devicestate.c

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/*
 * Asterisk -- An open source telephony toolkit.
 *
 * Copyright (C) 1999 - 2008, Digium, Inc.
 *
 * Mark Spencer <markster@digium.com>
 * Russell Bryant <russell@digium.com>
 *
 * 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 <markster@digium.com>
 * \author Russell Bryant <russell@digium.com>
 *
 *  \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 ast_extension_states "AstENUM"
 *      \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">
            <since>
                <version>13.0.0</version>
            </since>
            <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 }, /* Audible ringback tone */
    { AST_STATE_RINGING,         AST_DEVICE_RINGING }, /* Actual 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 snapshot message to publish.
 */
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 snapshot 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;
}