<!-- Module Developer's Guide -->

<chapter>
    <title>&develguide;</title>
    <para>
		The module provides the following functions that can be used
		in other &osips; modules.
   </para>
 		<section>
				<title>
				<function moreinfo="none">bind_presence(presence_api_t* api)</function>
				</title>
			<para>
				This function binds the presence modules and fills the structure 
				with the exported functions that represent functions adding events
				in presence module and functions specific for Subscribe processing.
			</para>
		<example>
		<title><function>presence_api_t</function> structure</title>
	<programlisting format="linespecific">
...
typedef struct presence_api {
	add_event_t add_event;
	contains_event_t contains_event;
	search_event_t search_event;
	get_event_list_t get_event_list;
	
	update_watchers_t update_watchers_status;
	
	/* subs hash table handling functions */
	new_shtable_t new_shtable;
	destroy_shtable_t destroy_shtable;
	insert_shtable_t insert_shtable;
	search_shtable_t search_shtable;
	delete_shtable_t delete_shtable;
	update_shtable_t update_shtable;
	/* function to duplicate a subs structure*/
	mem_copy_subs_t  mem_copy_subs;
	/* function used for update in database*/
	update_db_subs_t update_db_subs;
	/* function to extract dialog information from a
	SUBSCRIBE message */
	extract_sdialog_info_t extract_sdialog_info;
	/* function to request sphere defition for a presentity */
	pres_get_sphere_t get_sphere;
	pres_contains_presence_t contains_presence;
}presence_api_t;
...
</programlisting>
		</example>

		</section>
	
	<section>
		<title>
		<function moreinfo="none">add_event</function>
		</title>
		<para>
			Field type:
		</para>
			<programlisting format="linespecific">
...
typedef int (*add_event_t)(pres_ev_t* event);
...
</programlisting>
		<para>
			This function receives as a parameter a structure with event specific
			information and adds it to presence event list.
		</para>
		<para>
		The structure received as a parameter:
		</para>
	<programlisting format="linespecific">
...
typedef struct pres_ev
{
	str name;
	event_t* evp;
	str content_type;
	int default_expires;
	int type;
	int etag_not_new;
	/*
	 *  0 - the standard mechanism (allocating new etag
			for each Publish)
	 *  1 - allocating an etag only
			for an initial Publish 
	*/
	int req_auth;
	get_rules_doc_t* get_rules_doc;
	apply_auth_t*  apply_auth_nbody;
	is_allowed_t*  get_auth_status;
	
	/* an agg_body_t function should be registered
	 * if the event permits having multiple published
	 * states and requires an aggregation of the information
	 * otherwise, this field should be NULL and the last
	 * published state is taken when constructing Notify msg
	 */
	agg_nbody_t* agg_nbody;
	publ_handling_t  * evs_publ_handl;
	subs_handling_t  * evs_subs_handl;
	free_body_t* free_body;
	
	/* sometimes it is necessary that a module make changes for a body for each 
	 * active watcher (e.g. setting the "version" parameter in an XML document.
	 * If a module registers the aux_body_processing callback, it gets called for
	 * each watcher. It either gets the body received by the PUBLISH, or the body
	 * generated by the agg_nbody function.
	 * The module can deceide if it makes a copy of the original body, which is then
	 * manipulated, or if it works directly in the original body. If the module makes a
	 * copy of the original body, it also has to register the aux_free_body() to 
	 * free this "per watcher" body.
	 */
	aux_body_processing_t* aux_body_processing;
	free_body_t* aux_free_body;

	struct pres_ev* wipeer;			
	struct pres_ev* next;
	
}pres_ev_t;
...
</programlisting>
		</section>
<section>
		<title>
			<function moreinfo="none">get_rules_doc</function>
		</title>
		<para>
		
		</para>
		<para>
			Filed type:
			<programlisting format="linespecific">
...
typedef int (get_rules_doc_t)(str* user, str* domain, str** rules_doc);
...
			</programlisting>
		</para>
		<para>
		This function returns the authorization rules document that will be
		used in obtaining the status of the subscription and processing the
		notified body. A reference to the document should be put in the 
		auth_rules_doc of the subs_t structure given as a parameter to the
		functions described bellow.
		</para>
</section>	

<section>
		<title>
			<function moreinfo="none">get_auth_status</function>
		</title>
		<para>
			This filed is a function to be called for a subscription request
			to return the state for that subscription according to
			authorization rules. In the auth_rules_doc field of the subs_t
			structure received as a parameter should contain the rules 
			document of the presentity in case, if it exists.
		</para>
		<para>
			It is called only if the req_auth field is not 0. 
		</para>
		<para>
			Filed type:
			<programlisting format="linespecific">
...
typedef int (is_allowed_t)(struct subscription* subs);
...
			</programlisting>
			</para>
</section>	

<section>
		<title>
			<function moreinfo="none">apply_auth_nbody</function>
		</title>
		<para>
			This parameter should be a function to be called for an event 
			that requires authorization, when constructing final body. 
			The authorization document is taken from the auth_rules_doc
			field of the subs_t structure given as a parameter.
			It is called only if the req_auth field is not 0.
		</para>
		<para>
			Filed type:
			<programlisting format="linespecific">
...
typedef int (apply_auth_t)(str* , struct subscription*, str** );
...
			</programlisting>
			</para>
</section>			

<section>
		<title>
			<function moreinfo="none">agg_nbody</function>
		</title>
		<para>
			If present, this field marks that the events requires aggregation
			of states. This function receives a body array and should return
			the final body.	If not present, it is considered that the event
			does not require aggregation and the most recent published
			information is used when constructing Notifies.
		</para>
		<para>
		Filed type:
			<programlisting format="linespecific">
...
typedef str* (agg_nbody_t)(str* pres_user, str* pres_domain, 
str** body_array, int n, int off_index);
..
			</programlisting>
		</para>
</section>	

<section>
		<title>
			<function moreinfo="none">free_body</function>
		</title>
		<para>
			This field must be field in if subsequent processing is performed
			on the info from database before being inserted in Notify
			message body(if agg_nbody or apply_auth_nbody fields are
			filled in). It should match the allocation function used when
			processing the body.  
		</para>
		<para>
		Filed type:
			<programlisting format="linespecific">
...
typedef void(free_body_t)(char* body);
..
			</programlisting>
		</para>
</section>	

<section>
		<title>
			<function moreinfo="none">aux_body_processing</function>
		</title>
		<para>
			This field must be set if the module needs to manipulate the NOTIFY body 
			for each watcher. E.g. if the XML body includes a 'version' parameter which 
			will be increased for each NOTIFY, on a "per watcher" basis.
			The module can either allocate a new buffer for the new body an return it (aux_free_body
			function must be set too) or it manipualtes the original body directly and returns NULL.
		</para>
		<para>
		Filed type:
			<programlisting format="linespecific">
...
typedef str* (aux_body_processing_t)(struct subscription *subs, str* body);
..
			</programlisting>
		</para>
</section>	

<section>
		<title>
			<function moreinfo="none">aux_free_body</function>
		</title>
		<para>
			This field must be set if the module registers the aux_body_processing function
			and allocates memory for the new modified body. Then, this function will be used
			to free the pointer returned by the aux_body_processing function.
			If the module does use the aux_body_processing, but does not allocate new memory, but
			manipulates directly the original body buffer, then the aux_body_processing
			must return NULL and this field should not be set.
		</para>
		<para>
		Filed type:
			<programlisting format="linespecific">
...
typedef void(free_body_t)(char* body);
..
			</programlisting>
		</para>
</section>	

<section>
		<title>
			<function moreinfo="none">evs_publ_handl</function>
		</title>
		<para>
		This function is called when handling Publish requests. Most contain 
		body correctness check.
		</para>
		<para>
			<programlisting format="linespecific">
...
typedef int (publ_handling_t)(struct sip_msg*);
..
			</programlisting>
			</para>
</section>	

<section>
		<title>
			<function moreinfo="none">evs_subs_handl</function>
		</title>
		<para>
		It is not compulsory. Should contain event specific handling for
		Subscription requests.
		</para>
		<para>
		Filed type:
			</para>
			<programlisting format="linespecific">
...
typedef int (subs_handling_t)(struct sip_msg*);
..
</programlisting>
</section>	

<section>
	<title>
	<function moreinfo="none">contains_event</function>
	</title>
	<para>
		Field type:
	</para>
		<programlisting format="linespecific">
..
typedef pres_ev_t* (*contains_event_t)(str* name,
event_t* parsed_event);
...
</programlisting>
	<para>
	The function parses the event name received as a parameter and searches
	the result in the list. It returns the found event or NULL, if not found. 
	If the second argument is an allocated event_t* structure it fills it
	with the result of the parsing.
	</para>
</section>

<section>
	<title>
	<function moreinfo="none">get_event_list</function>
	</title>
	<para>
		Field type:
	</para>
		<programlisting format="linespecific">
...
typedef int (*get_event_list_t) (str** ev_list);
...
</programlisting>
	<para>
	This function returns a string representation of the events registered
	in presence module.( used for Allowed-Events header).
	</para>
</section>

<section>
	<title>
	<function moreinfo="none">update_watchers_status</function>
	</title>
	<para>
		Field type:
	</para>
		<programlisting format="linespecific">
...
typedef int (*update_watchers_t)(str pres_uri, pres_ev_t* ev,
str* rules_doc);
...
</programlisting>
	<para>
	This function is an external command that can be used to announce a change
	in authorization rules for a presentity. It updates the stored status and
	sends a Notify to the watchers whose status has changes. (used by
	presence_xml module when notified through an MI command of a change in
	an xcap document).
	</para>
</section>

<section>
	<title>
	<function moreinfo="none">get_sphere</function>
	</title>
	<para>
		Field type:
	</para>
		<programlisting format="linespecific">
...
typedef char* (*pres_get_sphere_t)(str* pres_uri);
...
</programlisting>
	<para>
	This function searches for a sphere definition in the published information
	if this has type RPID. If not found returns NULL. (the return value is
	allocated in private memory and should be freed)
	</para>
</section>

<section>
	<title>
	<function moreinfo="none">contains_presence</function>
	</title>
	<para>
		Field type:
	</para>
		<programlisting format="linespecific">
...
typedef int (*pres_contains_presence_t)(str* pres_uri);
...
</programlisting>
	<para>
	This function searches is a presence uri has published any presence
	information. It return 1 if a record is found, -1 otherwise.
	</para>
</section>

</chapter>

