evennia/docs/sphinx/source/wiki/Commands.rst

Command system
==============

The basic way for users to communicate with the game is through
*Commands*. These can be commands directly related to the game world
such as *look*, *get*, *drop* and so on, or administrative commands such
as *examine* or *@dig*.

The `default commands <DefaultCommandHelp.html>`_ coming with Evennia
are 'MUX-like' in that they use @ for admin commands, support things
like switches, syntax with the '=' symbol etc, but there is nothing that
prevents you from implementing a completely different command scheme for
your game. You can find the default commands in
``src/commands/default``. You should not edit these directly - they will
be updated by the Evennia team as new features are added. Rather you
should look to them for inspiration and inherit your own designs from
them.

There are two components to having a command running - the *Command*
class and the *Command Set*.

A *Command* is a python class containing all the functioning code for
what a command does - for example, a *get* command would contain code
for picking up objects.

A *Command Set* (often referred to as a CmdSet) is like a container for
one or more Commands. A given Command can go into any number of
different command sets. By putting the command set on a character object
you will make all the commands therein available to use by that
character. You can also store command sets on normal objects if you want
users to be able to use the object in various ways. Consider a "Tree"
object with a cmdset defining the commands *climb* and *chop down*. Or a
"Clock" with a cmdset containing the single command *check time*.

This page goes into full detail about how to use Commands. There is also
a step-by-step `beginner's tutorial <AddingCommandTutorial.html>`_ that
will get you started quickly without the explanations.

Defining a Command
------------------

All commands are implemented as normal Python classes inheriting from
the base class ``Command`` (``ev.Command``). You will find that this
base class is very "bare". The default commands of Evennia actually
inherit from a child of ``Command`` called ``MuxCommand`` - this is the
class that knows all the mux-like syntax like ``/switches``, splitting
by "=" etc. Below we'll avoid mux-specifics and use the base ``Command``
class directly.

::

    # basic Command definition
    from ev import Command
    class MyCmd(Command):
       """
       This is the help-text for the command
       """
       key = "mycommand" 
       def parse(self):
           # parsing the command line here
       def func(self):
           # executing the command here 

You define a new command by assigning a few class-global properties on
your inherited class and overloading one or two hook functions. The full
gritty mechanic behind how commands work are found towards the end of
this page; for now you only need to know that the command handler
creates an instance of this class and uses that instance whenever you
use this command - it also dynamically assigns the new command instance
a few useful properties that you can assume to always be available.

Properties assigned to the command instance at run-time
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Let's say player *Bob* with a character *BigGuy* enters the command
*look at sword*. After the system having successfully identified this a
the "look" command and determined that *BigGuy* really has access to a
command named ``look``, it chugs the ``look`` command class out of
storage and either loads an existing Command instance from cache or
creates one. After some more checks it then assigns it the following
properties:

-  ``caller`` - a reference to the object executing the command - this
   is normally the Character\_BigGuy\_, not his Player *Bob* ! If you
   want to do something to the player (*Bob*) in your command, do so
   through ``caller.player``. (Since cmdsets can be put directly on
   Players, caller *can* be a Player object as well, such commands are
   usually quite specific though).
-  ``cmdstring`` - the matched key for the command. This would be *look*
   in our example.
-  ``args`` - this is the rest of the string, except the command name.
   So if the string entered was *look at sword*, ``args`` would be "*at
   sword*\ ".
-  ``obj`` - the game `Object <Objects.html>`_ on which this command is
   defined. This need not be the caller, but since ``look`` is a common
   (default) command, this is probably defined directly on *BigGuy* - so
   ``obj`` will point to BigGuy. Otherwise ``obj`` could be a Player or
   any interactive object with commands defined on it, like in the
   example of the "check time" command defined on a "Clock" object or a
   `red
   button <https://code.google.com/p/evennia/source/browse/trunk/game/gamesrc/objects/examples/red_button.py>`_
   that you can "``push``\ ".
-  ``cmdset`` - this is a reference to the merged CmdSet (see below)
   from which this command was matched. This variable is rarely used,
   it's main use is for the `auto-help system <HelpSystem.html>`_
   (*Advanced note: the merged cmdset need NOT be the same as
   BigGuy.cmdset. The merged set can be a combination of the cmdsets
   from other objects in the room, for example*).
-  ``sessid`` - this is an integer identifier for the Session triggering
   this command, if any. This is seldomly needed directly.
-  ``raw_string`` - this is the raw input coming from the user, without
   stripping any surrounding whitespace. The only thing that is stripped
   is the ending newline marker.

Defining your own command classes
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Beyond the properties Evennia always assigns to the command at runtime
(listed above), your job is to define the following class properties:

-  ``key`` (string) - the identifier for the command, like ``look``.
   This should (ideally) be unique. A key can consist of more than one
   word, like "press button" or "pull left lever".
-  ``aliases`` (optional list) - a list of alternate names for the
   command (``["l", "glance", "see"]``). Same name rules as for ``key``
   applies.
-  ``locks`` (string) - a `lock definition <Locks.html>`_, usually on
   the form ``cmd:<lockfuncs>``. Locks is a rather big topic, so until
   you learn more about locks, stick to giving the lockstring
   ``"cmd:all()"`` to make the command available to everyone (if you
   don't put a lock string, this will be assigned for you).
-  ``help_category`` (optional string) - setting this helps to structure
   the auto-help into categories. If none is set, this will be set to
   *General*.
-  ``save_for_next`` (optional boolean). This defaults to ``False``. If
   ``True``, a copy of this command object (along with any changes you
   have done to it) will be stored by the system and can be accessed by
   the next command by retrieving ``self.caller.ndb.last_cmd``. The next
   run command will either clear or replace the storage.
-  'arg\_regex' (optional raw string): This should be given as a `raw
   regular expression string <http://docs.python.org/library/re.html>`_.
   The regex will be compiled by the system at runtime. This allows you
   to customize how the part *immediately following* the command name
   (or alias) must look in order for the parser to match for this
   command. Normally the parser is highly efficient in picking out the
   command name, also as the beginning of a longer word (as long as the
   longer word is not a command name in it self). So ``"lookme"`` will
   be parsed as the command ``"look"`` followed by the argument
   ``"me"``. By using ``arg_regex`` you could for example force the
   parser to require a space to follow the command name (regex string
   for this would be ``r"\s.*?|$"``). In that case, only ``"look me"``
   will work whereas ``"lookme"`` will lead to an "command not found"
   error.
-  ``func_parts`` (optional list of methods). Not defined by default,
   used if it exists. This list of methods will be called in sequence,
   each given a chance to yield execution. This allows for multi-part
   long-running commands. See `Commands with a
   Duration <CommandDuration.html>`_ for a practial presentation of how
   to use this.
-  ``auto_help`` (optional boolean). Defaults to ``True``. This allows
   for turning off the
   [`HelpSystem <HelpSystem.html>`_\ #Command\_Auto-help\_system
   auto-help system] on a per-command basis. This could be useful if you
   either want to write your help entries manually or hide the existence
   of a command from ``help``'s generated list.

You should also implement at least two methods, ``parse()`` and
``func()`` (You could also implement ``perm()``, but that's not needed
unless you want to fundamentally change how access checks work).

``parse()`` is intended to parse the arguments (``self.args``) of the
function. You can do this in any way you like, then store the result(s)
in variable(s) on the command object itself (i.e. on ``self``). To take
an example, the default mux-like system uses this method to detect
"command switches" and store them as a list in ``self.switches``. Since
the parsing is usually quite similar inside a command scheme you should
make ``parse()`` as generic as possible and then inherit from it rather
than re-implementing it over and over. In this way, the default
``MuxCommand`` class implements a ``parse()`` for all child commands to
use.

``func()`` is called right after ``parse()`` and should make use of the
pre-parsed input to actually do whatever the command is supposed to do.
This is the main body of the command.

Finally, you should always make an informative `doc
string <http://www.python.org/dev/peps/pep-0257/#what-is-a-docstring>`_
(``__doc__``) at the top of your class. This string is dynamically read
by the `Help system <HelpSystem.html>`_ to create the help entry for
this command. You should decide on a way to format your help and stick
to that.

Below is how you define a simple alternative "``smile``\ " command:

::

    from ev import Command

    class CmdSmile(Command):
        """
        A smile command

        Usage: 
          smile [at] [<someone>]
          grin [at] [<someone>] 

        Smiles to someone in your vicinity or to the room
        in general.

        (This initial string (the __doc__ string)
        is also used to auto-generate the help 
        for this command)
        """ 
      
        key = "smile"
        aliases = ["smile at", "grin", "grin at"] 
        locks = "cmd:all()"
        help_category = "General"
      
        def parse(self):
            "Very trivial parser" 
            self.target = self.args.strip() 

        def func(self):
            "This actually does things"
            caller = self.caller
            if not self.target or self.target == "here":
                string = "%s smiles." % caller.name
                caller.location.msg_contents(string, exclude=caller)
                caller.msg("You smile.")
            else:
                target = caller.search(self.target)
                if not target: 
                    # caller.search handles error messages
                    return
                string = "%s smiles to you." % caller.name
                target.msg(string)
                string = "You smile to %s." % target.name
                caller.msg(string)
                string = "%s smiles to %s." % (caller.name, target.name)           
                caller.location.msg_contents(string, exclude=[caller,target])

The power of having commands as classes and to separate ``parse()`` and
``func()`` lies in the ability to inherit functionality without having
to parse every command individually. For example, as mentioned the
default commands all inherit from ``MuxCommand``. ``MuxCommand``
implements its own version of ``parse()`` that understands all the
specifics of MUX-like commands. Almost none of the default commands thus
need to implement ``parse()`` at all, but can assume the incoming string
is already split up and parsed in suitable ways by its parent.

Command Sets
------------

All commands in Evennia are always grouped together into *Command Sets*
(CmdSets). A particular ``Command`` class definition can be part of any
number of different CmdSets. CmdSets can be stored either on game
`Sessions <Sessions.html>`_, `Objects <Objects.html>`_ or on
`Players <Players.html>`_.

When a user issues a command, it is matched against the contents of all
cmdsets available to the user at the moment,
[Commands#Adding\_and\_merging\_command\_sets merged together]. The
currently valid command sets are collected from the following sources,
in this order:

-  The active cmdset on the character object
-  The cmdsets of objects carried by the character
-  The cmdset of the current location
-  The cmdset(s) of objects in the current location (this includes
   exits)
-  The channel commandset
-  The cmdset defined on the Player object controlling the character

The default ``CmdSet`` shipping with Evennia is automatically added to
all new characters and contains commands such as ``look``, ``drop``,
``@dig`` etc. You can find it defined in
``src/commands/default/cmdset_character.py``, but it is also referenced
by importing ``ev.default_cmds`` and accessing its property
``CharacterCmdset``. Players have a cmdset called ``PlayerCmdSet`` that
can also be found from the same place. There is finally an "unloggedin"
cmdset, "UnloggedinCmdSet", that is used before the Player has
authenticated to the game. The path to these three standard command sets
are defined in settings, as ``CMDSET_UNLOGGEDIN``, ``CMDSET_CHARACTER``
and ``CMDSET_PLAYER``. You can create any number of command sets besides
those to fit your needs.

A CmdSet is, as most things in Evennia, defined as a Python class
inheriting from the correct parent (``ev.CmdSet`` or
``src.commands.cmdset.CmdSet``). The CmdSet class only needs to define
one method, called ``at_cmdset_creation()``. All other class parameters
are optional, but are used for more advanced set manipulation and coding
(see the [Commands#Merge\_rules merge rules] section).

::

    from ev import CmdSet
    from game.gamesrc.commands import mycommands
    class MyCmdSet(CmdSet):    
        def at_cmdset_creation(self):
            """
            The only thing this method should need
            to do is to add commands to the set.                                        
            """     
            self.add(mycommands.MyCommand1())
            self.add(mycommands.MyCommand2())
            self.add(mycommands.MyCommand3())       

The CmdSet's ``add()`` method can also take another CmdSet as input. In
this case all the commands from that CmdSet will be appended to this one
as if you added them line by line:

::

       at_cmdset_creation(): 
           ...
           self.add(AdditionalCmdSet) # adds all command from this set
           ...

If you added your command to an existing cmdset (like to the default
cmdset), that set is already loaded into memory. You need to make the
server aware of the code changes:

::

    @reload 

You should now be able to use the command.

If you created a new, fresh cmdset, this must be added to an object in
order to make the commands within available. A simple way to temporarily
test a cmdset on yourself is use the ``@py`` command to execute a python
snippet:

::

    @py self.cmdset.add('game.gamesrc.commands.mycmdset.MyCmdSet')

This will stay with you until you ``@reset`` or ``@shutdown`` the
server, or you run

::

    @py self.cmdset.delete('game.gamesrc.commands.mycmdset.MyCmdSet')

For a quick tutorial on setting up things more permanently read the
`Step by step
tutorial <http://code.google.com/p/evennia/wiki/AddingCommandTutorial>`_
for a different way of approaching it. Generally you can customize which
command sets are added to your objects by using ``self.cmdset.add()`` or
``self.cmdset.add_default()``.

Properties on command sets
~~~~~~~~~~~~~~~~~~~~~~~~~~

There are a few extra flags one can set on CmdSets in order to modify
how they work. All are optional and will be set to defaults otherwise.
Since many of these relate to *merging* cmdsets you might want to read
up on [Commands#Adding\_and\_merging\_command\_sets next section] for
some of these to make sense.

-  ``key`` (string) - an identifier for the cmdset. This is optional but
   should be unique; it is used for display in lists but also to
   identify special merging behaviours using the
   ``key_mergetype' dictionary below.  * ``\ mergetype\ `` (string) - one of "_Union_", "_Intersect_", "_Replace_" or "_Remove_".  * ``\ priority\ `` (int) - Higher priority sets will take priority during merging. Evennia default sets have priorities between ``\ 0\ `` and ``\ 9\ ``, where ``\ 0\ `` are most commands and ``\ 8\ `` or ``\ 9\ `` are used for special things like channel-commands and exit-commands.  * ``\ key\_mergetype\ `` (dict) - a dict of ``\ key:mergetype\ `` pairs. This allows this cmdset to merge differently with certain named cmdsets. If the cmdset to merge with has a ``\ key\ `` matching an entry in ``\ key\_mergetype\ ``, it will not be merged according to the setting in ``\ mergetype\ `` but according to the mode in this dict.   * ``\ duplicates\ `` (bool, default False) - when merging same-priority cmdsets containing same-key commands, the cmdset being merged "onto" the old one will take precedence. The result will be unique commands. If this flag is set the merged set can have multiple commands with the same key. This will usually lead to multi-match errors for the player. This is is useful e.g. for on-object cmdsets (example: There is a ``\ red
   button\ `` and a ``\ green
   button\ `` in the room. Both have a ``\ press
   button\ `` command, in cmdsets with the same priority. This flag makes sure that just writing ``\ press
   button\ `` will force the Player to define just which object's command was intended).   * ``\ no\_objs\ `` this is a flag for the cmdhandler that builds the set of commands available at every moment. It tells the handler not to include cmdsets from objects around the player (nor from rooms) when building the merged set. Exit commands will still be included.  * ``\ no\_exits\ `` - this is a flag for the cmdhandler that builds the set of commands available at every moment. It tells the handler not to include cmdsets from exits.  * ``\ is\_exit\ `` (bool) - this marks the cmdset as being used for an in-game exit. This allows the cmdhandler to easily disregard this cmdset when other cmdsets have their ``\ no\_exits\ `` flag set. It is set directly by the Exit object as part of initializing its cmdset.  * ``\ no\_channels\ `` (bool) - this is a flag for the cmdhandler that builds the set of commands available at every moment. It tells the handler not to include cmdsets from available in-game channels.  * ``\ is\_channel\ `` (bool)- this marks the cmdset as being used for an in-game exit. It allows the cmdhandler to easily disregard this cmdset when other cmdsets have their ``\ no\_channels\ `` flag set. It is set directly by the Channel object as part of initializing its cmdset.  == Default command sets ==   Evennia comes with four default cmdsets, used at different parts of the game. You can freely add more and/or expand on these as you see fit.    * _DefaultUnloggedin_ (``\ src.commands.default.cmdset\_unloggedin.UnloggedinCmdSet\ ``) - this cmdset holds the commands used before you have authenticated to the server, such as the login screen, connect, create character and so on.   * _DefaultSession_ (``\ src.commands.default.cmdset\_session.SessionCmdSet\ `` - this is stored on the [Session] once authenticated. This command set holds no commands by default. It is meant to hold session-specific OOC things, such as character-creation systems.   * _DefaultPlayer_ (``\ src.commands.default.cmdset\_player.PlayerCmdSet\ ``) - this is stored on the [Player] and contains account-centric OOC commands, such as the commands for sending text to channels or admin commands for staff.   * _DefaultCharacter_ (``\ src.commands.default.cmdset\_character.CharacterCmdSet\ ``) - this is finally stored on Character objects and holds all IC commands available to that Character. This is the biggest cmdset. For it to be available to the player, the Character must be puppeted.   Except for the unloggedin cmdset, cmdsets stored on these various levels dre merged "downward" in the connection hierarchy. So when merging (with the same priority), Session cmdsets are merged first, followed by Player and finally Character (so Character command overrule Player commands which overrule Session commands as it were). See the next section for details about merge rules.   ==Adding and merging command sets ==  _Note: This is an advanced topic. It's useful to know about, but you might want to skip it if this is your first time learning about commands._  !CmdSets have the special ability that they can be _merged_ together into new sets. This would happen if you, for example, did ``\ object.cmdset.add(MyCmdSet)\ `` on an object that already had a command set defined on it. The two sets will be evaluated and a temporary, _merged set_ will be created out of the commands in both sets. Only the commands in this merged set is from that point available to use. Which of the ingoing commands end up in the merged set is defined by the _merge rule_ and the relative _priorities_ of the two sets. Removing the latest added set will restore things back to the way it was before the addition.  !CmdSets are non-destructively stored in a stack inside the cmdset handler on the object. This stack is parsed to create the "combined" cmdset active at the moment. The very first cmdset in this stack is called the _Default cmdset_ and is protected from accidental deletion. Running ``\ obj.cmdset.delete()\ `` will never delete the default set. Instead one should add new cmdsets on top of th
   A2\ `` for set *A* and ``\ B1, B2, B3,
   B4\ `` for *B*. So for that example both sets contain commands with the same keys 1 and 2, whereas commands 3 and 4 are unique to *B*. To describe a merge between these sets, we would write {{{A1,A2 + B1,B2,B3,B4 = ?}}} where ``?\ `` is a list of commands that depend on which merge type *A* has, and which relative priorities the two sets have. By convention, we read this statement as "New command set *A* is merged onto the old command set *B* to form *?*".  Below are the available merge types and how they work. Names are partly borrowed from [http://en.wikipedia.org/wiki/Set_theory Set theory].  *Union* (default) - The two cmdsets are merged so that as many commands as possible from each cmdset ends up in the merged cmdset. Same-key commands are merged by priority.  {{{ # Union A1,A2 + B1,B2,B3,B4 = A1,A2,B3,B4 }}}  *Intersect* - Only commands found in _both_ cmdsets (i.e. which have the same keys) end up in the merged cmdset, with the higher-priority cmdset replacing the lower one's commands.   {{{ # Intersect  A1,A3,A5 + B1,B2,B4,B5 = A1,A5 }}} *Replace* -   The commands of the higher-prio cmdset completely replaces the lower-priority cmdset's commands, regardless of if same-key commands exist or not.  {{{ # Replace A1,A3 + B1,B2,B4,B5 = A1,A3 }}} *Remove* - The high-priority command sets removes same-key commands from the lower-priority cmdset. They are not replaced with anything, so this is a sort of filter that prunes the low-prio set using the high-prio one as a template.  {{{ # Remove A1,A3 + B1,B2,B3,B4,B5 = B2,B4,B5 }}}  Besides ``\ priority\ `` and ``\ mergetype\ ``, a command set also takes a few other variables to control how they merge:            * _duplicates_ (bool) - determines what happens when two sets of equal      priority merge. Default is that the new set in the merger  (i.e. *A* above) automatically takes precedence. But if _duplicates_ is true, the result will be a merger with more than one of each name match.  This will usually lead to the player                      receiving a multiple-match error higher up the road,                      but can be good for things like cmdsets on non-player                     objects in a room, to allow the system to warn that                      more than one 'ball' in the room has the same 'kick'                      command defined on it, so it may offer a chance to                     select which ball to kick ...  Allowing duplicates                      only makes sense for _Union_ and _Intersect_, the setting                     is ignored for the other mergetypes.     * _key_mergetypes_ (dict) - allows the cmdset to define a unique                  mergetype for particular cmdsets, identified by their cmdset-key.  Format is ``\ {CmdSetkey:mergetype}``. Priorities still apply.                 Example: ``\ {'Myevilcmdset','Replace'}\ `` which would make                  sure for this set to always use 'Replace' on                 ``\ Myevilcmdset\ `` only, no matter what _mergetype_ is set to.  More advanced cmdset example:  {{{ class MyCmdSet(CmdSet):      key = "MyCmdSet"     priority = 4     mergetype = "Replace"     key_mergetypes = {'MyOtherCmdSet':'Union'}        def at_cmdset_creation(self):         """         The only thing this method should need         to do is to add commands to the set.                                                 """              self.add(mycommands.MyCommand1())         self.add(mycommands.MyCommand2())         self.add(mycommands.MyCommand3())        }}}  == System commands ==  _Note: This is an advanced topic. Skip it if this is your first time learning about commands._  There are several command-situations that are exceptional in the eyes of the server. What happens if the player enters an empty string? What if the 'command' given is infact the name of a channel the user wants  to send a message to? Or if there are multiple command possibilities?  Such 'special cases' are handled by what's called  _system commands_. A system command is defined in the same way as other commands, except that their name (key) mus
   class variable can be used to implement state-persistent commands.
   For example it can make a command operate on "it", where it is
   determined by what the previous command operated on.**