"""The `ResultSet` class which is returned as result of a rql query

:organization: Logilab

:copyright: 2001-2008 LOGILAB S.A. (Paris, FRANCE), all rights reserved.

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

"""

__docformat__ = "restructuredtext en"

from logilab.common.decorators import cached, clear_cache, copy_cache

from rql import nodes

from cubicweb import NotAnEntity

class ResultSet(object):

    """a result set wrap a RQL query result. This object implements a partial

    list protocol to allow direct use as a list of result rows.

    :type rowcount: int

    :ivar rowcount: number of rows in the result

    :type rows: list

    :ivar rows: list of rows of result

    :type description: list

    :ivar description:

      result's description, using the same structure as the result itself

    :type rql: str or unicode

    :ivar rql: the original RQL query string

    """

    def __init__(self, results, rql, args=None, description=(), cachekey=None,

                 rqlst=None):

        self.rows = results

        self.rowcount = results and len(results) or 0

        # original query and arguments

        self.rql = rql

        self.args = args

        self.cachekey = cachekey

        # entity types for each cell (same shape as rows)

        # maybe discarded if specified when the query has been executed

        self.description = description

        # parsed syntax tree

        if rqlst is not None:

            rqlst.schema = None # reset schema in case of pyro transfert

        self._rqlst = rqlst

        # set to (limit, offset) when a result set is limited using the

        # .limit method

        self.limited = None

        # set by the cursor which returned this resultset

        self.vreg = None

        self.req = None

    def __str__(self):

        if not self.rows:

            return '<empty resultset %s>' % self.rql

        return '<resultset %s (%s rows)>' % (self.rql, len(self.rows))

    def __repr__(self):

        if not self.rows:

            return '<empty resultset for %r>' % self.rql

        if not self.description:

            return '<resultset %r: %s>' % (self.rql, '\n'.join(str(r) for r in self.rows))

        return '<resultset %r: %s>' % (self.rql,

                                       '\n'.join('%s (%s)' % (r, d)

                                                 for r, d in zip(self.rows, self.description)))

    @cached

    def possible_actions(self):

        return self.vreg.possible_vobjects('actions', self.req, self)

    def __len__(self):

        """returns the result set's size"""

        return self.rowcount

    def __nonzero__(self):

        return self.rowcount

    def __getitem__(self, i):

        """returns the ith element of the result set"""

        return self.rows[i] #ResultSetRow(self.rows[i])

    def __getslice__(self, i, j):

        """returns slice [i:j] of the result set"""

        return self.rows[i:j]

    def __iter__(self):

        """Returns an iterator over rows"""

        return iter(self.rows)

    def __add__(self, rset):

        # XXX buggy implementation (.rql and .args attributes at least much

        # probably differ)

        # at least rql could be fixed now that we have union and sub-queries

        # but I tend to think that since we have that, we should not need this

        # method anymore (syt)

        rset = ResultSet(self.rows+rset.rows, self.rql, self.args,

                         self.description +rset.description)

        return self.req.decorate_rset(rset)

    def _prepare_copy(self, rows, descr):

        rset = ResultSet(rows, self.rql, self.args, descr)

        return self.req.decorate_rset(rset)

    def transformed_rset(self, transformcb):

        """ the result set according to a given column types

        :type transormcb: callable(row, desc)

        :param transformcb:

          a callable which should take a row and its type description as

          parameters, and return the transformed row and type description.

        :type col: int

        :param col: the column index

        :rtype: `ResultSet`

        """

        rows, descr = [], []

        rset = self._prepare_copy(rows, descr)

        for row, desc in zip(self.rows, self.description):

            nrow, ndesc = transformcb(row, desc)

            if ndesc: # transformcb returns None for ndesc to skip that row

                rows.append(nrow)

                descr.append(ndesc)

        rset.rowcount = len(rows)

        return rset

    def filtered_rset(self, filtercb, col=0):

        """filter the result set according to a given filtercb

        :type filtercb: callable(entity)

        :param filtercb:

          a callable which should take an entity as argument and return

          False if it should be skipped, else True

        :type col: int

        :param col: the column index

        :rtype: `ResultSet`

        """

        rows, descr = [], []

        rset = self._prepare_copy(rows, descr)

        for i in xrange(len(self)):

            if not filtercb(self.get_entity(i, col)):

                continue

            rows.append(self.rows[i])

            descr.append(self.description[i])

        rset.rowcount = len(rows)

        return rset

    def sorted_rset(self, keyfunc, reverse=False, col=0):

        """sorts the result set according to a given keyfunc

        :type keyfunc: callable(entity)

        :param keyfunc:

          a callable which should take an entity as argument and return

          the value used to compare and sort

        :type reverse: bool

        :param reverse: if the result should be reversed

        :type col: int

        :param col: the column index. if col = -1, the whole row are used

        :rtype: `ResultSet`

        """

        rows, descr = [], []

        rset = self._prepare_copy(rows, descr)

        if col >= 0:

            entities = sorted(enumerate(self.entities(col)),

                              key=lambda (i, e): keyfunc(e), reverse=reverse)

        else:

            entities = sorted(enumerate(self),

                              key=lambda (i, e): keyfunc(e), reverse=reverse)

        for index, entity in entities:

            rows.append(self.rows[index])

            descr.append(self.description[index])

        rset.rowcount = len(rows)

        return rset

    def split_rset(self, keyfunc=None, col=0, return_dict=False):

        """Splits the result set in multiple result set according to a given key

        :type keyfunc: callable(entity or FinalType)

        :param keyfunc:

          a callable which should take a value of the rset in argument and

          return the value used to group the value. If not define, raw value

          of the specified columns is used.

        :type col: int

        :param col: the column index. if col = -1, the whole row are used

        :type return_dict: Boolean

        :param return_dict: If true, the function return a mapping

            (key -> rset) instead of a list of rset

        :rtype: List of `ResultSet` or mapping of  `ResultSet`

        """

        result = []

        mapping = {}

        for idx, line in enumerate(self):

            if col >= 0:

                try:

                    key = self.get_entity(idx,col)

                except NotAnEntity:

                    key = line[col]

            else:

                key = line

            if keyfunc is not None:

                key = keyfunc(key)

            if key not in mapping:

                rows, descr = [], []

                rset = self._prepare_copy(rows, descr)

                mapping[key] = rset

                result.append(rset)

            else:

                rset = mapping[key]

            rset.rows.append(self.rows[idx])

            rset.description.append(self.description[idx])

        for rset in result:

            rset.rowcount = len(rset.rows)

        if return_dict:

            return mapping

        else:

            return result

    def limit(self, limit, offset=0, inplace=False):

        """limit the result set to the given number of rows optionaly starting

        from an index different than 0

        :type limit: int

        :param limit: the maximum number of results

        :type offset: int

        :param offset: the offset index

        :type inplace: bool

        :param inplace:

          if true, the result set is modified in place, else a new result set

          is returned and the original is left unmodified

        :rtype: `ResultSet`

        """

        stop = limit+offset

        rows = self.rows[offset:stop]

        descr = self.description[offset:stop]

        if inplace:

            rset = self

            rset.rows, rset.description = rows, descr

            rset.rowcount = len(rows)

            clear_cache(rset, 'description_struct')

            if offset:

                clear_cache(rset, 'get_entity')

            # we also have to fix/remove from the request entity cache entities

            # which get a wrong rset reference by this limit call

            for entity in self.req.cached_entities():

                if entity.rset is self:

                    if offset <= entity.row < stop:

                        entity.row = entity.row - offset

                    else:

                        self.req.drop_entity_cache(entity.eid)

        else:

            rset = self._prepare_copy(rows, descr)

            if not offset:

                # can copy built entity caches

                copy_cache(rset, 'get_entity', self)

        rset.limited = (limit, offset)

        return rset

    def printable_rql(self, encoded=False):

        """return the result set's origin rql as a string, with arguments

        substitued

        """

        encoding = self.req.encoding

        rqlstr = self.syntax_tree().as_string(encoding, self.args)

        # sounds like we get encoded or unicode string due to a bug in as_string

        if not encoded:

            if isinstance(rqlstr, unicode):

                return rqlstr

            return unicode(rqlstr, encoding)

        else: 

            if isinstance(rqlstr, unicode):

                return rqlstr.encode(encoding)

            return rqlstr

    # client helper methods ###################################################

    def entities(self, col=0):

        """iter on entities with eid in the `col` column of the result set"""

        for i in xrange(len(self)):

            # may have None values in case of outer join (or aggregat on eid

            # hacks)

            if self.rows[i][col] is not None:

                yield self.get_entity(i, col)

    @cached

    def get_entity(self, row, col=None):

        """special method for query retreiving a single entity, returns a

        partially initialized Entity instance.

        WARNING: due to the cache wrapping this function, you should NEVER

                 give row as a named parameter (i.e. rset.get_entity(req, 0)

                 is OK but rset.get_entity(row=0, req=req) isn't

        :type row,col: int, int

        :param row,col:

          row and col numbers localizing the entity among the result's table

        :return: the partially initialized `Entity` instance

        """

        if col is None:

            from warnings import warn

            msg = 'col parameter will become mandatory in future version'

            warn(msg, DeprecationWarning, stacklevel=3)

            col = 0

        etype = self.description[row][col]

        try:

            eschema = self.vreg.schema.eschema(etype)

            if eschema.is_final():

                raise NotAnEntity(etype)

        except KeyError:

            raise NotAnEntity(etype)

        return self._build_entity(row, col)

    def _build_entity(self, row, col, _localcache=None):

        """internal method to get a single entity, returns a

        partially initialized Entity instance.

        partially means that only attributes selected in the RQL

        query will be directly assigned to the entity.

        :type row,col: int, int

        :param row,col:

          row and col numbers localizing the entity among the result's table

        :return: the partially initialized `Entity` instance

        """

        req = self.req

        if req is None:

            raise AssertionError('dont call get_entity with no req on the result set')

        rowvalues = self.rows[row]

        eid = rowvalues[col]

        assert eid is not None

        # return cached entity if exists. This also avoids potential recursion

        # XXX should we consider updating a cached entity with possible

        #     new attributes found in this resultset ?

        try:

            if hasattr(req, 'is_super_session'):

                # this is a Session object which is not caching entities, so we

                # have to use a local cache to avoid recursion pb

                if _localcache is None:

                    _localcache = {}

                return _localcache[eid]

            else:

                return req.entity_cache(eid)

        except KeyError:

            pass

        # build entity instance

        etype = self.description[row][col]

        entity = self.vreg.etype_class(etype)(req, self, row, col)

        entity.set_eid(eid)

        # cache entity

        if _localcache is not None:

            _localcache[eid] = entity

        req.set_entity_cache(entity)

        eschema = entity.e_schema

        # try to complete the entity if there are some additional columns

        if len(rowvalues) > 1:

            rqlst = self.syntax_tree()

            if rqlst.TYPE == 'select':

                # UNION query, find the subquery from which this entity has been

                # found

                rqlst = rqlst.locate_subquery(col, etype, self.args)

            # take care, due to outer join support, we may find None

            # values for non final relation

            for i, attr, x in attr_desc_iterator(rqlst, col):

                if x == 'subject':

                    rschema = eschema.subject_relation(attr)

                    if rschema.is_final():

                        entity[attr] = rowvalues[i]

                        continue

                    tetype = rschema.objects(etype)[0]

                    card = rschema.rproperty(etype, tetype, 'cardinality')[0]

                else:

                    rschema = eschema.object_relation(attr)

                    tetype = rschema.subjects(etype)[0]

                    card = rschema.rproperty(tetype, etype, 'cardinality')[1]

                # only keep value if it can't be multivalued

                if card in '1?':

                    if rowvalues[i] is None:

                        if x == 'subject':

                            rql = 'Any Y WHERE X %s Y, X eid %s'

                        else:

                            rql = 'Any Y WHERE Y %s X, X eid %s'

                        rrset = ResultSet([], rql % (attr, entity.eid))

                        req.decorate_rset(rrset)

                    else:

                        rrset = self._build_entity(row, i, _localcache).as_rset()

                    entity.set_related_cache(attr, x, rrset)

        return entity

    @cached

    def syntax_tree(self):

        """get the syntax tree for the source query.