freeipa/ipalib/plugable.py

# Authors:
#   Jason Gerard DeRose <jderose@redhat.com>
#
# Copyright (C) 2008  Red Hat
# see file 'COPYING' for use and warranty information
#
# 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/>.

"""
Plugin framework.

The classes in this module make heavy use of Python container emulation. If
you are unfamiliar with this Python feature, see
http://docs.python.org/ref/sequence-types.html
"""

import re
import sys
import inspect
import threading
import os
from os import path
import subprocess
import optparse
import errors
import textwrap
import collections
import importlib

from config import Env
import text
from text import _
from base import ReadOnly, NameSpace, lock, islocked, check_name
from constants import DEFAULT_CONFIG
from ipapython.ipa_log_manager import *
from ipapython.version import VERSION, API_VERSION

# FIXME: Updated constants.TYPE_ERROR to use this clearer format from wehjit:
TYPE_ERROR = '%s: need a %r; got a %r: %r'

def is_production_mode(obj):
    """
    If the object has self.env.mode defined and that mode is
    production return True, otherwise return False.
    """
    if getattr(obj, 'env', None) is None:
        return False
    if getattr(obj.env, 'mode', None) is None:
        return False
    return obj.env.mode == 'production'


# FIXME: This function has no unit test
def find_modules_in_dir(src_dir):
    """
    Iterate through module names found in ``src_dir``.
    """
    if not (os.path.abspath(src_dir) == src_dir and os.path.isdir(src_dir)):
        return
    if os.path.islink(src_dir):
        return
    suffix = '.py'
    for name in sorted(os.listdir(src_dir)):
        if not name.endswith(suffix):
            continue
        pyfile = os.path.join(src_dir, name)
        if not os.path.isfile(pyfile):
            continue
        module = name[:-len(suffix)]
        if module == '__init__':
            continue
        yield module


class Registry(object):
    """A decorator that makes plugins available to the API

    Usage::

        register = Registry()

        @register()
        class obj_mod(...):
            ...

    For forward compatibility, make sure that the module-level instance of
    this object is named "register".
    """
    def __call__(self):
        def decorator(cls):
            API.register(cls)
            return cls

        return decorator


class SetProxy(ReadOnly):
    """
    A read-only container with set/sequence behaviour.

    This container acts as a proxy to an actual set-like object (a set,
    frozenset, or dict) that is passed to the constructor. To the extent
    possible in Python, this underlying set-like object cannot be modified
    through the SetProxy... which just means you wont do it accidentally.
    """
    def __init__(self, s):
        """
        :param s: The target set-like object (a set, frozenset, or dict)
        """
        allowed = (set, frozenset, dict)
        if type(s) not in allowed:
            raise TypeError('%r not in %r' % (type(s), allowed))
        self.__s = s
        if not is_production_mode(self):
            lock(self)

    def __len__(self):
        """
        Return the number of items in this container.
        """
        return len(self.__s)

    def __iter__(self):
        """
        Iterate (in ascending order) through keys.
        """
        for key in sorted(self.__s):
            yield key

    def __contains__(self, key):
        """
        Return True if this container contains ``key``.

        :param key: The key to test for membership.
        """
        return key in self.__s


class DictProxy(SetProxy):
    """
    A read-only container with mapping behaviour.

    This container acts as a proxy to an actual mapping object (a dict) that
    is passed to the constructor. To the extent possible in Python, this
    underlying mapping object cannot be modified through the DictProxy...
    which just means you wont do it accidentally.

    Also see `SetProxy`.
    """
    def __init__(self, d):
        """
        :param d: The target mapping object (a dict)
        """
        if type(d) is not dict:
            raise TypeError('%r is not %r' % (type(d), dict))
        self.__d = d
        super(DictProxy, self).__init__(d)

    def __getitem__(self, key):
        """
        Return the value corresponding to ``key``.

        :param key: The key of the value you wish to retrieve.
        """
        return self.__d[key]

    def __call__(self):
        """
        Iterate (in ascending order by key) through values.
        """
        for key in self:
            yield self.__d[key]


class MagicDict(DictProxy):
    """
    A mapping container whose values can be accessed as attributes.

    For example:

    >>> magic = MagicDict({'the_key': 'the value'})
    >>> magic['the_key']
    'the value'
    >>> magic.the_key
    'the value'

    This container acts as a proxy to an actual mapping object (a dict) that
    is passed to the constructor. To the extent possible in Python, this
    underlying mapping object cannot be modified through the MagicDict...
    which just means you wont do it accidentally.

    Also see `DictProxy` and `SetProxy`.
    """

    def __getattr__(self, name):
        """
        Return the value corresponding to ``name``.

        :param name: The name of the attribute you wish to retrieve.
        """
        try:
            return self[name]
        except KeyError:
            raise AttributeError('no magic attribute %r' % name)


class Plugin(ReadOnly):
    """
    Base class for all plugins.
    """

    finalize_early = True

    label = None

    def __init__(self):
        self.__api = None
        self.__finalize_called = False
        self.__finalized = False
        self.__finalize_lock = threading.RLock()
        cls = self.__class__
        self.name = cls.__name__
        self.module = cls.__module__
        self.fullname = '%s.%s' % (self.module, self.name)
        self.bases = tuple(
            '%s.%s' % (b.__module__, b.__name__) for b in cls.__bases__
        )
        self.doc = _(cls.__doc__)
        if not self.doc.msg:
            self.summary = '<%s>' % self.fullname
        else:
            self.summary = unicode(self.doc).split('\n\n', 1)[0].strip()
        log_mgr.get_logger(self, True)
        if self.label is None:
            self.label = text.FixMe(self.name + '.label')
        if not isinstance(self.label, text.LazyText):
            raise TypeError(
                TYPE_ERROR % (
                    self.fullname + '.label',
                    text.LazyText,
                    type(self.label),
                    self.label
                )
            )

    def __get_api(self):
        """
        Return `API` instance passed to `set_api()`.

        If `set_api()` has not yet been called, None is returned.
        """
        return self.__api
    api = property(__get_api)

    def finalize(self):
        """
        Finalize plugin initialization.

        This method calls `_on_finalize()` and locks the plugin object.

        Subclasses should not override this method. Custom finalization is done
        in `_on_finalize()`.
        """
        with self.__finalize_lock:
            assert self.__finalized is False
            if self.__finalize_called:
                # No recursive calls!
                return
            self.__finalize_called = True
            self._on_finalize()
            self.__finalized = True
            if not is_production_mode(self):
                lock(self)

    def _on_finalize(self):
        """
        Do custom finalization.

        This method is called from `finalize()`. Subclasses can override this
        method in order to add custom finalization.
        """
        pass

    def ensure_finalized(self):
        """
        Finalize plugin initialization if it has not yet been finalized.
        """
        with self.__finalize_lock:
            if not self.__finalized:
                self.finalize()

    class finalize_attr(object):
        """
        Create a stub object for plugin attribute that isn't set until the
        finalization of the plugin initialization.

        When the stub object is accessed, it calls `ensure_finalized()` to make
        sure the plugin initialization is finalized. The stub object is expected
        to be replaced with the actual attribute value during the finalization
        (preferably in `_on_finalize()`), otherwise an `AttributeError` is
        raised.

        This is used to implement on-demand finalization of plugin
        initialization.
        """
        __slots__ = ('name', 'value')

        def __init__(self, name, value=None):
            self.name = name
            self.value = value

        def __get__(self, obj, cls):
            if obj is None or obj.api is None:
                return self.value
            obj.ensure_finalized()
            try:
                return getattr(obj, self.name)
            except RuntimeError:
                # If the actual attribute value is not set in _on_finalize(),
                # getattr() calls __get__() again, which leads to infinite
                # recursion. This can happen only if the plugin is written
                # badly, so advise the developer about that instead of giving
                # them a generic "maximum recursion depth exceeded" error.
                raise AttributeError(
                    "attribute '%s' of plugin '%s' was not set in finalize()" % (self.name, obj.name)
                )

    def set_api(self, api):
        """
        Set reference to `API` instance.
        """
        assert self.__api is None, 'set_api() can only be called once'
        assert api is not None, 'set_api() argument cannot be None'
        self.__api = api
        if not isinstance(api, API):
            return
        for name in api:
            assert not hasattr(self, name)
            setattr(self, name, api[name])
        for name in ('env', 'context'):
            if hasattr(api, name):
                assert not hasattr(self, name)
                setattr(self, name, getattr(api, name))

    def call(self, executable, *args):
        """
        Call ``executable`` with ``args`` using subprocess.call().

        If the call exits with a non-zero exit status,
        `ipalib.errors.SubprocessError` is raised, from which you can retrieve
        the exit code by checking the SubprocessError.returncode attribute.

        This method does *not* return what ``executable`` sent to stdout... for
        that, use `Plugin.callread()`.
        """
        argv = (executable,) + args
        self.debug('Calling %r', argv)
        code = subprocess.call(argv)
        if code != 0:
            raise errors.SubprocessError(returncode=code, argv=argv)

    def __repr__(self):
        """
        Return 'module_name.class_name()' representation.

        This representation could be used to instantiate this Plugin
        instance given the appropriate environment.
        """
        return '%s.%s()' % (
            self.__class__.__module__,
            self.__class__.__name__
        )


class Registrar(collections.Mapping):
    """
    Collects plugin classes as they are registered.

    The Registrar does not instantiate plugins... it only implements the
    override logic and stores the plugins in a namespace per allowed base
    class.

    The plugins are instantiated when `API.finalize()` is called.
    """
    def __init__(self):
        self.__registry = collections.OrderedDict()

    def __call__(self, klass, override=False):
        """
        Register the plugin ``klass``.

        :param klass: A subclass of `Plugin` to attempt to register.
        :param override: If true, override an already registered plugin.
        """
        if not inspect.isclass(klass):
            raise TypeError('plugin must be a class; got %r' % klass)

        # Raise DuplicateError if this exact class was already registered:
        if klass in self.__registry:
            raise errors.PluginDuplicateError(plugin=klass)

        # The plugin is okay, add to __registry:
        self.__registry[klass] = dict(override=override)

    def __getitem__(self, key):
        return self.__registry[key]

    def __iter__(self):
        return iter(self.__registry)

    def __len__(self):
        return len(self.__registry)


class API(DictProxy):
    """
    Dynamic API object through which `Plugin` instances are accessed.
    """

    register = Registrar()

    def __init__(self, allowed, modules):
        self.__plugins = {base: {} for base in allowed}
        self.modules = modules
        self.__d = dict()
        self.__done = set()
        self.env = Env()
        super(API, self).__init__(self.__d)

    def __doing(self, name):
        if name in self.__done:
            raise StandardError(
                '%s.%s() already called' % (self.__class__.__name__, name)
            )
        self.__done.add(name)

    def __do_if_not_done(self, name):
        if name not in self.__done:
            getattr(self, name)()

    def isdone(self, name):
        return name in self.__done

    def bootstrap(self, parser=None, **overrides):
        """
        Initialize environment variables and logging.
        """
        self.__doing('bootstrap')
        self.env._bootstrap(**overrides)
        self.env._finalize_core(**dict(DEFAULT_CONFIG))
        object.__setattr__(self, 'log_mgr', log_mgr)
        log = log_mgr.root_logger
        object.__setattr__(self, 'log', log)

        # Add the argument parser
        if not parser:
            parser = self.build_global_parser()
        object.__setattr__(self, 'parser', parser)

        # If logging has already been configured somewhere else (like in the
        # installer), don't add handlers or change levels:
        if log_mgr.configure_state != 'default' or self.env.validate_api:
            return

        log_mgr.default_level = 'info'
        log_mgr.configure_from_env(self.env, configure_state='api')
        # Add stderr handler:
        level = 'info'
        if self.env.debug:
            level = 'debug'
        else:
            if self.env.context == 'cli':
                if self.env.verbose > 0:
                    level = 'info'
                else:
                    level = 'warning'

        if log_mgr.handlers.has_key('console'):
            log_mgr.remove_handler('console')
        log_mgr.create_log_handlers([dict(name='console',
                                          stream=sys.stderr,
                                          level=level,
                                          format=LOGGING_FORMAT_STDERR)])

        # Add file handler:
        if self.env.mode in ('dummy', 'unit_test'):
            return  # But not if in unit-test mode
        if self.env.log is None:
            return
        log_dir = path.dirname(self.env.log)
        if not path.isdir(log_dir):
            try:
                os.makedirs(log_dir)
            except OSError:
                log.error('Could not create log_dir %r', log_dir)
                return

        level = 'info'
        if self.env.debug:
            level = 'debug'
        try:
            log_mgr.create_log_handlers([dict(name='file',
                                              filename=self.env.log,
                                              level=level,
                                              format=LOGGING_FORMAT_FILE)])
        except IOError, e:
            log.error('Cannot open log file %r: %s', self.env.log, e)
            return

    def build_global_parser(self, parser=None, context=None):
        """
        Add global options to an optparse.OptionParser instance.
        """
        if parser is None:
            parser = optparse.OptionParser(
                add_help_option=False,
                formatter=IPAHelpFormatter(),
                usage='%prog [global-options] COMMAND [command-options]',
                description='Manage an IPA domain',
                version=('VERSION: %s, API_VERSION: %s'
                                % (VERSION, API_VERSION)),
                epilog='\n'.join([
                    'See "ipa help topics" for available help topics.',
                    'See "ipa help <TOPIC>" for more information on a '
                        'specific topic.',
                    'See "ipa help commands" for the full list of commands.',
                    'See "ipa <COMMAND> --help" for more information on a '
                        'specific command.',
                ]))
            parser.disable_interspersed_args()
            parser.add_option("-h", "--help", action="help",
                help='Show this help message and exit')

        parser.add_option('-e', dest='env', metavar='KEY=VAL', action='append',
            help='Set environment variable KEY to VAL',
        )
        parser.add_option('-c', dest='conf', metavar='FILE',
            help='Load configuration from FILE',
        )
        parser.add_option('-d', '--debug', action='store_true',
            help='Produce full debuging output',
        )
        parser.add_option('--delegate', action='store_true',
            help='Delegate the TGT to the IPA server',
        )
        parser.add_option('-v', '--verbose', action='count',
            help='Produce more verbose output. A second -v displays the XML-RPC request',
        )
        if context == 'cli':
            parser.add_option('-a', '--prompt-all', action='store_true',
                help='Prompt for ALL values (even if optional)'
            )
            parser.add_option('-n', '--no-prompt', action='store_false',
                dest='interactive',
                help='Prompt for NO values (even if required)'
            )
            parser.add_option('-f', '--no-fallback', action='store_false',
                dest='fallback',
                help='Only use the server configured in /etc/ipa/default.conf'
            )

        return parser

    def bootstrap_with_global_options(self, parser=None, context=None):
        parser = self.build_global_parser(parser, context)
        (options, args) = parser.parse_args()
        overrides = {}
        if options.env is not None:
            assert type(options.env) is list
            for item in options.env:
                try:
                    (key, value) = item.split('=', 1)
                except ValueError:
                    # FIXME: this should raise an IPA exception with an
                    # error code.
                    # --Jason, 2008-10-31
                    pass
                overrides[str(key.strip())] = value.strip()
        for key in ('conf', 'debug', 'verbose', 'prompt_all', 'interactive',
            'fallback', 'delegate'):
            value = getattr(options, key, None)
            if value is not None:
                overrides[key] = value
        if hasattr(options, 'prod'):
            overrides['webui_prod'] = options.prod
        if context is not None:
            overrides['context'] = context
        self.bootstrap(parser, **overrides)
        return (options, args)

    def load_plugins(self):
        """
        Load plugins from all standard locations.

        `API.bootstrap` will automatically be called if it hasn't been
        already.
        """
        self.__doing('load_plugins')
        self.__do_if_not_done('bootstrap')
        if self.env.mode in ('dummy', 'unit_test'):
            return
        for module in self.modules:
            self.import_plugins(module)

    # FIXME: This method has no unit test
    def import_plugins(self, module):
        """
        Import plugins from ``module``.

        :param module: Name of the module to import. This might be a wildcard
                       in the form ```package.*``` in which case all modules
                       from the given package are loaded.
        """
        if module.endswith('.*'):
            subpackage = module[:-2]
            try:
                plugins = importlib.import_module(subpackage)
            except ImportError, e:
                self.log.error("cannot import plugins sub-package %s: %s",
                               subpackage, e)
                raise
            package, dot, part = subpackage.rpartition('.')
            parent = sys.modules[package]

            parent_dir = path.dirname(path.abspath(parent.__file__))
            plugins_dir = path.dirname(path.abspath(plugins.__file__))
            if parent_dir == plugins_dir:
                raise errors.PluginsPackageError(
                    name=subpackage, file=plugins.__file__
                )

            self.log.debug("importing all plugin modules in %s...", subpackage)
            modules = find_modules_in_dir(plugins_dir)
            modules = ['.'.join((subpackage, name)) for name in modules]
        else:
            modules = [module]

        for name in modules:
            self.log.debug("importing plugin module %s", name)
            try:
                module = importlib.import_module(name)
            except errors.SkipPluginModule, e:
                self.log.debug("skipping plugin module %s: %s", name, e.reason)
            except StandardError, e:
                if self.env.startup_traceback:
                    import traceback
                    self.log.error("could not load plugin module %s\n%s", name,
                                   traceback.format_exc())
                raise
            else:
                self.add_module(module)

    def add_module(self, module):
        """
        Add plugins from the ``module``.

        :param module: A module from which to add plugins.
        """
        for name in dir(module):
            klass = getattr(module, name)
            if not inspect.isclass(klass):
                continue
            if klass not in self.register:
                continue
            kwargs = self.register[klass]
            self.add_plugin(klass, **kwargs)

    def add_plugin(self, klass, override=False):
        """
        Add the plugin ``klass``.

        :param klass: A subclass of `Plugin` to attempt to add.
        :param override: If true, override an already added plugin.
        """
        if not inspect.isclass(klass):
            raise TypeError('plugin must be a class; got %r' % klass)

        # Find the base class or raise SubclassError:
        found = False
        for (base, sub_d) in self.__plugins.iteritems():
            if not issubclass(klass, base):
                continue

            found = True

            if sub_d.get(klass.__name__) is klass:
                continue

            # Check override:
            if klass.__name__ in sub_d:
                if not override:
                    # Must use override=True to override:
                    raise errors.PluginOverrideError(
                        base=base.__name__,
                        name=klass.__name__,
                        plugin=klass,
                    )
            else:
                if override:
                    # There was nothing already registered to override:
                    raise errors.PluginMissingOverrideError(
                        base=base.__name__,
                        name=klass.__name__,
                        plugin=klass,
                    )

            # The plugin is okay, add to sub_d:
            sub_d[klass.__name__] = klass

        if not found:
            raise errors.PluginSubclassError(
                plugin=klass,
                bases=self.__plugins.keys(),
            )

    def finalize(self):
        """
        Finalize the registration, instantiate the plugins.

        `API.bootstrap` will automatically be called if it hasn't been
        already.
        """
        self.__doing('finalize')
        self.__do_if_not_done('load_plugins')

        production_mode = is_production_mode(self)
        plugins = {}
        plugin_info = {}

        for base, sub_d in self.__plugins.iteritems():
            name = base.__name__

            members = []
            for klass in sub_d.itervalues():
                try:
                    instance = plugins[klass]
                except KeyError:
                    instance = plugins[klass] = klass()
                members.append(instance)
                plugin_info.setdefault(
                    '%s.%s' % (klass.__module__, klass.__name__),
                    []).append(name)

            namespace = NameSpace(members)
            if not production_mode:
                assert not (
                    name in self.__d or hasattr(self, name)
                )
            self.__d[name] = namespace
            object.__setattr__(self, name, namespace)

        for instance in plugins.itervalues():
            instance.set_api(self)

        for klass, instance in plugins.iteritems():
            if not production_mode:
                assert instance.api is self
            if klass.finalize_early or not self.env.plugins_on_demand:
                instance.ensure_finalized()
                if not production_mode:
                    assert islocked(instance)

        object.__setattr__(self, '_API__finalized', True)
        object.__setattr__(self, 'plugins',
            tuple((k, tuple(v)) for k, v in plugin_info.iteritems())
        )


class IPAHelpFormatter(optparse.IndentedHelpFormatter):
    def format_epilog(self, text):
        text_width = self.width - self.current_indent
        indent = " " * self.current_indent
        lines = text.splitlines()
        result = '\n'.join(
            textwrap.fill(line, text_width, initial_indent=indent,
                subsequent_indent=indent)
            for line in lines)
        return '\n%s\n' % result