"""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 logilab.common.interface import implements as implements_iface

from yams import BASE_TYPES

from cubicweb import Unauthorized, NoSelectableObject, role
from cubicweb.vregistry import NoSelectableObject, Selector, chainall, chainfirst
from cubicweb.cwvreg import DummyCursorError
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):
        if isinstance(cls, Selector):
            selname = cls.__class__.__name__
            oid = args[0].id
        else:
            selname = selector.__name__
            oid = cls.id
        ret = selector(cls, *args, **kwargs)
        if TRACED_OIDS == 'all' or oid in TRACED_OIDS:
            SELECTOR_LOGGER.warning('selector %s returned %s for %s', selname, 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
    """
    page_size = kwargs.get('page_size')
    if page_size is None:
        page_size = req.form.get('page_size')
        if page_size is None:
            page_size = req.property_value('navigation.page-size')
        else:
            page_size = int(page_size)
    if rset is None or len(rset) <= page_size:
        return 0
    return 1
largerset_selector = deprecated_function(paginated_rset)

@lltrace
def sorted_rset(cls, req, rset, row=None, col=0, **kwargs):
    """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)


class match_search_state(Selector):
    def __init__(self, *expected_states):
        self.expected_states = expected_states
        
    def __call__(self, cls, req, rset, row=None, col=0, **kwargs):
        """checks if the current request search state is in one of the expected states
        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

@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)

# abstract selectors ##########################################################

class EClassSelector(Selector):
    """abstract class for selectors working on the entity classes of the result
    set
    """
    once_is_enough = False
    
    @lltrace
    def __call__(self, cls, req, rset, row=None, col=0, **kwargs):
        if not rset:
            return 0
        score = 0
        if row is None:
            for etype in rset.column_types(col):
                if etype is None: # outer join
                    continue
                if etype in BASE_TYPES:
                    return 0
                escore = self.score_class(cls.vreg.etype_class(etype), req)
                if not escore:
                    return 0
                elif self.once_is_enough:
                    return escore
                score += escore
        else:
            etype = rset.description[row][col]
            if etype is not None and not etype in BASE_TYPES:
                score = self.score_class(cls.vreg.etype_class(etype), req)
        return score and (score + 1)

    def score_class(self, eclass, req):
        raise NotImplementedError()


class EntitySelector(Selector):
    """abstract class for selectors working on the entity instances of the
    result set
    """
    @lltrace
    def __call__(self, cls, req, rset, row=None, col=0, **kwargs):
        if not rset:
            return 0
        score = 0
        if row is None:
            for row, rowvalue in enumerate(rset.rows):
                if rowvalue[col] is None: # outer join
                    continue
                try:
                    escore = self.score_entity(rset.get_entity(row, col))
                except NotAnEntity:
                    return 0
                if not escore:
                    return 0
                score += escore
        else:
            etype = rset.description[row][col]
            if etype is not None: # outer join
                try:
                    score = self.score_entity(rset.get_entity(row, col))
                except NotAnEntity:
                    return 0
        return score and (score + 1)

    def score_entity(self, entity):
        raise NotImplementedError()

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

class implements(EClassSelector):
    """initializer takes a list of interfaces or entity types as argument
    
    * if row is None, return the number of implemented interfaces for each
      entity's class in the result set at the specified column (or column 0).
      If any class has no matching interface, return 0.
    * if row is specified, return number of implemented interfaces by the
      entity's class at this row (and column)

    if some interface is an entity class, the score will reflect class
    proximity so the most specific object'll be selected
    """

    def __init__(self, *expected_ifaces):
        self.expected_ifaces = expected_ifaces

    def score_class(self, eclass, req):
        score = 0
        for iface in self.expected_ifaces:
            if isinstance(iface, basestring):
                # entity type
                iface = eclass.vreg.etype_class(iface)
            if implements_iface(eclass, iface):
                score += 1
                if getattr(iface, '__registry__', None) == 'etypes':
                    # adjust score if the interface is an entity class
                    if iface is eclass:
                        score += len(eclass.e_schema.ancestors()) + 1
                    else:
                        parents = [e.type for e in eclass.e_schema.ancestors()]
                        for index, etype in enumerate(reversed(parents)):
                            basecls = eclass.vreg.etype_class(etype)
                            if iface is basecls:
                                score += index + 1
                                break
        return score


class relation_possible(EClassSelector):
    """initializer takes relation name as argument and an optional role (default
      as subject) and target type (default to unspecified)
      
    * if row is None, return 1 if every entity's class in the result set at the
      specified column (or column 0) may have this relation (as role). If target
      type is specified, check the relation's end may be of this target type.
      
    * if row is specified, check relation is supported by the entity's class at
      this row (and column)
    """
    def __init__(self, rtype, role='subject', target_etype=None,
                 permission='read', once_is_enough=False):
        self.rtype = rtype
        self.role = role
        self.target_etype = target_etype
        self.permission = permission
        self.once_is_enough = once_is_enough

    @lltrace
    def __call__(self, cls, *args, **kwargs):
        rschema = cls.schema.rschema(self.rtype)
        if not (rschema.has_perm(req, self.permission)
                or rschema.has_local_role(self.permission)):
            return 0
        return super(relation_possible, self)(cls, *args, **kwargs)
        
    def score_class(self, eclass, req):
        eschema = eclass.e_schema
        try:
            if self.role == 'object':
                rschema = eschema.object_relation(self.rtype)
            else:
                rschema = eschema.subject_relation(self.rtype)
        except KeyError:
            return 0
        if self.target_etype is not None:
            try:
                if self.role == 'object':
                    return self.target_etype in rschema.objects(eschema)
                else:
                    return self.target_etype in rschema.subjects(eschema)
            except KeyError, ex:
                return 0
        return 1


class non_final_entity(EClassSelector):
    """initializer takes no argument

    * if row is None, return 1 if there are only non final entity's class in the
      result set at the specified column (or column 0)
    * if row is specified, return 1 if entity's class at this row (and column)
      isn't final
    """
    def score_class(self, eclass, req):
        return int(not eclass.e_schema.is_final())


class match_user_groups(Selector):
    """initializer takes users group as argument

    * check logged user is in one of the given groups. If special 'owners' group
      given:
      - if row is specified check the entity at the given row/col is owned by
        the logged user
      - if row is not specified check all entities in col are owned by the
        logged user
    """
    
    def __init__(self, *required_groups):
        self.required_groups = required_groups
    
    @lltrace
    def __call__(self, cls, req, rset=None, row=None, col=0, **kwargs):
        user = req.user
        if user is None:
            return int('guests' in self.require_groups)
        score = user.matching_groups(self.require_groups)
        if not score and 'owners' in self.require_groups and rset:
            nbowned = 0
            if row is not None:
                if not user.owns(rset[row][col]):
                    return 0
                score = 1
            else:
                score = all(user.owns(r[col or 0]) for r in rset)
        return 0


class has_editable_relation(EntitySelector):
    """initializer takes no argument

    * if row is specified check the entity at the given row/col has some
      relation editable by the logged user
    * if row is not specified check all entities in col are owned have some
      relation editable by the logged userlogged user
    """
        
    def score_entity(self, entity):
        # if user has no update right but it can modify some relation,
        # display action anyway
        for dummy in entity.srelations_by_category(('generic', 'metadata'),
                                                   'add'):
            return 1
        for rschema, targetschemas, role in entity.relations_by_category(
            ('primary', 'secondary'), 'add'):
            if not rschema.is_final():
                return 1
        return 0


class may_add_relation(EntitySelector):
    """initializer a relation type and optional role (default to 'subject') as
    argument

    if row is specified check the relation may be added to the entity at the
    given row/col (if row specified) or to every entities in the given col (if
    row is not specified)
    """
    
    def __init__(self, rtype, role='subject'):
        self.rtype = rtype
        self.role = role
        
    def score_entity(self, entity):
        rschema = entity.schema.rschema(self.rtype)
        if self.role == 'subject':
            if not rschema.has_perm(req, 'add', fromeid=entity.eid):
                return False
        elif not rschema.has_perm(req, 'add', toeid=entity.eid):
            return False
        return True

        
class has_permission(EntitySelector):
    """initializer takes a schema action (eg 'read'/'add'/'delete'/'update') as
    argument

    * if row is specified check user has permission to do the requested action
      on the entity at the given row/col
    * if row is specified check user has permission to do the requested action
      on all entities in the given col
    """
    def __init__(self, schema_action):
        self.schema_action = schema_action
        
    @lltrace
    def __call__(self, cls, req, rset, row=None, col=0, **kwargs):
        user = req.user
        action = self.schema_action
        if row is None:
            score = 0
            need_local_check = [] 
            geteschema = cls.schema.eschema
            for etype in rset.column_types(0):
                if etype in BASE_TYPES:
                    return 0
                eschema = geteschema(etype)
                if not user.matching_groups(eschema.get_groups(action)):
                    if eschema.has_local_role(action):
                        # have to ckeck local roles
                        need_local_check.append(eschema)
                        continue
                    else:
                        # even a local role won't be enough
                        return 0
                score += accepted
            if need_local_check:
                # check local role for entities of necessary types
                for i, row in enumerate(rset):
                    if not rset.description[i][0] in need_local_check:
                        continue
                    if not self.score_entity(rset.get_entity(i, col)):
                        return 0
                    score += 1
            return score
        if rset.description[row][col] in BASE_TYPES:
            return 0
        return self.score_entity(rset.get_entity(row, col))
    
    def score_entity(self, entity):
        if entity.has_perm(self.schema_action):
            return 1
        return 0


class has_add_permission(EClassSelector):
    
    def score_class(self, eclass, req):
        eschema = eclass.e_schema
        if not (eschema.is_final() or eschema.is_subobject(strict=True)) \
               and eschema.has_perm(req, 'add'):
            return 1
        return 0

        
class score_entity(EntitySelector):
    def __init__(self, scorefunc):
        self.score_entity = scorefunc

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

@lltrace
def accept_etype(cls, req, *args, **kwargs):
    """check etype presence in request form *and* accepts conformance"""
    try:
        etype = req.form['etype']
    except KeyError:
        try:
            etype = kwargs['etype']
        except KeyError:
            return 0
    return implements(*cls.accepts).score_class(cls.vreg.etype_class(etype), req)
etype_form_selector = deprecated_function(accept_etype)

@lltrace
def _rql_condition(cls, req, rset, row=None, col=0, **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 but_etype(cls, req, rset, row=None, col=0, **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
def etype_rtype_selector(cls, req, rset, row=None, col=0, **kwargs):
    """only check if the user has read access on the entity's type refered
    by the .etype attribute and on the relations's type refered by the
    .rtype attribute if set.
    """
    schema = cls.schema
    perm = getattr(cls, 'require_permission', 'read')
    if hasattr(cls, 'etype'):
        eschema = schema.eschema(cls.etype)
        if not (eschema.has_perm(req, perm) or eschema.has_local_role(perm)):
            return 0
    if hasattr(cls, 'rtype'):
        rschema = schema.rschema(cls.rtype)
        if not (rschema.has_perm(req, perm) or rschema.has_local_role(perm)):
            return 0
    return 1

@lltrace
def has_related_entities(cls, req, rset, row=None, col=0, **kwargs):
    return bool(rset.get_entity(row or 0, col or 0).related(cls.rtype, role(cls)))

@lltrace
def user_can_add_etype(cls, req, rset, row=None, col=0, **kwargs):
    """only check if the user has add access on the entity's type refered
    by the .etype attribute.
    """
    if not cls.schema.eschema(cls.etype).has_perm(req, 'add'):
        return 0
    return 1
add_etype_selector = deprecated_function(user_can_add_etype)

@lltrace
def match_context_prop(cls, req, rset, row=None, col=0, context=None,
                       **kwargs):
    propval = req.property_value('%s.%s.context' % (cls.__registry__, cls.id))
    if not propval:
        propval = cls.context
    if context is not None and propval and context != propval:
        return 0
    return 1
contextprop_selector = deprecated_function(match_context_prop)

@lltrace
def primary_view(cls, req, rset, row=None, col=0, view=None,
                          **kwargs):
    if view is not None and not view.is_primary():
        return 0
    return 1
primaryview_selector = deprecated_function(primary_view)

def appobject_selectable(registry, oid):
    """return a selector that will have a positive score if an object for the
    given registry and object id is selectable for the input context
    """
    @lltrace
    def selector(cls, req, rset, *args, **kwargs):
        try:
            cls.vreg.select_object(registry, oid, req, rset, *args, **kwargs)
            return 1
        except NoSelectableObject:
            return 0
    return selector



# XXX DEPRECATED ##############################################################

def nfentity_selector(cls, req, rset, row=None, col=0, **kwargs):
    return non_final_entity()(cls, req, rset, row, col)
nfentity_selector = deprecated_function(nfentity_selector)

def implement_interface(cls, req, rset, row=None, col=0, **kwargs):
    return implements(*cls.accepts_interfaces)(cls, req, rset, row, col)
_interface_selector = deprecated_function(implement_interface)
interface_selector = deprecated_function(implement_interface)
implement_interface = deprecated_function(implement_interface)

def searchstate_selector(cls, req, rset, row=None, col=0, **kwargs):
    return match_search_state(cls.search_states)(cls, req, rset, row, col)
searchstate_selector = deprecated_function(searchstate_selector)

def match_user_group(cls, req, rset=None, row=None, col=0, **kwargs):
    return match_user_groups(cls.require_groups)(cls, req, rset, row, col, **kwargs)
in_group_selector = deprecated_function(match_user_group)
match_user_group = deprecated_function(match_user_group)

def has_relation(cls, req, rset, row=None, col=0, **kwargs):
    return relation_possible(cls.rtype, role(cls), cls.etype,
                             getattr(cls, 'require_permission', 'read'))(cls, req, rset, row, col, **kwargs)
has_relation = deprecated_function(has_relation)

def one_has_relation(cls, req, rset, row=None, col=0, **kwargs):
    return relation_possible(cls.rtype, role(cls), cls.etype,
                             getattr(cls, 'require_permission', 'read',
                                     once_is_enough=True))(cls, req, rset, row, col, **kwargs)
one_has_relation = deprecated_function(one_has_relation, 'use relation_possible selector')

def accept_rset(cls, req, rset, row=None, col=0, **kwargs):
    """simply delegate to cls.accept_rset method"""
    return implements(*cls.accepts)(cls, req, rset, row=row, col=col)
accept_rset_selector = deprecated_function(accept_rset)
accept_rset = deprecated_function(accept_rset, 'use implements selector')

accept = chainall(non_final_entity(), accept_rset, name='accept')
accept_selector = deprecated_function(accept)
accept = deprecated_function(accept, 'use implements selector')

# compound selectors ##########################################################

accept_one = deprecated_function(chainall(one_line_rset, accept,
                                          name='accept_one'))
accept_one_selector = deprecated_function(accept_one)

rql_condition = chainall(non_final_entity(), one_line_rset, _rql_condition,
                         name='rql_condition')
rqlcondition_selector = deprecated_function(rql_condition)


searchstate_accept = chainall(nonempty_rset, match_search_state, accept,
                              name='searchstate_accept')
searchstate_accept_selector = deprecated_function(searchstate_accept)

searchstate_accept_one = chainall(one_line_rset, match_search_state,
                                  accept, _rql_condition,
                                  name='searchstate_accept_one')
searchstate_accept_one_selector = deprecated_function(searchstate_accept_one)

searchstate_accept_one_but_etype = chainall(searchstate_accept_one, but_etype,
                                            name='searchstate_accept_one_but_etype')
searchstate_accept_one_but_etype_selector = deprecated_function(
    searchstate_accept_one_but_etype)