res_stasis.c

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/*
 * Asterisk -- An open source telephony toolkit.
 *
 * Copyright (C) 2012 - 2013, Digium, Inc.
 *
 * David M. Lee, II <[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 Stasis application support.
 *
 * \author David M. Lee, II <[email protected]>
 *
 * <code>res_stasis.so</code> brings together the various components of the
 * Stasis application infrastructure.
 *
 * First, there's the Stasis application handler, stasis_app_exec(). This is
 * called by <code>app_stasis.so</code> to give control of a channel to the
 * Stasis application code from the dialplan.
 *
 * While a channel is in stasis_app_exec(), it has a \ref stasis_app_control
 * object, which may be used to control the channel.
 *
 * To control the channel, commands may be sent to channel using
 * stasis_app_send_command() and stasis_app_send_async_command().
 *
 * Alongside this, applications may be registered/unregistered using
 * stasis_app_register()/stasis_app_unregister(). While a channel is in Stasis,
 * events received on the channel's topic are converted to JSON and forwarded to
 * the \ref stasis_app_cb. The application may also subscribe to the channel to
 * continue to receive messages even after the channel has left Stasis, but it
 * will not be able to control it.
 *
 * Given all the stuff that comes together in this module, it's been broken up
 * into several pieces that are in <code>res/stasis/</code> and compiled into
 * <code>res_stasis.so</code>.
 */

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

#include "asterisk.h"

#include "asterisk/astobj2.h"
#include "asterisk/callerid.h"
#include "asterisk/module.h"
#include "asterisk/stasis_app_impl.h"
#include "asterisk/stasis_channels.h"
#include "asterisk/stasis_bridges.h"
#include "asterisk/stasis_endpoints.h"
#include "asterisk/stasis_message_router.h"
#include "asterisk/strings.h"
#include "stasis/app.h"
#include "stasis/control.h"
#include "stasis/messaging.h"
#include "stasis/stasis_bridge.h"
#include "asterisk/core_unreal.h"
#include "asterisk/musiconhold.h"
#include "asterisk/causes.h"
#include "asterisk/stringfields.h"
#include "asterisk/bridge_after.h"
#include "asterisk/format_cache.h"

/*! Time to wait for a frame in the application */
#define MAX_WAIT_MS 200

/*!
 * \brief Number of buckets for the Stasis application hash table.  Remember to
 * keep it a prime number!
 */
#define APPS_NUM_BUCKETS 127

/*!
 * \brief Number of buckets for the Stasis application hash table.  Remember to
 * keep it a prime number!
 */
#define CONTROLS_NUM_BUCKETS 127

/*!
 * \brief Number of buckets for the Stasis bridges hash table.  Remember to
 * keep it a prime number!
 */
#define BRIDGES_NUM_BUCKETS 127

/*!
 * \brief Stasis application container.
 */
struct ao2_container *apps_registry;

struct ao2_container *app_controls;

struct ao2_container *app_bridges;

struct ao2_container *app_bridges_moh;

struct ao2_container *app_bridges_playback;

/*!
 * \internal \brief List of registered event sources.
 */
AST_RWLIST_HEAD_STATIC(event_sources, stasis_app_event_source);

static struct ast_json *stasis_end_to_json(struct stasis_message *message,
      const struct stasis_message_sanitizer *sanitize)
{
   struct ast_channel_blob *payload = stasis_message_data(message);
   struct ast_json *msg;

   if (sanitize && sanitize->channel_snapshot &&
         sanitize->channel_snapshot(payload->snapshot)) {
      return NULL;
   }

   msg = ast_json_pack("{s: s, s: O, s: o}",
      "type", "StasisEnd",
      "timestamp", ast_json_object_get(payload->blob, "timestamp"),
      "channel", ast_channel_snapshot_to_json(payload->snapshot, sanitize));
   if (!msg) {
      ast_log(LOG_ERROR, "Failed to pack JSON for StasisEnd message\n");
      return NULL;
   }

   return msg;
}

STASIS_MESSAGE_TYPE_DEFN_LOCAL(end_message_type,
   .to_json = stasis_end_to_json);

struct start_message_blob {
   struct ast_channel_snapshot *channel;     /*!< Channel that is entering Stasis() */
   struct ast_channel_snapshot *replace_channel;   /*!< Channel that is being replaced (optional) */
   struct ast_json *blob;           /*!< JSON blob containing timestamp and args */
};

static struct ast_json *stasis_start_to_json(struct stasis_message *message,
      const struct stasis_message_sanitizer *sanitize)
{
   struct start_message_blob *payload = stasis_message_data(message);
   struct ast_json *msg;

   if (sanitize && sanitize->channel_snapshot &&
         sanitize->channel_snapshot(payload->channel)) {
      return NULL;
   }

   msg = ast_json_pack("{s: s, s: O, s: O, s: o}",
      "type", "StasisStart",
      "timestamp", ast_json_object_get(payload->blob, "timestamp"),
      "args", ast_json_object_get(payload->blob, "args"),
      "channel", ast_channel_snapshot_to_json(payload->channel, NULL));
   if (!msg) {
      ast_log(LOG_ERROR, "Failed to pack JSON for StasisStart message\n");
      return NULL;
   }

   if (payload->replace_channel) {
      int res = ast_json_object_set(msg, "replace_channel",
         ast_channel_snapshot_to_json(payload->replace_channel, NULL));

      if (res) {
         ast_json_unref(msg);
         ast_log(LOG_ERROR, "Failed to append JSON for StasisStart message\n");
         return NULL;
      }
   }

   return msg;
}

STASIS_MESSAGE_TYPE_DEFN_LOCAL(start_message_type,
   .to_json = stasis_start_to_json);

/*! AO2 hash function for \ref app */
static int app_hash(const void *obj, const int flags)
{
   const struct stasis_app *app;
   const char *key;

   switch (flags & OBJ_SEARCH_MASK) {
   case OBJ_SEARCH_KEY:
      key = obj;
      break;
   case OBJ_SEARCH_OBJECT:
      app = obj;
      key = stasis_app_name(app);
      break;
   default:
      /* Hash can only work on something with a full key. */
      ast_assert(0);
      return 0;
   }
   return ast_str_hash(key);
}

/*! AO2 comparison function for \ref app */
static int app_compare(void *obj, void *arg, int flags)
{
   const struct stasis_app *object_left = obj;
   const struct stasis_app *object_right = arg;
   const char *right_key = arg;
   int cmp;

   switch (flags & OBJ_SEARCH_MASK) {
   case OBJ_SEARCH_OBJECT:
      right_key = stasis_app_name(object_right);
      /* Fall through */
   case OBJ_SEARCH_KEY:
      cmp = strcmp(stasis_app_name(object_left), right_key);
      break;
   case OBJ_SEARCH_PARTIAL_KEY:
      /*
       * We could also use a partial key struct containing a length
       * so strlen() does not get called for every comparison instead.
       */
      cmp = strncmp(stasis_app_name(object_left), right_key, strlen(right_key));
      break;
   default:
      /*
       * What arg points to is specific to this traversal callback
       * and has no special meaning to astobj2.
       */
      cmp = 0;
      break;
   }
   if (cmp) {
      return 0;
   }
   /*
    * At this point the traversal callback is identical to a sorted
    * container.
    */
   return CMP_MATCH;
}

/*! AO2 hash function for \ref stasis_app_control */
static int control_hash(const void *obj, const int flags)
{
   const struct stasis_app_control *control;
   const char *key;

   switch (flags & OBJ_SEARCH_MASK) {
   case OBJ_SEARCH_KEY:
      key = obj;
      break;
   case OBJ_SEARCH_OBJECT:
      control = obj;
      key = stasis_app_control_get_channel_id(control);
      break;
   default:
      /* Hash can only work on something with a full key. */
      ast_assert(0);
      return 0;
   }
   return ast_str_hash(key);
}

/*! AO2 comparison function for \ref stasis_app_control */
static int control_compare(void *obj, void *arg, int flags)
{
   const struct stasis_app_control *object_left = obj;
   const struct stasis_app_control *object_right = arg;
   const char *right_key = arg;
   int cmp;

   switch (flags & OBJ_SEARCH_MASK) {
   case OBJ_SEARCH_OBJECT:
      right_key = stasis_app_control_get_channel_id(object_right);
      /* Fall through */
   case OBJ_SEARCH_KEY:
      cmp = strcmp(stasis_app_control_get_channel_id(object_left), right_key);
      break;
   case OBJ_SEARCH_PARTIAL_KEY:
      /*
       * We could also use a partial key struct containing a length
       * so strlen() does not get called for every comparison instead.
       */
      cmp = strncmp(stasis_app_control_get_channel_id(object_left), right_key, strlen(right_key));
      break;
   default:
      /*
       * What arg points to is specific to this traversal callback
       * and has no special meaning to astobj2.
       */
      cmp = 0;
      break;
   }
   if (cmp) {
      return 0;
   }
   /*
    * At this point the traversal callback is identical to a sorted
    * container.
    */
   return CMP_MATCH;
}

static int cleanup_cb(void *obj, void *arg, int flags)
{
   struct stasis_app *app = obj;

   if (!app_is_finished(app)) {
      return 0;
   }

   ast_verb(1, "Shutting down application '%s'\n", stasis_app_name(app));
   app_shutdown(app);

   return CMP_MATCH;

}

/*!
 * \brief Clean up any old apps that we don't need any more.
 */
static void cleanup(void)
{
   ao2_callback(apps_registry, OBJ_MULTIPLE | OBJ_NODATA | OBJ_UNLINK,
      cleanup_cb, NULL);
}

struct stasis_app_control *stasis_app_control_create(struct ast_channel *chan)
{
   return control_create(chan, NULL);
}

struct stasis_app_control *stasis_app_control_find_by_channel(
   const struct ast_channel *chan)
{
   if (chan == NULL) {
      return NULL;
   }

   return stasis_app_control_find_by_channel_id(
      ast_channel_uniqueid(chan));
}

struct stasis_app_control *stasis_app_control_find_by_channel_id(
   const char *channel_id)
{
   return ao2_find(app_controls, channel_id, OBJ_SEARCH_KEY);
}

/*! AO2 hash function for bridges container  */
static int bridges_hash(const void *obj, const int flags)
{
   const struct ast_bridge *bridge;
   const char *key;

   switch (flags & OBJ_SEARCH_MASK) {
   case OBJ_SEARCH_KEY:
      key = obj;
      break;
   case OBJ_SEARCH_OBJECT:
      bridge = obj;
      key = bridge->uniqueid;
      break;
   default:
      /* Hash can only work on something with a full key. */
      ast_assert(0);
      return 0;
   }
   return ast_str_hash(key);
}

/*! AO2 comparison function for bridges container */
static int bridges_compare(void *obj, void *arg, int flags)
{
   const struct ast_bridge *object_left = obj;
   const struct ast_bridge *object_right = arg;
   const char *right_key = arg;
   int cmp;

   switch (flags & OBJ_SEARCH_MASK) {
   case OBJ_SEARCH_OBJECT:
      right_key = object_right->uniqueid;
      /* Fall through */
   case OBJ_SEARCH_KEY:
      cmp = strcmp(object_left->uniqueid, right_key);
      break;
   case OBJ_SEARCH_PARTIAL_KEY:
      /*
       * We could also use a partial key struct containing a length
       * so strlen() does not get called for every comparison instead.
       */
      cmp = strncmp(object_left->uniqueid, right_key, strlen(right_key));
      break;
   default:
      /*
       * What arg points to is specific to this traversal callback
       * and has no special meaning to astobj2.
       */
      cmp = 0;
      break;
   }
   if (cmp) {
      return 0;
   }
   /*
    * At this point the traversal callback is identical to a sorted
    * container.
    */
   return CMP_MATCH;
}

/*!
 *  Used with app_bridges_moh and app_bridge_control, they provide links
 *  between bridges and channels used for ARI application purposes
 */
struct stasis_app_bridge_channel_wrapper {
   AST_DECLARE_STRING_FIELDS(
      AST_STRING_FIELD(channel_id);
      AST_STRING_FIELD(bridge_id);
   );
};

/*! AO2 comparison function for bridges moh container */
static int bridges_channel_compare(void *obj, void *arg, int flags)
{
   const struct stasis_app_bridge_channel_wrapper *object_left = obj;
   const struct stasis_app_bridge_channel_wrapper *object_right = arg;
   const char *right_key = arg;
   int cmp;

   switch (flags & OBJ_SEARCH_MASK) {
   case OBJ_SEARCH_OBJECT:
         right_key = object_right->bridge_id;
   case OBJ_SEARCH_KEY:
         cmp = strcmp(object_left->bridge_id, right_key);
         break;
   case OBJ_SEARCH_PARTIAL_KEY:
         cmp = strncmp(object_left->bridge_id, right_key, strlen(right_key));
         break;
   default:
         cmp = 0;
         break;
   }
   if (cmp) {
      return 0;
   }
   return CMP_MATCH;
}

static void stasis_app_bridge_channel_wrapper_destructor(void *obj)
{
   struct stasis_app_bridge_channel_wrapper *wrapper = obj;
   ast_string_field_free_memory(wrapper);
}

/*! AO2 hash function for the bridges moh container */
static int bridges_channel_hash_fn(const void *obj, const int flags)
{
   const struct stasis_app_bridge_channel_wrapper *wrapper;
   const char *key;

   switch (flags & OBJ_SEARCH_MASK) {
   case OBJ_SEARCH_KEY:
      key = obj;
      break;
   case OBJ_SEARCH_OBJECT:
      wrapper = obj;
      key = wrapper->bridge_id;
      break;
   default:
      /* Hash can only work on something with a full key. */
      ast_assert(0);
      return 0;
   }
   return ast_str_hash(key);
}

static int bridges_channel_sort_fn(const void *obj_left, const void *obj_right, const int flags)
{
   const struct stasis_app_bridge_channel_wrapper *left = obj_left;
   const struct stasis_app_bridge_channel_wrapper *right = obj_right;
   const char *right_key = obj_right;
   int cmp;

   switch (flags & OBJ_SEARCH_MASK) {
   case OBJ_SEARCH_OBJECT:
      right_key = right->bridge_id;
      /* Fall through */
   case OBJ_SEARCH_KEY:
      cmp = strcmp(left->bridge_id, right_key);
      break;
   case OBJ_SEARCH_PARTIAL_KEY:
      cmp = strncmp(left->bridge_id, right_key, strlen(right_key));
      break;
   default:
      /* Sort can only work on something with a full or partial key. */
      ast_assert(0);
      cmp = 0;
      break;
   }
   return cmp;
}

/*! Request a bridge MOH channel */
static struct ast_channel *prepare_bridge_moh_channel(void)
{
   struct ast_channel *chan;
   struct ast_format_cap *cap;

   cap = ast_format_cap_alloc(AST_FORMAT_CAP_FLAG_DEFAULT);
   if (!cap) {
      return NULL;
   }

   ast_format_cap_append(cap, ast_format_slin, 0);

   chan = ast_request("Announcer", cap, NULL, NULL, "ARI_MOH", NULL);
   ao2_ref(cap, -1);

   return chan;
}

/*! Provides the moh channel with a thread so it can actually play its music */
static void *moh_channel_thread(void *data)
{
   struct stasis_app_bridge_channel_wrapper *moh_wrapper = data;
   struct ast_channel *moh_channel = ast_channel_get_by_name(moh_wrapper->channel_id);
   struct ast_frame *f;

   if (!moh_channel) {
      ao2_unlink(app_bridges_moh, moh_wrapper);
      ao2_ref(moh_wrapper, -1);
      return NULL;
   }

   /* Read and discard any frame coming from the stasis bridge. */
   for (;;) {
      if (ast_waitfor(moh_channel, -1) < 0) {
         /* Error or hungup */
         break;
      }

      f = ast_read(moh_channel);
      if (!f) {
         /* Hungup */
         break;
      }
      ast_frfree(f);
   }

   ao2_unlink(app_bridges_moh, moh_wrapper);
   ao2_ref(moh_wrapper, -1);

   ast_moh_stop(moh_channel);
   ast_hangup(moh_channel);

   return NULL;
}

/*!
 * \internal
 * \brief Creates, pushes, and links a channel for playing music on hold to bridge
 *
 * \param bridge Which bridge this moh channel exists for
 *
 * \retval NULL if the channel could not be created, pushed, or linked
 * \retval Reference to the channel on success
 */
static struct ast_channel *bridge_moh_create(struct ast_bridge *bridge)
{
   struct stasis_app_bridge_channel_wrapper *new_wrapper;
   struct ast_channel *chan;
   pthread_t threadid;

   chan = prepare_bridge_moh_channel();
   if (!chan) {
      return NULL;
   }

   if (stasis_app_channel_unreal_set_internal(chan)) {
      ast_hangup(chan);
      return NULL;
   }

   if (ast_unreal_channel_push_to_bridge(chan, bridge,
      AST_BRIDGE_CHANNEL_FLAG_IMMOVABLE | AST_BRIDGE_CHANNEL_FLAG_LONELY)) {
      ast_hangup(chan);
      return NULL;
   }

   new_wrapper = ao2_alloc_options(sizeof(*new_wrapper),
      stasis_app_bridge_channel_wrapper_destructor, AO2_ALLOC_OPT_LOCK_NOLOCK);
   if (!new_wrapper) {
      ast_hangup(chan);
      return NULL;
   }

   if (ast_string_field_init(new_wrapper, AST_UUID_STR_LEN + AST_CHANNEL_NAME)
      || ast_string_field_set(new_wrapper, bridge_id, bridge->uniqueid)
      || ast_string_field_set(new_wrapper, channel_id, ast_channel_uniqueid(chan))) {
      ao2_ref(new_wrapper, -1);
      ast_hangup(chan);
      return NULL;
   }

   if (!ao2_link_flags(app_bridges_moh, new_wrapper, OBJ_NOLOCK)) {
      ao2_ref(new_wrapper, -1);
      ast_hangup(chan);
      return NULL;
   }

   /* Pass the new_wrapper ref to moh_channel_thread() */
   if (ast_pthread_create_detached(&threadid, NULL, moh_channel_thread, new_wrapper)) {
      ast_log(LOG_ERROR, "Failed to create channel thread. Abandoning MOH channel creation.\n");
      ao2_unlink_flags(app_bridges_moh, new_wrapper, OBJ_NOLOCK);
      ao2_ref(new_wrapper, -1);
      ast_hangup(chan);
      return NULL;
   }

   return chan;
}

struct ast_channel *stasis_app_bridge_moh_channel(struct ast_bridge *bridge)
{
   struct ast_channel *chan;
   struct stasis_app_bridge_channel_wrapper *moh_wrapper;

   ao2_lock(app_bridges_moh);
   moh_wrapper = ao2_find(app_bridges_moh, bridge->uniqueid, OBJ_SEARCH_KEY | OBJ_NOLOCK);
   if (!moh_wrapper) {
      chan = bridge_moh_create(bridge);
   }
   ao2_unlock(app_bridges_moh);

   if (moh_wrapper) {
      chan = ast_channel_get_by_name(moh_wrapper->channel_id);
      ao2_ref(moh_wrapper, -1);
   }

   return chan;
}

int stasis_app_bridge_moh_stop(struct ast_bridge *bridge)
{
   struct stasis_app_bridge_channel_wrapper *moh_wrapper;
   struct ast_channel *chan;

   moh_wrapper = ao2_find(app_bridges_moh, bridge->uniqueid, OBJ_SEARCH_KEY | OBJ_UNLINK);
   if (!moh_wrapper) {
      return -1;
   }

   chan = ast_channel_get_by_name(moh_wrapper->channel_id);
   ao2_ref(moh_wrapper, -1);
   if (!chan) {
      return -1;
   }

   ast_moh_stop(chan);
   ast_softhangup(chan, AST_CAUSE_NORMAL_CLEARING);
   ao2_cleanup(chan);

   return 0;
}

/*! Removes the bridge to playback channel link */
static void remove_bridge_playback(char *bridge_id)
{
   struct stasis_app_bridge_channel_wrapper *wrapper;
   struct stasis_app_control *control;

   wrapper = ao2_find(app_bridges_playback, bridge_id, OBJ_SEARCH_KEY | OBJ_UNLINK);

   if (wrapper) {
      control = stasis_app_control_find_by_channel_id(wrapper->channel_id);
      if (control) {
         ao2_unlink(app_controls, control);
         ao2_ref(control, -1);
      }
      ao2_ref(wrapper, -1);
   }
   ast_free(bridge_id);
}

static void playback_after_bridge_cb_failed(enum ast_bridge_after_cb_reason reason, void *data)
{
   char *bridge_id = data;

   remove_bridge_playback(bridge_id);
}

static void playback_after_bridge_cb(struct ast_channel *chan, void *data)
{
   char *bridge_id = data;

   remove_bridge_playback(bridge_id);
}

int stasis_app_bridge_playback_channel_add(struct ast_bridge *bridge,
   struct ast_channel *chan,
   struct stasis_app_control *control)
{
   RAII_VAR(struct stasis_app_bridge_channel_wrapper *, new_wrapper, NULL, ao2_cleanup);
   char *bridge_id = ast_strdup(bridge->uniqueid);

   if (!bridge_id) {
      return -1;
   }

   if (ast_bridge_set_after_callback(chan,
      playback_after_bridge_cb, playback_after_bridge_cb_failed, bridge_id)) {
      ast_free(bridge_id);
      return -1;
   }

   new_wrapper = ao2_alloc_options(sizeof(*new_wrapper),
      stasis_app_bridge_channel_wrapper_destructor, AO2_ALLOC_OPT_LOCK_NOLOCK);
   if (!new_wrapper) {
      return -1;
   }

   if (ast_string_field_init(new_wrapper, 32)) {
      return -1;
   }

   ast_string_field_set(new_wrapper, bridge_id, bridge->uniqueid);
   ast_string_field_set(new_wrapper, channel_id, ast_channel_uniqueid(chan));

   if (!ao2_link(app_bridges_playback, new_wrapper)) {
      return -1;
   }

   ao2_link(app_controls, control);
   return 0;
}

void stasis_app_bridge_playback_channel_remove(char *bridge_id,
   struct stasis_app_control *control)
{
   struct stasis_app_bridge_channel_wrapper *wrapper;

   wrapper = ao2_find(app_bridges_playback, bridge_id, OBJ_SEARCH_KEY | OBJ_UNLINK);
   if (wrapper) {
      /* If wrapper is not found, then that means the after bridge callback has been
       * called or is in progress. No need to unlink the control here since that has
       * been done or is about to be done in the after bridge callback
       */
      ao2_unlink(app_controls, control);
      ao2_ref(wrapper, -1);
   }
}

struct ast_channel *stasis_app_bridge_playback_channel_find(struct ast_bridge *bridge)
{
   struct stasis_app_bridge_channel_wrapper *playback_wrapper;
   struct ast_channel *chan;

   playback_wrapper = ao2_find(app_bridges_playback, bridge->uniqueid, OBJ_SEARCH_KEY);
   if (!playback_wrapper) {
      return NULL;
   }

   chan = ast_channel_get_by_name(playback_wrapper->channel_id);
   ao2_ref(playback_wrapper, -1);
   return chan;
}

struct ast_bridge *stasis_app_bridge_find_by_id(
   const char *bridge_id)
{
   return ao2_find(app_bridges, bridge_id, OBJ_SEARCH_KEY);
}


/*!
 * \brief In addition to running ao2_cleanup(), this function also removes the
 * object from the app_controls container.
 */
static void control_unlink(struct stasis_app_control *control)
{
   if (!control) {
      return;
   }

   ao2_unlink(app_controls, control);
   ao2_cleanup(control);
}

static struct ast_bridge *bridge_create_common(const char *type, const char *name, const char *id, int invisible)
{
   struct ast_bridge *bridge;
   char *requested_type, *requested_types = ast_strdupa(S_OR(type, "mixing"));
   int capabilities = 0;
   int flags = AST_BRIDGE_FLAG_MERGE_INHIBIT_FROM | AST_BRIDGE_FLAG_MERGE_INHIBIT_TO
      | AST_BRIDGE_FLAG_SWAP_INHIBIT_FROM | AST_BRIDGE_FLAG_SWAP_INHIBIT_TO
      | AST_BRIDGE_FLAG_TRANSFER_BRIDGE_ONLY;
   enum ast_bridge_video_mode_type video_mode = AST_BRIDGE_VIDEO_MODE_TALKER_SRC;

   if (invisible) {
      flags |= AST_BRIDGE_FLAG_INVISIBLE;
   }

   while ((requested_type = strsep(&requested_types, ","))) {
      requested_type = ast_strip(requested_type);

      if (!strcmp(requested_type, "mixing")) {
         capabilities |= STASIS_BRIDGE_MIXING_CAPABILITIES;
         flags |= AST_BRIDGE_FLAG_SMART;
      } else if (!strcmp(requested_type, "holding")) {
         capabilities |= AST_BRIDGE_CAPABILITY_HOLDING;
      } else if (!strcmp(requested_type, "dtmf_events") ||
         !strcmp(requested_type, "proxy_media")) {
         capabilities &= ~AST_BRIDGE_CAPABILITY_NATIVE;
      } else if (!strcmp(requested_type, "video_sfu")) {
         video_mode = AST_BRIDGE_VIDEO_MODE_SFU;
      } else if (!strcmp(requested_type, "video_single")) {
         video_mode = AST_BRIDGE_VIDEO_MODE_SINGLE_SRC;
      }
   }

   /* For an SFU video bridge we ensure it always remains in multimix for the best experience. */
   if (video_mode == AST_BRIDGE_VIDEO_MODE_SFU) {
      capabilities = AST_BRIDGE_CAPABILITY_MULTIMIX;
      flags &= ~AST_BRIDGE_FLAG_SMART;
   }

   if (!capabilities
      /* Holding and mixing capabilities don't mix. */
      || ((capabilities & AST_BRIDGE_CAPABILITY_HOLDING)
         && (capabilities & (STASIS_BRIDGE_MIXING_CAPABILITIES)))) {
      return NULL;
   }

   bridge = bridge_stasis_new(capabilities, flags, name, id, video_mode);
   if (bridge) {
      if (!ao2_link(app_bridges, bridge)) {
         ast_bridge_destroy(bridge, 0);
         bridge = NULL;
      }
   }

   return bridge;
}

struct ast_bridge *stasis_app_bridge_create(const char *type, const char *name, const char *id)
{
   return bridge_create_common(type, name, id, 0);
}

struct ast_bridge *stasis_app_bridge_create_invisible(const char *type, const char *name, const char *id)
{
   return bridge_create_common(type, name, id, 1);
}

void stasis_app_bridge_destroy(const char *bridge_id)
{
   struct ast_bridge *bridge = stasis_app_bridge_find_by_id(bridge_id);
   if (!bridge) {
      return;
   }
   ao2_unlink(app_bridges, bridge);
   ast_bridge_destroy(bridge, 0);
}

struct replace_channel_store {
   struct ast_channel_snapshot *snapshot;
   char *app;
};

static void replace_channel_destroy(void *obj)
{
   struct replace_channel_store *replace = obj;

   ao2_cleanup(replace->snapshot);
   ast_free(replace->app);
   ast_free(replace);
}

static const struct ast_datastore_info replace_channel_store_info = {
   .type = "replace-channel-store",
   .destroy = replace_channel_destroy,
};

static struct replace_channel_store *get_replace_channel_store(struct ast_channel *chan, int no_create)
{
   struct ast_datastore *datastore;
   struct replace_channel_store *ret;

   ast_channel_lock(chan);
   datastore = ast_channel_datastore_find(chan, &replace_channel_store_info, NULL);
   if (!datastore && !no_create) {
      datastore = ast_datastore_alloc(&replace_channel_store_info, NULL);
      if (datastore) {
         ast_channel_datastore_add(chan, datastore);
      }
   }

   if (!datastore) {
      ast_channel_unlock(chan);
      return NULL;
   }

   if (!datastore->data) {
      datastore->data = ast_calloc(1, sizeof(struct replace_channel_store));
   }

   ret = datastore->data;
   ast_channel_unlock(chan);

   return ret;
}

int app_set_replace_channel_snapshot(struct ast_channel *chan, struct ast_channel_snapshot *replace_snapshot)
{
   struct replace_channel_store *replace = get_replace_channel_store(chan, 0);

   if (!replace) {
      return -1;
   }

   ao2_replace(replace->snapshot, replace_snapshot);
   return 0;
}

int app_set_replace_channel_app(struct ast_channel *chan, const char *replace_app)
{
   struct replace_channel_store *replace = get_replace_channel_store(chan, 0);

   if (!replace) {
      return -1;
   }

   ast_free(replace->app);
   replace->app = NULL;

   if (replace_app) {
      replace->app = ast_strdup(replace_app);
      if (!replace->app) {
         return -1;
      }
   }

   return 0;
}

static struct ast_channel_snapshot *get_replace_channel_snapshot(struct ast_channel *chan)
{
   struct replace_channel_store *replace = get_replace_channel_store(chan, 1);
   struct ast_channel_snapshot *replace_channel_snapshot;

   if (!replace) {
      return NULL;
   }

   replace_channel_snapshot = replace->snapshot;
   replace->snapshot = NULL;

   return replace_channel_snapshot;
}

char *app_get_replace_channel_app(struct ast_channel *chan)
{
   struct replace_channel_store *replace = get_replace_channel_store(chan, 1);
   char *replace_channel_app;

   if (!replace) {
      return NULL;
   }

   replace_channel_app = replace->app;
   replace->app = NULL;

   return replace_channel_app;
}

static void start_message_blob_dtor(void *obj)
{
   struct start_message_blob *payload = obj;

   ao2_cleanup(payload->channel);
   ao2_cleanup(payload->replace_channel);
   ast_json_unref(payload->blob);
}

static int send_start_msg_snapshots(struct ast_channel *chan, struct stasis_app *app,
   int argc, char *argv[], struct ast_channel_snapshot *snapshot,
   struct ast_channel_snapshot *replace_channel_snapshot)
{
   struct ast_json *json_blob;
   struct ast_json *json_args;
   struct start_message_blob *payload;
   struct stasis_message *msg;
   int i;

   if (app_subscribe_channel(app, chan)) {
      ast_log(LOG_ERROR, "Error subscribing app '%s' to channel '%s'\n",
         stasis_app_name(app), ast_channel_name(chan));
      return -1;
   }

   payload = ao2_alloc(sizeof(*payload), start_message_blob_dtor);
   if (!payload) {
      ast_log(LOG_ERROR, "Error packing JSON for StasisStart message\n");
      return -1;
   }

   payload->channel = ao2_bump(snapshot);
   payload->replace_channel = ao2_bump(replace_channel_snapshot);

   json_blob = ast_json_pack("{s: s, s: o, s: []}",
      "app", stasis_app_name(app),
      "timestamp", ast_json_timeval(ast_tvnow(), NULL),
      "args");
   if (!json_blob) {
      ast_log(LOG_ERROR, "Error packing JSON for StasisStart message\n");
      ao2_ref(payload, -1);
      return -1;
   }
   payload->blob = json_blob;


   /* Append arguments to args array */
   json_args = ast_json_object_get(json_blob, "args");
   ast_assert(json_args != NULL);
   for (i = 0; i < argc; ++i) {
      int r = ast_json_array_append(json_args,
                     ast_json_string_create(argv[i]));
      if (r != 0) {
         ast_log(LOG_ERROR, "Error appending to StasisStart message\n");
         ao2_ref(payload, -1);
         return -1;
      }
   }


   msg = stasis_message_create(start_message_type(), payload);
   ao2_ref(payload, -1);
   if (!msg) {
      ast_log(LOG_ERROR, "Error sending StasisStart message\n");
      return -1;
   }

   if (replace_channel_snapshot) {
      app_unsubscribe_channel_id(app, replace_channel_snapshot->base->uniqueid);
   }
   stasis_publish(ast_app_get_topic(app), msg);
   ao2_ref(msg, -1);
   return 0;
}

static int send_start_msg(struct stasis_app *app, struct ast_channel *chan,
   int argc, char *argv[])
{
   int ret = -1;
   struct ast_channel_snapshot *snapshot;
   struct ast_channel_snapshot *replace_channel_snapshot;

   ast_assert(chan != NULL);

   replace_channel_snapshot = get_replace_channel_snapshot(chan);

   /* Set channel info */
   ast_channel_lock(chan);
   snapshot = ast_channel_snapshot_create(chan);
   ast_channel_unlock(chan);
   if (snapshot) {
      ret = send_start_msg_snapshots(chan, app, argc, argv, snapshot, replace_channel_snapshot);
      ao2_ref(snapshot, -1);
   }
   ao2_cleanup(replace_channel_snapshot);

   return ret;
}

static void remove_masquerade_store(struct ast_channel *chan);

int app_send_end_msg(struct stasis_app *app, struct ast_channel *chan)
{
   struct stasis_message_sanitizer *sanitize = stasis_app_get_sanitizer();
   struct ast_json *blob;
   struct stasis_message *msg;

   if (sanitize && sanitize->channel
      && sanitize->channel(chan)) {
      return 0;
   }

   blob = ast_json_pack("{s: s, s: o}",
      "app", stasis_app_name(app),
      "timestamp", ast_json_timeval(ast_tvnow(), NULL)
      );
   if (!blob) {
      ast_log(LOG_ERROR, "Error packing JSON for StasisEnd message\n");
      return -1;
   }

   remove_masquerade_store(chan);
   app_unsubscribe_channel(app, chan);
   msg = ast_channel_blob_create(chan, end_message_type(), blob);
   if (msg) {
      stasis_publish(ast_app_get_topic(app), msg);
   }
   ao2_cleanup(msg);
   ast_json_unref(blob);

   return 0;
}

static int masq_match_cb(void *obj, void *data, int flags)
{
   struct stasis_app_control *control = obj;
   struct ast_channel *chan = data;

   if (!strcmp(ast_channel_uniqueid(chan),
      stasis_app_control_get_channel_id(control))) {
      return CMP_MATCH;
   }

   return 0;
}

static void channel_stolen_cb(void *data, struct ast_channel *old_chan, struct ast_channel *new_chan)
{
   struct stasis_app_control *control;

   /*
    * At this point, old_chan is the channel pointer that is in Stasis() and
    * has the unknown channel's name in it while new_chan is the channel pointer
    * that is not in Stasis(), but has the guts of the channel that Stasis() knows
    * about.
    *
    * Find and unlink control since the channel has a new name/uniqueid
    * and its hash has changed.  Since the channel is leaving stasis don't
    * bother putting it back into the container.  Nobody is going to
    * remove it from the container later.
    */
   control = ao2_callback(app_controls, OBJ_UNLINK, masq_match_cb, old_chan);
   if (!control) {
      ast_log(LOG_ERROR, "Could not find control for masqueraded channel\n");
      return;
   }

   /* send the StasisEnd message to the app */
   stasis_app_channel_set_stasis_end_published(new_chan);
   app_send_end_msg(control_app(control), new_chan);

   /* remove the datastore */
   remove_masquerade_store(old_chan);

   ao2_cleanup(control);
}

static void channel_replaced_cb(void *data, struct ast_channel *old_chan, struct ast_channel *new_chan)
{
   RAII_VAR(struct ast_channel_snapshot *, new_snapshot, NULL, ao2_cleanup);
   RAII_VAR(struct ast_channel_snapshot *, old_snapshot, NULL, ao2_cleanup);
   struct stasis_app_control *control;

   /* At this point, new_chan is the channel pointer that is in Stasis() and
    * has the unknown channel's name in it while old_chan is the channel pointer
    * that is not in Stasis(), but has the guts of the channel that Stasis() knows
    * about */

   /* grab a snapshot for the channel that is jumping into Stasis() */
   new_snapshot = ast_channel_snapshot_get_latest(ast_channel_uniqueid(new_chan));
   if (!new_snapshot) {
      ast_log(LOG_ERROR, "Could not get snapshot for masquerading channel\n");
      return;
   }

   /* grab a snapshot for the channel that has been kicked out of Stasis() */
   old_snapshot = ast_channel_snapshot_get_latest(ast_channel_uniqueid(old_chan));
   if (!old_snapshot) {
      ast_log(LOG_ERROR, "Could not get snapshot for masqueraded channel\n");
      return;
   }

   /*
    * Find, unlink, and relink control since the channel has a new
    * name/uniqueid and its hash has changed.
    */
   control = ao2_callback(app_controls, OBJ_UNLINK, masq_match_cb, new_chan);
   if (!control) {
      ast_log(LOG_ERROR, "Could not find control for masquerading channel\n");
      return;
   }
   ao2_link(app_controls, control);


   /* send the StasisStart with replace_channel to the app */
   send_start_msg_snapshots(new_chan, control_app(control), 0, NULL, new_snapshot,
      old_snapshot);
   /* send the StasisEnd message to the app */
   app_send_end_msg(control_app(control), old_chan);

   ao2_cleanup(control);
}

static const struct ast_datastore_info masquerade_store_info = {
   .type = "stasis-masqerade",
   .chan_fixup = channel_stolen_cb,
   .chan_breakdown = channel_replaced_cb,
};

static int has_masquerade_store(struct ast_channel *chan)
{
   SCOPED_CHANNELLOCK(lock, chan);
   return !!ast_channel_datastore_find(chan, &masquerade_store_info, NULL);
}

static int add_masquerade_store(struct ast_channel *chan)
{
   struct ast_datastore *datastore;

   SCOPED_CHANNELLOCK(lock, chan);
   if (ast_channel_datastore_find(chan, &masquerade_store_info, NULL)) {
      return 0;
   }

   datastore = ast_datastore_alloc(&masquerade_store_info, NULL);
   if (!datastore) {
      return -1;
   }

   ast_channel_datastore_add(chan, datastore);

   return 0;
}

static void remove_masquerade_store(struct ast_channel *chan)
{
   struct ast_datastore *datastore;

   SCOPED_CHANNELLOCK(lock, chan);
   datastore = ast_channel_datastore_find(chan, &masquerade_store_info, NULL);
   if (!datastore) {
      return;
   }

   ast_channel_datastore_remove(chan, datastore);
   ast_datastore_free(datastore);
}

void stasis_app_control_execute_until_exhausted(struct ast_channel *chan, struct stasis_app_control *control)
{
   while (!control_is_done(control)) {
      int command_count;
      command_count = control_dispatch_all(control, chan);

      ao2_lock(control);

      if (control_command_count(control)) {
         /* If the command queue isn't empty, something added to the queue before it was locked. */
         ao2_unlock(control);
         continue;
      }

      if (command_count == 0 || ast_channel_fdno(chan) == -1) {
         control_mark_done(control);
         ao2_unlock(control);
         break;
      }
      ao2_unlock(control);
   }
}

int stasis_app_control_is_done(struct stasis_app_control *control)
{
   return control_is_done(control);
}

void stasis_app_control_flush_queue(struct stasis_app_control *control)
{
   control_flush_queue(control);
}

struct ast_datastore_info set_end_published_info = {
   .type = "stasis_end_published",
};

void stasis_app_channel_set_stasis_end_published(struct ast_channel *chan)
{
   struct ast_datastore *datastore;

   datastore = ast_datastore_alloc(&set_end_published_info, NULL);
   if (datastore) {
      ast_channel_lock(chan);
      ast_channel_datastore_add(chan, datastore);
      ast_channel_unlock(chan);
   }
}

int stasis_app_channel_is_stasis_end_published(struct ast_channel *chan)
{
   struct ast_datastore *datastore;

   ast_channel_lock(chan);
   datastore = ast_channel_datastore_find(chan, &set_end_published_info, NULL);
   ast_channel_unlock(chan);

   return datastore ? 1 : 0;
}

static void remove_stasis_end_published(struct ast_channel *chan)
{
   struct ast_datastore *datastore;

   ast_channel_lock(chan);
   datastore = ast_channel_datastore_find(chan, &set_end_published_info, NULL);
   if (datastore) {
      ast_channel_datastore_remove(chan, datastore);
      ast_datastore_free(datastore);
   }
   ast_channel_unlock(chan);
}

/*! /brief Stasis dialplan application callback */
int stasis_app_exec(struct ast_channel *chan, const char *app_name, int argc,
          char *argv[])
{
   RAII_VAR(struct stasis_app *, app, NULL, ao2_cleanup);
   RAII_VAR(struct stasis_app_control *, control, NULL, control_unlink);
   struct ast_bridge *bridge = NULL;
   int res = 0;
   int needs_depart;

   ast_assert(chan != NULL);

   /* Just in case there's a lingering indication that the channel has had a stasis
    * end published on it, remove that now.
    */
   remove_stasis_end_published(chan);

   if (!apps_registry) {
      return -1;
   }

   app = ao2_find(apps_registry, app_name, OBJ_SEARCH_KEY);
   if (!app) {
      ast_log(LOG_ERROR,
         "Stasis app '%s' not registered\n", app_name);
      return -1;
   }
   if (!app_is_active(app)) {
      ast_log(LOG_ERROR,
         "Stasis app '%s' not active\n", app_name);
      return -1;
   }

   control = control_create(chan, app);
   if (!control) {
      ast_log(LOG_ERROR, "Control allocation failed or Stasis app '%s' not registered\n", app_name);
      return -1;
   }

   if (!control_app(control)) {
      ast_log(LOG_ERROR, "Stasis app '%s' not registered\n", app_name);
      return -1;
   }

   if (!app_is_active(control_app(control))) {
      ast_log(LOG_ERROR, "Stasis app '%s' not active\n", app_name);
      return -1;
   }
   ao2_link(app_controls, control);

   if (add_masquerade_store(chan)) {
      ast_log(LOG_ERROR, "Failed to attach masquerade detector\n");
      return -1;
   }

   res = send_start_msg(control_app(control), chan, argc, argv);
   if (res != 0) {
      ast_log(LOG_ERROR,
         "Error sending start message to '%s'\n", app_name);
      remove_masquerade_store(chan);
      return -1;
   }

   /* Pull queued prestart commands and execute */
   control_prestart_dispatch_all(control, chan);

   while (!control_is_done(control)) {
      RAII_VAR(struct ast_frame *, f, NULL, ast_frame_dtor);
      int r;
      int command_count;
      RAII_VAR(struct ast_bridge *, last_bridge, NULL, ao2_cleanup);

      /* Check to see if a bridge absorbed our hangup frame */
      if (ast_check_hangup_locked(chan)) {
         control_mark_done(control);
         break;
      }

      /* control->next_app is only modified within the control thread, so this is safe */
      if (control_next_app(control)) {
         struct stasis_app *next_app = ao2_find(apps_registry, control_next_app(control), OBJ_SEARCH_KEY);

         if (next_app && app_is_active(next_app)) {
            int idx;
            int next_argc;
            char **next_argv;

            /* If something goes wrong in this conditional, res will need to be non-zero
             * so that the code below the exec loop knows something went wrong during a move.
             */
            if (!stasis_app_channel_is_stasis_end_published(chan)) {
               res = has_masquerade_store(chan) && app_send_end_msg(control_app(control), chan);
               if (res != 0) {
                  ast_log(LOG_ERROR,
                     "Error sending end message to %s\n", stasis_app_name(control_app(control)));
                  control_mark_done(control);
                  ao2_ref(next_app, -1);
                  break;
               }
            } else {
               remove_stasis_end_published(chan);
            }

            /* This will ao2_bump next_app, and unref the previous app by 1 */
            control_set_app(control, next_app);

            /* There's a chance that the previous application is ready for clean up, so go ahead
             * and do that now.
             */
            cleanup();

            /* We need to add another masquerade store, otherwise the leave message will
             * not show up for the correct application.
             */
            if (add_masquerade_store(chan)) {
               ast_log(LOG_ERROR, "Failed to attach masquerade detector\n");
               res = -1;
               control_mark_done(control);
               ao2_ref(next_app, -1);
               break;
            }

            /* We MUST get the size before the list, as control_next_app_args steals the elements
             * from the string vector.
             */
            next_argc = control_next_app_args_size(control);
            next_argv = control_next_app_args(control);

            res = send_start_msg(control_app(control), chan, next_argc, next_argv);

            /* Even if res != 0, we still need to free the memory we got from control_argv */
            if (next_argv) {
               for (idx = 0; idx < next_argc; idx++) {
                  ast_free(next_argv[idx]);
               }
               ast_free(next_argv);
            }

            if (res != 0) {
               ast_log(LOG_ERROR,
                  "Error sending start message to '%s'\n", stasis_app_name(control_app(control)));
               remove_masquerade_store(chan);
               control_mark_done(control);
               ao2_ref(next_app, -1);
               break;
            }

            /* Done switching applications, free memory and clean up */
            control_move_cleanup(control);
         } else {
            /* If we can't switch applications, do nothing */
            struct ast_json *msg;
            RAII_VAR(struct ast_channel_snapshot *, snapshot, NULL, ao2_cleanup);

            if (!next_app) {
               ast_log(LOG_ERROR, "Could not move to Stasis app '%s' - not registered\n",
                  control_next_app(control));
            } else {
               ast_log(LOG_ERROR, "Could not move to Stasis app '%s' - not active\n",
                  control_next_app(control));
            }

            snapshot = ast_channel_snapshot_get_latest(ast_channel_uniqueid(chan));
            if (!snapshot) {
               ast_log(LOG_ERROR, "Could not get channel shapshot for '%s'\n",
                  ast_channel_name(chan));
            } else {
               struct ast_json *json_args;
               int next_argc = control_next_app_args_size(control);
               char **next_argv = control_next_app_args(control);

               msg = ast_json_pack("{s: s, s: o, s: o, s: s, s: []}",
                  "type", "ApplicationMoveFailed",
                  "timestamp", ast_json_timeval(ast_tvnow(), NULL),
                  "channel", ast_channel_snapshot_to_json(snapshot, NULL),
                  "destination", control_next_app(control),
                  "args");
               if (!msg) {
                  ast_log(LOG_ERROR, "Failed to pack JSON for ApplicationMoveFailed message\n");
               } else {
                  json_args = ast_json_object_get(msg, "args");
                  if (!json_args) {
                     ast_log(LOG_ERROR, "Could not get args json array");
                  } else {
                     int r = 0;
                     int idx;
                     for (idx = 0; idx < next_argc; ++idx) {
                        r = ast_json_array_append(json_args,
                           ast_json_string_create(next_argv[idx]));
                        if (r != 0) {
                           ast_log(LOG_ERROR, "Error appending to ApplicationMoveFailed message\n");
                           break;
                        }
                     }
                     if (r == 0) {
                        app_send(control_app(control), msg);
                     }
                  }
                  ast_json_unref(msg);
               }
            }
         }
         control_move_cleanup(control);
         ao2_cleanup(next_app);
      }

      last_bridge = bridge;
      bridge = ao2_bump(stasis_app_get_bridge(control));

      if (bridge != last_bridge) {
         if (last_bridge) {
            app_unsubscribe_bridge(control_app(control), last_bridge);
         }
         if (bridge) {
            app_subscribe_bridge(control_app(control), bridge);
         }
      }

      if (bridge) {
         /* Bridge/dial is handling channel frames */
         control_wait(control);
         control_dispatch_all(control, chan);
         continue;
      }

      r = ast_waitfor(chan, MAX_WAIT_MS);

      if (r < 0) {
         ast_debug(3, "%s: Poll error\n",
              ast_channel_uniqueid(chan));
         control_mark_done(control);
         break;
      }

      command_count = control_dispatch_all(control, chan);

      if (command_count > 0 && ast_channel_fdno(chan) == -1) {
         /* Command drained the channel; wait for next frame */
         continue;
      }

      if (r == 0) {
         /* Timeout */
         continue;
      }

      f = ast_read(chan);
      if (!f) {
         /* Continue on in the dialplan */
         ast_debug(3, "%s: Hangup (no more frames)\n",
            ast_channel_uniqueid(chan));
         control_mark_done(control);
         break;
      }

      if (f->frametype == AST_FRAME_CONTROL) {
         if (f->subclass.integer == AST_CONTROL_HANGUP) {
            /* Continue on in the dialplan */
            ast_debug(3, "%s: Hangup\n",
               ast_channel_uniqueid(chan));
            control_mark_done(control);
            break;
         }
      }
   }

   ast_channel_lock(chan);
   needs_depart = (ast_channel_internal_bridge_channel(chan) != NULL);
   ast_channel_unlock(chan);
   if (needs_depart) {
      ast_bridge_depart(chan);
   }

   if (stasis_app_get_bridge(control)) {
      app_unsubscribe_bridge(control_app(control), stasis_app_get_bridge(control));
   }
   ao2_cleanup(bridge);

   /* Only publish a stasis_end event if it hasn't already been published */
   if (!res && !stasis_app_channel_is_stasis_end_published(chan)) {
      /* A masquerade has occurred and this message will be wrong so it
       * has already been sent elsewhere. */
      res = has_masquerade_store(chan) && app_send_end_msg(control_app(control), chan);
      if (res != 0) {
         ast_log(LOG_ERROR,
            "Error sending end message to %s\n", stasis_app_name(control_app(control)));
         return res;
      }
   } else {
      remove_stasis_end_published(chan);
   }

   control_flush_queue(control);

   /* Stop any lingering silence generator */
   control_silence_stop_now(control);

   /* There's an off chance that app is ready for cleanup. Go ahead
    * and clean up, just in case
    */
   cleanup();

   /* The control needs to be removed from the controls container in
    * case a new PBX is started and ends up coming back into Stasis.
    */
   control_unlink(control);
   control = NULL;

   if (!res && !ast_channel_pbx(chan)) {
      int chan_hungup;

      /* The ASYNCGOTO softhangup flag may have broken the channel out of
       * its bridge to run dialplan, so if there's no pbx on the channel
       * let it run dialplan here. Otherwise, it will run when this
       * application exits. */
      ast_channel_lock(chan);
      ast_channel_clear_softhangup(chan, AST_SOFTHANGUP_ASYNCGOTO);
      chan_hungup = ast_check_hangup(chan);
      ast_channel_unlock(chan);

      if (!chan_hungup) {
         struct ast_pbx_args pbx_args;

         memset(&pbx_args, 0, sizeof(pbx_args));
         pbx_args.no_hangup_chan = 1;

         res = ast_pbx_run_args(chan, &pbx_args);
      }
   }

   return res;
}

int stasis_app_send(const char *app_name, struct ast_json *message)
{
   struct stasis_app *app;

   if (!apps_registry) {
      return -1;
   }

   app = ao2_find(apps_registry, app_name, OBJ_SEARCH_KEY);
   if (!app) {
      /* XXX We can do a better job handling late binding, queueing up
       * the call for a few seconds to wait for the app to register.
       */
      ast_log(LOG_WARNING,
         "Stasis app '%s' not registered\n", app_name);
      return -1;
   }
   app_send(app, message);
   ao2_ref(app, -1);

   return 0;
}

static struct stasis_app *find_app_by_name(const char *app_name)
{
   struct stasis_app *res = NULL;

   if (!apps_registry) {
      return NULL;
   }

   if (!ast_strlen_zero(app_name)) {
      res = ao2_find(apps_registry, app_name, OBJ_SEARCH_KEY);
   }

   return res;
}

struct stasis_app *stasis_app_get_by_name(const char *name)
{
   return find_app_by_name(name);
}

static int append_name(void *obj, void *arg, int flags)
{
   struct stasis_app *app = obj;
   struct ao2_container *apps = arg;

   ast_str_container_add(apps, stasis_app_name(app));
   return 0;
}

struct ao2_container *stasis_app_get_all(void)
{
   struct ao2_container *apps;

   if (!apps_registry) {
      return NULL;
   }

   apps = ast_str_container_alloc(1);
   if (!apps) {
      return NULL;
   }

   ao2_callback(apps_registry, OBJ_NODATA, append_name, apps);

   return apps;
}

static int __stasis_app_register(const char *app_name, stasis_app_cb handler, void *data, int all_events)
{
   RAII_VAR(struct stasis_app *, app, NULL, ao2_cleanup);

   if (!apps_registry) {
      return -1;
   }

   ao2_lock(apps_registry);
   app = ao2_find(apps_registry, app_name, OBJ_SEARCH_KEY | OBJ_NOLOCK);
   if (app) {
      /*
       * We need to unlock the apps_registry before calling app_update to
       * prevent the possibility of a deadlock with the session.
       */
      ao2_unlock(apps_registry);
      app_update(app, handler, data);
      cleanup();
      return 0;
   }

   app = app_create(app_name, handler, data, all_events ? STASIS_APP_SUBSCRIBE_ALL : STASIS_APP_SUBSCRIBE_MANUAL);
   if (!app) {
      ao2_unlock(apps_registry);
      return -1;
   }

   if (all_events) {
      struct stasis_app_event_source *source;

      AST_RWLIST_RDLOCK(&event_sources);
      AST_LIST_TRAVERSE(&event_sources, source, next) {
         if (!source->subscribe) {
            continue;
         }

         source->subscribe(app, NULL);
      }
      AST_RWLIST_UNLOCK(&event_sources);
   }
   ao2_link_flags(apps_registry, app, OBJ_NOLOCK);

   ao2_unlock(apps_registry);

   /* We lazily clean up the apps_registry, because it's good enough to
    * prevent memory leaks, and we're lazy.
    */
   cleanup();
   return 0;
}

int stasis_app_register(const char *app_name, stasis_app_cb handler, void *data)
{
   return __stasis_app_register(app_name, handler, data, 0);
}

int stasis_app_register_all(const char *app_name, stasis_app_cb handler, void *data)
{
   return __stasis_app_register(app_name, handler, data, 1);
}

void stasis_app_unregister(const char *app_name)
{
   struct stasis_app *app;

   if (!app_name) {
      return;
   }

   if (!apps_registry) {
      return;
   }

   app = ao2_find(apps_registry, app_name, OBJ_SEARCH_KEY);
   if (!app) {
      ast_log(LOG_ERROR,
         "Stasis app '%s' not registered\n", app_name);
      return;
   }

   app_deactivate(app);

   /* There's a decent chance that app is ready for cleanup. Go ahead
    * and clean up, just in case
    */
   cleanup();

   ao2_ref(app, -1);
}

void stasis_app_register_event_source(struct stasis_app_event_source *obj)
{
   AST_RWLIST_WRLOCK(&event_sources);
   AST_LIST_INSERT_TAIL(&event_sources, obj, next);
   AST_RWLIST_UNLOCK(&event_sources);
}

void stasis_app_unregister_event_source(struct stasis_app_event_source *obj)
{
   struct stasis_app_event_source *source;

   AST_RWLIST_WRLOCK(&event_sources);
   AST_RWLIST_TRAVERSE_SAFE_BEGIN(&event_sources, source, next) {
      if (source == obj) {
         AST_RWLIST_REMOVE_CURRENT(next);
         break;
      }
   }
   AST_RWLIST_TRAVERSE_SAFE_END;
   AST_RWLIST_UNLOCK(&event_sources);
}

/*!
 * \internal
 * \brief Convert event source data to JSON.
 *
 * Calls each event source that has a "to_json" handler allowing each
 * source to add data to the given JSON object.
 *
 * \param app application associated with the event source
 * \param json a json object to "fill"
 *
 * \retval The given json object.
 */
static struct ast_json *app_event_sources_to_json(
   const struct stasis_app *app, struct ast_json *json)
{
   struct stasis_app_event_source *source;

   AST_RWLIST_RDLOCK(&event_sources);
   AST_LIST_TRAVERSE(&event_sources, source, next) {
      if (source->to_json) {
         source->to_json(app, json);
      }
   }
   AST_RWLIST_UNLOCK(&event_sources);

   return json;
}

struct ast_json *stasis_app_object_to_json(struct stasis_app *app)
{
   if (!app) {
      return NULL;
   }

   return stasis_app_event_filter_to_json(
      app, app_event_sources_to_json(app, app_to_json(app)));
}

struct ast_json *stasis_app_to_json(const char *app_name)
{
   struct stasis_app *app = find_app_by_name(app_name);
   struct ast_json *json = stasis_app_object_to_json(app);

   ao2_cleanup(app);

   return json;
}

/*!
 * \internal
 * \brief Finds an event source that matches a uri scheme.
 *
 * Uri(s) should begin with a particular scheme that can be matched
 * against an event source.
 *
 * \param uri uri containing a scheme to match
 *
 * \retval an event source if found, NULL otherwise.
 */
static struct stasis_app_event_source *app_event_source_find(const char *uri)
{
   struct stasis_app_event_source *source;

   AST_RWLIST_RDLOCK(&event_sources);
   AST_LIST_TRAVERSE(&event_sources, source, next) {
      if (ast_begins_with(uri, source->scheme)) {
         break;
      }
   }
   AST_RWLIST_UNLOCK(&event_sources);

   return source;
}

/*!
 * \internal
 * \brief Callback for subscription handling
 *
 * \param app [un]subscribing application
 * \param uri scheme:id of an event source
 * \param event_source being [un]subscribed [from]to
 *
 * \retval stasis_app_subscribe_res return code.
 */
typedef enum stasis_app_subscribe_res (*app_subscription_handler)(
   struct stasis_app *app, const char *uri,
   struct stasis_app_event_source *event_source);

/*!
 * \internal
 * \brief Subscriptions handler for application [un]subscribing.
 *
 * \param app_name Name of the application to subscribe.
 * \param event_source_uris URIs for the event sources to subscribe to.
 * \param event_sources_count Array size of event_source_uris.
 * \param json Optional output pointer for JSON representation of the app
 *             after adding the subscription.
 * \param handler [un]subscribe handler
 *
 * \retval stasis_app_subscribe_res return code.
 */
static enum stasis_app_subscribe_res app_handle_subscriptions(
   const char *app_name, const char **event_source_uris,
   int event_sources_count, struct ast_json **json,
   app_subscription_handler handler)
{
   struct stasis_app *app = find_app_by_name(app_name);
   int i;

   ast_assert(handler != NULL);

   if (!app) {
      return STASIS_ASR_APP_NOT_FOUND;
   }

   for (i = 0; i < event_sources_count; ++i) {
      const char *uri = event_source_uris[i];
      struct stasis_app_event_source *event_source;
      enum stasis_app_subscribe_res res;

      event_source = app_event_source_find(uri);
      if (!event_source) {
         ast_log(LOG_WARNING, "Invalid scheme: %s\n", uri);
         ao2_ref(app, -1);

         return STASIS_ASR_EVENT_SOURCE_BAD_SCHEME;
      }

      res = handler(app, uri, event_source);
      if (res != STASIS_ASR_OK) {
         ao2_ref(app, -1);

         return res;
      }
   }

   if (json) {
      ast_debug(3, "%s: Successful; setting results\n", app_name);
      *json = stasis_app_object_to_json(app);
   }

   ao2_ref(app, -1);

   return STASIS_ASR_OK;
}

enum stasis_app_subscribe_res stasis_app_subscribe_channel(const char *app_name,
   struct ast_channel *chan)
{
   struct stasis_app *app = find_app_by_name(app_name);
   int res;

   if (!app) {
      return STASIS_ASR_APP_NOT_FOUND;
   }

   ast_debug(3, "%s: Subscribing to %s\n", app_name, ast_channel_uniqueid(chan));

   res = app_subscribe_channel(app, chan);
   ao2_ref(app, -1);

   if (res != 0) {
      ast_log(LOG_ERROR, "Error subscribing app '%s' to channel '%s'\n",
         app_name, ast_channel_uniqueid(chan));
      return STASIS_ASR_INTERNAL_ERROR;
   }

   return STASIS_ASR_OK;
}


/*!
 * \internal
 * \brief Subscribe an app to an event source.
 *
 * \param app subscribing application
 * \param uri scheme:id of an event source
 * \param event_source being subscribed to
 *
 * \retval stasis_app_subscribe_res return code.
 */
static enum stasis_app_subscribe_res app_subscribe(
   struct stasis_app *app, const char *uri,
   struct stasis_app_event_source *event_source)
{
   const char *app_name = stasis_app_name(app);
   RAII_VAR(void *, obj, NULL, ao2_cleanup);

   ast_debug(3, "%s: Checking %s\n", app_name, uri);

   if (!ast_strlen_zero(uri + strlen(event_source->scheme)) &&
       (!event_source->find || (!(obj = event_source->find(app, uri + strlen(event_source->scheme)))))) {
      ast_log(LOG_WARNING, "Event source not found: %s\n", uri);
      return STASIS_ASR_EVENT_SOURCE_NOT_FOUND;
   }

   ast_debug(3, "%s: Subscribing to %s\n", app_name, uri);

   if (!event_source->subscribe || (event_source->subscribe(app, obj))) {
      ast_log(LOG_WARNING, "Error subscribing app '%s' to '%s'\n",
         app_name, uri);
      return STASIS_ASR_INTERNAL_ERROR;
   }

   return STASIS_ASR_OK;
}

enum stasis_app_subscribe_res stasis_app_subscribe(const char *app_name,
   const char **event_source_uris, int event_sources_count,
   struct ast_json **json)
{
   return app_handle_subscriptions(
      app_name, event_source_uris, event_sources_count,
      json, app_subscribe);
}

/*!
 * \internal
 * \brief Unsubscribe an app from an event source.
 *
 * \param app application to unsubscribe
 * \param uri scheme:id of an event source
 * \param event_source being unsubscribed from
 *
 * \retval stasis_app_subscribe_res return code.
 */
static enum stasis_app_subscribe_res app_unsubscribe(
   struct stasis_app *app, const char *uri,
   struct stasis_app_event_source *event_source)
{
   const char *app_name = stasis_app_name(app);
   const char *id = uri + strlen(event_source->scheme);

   if (!event_source->is_subscribed ||
       (!event_source->is_subscribed(app, id))) {
      return STASIS_ASR_EVENT_SOURCE_NOT_FOUND;
   }

   ast_debug(3, "%s: Unsubscribing from %s\n", app_name, uri);

   if (!event_source->unsubscribe || (event_source->unsubscribe(app, id))) {
      ast_log(LOG_WARNING, "Error unsubscribing app '%s' to '%s'\n",
         app_name, uri);
      return -1;
   }
   return 0;
}

enum stasis_app_subscribe_res stasis_app_unsubscribe(const char *app_name,
   const char **event_source_uris, int event_sources_count,
   struct ast_json **json)
{
   return app_handle_subscriptions(
      app_name, event_source_uris, event_sources_count,
      json, app_unsubscribe);
}

enum stasis_app_user_event_res stasis_app_user_event(const char *app_name,
   const char *event_name,
   const char **source_uris, int sources_count,
   struct ast_json *json_variables)
{
   RAII_VAR(struct stasis_app *, app, find_app_by_name(app_name), ao2_cleanup);
   struct ast_json *blob = NULL;
   struct ast_multi_object_blob *multi;
   struct stasis_message *message;
   enum stasis_app_user_event_res res = STASIS_APP_USER_INTERNAL_ERROR;
   int have_channel = 0;
   int i;

   if (!app) {
      ast_log(LOG_WARNING, "App %s not found\n", app_name);
      return STASIS_APP_USER_APP_NOT_FOUND;
   }

   if (!ast_multi_user_event_type()) {
      return res;
   }

   if (json_variables) {
      struct ast_json *json_value = ast_json_string_create(event_name);

      if (json_value && !ast_json_object_set(json_variables, "eventname", json_value)) {
         blob = ast_json_ref(json_variables);
      }
   } else {
      blob = ast_json_pack("{s: s}", "eventname", event_name);
   }

   if (!blob) {
      ast_log(LOG_ERROR, "Failed to initialize blob\n");

      return res;
   }

   multi = ast_multi_object_blob_create(blob);
   ast_json_unref(blob);
   if (!multi) {
      ast_log(LOG_ERROR, "Failed to initialize multi\n");

      return res;
   }

   for (i = 0; i < sources_count; ++i) {
      const char *uri = source_uris[i];
      void *snapshot=NULL;
      enum stasis_user_multi_object_snapshot_type type;

      if (ast_begins_with(uri, "channel:")) {
         type = STASIS_UMOS_CHANNEL;
         snapshot = ast_channel_snapshot_get_latest(uri + 8);
         have_channel = 1;
      } else if (ast_begins_with(uri, "bridge:")) {
         type = STASIS_UMOS_BRIDGE;
         snapshot = ast_bridge_get_snapshot_by_uniqueid(uri + 7);
      } else if (ast_begins_with(uri, "endpoint:")) {
         type = STASIS_UMOS_ENDPOINT;
         snapshot = ast_endpoint_latest_snapshot(uri + 9, NULL);
      } else {
         ast_log(LOG_WARNING, "Invalid scheme: %s\n", uri);
         ao2_ref(multi, -1);

         return STASIS_APP_USER_EVENT_SOURCE_BAD_SCHEME;
      }
      if (!snapshot) {
         ast_log(LOG_ERROR, "Unable to get snapshot for %s\n", uri);
         ao2_ref(multi, -1);

         return STASIS_APP_USER_EVENT_SOURCE_NOT_FOUND;
      }
      ast_multi_object_blob_add(multi, type, snapshot);
   }

   message = stasis_message_create(ast_multi_user_event_type(), multi);
   ao2_ref(multi, -1);

   if (!message) {
      ast_log(LOG_ERROR, "Unable to create stasis user event message\n");
      return res;
   }

   /*
    * Publishing to two different topics is normally to be avoided -- except
    * in this case both are final destinations with no forwards (only listeners).
    * The message has to be delivered to the application topic for ARI, but a
    * copy is also delivered directly to the manager for AMI if there is a channel.
    */
   stasis_publish(ast_app_get_topic(app), message);

   if (have_channel) {
      stasis_publish(ast_manager_get_topic(), message);
   }
   ao2_ref(message, -1);

   return STASIS_APP_USER_OK;
}

static int unload_module(void)
{
   stasis_app_unregister_event_sources();

   messaging_cleanup();

   cleanup();

   stasis_app_control_shutdown();

   ao2_cleanup(apps_registry);
   apps_registry = NULL;

   ao2_cleanup(app_controls);
   app_controls = NULL;

   ao2_cleanup(app_bridges);
   app_bridges = NULL;

   ao2_cleanup(app_bridges_moh);
   app_bridges_moh = NULL;

   ao2_cleanup(app_bridges_playback);
   app_bridges_playback = NULL;

   STASIS_MESSAGE_TYPE_CLEANUP(end_message_type);
   STASIS_MESSAGE_TYPE_CLEANUP(start_message_type);

   return 0;
}

/* \brief Sanitization callback for channel snapshots */
static int channel_snapshot_sanitizer(const struct ast_channel_snapshot *snapshot)
{
   if (!snapshot || !(snapshot->base->tech_properties & AST_CHAN_TP_INTERNAL)) {
      return 0;
   }
   return 1;
}

/* \brief Sanitization callback for channels */
static int channel_sanitizer(const struct ast_channel *chan)
{
   if (!chan || !(ast_channel_tech(chan)->properties & AST_CHAN_TP_INTERNAL)) {
      return 0;
   }
   return 1;
}

/* \brief Sanitization callback for channel unique IDs */
static int channel_id_sanitizer(const char *id)
{
   struct ast_channel_snapshot *snapshot;
   int ret;

   snapshot = ast_channel_snapshot_get_latest(id);
   ret = channel_snapshot_sanitizer(snapshot);
   ao2_cleanup(snapshot);

   return ret;
}

/* \brief Sanitization callbacks for communication to Stasis applications */
struct stasis_message_sanitizer app_sanitizer = {
   .channel_id = channel_id_sanitizer,
   .channel_snapshot = channel_snapshot_sanitizer,
   .channel = channel_sanitizer,
};

struct stasis_message_sanitizer *stasis_app_get_sanitizer(void)
{
   return &app_sanitizer;
}

static const struct ast_datastore_info stasis_internal_channel_info = {
   .type = "stasis-internal-channel",
};

static int set_internal_datastore(struct ast_channel *chan)
{
   struct ast_datastore *datastore;

   datastore = ast_channel_datastore_find(chan, &stasis_internal_channel_info, NULL);
   if (!datastore) {
      datastore = ast_datastore_alloc(&stasis_internal_channel_info, NULL);
      if (!datastore) {
         return -1;
      }
      ast_channel_datastore_add(chan, datastore);
   }
   return 0;
}

int stasis_app_channel_unreal_set_internal(struct ast_channel *chan)
{
   struct ast_channel *outchan = NULL, *outowner = NULL;
   int res = 0;
   struct ast_unreal_pvt *unreal_pvt = ast_channel_tech_pvt(chan);

   ao2_ref(unreal_pvt, +1);
   ast_unreal_lock_all(unreal_pvt, &outowner, &outchan);
   if (outowner) {
      res |= set_internal_datastore(outowner);
      ast_channel_unlock(outowner);
      ast_channel_unref(outowner);
   }
   if (outchan) {
      res |= set_internal_datastore(outchan);
      ast_channel_unlock(outchan);
      ast_channel_unref(outchan);
   }
   ao2_unlock(unreal_pvt);
   ao2_ref(unreal_pvt, -1);
   return res;
}

int stasis_app_channel_set_internal(struct ast_channel *chan)
{
   int res;

   ast_channel_lock(chan);
   res = set_internal_datastore(chan);
   ast_channel_unlock(chan);

   return res;
}

int stasis_app_channel_is_internal(struct ast_channel *chan)
{
   struct ast_datastore *datastore;
   int res = 0;

   ast_channel_lock(chan);
   datastore = ast_channel_datastore_find(chan, &stasis_internal_channel_info, NULL);
   if (datastore) {
      res = 1;
   }
   ast_channel_unlock(chan);

   return res;
}

static int load_module(void)
{
   if (STASIS_MESSAGE_TYPE_INIT(start_message_type) != 0) {
      return AST_MODULE_LOAD_DECLINE;
   }
   if (STASIS_MESSAGE_TYPE_INIT(end_message_type) != 0) {
      return AST_MODULE_LOAD_DECLINE;
   }
   apps_registry = ao2_container_alloc_hash(AO2_ALLOC_OPT_LOCK_MUTEX, 0,
      APPS_NUM_BUCKETS, app_hash, NULL, app_compare);
   app_controls = ao2_container_alloc_hash(AO2_ALLOC_OPT_LOCK_MUTEX, 0,
      CONTROLS_NUM_BUCKETS, control_hash, NULL, control_compare);
   app_bridges = ao2_container_alloc_hash(AO2_ALLOC_OPT_LOCK_MUTEX, 0,
      BRIDGES_NUM_BUCKETS, bridges_hash, NULL, bridges_compare);
   app_bridges_moh = ao2_container_alloc_hash(
      AO2_ALLOC_OPT_LOCK_MUTEX, 0,
      37, bridges_channel_hash_fn, NULL, bridges_channel_compare);
   app_bridges_playback = ao2_container_alloc_hash(
      AO2_ALLOC_OPT_LOCK_MUTEX, AO2_CONTAINER_ALLOC_OPT_DUPS_REJECT,
      37, bridges_channel_hash_fn, bridges_channel_sort_fn, NULL);
   if (!apps_registry || !app_controls || !app_bridges || !app_bridges_moh || !app_bridges_playback) {
      unload_module();
      return AST_MODULE_LOAD_DECLINE;
   }

   if (messaging_init()) {
      unload_module();
      return AST_MODULE_LOAD_DECLINE;
   }

   bridge_stasis_init();

   stasis_app_register_event_sources();

   return AST_MODULE_LOAD_SUCCESS;
}

AST_MODULE_INFO(ASTERISK_GPL_KEY, AST_MODFLAG_GLOBAL_SYMBOLS | AST_MODFLAG_LOAD_ORDER, "Stasis application support",
   .load_pri = AST_MODPRI_APP_DEPEND - 1,
   .support_level = AST_MODULE_SUPPORT_CORE,
   .load = load_module,
   .unload = unload_module,
);