"""This file contains some basic selectors required by application objects.

A selector is responsible to score how well an object may be used with a

given result set (publishing time selection)

If you have trouble with selectors, especially if the objet (typically

a view or a component) you want to use is not selected and you want to

know which one(s) of its selectors fail (e.g. returns 0), you can use

`traced_selection` or even direclty `TRACED_OIDS`.

`TRACED_OIDS` is a tuple of traced object ids. The special value

'all' may be used to log selectors for all objects.

For instance, say that the following code yields a `NoSelectableObject`

exception::

    self.view('calendar', myrset)

You can log the selectors involved for *calendar* by replacing the line

above by::

    # in Python2.5

    from cubicweb.common.selectors import traced_selection

    with traced_selection():

        self.view('calendar', myrset)

    # in Python2.4

    from cubicweb.common import selectors

    selectors.TRACED_OIDS = ('calendar',)

    self.view('calendar', myrset)

    selectors.TRACED_OIDS = ()

:organization: Logilab

:copyright: 2001-2009 LOGILAB S.A. (Paris, FRANCE), all rights reserved.

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

"""

__docformat__ = "restructuredtext en"

import logging

from logilab.common.compat import all

from logilab.common.deprecation import deprecated_function

from cubicweb import Unauthorized, NoSelectableObject, role

from cubicweb.cwvreg import DummyCursorError

from cubicweb.vregistry import chainall, chainfirst, NoSelectableObject

from cubicweb.cwconfig import CubicWebConfiguration

from cubicweb.schema import split_expression

# helpers for debugging selectors

SELECTOR_LOGGER = logging.getLogger('cubicweb.selectors')

TRACED_OIDS = ()

def lltrace(selector):

    # don't wrap selectors if not in development mode

    if CubicWebConfiguration.mode == 'installed':

        return selector

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

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

        if TRACED_OIDS == 'all' or cls.id in TRACED_OIDS:

            SELECTOR_LOGGER.warning('selector %s returned %s for %s', selector.__name__, ret, cls)

        return ret

    traced.__name__ = selector.__name__

    return traced

class traced_selection(object):

    """selector debugging helper.

    Typical usage is :

    >>> with traced_selection():

    ...     # some code in which you want to debug selectors

    ...     # for all objects

    or

    >>> with traced_selection( ('oid1', 'oid2') ):

    ...     # some code in which you want to debug selectors

    ...     # for objects with id 'oid1' and 'oid2'

    """

    def __init__(self, traced='all'):

        self.traced = traced

    def __enter__(self):

        global TRACED_OIDS

        TRACED_OIDS = self.traced

    def __exit__(self, exctype, exc, traceback):

        global TRACED_OIDS

        TRACED_OIDS = ()

        return traceback is None

# very basic selectors ########################################################

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

    """accept everything"""

    return 1

yes_selector = deprecated_function(yes)

@lltrace

def none_rset(cls, req, rset, *args, **kwargs):

    """accept no result set"""

    if rset is None:

        return 1

    return 0

norset_selector = deprecated_function(none_rset)

@lltrace

def any_rset(cls, req, rset, *args, **kwargs):

    """accept result set, whatever the number of result"""

    if rset is not None:

        return 1

    return 0

rset_selector = deprecated_function(any_rset)

@lltrace

def nonempty_rset(cls, req, rset, *args, **kwargs):

    """accept any non empty result set"""

    if rset is not None and rset.rowcount:

        return 1

    return 0

anyrset_selector = deprecated_function(nonempty_rset)

@lltrace

def empty_rset(cls, req, rset, *args, **kwargs):

    """accept empty result set"""

    if rset is not None and rset.rowcount == 0:

        return 1

    return 0

emptyrset_selector = deprecated_function(empty_rset)

@lltrace

def one_line_rset(cls, req, rset, row=None, *args, **kwargs):

    """accept result set with a single line of result"""

    if rset is not None and (row is not None or rset.rowcount == 1):

        return 1

    return 0

onelinerset_selector = deprecated_function(one_line_rset)

@lltrace

def two_lines_rset(cls, req, rset, *args, **kwargs):

    """accept result set with *at least* two lines of result"""

    if rset is not None and rset.rowcount > 1:

        return 1

    return 0

twolinerset_selector = deprecated_function(two_lines_rset)

@lltrace

def two_cols_rset(cls, req, rset, *args, **kwargs):

    """accept result set with at least one line and two columns of result"""

    if rset is not None and rset.rowcount > 0 and len(rset.rows[0]) > 1:

        return 1

    return 0

twocolrset_selector = deprecated_function(two_cols_rset)

@lltrace

def paginated_rset(cls, req, rset, *args, **kwargs):

    """accept result sets with more rows than the page size

    """

    if rset is None or len(rset) <= req.property_value('navigation.page-size'):

        return 0

    return 1

largerset_selector = deprecated_function(paginated_rset)

@lltrace

def sorted_rset(cls, req, rset, row=None, col=None):

    """accept sorted result set"""

    rqlst = rset.syntax_tree()

    if len(rqlst.children) > 1 or not rqlst.children[0].orderby:

        return 0

    return 2

sortedrset_selector = deprecated_function(sorted_rset)

@lltrace

def one_etype_rset(cls, req, rset, *args, **kwargs):

    """accept result set where entities in the first columns are all of the

    same type

    """

    if len(rset.column_types(0)) != 1:

        return 0

    return 1

oneetyperset_selector = deprecated_function(one_etype_rset)

@lltrace

def two_etypes_rset(cls, req, rset, **kwargs):

    """accepts resultsets containing several entity types"""

    if rset:

        etypes = rset.column_types(0)

        if len(etypes) > 1:

            return 1

    return 0

multitype_selector = deprecated_function(two_etypes_rset)

@lltrace

def match_search_state(cls, req, rset, row=None, col=None, **kwargs):

    """checks if the current search state is in a .search_states attribute of

    the wrapped class

    search state should be either 'normal' or 'linksearch' (eg searching for an

    object to create a relation with another)

    """

    try:

        if not req.search_state[0] in cls.search_states:

            return 0

    except AttributeError:

        return 1 # class doesn't care about search state, accept it

    return 1

searchstate_selector = deprecated_function(match_search_state)

@lltrace

def anonymous_user(cls, req, *args, **kwargs):

    """accept if user is anonymous"""

    if req.cnx.anonymous_connection:

        return 1

    return 0

anonymous_selector = deprecated_function(anonymous_user)

@lltrace

def authenticated_user(cls, req, *args, **kwargs):

    """accept if user is authenticated"""

    return not anonymous_user(cls, req, *args, **kwargs)

not_anonymous_selector = deprecated_function(authenticated_user)

@lltrace

def match_form_params(cls, req, *args, **kwargs):

    """check if parameters specified by the form_params attribute on

    the wrapped class are specified in request form parameters

    """

    score = 0

    for param in cls.form_params:

        val = req.form.get(param)

        if not val:

            return 0

        score += 1

    return score + 1

req_form_params_selector = deprecated_function(match_form_params)

@lltrace

def match_kwargs(cls, req, *args, **kwargs):

    """check if arguments specified by the expected_kwargs attribute on

    the wrapped class are specified in given named parameters

    """

    values = []

    for arg in cls.expected_kwargs:

        if not arg in kwargs:

            return 0

    return 1

kwargs_selector = deprecated_function(match_kwargs)

# not so basic selectors ######################################################

@lltrace

def accept_etype(cls, req, *args, **kwargs):

    """check etype presence in request form *and* accepts conformance"""

    if 'etype' not in req.form and 'etype' not in kwargs:

        return 0

    try:

        etype = req.form['etype']

    except KeyError:

        etype = kwargs['etype']

    # value is a list or a tuple if web request form received several

    # values for etype parameter

    assert isinstance(etype, basestring), "got multiple etype parameters in req.form"

    if 'Any' in cls.accepts:

        return 1

    # no Any found, we *need* exact match

    if etype not in cls.accepts:

        return 0

    # exact match must return a greater value than 'Any'-match

    return 2

etype_form_selector = deprecated_function(accept_etype)

@lltrace

def _non_final_entity(cls, req, rset, row=None, col=None, **kwargs):

    """accept non final entities

    if row is not specified, use the first one

    if col is not specified, use the first one

    """

    etype = rset.description[row or 0][col or 0]

    if etype is None: # outer join

        return 0

    if cls.schema.eschema(etype).is_final():

        return 0

    return 1

_nfentity_selector = deprecated_function(_non_final_entity)

@lltrace

def _rql_condition(cls, req, rset, row=None, col=None, **kwargs):

    """accept single entity result set if the entity match an rql condition

    """

    if cls.condition:

        eid = rset[row or 0][col or 0]

        if 'U' in frozenset(split_expression(cls.condition)):

            rql = 'Any X WHERE X eid %%(x)s, U eid %%(u)s, %s' % cls.condition

        else:

            rql = 'Any X WHERE X eid %%(x)s, %s' % cls.condition

        try:

            return len(req.execute(rql, {'x': eid, 'u': req.user.eid}, 'x'))

        except Unauthorized:

            return 0

    return 1

_rqlcondition_selector = deprecated_function(_rql_condition)

@lltrace

def _implement_interface(cls, req, rset, row=None, col=None, **kwargs):

    """accept uniform result sets, and apply the following rules:

    * wrapped class must have a accepts_interfaces attribute listing the

      accepted ORed interfaces

    * if row is None, return the sum of values returned by the method

      for each entity's class in the result set. If any score is 0,

      return 0.

    * if row is specified, return the value returned by the method with

      the entity's class of this row

    """

    # XXX this selector can be refactored : extract the code testing

    #     for entity schema / interface compliance

    score = 0

    # check 'accepts' to give priority to more specific classes

    if row is None:

        for etype in rset.column_types(col or 0):

            eclass = cls.vreg.etype_class(etype)

            escore = 0

            for iface in cls.accepts_interfaces:

                escore += iface.is_implemented_by(eclass)

            if not escore:

                return 0

            score += escore

            accepts = set(getattr(cls, 'accepts', ()))

            # if accepts is defined on the vobject, eclass must match

            if accepts:

                eschema = eclass.e_schema

                etypes = set([eschema] + eschema.ancestors())

                if accepts & etypes:

                    score += 2

                elif 'Any' not in accepts:

                    return 0

        return score + 1

    etype = rset.description[row][col or 0]

    if etype is None: # outer join

        return 0

    eclass = cls.vreg.etype_class(etype)

    for iface in cls.accepts_interfaces:

        score += iface.is_implemented_by(eclass)

    if score:

        accepts = set(getattr(cls, 'accepts', ()))

        # if accepts is defined on the vobject, eclass must match

        if accepts:

            eschema = eclass.e_schema

            etypes = set([eschema] + eschema.ancestors())

            if accepts & etypes:

                score += 1

            elif 'Any' not in accepts:

                return 0

        score += 1

    return score

_interface_selector = deprecated_function(_implement_interface)

@lltrace

def score_entity_selector(cls, req, rset, row=None, col=None, **kwargs):

    if row is None:

        rows = xrange(rset.rowcount)

    else:

        rows = (row,)

    for row in rows:

        try:

            score = cls.score_entity(rset.get_entity(row, col or 0))

        except DummyCursorError:

            # get a dummy cursor error, that means we are currently

            # using a dummy rset to list possible views for an entity

            # type, not for an actual result set. In that case, we

            # don't care of the value, consider the object as selectable

            return 1

        if not score:

            return 0

    return 1

@lltrace

def accept_rset(cls, req, rset, row=None, col=None, **kwargs):

    """simply delegate to cls.accept_rset method"""

    return cls.accept_rset(req, rset, row=row, col=col)

accept_rset_selector = deprecated_function(accept_rset)

@lltrace

def but_etype(cls, req, rset, row=None, col=None, **kwargs):

    """restrict the searchstate_accept_one_selector to exclude entity's type

    refered by the .etype attribute

    """

    if rset.description[row or 0][col or 0] == cls.etype:

        return 0

    return 1

but_etype_selector = deprecated_function(but_etype)

@lltrace