control.c

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/*
 * Asterisk -- An open source telephony toolkit.
 *
 * Copyright (C) 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 control support.
 *
 * \author David M. Lee, II <[email protected]>
 */

#include "asterisk.h"

#include "asterisk/stasis_channels.h"
#include "asterisk/stasis_app.h"

#include "command.h"
#include "control.h"
#include "app.h"
#include "asterisk/dial.h"
#include "asterisk/bridge.h"
#include "asterisk/bridge_after.h"
#include "asterisk/bridge_basic.h"
#include "asterisk/bridge_features.h"
#include "asterisk/frame.h"
#include "asterisk/pbx.h"
#include "asterisk/musiconhold.h"
#include "asterisk/app.h"

AST_LIST_HEAD(app_control_rules, stasis_app_control_rule);

/*!
 * \brief Indicates if the Stasis app internals are being shut down
 */
static int shutting_down;

struct stasis_app_control {
   ast_cond_t wait_cond;
   /*! Queue of commands to dispatch on the channel */
   struct ao2_container *command_queue;
   /*!
    * The associated channel.
    * Be very careful with the threading associated w/ manipulating
    * the channel.
    */
   struct ast_channel *channel;
   /*!
    * When a channel is in a bridge, the bridge that it is in.
    */
   struct ast_bridge *bridge;
   /*!
    * Bridge features which should be applied to the channel when it enters the next bridge.  These only apply to the next bridge and will be emptied thereafter.
    */
   struct ast_bridge_features *bridge_features;
   /*!
    * Holding place for channel's PBX while imparted to a bridge.
    */
   struct ast_pbx *pbx;
   /*!
    * A list of rules to check before adding a channel to a bridge.
    */
   struct app_control_rules add_rules;
   /*!
    * A list of rules to check before removing a channel from a bridge.
    */
   struct app_control_rules remove_rules;
   /*!
    * Silence generator, when silence is being generated.
    */
   struct ast_silence_generator *silgen;
   /*!
    * The app for which this control is currently controlling.
    * This can change through the use of the /channels/{channelId}/move
    * command.
    */
   struct stasis_app *app;
   /*!
    * The name of the next Stasis application to move to.
    */
   char *next_app;
   /*!
    * The list of arguments to pass to StasisStart when moving to another app.
    */
   AST_VECTOR(, char *) next_app_args;
   /*!
    * When set, /c app_stasis should exit and continue in the dialplan.
    */
   unsigned int is_done:1;
};

static void control_dtor(void *obj)
{
   struct stasis_app_control *control = obj;

   ao2_cleanup(control->command_queue);

   ast_channel_cleanup(control->channel);
   ao2_cleanup(control->app);

   control_move_cleanup(control);

   ast_cond_destroy(&control->wait_cond);
   AST_LIST_HEAD_DESTROY(&control->add_rules);
   AST_LIST_HEAD_DESTROY(&control->remove_rules);
   ast_bridge_features_destroy(control->bridge_features);

}

struct stasis_app_control *control_create(struct ast_channel *channel, struct stasis_app *app)
{
   struct stasis_app_control *control;
   int res;

   control = ao2_alloc(sizeof(*control), control_dtor);
   if (!control) {
      return NULL;
   }

   AST_LIST_HEAD_INIT(&control->add_rules);
   AST_LIST_HEAD_INIT(&control->remove_rules);

   res = ast_cond_init(&control->wait_cond, NULL);
   if (res != 0) {
      ast_log(LOG_ERROR, "Error initializing ast_cond_t: %s\n",
         strerror(errno));
      ao2_ref(control, -1);
      return NULL;
   }

   control->app = ao2_bump(app);

   ast_channel_ref(channel);
   control->channel = channel;

   control->command_queue = ao2_container_alloc_list(
      AO2_ALLOC_OPT_LOCK_MUTEX, 0, NULL, NULL);
   if (!control->command_queue) {
      ao2_ref(control, -1);
      return NULL;
   }

   control->next_app = NULL;
   AST_VECTOR_INIT(&control->next_app_args, 0);

   return control;
}

static void app_control_register_rule(
   struct stasis_app_control *control,
   struct app_control_rules *list, struct stasis_app_control_rule *obj)
{
   ao2_lock(control->command_queue);
   AST_LIST_INSERT_TAIL(list, obj, next);
   ao2_unlock(control->command_queue);
}

static void app_control_unregister_rule(
   struct stasis_app_control *control,
   struct app_control_rules *list, struct stasis_app_control_rule *obj)
{
   struct stasis_app_control_rule *rule;

   ao2_lock(control->command_queue);
   AST_RWLIST_TRAVERSE_SAFE_BEGIN(list, rule, next) {
      if (rule == obj) {
         AST_RWLIST_REMOVE_CURRENT(next);
         break;
      }
   }
   AST_RWLIST_TRAVERSE_SAFE_END;
   ao2_unlock(control->command_queue);
}

/*!
 * \internal
 * \brief Checks to make sure each rule in the given list passes.
 *
 * \details Loops over a list of rules checking for rejections or failures.
 *          If one rule fails its resulting error code is returned.
 *
 * \note Command queue should be locked before calling this function.
 *
 * \param control The stasis application control
 * \param list The list of rules to check
 *
 * \retval 0 if all rules pass
 * \retval non-zero error code if a rule fails
 */
static enum stasis_app_control_channel_result app_control_check_rules(
   const struct stasis_app_control *control,
   struct app_control_rules *list)
{
   int res = 0;
   struct stasis_app_control_rule *rule;
   AST_LIST_TRAVERSE(list, rule, next) {
      if ((res = rule->check_rule(control))) {
         return res;
      }
   }
   return res;
}

void stasis_app_control_register_add_rule(
   struct stasis_app_control *control,
   struct stasis_app_control_rule *rule)
{
   return app_control_register_rule(control, &control->add_rules, rule);
}

void stasis_app_control_unregister_add_rule(
   struct stasis_app_control *control,
   struct stasis_app_control_rule *rule)
{
   app_control_unregister_rule(control, &control->add_rules, rule);
}

void stasis_app_control_register_remove_rule(
   struct stasis_app_control *control,
   struct stasis_app_control_rule *rule)
{
   return app_control_register_rule(control, &control->remove_rules, rule);
}

void stasis_app_control_unregister_remove_rule(
   struct stasis_app_control *control,
   struct stasis_app_control_rule *rule)
{
   app_control_unregister_rule(control, &control->remove_rules, rule);
}

static int app_control_can_add_channel_to_bridge(
   struct stasis_app_control *control)
{
   return app_control_check_rules(control, &control->add_rules);
}

static int app_control_can_remove_channel_from_bridge(
   struct stasis_app_control *control)
{
   return app_control_check_rules(control, &control->remove_rules);
}

static int noop_cb(struct stasis_app_control *control,
   struct ast_channel *chan, void *data)
{
   return 0;
}

/*! Callback type to see if the command can execute
    note: command_queue is locked during callback */
typedef int (*app_command_can_exec_cb)(struct stasis_app_control *control);

static struct stasis_app_command *exec_command_on_condition(
   struct stasis_app_control *control, stasis_app_command_cb command_fn,
   void *data, command_data_destructor_fn data_destructor,
   app_command_can_exec_cb can_exec_fn)
{
   int retval;
   struct stasis_app_command *command;

   command_fn = command_fn ? : noop_cb;

   command = command_create(command_fn, data, data_destructor);
   if (!command) {
      return NULL;
   }

   ao2_lock(control->command_queue);
   if (control->is_done) {
      ao2_unlock(control->command_queue);
      ao2_ref(command, -1);
      return NULL;
   }
   if (can_exec_fn && (retval = can_exec_fn(control))) {
      ao2_unlock(control->command_queue);
      command_complete(command, retval);
      return command;
   }

   ao2_link_flags(control->command_queue, command, OBJ_NOLOCK);
   ast_cond_signal(&control->wait_cond);
   ao2_unlock(control->command_queue);

   return command;
}

static struct stasis_app_command *exec_command(
   struct stasis_app_control *control, stasis_app_command_cb command_fn,
   void *data, command_data_destructor_fn data_destructor)
{
   return exec_command_on_condition(control, command_fn, data, data_destructor, NULL);
}

static int app_control_add_role(struct stasis_app_control *control,
      struct ast_channel *chan, void *data)
{
   char *role = data;

   return ast_channel_add_bridge_role(chan, role);
}

int stasis_app_control_add_role(struct stasis_app_control *control, const char *role)
{
   char *role_dup;

   role_dup = ast_strdup(role);
   if (!role_dup) {
      return -1;
   }

   stasis_app_send_command_async(control, app_control_add_role, role_dup, ast_free_ptr);

   return 0;
}

static int app_control_clear_roles(struct stasis_app_control *control,
      struct ast_channel *chan, void *data)
{
   ast_channel_clear_bridge_roles(chan);

   return 0;
}

void stasis_app_control_clear_roles(struct stasis_app_control *control)
{
   stasis_app_send_command_async(control, app_control_clear_roles, NULL, NULL);
}

int control_command_count(struct stasis_app_control *control)
{
   return ao2_container_count(control->command_queue);
}

int control_is_done(struct stasis_app_control *control)
{
   /* Called from stasis_app_exec thread; no lock needed */
   return control->is_done;
}

void control_mark_done(struct stasis_app_control *control)
{
   /* Locking necessary to sync with other threads adding commands to the queue. */
   ao2_lock(control->command_queue);
   control->is_done = 1;
   ao2_unlock(control->command_queue);
}

struct stasis_app_control_continue_data {
   char context[AST_MAX_CONTEXT];
   char extension[AST_MAX_EXTENSION];
   int priority;
};

static int app_control_continue(struct stasis_app_control *control,
   struct ast_channel *chan, void *data)
{
   struct stasis_app_control_continue_data *continue_data = data;

   ast_assert(control->channel != NULL);

   /* If we're in a Stasis bridge, depart it before going back to the
    * dialplan */
   if (stasis_app_get_bridge(control)) {
      ast_bridge_depart(control->channel);
   }

   /* Called from stasis_app_exec thread; no lock needed */
   ast_explicit_goto(control->channel, continue_data->context, continue_data->extension, continue_data->priority);

   control_mark_done(control);

   return 0;
}

int stasis_app_control_continue(struct stasis_app_control *control, const char *context, const char *extension, int priority)
{
   struct stasis_app_control_continue_data *continue_data;

   if (!(continue_data = ast_calloc(1, sizeof(*continue_data)))) {
      return -1;
   }
   ast_copy_string(continue_data->context, S_OR(context, ""), sizeof(continue_data->context));
   ast_copy_string(continue_data->extension, S_OR(extension, ""), sizeof(continue_data->extension));
   if (priority > 0) {
      continue_data->priority = priority;
   } else {
      continue_data->priority = -1;
   }

   stasis_app_send_command_async(control, app_control_continue, continue_data, ast_free_ptr);

   return 0;
}

struct stasis_app_control_move_data {
   char *app_name;
   char *app_args;
};

static int app_control_move(struct stasis_app_control *control,
   struct ast_channel *chan, void *data)
{
   struct stasis_app_control_move_data *move_data = data;

   control->next_app = ast_strdup(move_data->app_name);
   if (!control->next_app) {
      ast_log(LOG_ERROR, "Allocation failed for next app\n");
      return -1;
   }

   if (move_data->app_args) {
      char *token;

      while ((token = strtok_r(move_data->app_args, ",", &move_data->app_args))) {
         int res;
         char *arg;

         if (!(arg = ast_strdup(token))) {
            ast_log(LOG_ERROR, "Allocation failed for next app arg\n");
            control_move_cleanup(control);
            return -1;
         }

         res = AST_VECTOR_APPEND(&control->next_app_args, arg);
         if (res) {
            ast_log(LOG_ERROR, "Failed to append arg to next app args\n");
            ast_free(arg);
            control_move_cleanup(control);
            return -1;
         }
      }
   }

   return 0;
}

int stasis_app_control_move(struct stasis_app_control *control, const char *app_name, const char *app_args)
{
   struct stasis_app_control_move_data *move_data;
   size_t size;

   size = sizeof(*move_data) + strlen(app_name) + 1;
   if (app_args) {
      /* Application arguments are optional */
      size += strlen(app_args) + 1;
   }

   if (!(move_data = ast_calloc(1, size))) {
      return -1;
   }

   move_data->app_name = (char *)move_data + sizeof(*move_data);
   strcpy(move_data->app_name, app_name); /* Safe */

   if (app_args) {
      move_data->app_args = move_data->app_name + strlen(app_name) + 1;
      strcpy(move_data->app_args, app_args); /* Safe */
   } else {
      move_data->app_args = NULL;
   }

   stasis_app_send_command_async(control, app_control_move, move_data, ast_free_ptr);

   return 0;
}

static int app_control_redirect(struct stasis_app_control *control,
   struct ast_channel *chan, void *data)
{
   char *endpoint = data;
   int res;

   ast_assert(control->channel != NULL);
   ast_assert(endpoint != NULL);

   res = ast_transfer(control->channel, endpoint);
   if (!res) {
      ast_log(LOG_NOTICE, "Unsupported transfer requested on channel '%s'\n",
         ast_channel_name(control->channel));
      return 0;
   }

   return 0;
}

int stasis_app_control_redirect(struct stasis_app_control *control, const char *endpoint)
{
   char *endpoint_data = ast_strdup(endpoint);

   if (!endpoint_data) {
      return -1;
   }

   stasis_app_send_command_async(control, app_control_redirect, endpoint_data, ast_free_ptr);

   return 0;
}

struct stasis_app_control_dtmf_data {
   int before;
   int between;
   unsigned int duration;
   int after;
   char dtmf[];
};

static void dtmf_in_bridge(struct ast_channel *chan, struct stasis_app_control_dtmf_data *dtmf_data)
{
   if (dtmf_data->before) {
      usleep(dtmf_data->before * 1000);
   }

   ast_dtmf_stream_external(chan, dtmf_data->dtmf, dtmf_data->between, dtmf_data->duration);

   if (dtmf_data->after) {
      usleep(dtmf_data->after * 1000);
   }
}

static void dtmf_no_bridge(struct ast_channel *chan, struct stasis_app_control_dtmf_data *dtmf_data)
{
   if (dtmf_data->before) {
      ast_safe_sleep(chan, dtmf_data->before);
   }

   ast_dtmf_stream(chan, NULL, dtmf_data->dtmf, dtmf_data->between, dtmf_data->duration);

   if (dtmf_data->after) {
      ast_safe_sleep(chan, dtmf_data->after);
   }
}

static int app_control_dtmf(struct stasis_app_control *control,
   struct ast_channel *chan, void *data)
{
   struct stasis_app_control_dtmf_data *dtmf_data = data;

   if (ast_channel_state(chan) != AST_STATE_UP) {
      ast_indicate(chan, AST_CONTROL_PROGRESS);
   }

   if (stasis_app_get_bridge(control)) {
      dtmf_in_bridge(chan, dtmf_data);
   } else {
      dtmf_no_bridge(chan, dtmf_data);
   }

   return 0;
}

int stasis_app_control_dtmf(struct stasis_app_control *control, const char *dtmf, int before, int between, unsigned int duration, int after)
{
   struct stasis_app_control_dtmf_data *dtmf_data;

   if (!(dtmf_data = ast_calloc(1, sizeof(*dtmf_data) + strlen(dtmf) + 1))) {
      return -1;
   }

   dtmf_data->before = before;
   dtmf_data->between = between;
   dtmf_data->duration = duration;
   dtmf_data->after = after;
   strcpy(dtmf_data->dtmf, dtmf);

   stasis_app_send_command_async(control, app_control_dtmf, dtmf_data, ast_free_ptr);

   return 0;
}

static int app_control_ring(struct stasis_app_control *control,
   struct ast_channel *chan, void *data)
{
   ast_indicate(control->channel, AST_CONTROL_RINGING);

   return 0;
}

int stasis_app_control_ring(struct stasis_app_control *control)
{
   stasis_app_send_command_async(control, app_control_ring, NULL, NULL);

   return 0;
}

static int app_control_ring_stop(struct stasis_app_control *control,
   struct ast_channel *chan, void *data)
{
   ast_indicate(control->channel, -1);

   return 0;
}

int stasis_app_control_ring_stop(struct stasis_app_control *control)
{
   stasis_app_send_command_async(control, app_control_ring_stop, NULL, NULL);

   return 0;
}

struct stasis_app_control_mute_data {
   enum ast_frame_type frametype;
   unsigned int direction;
};

static int app_control_mute(struct stasis_app_control *control,
   struct ast_channel *chan, void *data)
{
   struct stasis_app_control_mute_data *mute_data = data;

   ast_channel_lock(chan);
   ast_channel_suppress(control->channel, mute_data->direction, mute_data->frametype);
   ast_channel_unlock(chan);

   return 0;
}

int stasis_app_control_mute(struct stasis_app_control *control, unsigned int direction, enum ast_frame_type frametype)
{
   struct stasis_app_control_mute_data *mute_data;

   if (!(mute_data = ast_calloc(1, sizeof(*mute_data)))) {
      return -1;
   }

   mute_data->direction = direction;
   mute_data->frametype = frametype;

   stasis_app_send_command_async(control, app_control_mute, mute_data, ast_free_ptr);

   return 0;
}

static int app_control_unmute(struct stasis_app_control *control,
   struct ast_channel *chan, void *data)
{
   struct stasis_app_control_mute_data *mute_data = data;

   ast_channel_lock(chan);
   ast_channel_unsuppress(control->channel, mute_data->direction, mute_data->frametype);
   ast_channel_unlock(chan);

   return 0;
}

int stasis_app_control_unmute(struct stasis_app_control *control, unsigned int direction, enum ast_frame_type frametype)
{
   struct stasis_app_control_mute_data *mute_data;

   if (!(mute_data = ast_calloc(1, sizeof(*mute_data)))) {
      return -1;
   }

   mute_data->direction = direction;
   mute_data->frametype = frametype;

   stasis_app_send_command_async(control, app_control_unmute, mute_data, ast_free_ptr);

   return 0;
}

/*!
 * \brief structure for queuing ARI channel variable setting
 *
 * It may seem weird to define this custom structure given that we already have
 * ast_var_t and ast_variable defined elsewhere. The problem with those is that
 * they are not tolerant of NULL channel variable value pointers. In fact, in both
 * cases, the best they could do is to have a zero-length variable value. However,
 * when un-setting a channel variable, it is important to pass a NULL value, not
 * a zero-length string.
 */
struct chanvar {
   /*! Name of variable to set/unset */
   char *name;
   /*! Value of variable to set. If unsetting, this will be NULL */
   char *value;
};

static void free_chanvar(void *data)
{
   struct chanvar *var = data;

   ast_free(var->name);
   ast_free(var->value);
   ast_free(var);
}

static int app_control_set_channel_var(struct stasis_app_control *control,
   struct ast_channel *chan, void *data)
{
   struct chanvar *var = data;

   pbx_builtin_setvar_helper(control->channel, var->name, var->value);

   return 0;
}

int stasis_app_control_set_channel_var(struct stasis_app_control *control, const char *variable, const char *value)
{
   struct chanvar *var;

   var = ast_calloc(1, sizeof(*var));
   if (!var) {
      return -1;
   }

   var->name = ast_strdup(variable);
   if (!var->name) {
      free_chanvar(var);
      return -1;
   }

   /* It's kosher for value to be NULL. It means the variable is being unset */
   if (value) {
      var->value = ast_strdup(value);
      if (!var->value) {
         free_chanvar(var);
         return -1;
      }
   }

   stasis_app_send_command_async(control, app_control_set_channel_var, var, free_chanvar);

   return 0;
}

static int app_control_hold(struct stasis_app_control *control,
   struct ast_channel *chan, void *data)
{
   ast_indicate(control->channel, AST_CONTROL_HOLD);

   return 0;
}

void stasis_app_control_hold(struct stasis_app_control *control)
{
   stasis_app_send_command_async(control, app_control_hold, NULL, NULL);
}

static int app_control_unhold(struct stasis_app_control *control,
   struct ast_channel *chan, void *data)
{
   ast_indicate(control->channel, AST_CONTROL_UNHOLD);

   return 0;
}

void stasis_app_control_unhold(struct stasis_app_control *control)
{
   stasis_app_send_command_async(control, app_control_unhold, NULL, NULL);
}

static int app_control_moh_start(struct stasis_app_control *control,
   struct ast_channel *chan, void *data)
{
   char *moh_class = data;

   if (ast_channel_state(chan) != AST_STATE_UP) {
      ast_indicate(chan, AST_CONTROL_PROGRESS);
   }

   ast_moh_start(chan, moh_class, NULL);

   return 0;
}

void stasis_app_control_moh_start(struct stasis_app_control *control, const char *moh_class)
{
   char *data = NULL;

   if (!ast_strlen_zero(moh_class)) {
      data = ast_strdup(moh_class);
   }

   stasis_app_send_command_async(control, app_control_moh_start, data, ast_free_ptr);
}

static int app_control_moh_stop(struct stasis_app_control *control,
   struct ast_channel *chan, void *data)
{
   ast_moh_stop(chan);
   return 0;
}

void stasis_app_control_moh_stop(struct stasis_app_control *control)
{
   stasis_app_send_command_async(control, app_control_moh_stop, NULL, NULL);
}

static int app_control_silence_start(struct stasis_app_control *control,
   struct ast_channel *chan, void *data)
{
   if (ast_channel_state(chan) != AST_STATE_UP) {
      ast_indicate(chan, AST_CONTROL_PROGRESS);
   }

   if (control->silgen) {
      /* We have a silence generator, but it may have been implicitly
       * disabled by media actions (music on hold, playing media,
       * etc.) Just stop it and restart a new one.
       */
      ast_channel_stop_silence_generator(
         control->channel, control->silgen);
   }

   ast_debug(3, "%s: Starting silence generator\n",
      stasis_app_control_get_channel_id(control));
   control->silgen = ast_channel_start_silence_generator(control->channel);

   if (!control->silgen) {
      ast_log(LOG_WARNING,
         "%s: Failed to start silence generator.\n",
         stasis_app_control_get_channel_id(control));
   }

   return 0;
}

void stasis_app_control_silence_start(struct stasis_app_control *control)
{
   stasis_app_send_command_async(control, app_control_silence_start, NULL, NULL);
}

void control_silence_stop_now(struct stasis_app_control *control)
{
   if (control->silgen) {
      ast_debug(3, "%s: Stopping silence generator\n",
         stasis_app_control_get_channel_id(control));
      ast_channel_stop_silence_generator(
         control->channel, control->silgen);
      control->silgen = NULL;
   }
}

static int app_control_silence_stop(struct stasis_app_control *control,
   struct ast_channel *chan, void *data)
{
   control_silence_stop_now(control);
   return 0;
}

void stasis_app_control_silence_stop(struct stasis_app_control *control)
{
   stasis_app_send_command_async(control, app_control_silence_stop, NULL, NULL);
}

struct ast_channel_snapshot *stasis_app_control_get_snapshot(
   const struct stasis_app_control *control)
{
   return ast_channel_snapshot_get_latest(stasis_app_control_get_channel_id(control));
}

static int app_send_command_on_condition(struct stasis_app_control *control,
                stasis_app_command_cb command_fn, void *data,
                command_data_destructor_fn data_destructor,
                app_command_can_exec_cb can_exec_fn)
{
   int ret;
   struct stasis_app_command *command;

   if (control == NULL || control->is_done) {
      /* If exec_command_on_condition fails, it calls the data_destructor.
       * In order to provide consistent behavior, we'll also call the data_destructor
       * on this error path. This way, callers never have to call the
       * data_destructor themselves.
       */
      if (data_destructor) {
         data_destructor(data);
      }
      return -1;
   }

   command = exec_command_on_condition(
      control, command_fn, data, data_destructor, can_exec_fn);
   if (!command) {
      return -1;
   }

   ret = command_join(command);
   ao2_ref(command, -1);

   return ret;
}

int stasis_app_send_command(struct stasis_app_control *control,
   stasis_app_command_cb command_fn, void *data, command_data_destructor_fn data_destructor)
{
   return app_send_command_on_condition(control, command_fn, data, data_destructor, NULL);
}

int stasis_app_send_command_async(struct stasis_app_control *control,
   stasis_app_command_cb command_fn, void *data,
   command_data_destructor_fn data_destructor)
{
   struct stasis_app_command *command;

   if (control == NULL || control->is_done) {
      /* If exec_command fails, it calls the data_destructor. In order to
       * provide consistent behavior, we'll also call the data_destructor
       * on this error path. This way, callers never have to call the
       * data_destructor themselves.
       */
      if (data_destructor) {
         data_destructor(data);
      }
      return -1;
   }

   command = exec_command(control, command_fn, data, data_destructor);
   if (!command) {
      return -1;
   }
   ao2_ref(command, -1);

   return 0;
}

struct ast_bridge *stasis_app_get_bridge(struct stasis_app_control *control)
{
   struct ast_bridge *ret;

   if (!control) {
      return NULL;
   }

   ao2_lock(control);
   ret = control->bridge;
   ao2_unlock(control);

   return ret;
}

/*!
 * \brief Singleton dial bridge
 *
 * The dial bridge is a holding bridge used to hold all
 * outbound dialed channels that are not in any "real" ARI-created
 * bridge. The dial bridge is invisible, meaning that it does not
 * show up in channel snapshots, AMI or ARI output, and no events
 * get raised for it.
 *
 * This is used to keep dialed channels confined to the bridging system
 * and unify the threading model used for dialing outbound channels.
 */
static struct ast_bridge *dial_bridge;
AST_MUTEX_DEFINE_STATIC(dial_bridge_lock);

/*!
 * \brief Retrieve a reference to the dial bridge.
 *
 * If the dial bridge has not been created yet, it will
 * be created, otherwise, a reference to the existing bridge
 * will be returned.
 *
 * The caller will need to unreference the dial bridge once
 * they are finished with it.
 *
 * \retval NULL Unable to find/create the dial bridge
 * \retval non-NULL A reference to the dial bridge
 */
static struct ast_bridge *get_dial_bridge(void)
{
   struct ast_bridge *ret_bridge = NULL;

   ast_mutex_lock(&dial_bridge_lock);

   if (shutting_down) {
      goto end;
   }

   if (dial_bridge) {
      ret_bridge = ao2_bump(dial_bridge);
      goto end;
   }

   dial_bridge = stasis_app_bridge_create_invisible("holding", "dial_bridge", NULL);
   if (!dial_bridge) {
      goto end;
   }
   ret_bridge = ao2_bump(dial_bridge);

end:
   ast_mutex_unlock(&dial_bridge_lock);
   return ret_bridge;
}

static int bridge_channel_depart(struct stasis_app_control *control,
   struct ast_channel *chan, void *data);

/*!
 * \brief after bridge callback for the dial bridge
 *
 * The only purpose of this callback is to ensure that the control structure's
 * bridge pointer is NULLed
 */
static void dial_bridge_after_cb(struct ast_channel *chan, void *data)
{
   struct stasis_app_control *control = data;
   struct ast_bridge_channel *bridge_channel;

   ast_channel_lock(chan);
   bridge_channel = ast_channel_get_bridge_channel(chan);
   ast_channel_unlock(chan);

   ast_debug(3, "Channel: <%s>  Reason: %d\n", ast_channel_name(control->channel), ast_channel_hangupcause(chan));

   stasis_app_send_command_async(control, bridge_channel_depart, bridge_channel, __ao2_cleanup);

   control->bridge = NULL;
}

static void dial_bridge_after_cb_failed(enum ast_bridge_after_cb_reason reason, void *data)
{
   struct stasis_app_control *control = data;

   ast_debug(3, "Channel: <%s>  Reason: %d\n", ast_channel_name(control->channel), reason);
   dial_bridge_after_cb(control->channel, data);
}

/*!
 * \brief Add a channel to the singleton dial bridge.
 *
 * \param control The Stasis control structure
 * \param chan The channel to add to the bridge
 * \retval -1 Failed
 * \retval 0 Success
 */
static int add_to_dial_bridge(struct stasis_app_control *control, struct ast_channel *chan)
{
   struct ast_bridge *bridge;

   bridge = get_dial_bridge();
   if (!bridge) {
      return -1;
   }

   control->bridge = bridge;
   ast_bridge_set_after_callback(chan, dial_bridge_after_cb, dial_bridge_after_cb_failed, control);
   if (ast_bridge_impart(bridge, chan, NULL, NULL, AST_BRIDGE_IMPART_CHAN_DEPARTABLE)) {
      control->bridge = NULL;
      ao2_ref(bridge, -1);
      return -1;
   }

   ao2_ref(bridge, -1);

   return 0;
}

/*!
 * \brief Depart a channel from a bridge, and potentially add it back to the dial bridge
 *
 * \param control Take a guess
 * \param chan Take another guess
 */
static int depart_channel(struct stasis_app_control *control, struct ast_channel *chan)
{
   ast_bridge_depart(chan);

   /* Channels which have a PBX are not ones that have been created and dialed from ARI. They
    * have externally come in from the dialplan, and thus should not be placed into the dial
    * bridge. Only channels which are created and dialed in ARI should go into the dial bridge.
    */
   if (!ast_check_hangup(chan) && ast_channel_state(chan) != AST_STATE_UP && !ast_channel_pbx(chan)) {
      /* Channel is still being dialed, so put it back in the dialing bridge */
      add_to_dial_bridge(control, chan);
   }

   return 0;
}

static int bridge_channel_depart(struct stasis_app_control *control,
   struct ast_channel *chan, void *data)
{
   struct ast_bridge_channel *bridge_channel;

   ast_channel_lock(chan);
   bridge_channel = ast_channel_internal_bridge_channel(chan);
   ast_channel_unlock(chan);

   if (bridge_channel != data) {
      ast_debug(3, "%s: Channel is no longer in departable state\n",
         ast_channel_uniqueid(chan));
      return -1;
   }

   ast_debug(3, "%s: Channel departing bridge\n",
      ast_channel_uniqueid(chan));

   depart_channel(control, chan);

   return 0;
}

static void internal_bridge_after_cb(struct ast_channel *chan, void *data,
   enum ast_bridge_after_cb_reason reason)
{
   struct stasis_app_control *control = data;
   struct ast_bridge_channel *bridge_channel;

   ao2_lock(control);
   ast_debug(3, "%s, %s: %s\n",
      ast_channel_uniqueid(chan), control->bridge ? control->bridge->uniqueid : "unknown",
         ast_bridge_after_cb_reason_string(reason));

   if (reason == AST_BRIDGE_AFTER_CB_REASON_IMPART_FAILED) {
      /* The impart actually failed so control->bridge isn't valid. */
      control->bridge = NULL;
   }

   ast_assert(chan == control->channel);

   /* Restore the channel's PBX */
   ast_channel_pbx_set(control->channel, control->pbx);
   control->pbx = NULL;

   if (control->bridge) {
      app_unsubscribe_bridge(control->app, control->bridge);

      /* No longer in the bridge */
      control->bridge = NULL;

      /* Get the bridge channel so we don't depart from the wrong bridge */
      ast_channel_lock(chan);
      bridge_channel = ast_channel_get_bridge_channel(chan);
      ast_channel_unlock(chan);

      /* Depart this channel from the bridge using the command queue if possible */
      stasis_app_send_command_async(control, bridge_channel_depart, bridge_channel, __ao2_cleanup);
   }

   if (stasis_app_channel_is_stasis_end_published(chan)) {
      /* The channel has had a StasisEnd published on it, but until now had remained in
       * the bridging system. This means that the channel moved from a Stasis bridge to a
       * non-Stasis bridge and is now exiting the bridging system. Because of this, the
       * channel needs to exit the Stasis application and go to wherever the non-Stasis
       * bridge has directed it to go. If the non-Stasis bridge has not set up an after
       * bridge destination, then the channel should be hung up.
       */
      int hangup_flag;

      hangup_flag = ast_bridge_setup_after_goto(chan) ? AST_SOFTHANGUP_DEV : AST_SOFTHANGUP_ASYNCGOTO;
      ast_channel_lock(chan);
      ast_softhangup_nolock(chan, hangup_flag);
      ast_channel_unlock(chan);
   }
   ao2_unlock(control);
}

static void bridge_after_cb(struct ast_channel *chan, void *data)
{
   struct stasis_app_control *control = data;

   internal_bridge_after_cb(control->channel, data, AST_BRIDGE_AFTER_CB_REASON_DEPART);
}

static void bridge_after_cb_failed(enum ast_bridge_after_cb_reason reason,
   void *data)
{
   struct stasis_app_control *control = data;

   internal_bridge_after_cb(control->channel, data, reason);

   ast_debug(3, "  reason: %s\n",
      ast_bridge_after_cb_reason_string(reason));
}

/*!
 * \brief Dial timeout datastore
 *
 * A datastore is used because a channel may change
 * bridges during the course of a dial attempt. This
 * may be because the channel changes from the dial bridge
 * to a standard bridge, or it may move between standard
 * bridges. In order to keep the dial timeout, we need
 * to keep the timeout information local to the channel.
 * That is what this datastore is for
 */
struct ast_datastore_info timeout_datastore = {
   .type = "ARI dial timeout",
};

static int hangup_channel(struct stasis_app_control *control,
   struct ast_channel *chan, void *data)
{
   ast_softhangup(chan, AST_SOFTHANGUP_EXPLICIT);
   return 0;
}

/*!
 * \brief Dial timeout
 *
 * This is a bridge interval hook callback. The interval hook triggering
 * means that the dial timeout has been reached. If the channel has not
 * been answered by the time this callback is called, then the channel
 * is hung up
 *
 * \param bridge_channel Bridge channel on which interval hook has been called
 * \param ignore Ignored
 * \return -1 (i.e. remove the interval hook)
 */
static int bridge_timeout(struct ast_bridge_channel *bridge_channel, void *ignore)
{
   struct ast_datastore *datastore;
   RAII_VAR(struct stasis_app_control *, control, NULL, ao2_cleanup);

   control = stasis_app_control_find_by_channel(bridge_channel->chan);

   ast_channel_lock(bridge_channel->chan);
   if (ast_channel_state(bridge_channel->chan) != AST_STATE_UP) {
      /* Don't bother removing the datastore because it will happen when the channel is hung up */
      ast_channel_unlock(bridge_channel->chan);
      stasis_app_send_command_async(control, hangup_channel, NULL, NULL);
      return -1;
   }

   datastore = ast_channel_datastore_find(bridge_channel->chan, &timeout_datastore, NULL);
   if (!datastore) {
      ast_channel_unlock(bridge_channel->chan);
      return -1;
   }
   ast_channel_datastore_remove(bridge_channel->chan, datastore);
   ast_channel_unlock(bridge_channel->chan);
   ast_datastore_free(datastore);

   return -1;
}

/*!
 * \brief Set a dial timeout interval hook on the channel.
 *
 * The absolute time that the timeout should occur is stored on
 * a datastore on the channel. This time is converted into a relative
 * number of milliseconds in the future. Then an interval hook is set
 * to trigger in that number of milliseconds.
 *
 * \pre chan is locked
 *
 * \param chan The channel on which to set the interval hook
 */
static void set_interval_hook(struct ast_channel *chan)
{
   struct ast_datastore *datastore;
   struct timeval *hangup_time;
   int64_t ms;
   struct ast_bridge_channel *bridge_channel;

   datastore = ast_channel_datastore_find(chan, &timeout_datastore, NULL);
   if (!datastore) {
      return;
   }

   hangup_time = datastore->data;

   ms = ast_tvdiff_ms(*hangup_time, ast_tvnow());
   bridge_channel = ast_channel_get_bridge_channel(chan);
   if (!bridge_channel) {
      return;
   }

   if (ast_bridge_interval_hook(bridge_channel->features, 0, ms > 0 ? ms : 1,
         bridge_timeout, NULL, NULL, 0)) {
      ao2_ref(bridge_channel, -1);
      return;
   }

   ast_queue_frame(bridge_channel->chan, &ast_null_frame);
   ao2_ref(bridge_channel, -1);
}

int control_swap_channel_in_bridge(struct stasis_app_control *control, struct ast_bridge *bridge, struct ast_channel *chan, struct ast_channel *swap)
{
   int res;
   struct ast_bridge_features *features;
   int flags = AST_BRIDGE_IMPART_CHAN_DEPARTABLE;

   if (!control || !bridge) {
      return -1;
   }

   ast_debug(3, "%s: Adding to bridge %s\n",
      stasis_app_control_get_channel_id(control),
      bridge->uniqueid);

   ast_assert(chan != NULL);

   /* Depart whatever Stasis bridge we're currently in. */
   if (stasis_app_get_bridge(control)) {
      /* Note that it looks like there's a race condition here, since
       * we don't have control locked. But this happens from the
       * control callback thread, so there won't be any other
       * concurrent attempts to bridge.
       */
      ast_bridge_depart(chan);
   }


   res = ast_bridge_set_after_callback(chan, bridge_after_cb,
      bridge_after_cb_failed, control);
   if (res != 0) {
      ast_log(LOG_ERROR, "Error setting after-bridge callback\n");
      return -1;
   }

   ao2_lock(control);

   /* Ensure the controlling application is subscribed early enough
    * to receive the ChannelEnteredBridge message. This works in concert
    * with the subscription handled in the Stasis application execution
    * loop */
   app_subscribe_bridge(control->app, bridge);

   /* Save off the channel's PBX */
   ast_assert(control->pbx == NULL);
   if (!control->pbx) {
      control->pbx = ast_channel_pbx(chan);
      ast_channel_pbx_set(chan, NULL);
   }

   /* Pull bridge features from the control */
   features = control->bridge_features;
   control->bridge_features = NULL;
   if (features && features->inhibit_colp) {
      flags |= AST_BRIDGE_IMPART_INHIBIT_JOIN_COLP;
   }

   ast_assert(stasis_app_get_bridge(control) == NULL);
   /* We need to set control->bridge here since bridge_after_cb may be run
    * before ast_bridge_impart returns.  bridge_after_cb gets a reason
    * code so it can tell if the bridge is actually valid or not.
    */
   control->bridge = bridge;

   /* We can't be holding the control lock while impart is running
    * or we could create a deadlock with bridge_after_cb which also
    * tries to lock control.
    */
   ao2_unlock(control);
   res = ast_bridge_impart(bridge,
      chan,
      swap,
      features, /* features */
      flags);
   if (res != 0) {
      /* ast_bridge_impart failed before it could spawn the depart
       * thread.  The callbacks aren't called in this case.
       * The impart could still fail even if ast_bridge_impart returned
       * ok but that's handled by bridge_after_cb.
       */
      ast_log(LOG_ERROR, "Error adding channel to bridge\n");
      ao2_lock(control);
      ast_channel_pbx_set(chan, control->pbx);
      control->pbx = NULL;
      control->bridge = NULL;
      ao2_unlock(control);
   } else {
      ast_channel_lock(chan);
      set_interval_hook(chan);
      ast_channel_unlock(chan);
   }

   return res;
}

int control_add_channel_to_bridge(struct stasis_app_control *control, struct ast_channel *chan, void *data)
{
   return control_swap_channel_in_bridge(control, data, chan, NULL);
}

int stasis_app_control_add_channel_to_bridge(
   struct stasis_app_control *control, struct ast_bridge *bridge)
{
   ast_debug(3, "%s: Sending channel add_to_bridge command\n",
         stasis_app_control_get_channel_id(control));

   return app_send_command_on_condition(
      control, control_add_channel_to_bridge, bridge, NULL,
      app_control_can_add_channel_to_bridge);
}

static int app_control_remove_channel_from_bridge(
   struct stasis_app_control *control,
   struct ast_channel *chan, void *data)
{
   struct ast_bridge *bridge = data;

   if (!control) {
      return -1;
   }

   /* We should only depart from our own bridge */
   ast_debug(3, "%s: Departing bridge %s\n",
      stasis_app_control_get_channel_id(control),
      bridge->uniqueid);

   if (bridge != stasis_app_get_bridge(control)) {
      ast_log(LOG_WARNING, "%s: Not in bridge %s; not removing\n",
         stasis_app_control_get_channel_id(control),
         bridge->uniqueid);
      return -1;
   }

   depart_channel(control, chan);
   return 0;
}

int stasis_app_control_remove_channel_from_bridge(
   struct stasis_app_control *control, struct ast_bridge *bridge)
{
   ast_debug(3, "%s: Sending channel remove_from_bridge command\n",
         stasis_app_control_get_channel_id(control));
   return app_send_command_on_condition(
      control, app_control_remove_channel_from_bridge, bridge, NULL,
      app_control_can_remove_channel_from_bridge);
}

const char *stasis_app_control_get_channel_id(
   const struct stasis_app_control *control)
{
   return ast_channel_uniqueid(control->channel);
}

void stasis_app_control_publish(
   struct stasis_app_control *control, struct stasis_message *message)
{
   if (!control || !control->channel || !message) {
      return;
   }
   stasis_publish(ast_channel_topic(control->channel), message);
}

int stasis_app_control_queue_control(struct stasis_app_control *control,
   enum ast_control_frame_type frame_type)
{
   return ast_queue_control(control->channel, frame_type);
}

int stasis_app_control_bridge_features_init(
   struct stasis_app_control *control)
{
   struct ast_bridge_features *features;

   features = ast_bridge_features_new();
   if (!features) {
      return 1;
   }
   control->bridge_features = features;
   return 0;
}

void stasis_app_control_absorb_dtmf_in_bridge(
   struct stasis_app_control *control, int absorb)
{
   control->bridge_features->dtmf_passthrough = !absorb;
}

void stasis_app_control_mute_in_bridge(
   struct stasis_app_control *control, int mute)
{
   control->bridge_features->mute = mute;
}

void stasis_app_control_inhibit_colp_in_bridge(
   struct stasis_app_control *control, int inhibit_colp)
{
   control->bridge_features->inhibit_colp = inhibit_colp;
}

void control_flush_queue(struct stasis_app_control *control)
{
   struct ao2_iterator iter;
   struct stasis_app_command *command;

   iter = ao2_iterator_init(control->command_queue, AO2_ITERATOR_UNLINK);
   while ((command = ao2_iterator_next(&iter))) {
      command_complete(command, -1);
      ao2_ref(command, -1);
   }
   ao2_iterator_destroy(&iter);
}

int control_dispatch_all(struct stasis_app_control *control,
   struct ast_channel *chan)
{
   int count = 0;
   struct ao2_iterator iter;
   struct stasis_app_command *command;

   ast_assert(control->channel == chan);

   iter = ao2_iterator_init(control->command_queue, AO2_ITERATOR_UNLINK);
   while ((command = ao2_iterator_next(&iter))) {
      command_invoke(command, control, chan);
      ao2_ref(command, -1);
      ++count;
   }
   ao2_iterator_destroy(&iter);

   return count;
}

void control_wait(struct stasis_app_control *control)
{
   if (!control) {
      return;
   }

   ast_assert(control->command_queue != NULL);

   ao2_lock(control->command_queue);
   while (ao2_container_count(control->command_queue) == 0) {
      int res = ast_cond_wait(&control->wait_cond,
         ao2_object_get_lockaddr(control->command_queue));
      if (res < 0) {
         ast_log(LOG_ERROR, "Error waiting on command queue\n");
         break;
      }
   }
   ao2_unlock(control->command_queue);
}

int control_prestart_dispatch_all(struct stasis_app_control *control,
   struct ast_channel *chan)
{
   struct ao2_container *command_queue;
   int count = 0;
   struct ao2_iterator iter;
   struct stasis_app_command *command;

   ast_channel_lock(chan);
   command_queue = command_prestart_get_container(chan);
   ast_channel_unlock(chan);
   if (!command_queue) {
      return 0;
   }

   iter = ao2_iterator_init(command_queue, AO2_ITERATOR_UNLINK);

   while ((command = ao2_iterator_next(&iter))) {
      command_invoke(command, control, chan);
      ao2_cleanup(command);
      ++count;
   }

   ao2_iterator_destroy(&iter);
   ao2_cleanup(command_queue);
   return count;
}

struct stasis_app *control_app(struct stasis_app_control *control)
{
   return control->app;
}

struct control_dial_args {
   unsigned int timeout;
   char dialstring[0];
};

static struct control_dial_args *control_dial_args_alloc(const char *dialstring,
   unsigned int timeout)
{
   struct control_dial_args *args;

   args = ast_malloc(sizeof(*args) + strlen(dialstring) + 1);
   if (!args) {
      return NULL;
   }

   args->timeout = timeout;
   /* Safe */
   strcpy(args->dialstring, dialstring);

   return args;
}

static void control_dial_args_destroy(void *data)
{
   struct control_dial_args *args = data;

   ast_free(args);
}

/*!
 * \brief Set dial timeout on a channel to be dialed.
 *
 * \param chan The channel on which to set the dial timeout
 * \param timeout The timeout in seconds
 */
static int set_timeout(struct ast_channel *chan, unsigned int timeout)
{
   struct ast_datastore *datastore;
   struct timeval *hangup_time;

   hangup_time = ast_malloc(sizeof(struct timeval));

   datastore = ast_datastore_alloc(&timeout_datastore, NULL);
   if (!datastore) {
      return -1;
   }
   *hangup_time = ast_tvadd(ast_tvnow(), ast_samp2tv(timeout, 1));
   datastore->data = hangup_time;

   ast_channel_lock(chan);
   ast_channel_datastore_add(chan, datastore);

   if (ast_channel_is_bridged(chan)) {
      set_interval_hook(chan);
   }
   ast_channel_unlock(chan);

   return 0;
}

static int app_control_dial(struct stasis_app_control *control,
   struct ast_channel *chan, void *data)
{
   struct control_dial_args *args = data;
   int bridged;

   ast_channel_lock(chan);
   bridged = ast_channel_is_bridged(chan);
   ast_channel_unlock(chan);

   if (!bridged && add_to_dial_bridge(control, chan)) {
      return -1;
   }

   if (args->timeout && set_timeout(chan, args->timeout)) {
      return -1;
   }

   if (ast_call(chan, args->dialstring, 0)) {
      /* If call fails normally this channel would then just be normally hung up and destroyed.
       * In this case though the channel is being handled by the ARI control thread and dial
       * bridge which needs to be notified that the channel should be hung up. To do this we
       * queue a soft hangup which will cause each to wake up, see that the channel has been
       * hung up, and then destroy it.
       */
      int hangup_flag;
      hangup_flag = ast_bridge_setup_after_goto(chan) ? AST_SOFTHANGUP_DEV : AST_SOFTHANGUP_ASYNCGOTO;
      ast_channel_lock(chan);
      ast_softhangup_nolock(chan, hangup_flag);
      ast_channel_unlock(chan);
      return -1;
   }

   ast_channel_publish_dial(NULL, chan, args->dialstring, NULL);

   return 0;
}

int stasis_app_control_dial(struct stasis_app_control *control,
      const char *dialstring, unsigned int timeout)
{
   struct control_dial_args *args;

   args = control_dial_args_alloc(dialstring, timeout);
   if (!args) {
      return -1;
   }

   return stasis_app_send_command_async(control, app_control_dial,
      args, control_dial_args_destroy);
}

void stasis_app_control_shutdown(void)
{
   ast_mutex_lock(&dial_bridge_lock);
   shutting_down = 1;
   if (dial_bridge) {
      ast_bridge_destroy(dial_bridge, 0);
      dial_bridge = NULL;
   }
   ast_mutex_unlock(&dial_bridge_lock);
}

void control_set_app(struct stasis_app_control *control, struct stasis_app *app)
{
   ao2_cleanup(control->app);
   control->app = ao2_bump(app);
}

char *control_next_app(struct stasis_app_control *control)
{
   return control->next_app;
}

void control_move_cleanup(struct stasis_app_control *control)
{
   ast_free(control->next_app);
   control->next_app = NULL;

   AST_VECTOR_RESET(&control->next_app_args, ast_free_ptr);
}

char **control_next_app_args(struct stasis_app_control *control)
{
   return AST_VECTOR_STEAL_ELEMENTS(&control->next_app_args);
}

int control_next_app_args_size(struct stasis_app_control *control)
{
   return AST_VECTOR_SIZE(&control->next_app_args);
}