"""relation tags store

: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"

class RelationTags(object):

    """RelationTags instances are a tag store for full relation definitions :

         (subject type, relation type, object type, role)

    allowing to set tags using wildcard (eg '*') as subject type / object type

    if `use_set` is True, a set of tags is associated to each key, and you

    should use rtags / etype_rtags / add_rtag api. Otherwise, a single tag is

    associated to each key, and you should use rtag / etype_rtag / set_rtag api.

    """

    def __init__(self, use_set=False):

        self.use_set = use_set

        self._tagdefs = {}

    def set_rtag(self, tag, rtype, role, stype='*', otype='*'):

        assert not self.use_set

        assert role in ('subject', 'object'), role

        self._tagdefs[(str(rtype), role, str(stype), str(otype))] = tag

    def rtag(self, rtype, role, stype='*', otype='*'):

        assert not self.use_set

        for key in reversed(self._get_keys(rtype, role, stype, otype)):

            try:

                return self._tagdefs[key]

            except KeyError:

                continue

        return None

    def etype_rtag(self, etype, rtype, role, ttype='*'):

        if role == 'subject':

            return self.rtag(rtype, role, etype, ttype)

        return self.rtag(rtype, role, ttype, etype)

    def add_rtag(self, tag, rtype, role, stype='*', otype='*'):

        assert self.use_set

        assert role in ('subject', 'object'), role

        rtags = self._tagdefs.setdefault((rtype, role, stype, otype), set())

        rtags.add(tag)

    def rtags(self, rtype, role, stype='*', otype='*'):

        assert self.use_set

        rtags = set()

        for key in self._get_keys(rtype, role, stype, otype):

            try:

                rtags.update(self._tagdefs[key])

            except KeyError:

                continue

        return rtags

    def etype_rtags(self, etype, rtype, role, ttype='*'):

        if role == 'subject':

            return self.rtags(rtype, role, etype, ttype)

        return self.rtags(rtype, role, ttype, etype)

    def _get_keys(self, rtype, role, stype, otype): 

        assert role in ('subject', 'object'), role

        keys = [(rtype, role, '*', '*'),

                (rtype, role, '*', otype),

                (rtype, role, stype, '*'),

                (rtype, role, stype, otype)]

        if stype == '*' or otype == '*':

            keys.remove((rtype, role, '*', '*'))

            if stype == '*':

                keys.remove((rtype, role, '*', otype))

            if otype == '*':

                keys.remove((rtype, role, stype, '*'))            

        return keys

    # dict compat

    def __getitem__(self, key):

        if isinstance(key, basestring):

            key = (key,)

        return self.rtags(*key)

    __contains__ = __getitem__