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devicestate.c

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/*
 * Asterisk -- An open source telephony toolkit.
 *
 * Copyright (C) 1999 - 2006, Digium, Inc.
 *
 * Mark Spencer <markster@digium.com>
 *
 * See http://www.asterisk.org for more information about
 * the Asterisk project. Please do not directly contact
 * any of the maintainers of this project for assistance;
 * the project provides a web site, mailing lists and IRC
 * channels for your use.
 *
 * This program is free software, distributed under the terms of
 * the GNU General Public License Version 2. See the LICENSE file
 * at the top of the source tree.
 */

/*! \file
 *
 * \brief Device state management
 *
 *
 * \author Mark Spencer <markster@digium.com> 
 *
 * \arg \ref AstExtState
 */
/*! \page AstExtState Extension and device states in Asterisk
 *
 * Asterisk has an internal system that reports states
 * for an extension. By using the dialplan priority -1,
 * also called a \b hint, a connection can be made from an
 * extension to one or many devices. The state of the extension
 * now depends on the combined state of the devices.
 *
 * The device state is basically based on the current calls.
 * If the devicestate engine can find a call from or to the
 * device, it's in use.
 * 
 * Some channel drivers implement a callback function for 
 * a better level of reporting device states. The SIP channel
 * has a complicated system for this, which is improved 
 * by adding call limits to the configuration.
 * 
 * Functions that want to check the status of an extension
 * register themself as a \b watcher.
 * Watchers in this system can subscribe either to all extensions
 * or just a specific extensions.
 *
 * For non-device related states, there's an API called
 * devicestateproviders. This is an extendable system for
 * delivering state information from outside sources or
 * functions within Asterisk. Currently we have providers
 * for app_meetme.c - the conference bridge - and call
 * parking (metermaids).
 *
 * There are manly three subscribers to extension states 
 * within Asterisk:
 * - AMI, the manager interface
 * - app_queue.c - the Queue dialplan application
 * - SIP subscriptions, a.k.a. "blinking lamps" or 
 *   "buddy lists"
 *
 * The CLI command "show hints" show last known state
 *
 * \note None of these handle user states, like an IM presense
 * system. res_jabber.c can subscribe and watch such states
 * in jabber/xmpp based systems.
 *
 * \section AstDevStateArch Architecture for devicestates
 *
 * When a channel driver or asterisk app changes state for 
 * a watched object, it alerts the core. The core queues
 * a change. When the change is processed, there's a query
 * sent to the channel driver/provider if there's a function
 * to handle that, otherwise a channel walk is issued to find
 * a channel that involves the object.
 * 
 * The changes are queued and processed by a separate thread.
 * This thread calls the watchers subscribing to status 
 * changes for the object. For manager, this results 
 * in events. For SIP, NOTIFY requests.
 *
 * - Device states
 *    \arg \ref devicestate.c 
 *    \arg \ref devicestate.h 
 *
 * \section AstExtStateArch Architecture for extension states
 * 
 * Hints are connected to extension. If an extension changes state
 * it checks the hint devices. If there is a hint, the callbacks into
 * device states are checked. The aggregated state is set for the hint
 * and reported back.
 *
 * - Extension states
 *    \arg \ref enum ast_extension_states
 *    \arg \ref pbx.c 
 *    \arg \ref pbx.h 
 * - Structures
 *    - \ref struct ast_state_cb  Callbacks for watchers
 *    - Callback ast_state_cb_type
 *    - \ref struct ast_hint
 *    - Functions
 *    - ast_extension_state_add()
 *    - ast_extension_state_del()
 *    - ast_get_hint()
 * 
 */

#include "asterisk.h"

ASTERISK_FILE_VERSION(__FILE__, "$Revision: 53128 $")

#include <sys/types.h>
#include <unistd.h>
#include <stdlib.h>
#include <string.h>
#include <stdio.h>

#include "asterisk/channel.h"
#include "asterisk/utils.h"
#include "asterisk/lock.h"
#include "asterisk/linkedlists.h"
#include "asterisk/logger.h"
#include "asterisk/devicestate.h"
#include "asterisk/pbx.h"
#include "asterisk/app.h"
#include "asterisk/options.h"

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

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

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

/*! \brief  A device state watcher (callback) */
struct devstate_cb {
   void *data;
   ast_devstate_cb_type callback;   /*!< Where to report when state changes */
   AST_RWLIST_ENTRY(devstate_cb) list;
};

/*! \brief A device state watcher list */
static AST_RWLIST_HEAD_STATIC(devstate_cbs, devstate_cb);

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

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

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

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

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

/*! \brief Find devicestate as text message for output */
const char *devstate2str(int devstate) 
{
   return devstatestring[devstate];
}

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

   ast_copy_string(match, device, sizeof(match)-1);
   strcat(match, "-");
   chan = ast_get_channel_by_name_prefix_locked(match, strlen(match));

   if (!chan)
      return AST_DEVICE_UNKNOWN;

   if (chan->_state == AST_STATE_RINGING)
      res = AST_DEVICE_RINGING;
   else
      res = AST_DEVICE_INUSE;
   
   ast_channel_unlock(chan);

   return res;
}

/*! \brief Check device state through channel specific function or generic function */
int ast_device_state(const char *device)
{
   char *buf;
   char *number;
   const struct ast_channel_tech *chan_tech;
   int res = 0;
   /*! \brief Channel driver that provides device state */
   char *tech;
   /*! \brief Another provider of device state */
   char *provider = NULL;
   
   buf = ast_strdupa(device);
   tech = strsep(&buf, "/");
   if (!(number = buf)) {
      if (!(provider = strsep(&tech, ":")))
         return AST_DEVICE_INVALID;
      /* We have a provider */
      number = tech;
      tech = NULL;
   }

   if (provider)  {
      if (option_debug > 2)
         ast_log(LOG_DEBUG, "Checking if I can find provider for \"%s\" - number: %s\n", provider, number);
      return getproviderstate(provider, number);
   }

   if (option_debug > 3)
      ast_log(LOG_DEBUG, "No provider found, checking channel drivers for %s - %s\n", tech, number);

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

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

   res = chan_tech->devicestate(number);

   if (res != AST_DEVICE_UNKNOWN)
      return res;

   res = ast_parse_device_state(device);

   if (res == AST_DEVICE_UNKNOWN)
      return AST_DEVICE_NOT_INUSE;

   return res;
}

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

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

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

   AST_RWLIST_WRLOCK(&devstate_provs);
   AST_RWLIST_INSERT_HEAD(&devstate_provs, devprov, list);
   AST_RWLIST_UNLOCK(&devstate_provs);

   return 0;
}

/*! \brief Remove device state provider */
void ast_devstate_prov_del(const char *label)
{
   struct devstate_prov *devcb;

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

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


   AST_RWLIST_RDLOCK(&devstate_provs);
   AST_RWLIST_TRAVERSE(&devstate_provs, devprov, list) {
      if (option_debug > 4)
         ast_log(LOG_DEBUG, "Checking provider %s with %s\n", devprov->label, provider);

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

/*! \brief Add device state watcher */
int ast_devstate_add(ast_devstate_cb_type callback, void *data)
{
   struct devstate_cb *devcb;

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

   devcb->data = data;
   devcb->callback = callback;

   AST_RWLIST_WRLOCK(&devstate_cbs);
   AST_RWLIST_INSERT_HEAD(&devstate_cbs, devcb, list);
   AST_RWLIST_UNLOCK(&devstate_cbs);

   return 0;
}

/*! \brief Remove device state watcher */
void ast_devstate_del(ast_devstate_cb_type callback, void *data)
{
   struct devstate_cb *devcb;

   AST_RWLIST_WRLOCK(&devstate_cbs);
   AST_RWLIST_TRAVERSE_SAFE_BEGIN(&devstate_cbs, devcb, list) {
      if ((devcb->callback == callback) && (devcb->data == data)) {
         AST_RWLIST_REMOVE_CURRENT(&devstate_cbs, list);
         free(devcb);
         break;
      }
   }
   AST_RWLIST_TRAVERSE_SAFE_END;
   AST_RWLIST_UNLOCK(&devstate_cbs);
}

/*! \brief Notify callback watchers of change, and notify PBX core for hint updates
   Normally executed within a separate thread
*/
static void do_state_change(const char *device)
{
   int state;
   struct devstate_cb *devcb;

   state = ast_device_state(device);
   if (option_debug > 2)
      ast_log(LOG_DEBUG, "Changing state for %s - state %d (%s)\n", device, state, devstate2str(state));

   AST_RWLIST_RDLOCK(&devstate_cbs);
   AST_RWLIST_TRAVERSE(&devstate_cbs, devcb, list)
      devcb->callback(device, state, devcb->data);
   AST_RWLIST_UNLOCK(&devstate_cbs);

   ast_hint_state_changed(device);
}

static int __ast_device_state_changed_literal(char *buf)
{
   char *device, *tmp;
   struct state_change *change;

   if (option_debug > 2)
      ast_log(LOG_DEBUG, "Notification of state change to be queued on device/channel %s\n", buf);

   device = buf;
   if ((tmp = strrchr(device, '-')))
      *tmp = '\0';

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

   return 1;
}

int ast_device_state_changed_literal(const char *dev)
{
   char *buf;
   buf = ast_strdupa(dev);
   return __ast_device_state_changed_literal(buf);
}

/*! \brief Accept change notification, add it to change queue */
int ast_device_state_changed(const char *fmt, ...) 
{
   char buf[AST_MAX_EXTENSION];
   va_list ap;

   va_start(ap, fmt);
   vsnprintf(buf, sizeof(buf), fmt, ap);
   va_end(ap);
   return __ast_device_state_changed_literal(buf);
}

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

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

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

   return NULL;
}

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

   return 0;
}

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