"""Base class for dynamically loaded objects accessible through the vregistry.

You'll also find some convenience classes to build selectors.

:organization: Logilab

:copyright: 2001-2010 LOGILAB S.A. (Paris, FRANCE), license is LGPL v2.

:contact: http://www.logilab.fr/ -- mailto:contact@logilab.fr

:license: GNU Lesser General Public License, v2.1 - http://www.gnu.org/licenses

"""

__docformat__ = "restructuredtext en"

import types

from logging import getLogger

from datetime import datetime, timedelta, time

from logilab.common.decorators import classproperty

from logilab.common.deprecation import deprecated

from logilab.common.logging_ext import set_log_methods

from rql.nodes import VariableRef, SubQuery

from rql.stmts import Union, Select

from cubicweb import Unauthorized, NoSelectableObject

from cubicweb.utils import UStringIO, ustrftime, strptime, todate, todatetime

ONESECOND = timedelta(0, 1, 0)

CACHE_REGISTRY = {}

class Cache(dict):

    def __init__(self):

        super(Cache, self).__init__()

        _now = datetime.now()

        self.cache_creation_date = _now

        self.latest_cache_lookup = _now

# selector base classes and operations ########################################

def objectify_selector(selector_func):

    """convenience decorator for simple selectors where a class definition

    would be overkill::

        @objectify_selector

        def yes(cls, *args, **kwargs):

            return 1

    """

    return type(selector_func.__name__, (Selector,),

                {'__call__': lambda self, *args, **kwargs: selector_func(*args, **kwargs)})

def _instantiate_selector(selector):

    """ensures `selector` is a `Selector` instance

    NOTE: This should only be used locally in build___select__()

    XXX: then, why not do it ??

    """

    if isinstance(selector, types.FunctionType):

        return objectify_selector(selector)()

    if isinstance(selector, type) and issubclass(selector, Selector):

        return selector()

    return selector

class Selector(object):

    """base class for selector classes providing implementation

    for operators ``&`` and ``|``

    This class is only here to give access to binary operators, the

    selector logic itself should be implemented in the __call__ method

    a selector is called to help choosing the correct object for a

    particular context by returning a score (`int`) telling how well

    the class given as first argument apply to the given context.

    0 score means that the class doesn't apply.

    """

    @property

    def func_name(self):

        # backward compatibility

        return self.__class__.__name__

    def search_selector(self, selector):

        """search for the given selector or selector instance in the selectors

        tree. Return it of None if not found

        """

        if self is selector:

            return self

        if isinstance(selector, type) and isinstance(self, selector):

            return self

        return None

    def __str__(self):

        return self.__class__.__name__

    def __and__(self, other):

        return AndSelector(self, other)

    def __rand__(self, other):

        return AndSelector(other, self)

    def __or__(self, other):

        return OrSelector(self, other)

    def __ror__(self, other):

        return OrSelector(other, self)

    def __invert__(self):

        return NotSelector(self)

    # XXX (function | function) or (function & function) not managed yet

    def __call__(self, cls, *args, **kwargs):

        return NotImplementedError("selector %s must implement its logic "

                                   "in its __call__ method" % self.__class__)

class MultiSelector(Selector):

    """base class for compound selector classes"""

    def __init__(self, *selectors):

        self.selectors = self.merge_selectors(selectors)

    def __str__(self):

        return '%s(%s)' % (self.__class__.__name__,

                           ','.join(str(s) for s in self.selectors))

    @classmethod

    def merge_selectors(cls, selectors):

        """deal with selector instanciation when necessary and merge

        multi-selectors if possible:

        AndSelector(AndSelector(sel1, sel2), AndSelector(sel3, sel4))

        ==> AndSelector(sel1, sel2, sel3, sel4)

        """

        merged_selectors = []

        for selector in selectors:

            try:

                selector = _instantiate_selector(selector)

            except:

                pass

            #assert isinstance(selector, Selector), selector

            if isinstance(selector, cls):

                merged_selectors += selector.selectors

            else:

                merged_selectors.append(selector)

        return merged_selectors

    def search_selector(self, selector):

        """search for the given selector or selector instance in the selectors

        tree. Return it of None if not found

        """

        for childselector in self.selectors:

            if childselector is selector:

                return childselector

            found = childselector.search_selector(selector)

            if found is not None:

                return found

        return None

class AndSelector(MultiSelector):

    """and-chained selectors (formerly known as chainall)"""

    def __call__(self, cls, *args, **kwargs):

        score = 0

        for selector in self.selectors:

            partscore = selector(cls, *args, **kwargs)

            if not partscore:

                return 0

            score += partscore

        return score

class OrSelector(MultiSelector):

    """or-chained selectors (formerly known as chainfirst)"""

    def __call__(self, cls, *args, **kwargs):

        for selector in self.selectors:

            partscore = selector(cls, *args, **kwargs)

            if partscore:

                return partscore

        return 0

class NotSelector(Selector):

    """negation selector"""

    def __init__(self, selector):

        self.selector = selector

    def __call__(self, cls, *args, **kwargs):

        score = self.selector(cls, *args, **kwargs)

        return int(not score)

    def __str__(self):

        return 'NOT(%s)' % super(NotSelector, self).__str__()

class yes(Selector):

    """return arbitrary score

    default score of 0.5 so any other selector take precedence

    """

    def __init__(self, score=0.5):

        self.score = score

    def __call__(self, *args, **kwargs):

        return self.score

# the base class for all appobjects ############################################

class AppObject(object):

    """This is the base class for CubicWeb application objects which are

    selected according to a context (usually at least a request and a result

    set).

    Concrete application objects classes are designed to be loaded by the

    vregistry and should be accessed through it, not by direct instantiation.

    The following attributes should be set on concret appobject classes:

    :__registry__:

      name of the registry for this object (string like 'views',

      'templates'...)

    :id:

      object's identifier in the registry (string like 'main',

      'primary', 'folder_box')

    :__select__:

      class'selector

    Moreover, the `__abstract__` attribute may be set to True to indicate

    that a appobject is abstract and should not be registered.

    At registration time, the following attributes are set on the class:

    :vreg:

      the instance's registry

    :schema:

      the instance's schema

    :config:

      the instance's configuration

    At selection time, the following attributes are set on the instance:

    :req:

      current request

    :rset:

      context result set or None

    :row:

      if a result set is set and the context is about a particular cell in the

      result set, and not the result set as a whole, specify the row number we

      are interested in, else None

    :col:

      if a result set is set and the context is about a particular cell in the

      result set, and not the result set as a whole, specify the col number we

      are interested in, else None

    """

    __registry__ = None

    id = None

    __select__ = yes()

    @classmethod

    def classid(cls):

        """returns a unique identifier for the appobject"""

        return '%s.%s' % (cls.__module__, cls.__name__)

    # XXX bw compat code

    @classmethod

    def build___select__(cls):

        for klass in cls.mro():

            if klass.__name__ == 'AppObject':

                continue # the bw compat __selector__ is there

            klassdict = klass.__dict__

            if ('__select__' in klassdict and '__selectors__' in klassdict

                and '__selgenerated__' not in klassdict):

                raise TypeError("__select__ and __selectors__ can't be used together on class %s" % cls)

            if '__selectors__' in klassdict and '__selgenerated__' not in klassdict:

                cls.__selgenerated__ = True

                # case where __selectors__ is defined locally (but __select__

                # is in a parent class)

                selectors = klassdict['__selectors__']

                if len(selectors) == 1:

                    # micro optimization: don't bother with AndSelector if there's

                    # only one selector

                    select = _instantiate_selector(selectors[0])

                else:

                    select = AndSelector(*selectors)

                cls.__select__ = select

    @classmethod

    def registered(cls, registry):

        """called by the registry when the appobject has been registered.

        It must return the object that will be actually registered (this may be

        the right hook to create an instance for example). By default the

        appobject is returned without any transformation.

        """

        cls.build___select__()

        cls.vreg = registry.vreg

        cls.schema = registry.schema

        cls.config = registry.config

        cls.register_properties()

        return cls

    @classmethod

    def vreg_initialization_completed(cls):

        pass

    # Eproperties definition:

    # key: id of the property (the actual CWProperty key is build using

    #      <registry name>.<obj id>.<property id>

    # value: tuple (property type, vocabfunc, default value, property description)

    #        possible types are those used by `logilab.common.configuration`

    #

    # notice that when it exists multiple objects with the same id (adaptation,

    # overriding) only the first encountered definition is considered, so those

    # objects can't try to have different default values for instance.

    property_defs = {}

    @classmethod

    def register_properties(cls):

        for propid, pdef in cls.property_defs.items():

            pdef = pdef.copy() # may be shared

            pdef['default'] = getattr(cls, propid, pdef['default'])

            pdef['sitewide'] = getattr(cls, 'site_wide', pdef.get('sitewide'))

            cls.vreg.register_property(cls.propkey(propid), **pdef)

    @classmethod

    def propkey(cls, propid):

        return '%s.%s.%s' % (cls.__registry__, cls.id, propid)

    @classproperty

    @deprecated('use __select__ and & or | operators')

    def __selectors__(cls):

        selector = cls.__select__

        if isinstance(selector, AndSelector):

            return tuple(selector.selectors)

        if not isinstance(selector, tuple):

            selector = (selector,)

        return selector

    def __init__(self, req=None, rset=None, row=None, col=None, **extra):

        super(AppObject, self).__init__()

        self.req = req

        self.rset = rset

        self.row = row

        self.col = col

        self.extra_kwargs = extra

    def get_cache(self, cachename):

        """

        NOTE: cachename should be dotted names as in :

        - cubicweb.mycache

        - cubes.blog.mycache

        - etc.

        """

        if cachename in CACHE_REGISTRY:

            cache = CACHE_REGISTRY[cachename]

        else:

            cache = CACHE_REGISTRY[cachename] = Cache()

        _now = datetime.now()

        if _now > cache.latest_cache_lookup + ONESECOND:

            ecache = self.req.execute('Any C,T WHERE C is CWCache, C name %(name)s, C timestamp T',

                                      {'name':cachename}).get_entity(0,0)

            cache.latest_cache_lookup = _now

            if not ecache.valid(cache.cache_creation_date):

                cache.clear()

                cache.cache_creation_date = _now

        return cache

    def propval(self, propid):

        assert self.req

        return self.req.property_value(self.propkey(propid))

    def limited_rql(self):

        """return a printable rql for the result set associated to the object,

        with limit/offset correctly set according to maximum page size and

        currently displayed page when necessary

        """

        # try to get page boundaries from the navigation component

        # XXX we should probably not have a ref to this component here (eg in

        #     cubicweb.common)

        nav = self.vreg['components'].select_object('navigation', self.req,

                                                    rset=self.rset)

        if nav:

            start, stop = nav.page_boundaries()

            rql = self._limit_offset_rql(stop - start, start)

        # result set may have be limited manually in which case navigation won't

        # apply

        elif self.rset.limited:

            rql = self._limit_offset_rql(*self.rset.limited)

        # navigation component doesn't apply and rset has not been limited, no

        # need to limit query

        else:

            rql = self.rset.printable_rql()

        return rql

    def _limit_offset_rql(self, limit, offset):

        rqlst = self.rset.syntax_tree()

        if len(rqlst.children) == 1:

            select = rqlst.children[0]

            olimit, ooffset = select.limit, select.offset

            select.limit, select.offset = limit, offset

            rql = rqlst.as_string(kwargs=self.rset.args)

            # restore original limit/offset

            select.limit, select.offset = olimit, ooffset