===========================================

    Mcabber module writing brief howto

===========================================

To obtain information on module mcabber uses struct module_info_t, that

module should provide in public variable with name info_<modulename>.

If the module name contains any extra symbols except [a-z0-9_] they

should be replaced with '_'.

------------------------------------------------------------------------

  #include <mcabber/modules.h>

  typedef void (*module_init_t)(void);

  typedef void (*module_uninit_t)(void);

  typedef struct module_info_struct module_info_t;

  struct module_info_struct {

    const gchar      *branch;

    guint             api;

    const gchar      *version;

    const gchar      *description;

    const gchar     **requires;

    module_init_t     init;

    module_uninit_t   uninit;

    module_info_t    *next;

  };

------------------------------------------------------------------------

Callbacks init and uninit will be called after module and its

dependencies loading.  'requires' can contain a NULL-terminated list of

module names, that should be loaded before this.  'branch' and 'api' are

required and should contain mcabber branch and api version, that this

module is designed to work with.  For these values see ChangeLog.api.

'version' and 'description' fields are optional and just provide user

with additional information about the module.  'description' field can

contain newlines.  The 'next' field can contain pointer to the next

struct with another branch of mcabber, if your module can work with

multiple branches.

To load modules, mcabber uses glib's GModule, thus, in your module you

can also use functions

------------------------------------------------------------------------

  #include <glib.h>

  #include <gmodule.h>

  const gchar* g_module_check_init (GModule *module);

  void         g_module_unload (GModule *module);

------------------------------------------------------------------------

to do something before any version/dependency check is performed when

your module is loaded/unloaded.  On success g_module_check_init should

return NULL, and error message otherwise.

As module is loaded, you can use mcabber functions, declared in

mcabber's header files (though you should consider, that they may change

their calling conventions some day).

I will not explain them all, there are too much of them, but will

provide description for those, provided especially for module writers.

------------------------------------------------------------------------

  #include <mcabber/modules.h>

  const gchar *module_load (const gchar *name,

			    gboolean manual,

			    gboolean force);

  const gchar *module_unload (const gchar *name,

			      gboolean manual,

			      gboolean force);

------------------------------------------------------------------------

These functions load and unload modules respectively.  You can use them

to handle optional dependencies.  What happens, when module is loaded:

 - check if module is present, and if present just increase it's

   reference count

 - load .so via glib (and call g_module_check_init, if present)

 - check for information structure presence

 - find suitable branch and check api version compatibility

 - load modules, that this module requires (note, that dependency

   problems will be reported as error invariably, force flag have no

   effect on this check)

 - module placed into a list of modules

 - module init routine is called

And when unloaded:

 - check if module is present

 - decrease reference count, if it is not zero, return

 - run module uninit routine

 - unload modules, that were loaded as dependencies for this one

 - remove from modules list

They return error message or NULL in case of success.  'manual' flag

indicates, that module will be loaded by direct user request.  It serves

the purpose of tracking user and automatic references (user can have

only one).  'force' flag on module loading causes mcabber to ignore most

of the loading errors.  On unload it forces unloading even if reference

count is not zero.

------------------------------------------------------------------------

  #include <mcabber/commands.h>

  void cmd_add (const char *name, const char *help,

                guint flags1, guint flags2,

		void (*f)(char*), gpointer userdata);

  void cmd_del (const char *name);

------------------------------------------------------------------------

These two functions are provided to declare mcabber commands, offered by

your module.

 - name is a command name.

 - help is a short description of your command, however for now it is

   not used at all and can be omitted.

 - flags are completion identifiers for first and second command

   arguments, for list of built-in completions, see compl.h.  You can

   declare your own completion lists, using functions from compl.h,

   described later.

 - f is a user-provided callback function, that will be called upon

   executing mcabber command.  If you will provide non-NULL userdata,

   function must be of type

   void (*f) (char *commandline, gpointer userdata).

 - userdata is a pointer to data, transparently passed to callback.

   See f description.

------------------------------------------------------------------------

  #include <mcabber/compl.h>

  guint compl_new_category (void);

  void  compl_del_category (guint id);

  void    compl_add_category_word (guint categ,

                                   const char *command);

  void    compl_del_category_word (guint categ,

                                   const char *word);

  GSList *compl_get_category_list (guint cat_flags,

                                   guint *dynlist);

------------------------------------------------------------------------

These functions allow you to define and manage word lists for completion

categories, used by your commands.  First you need to obtain handle for

completion type, that you later will supply as flags, when declaring

your commands.  For that use function compl_new_category.  It returns

new category id, or zero if mcabber runs out of completion ids (for now

there are only 32 ids available, and 20 of them are already used for

builtin commands).  compl_del_category allows you to delete user-defined

category, deleting all words in it too.

Now, that you have a completion category, you can at any time add or

delete words from its completion list.  To do that, use the functions

compl_add_category_word and compl_del_category_word.  You can obtain

current contents of category by using gompl_get_category_list.  If after

execution dynlist is TRUE, you should free obtained list of words (both,

words and list).

------------------------------------------------------------------------

  #include <mcabber/hooks.h>

  typedef struct {

    const char *name;

    const char *value;

  } hk_arg_t;

  typedef guint (*hk_handler_t) (const gchar *hookname,

				 hk_arg_t *args,

				 gpointer userdata);

  guint hk_add_handler (hk_handler_t handler,

			const gchar *hookname,

			gint priority,

			gpointer userdata);

  void hk_del_handler (const gchar *hookname,

                       guint hid);

------------------------------------------------------------------------

These functions allow your module to react to events, such as incoming

and outgoing messages, buddy status changes and server connection

establishment or breakup.  The hookname string specifies the events the

handler wants to subscribe to.  The available strings can be found in

hooks.h.

The hk_add_handler() function will return a handler id which you will

use to remove the handler with hk_del_handler().

Args argument is a list of hk_arg_t structures, terminated by structure,

whose name field is set to NULL.

Your handler should return one of the values in the hk_handler_result

enum (see hooks.h), usually HOOK_HANDLER_RESULT_ALLOW_MORE_HANDLERS so

that other handlers can be triggers as well.

A handler can determine which event has occured by checking the hookname

argument (a same hook handler can subscribe to several events by using

hk_add_handler() several times).

Currently the following events exist:

 - hook-pre-message-in (HOOK_PRE_MESSAGE_IN) with parameters

   * jid - sender of the incoming message

   * resource - resource of the incoming message

   * message - message body, converted to locale charset

   * groupchat - ("true" or "false")

   * delayed - message timestamp (ISO-8601 string) or empty string if

     the message wasn't delayed

 - hook-post-message-in (HOOK_POST_MESSAGE_IN) with parameters

   * jid - sender of the incoming message

   * resource - resource of the incoming message

   * message - message body, converted to locale charset

   * groupchat - ("true" or "false")

   * attention - In a MUC message, true if you've been highlighted

     In a regular message, true if the sender has requested your

     attention (only implemented for MUC currently)

   * delayed - message timestamp (ISO-8601 string) or empty string if

     the message wasn't delayed

 - hook-message-out (HOOK_MESSAGE_OUT) with parameters

   * jid - recipient of the outgoing message

   * message - message body, converted to locale charset

 - hook-status-change (HOOK_STATUS_CHANGE) with

   parameters

   * jid - buddy, whose status has changed

   * resource - resource, whose status has changed

   * old_status - old status of the buddy, one-char string,

     representing mcabber status letter - one of 'ofdna?_'.

   * new_status - new buddy status.  Same as above.

   * message - new status message.  Old one should still be

     available to module as the current buddy's message.

 - hook-my-status-change (HOOK_MY_STATUS_CHANGE) with

   parameters

   * new_status - user's new status, see

     hook-status-change.  Old one should still be

     available as the current status of the user.

   * message - new status message

 - hook-post-connect (HOOK_POST_CONNECT) with no parameters

 - hook-pre-disconnect (HOOK_PRE_DISCONNECT) with no parameters

 - hook-unread-list-change (HOOK_UNREAD_LIST_CHANGE)

   * unread - number of buffers with the pending message flag (#)

   * attention - number of non-MUC buffers with the attention sign (!)

   * muc_unread - number of MUC buffers with the unread message flag

   * muc_attention - number of MUC buffers with the attention sign

------------------------------------------------------------------------

  #include <mcabber/xmpp_helper.h>

  void xmpp_add_feature (const char *xmlns);

  void xmpp_del_feature (const char *xmlns);

------------------------------------------------------------------------

These functions may be useful, if your module implements some additional

functionality to mcabber, that should be advertised in a client's

discovery features list.

=====================

   Example: hello

=====================

Now, let's write a simple module, called "hello", that will do no more

than just print something on loading and unloading.

------------------------------------------------------------------------

#include <glib.h>

#include <gmodule.h>

/* We will use scr_log_print() mcabber function,

   that does mcabber's messages output */

#include <mcabber/logprint.h>

/* Print something on module loading */

const gchar* g_module_check_init(GModule *module)

{

	scr_log_print(LPRINT_NORMAL, "Hello, World!");

	return NULL;

}

/* ... and unloading */

void g_module_unload(GModule *module)

{

	scr_log_print(LPRINT_NORMAL, "Bye, World!");

}

/* The End */

------------------------------------------------------------------------

Now, compile this file (hello.c) with

libtool --mode=compile gcc `pkg-config --cflags glib-2.0 \

  gmodule-2.0 mcabber` -c hello.c

libtool --mode=link gcc -module -rpath /usr/lib/mcabber/ \

  `pkg-config --libs glib-2.0 gmodule-2.0 mcabber` \

  -o libhello.la hello.lo

(you should substitute /usr/lib/mcabber to the directory where

your modules are located) and then install obtained module with

libtool --mode=install install libhello.la \

  /usr/lib/mcabber/libhello.la

Note that you most likely need not run suggested by libtool finish

action, as we're working with module object, not system- wide library,

but maybe some systems require that.

Now, set modules_dir mcabber variable to point to your modules

directory, and try to run /module -f load hello.  If all goes well,

you should see in status buffer message "Hello World!" (as well as

some complaints, as we forced module loading).

Now unload module by running command /module unload hello,

that should bring up message "Bye, World!".

That's it, you just created very simple dynamically loadable mcabber

module.  But, as you noticed, it needs force to be loaded.  Now, let's

add the information structure that mcabber wants.

==========================

   Example: info struct

==========================

------------------------------------------------------------------------

#include <mcabber/logprint.h>

/* module_info_t definition */

#include <mcabber/modules.h>

/* Print something on module loading */

void hello_init(void)

{

	scr_log_print(LPRINT_NORMAL, "Hello, World!");

}

/* ... and unloading */

void hello_uninit(void)

{

	scr_log_print(LPRINT_NORMAL, "Bye, World!");

}

module_info_t info_hello = {

	.branch          = "dev",

	.api             = 1,

	.version         = "0.0.1",

	.description     = "Hello world module\n"

		" (as well as bye world module)",

	.requires        = NULL,

	.init            = hello_init,

	.uninit          = hello_uninit,

	.next            = NULL,

};

/* The End */

------------------------------------------------------------------------

Here we still do not use glib nor gmodule, so, we can omit them in

compilation lines:

libtool --mode=compile gcc `pkg-config --cflags mcabber` \

  -c hello.c

libtool --mode=link gcc -module -rpath /usr/lib/mcabber/ \

  `pkg-config --libs mcabber` -o libhello.la hello.lo

Again compile it, copy, and try to load, now without -f flag.  As you

may notice, when loading previous example, mcabber first printed "Hello,

World!", and only then complaint about module not having information

struct.  That's because g_module_check_init is called right after module

loading, before mcabber even has a chance to look at module, while .init

from info struct is called afterwards by mcabber itself.  You can try to

introduce some error (e.g. too high or missing target mcabber version)

and see the difference.

=======================

   Example: command

=======================

Now, let's allow our module to do some real work.

------------------------------------------------------------------------

#include <mcabber/logprint.h>

#include <mcabber/commands.h>

#include <mcabber/modules.h>

/* Handler for command */

void do_hello(char *args)

{

	/* args contains command line with command

         * name and any spaces after it stripped */

	scr_log_print(LPRINT_NORMAL, "Hello, %s!",

                      *args != '\0' ? args : "World");

}

/* Register command */

void hello_init(void)

{

	cmd_add("hello", "", 0, 0, do_hello, NULL);

}

/* Unregister command */

void hello_uninit(void)

{

	cmd_del("hello");

}

module_info_t hello_info = {

	.branch          = "dev",

	.api             = 1,

	.version         = "0.0.2",

	.description     = "Hello world module\n"

		" Provides command /hello",

	.requires        = NULL,

	.init            = hello_init,

	.uninit          = hello_uninit,

	.next            = NULL,

}

/* The End */

------------------------------------------------------------------------

Now, compile it and try to load and run /hello with some arguments.

Note, that we used one-argument version of command handler, as we have

specified no userdata.

==========================

   Example: completion

==========================

Now let's investigate how to provide custom completion to your commands.

You can as well use built-in completions, their IDs are listed in

compl.h.

------------------------------------------------------------------------

#include <mcabber/logprint.h>

#include <mcabber/commands.h>

#include <mcabber/modules.h>

#include <mcabber/compl.h>

static guint hello_cid = 0;

/* hello command handler */

void do_hello(char *args)

{

	/* If argument is provided, add it to

	 * completions list. */

	if (hello_cid && *args != '\0')

		compl_add_category_word(hello_cid,

		                        args);

	scr_log_print(LPRINT_NORMAL, "Hello, %s!",

	              *args != '\0' ? args : "World");

}

/* Initialization */

void hello_init(void)

{

	/* Obtain handle for our completion

	 * category */

	hello_cid = compl_new_category();

	if (hello_cid)

		/* Add known default word to

		 * completion list */

		compl_add_category_word(hello_cid,

		                         "World");

	cmd_add("hello", "", hello_cid, 0, do_hello,

                 NULL);

}

/* Deinitialization */

void hello_uninit(void)

{

	/* Give back category handle */

	if (hello_cid)

		compl_del_category(hello_cid);

	cmd_del("hello");

}

module_info_t hello_info = {

	.branch          = "dev",

	.api             = 1,

	.version         = "0.0.3",

	.description     = "Hello world module"

		" Provides command /hello with completion",

	.requires        = NULL,

	.init            = hello_init,

	.uninit          = hello_uninit,

	.next            = NULL,

}