/*
 * Asterisk -- An open source telephony toolkit.
 *
 * Copyright (C) 2013, Digium, Inc.
 *
 * Kevin Harwell <kharwell@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.
 */

/*** MODULEINFO
	<depend>pjproject</depend>
	<depend>res_pjsip</depend>
	<depend>res_pjsip_session</depend>
	<support_level>core</support_level>
 ***/

#include "asterisk.h"

#include <pjsip.h>
#include <pjsip_ua.h>

#include "asterisk/res_pjsip.h"
#include "asterisk/res_pjsip_session.h"
#include "asterisk/callerid.h"
#include "asterisk/channel.h"
#include "asterisk/module.h"
#include "asterisk/strings.h"

static const pj_str_t diversion_name = { "Diversion", 9 };
static const pj_str_t history_info_name = { "History-Info", 12 };
static pj_str_t HISTINFO_SUPPORTED_NAME = { "histinfo", 8 };

/*
 * Should we queue a frame with the updated redirecting information.
 */
typedef enum  {
	PJSIP_DIVERSION_NOSEND_UPDATE = 0,
	PJSIP_DIVERSION_SEND_UPDATE = 1,
} pjsip_diversion_send_update;

/*!
 * \internal
 * \brief Determine if the given string is a SIP token.
 * \since 13.8.0
 *
 * \param str String to determine if is a SIP token.
 *
 * \note A token is defined by RFC3261 Section 25.1
 *
 * \return Non-zero if the string is a SIP token.
 */
static int sip_is_token(const char *str)
{
	int is_token;

	if (ast_strlen_zero(str)) {
		/* An empty string is not a token. */
		return 0;
	}

	is_token = 1;
	do {
		if (!isalnum(*str)
			&& !strchr("-.!%*_+`'~", *str)) {
			/* The character is not allowed in a token. */
			is_token = 0;
			break;
		}
	} while (*++str);

	return is_token;
}

/*! \brief Diversion header reasons
 *
 * The core defines a bunch of constants used to define
 * redirecting reasons. This provides a translation table
 * between those and the strings which may be present in
 * a SIP Diversion header
 */
static const struct reasons {
	enum AST_REDIRECTING_REASON code;
	const char *text;
	const unsigned int cause;
} reason_table[] = {
	{ AST_REDIRECTING_REASON_UNKNOWN, "unknown", 404 },
	{ AST_REDIRECTING_REASON_USER_BUSY, "user-busy", 486 },
	{ AST_REDIRECTING_REASON_NO_ANSWER, "no-answer", 408 },
	{ AST_REDIRECTING_REASON_UNAVAILABLE, "unavailable", 503 },
	{ AST_REDIRECTING_REASON_UNCONDITIONAL, "unconditional", 302 },
	{ AST_REDIRECTING_REASON_TIME_OF_DAY, "time-of-day", 404 },
	{ AST_REDIRECTING_REASON_DO_NOT_DISTURB, "do-not-disturb", 404 },
	{ AST_REDIRECTING_REASON_DEFLECTION, "deflection", 480 },
	{ AST_REDIRECTING_REASON_FOLLOW_ME, "follow-me", 404 },
	{ AST_REDIRECTING_REASON_OUT_OF_ORDER, "out-of-service", 404 },
	{ AST_REDIRECTING_REASON_AWAY, "away", 404 },
	{ AST_REDIRECTING_REASON_CALL_FWD_DTE, "cf_dte", 404 },		/* Non-standard */
	{ AST_REDIRECTING_REASON_SEND_TO_VM, "send_to_vm", 404 },	/* Non-standard */
};

static enum AST_REDIRECTING_REASON cause_to_reason(const unsigned long cause) {
	switch(cause) {
		case 302:
			return AST_REDIRECTING_REASON_UNCONDITIONAL;
		case 486:
			return AST_REDIRECTING_REASON_USER_BUSY;
		case 408:
			return AST_REDIRECTING_REASON_NO_ANSWER;
		case 480:
		case 487:
			return AST_REDIRECTING_REASON_DEFLECTION;
		case 503:
			return AST_REDIRECTING_REASON_UNAVAILABLE;
		default:
			return AST_REDIRECTING_REASON_UNKNOWN;
	}
}

static int add_supported(pjsip_tx_data *tdata)
{
	pjsip_supported_hdr *hdr;
	unsigned int i;

	hdr = pjsip_msg_find_hdr(tdata->msg, PJSIP_H_SUPPORTED, NULL);
	if (!hdr) {
		/* insert a new Supported header */
		hdr = pjsip_supported_hdr_create(tdata->pool);
		if (!hdr) {
			return -1;
		}

		pjsip_msg_add_hdr(tdata->msg, (pjsip_hdr *)hdr);
	}

	/* Asterisk can send multiple "181 Call forwarded" in a single session,
	 * we might have already modified Supported before
	 */
	for (i = 0; i < hdr->count; ++i) {
		if (pj_stricmp(&hdr->values[i], &HISTINFO_SUPPORTED_NAME) == 0) {
			return 0;
		}
	}

	if (hdr->count >= PJSIP_GENERIC_ARRAY_MAX_COUNT) {
		return -1;
	}

	/* add on to the existing Supported header */
	pj_strassign(&hdr->values[hdr->count++], &HISTINFO_SUPPORTED_NAME);

	return 0;
}

static const char *reason_code_to_str(const struct ast_party_redirecting_reason *reason)
{
	int idx;
	int code;

	/* use specific string if given */
	if (!ast_strlen_zero(reason->str)) {
		return reason->str;
	}

	code = reason->code;
	for (idx = 0; idx < ARRAY_LEN(reason_table); ++idx) {
		if (code == reason_table[idx].code) {
			return reason_table[idx].text;
		}
	}

	return "unknown";
}

static const unsigned int reason_code_to_cause(const struct ast_party_redirecting_reason *reason)
{
	int idx;
	int code;

	code = reason->code;
	for (idx = 0; idx < ARRAY_LEN(reason_table); ++idx) {
		if (code == reason_table[idx].code) {
			return reason_table[idx].cause;
		}
	}

	return 404;
}

static pjsip_fromto_hdr *get_diversion_header(pjsip_rx_data *rdata)
{
	static const pj_str_t from_name = { "From", 4 };

	pjsip_generic_string_hdr *hdr;
	pj_str_t value;
	int size;

	if (!(hdr = pjsip_msg_find_hdr_by_name(rdata->msg_info.msg, &diversion_name, NULL))) {
		return NULL;
	}

	pj_strdup_with_null(rdata->tp_info.pool, &value, &hdr->hvalue);

	/* parse as a fromto header */
	return pjsip_parse_hdr(rdata->tp_info.pool, &from_name, value.ptr,
			       pj_strlen(&value), &size);
}

/* Asterisk keeps track of 2 things. The redirected from address and
 * the redirected to address. If first=0 method will get the most recent
 * redirection target for use as the redirected to address. If first=1
 * then this method will get the original redirection target (index=1)
 * for use as the redirected from address.
 */
static pjsip_fromto_hdr *get_history_info_header(pjsip_rx_data *rdata, const unsigned int first)
{
	static const pj_str_t from_name = { "From", 4 };
	pjsip_fromto_hdr * result_hdr = NULL;

	pjsip_generic_string_hdr *hdr = NULL;

	hdr = pjsip_msg_find_hdr_by_name(rdata->msg_info.msg, &history_info_name, NULL);

	if (!hdr) {
		return NULL;
	}

	do {
		static const pj_str_t index_name = { "index", 5 };
		pj_str_t value;
		int size;
		pjsip_fromto_hdr * fromto_hdr = NULL;
		pjsip_param * index = NULL;

		pj_strdup_with_null(rdata->tp_info.pool, &value, &hdr->hvalue);

		/* parse as a fromto header */
		fromto_hdr =  pjsip_parse_hdr(rdata->tp_info.pool, &from_name, value.ptr,
				       pj_strlen(&value), &size);

		if (fromto_hdr == NULL) {
			continue;
		}

		index = pjsip_param_find(&fromto_hdr->other_param, &index_name);

		if (index) {
			if (!pj_strcmp2(&index->value, "1")) {
				if (!first) {
					continue;
				} else {
					return fromto_hdr;
				}
			}
		}

		result_hdr = fromto_hdr;

	} while ((hdr = pjsip_msg_find_hdr_by_name(rdata->msg_info.msg, &history_info_name, hdr->next)));

	return result_hdr;
}

static void set_redirecting_value(char **dst, const pj_str_t *src)
{
	ast_free(*dst);
	*dst = ast_malloc(pj_strlen(src) + 1);
	if (*dst) {
		ast_copy_pj_str(*dst, src, pj_strlen(src) + 1);
	}
}

static void set_redirecting_id(pjsip_name_addr *name_addr, struct ast_party_id *data,
			       struct ast_set_party_id *update)
{
	pjsip_sip_uri *uri = pjsip_uri_get_uri(name_addr->uri);
	char *semi;
	pj_str_t uri_user;

	uri_user = uri->user;

	/* Always truncate redirecting number at a semicolon. */
	semi = pj_strchr(&uri_user, ';');
	if (semi) {
		/*
		 * We need to be able to handle URI's looking like
		 * "sip:1235557890;phone-context=national@x.x.x.x;user=phone"
		 *
		 * Where the uri->user field will result in:
		 * "1235557890;phone-context=national"
		 *
		 * People don't care about anything after the semicolon
		 * showing up on their displays even though the RFC
		 * allows the semicolon.
		 */
		pj_strset(&uri_user, (char *) pj_strbuf(&uri_user), semi - pj_strbuf(&uri_user));
	}

	if (pj_strlen(&uri_user)) {
		update->number = 1;
		data->number.valid = 1;
		set_redirecting_value(&data->number.str, &uri_user);
	}

	if (pj_strlen(&name_addr->display)) {
		update->name = 1;
		data->name.valid = 1;
		set_redirecting_value(&data->name.str, &name_addr->display);
	}
}

static void copy_redirecting_id(struct ast_party_id *dst, const struct ast_party_id *src,
				struct ast_set_party_id *update)
{
	ast_party_id_copy(dst, src);

	if (dst->number.valid) {
		update->number = 1;
	}

	if (dst->name.valid) {
		update->name = 1;
	}
}

static void set_redirecting_reason_by_cause(pjsip_name_addr *name_addr,
				   struct ast_party_redirecting_reason *data)
{
	static const pj_str_t cause_name = { "cause", 5 };
	pjsip_uri *uri = name_addr->uri;
	pjsip_param *cause = NULL;
	unsigned long cause_value = 0;

	if (!ast_sip_is_allowed_uri(uri)) {
		return;
	}

	cause = ast_sip_pjsip_uri_get_other_param(uri, &cause_name);

	if (!cause) {
		return;
	}

	cause_value = pj_strtoul(&cause->value);

	data->code = cause_to_reason(cause_value);
	ast_free(data->str);
	data->str = ast_strdup("");
}

static void set_redirecting_reason(pjsip_fromto_hdr *from_info, pjsip_name_addr *to_info,
				   struct ast_party_redirecting_reason *data)
{
	static const pj_str_t reason_name = { "reason", 6 };
	pjsip_param *reason = pjsip_param_find(&from_info->other_param, &reason_name);
	char *reason_str;

	if (!reason) {
		if (to_info) {
			set_redirecting_reason_by_cause(to_info, data);
		}
		return;
	}

	set_redirecting_value(&data->str, &reason->value);
	if (!data->str) {
		/* Oops, allocation failure */
		return;
	}
	reason_str = ast_strdupa(data->str);

	/* Remove any enclosing double-quotes */
	if (*reason_str == '"') {
		reason_str = ast_strip_quoted(reason_str, "\"", "\"");
	}

	data->code = ast_redirecting_reason_parse(reason_str);
	if (data->code < 0) {
		data->code = AST_REDIRECTING_REASON_UNKNOWN;
	} else {
		ast_free(data->str);
		data->str = ast_strdup("");
	}
}

static void set_redirecting(struct ast_sip_session *session,
			    pjsip_fromto_hdr *from_info,
			    pjsip_name_addr *to_info,
			    pjsip_diversion_send_update send_update)
{
	struct ast_party_redirecting data;
	struct ast_set_party_redirecting update;

	if (!session->channel) {
		return;
	}

	ast_party_redirecting_init(&data);
	memset(&update, 0, sizeof(update));

	data.reason.code = AST_REDIRECTING_REASON_UNKNOWN;
	if (from_info) {
		set_redirecting_id((pjsip_name_addr*)from_info->uri,
			&data.from, &update.from);
		set_redirecting_reason(from_info, to_info, &data.reason);
		ast_set_party_id_all(&update.priv_to);
	} else {
		copy_redirecting_id(&data.from, &session->id, &update.from);
	}

	if (to_info) {
		set_redirecting_id(to_info, &data.to, &update.to);
	}

	ast_set_party_id_all(&update.priv_orig);
	ast_set_party_id_all(&update.priv_from);
	ast_set_party_id_all(&update.priv_to);
	++data.count;

	ast_channel_set_redirecting(session->channel, &data, &update);
	/* Only queue an indication if it was due to a response received pre media*/
	if (session->inv_session->role == PJSIP_ROLE_UAC && send_update) {
		ast_channel_queue_redirecting_update(session->channel, &data, &update);
	}
	ast_party_redirecting_free(&data);
}

static int diversion_incoming_request(struct ast_sip_session *session, pjsip_rx_data *rdata)
{
	pjsip_fromto_hdr *hdr = get_diversion_header(rdata);

	if (hdr) {
		set_redirecting(session, hdr, (pjsip_name_addr*)
				PJSIP_MSG_TO_HDR(rdata->msg_info.msg)->uri, PJSIP_DIVERSION_SEND_UPDATE);
	} else {
		pjsip_fromto_hdr *history_info_to;
		pjsip_fromto_hdr *history_info_from;
		history_info_to  = get_history_info_header(rdata, 0);

		if (history_info_to) {
			/* If History-Info is present, then it will also include the original
			   redirected-from in addition to the redirected-to */
			history_info_from = get_history_info_header(rdata, 1);
			set_redirecting(session, history_info_from, (pjsip_name_addr*)history_info_to->uri, PJSIP_DIVERSION_SEND_UPDATE);
		}
	}

	return 0;
}

static void diversion_incoming_response(struct ast_sip_session *session, pjsip_rx_data *rdata, pjsip_diversion_send_update send_update)
{
	static const pj_str_t contact_name = { "Contact", 7 };
	static const pj_str_t contact_name_s = { "m", 1 };

	pjsip_status_line status = rdata->msg_info.msg->line.status;
	pjsip_fromto_hdr *div_hdr;
	pjsip_fromto_hdr *history_info_to;
	pjsip_fromto_hdr *history_info_from;
	pjsip_contact_hdr *contact_hdr;

	if ((status.code != 302) && (status.code != 181)) {
		return;
	}

	/* use the diversion header info if there is one. if not one then use the
	   the history-info, if that doesn't exist, use session caller id info. if
	   that doesn't exist use info from the To hdr*/
	if (!(div_hdr = get_diversion_header(rdata))) {
		history_info_to  = get_history_info_header(rdata, 0);

		if (history_info_to) {
			/* If History-Info is present, then it will also include the original
			   redirected-from in addition to the redirected-to */
			history_info_from = get_history_info_header(rdata, 1);
			set_redirecting(session, history_info_from, (pjsip_name_addr*)history_info_to->uri, send_update);
			return;
		}
		if (!div_hdr && !session->id.number.valid) {
			div_hdr = PJSIP_MSG_TO_HDR(rdata->msg_info.msg);
		}
	}


	if (status.code == 302) {
		/* With 302, Contact indicates the final destination and possibly Diversion indicates the hop before */
		contact_hdr = pjsip_msg_find_hdr_by_names(rdata->msg_info.msg, &contact_name, &contact_name_s, NULL);
		set_redirecting(session, div_hdr, contact_hdr ?	(pjsip_name_addr*)contact_hdr->uri :
				(pjsip_name_addr*)PJSIP_MSG_FROM_HDR(rdata->msg_info.msg)->uri, send_update);
	} else {
		/* With 181, Diversion is non-standard, but if present indicates the new final destination, and To indicating the original */
		set_redirecting(session, PJSIP_MSG_TO_HDR(rdata->msg_info.msg),
				div_hdr ? (pjsip_name_addr*)div_hdr->uri : NULL, send_update);
	}
}

static void diversion_incoming_response_media(struct ast_sip_session *session, pjsip_rx_data *rdata)
{
	/* Trigger an update if the event is triggered by the PJSIP AST_SIP_SESSION_BEFORE_MEDIA callback */
	diversion_incoming_response(session, rdata, PJSIP_DIVERSION_SEND_UPDATE);
	return;
}

static void diversion_incoming_response_redirecting(struct ast_sip_session *session, pjsip_rx_data *rdata)
{
	/* Don't trigger an update if the event is triggered by the PJSIP AST_SIP_SESSION_REDIRECTING callback
	   otherwise, we will send a duplicate 181 to the UAC */
	diversion_incoming_response(session, rdata, PJSIP_DIVERSION_NOSEND_UPDATE);
	return;
}

/*!
 * \internal
 * \brief Adds diversion header information to an outbound SIP message
 *
 * \param tdata The outbound message
 * \param data The redirecting data used to fill parts of the diversion header
 */
static void add_diversion_header(pjsip_tx_data *tdata, struct ast_party_redirecting *data)
{
	static const pj_str_t reason_name = { "reason", 6 };

	pjsip_fromto_hdr *hdr;
	pjsip_name_addr *name_addr;
	pjsip_param *param;
	pjsip_fromto_hdr *old_hdr;
	const char *reason_str;
	const char *quote_str;
	char *reason_buf;
	pjsip_uri *base;

	struct ast_party_id *id = NULL;
	if (tdata->msg->type == PJSIP_REQUEST_MSG) {
		id = &data->from;
	} else {
		/* In responses indicate the new destination */
		id = &data->to;
	}

	base = PJSIP_MSG_FROM_HDR(tdata->msg)->uri;

	if (!id->number.valid || ast_strlen_zero(id->number.str)) {
		return;
	}

	hdr = pjsip_from_hdr_create(tdata->pool);
	hdr->type = PJSIP_H_OTHER;
	hdr->sname = hdr->name = diversion_name;

	name_addr = pjsip_uri_clone(tdata->pool, base);

	pj_strdup2(tdata->pool, &name_addr->display, id->name.str);
	pj_strdup2(tdata->pool, (pj_str_t *)ast_sip_pjsip_uri_get_username(name_addr->uri), id->number.str);

	param = PJ_POOL_ALLOC_T(tdata->pool, pjsip_param);
	param->name = reason_name;

	reason_str = reason_code_to_str(&data->reason);

	/* Reason is either already quoted or it is a token to not need quotes added. */
	quote_str = *reason_str == '\"' || sip_is_token(reason_str) ? "" : "\"";

	reason_buf = pj_pool_alloc(tdata->pool, strlen(reason_str) + 3);
	sprintf(reason_buf, "%s%s%s", quote_str, reason_str, quote_str);/* Safe */

	param->value = pj_str(reason_buf);

	pj_list_insert_before(&hdr->other_param, param);

	hdr->uri = (pjsip_uri *) name_addr;
	old_hdr = pjsip_msg_find_hdr_by_name(tdata->msg, &diversion_name, NULL);
	if (old_hdr) {
		pj_list_erase(old_hdr);
	}
	pjsip_msg_add_hdr(tdata->msg, (pjsip_hdr *)hdr);
}

/*!
 * \internal
 * \brief Adds history-info header information to an outbound SIP message
 *
 * \param tdata The outbound message
 * \param data The redirecting data used to fill parts of the history-info header
 */
static void add_history_info_header(pjsip_tx_data *tdata, struct ast_party_redirecting *data)
{
	static const pj_str_t index_name = { "index", 5 };
	static const pj_str_t cause_name = { "cause", 5 };
	static const pj_str_t first_index = { "1", 1 };
	static const pj_str_t last_index = { "1.1", 3 };

	pjsip_fromto_hdr *hdr;
	pjsip_name_addr *name_addr;
	pjsip_sip_uri *uri;
	pjsip_param *param;
	pjsip_fromto_hdr *old_hdr;
	unsigned int cause;
	char *cause_buf;

	struct ast_party_id *to = &data->to;
	struct ast_party_id *from = &data->from;

	pjsip_uri *base = PJSIP_MSG_TO_HDR(tdata->msg)->uri;


	hdr = pjsip_from_hdr_create(tdata->pool);
	hdr->type = PJSIP_H_OTHER;
	hdr->sname = hdr->name = history_info_name;

	name_addr = pjsip_uri_clone(tdata->pool, base);
	uri = pjsip_uri_get_uri(name_addr->uri);

	/* if no redirecting information, then TO is the original destination */
	if (from->number.valid && !ast_strlen_zero(from->number.str)) {
		pj_strdup2(tdata->pool, &name_addr->display, from->name.str);
		pj_strdup2(tdata->pool, &uri->user, from->number.str);
	}

	param = PJ_POOL_ALLOC_T(tdata->pool, pjsip_param);
	param->name = index_name;
	param->value = first_index;


	pj_list_insert_before(&hdr->other_param, param);
	hdr->uri = (pjsip_uri *) name_addr;

	while ((old_hdr = pjsip_msg_find_hdr_by_name(tdata->msg, &history_info_name, NULL)) != NULL) {
		pj_list_erase(old_hdr);
	}

	pjsip_msg_add_hdr(tdata->msg, (pjsip_hdr *)hdr);

	if (!to->number.valid || ast_strlen_zero(to->number.str)) {
		return;
	}

	hdr = pjsip_from_hdr_create(tdata->pool);
	hdr->type = PJSIP_H_OTHER;
	hdr->sname = hdr->name = history_info_name;

	name_addr = pjsip_uri_clone(tdata->pool, base);
	uri = pjsip_uri_get_uri(name_addr->uri);

	pj_strdup2(tdata->pool, &name_addr->display, to->name.str);
	pj_strdup2(tdata->pool, &uri->user, to->number.str);

	param = PJ_POOL_ALLOC_T(tdata->pool, pjsip_param);
	param->name = index_name;
	param->value = last_index;
	pj_list_insert_before(&hdr->other_param, param);

	param = PJ_POOL_ALLOC_T(tdata->pool, pjsip_param);
	param->name = cause_name;
	cause = reason_code_to_cause(&data->reason);
	cause_buf = pj_pool_alloc(tdata->pool, 4);
	snprintf(cause_buf, 4, "%ud", cause);
	param->value = pj_str(cause_buf);
	pj_list_insert_before(&uri->other_param, param);
	hdr->uri = (pjsip_uri *) name_addr;

	pjsip_msg_add_hdr(tdata->msg, (pjsip_hdr *)hdr);
}

static void get_redirecting_add_diversion(struct ast_sip_session *session, pjsip_tx_data *tdata)
{
	struct ast_party_redirecting *data;

	add_supported(tdata);

	if (session->channel && session->endpoint->id.send_diversion &&
	    (data = ast_channel_redirecting(session->channel))->count) {
		add_diversion_header(tdata, data);
	}
	if (session->channel && session->endpoint->id.send_history_info) {
		data = ast_channel_redirecting(session->channel);
		add_history_info_header(tdata, data);
	}
}

/*!
 * \internal
 * \brief Adds a diversion header to an outgoing INVITE request if
 *  redirecting information is available.
 *
 * \param session The session on which the INVITE request is to be sent
 * \param tdata The outbound INVITE request
 */
static void diversion_outgoing_request(struct ast_sip_session *session, pjsip_tx_data *tdata)
{
	get_redirecting_add_diversion(session, tdata);
}

/*!
 * \internal
 * \brief Adds a diversion header to an outgoing 3XX response
 *
 * \param session The session on which the INVITE response is to be sent
 * \param tdata The outbound INVITE response
 */
static void diversion_outgoing_response(struct ast_sip_session *session, pjsip_tx_data *tdata)
{
	struct pjsip_status_line status = tdata->msg->line.status;

	/* add to 302 and 181 */
	if (PJSIP_IS_STATUS_IN_CLASS(status.code, 300) || (status.code == 181)) {
        get_redirecting_add_diversion(session, tdata);
    }
}

static struct ast_sip_session_supplement diversion_supplement_media = {
	.method = "INVITE",
	/* this supplement needs to be called after caller id
           and after the channel has been created */
	.priority = AST_SIP_SUPPLEMENT_PRIORITY_CHANNEL + 100,
	.incoming_response = diversion_incoming_response_media,
	.response_priority = AST_SIP_SESSION_BEFORE_MEDIA,
};

static struct ast_sip_session_supplement diversion_supplement_redirecting = {
	.method = "INVITE",
	/* this supplement needs to be called after caller id
           and after the channel has been created */
	.priority = AST_SIP_SUPPLEMENT_PRIORITY_CHANNEL + 100,
	.incoming_request = diversion_incoming_request,
	.incoming_response = diversion_incoming_response_redirecting,
	.outgoing_request = diversion_outgoing_request,
	.outgoing_response = diversion_outgoing_response,
	.response_priority = AST_SIP_SESSION_BEFORE_REDIRECTING,
};

static int load_module(void)
{
	/* Because we are passing static memory to pjsip, we need to make sure it
	 * stays valid while we potentially have active sessions */
	ast_module_shutdown_ref(ast_module_info->self);
	ast_sip_session_register_supplement(&diversion_supplement_media);
	ast_sip_session_register_supplement(&diversion_supplement_redirecting);
	return AST_MODULE_LOAD_SUCCESS;
}

static int unload_module(void)
{
	ast_sip_session_unregister_supplement(&diversion_supplement_media);
	ast_sip_session_unregister_supplement(&diversion_supplement_redirecting);
	return 0;
}

AST_MODULE_INFO(ASTERISK_GPL_KEY, AST_MODFLAG_LOAD_ORDER, "PJSIP Add Diversion Header Support",
	.support_level = AST_MODULE_SUPPORT_CORE,
	.load = load_module,
	.unload = unload_module,
	.load_pri = AST_MODPRI_APP_DEPEND,
	.requires = "res_pjsip,res_pjsip_session",
);
