# copyright 2003-2011 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/>.

"""Defines the diferent querier steps usable in plans.

FIXME : this code needs refactoring. Some problems :

* get data from the parent plan, the latest step, temporary table...

* each step has is own members (this is not necessarily bad, but a bit messy

  for now)

"""

from __future__ import with_statement

__docformat__ = "restructuredtext en"

from rql.nodes import VariableRef, Variable, Function

from cubicweb.server.ssplanner import (LimitOffsetMixIn, Step, OneFetchStep,

                                    varmap_test_repr, offset_result)

AGGR_TRANSFORMS = {'COUNT':'SUM', 'MIN':'MIN', 'MAX':'MAX', 'SUM': 'SUM'}

class remove_and_restore_clauses(object):

    def __init__(self, union, keepgroup):

        self.union = union

        self.keepgroup = keepgroup

        self.clauses = None

    def __enter__(self):

        self.clauses = clauses = []

        for select in self.union.children:

            if self.keepgroup:

                having, orderby = select.having, select.orderby

                select.having, select.orderby = (), ()

                clauses.append( (having, orderby) )

            else:

                groupby, having, orderby = select.groupby, select.having, select.orderby

                select.groupby, select.having, select.orderby = (), (), ()

                clauses.append( (groupby, having, orderby) )

    def __exit__(self, exctype, exc, traceback):

        for i, select in enumerate(self.union.children):

            if self.keepgroup:

                select.having, select.orderby = self.clauses[i]

            else:

                select.groupby, select.having, select.orderby = self.clauses[i]

class FetchStep(OneFetchStep):

    """step consisting in fetching data from sources, and storing result in

    a temporary table

    """

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

        OneFetchStep.__init__(self, plan, union, sources)

        # temporary table to store step result

        self.table = table

        # should groupby clause be kept or not

        self.keepgroup = keepgroup

        # variables mapping to use as input

        self.inputmap = inputmap

        # output variable mapping

        srqlst = union.children[0] # sample select node

        # add additional information to the output mapping

        self.outputmap = plan.init_temp_table(table, srqlst.selection,

                                              srqlst.solutions[0])

        for vref in srqlst.selection:

            if not isinstance(vref, VariableRef):

                continue

            var = vref.variable

            if var.stinfo.get('attrvars'):

                for lhsvar, rtype in var.stinfo['attrvars']:

                    if lhsvar.name in srqlst.defined_vars:

                        key = '%s.%s' % (lhsvar.name, rtype)

                        self.outputmap[key] = self.outputmap[var.name]

            else:

                rschema = self.plan.schema.rschema

                for rel in var.stinfo['rhsrelations']:

                    if rschema(rel.r_type).inlined:

                        lhsvar = rel.children[0]

                        if lhsvar.name in srqlst.defined_vars:

                            key = '%s.%s' % (lhsvar.name, rel.r_type)

                            self.outputmap[key] = self.outputmap[var.name]

    def execute(self):

        """execute this step"""

        self.execute_children()

        plan = self.plan

        plan.create_temp_table(self.table)

        union = self.union

        with remove_and_restore_clauses(union, self.keepgroup):

            for source in self.sources:

                source.flying_insert(self.table, plan.session, union, plan.args,

                                     self.inputmap)

    def mytest_repr(self):

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

        with remove_and_restore_clauses(self.union, self.keepgroup):

            try:

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

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

            except AttributeError:

                inputmap = self.inputmap

                outputmap = self.outputmap

            return (self.__class__.__name__,

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

                           for r in self.union.children),

                    sorted(self.sources), inputmap, outputmap)

class AggrStep(LimitOffsetMixIn, Step):

    """step consisting in making aggregat from temporary data in the system

    source

    """

    def __init__(self, plan, selection, select, table, outputtable=None):

        Step.__init__(self, plan)

        # original selection

        self.selection = selection

        # original Select RQL tree

        self.select = select

        # table where are located temporary results

        self.table = table

        # optional table where to write results

        self.outputtable = outputtable

        if outputtable is not None:

            plan.init_temp_table(outputtable, selection, select.solutions[0])

        #self.inputmap = inputmap

    def mytest_repr(self):

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

        try:

            # rely on a monkey patch (cf unittest_querier)

            table = self.plan.tablesinorder[self.table]

            outputtable = self.outputtable and self.plan.tablesinorder[self.outputtable]

        except AttributeError:

            # not monkey patched

            table = self.table

            outputtable = self.outputtable

        sql = self.get_sql().replace(self.table, table)

        return (self.__class__.__name__, sql, outputtable)

    def execute(self):

        """execute this step"""

        self.execute_children()

        sql = self.get_sql()

        if self.outputtable:

            self.plan.create_temp_table(self.outputtable)

            sql = 'INSERT INTO %s %s' % (self.outputtable, sql)

            self.plan.syssource.doexec(self.plan.session, sql, self.plan.args)

        else:

            return self.plan.sqlexec(sql, self.plan.args)

    def get_sql(self):

        self.inputmap = inputmap = self.children[-1].outputmap

        dbhelper=self.plan.syssource.dbhelper

        # get the select clause

        clause = []

        for i, term in enumerate(self.selection):

            try:

                var_name = inputmap[term.as_string()]

            except KeyError:

                var_name = 'C%s' % i

            if isinstance(term, Function):

                # we have to translate some aggregat function

                # (for instance COUNT -> SUM)

                orig_name = term.name

                try:

                    term.name = AGGR_TRANSFORMS[term.name]

                    # backup and reduce children

                    orig_children = term.children

                    term.children = [VariableRef(Variable(var_name))]

                    clause.append(term.accept(self))

                    # restaure the tree XXX necessary?

                    term.name = orig_name

                    term.children = orig_children

                except KeyError:

                    clause.append(var_name)

            else:

                clause.append(var_name)

                for vref in term.iget_nodes(VariableRef):

                    inputmap[vref.name] = var_name

        # XXX handle distinct with non selected sort term

        if self.select.distinct:

            sql = ['SELECT DISTINCT %s' % ', '.join(clause)]

        else:

            sql = ['SELECT %s' % ', '.join(clause)]

        sql.append("FROM %s" % self.table)

        # get the group/having clauses

        if self.select.groupby:

            clause = [inputmap[var.name] for var in self.select.groupby]

            grouped = set(var.name for var in self.select.groupby)

            sql.append('GROUP BY %s' % ', '.join(clause))

        else:

            grouped = None

        if self.select.having:

            clause = [term.accept(self) for term in self.select.having]

            sql.append('HAVING %s' % ', '.join(clause))

        # get the orderby clause

        if self.select.orderby:

            clause = []

            for sortterm in self.select.orderby:

                sqlterm = sortterm.term.accept(self)

                if sortterm.asc:

                    clause.append(sqlterm)

                else:

                    clause.append('%s DESC' % sqlterm)

                if grouped is not None:

                    for vref in sortterm.iget_nodes(VariableRef):

                        if not vref.name in grouped:

                            sql[-1] += ', ' + self.inputmap[vref.name]

                            grouped.add(vref.name)

            sql = dbhelper.sql_add_order_by(' '.join(sql),

                                            clause,

                                            None, False,

                                            self.limit or self.offset)

        else:

            sql = ' '.join(sql)

            clause = None

        sql = dbhelper.sql_add_limit_offset(sql, self.limit, self.offset, clause)

        return sql

    def visit_function(self, function):

        """generate SQL name for a function"""

        try:

            return self.children[0].outputmap[str(function)]

        except KeyError:

            return '%s(%s)' % (function.name,

                               ','.join(c.accept(self) for c in function.children))

    def visit_variableref(self, variableref):

        """get the sql name for a variable reference"""

        try:

            return self.inputmap[variableref.name]

        except KeyError: # XXX duh? explain

            return variableref.variable.name

    def visit_constant(self, constant):

        """generate SQL name for a constant"""

        assert constant.type == 'Int'

        return str(constant.value)

class UnionStep(LimitOffsetMixIn, Step):

    """union results of child in-memory steps (e.g. OneFetchStep / AggrStep)"""

    def execute(self):

        """execute this step"""

        result = []

        limit = olimit = self.limit

        offset = self.offset

        assert offset != 0

        if offset is not None:

            limit = limit + offset

        for step in self.children:

            if limit is not None:

                if offset is None:

                    limit = olimit - len(result)

                step.set_limit_offset(limit, None)

            result_ = step.execute()

            if offset is not None:

                offset, result_ = offset_result(offset, result_)

            result += result_

            if limit is not None:

                if len(result) >= olimit:

                    return result[:olimit]

        return result

    def mytest_repr(self):

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

        return (self.__class__.__name__, self.limit, self.offset)

class IntersectStep(UnionStep):

    """return intersection of results of child in-memory steps (e.g. OneFetchStep / AggrStep)"""

    def execute(self):

        """execute this step"""

        result = set()

        for step in self.children:

            result &= frozenset(step.execute())

        result = list(result)

        if self.offset:

            result = result[self.offset:]

        if self.limit:

            result = result[:self.limit]

        return result

class UnionFetchStep(Step):

    """union results of child steps using temporary tables (e.g. FetchStep)"""

    def execute(self):

        """execute this step"""

        self.execute_children()

__all__ = ('FetchStep', 'AggrStep', 'UnionStep', 'UnionFetchStep', 'IntersectStep')