gajim-plural/gajim/command_system/framework.py

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# Copyright (C) 2009-2010 Alexander Cherniuk <ts33kr@gmail.com>
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program. If not, see <http://www.gnu.org/licenses/>.
"""
Provides a tiny framework with simple, yet powerful and extensible
architecture to implement commands in a straight and flexible,
declarative way.
"""
from types import FunctionType
from inspect import getargspec, getdoc
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from gajim.command_system.dispatcher import Host, Container
from gajim.command_system.dispatcher import get_command, list_commands
from gajim.command_system.mapping import parse_arguments, adapt_arguments
from gajim.command_system.errors import DefinitionError, CommandError, NoCommandError
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class CommandHost(metaclass=Host):
"""
Command host is a hub between numerous command processors and
command containers. Aimed to participate in a dispatching process in
order to provide clean and transparent architecture.
The AUTOMATIC class variable, which must be defined by a command
host, specifies whether the command host should be automatically
dispatched and enabled by the dispatcher or not.
"""
__metaclass__ = Host
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class CommandContainer(metaclass=Container):
"""
Command container is an entity which holds defined commands,
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allowing them to be dispatched and processed correctly. Each
command container may be bound to a one or more command hosts.
The AUTOMATIC class variable, which must be defined by a command
processor, specifies whether the command processor should be
automatically dispatched and enabled by the dispatcher or not.
Bounding is controlled by the HOSTS class variable, which must be
defined by the command container. This variable should contain a
sequence of hosts to bound to, as a tuple or list.
"""
__metaclass__ = Container
class CommandProcessor:
"""
Command processor is an immediate command emitter. It does not
participate in the dispatching process directly, but must define a
host to bound to.
Bounding is controlled by the COMMAND_HOST variable, which must be
defined in the body of the command processor. This variable should
be set to a specific command host.
"""
# This defines a command prefix (or an initializer), which should
# precede a text in order for it to be processed as a command.
COMMAND_PREFIX = '/'
def process_as_command(self, text):
"""
Try to process text as a command. Returns True if it has been
processed as a command and False otherwise.
"""
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# pylint: disable=assignment-from-no-return
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prefix = text.startswith(self.COMMAND_PREFIX)
length = len(text) > len(self.COMMAND_PREFIX)
if not (prefix and length):
return False
body = text[len(self.COMMAND_PREFIX):]
body = body.strip()
parts = body.split(None, 1)
name, arguments = parts if len(parts) > 1 else (parts[0], None)
flag = self.looks_like_command(text, body, name, arguments)
if flag is not None:
return flag
self.execute_command(name, arguments)
return True
def execute_command(self, name, arguments):
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cmd = self.get_command(name)
args, opts = parse_arguments(arguments) if arguments else ([], [])
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args, kwargs = adapt_arguments(cmd, arguments, args, opts)
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if self.command_preprocessor(cmd, name, arguments, args, kwargs):
return
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value = cmd(self, *args, **kwargs)
self.command_postprocessor(cmd, name, arguments, args, kwargs, value)
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def command_preprocessor(self, cmd, name, arguments, args, kwargs):
"""
Redefine this method in the subclass to execute custom code
before command gets executed.
If returns True then command execution will be interrupted and
command will not be executed.
"""
pass
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def command_postprocessor(self, cmd, name, arguments, args, kwargs, value):
"""
Redefine this method in the subclass to execute custom code
after command gets executed.
"""
pass
def looks_like_command(self, text, body, name, arguments):
"""
This hook is being called before any processing, but after it
was determined that text looks like a command.
If returns value other then None - then further processing will
be interrupted and that value will be used to return from
process_as_command.
"""
pass
def get_command(self, name):
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cmd = get_command(self.COMMAND_HOST, name)
if not cmd:
raise NoCommandError("Command does not exist", name=name)
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return cmd
def list_commands(self):
commands = list_commands(self.COMMAND_HOST)
commands = dict(commands)
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return sorted(set(commands.values()), key=lambda k: k.__repr__())
class Command:
def __init__(self, handler, *names, **properties):
self.handler = handler
self.names = names
# Automatically set all the properties passed to a constructor
# by the command decorator.
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for key, value in properties.items():
setattr(self, key, value)
def __call__(self, *args, **kwargs):
try:
return self.handler(*args, **kwargs)
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# This allows to use a shortcut way of raising an exception
# inside a handler. That is to raise a CommandError without
# command or name attributes set. They will be set to a
# corresponding values right here in case if they was not set by
# the one who raised an exception.
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except CommandError as error:
if not error.command and not error.name:
raise CommandError(error.message, self)
raise
# This one is a little bit too wide, but as Python does not have
# anything more constrained - there is no other choice. Take a
# look here if command complains about invalid arguments while
# they are ok.
except TypeError:
raise CommandError("Command received invalid arguments", self)
def __repr__(self):
return "<Command %s>" % ', '.join(self.names)
def __cmp__(self, other):
if self.first_name > other.first_name:
return 1
if self.first_name < other.first_name:
return -1
return 0
@property
def first_name(self):
return self.names[0]
@property
def native_name(self):
return self.handler.__name__
def extract_documentation(self):
"""
Extract handler's documentation which is a doc-string and
transform it to a usable format.
"""
return getdoc(self.handler)
def extract_description(self):
"""
Extract handler's description (which is a first line of the
documentation). Try to keep them simple yet meaningful.
"""
documentation = self.extract_documentation()
return documentation.split('\n', 1)[0] if documentation else None
def extract_specification(self):
"""
Extract handler's arguments specification, as it was defined
preserving their order.
"""
names, var_args, var_kwargs, defaults = getargspec(self.handler) # pylint: disable=W1505
# Behavior of this code need to be checked. Might yield
# incorrect results on some rare occasions.
spec_args = names[:-len(defaults) if defaults else len(names)]
spec_kwargs = list(zip(names[-len(defaults):], defaults)) if defaults else {}
# Removing self from arguments specification. Command handler
# should receive the processors as a first argument, which
# should be self by the canonical means.
if spec_args.pop(0) != 'self':
raise DefinitionError("First argument must be self", self)
return spec_args, spec_kwargs, var_args, var_kwargs
def command(*names, **properties):
"""
A decorator for defining commands in a declarative way. Provides
facilities for setting command's names and properties.
Names should contain a set of names (aliases) by which the command
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can be reached. If no names are given - the native name (the one
extracted from the command handler) will be used.
If native=True is given (default) and names is non-empty - then the
native name of the command will be prepended in addition to the
given names.
If usage=True is given (default) - then command help will be
appended with autogenerated usage info, based of the command handler
arguments introspection.
If source=True is given - then the first argument of the command
will receive the source arguments, as a raw, unprocessed string. The
further mapping of arguments and options will not be affected.
If raw=True is given - then command considered to be raw and should
define positional arguments only. If it defines only one positional
argument - this argument will receive all the raw and unprocessed
arguments. If the command defines more then one positional argument
- then all the arguments except the last one will be processed
normally; the last argument will get what is left after the
processing as raw and unprocessed string.
If empty=True is given - this will allow to call a raw command
without arguments.
If extra=True is given - then all the extra arguments passed to a
command will be collected into a sequence and given to the last
positional argument.
If overlap=True is given - then all the extra arguments will be
mapped as if they were values for the keyword arguments.
If expand=True is given (default) - then short, one-letter options
will be expanded to a verbose ones, based of the comparison of the
first letter. If more then one option with the same first letter is
given - then only first one will be used in the expansion.
"""
names = list(names)
native = properties.get('native', True)
usage = properties.get('usage', True)
source = properties.get('source', False)
raw = properties.get('raw', False)
empty = properties.get('empty', False)
extra = properties.get('extra', False)
overlap = properties.get('overlap', False)
expand = properties.get('expand', True)
if empty and not raw:
raise DefinitionError("Empty option can be used only with raw commands")
if extra and overlap:
raise DefinitionError("Extra and overlap options can not be used together")
properties = {
'usage': usage,
'source': source,
'raw': raw,
'extra': extra,
'overlap': overlap,
'empty': empty,
'expand': expand
}
def decorator(handler):
"""
Decorator which receives handler as a first argument and then
wraps it in the command which then returns back.
"""
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cmd = Command(handler, *names, **properties)
# Extract and inject a native name if either no other names are
# specified or native property is enabled, while making
# sure it is going to be the first one in the list.
if not names or native:
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names.insert(0, cmd.native_name)
cmd.names = tuple(names)
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return cmd
# Workaround if we are getting called without parameters. Keep in
# mind that in that case - first item in the names will be the
# handler.
if names and isinstance(names[0], FunctionType):
return decorator(names.pop(0))
return decorator
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def doc(text):
"""
This decorator is used to bind a documentation (a help) to a
command.
"""
def decorator(target):
if isinstance(target, Command):
target.handler.__doc__ = text
else:
target.__doc__ = text
return target
return decorator