/*
* Asterisk -- An open source telephony toolkit.
*
* Copyright (C) 2013, Digium, Inc.
*
* Mark Michelson <mmichelson@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_sip</depend>
	<support_level>core</support_level>
 ***/

#include "asterisk.h"

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

#include "asterisk/res_sip.h"
#include "asterisk/res_sip_session.h"
#include "asterisk/datastore.h"
#include "asterisk/module.h"
#include "asterisk/logger.h"
#include "asterisk/res_sip.h"
#include "asterisk/astobj2.h"
#include "asterisk/lock.h"
#include "asterisk/uuid.h"
#include "asterisk/pbx.h"
#include "asterisk/taskprocessor.h"
#include "asterisk/causes.h"
#include "asterisk/sdp_srtp.h"
#include "asterisk/dsp.h"

#define SDP_HANDLER_BUCKETS 11

/* Some forward declarations */
static void handle_incoming_request(struct ast_sip_session *session, pjsip_rx_data *rdata);
static void handle_incoming_response(struct ast_sip_session *session, pjsip_rx_data *rdata);
static int handle_incoming(struct ast_sip_session *session, pjsip_rx_data *rdata);
static void handle_outgoing_request(struct ast_sip_session *session, pjsip_tx_data *tdata);
static void handle_outgoing_response(struct ast_sip_session *session, pjsip_tx_data *tdata);
static void handle_outgoing(struct ast_sip_session *session, pjsip_tx_data *tdata);

/*! \brief NAT hook for modifying outgoing messages with SDP */
static struct ast_sip_nat_hook *nat_hook;

/*!
 * \brief Registered SDP stream handlers
 *
 * This container is keyed on stream types. Each
 * object in the container is a linked list of
 * handlers for the stream type.
 */
static struct ao2_container *sdp_handlers;

/*!
 * These are the objects in the sdp_handlers container
 */
struct sdp_handler_list {
	/* The list of handlers to visit */
	AST_LIST_HEAD_NOLOCK(, ast_sip_session_sdp_handler) list;
	/* The handlers in this list handle streams of this type */
	char stream_type[1];
};

static struct pjmedia_sdp_session *create_local_sdp(pjsip_inv_session *inv, struct ast_sip_session *session, const pjmedia_sdp_session *offer);

static int sdp_handler_list_hash(const void *obj, int flags)
{
	const struct sdp_handler_list *handler_list = obj;
	const char *stream_type = flags & OBJ_KEY ? obj : handler_list->stream_type;

	return ast_str_hash(stream_type);
}

static int sdp_handler_list_cmp(void *obj, void *arg, int flags)
{
	struct sdp_handler_list *handler_list1 = obj;
	struct sdp_handler_list *handler_list2 = arg;
	const char *stream_type2 = flags & OBJ_KEY ? arg : handler_list2->stream_type;

	return strcmp(handler_list1->stream_type, stream_type2) ? 0 : CMP_MATCH | CMP_STOP;
}

static int session_media_hash(const void *obj, int flags)
{
	const struct ast_sip_session_media *session_media = obj;
	const char *stream_type = flags & OBJ_KEY ? obj : session_media->stream_type;

	return ast_str_hash(stream_type);
}

static int session_media_cmp(void *obj, void *arg, int flags)
{
	struct ast_sip_session_media *session_media1 = obj;
	struct ast_sip_session_media *session_media2 = arg;
	const char *stream_type2 = flags & OBJ_KEY ? arg : session_media2->stream_type;

	return strcmp(session_media1->stream_type, stream_type2) ? 0 : CMP_MATCH | CMP_STOP;
}

int ast_sip_session_register_sdp_handler(struct ast_sip_session_sdp_handler *handler, const char *stream_type)
{
	RAII_VAR(struct sdp_handler_list *, handler_list,
			ao2_find(sdp_handlers, stream_type, OBJ_KEY), ao2_cleanup);
	SCOPED_AO2LOCK(lock, sdp_handlers);

	if (handler_list) {
		struct ast_sip_session_sdp_handler *iter;
		/* Check if this handler is already registered for this stream type */
		AST_LIST_TRAVERSE(&handler_list->list, iter, next) {
			if (!strcmp(iter->id, handler->id)) {
				ast_log(LOG_WARNING, "Handler '%s' already registered for stream type '%s'.\n", handler->id, stream_type);
				return -1;
			}
		}
		AST_LIST_INSERT_TAIL(&handler_list->list, handler, next);
		ast_debug(1, "Registered SDP stream handler '%s' for stream type '%s'\n", handler->id, stream_type); 
		ast_module_ref(ast_module_info->self);
		return 0;
	}

	/* No stream of this type has been registered yet, so we need to create a new list */
	handler_list = ao2_alloc(sizeof(*handler_list) + strlen(stream_type), NULL);
	if (!handler_list) {
		return -1;
	}
	/* Safe use of strcpy */
	strcpy(handler_list->stream_type, stream_type);
	AST_LIST_HEAD_INIT_NOLOCK(&handler_list->list);
	AST_LIST_INSERT_TAIL(&handler_list->list, handler, next);
	if (!ao2_link(sdp_handlers, handler_list)) {
		return -1;
	}
	ast_debug(1, "Registered SDP stream handler '%s' for stream type '%s'\n", handler->id, stream_type); 
	ast_module_ref(ast_module_info->self);
	return 0;
}

static int remove_handler(void *obj, void *arg, void *data, int flags)
{
	struct sdp_handler_list *handler_list = obj;
	struct ast_sip_session_sdp_handler *handler = data;
	struct ast_sip_session_sdp_handler *iter;
	const char *stream_type = arg;

	AST_LIST_TRAVERSE_SAFE_BEGIN(&handler_list->list, iter, next) {
		if (!strcmp(iter->id, handler->id)) {
			AST_LIST_REMOVE_CURRENT(next);
			ast_debug(1, "Unregistered SDP stream handler '%s' for stream type '%s'\n", handler->id, stream_type);
			ast_module_unref(ast_module_info->self);
		}
	}
	AST_LIST_TRAVERSE_SAFE_END;

	if (AST_LIST_EMPTY(&handler_list->list)) {
		ast_debug(3, "No more handlers exist for stream type '%s'\n", stream_type);
		return CMP_MATCH;
	} else {
		return CMP_STOP;
	}
}

void ast_sip_session_unregister_sdp_handler(struct ast_sip_session_sdp_handler *handler, const char *stream_type)
{
	ao2_callback_data(sdp_handlers, OBJ_KEY | OBJ_UNLINK | OBJ_NODATA, remove_handler, (void *)stream_type, handler);
}

static int validate_port_hash(const void *obj, int flags)
{
	const int *port = obj;
	return *port;
}

static int validate_port_cmp(void *obj, void *arg, int flags)
{
	int *port1 = obj;
	int *port2 = arg;

	return *port1 == *port2 ? CMP_MATCH | CMP_STOP : 0;
}

struct bundle_assoc {
	int port;
	char tag[1];
};

static int bundle_assoc_hash(const void *obj, int flags)
{
	const struct bundle_assoc *assoc = obj;
	const char *tag = flags & OBJ_KEY ? obj : assoc->tag;

	return ast_str_hash(tag);
}

static int bundle_assoc_cmp(void *obj, void *arg, int flags)
{
	struct bundle_assoc *assoc1 = obj;
	struct bundle_assoc *assoc2 = arg;
	const char *tag2 = flags & OBJ_KEY ? arg : assoc2->tag;

	return strcmp(assoc1->tag, tag2) ? 0 : CMP_MATCH | CMP_STOP;
}

/* return must be ast_freed */
static pjmedia_sdp_attr *media_get_mid(pjmedia_sdp_media *media)
{
	pjmedia_sdp_attr *attr = pjmedia_sdp_media_find_attr2(media, "mid", NULL);
	if (!attr) {
		return NULL;
	}

	return attr;
}

static int get_bundle_port(const pjmedia_sdp_session *sdp, const char *mid)
{
	int i;
	for (i = 0; i < sdp->media_count; ++i) {
		pjmedia_sdp_attr *mid_attr = media_get_mid(sdp->media[i]);
		if (mid_attr && !pj_strcmp2(&mid_attr->value, mid)) {
			return sdp->media[i]->desc.port;
		}
	}

	return -1;
}

static int validate_incoming_sdp(const pjmedia_sdp_session *sdp)
{
	int i;
	RAII_VAR(struct ao2_container *, portlist, ao2_container_alloc(5, validate_port_hash, validate_port_cmp), ao2_cleanup);
	RAII_VAR(struct ao2_container *, bundle_assoc_list, ao2_container_alloc(5, bundle_assoc_hash, bundle_assoc_cmp), ao2_cleanup);

	/* check for bundles (for websocket RTP multiplexing, there can be more than one) */
	for (i = 0; i < sdp->attr_count; ++i) {
		char *bundle_list;
		int bundle_port = 0;
		if (pj_stricmp2(&sdp->attr[i]->name, "group")) {
			continue;
		}

		/* check to see if this group is a bundle */
		if (7 >= sdp->attr[i]->value.slen || pj_strnicmp2(&sdp->attr[i]->value, "bundle ", 7)) {
			continue;
		}

		bundle_list = ast_alloca(sdp->attr[i]->value.slen - 6);
		strncpy(bundle_list, sdp->attr[i]->value.ptr + 7, sdp->attr[i]->value.slen - 7);
		bundle_list[sdp->attr[i]->value.slen - 7] = '\0';
		while (bundle_list) {
			char *item;
			RAII_VAR(struct bundle_assoc *, assoc, NULL, ao2_cleanup);
			item = strsep(&bundle_list, " ,");
			if (!bundle_port) {
				RAII_VAR(int *, port, ao2_alloc(sizeof(int), NULL), ao2_cleanup);
				RAII_VAR(int *, port_match, NULL, ao2_cleanup);
				bundle_port = get_bundle_port(sdp, item);
				if (bundle_port < 0) {
					return -1;
				}
				port_match = ao2_find(portlist, &bundle_port, OBJ_KEY);
				if (port_match) {
					/* bundle port aready consumed by a different bundle */
					return -1;
				}
				*port = bundle_port;
				ao2_link(portlist, port);
			}
			assoc = ao2_alloc(sizeof(*assoc) + strlen(item), NULL);
			if (!assoc) {
				return -1;
			}

			/* safe use of strcpy */
			strcpy(assoc->tag, item);
			assoc->port = bundle_port;
			ao2_link(bundle_assoc_list, assoc);
		}
	}

	/* validate all streams */
	for (i = 0; i < sdp->media_count; ++i) {
		RAII_VAR(int *, port, ao2_alloc(sizeof(int), NULL), ao2_cleanup);
		RAII_VAR(int *, port_match, NULL, ao2_cleanup);
		RAII_VAR(int *, bundle_match, NULL, ao2_cleanup);
		*port = sdp->media[i]->desc.port;
		port_match = ao2_find(portlist, port, OBJ_KEY);
		if (port_match) {
			RAII_VAR(struct bundle_assoc *, assoc, NULL, ao2_cleanup);
			pjmedia_sdp_attr *mid = media_get_mid(sdp->media[i]);
			char *mid_val;

			if (!mid) {
				/* not part of a bundle */
				return -1;
			}

			mid_val = ast_alloca(mid->value.slen + 1);
			strncpy(mid_val, mid->value.ptr, mid->value.slen);
			mid_val[mid->value.slen] = '\0';

			assoc = ao2_find(bundle_assoc_list, mid_val, OBJ_KEY);
			if (!assoc || assoc->port != *port) {
				/* This port already exists elsewhere in the SDP
				 * and is not an appropriate bundle port, fail
				 * catastrophically */
				return -1;
			}
		}
		ao2_link(portlist, port);
	}
	return 0;
}

static int handle_incoming_sdp(struct ast_sip_session *session, const pjmedia_sdp_session *sdp)
{
	int i;
	if (validate_incoming_sdp(sdp)) {
		return -1;
	}

	for (i = 0; i < sdp->media_count; ++i) {
		/* See if there are registered handlers for this media stream type */
		char media[20];
		struct ast_sip_session_sdp_handler *handler;
		RAII_VAR(struct sdp_handler_list *, handler_list, NULL, ao2_cleanup);
		RAII_VAR(struct ast_sip_session_media *, session_media, NULL, ao2_cleanup);

		/* We need a null-terminated version of the media string */
		ast_copy_pj_str(media, &sdp->media[i]->desc.media, sizeof(media));

		session_media = ao2_find(session->media, media, OBJ_KEY);
		if (!session_media) {
			/* if the session_media doesn't exist, there weren't
			 * any handlers at the time of its creation */
			continue;
		}

		if (session_media->handler) {
			int res;
			handler = session_media->handler;
			res = handler->negotiate_incoming_sdp_stream(
				session, session_media, sdp, sdp->media[i]);
			if (res <= 0) {
				/* Catastrophic failure or ignored by assigned handler. Abort! */
				return -1;
			}
			if (res > 0) {
				/* Handled by this handler. Move to the next stream */
				continue;
			}
		}

		handler_list = ao2_find(sdp_handlers, media, OBJ_KEY);
		if (!handler_list) {
			ast_debug(1, "No registered SDP handlers for media type '%s'\n", media);
			continue;
		}
		AST_LIST_TRAVERSE(&handler_list->list, handler, next) {
			int res;
			if (session_media->handler) {
				/* There is only one slot for this stream type and it has already been claimed
				 * so it will go unhandled */
				break;
			}
			res = handler->negotiate_incoming_sdp_stream(session, session_media, sdp, sdp->media[i]);
			if (res < 0) {
				/* Catastrophic failure. Abort! */
				return -1;
			}
			if (res > 0) {
				/* Handled by this handler. Move to the next stream */
				session_media->handler = handler;
				break;
			}
		}
	}
	return 0;
}

struct handle_negotiated_sdp_cb {
	struct ast_sip_session *session;
	const pjmedia_sdp_session *local;
	const pjmedia_sdp_session *remote;
};

static int handle_negotiated_sdp_session_media(void *obj, void *arg, int flags)
{
	struct ast_sip_session_media *session_media = obj;
	struct handle_negotiated_sdp_cb *callback_data = arg;
	struct ast_sip_session *session = callback_data->session;
	const pjmedia_sdp_session *local = callback_data->local;
	const pjmedia_sdp_session *remote = callback_data->remote;
	int i;

	for (i = 0; i < local->media_count; ++i) {
		/* See if there are registered handlers for this media stream type */
		char media[20];
		struct ast_sip_session_sdp_handler *handler;
		RAII_VAR(struct sdp_handler_list *, handler_list, NULL, ao2_cleanup);

		/* We need a null-terminated version of the media string */
		ast_copy_pj_str(media, &local->media[i]->desc.media, sizeof(media));

		/* stream type doesn't match the one we're looking to fill */
		if (strcasecmp(session_media->stream_type, media)) {
			continue;
		}

		handler = session_media->handler;
		if (handler) {
			int res = handler->apply_negotiated_sdp_stream(session, session_media, local, local->media[i], remote, remote->media[i]);
			if (res >= 0) {
				return CMP_MATCH;
			}
			return 0;
		}

		handler_list = ao2_find(sdp_handlers, media, OBJ_KEY);
		if (!handler_list) {
			ast_debug(1, "No registered SDP handlers for media type '%s'\n", media);
			continue;
		}
		AST_LIST_TRAVERSE(&handler_list->list, handler, next) {
			int res = handler->apply_negotiated_sdp_stream(session, session_media, local, local->media[i], remote, remote->media[i]);
			if (res < 0) {
				/* Catastrophic failure. Abort! */
				return 0;
			}
			if (res > 0) {
				/* Handled by this handler. Move to the next stream */
				session_media->handler = handler;
				return CMP_MATCH;
			}
		}
	}
	return CMP_MATCH;
}

static int handle_negotiated_sdp(struct ast_sip_session *session, const pjmedia_sdp_session *local, const pjmedia_sdp_session *remote)
{
	RAII_VAR(struct ao2_iterator *, successful, NULL, ao2_iterator_cleanup);
	struct handle_negotiated_sdp_cb callback_data = {
		.session = session,
		.local = local,
		.remote = remote,
	};

	successful = ao2_callback(session->media, OBJ_MULTIPLE, handle_negotiated_sdp_session_media, &callback_data);
	if (successful && ao2_container_count(successful->c) == ao2_container_count(session->media)) {
		/* Nothing experienced a catastrophic failure */
		return 0;
	}
	return -1;
}

AST_RWLIST_HEAD_STATIC(session_supplements, ast_sip_session_supplement);

int ast_sip_session_register_supplement(struct ast_sip_session_supplement *supplement)
{
	struct ast_sip_session_supplement *iter;
	int inserted = 0;
	SCOPED_LOCK(lock, &session_supplements, AST_RWLIST_WRLOCK, AST_RWLIST_UNLOCK);

	AST_RWLIST_TRAVERSE_SAFE_BEGIN(&session_supplements, iter, next) {
		if (iter->priority > supplement->priority) {
			AST_RWLIST_INSERT_BEFORE_CURRENT(supplement, next);
			inserted = 1;
			break;
		}
	}
	AST_RWLIST_TRAVERSE_SAFE_END;

	if (!inserted) {
		AST_RWLIST_INSERT_TAIL(&session_supplements, supplement, next);
	}
	ast_module_ref(ast_module_info->self);
	return 0;
}

void ast_sip_session_unregister_supplement(struct ast_sip_session_supplement *supplement)
{
	struct ast_sip_session_supplement *iter;
	SCOPED_LOCK(lock, &session_supplements, AST_RWLIST_WRLOCK, AST_RWLIST_UNLOCK);
	AST_RWLIST_TRAVERSE_SAFE_BEGIN(&session_supplements, iter, next) {
		if (supplement == iter) {
			AST_RWLIST_REMOVE_CURRENT(next);
			ast_module_unref(ast_module_info->self);
			break;
		}
	}
	AST_RWLIST_TRAVERSE_SAFE_END;
}

static struct ast_sip_session_supplement *supplement_dup(const struct ast_sip_session_supplement *src)
{
	struct ast_sip_session_supplement *dst = ast_calloc(1, sizeof(*dst));
	if (!dst) {
		return NULL;
	}
	/* Will need to revisit if shallow copy becomes an issue */
	*dst = *src;
	return dst;
}

#define DATASTORE_BUCKETS 53
#define MEDIA_BUCKETS 7

static void session_datastore_destroy(void *obj)
{
	struct ast_datastore *datastore = obj;

	/* Using the destroy function (if present) destroy the data */
	if (datastore->info->destroy != NULL && datastore->data != NULL) {
		datastore->info->destroy(datastore->data);
		datastore->data = NULL;
	}

	ast_free((void *) datastore->uid);
	datastore->uid = NULL;
}

struct ast_datastore *ast_sip_session_alloc_datastore(const struct ast_datastore_info *info, const char *uid)
{
	RAII_VAR(struct ast_datastore *, datastore, NULL, ao2_cleanup);
	const char *uid_ptr = uid;

	if (!info) {
		return NULL;
	}

	datastore = ao2_alloc(sizeof(*datastore), session_datastore_destroy);
	if (!datastore) {
		return NULL;
	}

	datastore->info = info;
	if (ast_strlen_zero(uid)) {
		/* They didn't provide an ID so we'll provide one ourself */
		struct ast_uuid *uuid = ast_uuid_generate();
		char uuid_buf[AST_UUID_STR_LEN];
		if (!uuid) {
			return NULL;
		}
		uid_ptr = ast_uuid_to_str(uuid, uuid_buf, sizeof(uuid_buf));
		ast_free(uuid);
	}

	datastore->uid = ast_strdup(uid_ptr);
	if (!datastore->uid) {
		return NULL;
	}

	ao2_ref(datastore, +1);
	return datastore;
}

int ast_sip_session_add_datastore(struct ast_sip_session *session, struct ast_datastore *datastore)
{
	ast_assert(datastore != NULL);
	ast_assert(datastore->info != NULL);
	ast_assert(ast_strlen_zero(datastore->uid) == 0);

	if (!ao2_link(session->datastores, datastore)) {
		return -1;
	}
	return 0;
}

struct ast_datastore *ast_sip_session_get_datastore(struct ast_sip_session *session, const char *name)
{
	return ao2_find(session->datastores, name, OBJ_KEY);
}

void ast_sip_session_remove_datastore(struct ast_sip_session *session, const char *name)
{
	ao2_callback(session->datastores, OBJ_KEY | OBJ_UNLINK | OBJ_NODATA, NULL, (void *) name);
}

int ast_sip_session_get_identity(struct pjsip_rx_data *rdata, struct ast_party_id *id)
{
	/* XXX STUB
	 * This is low-priority as far as getting SIP working is concerned, so this
	 * will be addressed later.
	 *
	 * The idea here will be that the rdata will be examined for headers such as
	 * P-Asserted-Identity, Remote-Party-ID, and From in order to determine Identity
	 * information.
	 *
	 * For reference, Asterisk SCF code does something very similar to this, except in
	 * C++ and using its version of the ast_party_id struct, so using it as a basis
	 * would be a smart idea here.
	 */
	return 0;
}

/*!
 * \brief Structure used for sending delayed requests
 *
 * Requests are typically delayed because the current transaction
 * state of an INVITE. Once the pending INVITE transaction terminates,
 * the delayed request will be sent
 */
struct ast_sip_session_delayed_request {
	/*! Method of the request */
	char method[15];
	/*! Callback to call when the delayed request is created. */
	ast_sip_session_request_creation_cb on_request_creation;
	/*! Callback to call when the delayed request receives a response */
	ast_sip_session_response_cb on_response;
	/*! Request to send */
	pjsip_tx_data *tdata;
	AST_LIST_ENTRY(ast_sip_session_delayed_request) next;
};

static struct ast_sip_session_delayed_request *delayed_request_alloc(const char *method,
		ast_sip_session_request_creation_cb on_request_creation,
		ast_sip_session_response_cb on_response,
		pjsip_tx_data *tdata)
{
	struct ast_sip_session_delayed_request *delay = ast_calloc(1, sizeof(*delay));
	if (!delay) {
		return NULL;
	}
	ast_copy_string(delay->method, method, sizeof(delay->method));
	delay->on_request_creation = on_request_creation;
	delay->on_response = on_response;
	delay->tdata = tdata;
	return delay;
}

static int send_delayed_request(struct ast_sip_session *session, struct ast_sip_session_delayed_request *delay)
{
	ast_debug(3, "Sending delayed %s request to %s\n", delay->method, ast_sorcery_object_get_id(session->endpoint));

	if (delay->tdata) {
		ast_sip_session_send_request_with_cb(session, delay->tdata, delay->on_response);
		return 0;
	}

	if (!strcmp(delay->method, "INVITE")) {
		ast_sip_session_refresh(session, delay->on_request_creation,
				delay->on_response, AST_SIP_SESSION_REFRESH_METHOD_INVITE, 1);
	} else if (!strcmp(delay->method, "UPDATE")) {
		ast_sip_session_refresh(session, delay->on_request_creation,
				delay->on_response, AST_SIP_SESSION_REFRESH_METHOD_UPDATE, 1);
	} else {
		ast_log(LOG_WARNING, "Unexpected delayed %s request with no existing request structure\n", delay->method);
		return -1;
	}
	return 0;
}

static int queued_delayed_request_send(void *data)
{
	RAII_VAR(struct ast_sip_session *, session, data, ao2_cleanup);
	RAII_VAR(struct ast_sip_session_delayed_request *, delay, NULL, ast_free_ptr);

	delay = AST_LIST_REMOVE_HEAD(&session->delayed_requests, next);
	if (!delay) {
		return 0;
	}

	return send_delayed_request(session, delay);
}

static void queue_delayed_request(struct ast_sip_session *session)
{
	if (AST_LIST_EMPTY(&session->delayed_requests)) {
		/* No delayed request to send, so just return */
		return;
	}

	ast_debug(3, "Queuing delayed request to run for %s\n",
			ast_sorcery_object_get_id(session->endpoint));

	ao2_ref(session, +1);
	ast_sip_push_task(session->serializer, queued_delayed_request_send, session);
}

static int delay_request(struct ast_sip_session *session, ast_sip_session_request_creation_cb on_request,
		ast_sip_session_response_cb on_response, const char *method, pjsip_tx_data *tdata)
{
	struct ast_sip_session_delayed_request *delay = delayed_request_alloc(method,
			on_request, on_response, tdata);

	if (!delay) {
		return -1;
	}

	AST_LIST_INSERT_TAIL(&session->delayed_requests, delay, next);
	return 0;
}

static pjmedia_sdp_session *generate_session_refresh_sdp(struct ast_sip_session *session)
{
	pjsip_inv_session *inv_session = session->inv_session;
	const pjmedia_sdp_session *previous_sdp;

	if (pjmedia_sdp_neg_was_answer_remote(inv_session->neg)) {
		pjmedia_sdp_neg_get_active_remote(inv_session->neg, &previous_sdp);
	} else {
		pjmedia_sdp_neg_get_active_local(inv_session->neg, &previous_sdp);
	}
	return create_local_sdp(inv_session, session, previous_sdp);
}

int ast_sip_session_refresh(struct ast_sip_session *session,
		ast_sip_session_request_creation_cb on_request_creation, ast_sip_session_response_cb on_response,
		enum ast_sip_session_refresh_method method, int generate_new_sdp)
{
	pjsip_inv_session *inv_session = session->inv_session;
	pjmedia_sdp_session *new_sdp = NULL;
	pjsip_tx_data *tdata;

	if (inv_session->state == PJSIP_INV_STATE_DISCONNECTED) {
		/* Don't try to do anything with a hung-up call */
		ast_debug(3, "Not sending reinvite to %s because of disconnected state...\n",
				ast_sorcery_object_get_id(session->endpoint));
		return 0;
	}

	if ((method == AST_SIP_SESSION_REFRESH_METHOD_INVITE) && inv_session->invite_tsx) {
		/* We can't send a reinvite yet, so delay it */
		ast_debug(3, "Delaying sending reinvite to %s because of outstanding transaction...\n",
				ast_sorcery_object_get_id(session->endpoint));
		return delay_request(session, on_request_creation, on_response, "INVITE", NULL);
	}

	if (generate_new_sdp) {
		new_sdp = generate_session_refresh_sdp(session);
		if (!new_sdp) {
			ast_log(LOG_ERROR, "Failed to generate session refresh SDP. Not sending session refresh\n");
			return -1;
		}
	}

	if (method == AST_SIP_SESSION_REFRESH_METHOD_INVITE) {
		if (pjsip_inv_reinvite(inv_session, NULL, new_sdp, &tdata)) {
			ast_log(LOG_WARNING, "Failed to create reinvite properly.\n");
			return -1;
		}
	} else if (pjsip_inv_update(inv_session, NULL, new_sdp, &tdata)) {
		ast_log(LOG_WARNING, "Failed to create UPDATE properly.\n");
		return -1;
	}
	if (on_request_creation) {
		if (on_request_creation(session, tdata)) {
			return -1;
		}
	}
	ast_sip_session_send_request_with_cb(session, tdata, on_response);
	return 0;
}

void ast_sip_session_send_response(struct ast_sip_session *session, pjsip_tx_data *tdata)
{
	handle_outgoing_response(session, tdata);
	pjsip_inv_send_msg(session->inv_session, tdata);
	return;
}

static pj_status_t session_load(pjsip_endpoint *endpt);
static pj_status_t session_start(void);
static pj_status_t session_stop(void);
static pj_status_t session_unload(void);
static pj_bool_t session_on_rx_request(pjsip_rx_data *rdata);

static pjsip_module session_module = {
	.name = {"Session Module", 14},
	.priority = PJSIP_MOD_PRIORITY_APPLICATION,
	.load = session_load,
	.unload = session_unload,
	.start = session_start,
	.stop = session_stop,
	.on_rx_request = session_on_rx_request,
};

void ast_sip_session_send_request_with_cb(struct ast_sip_session *session, pjsip_tx_data *tdata,
		ast_sip_session_response_cb on_response)
{
	pjsip_inv_session *inv_session = session->inv_session;

	if (inv_session->state == PJSIP_INV_STATE_DISCONNECTED) {
		/* Don't try to do anything with a hung-up call */
		return;
	}

	tdata->mod_data[session_module.id] = on_response;
	handle_outgoing_request(session, tdata);
	pjsip_inv_send_msg(session->inv_session, tdata);
	return;
}

void ast_sip_session_send_request(struct ast_sip_session *session, pjsip_tx_data *tdata)
{
	ast_sip_session_send_request_with_cb(session, tdata, NULL);
}

int ast_sip_session_create_invite(struct ast_sip_session *session, pjsip_tx_data **tdata)
{
	pjmedia_sdp_session *offer;

	if (!(offer = create_local_sdp(session->inv_session, session, NULL))) {
		pjsip_inv_terminate(session->inv_session, 500, PJ_FALSE);
		return -1;
	}

	pjsip_inv_set_local_sdp(session->inv_session, offer);
	pjmedia_sdp_neg_set_prefer_remote_codec_order(session->inv_session->neg, PJ_FALSE);
	if (pjsip_inv_invite(session->inv_session, tdata) != PJ_SUCCESS) {
		return -1;
	}
	return 0;
}

/*!
 * \brief Called when the PJSIP core loads us
 *
 * Since we already have Asterisk's fine module load/unload framework
 * in use, we don't need to do anything special here.
 */
static pj_status_t session_load(pjsip_endpoint *endpt)
{
	return PJ_SUCCESS;
}

/*!
 * \brief Called when the PJSIP core starts us
 *
 * Since we already have Asterisk's fine module load/unload framework
 * in use, we don't need to do anything special here.
 */
static pj_status_t session_start(void)
{
	return PJ_SUCCESS;
}

/*!
 * \brief Called when the PJSIP core stops us
 *
 * Since we already have Asterisk's fine module load/unload framework
 * in use, we don't need to do anything special here.
 */
static pj_status_t session_stop(void)
{
	return PJ_SUCCESS;
}

/*!
 * \brief Called when the PJSIP core unloads us
 *
 * Since we already have Asterisk's fine module load/unload framework
 * in use, we don't need to do anything special here.
 */
static pj_status_t session_unload(void)
{
	return PJ_SUCCESS;
}

static int datastore_hash(const void *obj, int flags)
{
	const struct ast_datastore *datastore = obj;
	const char *uid = flags & OBJ_KEY ? obj : datastore->uid;

	ast_assert(uid != NULL);

	return ast_str_hash(uid);
}

static int datastore_cmp(void *obj, void *arg, int flags)
{
	const struct ast_datastore *datastore1 = obj;
	const struct ast_datastore *datastore2 = arg;
	const char *uid2 = flags & OBJ_KEY ? arg : datastore2->uid;

	ast_assert(datastore1->uid != NULL);
	ast_assert(uid2 != NULL);

	return strcmp(datastore1->uid, uid2) ? 0 : CMP_MATCH | CMP_STOP;
}

static void session_media_dtor(void *obj)
{
	struct ast_sip_session_media *session_media = obj;
	if (session_media->handler) {
		session_media->handler->stream_destroy(session_media);
	}
	if (session_media->srtp) {
		ast_sdp_srtp_destroy(session_media->srtp);
	}
}

static void session_destructor(void *obj)
{
	struct ast_sip_session *session = obj;
	struct ast_sip_session_supplement *supplement;
	struct ast_sip_session_delayed_request *delay;

	ast_debug(3, "Destroying SIP session with endpoint %s\n",
			ast_sorcery_object_get_id(session->endpoint));

	while ((supplement = AST_LIST_REMOVE_HEAD(&session->supplements, next))) {
		if (supplement->session_destroy) {
			supplement->session_destroy(session);
		}
		ast_free(supplement);
	}

	ast_taskprocessor_unreference(session->serializer);
	ao2_cleanup(session->datastores);
	ao2_cleanup(session->media);
	AST_LIST_HEAD_DESTROY(&session->supplements);
	while ((delay = AST_LIST_REMOVE_HEAD(&session->delayed_requests, next))) {
		ast_free(delay);
	}
	ast_party_id_free(&session->id);
	ao2_cleanup(session->endpoint);
	ast_format_cap_destroy(session->req_caps);

	if (session->dsp) {
		ast_dsp_free(session->dsp);
	}

	if (session->inv_session) {
		pjsip_dlg_dec_session(session->inv_session->dlg, &session_module);
	}
}

static int add_supplements(struct ast_sip_session *session)
{
	struct ast_sip_session_supplement *iter;
	SCOPED_LOCK(lock, &session_supplements, AST_RWLIST_RDLOCK, AST_RWLIST_UNLOCK);

	AST_RWLIST_TRAVERSE(&session_supplements, iter, next) {
		struct ast_sip_session_supplement *copy = supplement_dup(iter);
		if (!copy) {
			return -1;
		}
		AST_LIST_INSERT_TAIL(&session->supplements, copy, next);
	}
	return 0;
}

static int add_session_media(void *obj, void *arg, int flags)
{
	struct sdp_handler_list *handler_list = obj;
	struct ast_sip_session * session = arg;
	RAII_VAR(struct ast_sip_session_media *, session_media, NULL, ao2_cleanup);
	session_media = ao2_alloc(sizeof(*session_media) + strlen(handler_list->stream_type), session_media_dtor);
	if (!session_media) {
		return CMP_STOP;
	}
	/* Safe use of strcpy */
	strcpy(session_media->stream_type, handler_list->stream_type);
	ao2_link(session->media, session_media);
	return 0;
}

struct ast_sip_session *ast_sip_session_alloc(struct ast_sip_endpoint *endpoint, pjsip_inv_session *inv_session)
{
	RAII_VAR(struct ast_sip_session *, session, ao2_alloc(sizeof(*session), session_destructor), ao2_cleanup);
	struct ast_sip_session_supplement *iter;
	if (!session) {
		return NULL;
	}
	AST_LIST_HEAD_INIT(&session->supplements);
	session->datastores = ao2_container_alloc(DATASTORE_BUCKETS, datastore_hash, datastore_cmp);
	if (!session->datastores) {
		return NULL;
	}

	session->media = ao2_container_alloc(MEDIA_BUCKETS, session_media_hash, session_media_cmp);
	if (!session->media) {
		return NULL;
	}
	/* fill session->media with available types */
	ao2_callback(sdp_handlers, OBJ_NODATA, add_session_media, session);

	session->serializer = ast_sip_create_serializer();
	if (!session->serializer) {
		return NULL;
	}
	ast_sip_dialog_set_serializer(inv_session->dlg, session->serializer);
	ast_sip_dialog_set_endpoint(inv_session->dlg, endpoint);
	pjsip_dlg_inc_session(inv_session->dlg, &session_module);
	ao2_ref(endpoint, +1);
	inv_session->mod_data[session_module.id] = session;
	session->endpoint = endpoint;
	session->inv_session = inv_session;
	session->req_caps = ast_format_cap_alloc_nolock();

	if (endpoint->dtmf == AST_SIP_DTMF_INBAND) {
		if (!(session->dsp = ast_dsp_new())) {
			return NULL;
		}

		ast_dsp_set_features(session->dsp, DSP_FEATURE_DIGIT_DETECT);
	}

	if (add_supplements(session)) {
		return NULL;
	}
	AST_LIST_TRAVERSE(&session->supplements, iter, next) {
		if (iter->session_begin) {
			iter->session_begin(session);
		}
	}
	session->direct_media_cap = ast_format_cap_alloc_nolock();
	AST_LIST_HEAD_INIT_NOLOCK(&session->delayed_requests);
	ast_party_id_init(&session->id);
	ao2_ref(session, +1);
	return session;
}

static int session_outbound_auth(pjsip_dialog *dlg, pjsip_tx_data *tdata, void *user_data)
{
	pjsip_inv_session *inv = pjsip_dlg_get_inv_session(dlg);
	struct ast_sip_session *session = inv->mod_data[session_module.id];

	if (inv->state < PJSIP_INV_STATE_CONFIRMED && tdata->msg->line.req.method.id == PJSIP_INVITE_METHOD) {
		pjsip_inv_uac_restart(inv, PJ_TRUE);
	}
	ast_sip_session_send_request(session, tdata);
	return 0;
}

struct ast_sip_session *ast_sip_session_create_outgoing(struct ast_sip_endpoint *endpoint, const char *location, const char *request_user, struct ast_format_cap *req_caps)
{
	const char *uri = NULL;
	RAII_VAR(struct ast_sip_contact *, contact, NULL, ao2_cleanup);
	pjsip_timer_setting timer;
	pjsip_dialog *dlg;
	struct pjsip_inv_session *inv_session;
	RAII_VAR(struct ast_sip_session *, session, NULL, ao2_cleanup);

	/* If no location has been provided use the AOR list from the endpoint itself */
	location = S_OR(location, endpoint->aors);

	contact = ast_sip_location_retrieve_contact_from_aor_list(location);
	if (!contact || ast_strlen_zero(contact->uri)) {
		uri = location;
	} else {
		uri = contact->uri;
	}

	/* If we still have no URI to dial fail to create the session */
	if (ast_strlen_zero(uri)) {
		return NULL;
	}

	if (!(dlg = ast_sip_create_dialog(endpoint, uri, request_user))) {
		return NULL;
	}

	if (ast_sip_dialog_setup_outbound_authentication(dlg, endpoint, session_outbound_auth, NULL)) {
		pjsip_dlg_terminate(dlg);
		return NULL;
	}

	if (pjsip_inv_create_uac(dlg, NULL, endpoint->extensions, &inv_session) != PJ_SUCCESS) {
		pjsip_dlg_terminate(dlg);
		return NULL;
	}

	pjsip_timer_setting_default(&timer);
	timer.min_se = endpoint->min_se;
	timer.sess_expires = endpoint->sess_expires;
	pjsip_timer_init_session(inv_session, &timer);

	if (!(session = ast_sip_session_alloc(endpoint, inv_session))) {
		pjsip_inv_terminate(inv_session, 500, PJ_FALSE);
		return NULL;
	}

	ast_format_cap_copy(session->req_caps, req_caps);
	if ((pjsip_dlg_add_usage(dlg, &session_module, NULL) != PJ_SUCCESS)) {
		pjsip_inv_terminate(inv_session, 500, PJ_FALSE);
		return NULL;
	}

	ao2_ref(session, +1);
	return session;
}

static int session_termination_task(void *data)
{
	RAII_VAR(struct ast_sip_session *, session, data, ao2_cleanup);
	pjsip_tx_data *packet = NULL;

	if (!session->inv_session) {
		return 0;
	}

	if (pjsip_inv_end_session(session->inv_session, 603, NULL, &packet) == PJ_SUCCESS) {
		ast_sip_session_send_request(session, packet);
	}

	return 0;
}

static void session_termination_cb(pj_timer_heap_t *timer_heap, struct pj_timer_entry *entry)
{
	struct ast_sip_session *session = entry->user_data;

	if (ast_sip_push_task(session->serializer, session_termination_task, session)) {
		ao2_cleanup(session);
	}
}

void ast_sip_session_defer_termination(struct ast_sip_session *session)
{
	pj_time_val delay = { .sec = 60, };

	session->defer_terminate = 1;

	session->scheduled_termination.id = 0;
	ao2_ref(session, +1);
	session->scheduled_termination.user_data = session;
	session->scheduled_termination.cb = session_termination_cb;

	if (pjsip_endpt_schedule_timer(ast_sip_get_pjsip_endpoint(), &session->scheduled_termination, &delay) != PJ_SUCCESS) {
		ao2_ref(session, -1);
	}
}

struct ast_sip_session *ast_sip_dialog_get_session(pjsip_dialog *dlg)
{
	pjsip_inv_session *inv_session = pjsip_dlg_get_inv_session(dlg);
	struct ast_sip_session *session;

	if (!inv_session ||
		!(session = inv_session->mod_data[session_module.id])) {
		return NULL;
	}

	ao2_ref(session, +1);

	return session;
}

enum sip_get_destination_result {
	/*! The extension was successfully found */
	SIP_GET_DEST_EXTEN_FOUND,
	/*! The extension specified in the RURI was not found */
	SIP_GET_DEST_EXTEN_NOT_FOUND,
	/*! The extension specified in the RURI was a partial match */
	SIP_GET_DEST_EXTEN_PARTIAL,
	/*! The RURI is of an unsupported scheme */
	SIP_GET_DEST_UNSUPPORTED_URI,
};

/*!
 * \brief Determine where in the dialplan a call should go
 *
 * This uses the username in the request URI to try to match
 * an extension in the endpoint's configured context in order
 * to route the call.
 *
 * \param session The inbound SIP session
 * \param rdata The SIP INVITE
 */
static enum sip_get_destination_result get_destination(struct ast_sip_session *session, pjsip_rx_data *rdata)
{
	pjsip_uri *ruri = rdata->msg_info.msg->line.req.uri;
	pjsip_sip_uri *sip_ruri;
	if (!PJSIP_URI_SCHEME_IS_SIP(ruri) && !PJSIP_URI_SCHEME_IS_SIPS(ruri)) {
		return SIP_GET_DEST_UNSUPPORTED_URI;
	}
	sip_ruri = pjsip_uri_get_uri(ruri);
	ast_copy_pj_str(session->exten, &sip_ruri->user, sizeof(session->exten));
	if (ast_exists_extension(NULL, session->endpoint->context, session->exten, 1, NULL)) {
		return SIP_GET_DEST_EXTEN_FOUND;
	}
	/* XXX In reality, we'll likely have further options so that partial matches
	 * can be indicated here, but for getting something up and running, we're going
	 * to return a "not exists" error here.
	 */
	return SIP_GET_DEST_EXTEN_NOT_FOUND;
}

static pjsip_inv_session *pre_session_setup(pjsip_rx_data *rdata, const struct ast_sip_endpoint *endpoint)
{
	pjsip_tx_data *tdata;
	pjsip_dialog *dlg;
	pjsip_inv_session *inv_session;
	unsigned int options = endpoint->extensions;

	if (pjsip_inv_verify_request(rdata, &options, NULL, NULL, ast_sip_get_pjsip_endpoint(), &tdata) != PJ_SUCCESS) {
		if (tdata) {
			pjsip_endpt_send_response2(ast_sip_get_pjsip_endpoint(), rdata, tdata, NULL, NULL);
		} else {
			pjsip_endpt_respond_stateless(ast_sip_get_pjsip_endpoint(), rdata, 500, NULL, NULL, NULL);
		}
		return NULL;
	}
	if (pjsip_dlg_create_uas(pjsip_ua_instance(), rdata, NULL, &dlg) != PJ_SUCCESS) {
		pjsip_endpt_respond_stateless(ast_sip_get_pjsip_endpoint(), rdata, 500, NULL, NULL, NULL);
		return NULL;
	}
	if (pjsip_inv_create_uas(dlg, rdata, NULL, 0, &inv_session) != PJ_SUCCESS) {
		pjsip_endpt_respond_stateless(ast_sip_get_pjsip_endpoint(), rdata, 500, NULL, NULL, NULL);
		pjsip_dlg_terminate(dlg);
		return NULL;
	}
	if (pjsip_dlg_add_usage(dlg, &session_module, NULL) != PJ_SUCCESS) {
		if (pjsip_inv_initial_answer(inv_session, rdata, 500, NULL, NULL, &tdata) != PJ_SUCCESS) {
			pjsip_inv_terminate(inv_session, 500, PJ_FALSE);
		}
		pjsip_inv_send_msg(inv_session, tdata);
		return NULL;
	}
	return inv_session;
}

static void handle_new_invite_request(pjsip_rx_data *rdata)
{
	RAII_VAR(struct ast_sip_endpoint *, endpoint,
			ast_pjsip_rdata_get_endpoint(rdata), ao2_cleanup);
	pjsip_tx_data *tdata = NULL;
	pjsip_inv_session *inv_session = NULL;
	struct ast_sip_session *session = NULL;
	pjsip_timer_setting timer;
	pjsip_rdata_sdp_info *sdp_info;
	pjmedia_sdp_session *local = NULL;

	ast_assert(endpoint != NULL);

	inv_session = pre_session_setup(rdata, endpoint);
	if (!inv_session) {
		/* pre_session_setup() returns a response on failure */
		return;
	}

	session = ast_sip_session_alloc(endpoint, inv_session);
	if (!session) {
		if (pjsip_inv_initial_answer(inv_session, rdata, 500, NULL, NULL, &tdata) == PJ_SUCCESS) {
			pjsip_inv_terminate(inv_session, 500, PJ_FALSE);
		} else {
			pjsip_inv_send_msg(inv_session, tdata);
		}
		return;
	}

	/* From this point on, any calls to pjsip_inv_terminate have the last argument as PJ_TRUE
	 * so that we will be notified so we can destroy the session properly
	 */

	switch (get_destination(session, rdata)) {
	case SIP_GET_DEST_EXTEN_FOUND:
		/* Things worked. Keep going */
		break;
	case SIP_GET_DEST_UNSUPPORTED_URI:
		if (pjsip_inv_initial_answer(inv_session, rdata, 416, NULL, NULL, &tdata) == PJ_SUCCESS) {
			ast_sip_session_send_response(session, tdata);
		} else  {
			pjsip_inv_terminate(inv_session, 416, PJ_TRUE);
		}
		return;
	case SIP_GET_DEST_EXTEN_NOT_FOUND:
	case SIP_GET_DEST_EXTEN_PARTIAL:
	default:
		ast_log(LOG_NOTICE, "Call from '%s' (%s:%s:%d) to extension '%s' rejected because extension not found in context '%s'.\n",
			ast_sorcery_object_get_id(session->endpoint), rdata->tp_info.transport->type_name, rdata->pkt_info.src_name,
			rdata->pkt_info.src_port, session->exten, session->endpoint->context);

		if (pjsip_inv_initial_answer(inv_session, rdata, 404, NULL, NULL, &tdata) == PJ_SUCCESS) {
			ast_sip_session_send_response(session, tdata);
		} else  {
			pjsip_inv_terminate(inv_session, 404, PJ_TRUE);
		}
		return;
	};

	if ((sdp_info = pjsip_rdata_get_sdp_info(rdata)) && (sdp_info->sdp_err == PJ_SUCCESS) && sdp_info->sdp) {
		if (handle_incoming_sdp(session, sdp_info->sdp)) {
			if (pjsip_inv_initial_answer(inv_session, rdata, 488, NULL, NULL, &tdata) == PJ_SUCCESS) {
				ast_sip_session_send_response(session, tdata);
			} else  {
				pjsip_inv_terminate(inv_session, 488, PJ_TRUE);
			}
			return;
		}
		/* We are creating a local SDP which is an answer to their offer */
		local = create_local_sdp(inv_session, session, sdp_info->sdp);
	} else {
		/* We are creating a local SDP which is an offer */
		local = create_local_sdp(inv_session, session, NULL);
	}

	/* If we were unable to create a local SDP terminate the session early, it won't go anywhere */
	if (!local) {
		if (pjsip_inv_initial_answer(inv_session, rdata, 500, NULL, NULL, &tdata) == PJ_SUCCESS) {
			ast_sip_session_send_response(session, tdata);
		} else  {
			pjsip_inv_terminate(inv_session, 500, PJ_TRUE);
		}
		return;
	} else {
		pjsip_inv_set_local_sdp(inv_session, local);
		pjmedia_sdp_neg_set_prefer_remote_codec_order(inv_session->neg, PJ_FALSE);
	}

	pjsip_timer_setting_default(&timer);
	timer.min_se = endpoint->min_se;
	timer.sess_expires = endpoint->sess_expires;
	pjsip_timer_init_session(inv_session, &timer);

	/* At this point, we've verified what we can, so let's go ahead and send a 100 Trying out */
	if (pjsip_inv_initial_answer(inv_session, rdata, 100, NULL, NULL, &tdata) != PJ_SUCCESS) {
		pjsip_inv_terminate(inv_session, 500, PJ_TRUE);
		return;
	}
	ast_sip_session_send_response(session, tdata);

	handle_incoming_request(session, rdata);
}

static pj_bool_t does_method_match(const pj_str_t *message_method, const char *supplement_method)
{
	pj_str_t method;

	if (ast_strlen_zero(supplement_method)) {
		return PJ_TRUE;
	}

	pj_cstr(&method, supplement_method);

	return pj_stristr(&method, message_method) ? PJ_TRUE : PJ_FALSE;
}

static pj_bool_t has_supplement(const struct ast_sip_session *session, const pjsip_rx_data *rdata)
{
	struct ast_sip_session_supplement *supplement;
	struct pjsip_method *method = &rdata->msg_info.msg->line.req.method;

	if (!session) {
		return PJ_FALSE;
	}

	AST_LIST_TRAVERSE(&session->supplements, supplement, next) {
		if (does_method_match(&method->name, supplement->method)) {
			return PJ_TRUE;
		}
	}
	return PJ_FALSE;
}
/*!
 * \brief Called when a new SIP request comes into PJSIP
 *
 * This function is called under two circumstances
 * 1) An out-of-dialog request is received by PJSIP
 * 2) An in-dialog request that the inv_session layer does not
 *    handle is received (such as an in-dialog INFO)
 *
 * In all cases, there is very little we actually do in this function
 * 1) For requests we don't handle, we return PJ_FALSE
 * 2) For new INVITEs, throw the work into the SIP threadpool to be done
 *    there to free up the thread(s) handling incoming requests
 * 3) For in-dialog requests we handle, we defer handling them until the
 *    on_inv_state_change() callback instead (where we will end up putting
 *    them into the threadpool).
 */
static pj_bool_t session_on_rx_request(pjsip_rx_data *rdata)
{
	pj_status_t handled = PJ_FALSE;
	pjsip_dialog *dlg = pjsip_rdata_get_dlg(rdata);
	pjsip_inv_session *inv_session;

	switch (rdata->msg_info.msg->line.req.method.id) {
	case PJSIP_INVITE_METHOD:
		if (dlg) {
			ast_log(LOG_WARNING, "on_rx_request called for INVITE in mid-dialog?\n");
			break;
		}
		handled = PJ_TRUE;
		handle_new_invite_request(rdata);
		break;
	default:
		/* Handle other in-dialog methods if their supplements have been registered */
		handled = dlg && (inv_session = pjsip_dlg_get_inv_session(dlg)) &&
			has_supplement(inv_session->mod_data[session_module.id], rdata);
		break;
	}

	return handled;
}

struct reschedule_reinvite_data {
	struct ast_sip_session *session;
	struct ast_sip_session_delayed_request *delay;
};

static struct reschedule_reinvite_data *reschedule_reinvite_data_alloc(
		struct ast_sip_session *session, struct ast_sip_session_delayed_request *delay)
{
	struct reschedule_reinvite_data *rrd = ast_malloc(sizeof(*rrd));
	if (!rrd) {
		return NULL;
	}
	ao2_ref(session, +1);
	rrd->session = session;
	rrd->delay = delay;
	return rrd;
}

static void reschedule_reinvite_data_destroy(struct reschedule_reinvite_data *rrd)
{
	ao2_cleanup(rrd->session);
	ast_free(rrd->delay);
	ast_free(rrd);
}

static int really_resend_reinvite(void *data)
{
	RAII_VAR(struct reschedule_reinvite_data *, rrd, data, reschedule_reinvite_data_destroy);

	return send_delayed_request(rrd->session, rrd->delay);
}

static void resend_reinvite(pj_timer_heap_t *timer, pj_timer_entry *entry)
{
	struct reschedule_reinvite_data *rrd = entry->user_data;

	ast_sip_push_task(rrd->session->serializer, really_resend_reinvite, entry->user_data);
}

static void reschedule_reinvite(struct ast_sip_session *session, ast_sip_session_response_cb on_response, pjsip_tx_data *tdata)
{
	struct ast_sip_session_delayed_request *delay = delayed_request_alloc("INVITE",
			NULL, on_response, tdata);
	pjsip_inv_session *inv = session->inv_session;
	struct reschedule_reinvite_data *rrd = reschedule_reinvite_data_alloc(session, delay);
	pj_time_val tv;
	
	if (!rrd || !delay) {
		return;
	}

	tv.sec = 0;
	if (inv->role == PJSIP_ROLE_UAC) {
		tv.msec = 2100 + ast_random() % 2000;
	} else {
		tv.msec = ast_random() % 2000;
	}

	pj_timer_entry_init(&session->rescheduled_reinvite, 0, rrd, resend_reinvite);

	pjsip_endpt_schedule_timer(ast_sip_get_pjsip_endpoint(), &session->rescheduled_reinvite, &tv);
}

static void __print_debug_details(const char *function, pjsip_inv_session *inv, pjsip_transaction *tsx, pjsip_event *e)
{
	struct ast_sip_session *session;
	ast_debug(5, "Function %s called on event %s\n", function, pjsip_event_str(e->type));
	if (!inv) {
		ast_debug(5, "Transaction %p does not belong to an inv_session?\n", tsx);
		ast_debug(5, "The transaction state is %s\n", pjsip_tsx_state_str(tsx->state));
		return;
	}
	session = inv->mod_data[session_module.id];
	if (!session) {
		ast_debug(5, "inv_session %p has no ast session\n", inv);
	} else {
		ast_debug(5, "The state change pertains to the session with %s\n",
				ast_sorcery_object_get_id(session->endpoint));
	}
	if (inv->invite_tsx) {
		ast_debug(5, "The inv session still has an invite_tsx (%p)\n", inv->invite_tsx);
	} else {
		ast_debug(5, "The inv session does NOT have an invite_tsx\n");
	}
	if (tsx) {
		ast_debug(5, "The transaction involved in this state change is %p\n", tsx);
		ast_debug(5, "The current transaction state is %s\n", pjsip_tsx_state_str(tsx->state));
		ast_debug(5, "The transaction state change event is %s\n", pjsip_event_str(e->body.tsx_state.type));
	} else {
		ast_debug(5, "There is no transaction involved in this state change\n");
	}
	ast_debug(5, "The current inv state is %s\n", pjsip_inv_state_name(inv->state));
}

#define print_debug_details(inv, tsx, e) __print_debug_details(__PRETTY_FUNCTION__, (inv), (tsx), (e))

static void handle_incoming_request(struct ast_sip_session *session, pjsip_rx_data *rdata)
{
	struct ast_sip_session_supplement *supplement;
	struct pjsip_request_line req = rdata->msg_info.msg->line.req;

	ast_debug(3, "Method is %.*s\n", (int) pj_strlen(&req.method.name), pj_strbuf(&req.method.name));
	AST_LIST_TRAVERSE(&session->supplements, supplement, next) {
		if (supplement->incoming_request && does_method_match(&req.method.name, supplement->method)) {
			if (supplement->incoming_request(session, rdata)) {
				break;
			}
		}
	}
}

static void handle_incoming_response(struct ast_sip_session *session, pjsip_rx_data *rdata)
{
	struct ast_sip_session_supplement *supplement;
	struct pjsip_status_line status = rdata->msg_info.msg->line.status;

	ast_debug(3, "Response is %d %.*s\n", status.code, (int) pj_strlen(&status.reason),
			pj_strbuf(&status.reason));

	AST_LIST_TRAVERSE(&session->supplements, supplement, next) {
		if (supplement->incoming_response && does_method_match(&rdata->msg_info.cseq->method.name, supplement->method)) {
			supplement->incoming_response(session, rdata);
		}
	}
}

static int handle_incoming(struct ast_sip_session *session, pjsip_rx_data *rdata)
{
	ast_debug(3, "Received %s\n", rdata->msg_info.msg->type == PJSIP_REQUEST_MSG ?
			"request" : "response");

	if (rdata->msg_info.msg->type == PJSIP_REQUEST_MSG) {
		handle_incoming_request(session, rdata);
	} else {
		handle_incoming_response(session, rdata);
	}

	return 0;
}

static void handle_outgoing_request(struct ast_sip_session *session, pjsip_tx_data *tdata)
{
	struct ast_sip_session_supplement *supplement;
	struct pjsip_request_line req = tdata->msg->line.req;

	ast_debug(3, "Method is %.*s\n", (int) pj_strlen(&req.method.name), pj_strbuf(&req.method.name));
	AST_LIST_TRAVERSE(&session->supplements, supplement, next) {
		if (supplement->outgoing_request && does_method_match(&req.method.name, supplement->method)) {
			supplement->outgoing_request(session, tdata);
		}
	}
}

static void handle_outgoing_response(struct ast_sip_session *session, pjsip_tx_data *tdata)
{
	struct ast_sip_session_supplement *supplement;
	struct pjsip_status_line status = tdata->msg->line.status;
	pjsip_cseq_hdr *cseq = pjsip_msg_find_hdr(tdata->msg, PJSIP_H_CSEQ, NULL);
	ast_debug(3, "Method is %.*s, Response is %d %.*s\n", (int) pj_strlen(&cseq->method.name),
		pj_strbuf(&cseq->method.name), status.code, (int) pj_strlen(&status.reason),
		pj_strbuf(&status.reason));

	AST_LIST_TRAVERSE(&session->supplements, supplement, next) {
		if (supplement->outgoing_response && does_method_match(&cseq->method.name, supplement->method)) {
			supplement->outgoing_response(session, tdata);
		}
	}
}

static void handle_outgoing(struct ast_sip_session *session, pjsip_tx_data *tdata)
{
	ast_debug(3, "Sending %s\n", tdata->msg->type == PJSIP_REQUEST_MSG ?
			"request" : "response");
	if (tdata->msg->type == PJSIP_REQUEST_MSG) {
		handle_outgoing_request(session, tdata);
	} else {
		handle_outgoing_response(session, tdata);
	}
}

static int session_end(struct ast_sip_session *session)
{
	struct ast_sip_session_supplement *iter;

	/* Stop the scheduled termination */
	if (pj_timer_heap_cancel(pjsip_endpt_get_timer_heap(ast_sip_get_pjsip_endpoint()), &session->scheduled_termination)) {
		ao2_ref(session, -1);
	}

	/* Session is dead. Let's get rid of the reference to the session */
	AST_LIST_TRAVERSE(&session->supplements, iter, next) {
		if (iter->session_end) {
			iter->session_end(session);
		}
	}

	session->inv_session->mod_data[session_module.id] = NULL;
	ast_sip_dialog_set_serializer(session->inv_session->dlg, NULL);
	ast_sip_dialog_set_endpoint(session->inv_session->dlg, NULL);
	ao2_cleanup(session);
	return 0;
}

static void session_inv_on_state_changed(pjsip_inv_session *inv, pjsip_event *e)
{
	struct ast_sip_session *session = inv->mod_data[session_module.id];

	print_debug_details(inv, NULL, e);

	switch(e->type) {
	case PJSIP_EVENT_TX_MSG:
		handle_outgoing(session, e->body.tx_msg.tdata);
		break;
	case PJSIP_EVENT_RX_MSG:
		handle_incoming(session, e->body.rx_msg.rdata);
		break;
	case PJSIP_EVENT_TSX_STATE:
		ast_debug(3, "Source of transaction state change is %s\n", pjsip_event_str(e->body.tsx_state.type));
		/* Transaction state changes are prompted by some other underlying event. */
		switch(e->body.tsx_state.type) {
		case PJSIP_EVENT_TX_MSG:
			handle_outgoing(session, e->body.tsx_state.src.tdata);
			break;
		case PJSIP_EVENT_RX_MSG:
			handle_incoming(session, e->body.tsx_state.src.rdata);
			break;
		case PJSIP_EVENT_TRANSPORT_ERROR:
		case PJSIP_EVENT_TIMER:
		case PJSIP_EVENT_USER:
		case PJSIP_EVENT_UNKNOWN:
		case PJSIP_EVENT_TSX_STATE:
			/* Inception? */
			break;
		}
		break;
	case PJSIP_EVENT_TRANSPORT_ERROR:
	case PJSIP_EVENT_TIMER:
	case PJSIP_EVENT_UNKNOWN:
	case PJSIP_EVENT_USER:
	default:
		break;
	}

	if (inv->state == PJSIP_INV_STATE_DISCONNECTED) {
		session_end(session);
	}
}

static void session_inv_on_new_session(pjsip_inv_session *inv, pjsip_event *e)
{
	/* XXX STUB */
}

static void session_inv_on_tsx_state_changed(pjsip_inv_session *inv, pjsip_transaction *tsx, pjsip_event *e)
{
	struct ast_sip_session *session = inv->mod_data[session_module.id];
	print_debug_details(inv, tsx, e);
	if (!session) {
		/* Transaction likely timed out after the call was hung up. Just
		 * ignore such transaction changes
		 */
		return;
	}
	switch (e->body.tsx_state.type) {
	case PJSIP_EVENT_TX_MSG:
		/* When we create an outgoing request, we do not have access to the transaction that
		 * is created. Instead, We have to place transaction-specific data in the tdata. Here,
		 * we transfer the data into the transaction. This way, when we receive a response, we
		 * can dig this data out again
		 */
		tsx->mod_data[session_module.id] = e->body.tsx_state.src.tdata->mod_data[session_module.id];
		break;
	case PJSIP_EVENT_RX_MSG:
		if (tsx->method.id == PJSIP_INVITE_METHOD) {
			if (tsx->role == PJSIP_ROLE_UAC && tsx->state == PJSIP_TSX_STATE_COMPLETED) {
				/* This means we got a non 2XX final response to our outgoing INVITE */
				if (tsx->status_code == PJSIP_SC_REQUEST_PENDING) {
					reschedule_reinvite(session, tsx->mod_data[session_module.id], tsx->last_tx);
					return;
				} else {
					/* Other failures result in destroying the session. */
					pjsip_tx_data *tdata;
					pjsip_inv_end_session(inv, 500, NULL, &tdata);
					ast_sip_session_send_request(session, tdata);
				}
			}
		} else {
			if (tsx->role == PJSIP_ROLE_UAS && tsx->state == PJSIP_TSX_STATE_TRYING) {
				handle_incoming_request(session, e->body.tsx_state.src.rdata);
			}
		}
		if (tsx->mod_data[session_module.id]) {
			ast_sip_session_response_cb cb = tsx->mod_data[session_module.id];
			cb(session, e->body.tsx_state.src.rdata);
		}
	case PJSIP_EVENT_TRANSPORT_ERROR:
	case PJSIP_EVENT_TIMER:
	case PJSIP_EVENT_USER:
	case PJSIP_EVENT_UNKNOWN:
	case PJSIP_EVENT_TSX_STATE:
		/* Inception? */
		break;
	}

	/* Terminated INVITE transactions always should result in queuing delayed requests,
	 * no matter what event caused the transaction to terminate
	 */
	if (tsx->method.id == PJSIP_INVITE_METHOD && tsx->state == PJSIP_TSX_STATE_TERMINATED) {
		queue_delayed_request(session);
	}
}

static int add_sdp_streams(void *obj, void *arg, void *data, int flags)
{
	struct ast_sip_session_media *session_media = obj;
	pjmedia_sdp_session *answer = arg;
	struct ast_sip_session *session = data;
	struct ast_sip_session_sdp_handler *handler = session_media->handler;
	RAII_VAR(struct sdp_handler_list *, handler_list, NULL, ao2_cleanup);

	if (handler) {
		/* if an already assigned handler does not handle the session_media or reports a catastrophic error, fail */
		if (handler->create_outgoing_sdp_stream(session, session_media, answer) <= 0) {
			return 0;
		}
		return CMP_MATCH;
	}

	handler_list = ao2_find(sdp_handlers, session_media->stream_type, OBJ_KEY);
	if (!handler_list) {
		return CMP_MATCH;
	}

	/* no handler for this stream type and we have a list to search */
	AST_LIST_TRAVERSE(&handler_list->list, handler, next) {
		int res = handler->create_outgoing_sdp_stream(session, session_media, answer);
		if (res < 0) {
			/* catastrophic error */
			return 0;
		}
		if (res > 0) {
			/* handled */
			return CMP_MATCH;
		}
	}

	/* streams that weren't handled won't be included in generated outbound SDP */
	return CMP_MATCH;
}

static struct pjmedia_sdp_session *create_local_sdp(pjsip_inv_session *inv, struct ast_sip_session *session, const pjmedia_sdp_session *offer)
{
	RAII_VAR(struct ao2_iterator *, successful, NULL, ao2_iterator_cleanup);
	static const pj_str_t STR_ASTERISK = { "Asterisk", 8 };
	static const pj_str_t STR_IN = { "IN", 2 };
	static const pj_str_t STR_IP4 = { "IP4", 3 };
	static const pj_str_t STR_IP6 = { "IP6", 3 };
	pjmedia_sdp_session *local;

	if (!(local = PJ_POOL_ZALLOC_T(inv->pool_prov, pjmedia_sdp_session))) {
		return NULL;
	}

	if (!offer) {
		local->origin.version = local->origin.id = (pj_uint32_t)(ast_random());
	} else {
		local->origin.version = offer->origin.version + 1;
		local->origin.id = offer->origin.id;
	}

	local->origin.user = STR_ASTERISK;
	local->origin.net_type = STR_IN;
	local->origin.addr_type = session->endpoint->rtp_ipv6 ? STR_IP6 : STR_IP4;
	local->origin.addr = *pj_gethostname();
	local->name = local->origin.user;

	/* Now let the handlers add streams of various types, pjmedia will automatically reorder the media streams for us */
	successful = ao2_callback_data(session->media, OBJ_MULTIPLE, add_sdp_streams, local, session);
	if (!successful || ao2_container_count(successful->c) != ao2_container_count(session->media)) {
		/* Something experienced a catastrophic failure */
		return NULL;
	}

	/* Use the connection details of the first media stream if possible for SDP level */
	if (local->media_count) {
		local->conn = local->media[0]->conn;
	}

	return local;
}

static void session_inv_on_rx_offer(pjsip_inv_session *inv, const pjmedia_sdp_session *offer)
{
	struct ast_sip_session *session = inv->mod_data[session_module.id];
	pjmedia_sdp_session *answer;

	if (handle_incoming_sdp(session, offer)) {
		return;
	}

	if ((answer = create_local_sdp(inv, session, offer))) {
		pjsip_inv_set_sdp_answer(inv, answer);
	}
}

#if 0
static void session_inv_on_create_offer(pjsip_inv_session *inv, pjmedia_sdp_session **p_offer)
{
	/* XXX STUB */
}
#endif

static void session_inv_on_media_update(pjsip_inv_session *inv, pj_status_t status)
{
	struct ast_sip_session *session = inv->mod_data[session_module.id];
	const pjmedia_sdp_session *local, *remote;

	if (!session->channel) {
		/* If we don't have a channel. We really don't care about media updates.
		 * Just ignore
		 */
		return;
	}

	if ((status != PJ_SUCCESS) || (pjmedia_sdp_neg_get_active_local(inv->neg, &local) != PJ_SUCCESS) ||
		(pjmedia_sdp_neg_get_active_remote(inv->neg, &remote) != PJ_SUCCESS)) {
		ast_channel_hangupcause_set(session->channel, AST_CAUSE_BEARERCAPABILITY_NOTAVAIL);
		ast_queue_hangup(session->channel);
		return;
	}

	handle_negotiated_sdp(session, local, remote);
}

static pjsip_redirect_op session_inv_on_redirected(pjsip_inv_session *inv, const pjsip_uri *target, const pjsip_event *e)
{
	struct ast_sip_session *session = inv->mod_data[session_module.id];

	if (PJSIP_URI_SCHEME_IS_SIP(target) || PJSIP_URI_SCHEME_IS_SIPS(target)) {
		const pjsip_sip_uri *uri = pjsip_uri_get_uri(target);
		char exten[AST_MAX_EXTENSION];

		ast_copy_pj_str(exten, &uri->user, sizeof(exten));
		ast_channel_call_forward_set(session->channel, exten);
	}

	return PJSIP_REDIRECT_STOP;
}

static pjsip_inv_callback inv_callback = {
	.on_state_changed = session_inv_on_state_changed,
	.on_new_session = session_inv_on_new_session,
	.on_tsx_state_changed = session_inv_on_tsx_state_changed,
	.on_rx_offer = session_inv_on_rx_offer,
	.on_media_update = session_inv_on_media_update,
	.on_redirected = session_inv_on_redirected,
};

/*! \brief Hook for modifying outgoing messages with SDP to contain the proper address information */
static void session_outgoing_nat_hook(pjsip_tx_data *tdata, struct ast_sip_transport *transport)
{
	struct ast_sip_nat_hook *hook = tdata->mod_data[session_module.id];
	struct pjmedia_sdp_session *sdp;
	int stream;

	/* SDP produced by us directly will never be multipart */
	if (hook || !tdata->msg->body || pj_stricmp2(&tdata->msg->body->content_type.type, "application") ||
		pj_stricmp2(&tdata->msg->body->content_type.subtype, "sdp") || ast_strlen_zero(transport->external_media_address)) {
		return;
	}

	sdp = tdata->msg->body->data;

	for (stream = 0; stream < sdp->media_count; ++stream) {
		/* See if there are registered handlers for this media stream type */
		char media[20];
		struct ast_sip_session_sdp_handler *handler;
		RAII_VAR(struct sdp_handler_list *, handler_list, NULL, ao2_cleanup);

		/* We need a null-terminated version of the media string */
		ast_copy_pj_str(media, &sdp->media[stream]->desc.media, sizeof(media));

		handler_list = ao2_find(sdp_handlers, media, OBJ_KEY);
		if (!handler_list) {
			ast_debug(1, "No registered SDP handlers for media type '%s'\n", media);
			continue;
		}
		AST_LIST_TRAVERSE(&handler_list->list, handler, next) {
			if (handler->change_outgoing_sdp_stream_media_address) {
				handler->change_outgoing_sdp_stream_media_address(tdata, sdp->media[stream], transport);
			}
		}
	}

	/* We purposely do this so that the hook will not be invoked multiple times, ie: if a retransmit occurs */
	tdata->mod_data[session_module.id] = nat_hook;
}

static int load_module(void)
{
	pjsip_endpoint *endpt;
	if (!ast_sip_get_sorcery() || !ast_sip_get_pjsip_endpoint()) {
		return AST_MODULE_LOAD_DECLINE;
	}
	if (!(nat_hook = ast_sorcery_alloc(ast_sip_get_sorcery(), "nat_hook", NULL))) {
		return AST_MODULE_LOAD_DECLINE;
	}
	nat_hook->outgoing_external_message = session_outgoing_nat_hook;
	ast_sorcery_create(ast_sip_get_sorcery(), nat_hook);
	sdp_handlers = ao2_container_alloc(SDP_HANDLER_BUCKETS,
			sdp_handler_list_hash, sdp_handler_list_cmp);
	if (!sdp_handlers) {
		return AST_MODULE_LOAD_DECLINE;
	}
	endpt = ast_sip_get_pjsip_endpoint();
	pjsip_inv_usage_init(endpt, &inv_callback);
	pjsip_100rel_init_module(endpt);
	pjsip_timer_init_module(endpt);
	if (ast_sip_register_service(&session_module)) {
		return AST_MODULE_LOAD_DECLINE;
	}
	return AST_MODULE_LOAD_SUCCESS;
}

static int unload_module(void)
{
	ast_sip_unregister_service(&session_module);
	if (nat_hook) {
		ast_sorcery_delete(ast_sip_get_sorcery(), nat_hook);
		nat_hook = NULL;
	}
	return 0;
}

AST_MODULE_INFO(ASTERISK_GPL_KEY, AST_MODFLAG_GLOBAL_SYMBOLS | AST_MODFLAG_LOAD_ORDER, "SIP Session resource",
		.load = load_module,
		.unload = unload_module,
		.load_pri = AST_MODPRI_APP_DEPEND,
	       );