[email protected]>
 *
 * \arg \ref AstExtState
 */

/*! \page AstExtState Extension and device states in Asterisk
 *
 * (Note that these descriptions of device states and extension
 * states have not been updated to the way things work
 * in Asterisk 1.6.)
 *
 * Asterisk has an internal system that reports states
 * for an extension. By using the dialplan priority -1,
 * also called a \b hint, a connection can be made from an
 * extension to one or many devices. The state of the extension
 * now depends on the combined state of the devices.
 *
 * The device state is basically based on the current calls.
 * If the devicestate engine can find a call from or to the
 * device, it's in use.
 *
 * Some channel drivers implement a callback function for
 * a better level of reporting device states. The SIP channel
 * has a complicated system for this, which is improved
 * by adding call limits to the configuration.
 *
 * Functions that want to check the status of an extension
 * register themself as a \b watcher.
 * Watchers in this system can subscribe either to all extensions
 * or just a specific extensions.
 *
 * For non-device related states, there's an API called
 * devicestate providers. This is an extendible system for
 * delivering state information from outside sources or
 * functions within Asterisk. Currently we have providers
 * for app_meetme.c - the conference bridge - and call
 * parking (metermaids).
 *
 * There are manly three subscribers to extension states
 * within Asterisk:
 * - AMI, the manager interface
 * - app_queue.c - the Queue dialplan application
 * - SIP subscriptions, a.k.a. "blinking lamps" or
 *   "buddy lists"
 *
 * The CLI command "show hints" show last known state
 *
 * \note None of these handle user states, like an IM presence
 * system. res_xmpp.c can subscribe and watch such states
 * in jabber/xmpp based systems.
 *
 * \section AstDevStateArch Architecture for devicestates
 *
 * When a channel driver or asterisk app changes state for
 * a watched object, it alerts the core. The core queues
 * a change. When the change is processed, there's a query
 * sent to the channel driver/provider if there's a function
 * to handle that, otherwise a channel walk is issued to find
 * a channel that involves the object.
 *
 * The changes are queued and processed by a separate thread.
 * This thread calls the watchers subscribing to status
 * changes for the object. For manager, this results
 * in events. For SIP, NOTIFY requests.
 *
 * - Device states
 *    \arg \ref devicestate.c
 *    \arg \ref devicestate.h
 *
 * \section AstExtStateArch Architecture for extension states
 *
 * Hints are connected to extension. If an extension changes state
 * it checks the hint devices. If there is a hint, the callbacks into
 * device states are checked. The aggregated state is set for the hint
 * and reported back.
 *
 * - Extension states
 *    \arg \ref AstENUM ast_extension_states
 *    \arg \ref pbx.c
 *    \arg \ref pbx.h
 * - Structures
 *    - \ref ast_state_cb struct.  Callbacks for watchers
 *    - Callback ast_state_cb_type
 *    - \ref ast_hint struct.
 * - Functions
 *    - ast_extension_state_add()
 *    - ast_extension_state_del()
 *    - ast_get_hint()
 *
 */

/*** MODULEINFO
   <support_level>core</support_level>
 ***/

/*** DOCUMENTATION
   <managerEvent language="en_US" name="DeviceStateChange">
      <managerEventInstance class="EVENT_FLAG_CALL">
         <synopsis>Raised when a device state changes</synopsis>
         <syntax>
            <parameter name="Device">
               <para>The device whose state has changed</para>
            </parameter>
            <parameter name="State">
               <para>The new state of the device</para>
            </parameter>
         </syntax>
         <description>
            <para>This differs from the <literal>ExtensionStatus</literal>
            event because this event is raised for all device state changes,
            not only for changes that affect dialplan hints.</para>
         </description>
         <see-also>
            <ref type="managerEvent">ExtensionStatus</ref>
         </see-also>
      </managerEventInstance>
   </managerEvent>
***/

#include "asterisk.h"

#include "asterisk/_private.h"
#include "asterisk/channel.h"
#include "asterisk/utils.h"
#include "asterisk/lock.h"
#include "asterisk/linkedlists.h"
#include "asterisk/devicestate.h"
#include "asterisk/pbx.h"
#include "asterisk/app.h"
#include "asterisk/astobj2.h"
#include "asterisk/stasis.h"
#include "asterisk/devicestate.h"

#define DEVSTATE_TOPIC_BUCKETS 57

/*! \brief Device state strings for printing */
static const char * const devstatestring[][2] = {
   { /* 0 AST_DEVICE_UNKNOWN */     "Unknown",     "UNKNOWN"     }, /*!< Valid, but unknown state */
   { /* 1 AST_DEVICE_NOT_INUSE */   "Not in use",  "NOT_INUSE"   }, /*!< Not used */
   { /* 2 AST_DEVICE IN USE */      "In use",      "INUSE"       }, /*!< In use */
   { /* 3 AST_DEVICE_BUSY */        "Busy",        "BUSY"        }, /*!< Busy */
   { /* 4 AST_DEVICE_INVALID */     "Invalid",     "INVALID"     }, /*!< Invalid - not known to Asterisk */
   { /* 5 AST_DEVICE_UNAVAILABLE */ "Unavailable", "UNAVAILABLE" }, /*!< Unavailable (not registered) */
   { /* 6 AST_DEVICE_RINGING */     "Ringing",     "RINGING"     }, /*!< Ring, ring, ring */
   { /* 7 AST_DEVICE_RINGINUSE */   "Ring+Inuse",  "RINGINUSE"   }, /*!< Ring and in use */
   { /* 8 AST_DEVICE_ONHOLD */      "On Hold",     "ONHOLD"      }, /*!< On Hold */
};

/*!\brief Mapping for channel states to device states */
static const struct chan2dev {
   enum ast_channel_state chan;
   enum ast_device_state dev;
} chan2dev[] = {
   { AST_STATE_DOWN,            AST_DEVICE_NOT_INUSE },
   { AST_STATE_RESERVED,        AST_DEVICE_INUSE },
   { AST_STATE_OFFHOOK,         AST_DEVICE_INUSE },
   { AST_STATE_DIALING,         AST_DEVICE_INUSE },
   { AST_STATE_RING,            AST_DEVICE_INUSE },
   { AST_STATE_RINGING,         AST_DEVICE_RINGING },
   { AST_STATE_UP,              AST_DEVICE_INUSE },
   { AST_STATE_BUSY,            AST_DEVICE_BUSY },
   { AST_STATE_DIALING_OFFHOOK, AST_DEVICE_INUSE },
   { AST_STATE_PRERING,         AST_DEVICE_RINGING },
};

/*! \brief  A device state provider (not a channel) */
struct devstate_prov {
   char label[40];
   ast_devstate_prov_cb_type callback;
   AST_RWLIST_ENTRY(devstate_prov) list;
};

/*! \brief A list of providers */
static AST_RWLIST_HEAD_STATIC(devstate_provs, devstate_prov);

struct state_change {
   AST_LIST_ENTRY(state_change) list;
   enum ast_devstate_cache cachable;
   char device[1];
};

/*! \brief The state change queue. State changes are queued
   for processing by a separate thread */
static AST_LIST_HEAD_STATIC(state_changes, state_change);

/*! \brief The device state change notification thread */
static pthread_t change_thread = AST_PTHREADT_NULL;

/*! \brief Flag for the queue */
static ast_cond_t change_pending;
static volatile int shuttingdown;

struct stasis_subscription *devstate_message_sub;

static struct stasis_topic *device_state_topic_all;
static struct stasis_cache *device_state_cache;
static struct stasis_caching_topic *device_state_topic_cached;
static struct stasis_topic_pool *device_state_topic_pool;

static struct ast_manager_event_blob *devstate_to_ami(struct stasis_message *msg);
static struct ast_event *devstate_to_event(struct stasis_message *msg);


STASIS_MESSAGE_TYPE_DEFN(ast_device_state_message_type,
   .to_ami = devstate_to_ami,
   .to_event = devstate_to_event,
);

/* Forward declarations */
static int getproviderstate(const char *provider, const char *address);

/*! \brief Find devicestate as text message for output */
const char *ast_devstate2str(enum ast_device_state devstate)
{
   return devstatestring[devstate][0];
}

enum ast_device_state ast_state_chan2dev(enum ast_channel_state chanstate)
{
   int i;
   chanstate &= 0xFFFF;
   for (i = 0; i < ARRAY_LEN(chan2dev); i++) {
      if (chan2dev[i].chan == chanstate) {
         return chan2dev[i].dev;
      }
   }
   return AST_DEVICE_UNKNOWN;
}

/* Parseable */
const char *ast_devstate_str(enum ast_device_state state)
{
   return devstatestring[state][1];
}

enum ast_device_state ast_devstate_val(const char *val)
{
   if (!strcasecmp(val, "NOT_INUSE"))
      return AST_DEVICE_NOT_INUSE;
   else if (!strcasecmp(val, "INUSE"))
      return AST_DEVICE_INUSE;
   else if (!strcasecmp(val, "BUSY"))
      return AST_DEVICE_BUSY;
   else if (!strcasecmp(val, "INVALID"))
      return AST_DEVICE_INVALID;
   else if (!strcasecmp(val, "UNAVAILABLE"))
      return AST_DEVICE_UNAVAILABLE;
   else if (!strcasecmp(val, "RINGING"))
      return AST_DEVICE_RINGING;
   else if (!strcasecmp(val, "RINGINUSE"))
      return AST_DEVICE_RINGINUSE;
   else if (!strcasecmp(val, "ONHOLD"))
      return AST_DEVICE_ONHOLD;

   return AST_DEVICE_UNKNOWN;
}

/*! \brief Find out if device is active in a call or not
   \note find channels with the device's name in it
   This function is only used for channels that does not implement
   devicestate natively
*/
enum ast_device_state ast_parse_device_state(const char *device)
{
   struct ast_channel *chan;
   char match[AST_CHANNEL_NAME];
   enum ast_device_state res;

   snprintf(match, sizeof(match), "%s-", device);

   if (!(chan = ast_channel_get_by_name_prefix(match, strlen(match)))) {
      return AST_DEVICE_UNKNOWN;
   }

   if (ast_channel_hold_state(chan) == AST_CONTROL_HOLD) {
      res = AST_DEVICE_ONHOLD;
   } else {
      res = ast_state_chan2dev(ast_channel_state(chan));
   }
   ast_channel_unref(chan);

   return res;
}

static enum ast_device_state devstate_cached(const char *device)
{
   struct stasis_message *cached_msg;
   struct ast_device_state_message *device_state;
   enum ast_device_state state;

   cached_msg = stasis_cache_get_by_eid(ast_device_state_cache(),
      ast_device_state_message_type(), device, NULL);
   if (!cached_msg) {
      return AST_DEVICE_UNKNOWN;
   }
   device_state = stasis_message_data(cached_msg);
   state = device_state->state;
   ao2_cleanup(cached_msg);

   return state;
}

/*! \brief Check device state through channel specific function or generic function */
static enum ast_device_state _ast_device_state(const char *device, int check_cache)
{
   char *number;
   const struct ast_channel_tech *chan_tech;
   enum ast_device_state res;
   /*! \brief Channel driver that provides device state */
   char *tech;

   /* If the last known state is cached, just return that */
   if (check_cache) {
      res = devstate_cached(device);
      if (res != AST_DEVICE_UNKNOWN) {
         return res;
      }
   }

   number = ast_strdupa(device);
   tech = strsep(&number, "/");
   if (!number) {
      /*! \brief Another provider of device state */
      char *provider;

      provider = strsep(&tech, ":");
      if (!tech) {
         return AST_DEVICE_INVALID;
      }
      /* We have a provider */
      number = tech;

      ast_debug(3, "Checking if I can find provider for \"%s\" - number: %s\n", provider, number);
      return getproviderstate(provider, number);
   }

   ast_debug(4, "No provider found, checking channel drivers for %s - %s\n", tech, number);

   chan_tech = ast_get_channel_tech(tech);
   if (!chan_tech) {
      return AST_DEVICE_INVALID;
   }

   /* Does the channel driver support device state notification? */
   if (!chan_tech->devicestate) {
      /* No, try the generic function */
      return ast_parse_device_state(device);
   }

   res = chan_tech->devicestate(number);
   if (res == AST_DEVICE_UNKNOWN) {
      res = ast_parse_device_state(device);
   }

   return res;
}

enum ast_device_state ast_device_state(const char *device)
{
   /* This function is called from elsewhere in the code to find out the
    * current state of a device.  Check the cache, first. */

   return _ast_device_state(device, 1);
}

/*! \brief Add device state provider */
int ast_devstate_prov_add(const char *label, ast_devstate_prov_cb_type callback)
{
   struct devstate_prov *devcb;
   struct devstate_prov *devprov;

   if (!callback || !(devprov = ast_calloc(1, sizeof(*devprov))))
      return -1;

   devprov->callback = callback;
   ast_copy_string(devprov->label, label, sizeof(devprov->label));

   AST_RWLIST_WRLOCK(&devstate_provs);
   AST_RWLIST_TRAVERSE(&devstate_provs, devcb, list) {
      if (!strcasecmp(devcb->label, label)) {
         ast_log(LOG_WARNING, "Device state provider '%s' already registered\n", label);
         ast_free(devprov);
         AST_RWLIST_UNLOCK(&devstate_provs);
         return -1;
      }
   }
   AST_RWLIST_INSERT_HEAD(&devstate_provs, devprov, list);
   AST_RWLIST_UNLOCK(&devstate_provs);

   return 0;
}

/*! \brief Remove device state provider */
int ast_devstate_prov_del(const char *label)
{
   struct devstate_prov *devcb;
   int res = -1;

   AST_RWLIST_WRLOCK(&devstate_provs);
   AST_RWLIST_TRAVERSE_SAFE_BEGIN(&devstate_provs, devcb, list) {
      if (!strcasecmp(devcb->label, label)) {
         AST_RWLIST_REMOVE_CURRENT(list);
         ast_free(devcb);
         res = 0;
         break;
      }
   }
   AST_RWLIST_TRAVERSE_SAFE_END;
   AST_RWLIST_UNLOCK(&devstate_provs);

   return res;
}

/*! \brief Get provider device state */
static int getproviderstate(const char *provider, const char *address)
{
   struct devstate_prov *devprov;
   int res = AST_DEVICE_INVALID;

   AST_RWLIST_RDLOCK(&devstate_provs);
   AST_RWLIST_TRAVERSE(&devstate_provs, devprov, list) {
      ast_debug(5, "Checking provider %s with %s\n", devprov->label, provider);

      if (!strcasecmp(devprov->label, provider)) {
         res = devprov->callback(address);
         break;
      }
   }
   AST_RWLIST_UNLOCK(&devstate_provs);

   return res;
}

/*! Called by the state change thread to find out what the state is, and then
 *  to queue up the state change event */
static void do_state_change(const char *device, enum ast_devstate_cache cachable)
{
   enum ast_device_state state;

   state = _ast_device_state(device, 0);

   ast_debug(3, "Changing state for %s - state %u (%s)\n", device, state, ast_devstate2str(state));

   ast_publish_device_state(device, state, cachable);
}

int ast_devstate_changed_literal(enum ast_device_state state, enum ast_devstate_cache cachable, const char *device)
{
   struct state_change *change;

   /*
    * If we know the state change (how nice of the caller of this function!)
    * then we can just generate a device state event.
    *
    * Otherwise, we do the following:
    *   - Queue an event up to another thread that the state has changed
    *   - In the processing thread, it calls the callback provided by the
    *     device state provider (which may or may not be a channel driver)
    *     to determine the state.
    *   - If the device state provider does not know the state, or this is
    *     for a channel and the channel driver does not implement a device
    *     state callback, then we will look through the channel list to
    *     see if we can determine a state based on active calls.
    *   - Once a state has been determined, a device state event is generated.
    */

   if (state != AST_DEVICE_UNKNOWN) {
      ast_publish_device_state(device, state, cachable);
   } else if (change_thread == AST_PTHREADT_NULL || !(change = ast_calloc(1, sizeof(*change) + strlen(device)))) {
      /* we could not allocate a change struct, or */
      /* there is no background thread, so process the change now */
      do_state_change(device, cachable);
   } else {
      /* queue the change */
      strcpy(change->device, device);
      change->cachable = cachable;
      AST_LIST_LOCK(&state_changes);
      AST_LIST_INSERT_TAIL(&state_changes, change, list);
      ast_cond_signal(&change_pending);
      AST_LIST_UNLOCK(&state_changes);
   }

   return 0;
}

int ast_devstate_changed(enum ast_device_state state, enum ast_devstate_cache cachable, const char *fmt, ...)
{
   char buf[AST_MAX_EXTENSION];
   va_list ap;

   va_start(ap, fmt);
   vsnprintf(buf, sizeof(buf), fmt, ap);
   va_end(ap);

   return ast_devstate_changed_literal(state, cachable, buf);
}

/*! \brief Go through the dev state change queue and update changes in the dev state thread */
static void *do_devstate_changes(void *data)
{
   struct state_change *next, *current;

   while (!shuttingdown) {
      /* This basically pops off any state change entries, resets the list back to NULL, unlocks, and processes each state change */
      AST_LIST_LOCK(&state_changes);
      if (AST_LIST_EMPTY(&state_changes))
         ast_cond_wait(&change_pending, &state_changes.lock);
      next = AST_LIST_FIRST(&state_changes);
      AST_LIST_HEAD_INIT_NOLOCK(&state_changes);
      AST_LIST_UNLOCK(&state_changes);

      /* Process each state change */
      while ((current = next)) {
         next = AST_LIST_NEXT(current, list);
         do_state_change(current->device, current->cachable);
         ast_free(current);
      }
   }

   return NULL;
}

static struct ast_device_state_message *device_state_alloc(const char *device, enum ast_device_state state, enum ast_devstate_cache cachable, const struct ast_eid *eid)
{
   struct ast_device_state_message *new_device_state;
   char *pos;
   size_t stuff_len;

   ast_assert(!ast_strlen_zero(device));

   stuff_len = strlen(device) + 1;
   if (eid) {
      stuff_len += sizeof(*eid);
   }
   new_device_state = ao2_alloc_options(sizeof(*new_device_state) + stuff_len, NULL,
      AO2_ALLOC_OPT_LOCK_NOLOCK);
   if (!new_device_state) {
      return NULL;
   }

   if (eid) {
      /* non-aggregate device state. */
      new_device_state->stuff[0] = *eid;
      new_device_state->eid = &new_device_state->stuff[0];
      pos = (char *) &new_device_state->stuff[1];
   } else {
      pos = (char *) &new_device_state->stuff[0];
   }

   strcpy(pos, device);/* Safe */
   new_device_state->device = pos;

   new_device_state->state = state;
   new_device_state->cachable = cachable;

   return new_device_state;
}

static void devstate_change_cb(void *data, struct stasis_subscription *sub, struct stasis_message *msg)
{
   struct ast_device_state_message *device_state;

   if (ast_device_state_message_type() != stasis_message_type(msg)) {
      return;
   }

   device_state = stasis_message_data(msg);
   if (device_state->cachable == AST_DEVSTATE_CACHABLE || !device_state->eid) {
      /* Ignore cacheable and aggregate messages. */
      return;
   }

   /*
    * Non-cacheable device state aggregates are just the
    * device state republished as the aggregate.
    */
   ast_publish_device_state_full(device_state->device, device_state->state,
      device_state->cachable, NULL);
}

static void device_state_engine_cleanup(void)
{
   shuttingdown = 1;
   AST_LIST_LOCK(&state_changes);
   ast_cond_signal(&change_pending);
   AST_LIST_UNLOCK(&state_changes);

   if (change_thread != AST_PTHREADT_NULL) {
      pthread_join(change_thread, NULL);
   }
}

/*! \brief Initialize the device state engine in separate thread */
int ast_device_state_engine_init(void)
{
   ast_cond_init(&change_pending, NULL);
   if (ast_pthread_create_background(&change_thread, NULL, do_devstate_changes, NULL) < 0) {
      ast_log(LOG_ERROR, "Unable to start device state change thread.\n");
      return -1;
   }
   ast_register_cleanup(device_state_engine_cleanup);

   return 0;
}

void ast_devstate_aggregate_init(struct ast_devstate_aggregate *agg)
{
   memset(agg, 0, sizeof(*agg));
   agg->state = AST_DEVICE_INVALID;
}

void ast_devstate_aggregate_add(struct ast_devstate_aggregate *agg, enum ast_device_state state)
{
   static enum ast_device_state state_order[] = {
      1, /* AST_DEVICE_UNKNOWN */
      3, /* AST_DEVICE_NOT_INUSE */
      6, /* AST_DEVICE_INUSE */
      7, /* AST_DEVICE_BUSY */
      0, /* AST_DEVICE_INVALID */
      2, /* AST_DEVICE_UNAVAILABLE */
      5, /* AST_DEVICE_RINGING */
      8, /* AST_DEVICE_RINGINUSE */
      4, /* AST_DEVICE_ONHOLD */
   };

   if (state == AST_DEVICE_RINGING) {
      agg->ringing = 1;
   } else if (state == AST_DEVICE_INUSE || state == AST_DEVICE_ONHOLD || state == AST_DEVICE_BUSY) {
      agg->inuse = 1;
   }

   if (agg->ringing && agg->inuse) {
      agg->state = AST_DEVICE_RINGINUSE;
   } else if (state_order[state] > state_order[agg->state]) {
      agg->state = state;
   }
}

enum ast_device_state ast_devstate_aggregate_result(struct ast_devstate_aggregate *agg)
{
   return agg->state;
}

struct stasis_topic *ast_device_state_topic_all(void)
{
   return device_state_topic_all;
}

struct stasis_cache *ast_device_state_cache(void)
{
   return device_state_cache;
}

struct stasis_topic *ast_device_state_topic_cached(void)
{
   return stasis_caching_get_topic(device_state_topic_cached);
}

struct stasis_topic *ast_device_state_topic(const char *device)
{
   return stasis_topic_pool_get_topic(device_state_topic_pool, device);
}

int ast_device_state_clear_cache(const char *device)
{
   struct stasis_message *cached_msg;
   struct stasis_message *msg;

   cached_msg = stasis_cache_get_by_eid(ast_device_state_cache(),
      ast_device_state_message_type(), device, &ast_eid_default);
   if (!cached_msg) {
      /* nothing to clear */
      return -1;
   }

   msg = stasis_cache_clear_create(cached_msg);
   if (msg) {
      stasis_publish(ast_device_state_topic(device), msg);
   }
   ao2_cleanup(msg);
   ao2_cleanup(cached_msg);
   return 0;
}

int ast_publish_device_state_full(
   const char *device,
   enum ast_device_state state,
   enum ast_devstate_cache cachable,
   struct ast_eid *eid)
{
   RAII_VAR(struct ast_device_state_message *, device_state, NULL, ao2_cleanup);
   RAII_VAR(struct stasis_message *, message, NULL, ao2_cleanup);
   struct stasis_topic *topic;

   ast_assert(!ast_strlen_zero(device));

   if (!ast_device_state_message_type()) {
      return -1;
   }

   device_state = device_state_alloc(device, state, cachable, eid);
   if (!device_state) {
      return -1;
   }

   message = stasis_message_create_full(ast_device_state_message_type(), device_state,
      eid);
   if (!message) {
      return -1;
   }

   /* When a device state is to be cached it is likely that something
    * external will either be monitoring it or will want to pull the
    * information from the cache, so we always publish to the device
    * specific topic. Cachable updates traditionally come from such things
    * as a SIP or PJSIP device.
    * When a device state is not to be cached we only publish to its
    * specific topic if something has already created the topic. Publishing
    * to its topic otherwise would create the topic, which may not be
    * necessary as it could be an ephemeral device. Uncachable updates
    * traditionally come from such things as Local channels.
    */
   if (cachable || stasis_topic_pool_topic_exists(device_state_topic_pool, device)) {
      topic = ast_device_state_topic(device);
   } else {
      topic = ast_device_state_topic_all();
   }

   if (!topic) {
      return -1;
   }

   stasis_publish(topic, message);
   return 0;
}

static const char *device_state_get_id(struct stasis_message *message)
{
   struct ast_device_state_message *device_state;

   if (ast_device_state_message_type() != stasis_message_type(message)) {
      return NULL;
   }

   device_state = stasis_message_data(message);
   if (device_state->cachable == AST_DEVSTATE_NOT_CACHABLE) {
      return NULL;
   }

   return device_state->device;
}

/*!
 * \internal
 * \brief Callback to publish the aggregate device state cache entry message.
 * \since 12.2.0
 *
 * \param cache_topic Caching topic the aggregate message may be published over.
 * \param aggregate The aggregate shapshot message to publish.
 *
 * \return Nothing
 */
static void device_state_aggregate_publish(struct stasis_topic *cache_topic, struct stasis_message *aggregate)
{
   const char *device;
   struct stasis_topic *device_specific_topic;

   device = device_state_get_id(aggregate);
   if (!device) {
      return;
   }
   device_specific_topic = ast_device_state_topic(device);
   if (!device_specific_topic) {
      return;
   }

   stasis_publish(device_specific_topic, aggregate);
}

/*!
 * \internal
 * \brief Callback to calculate the aggregate device state cache entry.
 * \since 12.2.0
 *
 * \param entry Cache entry to calculate a new aggregate snapshot.
 * \param new_snapshot The shapshot that is being updated.
 *
 * \note Return a ref bumped pointer from stasis_cache_entry_get_aggregate()
 * if a new aggregate could not be calculated because of error.
 *
 * \return New aggregate-snapshot calculated on success.
 * Caller has a reference on return.
 */
static struct stasis_message *device_state_aggregate_calc(struct stasis_cache_entry *entry, struct stasis_message *new_snapshot)
{
   struct stasis_message *aggregate_snapshot;
   struct stasis_message *snapshot;
   struct ast_device_state_message *device_state;
   const char *device = NULL;
   struct ast_devstate_aggregate aggregate;
   int idx;

   if (!ast_device_state_message_type()) {
      return NULL;
   }

   /* Determine the new aggregate device state. */
   ast_devstate_aggregate_init(&aggregate);
   snapshot = stasis_cache_entry_get_local(entry);
   if (snapshot) {
      device_state = stasis_message_data(snapshot);
      device = device_state->device;
      ast_devstate_aggregate_add(&aggregate, device_state->state);
   }
   for (idx = 0; ; ++idx) {
      snapshot = stasis_cache_entry_get_remote(entry, idx);
      if (!snapshot) {
         break;
      }

      device_state = stasis_message_data(snapshot);
      device = device_state->device;
      ast_devstate_aggregate_add(&aggregate, device_state->state);
   }

   if (!device) {
      /* There are no device states cached.  Delete the aggregate. */
      return NULL;
   }

   snapshot = stasis_cache_entry_get_aggregate(entry);
   if (snapshot) {
      device_state = stasis_message_data(snapshot);
      if (device_state->state == ast_devstate_aggregate_result(&aggregate)) {
         /* Aggregate device state did not change. */
         return ao2_bump(snapshot);
      }
   }

   device_state = device_state_alloc(device, ast_devstate_aggregate_result(&aggregate),
      AST_DEVSTATE_CACHABLE, NULL);
   if (!device_state) {
      /* Bummer.  We have to keep the old aggregate snapshot. */
      return ao2_bump(snapshot);
   }
   aggregate_snapshot = stasis_message_create_full(ast_device_state_message_type(),
      device_state, NULL);
   ao2_cleanup(device_state);
   if (!aggregate_snapshot) {
      /* Bummer.  We have to keep the old aggregate snapshot. */
      return ao2_bump(snapshot);
   }

   return aggregate_snapshot;
}

static void devstate_cleanup(void)
{
   devstate_message_sub = stasis_unsubscribe_and_join(devstate_message_sub);
   device_state_topic_cached = stasis_caching_unsubscribe_and_join(device_state_topic_cached);

   ao2_cleanup(device_state_cache);
   device_state_cache = NULL;

   ao2_cleanup(device_state_topic_pool);
   device_state_topic_pool = NULL;

   ao2_cleanup(device_state_topic_all);
   device_state_topic_all = NULL;

   STASIS_MESSAGE_TYPE_CLEANUP(ast_device_state_message_type);
}

int devstate_init(void)
{
   ast_register_cleanup(devstate_cleanup);

   if (STASIS_MESSAGE_TYPE_INIT(ast_device_state_message_type) != 0) {
      return -1;
   }
   device_state_topic_all = stasis_topic_create("devicestate:all");
   if (!device_state_topic_all) {
      return -1;
   }
   device_state_topic_pool = stasis_topic_pool_create(ast_device_state_topic_all());
   if (!device_state_topic_pool) {
      return -1;
   }
   device_state_cache = stasis_cache_create_full(device_state_get_id,
      device_state_aggregate_calc, device_state_aggregate_publish);
   if (!device_state_cache) {
      return -1;
   }
   device_state_topic_cached = stasis_caching_topic_create(ast_device_state_topic_all(),
      device_state_cache);
   if (!device_state_topic_cached) {
      return -1;
   }
   stasis_caching_accept_message_type(device_state_topic_cached, ast_device_state_message_type());
   stasis_caching_set_filter(device_state_topic_cached, STASIS_SUBSCRIPTION_FILTER_SELECTIVE);

   devstate_message_sub = stasis_subscribe(ast_device_state_topic_all(),
      devstate_change_cb, NULL);
   if (!devstate_message_sub) {
      ast_log(LOG_ERROR, "Failed to create subscription creating uncached device state aggregate events.\n");
      return -1;
   }
   stasis_subscription_accept_message_type(devstate_message_sub, ast_device_state_message_type());
   stasis_subscription_set_filter(devstate_message_sub, STASIS_SUBSCRIPTION_FILTER_SELECTIVE);

   return 0;
}

static struct ast_manager_event_blob *devstate_to_ami(struct stasis_message *msg)
{
   struct ast_device_state_message *dev_state;

   dev_state = stasis_message_data(msg);

   /* Ignore non-aggregate states */
   if (dev_state->eid) {
      return NULL;
   }

   return ast_manager_event_blob_create(EVENT_FLAG_CALL, "DeviceStateChange",
      "Device: %s\r\n"
      "State: %s\r\n",
      dev_state->device, ast_devstate_str(dev_state->state));
}

/*! \brief Convert a \ref stasis_message to a \ref ast_event */
static struct ast_event *devstate_to_event(struct stasis_message *message)
{
   struct ast_event *event;
   struct ast_device_state_message *device_state;

   if (!message) {
      return NULL;
   }

   device_state = stasis_message_data(message);

   if (device_state->eid) {
      event = ast_event_new(AST_EVENT_DEVICE_STATE_CHANGE,
                   AST_EVENT_IE_DEVICE, AST_EVENT_IE_PLTYPE_STR, device_state->device,
                   AST_EVENT_IE_STATE, AST_EVENT_IE_PLTYPE_UINT, device_state->state,
                   AST_EVENT_IE_CACHABLE, AST_EVENT_IE_PLTYPE_UINT, device_state->cachable,
                   AST_EVENT_IE_EID, AST_EVENT_IE_PLTYPE_RAW, device_state->eid, sizeof(*device_state->eid),
                   AST_EVENT_IE_END);
   } else {
      event = ast_event_new(AST_EVENT_DEVICE_STATE,
                   AST_EVENT_IE_DEVICE, AST_EVENT_IE_PLTYPE_STR, device_state->device,
                   AST_EVENT_IE_STATE, AST_EVENT_IE_PLTYPE_UINT, device_state->state,
                   AST_EVENT_IE_CACHABLE, AST_EVENT_IE_PLTYPE_UINT, device_state->cachable,
                   AST_EVENT_IE_END);
   }

   return event;
}