app_attended_transfer.c

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/*
 * Asterisk -- An open source telephony toolkit.
 *
 * Copyright (C) 2019, Alexei Gradinari
 *
 * Alexei Gradinari <[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 Attended transfer by caller channel
 *
 * \author Alexei Gradinari <[email protected]>
 *
 * \ingroup applications
 */

/*** MODULEINFO
   <support_level>extended</support_level>
 ***/

#include "asterisk.h"

#include "asterisk/pbx.h"
#include "asterisk/module.h"
#include "asterisk/app.h"
#include "asterisk/channel.h"
#include "asterisk/bridge.h"
#include "asterisk/features_config.h"

/*** DOCUMENTATION
   <application name="AttendedTransfer" language="en_US">
      <synopsis>
         Attended transfer to the extension provided and TRANSFER_CONTEXT
      </synopsis>
      <syntax>
         <parameter name="exten" required="true">
            <para>Specify extension.</para>
         </parameter>
      </syntax>
      <description>
         <para>Queue up attended transfer to the specified extension in the <literal>TRANSFER_CONTEXT</literal>.</para>
         <para>Note that the attended transfer only work when two channels have answered and are bridged together.</para>
         <para>Make sure to set Attended Transfer DTMF feature <literal>atxfer</literal>
         and attended transfer is permitted.</para>
         <para>The result of the application will be reported in the <variable>ATTENDEDTRANSFERSTATUS</variable>
         channel variable:</para>
         <variablelist>
            <variable name="ATTENDEDTRANSFERSTATUS">
               <value name="SUCCESS">
                  Transfer successfully queued.
               </value>
               <value name="FAILURE">
                  Transfer failed.
               </value>
               <value name="NOTPERMITTED">
                  Transfer not permitted.
               </value>
            </variable>
         </variablelist>
      </description>
   </application>
 ***/

static const char * const app = "AttendedTransfer";

static int attended_transfer_exec(struct ast_channel *chan, const char *data)
{
   char *exten = NULL;
   const char *context = NULL;
   char *parse;
   AST_DECLARE_APP_ARGS(args,
      AST_APP_ARG(exten);
   );
   char feature_code[AST_FEATURE_MAX_LEN];
   const char *digit;
   struct ast_frame f = { .frametype = AST_FRAME_DTMF };

   if (ast_strlen_zero((char *)data)) {
      ast_log(LOG_WARNING, "%s requires an argument (exten)\n", app);
      pbx_builtin_setvar_helper(chan, "ATTENDEDTRANSFERSTATUS", "FAILURE");
      return 0;
   }

   context = pbx_builtin_getvar_helper(chan, "TRANSFER_CONTEXT");
   if (ast_strlen_zero(context)) {
      pbx_builtin_setvar_helper(chan, "ATTENDEDTRANSFERSTATUS", "NOTPERMITTED");
      return 0;
   }

   ast_channel_lock(chan);
   if (ast_get_builtin_feature(chan, "atxfer", feature_code, sizeof(feature_code)) ||
      ast_strlen_zero(feature_code)) {
      pbx_builtin_setvar_helper(chan, "ATTENDEDTRANSFERSTATUS", "NOTPERMITTED");
      ast_channel_unlock(chan);
      return 0;
   }
   ast_channel_unlock(chan);

   parse = ast_strdupa(data);
   AST_STANDARD_APP_ARGS(args, parse);

   exten = args.exten;

   for (digit = feature_code; *digit; ++digit) {
      f.subclass.integer = *digit;
      ast_queue_frame(chan, &f);
   }

   for (digit = exten; *digit; ++digit) {
      f.subclass.integer = *digit;
      ast_queue_frame(chan, &f);
   }

   f.subclass.integer = '#';
   ast_queue_frame(chan, &f);

   pbx_builtin_setvar_helper(chan, "ATTENDEDTRANSFERSTATUS", "SUCCESS");

   return 0;
}

static int unload_module(void)
{
   return ast_unregister_application(app);
}

static int load_module(void)
{
   return ast_register_application_xml(app, attended_transfer_exec);
}

AST_MODULE_INFO_STANDARD_EXTENDED(ASTERISK_GPL_KEY, "Attended transfer to the given extension");