"""plan execution of rql queries on a single source

:organization: Logilab

:copyright: 2001-2009 LOGILAB S.A. (Paris, FRANCE), license is LGPL v2.

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

:license: GNU Lesser General Public License, v2.1 - http://www.gnu.org/licenses

"""

__docformat__ = "restructuredtext en"

from copy import copy

from rql.stmts import Union, Select

from rql.nodes import Constant

from cubicweb import QueryError, typed_eid

from cubicweb.schema import VIRTUAL_RTYPES

from cubicweb.rqlrewrite import add_types_restriction

class SSPlanner(object):

    """SingleSourcePlanner: build execution plan for rql queries

    optimized for single source repositories

    """

    def __init__(self, schema, rqlhelper):

        self.schema = schema

        self.rqlhelper = rqlhelper

    def build_plan(self, plan):

        """build an execution plan from a RQL query

        do nothing here, dispatch according to the statement type

        """

        build_plan = getattr(self, 'build_%s_plan' % plan.rqlst.TYPE)

        for step in build_plan(plan, plan.rqlst):

            plan.add_step(step)

    def build_select_plan(self, plan, rqlst):

        """build execution plan for a SELECT RQL query. Suppose only one source

        is available and so avoid work need for query decomposition among sources

        the rqlst should not be tagged at this point.

        """

        plan.preprocess(rqlst)

        return (OneFetchStep(plan, rqlst, plan.session.repo.sources),)

    def build_insert_plan(self, plan, rqlst):

        """get an execution plan from an INSERT RQL query"""

        # each variable in main variables is a new entity to insert

        to_build = {}

        session = plan.session

        etype_class = session.vreg['etypes'].etype_class

        for etype, var in rqlst.main_variables:

            # need to do this since entity class is shared w. web client code !

            to_build[var.name] = etype_class(etype)(session)

            plan.add_entity_def(to_build[var.name])

        # add constant values to entity def, mark variables to be selected

        to_select = plan.relation_definitions(rqlst, to_build)

        # add necessary steps to add relations and update attributes

        step = InsertStep(plan) # insert each entity and its relations

        step.children += self._compute_relation_steps(plan, rqlst.solutions,

                                                      rqlst.where, to_select)

        return (step,)

    def _compute_relation_steps(self, plan, solutions, restriction, to_select):

        """handle the selection of relations for an insert query"""

        for edef, rdefs in to_select.items():

            # create a select rql st to fetch needed data

            select = Select()

            eschema = edef.e_schema

            for i in range(len(rdefs)):

                rtype, term, reverse = rdefs[i]

                select.append_selected(term.copy(select))

                if reverse:

                    rdefs[i] = rtype, RelationsStep.REVERSE_RELATION

                else:

                    rschema = eschema.subjrels[rtype]

                    if rschema.final or rschema.inlined:

                        rdefs[i] = rtype, RelationsStep.FINAL

                    else:

                        rdefs[i] = rtype, RelationsStep.RELATION

            if restriction is not None:

                select.set_where(restriction.copy(select))

            step = RelationsStep(plan, edef, rdefs)

            step.children += self._select_plan(plan, select, solutions)

            yield step

    def build_delete_plan(self, plan, rqlst):

        """get an execution plan from a DELETE RQL query"""

        # build a select query to fetch entities to delete

        steps = []

        for etype, var in rqlst.main_variables:

            step = DeleteEntitiesStep(plan)

            step.children += self._sel_variable_step(plan, rqlst.solutions,

                                                     rqlst.where, etype, var)

            steps.append(step)

        for relation in rqlst.main_relations:

            step = DeleteRelationsStep(plan, relation.r_type)

            step.children += self._sel_relation_steps(plan, rqlst.solutions,

                                                      rqlst.where, relation)

            steps.append(step)

        return steps

    def _sel_variable_step(self, plan, solutions, restriction, etype, varref):

        """handle the selection of variables for a delete query"""

        select = Select()

        varref = varref.copy(select)

        select.defined_vars = {varref.name: varref.variable}

        select.append_selected(varref)

        if restriction is not None:

            select.set_where(restriction.copy(select))

        if etype != 'Any':

            select.add_type_restriction(varref.variable, etype)

        return self._select_plan(plan, select, solutions)

    def _sel_relation_steps(self, plan, solutions, restriction, relation):

        """handle the selection of relations for a delete query"""

        select = Select()

        lhs, rhs = relation.get_variable_parts()

        select.append_selected(lhs.copy(select))

        select.append_selected(rhs.copy(select))

        select.set_where(relation.copy(select))

        if restriction is not None:

            select.add_restriction(restriction.copy(select))

        return self._select_plan(plan, select, solutions)

    def build_set_plan(self, plan, rqlst):

        """get an execution plan from an SET RQL query"""

        select = Select()

        # extract variables to add to the selection

        selected_index = {}

        index = 0

        relations, attrrelations = [], []

        getrschema = self.schema.rschema

        for relation in rqlst.main_relations:

            if relation.r_type in VIRTUAL_RTYPES:

                raise QueryError('can not assign to %r relation'

                                 % relation.r_type)

            lhs, rhs = relation.get_variable_parts()

            if not lhs.as_string('utf-8') in selected_index:

                select.append_selected(lhs.copy(select))

                selected_index[lhs.as_string('utf-8')] = index

                index += 1

            if not rhs.as_string('utf-8') in selected_index:

                select.append_selected(rhs.copy(select))

                selected_index[rhs.as_string('utf-8')] = index

                index += 1

            rschema = getrschema(relation.r_type)

            if rschema.final or rschema.inlined:

                attrrelations.append(relation)

            else:

                relations.append(relation)

        # add step necessary to fetch all selected variables values

        if rqlst.where is not None:

            select.set_where(rqlst.where.copy(select))

        # set distinct to avoid potential duplicate key error

        select.distinct = True

        step = UpdateStep(plan, attrrelations, relations, selected_index)

        step.children += self._select_plan(plan, select, rqlst.solutions)

        return (step,)

    # internal methods ########################################################

    def _select_plan(self, plan, select, solutions):

        union = Union()

        union.append(select)

        select.clean_solutions(solutions)

        add_types_restriction(self.schema, select)

        self.rqlhelper.annotate(union)

        return self.build_select_plan(plan, union)

# execution steps and helper functions ########################################

def varmap_test_repr(varmap, tablesinorder):

    if varmap is None:

        return varmap

    maprepr = {}

    for var, sql in varmap.iteritems():

        table, col = sql.split('.')

        maprepr[var] = '%s.%s' % (tablesinorder[table], col)

    return maprepr

def offset_result(offset, result):

    offset -= len(result)

    if offset < 0:

        result = result[offset:]

        offset = None

    elif offset == 0:

        offset = None

        result = ()

    return offset, result

class LimitOffsetMixIn(object):

    limit = offset = None

    def set_limit_offset(self, limit, offset):

        self.limit = limit

        self.offset = offset or None

class Step(object):

    """base abstract class for execution step"""

    def __init__(self, plan):

        self.plan = plan

        self.children = []

    def execute_child(self):

        assert len(self.children) == 1

        return self.children[0].execute()

    def execute_children(self):

        for step in self.children:

            step.execute()

    def execute(self):

        """execute this step and store partial (eg this step) results"""

        raise NotImplementedError()

    def mytest_repr(self):

        """return a representation of this step suitable for test"""

        return (self.__class__.__name__,)

    def test_repr(self):

        """return a representation of this step suitable for test"""

        return self.mytest_repr() + (

            [step.test_repr() for step in self.children],)

class OneFetchStep(LimitOffsetMixIn, Step):

    """step consisting in fetching data from sources and directly returning

    results

    """

    def __init__(self, plan, union, sources, inputmap=None):

        Step.__init__(self, plan)

        self.union = union

        self.sources = sources

        self.inputmap = inputmap

        self.set_limit_offset(union.children[-1].limit, union.children[-1].offset)

    def set_limit_offset(self, limit, offset):

        LimitOffsetMixIn.set_limit_offset(self, limit, offset)

        for select in self.union.children:

            select.limit = limit

            select.offset = offset

    def execute(self):

        """call .syntax_tree_search with the given syntax tree on each

        source for each solution

        """

        self.execute_children()

        session = self.plan.session

        args = self.plan.args

        inputmap = self.inputmap

        union = self.union

        # do we have to use a inputmap from a previous step ? If so disable

        # cachekey

        if inputmap or self.plan.cache_key is None:

            cachekey = None

        # union may have been splited into subqueries, rebuild a cache key

        elif isinstance(self.plan.cache_key, tuple):

            cachekey = list(self.plan.cache_key)

            cachekey[0] = union.as_string()

            cachekey = tuple(cachekey)

        else:

            cachekey = union.as_string()

        result = []

        # limit / offset processing

        limit = self.limit

        offset = self.offset

        if offset is not None:

            if len(self.sources) > 1:

                # we'll have to deal with limit/offset by ourself

                if union.children[-1].limit:

                    union.children[-1].limit = limit + offset

                union.children[-1].offset = None

            else:

                offset, limit = None, None

        for source in self.sources:

            if offset is None and limit is not None:

                # modifying the sample rqlst is enough since sql generation

                # will pick it here as well

                union.children[-1].limit = limit - len(result)

            result_ = source.syntax_tree_search(session, union, args, cachekey,

                                                inputmap)

            if offset is not None:

                offset, result_ = offset_result(offset, result_)

            result += result_

            if limit is not None:

                if len(result) >= limit:

                    return result[:limit]

        #print 'ONEFETCH RESULT %s' % (result)

        return result

    def mytest_repr(self):

        """return a representation of this step suitable for test"""

        try:

            inputmap = varmap_test_repr(self.inputmap, self.plan.tablesinorder)

        except AttributeError:

            inputmap = self.inputmap

        return (self.__class__.__name__,

                sorted((r.as_string(kwargs=self.plan.args), r.solutions)

                       for r in self.union.children),

                self.limit, self.offset,

                sorted(self.sources), inputmap)

# UPDATE/INSERT/DELETE steps ##################################################

class RelationsStep(Step):

    """step consisting in adding attributes/relations to entity defs from a

    previous FetchStep

    relations values comes from the latest result, with one columns for

    each relation defined in self.rdefs

    for one entity definition, we'll construct N entity, where N is the

    number of the latest result

    """

    FINAL = 0

    RELATION = 1

    REVERSE_RELATION = 2

    def __init__(self, plan, edef, rdefs):

        Step.__init__(self, plan)

        # partial entity definition to expand

        self.edef = edef

        # definition of relations to complete

        self.rdefs = rdefs

    def execute(self):

        """execute this step"""

        base_edef = self.edef

        edefs = []

        result = self.execute_child()

        for row in result:

            # get a new entity definition for this row

            edef = copy(base_edef)

            # complete this entity def using row values

            for i in range(len(self.rdefs)):

                rtype, rorder = self.rdefs[i]

                if rorder == RelationsStep.FINAL:

                    edef[rtype] = row[i]

                elif rorder == RelationsStep.RELATION:

                    self.plan.add_relation_def( (edef, rtype, row[i]) )

                    edef.querier_pending_relations[(rtype, 'subject')] = row[i]

                else:

                    self.plan.add_relation_def( (row[i], rtype, edef) )

                    edef.querier_pending_relations[(rtype, 'object')] = row[i]

            edefs.append(edef)

        self.plan.substitute_entity_def(base_edef, edefs)

        return result

class InsertStep(Step):

    """step consisting in inserting new entities / relations"""

    def execute(self):

        """execute this step"""

        for step in self.children:

            assert isinstance(step, RelationsStep)

            step.plan = self.plan

            step.execute()

        # insert entities first

        result = self.plan.insert_entity_defs()

        # then relation

        self.plan.insert_relation_defs()

        # return eids of inserted entities

        return result

class DeleteEntitiesStep(Step):

    """step consisting in deleting entities"""

    def execute(self):

        """execute this step"""

        results = self.execute_child()

        todelete = frozenset(typed_eid(eid) for eid, in self.execute_child())

        session = self.plan.session

        delete = session.repo.glob_delete_entity

        # register pending eids first to avoid multiple deletion

        pending = session.transaction_data.setdefault('pendingeids', set())

        actual = todelete - pending