# copyright 2003-2018 LOGILAB S.A. (Paris, FRANCE), all rights reserved.

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

#

# This file is part of CubicWeb.

#

# CubicWeb is free software: you can redistribute it and/or modify it under the

# terms of the GNU Lesser General Public License as published by the Free

# Software Foundation, either version 2.1 of the License, or (at your option)

# any later version.

#

# CubicWeb is distributed in the hope that it will be useful, but WITHOUT

# ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS

# FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public License for more

# details.

#

# You should have received a copy of the GNU Lesser General Public License along

# with CubicWeb.  If not, see <http://www.gnu.org/licenses/>.

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

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

from rql import nodes, stmts

from cubicweb import NotAnEntity, NoResultError, MultipleResultsError, UnknownEid

class ResultSet(object):

    """A result set wraps a RQL query result. This object implements

    partially the list protocol to allow direct use as a list of

    result rows.

    :type rowcount: int

    :param rowcount: number of rows in the result

    :type rows: list

    :param rows: list of rows of result

    :type description: list

    :param description:

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

    :type rql: str or unicode

    :param rql: the original RQL query string

    """

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

        self.rows = results

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

        # original query and arguments

        self.rql = rql

        self.args = args

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

        # maybe discarded if specified when the query has been executed

        if description is None:

            self.description = []

        else:

            self.description = description

        # 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.req = None

        # actions cache

        self._actions_cache = 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

        rows = self.rows

        if len(rows) > 10:

            rows = rows[:10] + ['...']

        if len(rows) > 1:

            # add a line break before first entity if more that one.

            pattern = '<resultset %r (%s rows):\n%s>'

        else:

            pattern = '<resultset %r (%s rows): %s>'

        if not self.description:

            return pattern % (self.rql, len(self.rows),

                              '\n'.join(str(r) for r in rows))

        return pattern % (self.rql, len(self.rows),

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

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

    def possible_actions(self, **kwargs):

        """Return possible actions on this result set. Should always be called with the same

        arguments so it may be computed only once.

        """

        if not kwargs:

            raise ValueError("ResultSet.possible_actions is expecting to receive "

                             "keywords arguments to be able to compute access to "

                             "the cache only once but you provided none.")

        key = tuple(sorted(kwargs.items()))

        if self._actions_cache is None:

            actions = self.req.vreg['actions'].poss_visible_objects(

                self.req, rset=self, **kwargs)

            self._actions_cache = (key, actions)

            return actions

        else:

            if key != self._actions_cache[0]:

                raise ValueError("ResultSet.possible_actions expects to always "

                                 "receive the same arguments to compute the "

                                 "cache once, but you've call it with the "

                                 "arguments: '%s' that aren't the same as the "

                                 "previously used combinaison '%s'" % (key, self._actions_cache[0]))

            return self._actions_cache[1]

    def __len__(self):

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

        return self.rowcount

    def __getitem__(self, i):

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

        return self.rows[i]

    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)

        rset.req = self.req

        return rset

    def copy(self, rows=None, descr=None):

        if rows is None:

            rows = self.rows[:]

            descr = self.description[:]

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

        rset.req = self.req

        return 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.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.copy(rows, descr)

        for i in range(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.copy(rows, descr)

        if col >= 0:

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

                              key=lambda t: keyfunc(t[1]), reverse=reverse)

        else:

            entities = sorted(enumerate(self),

                              key=lambda t: keyfunc(t[1]), reverse=reverse)

        for index, _ 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 sets 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.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 limited_rql(self):

        """returns 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)

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

                                                         rset=self)

        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.limited:

            rql = self._limit_offset_rql(*self.limited)

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

        # need to limit query

        else:

            rql = self.printable_rql()

        return rql

    def _limit_offset_rql(self, limit, offset):

        rqlst = self.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.args)

            # restore original limit/offset

            select.limit, select.offset = olimit, ooffset

        else:

            newselect = stmts.Select()

            newselect.limit = limit

            newselect.offset = offset

            aliases = [nodes.VariableRef(newselect.get_variable(chr(65 + i), i))

                       for i in range(len(rqlst.children[0].selection))]

            for vref in aliases:

                newselect.append_selected(nodes.VariableRef(vref.variable))

            newselect.set_with([nodes.SubQuery(aliases, rqlst)], check=False)

            newunion = stmts.Union()

            newunion.append(newselect)

            rql = newunion.as_string(kwargs=self.args)

            rqlst.parent = None

        return rql

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

        """limit the result set to the given number of rows optionally 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.cw_rset is self:

                    if offset <= entity.cw_row < stop:

                        entity.cw_row = entity.cw_row - offset

                    else:

                        entity.cw_rset = entity.as_rset()

                        entity.cw_row = entity.cw_col = 0

        else:

            rset = self.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):

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

        substitued

        """

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

    def entities(self, col=0):

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

        for i in range(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)

    all = entities

    def iter_rows_with_entities(self):

        """ iterates over rows, and for each row

        eids are converted to plain entities

        """

        for i, row in enumerate(self):

            _row = []

            for j, col in enumerate(row):

                try:

                    _row.append(self.get_entity(i, j) if col is not None else col)

                except NotAnEntity:

                    _row.append(col)

            yield _row

    def complete_entity(self, row, col=0, skip_bytes=True):

        """short cut to get an completed entity instance for a particular

        row (all instance's attributes have been fetched)