evennia/src/cmdhandler.py

"""
This is the command processing module. It is instanced once in the main
server module and the handle() function is hit every time a player sends
something.
"""
from traceback import format_exc
import time

from src.objects.models import Object
import defines_global
import cmdtable
import logger
import comsys

class UnknownCommand(Exception):
    """
    Throw this when a user enters an an invalid command.
    """
    pass
class ExitCommandHandler(Exception):
    """
    Thrown when something happens and it's time to exit the command handler.
    """
    pass
    
class Command(object):
    # Reference to the master server object.
    server = None
    # The player session that the command originated from.
    session = None
    # The entire raw, un-parsed command.
    raw_input = None
    # Just the root command. IE: if input is "look dog", this is just "look".
    command_string = None
    # A list of switches in the form of strings.
    command_switches = []
    # The un-parsed argument provided. IE: if input is "look dog", this is "dog".
    command_argument = None
    # A reference to the command function looked up in a command table.
    command_function = None
    
    def parse_command_switches(self):
        """
        Splits any switches out of a command_string into the command_switches
        list, and yanks the switches out of the original command_string.
        """
        splitted_command = self.command_string.split('/')
        self.command_switches = splitted_command[1:]
        self.command_string = splitted_command[0]
    
    def parse_command(self):
        """
        Breaks the command up into the main command string, a list of switches,
        and a string containing the argument provided with the command. More
        specific processing is left up to the individual command functions.
        """
        try:
            """
            Break the command in half into command and argument. If the
            command string can't be parsed, it has no argument and is
            handled by the except ValueError block below.
            """
            (self.command_string, self.command_argument) = self.raw_input.split(' ', 1)
            self.command_argument = self.command_argument.strip()
            self.command_string = self.command_string.strip()
            """
            This is a really important behavior to note. If the user enters
            anything other than a string with some character in it, the value
            of the argument is None, not an empty string.
            """
            if self.command_string == '':
                self.command_string = None
            if self.command_argument == '':
                self.command_argument = None 
        except ValueError:
            """
            No arguments. IE: look, who.
            """
            self.command_string = self.raw_input

        # Parse command_string for switches, regardless of what happens.
        self.parse_command_switches()
    
    def __init__(self, raw_input, server=None, session=None):
        """
        Instantiates the Command object and does some preliminary parsing.
        """
        self.server = server
        self.raw_input = raw_input
        self.session = session
        # The work starts here.
        self.parse_command()
        
    def arg_has_target(self):
        """
        Returns true if the argument looks to be target-style. IE:
        page blah=hi
        kick ball=north
        """
        return "=" in self.command_argument
    
    def get_arg_targets(self, delim=','):
        """
        Returns a list of targets from the argument. These happen before
        the '=' sign and may be separated by a delimiter.
        """
        # Make sure we even have a target (= sign).
        if not self.arg_has_target():
            return None
        
        target = self.command_argument.split('=', 1)[0]
        return [targ.strip() for targ in target.split(delim)]
    
    def get_arg_target_value(self):
        """
        In a case of something like: page bob=Hello there, the target is "bob",
        while the value is "Hello there". This function returns the portion
        of the command that takes place after the first equal sign.
        """
        # Make sure we even have a target (= sign).
        if not self.arg_has_target():
            return None
        
        return self.command_argument.split('=', 1)[1]

def match_idle(command):
    """
    Matches against the 'idle' command. It doesn't actually do anything, but it
    lets the users get around badly configured NAT timeouts that would cause
    them to drop if they don't send or receive something from the connection
    for a while.
    """
    if not command.command_string == 'idle':
        # Anything other than an 'idle' command updates the public-facing idle
        # time for the session.
        command.session.count_command(silently=False)
    else:
        # User is hitting IDLE command. Don't update their publicly
        # facing idle time, drop out of command handler immediately.
        command.session.count_command(silently=True)
        raise ExitCommandHandler

def match_exits(command):
    """
    See if we can find an input match to exits.
    """
    # If we're not logged in, don't check exits.
    pobject = command.session.get_pobject()
    exits = pobject.get_location().get_contents(filter_type=defines_global.OTYPE_EXIT)
    exit_matches = Object.objects.list_search_object_namestr(exits, 
                                                     command.command_string, 
                                                     match_type="exact")
    if exit_matches:
        # Only interested in the first match.
        targ_exit = exit_matches[0]
        # An exit's home is its destination. If the exit has a None home value,
        # it's not traversible.
        if targ_exit.get_home():                   
            # SCRIPT: See if the player can traverse the exit
            if not targ_exit.scriptlink.default_lock({
                "pobject": pobject
            }):
                command.session.msg("You can't traverse that exit.")
            else:
                pobject.move_to(targ_exit.get_home())
                # Force the player to 'look' to see the description.
                command.session.execute_cmd("look")
        else:
            command.session.msg("That exit leads to nowhere.")
        # We found a match, kill the command handler.
        raise ExitCommandHandler

def match_alias(command):
    """
    Checks to see if the entered command matches an alias. If so, replaces
    the command_string with the correct command.

    We do a dictionary lookup. If the key (the player's command_string) doesn't 
    exist on the dict, just keep the command_string the same. If the key exists, 
    its value replaces the command_string. For example, sa -> say.
    """
    command.command_string = command.server.cmd_alias_list.get(
                                            command.command_string,
                                            command.command_string)
    
def match_channel(command):
    """
    Match against a comsys channel or comsys command. If the player is talking
    over a channel, replace command_string with @cemit. If they're entering
    a channel manipulation command, perform the operation and kill the things
    immediately with a True value sent back to the command handler.
    """
    if comsys.plr_has_channel(command.session, command.command_string, 
        alias_search=True, return_muted=True):
        
        calias = command.command_string
        cname = comsys.plr_cname_from_alias(command.session, calias)
        
        if command.command_argument == "who":
            comsys.msg_cwho(command.session, cname)
            raise ExitCommandHandler
        elif command.command_argument == "on":
            comsys.plr_chan_on(command.session, calias)
            raise ExitCommandHandler
        elif command.command_argument == "off":
            comsys.plr_chan_off(command.session, calias)
            raise ExitCommandHandler
        elif command.command_argument == "last":
            comsys.msg_chan_hist(command.session, cname)
            ExitCommandHandler
            
        second_arg = "%s=%s" % (cname, command.command_argument)
        command.command_string = "@cemit"
        command.command_switches = ["sendername", "quiet"]
        
def command_table_lookup(command, command_table, eval_perms=True):
    """
    Performs a command table lookup on the specified command table. Also
    evaluates the permissions tuple.
    """
    # Get the command's function reference (Or False)
    cmdtuple = command_table.get_command_tuple(command.command_string)
    if cmdtuple:
        # If there is a permissions element to the entry, check perms.
        if eval_perms and cmdtuple[1]:
            if not command.session.get_pobject().user_has_perm_list(cmdtuple[1]):
                command.session.msg(defines_global.NOPERMS_MSG)
                raise ExitCommandHandler
        # If flow reaches this point, user has perms and command is ready.
        command.command_function = cmdtuple[0]

def handle(command):
    """
    Use the spliced (list) uinput variable to retrieve the correct
    command, or return an invalid command error.

    We're basically grabbing the player's command by tacking
    their input on to 'cmd_' and looking it up in the GenCommands
    class.
    """
    session = command.session
    server = command.server
    
    try:
        # TODO: Protect against non-standard characters.
        if not command.command_string:
            # Nothing sent in of value, ignore it.
            raise ExitCommandHandler

        if session.logged_in:
            # Match against the 'idle' command.
            match_idle(command)
            # See if this is an aliased command.
            match_alias(command)
            # Check if the user is using a channel command.
            match_channel(command)
            # See if the user is trying to traverse an exit.
            match_exits(command)
            # Retrieve the appropriate (if any) command function.
            command_table_lookup(command, cmdtable.GLOBAL_CMD_TABLE)
        else:
            # Not logged in, look through the unlogged-in command table.
            command_table_lookup(command, cmdtable.GLOBAL_UNCON_CMD_TABLE, 
                                 eval_perms=False)
        
        """
        By this point, we assume that the user has entered a command and not
        something like a channel or exit. Make sure that the command's
        function reference is value and try to run it.
        """
        if callable(command.command_function):
            try:
                # Move to the command function, passing the command object.
                command.command_function(command)
            except:
                """
                This is a crude way of trapping command-related exceptions
                and showing them to the user and server log. Once the
                codebase stabilizes, we will probably want something more
                useful or give them the option to hide exception values.
                """
                session.msg("Untrapped error, please file a bug report:\n%s" % 
                    (format_exc(),))
                logger.log_errmsg("Untrapped error, evoker %s: %s" %
                    (session, format_exc()))
                # Prevent things from falling through to UnknownCommand.
                raise ExitCommandHandler
        else:
            # If we reach this point, we haven't matched anything.     
            raise UnknownCommand

    except ExitCommandHandler:
        # When this is thrown, just get out and do nothing. It doesn't mean
        # something bad has happened.
        pass
    except UnknownCommand:
        # Default fall-through. No valid command match.
        session.msg("Huh?  (Type \"help\" for help.)")