app_attended_transfer.c

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/*
 * Asterisk -- An open source telephony toolkit.
 *
 * Copyright (C) 2019, Alexei Gradinari
 *
 * Alexei Gradinari <alex2grad@gmail.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 Attended transfer by caller channel
 *
 * \author Alexei Gradinari <alex2grad@gmail.com>
 *
 * \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");