# 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/>.

"""RQL rewriting utilities : insert rql expression snippets into rql syntax

tree.

This is used for instance for read security checking in the repository.

"""

__docformat__ = "restructuredtext en"

from rql import nodes as n, stmts, TypeResolverException

from rql.utils import common_parent

from yams import BadSchemaDefinition

from logilab.common.graph import has_path

from cubicweb import Unauthorized, typed_eid

def add_types_restriction(schema, rqlst, newroot=None, solutions=None):

    if newroot is None:

        assert solutions is None

        if hasattr(rqlst, '_types_restr_added'):

            return

        solutions = rqlst.solutions

        newroot = rqlst

        rqlst._types_restr_added = True

    else:

        assert solutions is not None

        rqlst = rqlst.stmt

    eschema = schema.eschema

    allpossibletypes = {}

    for solution in solutions:

        for varname, etype in solution.iteritems():

            # XXX not considering aliases by design, right ?

            if varname not in newroot.defined_vars or eschema(etype).final:

                continue

            allpossibletypes.setdefault(varname, set()).add(etype)

    for varname in sorted(allpossibletypes):

        var = newroot.defined_vars[varname]

        stinfo = var.stinfo

        if stinfo.get('uidrel') is not None:

            continue # eid specified, no need for additional type specification

        try:

            typerel = rqlst.defined_vars[varname].stinfo.get('typerel')

        except KeyError:

            assert varname in rqlst.aliases

            continue

        if newroot is rqlst and typerel is not None:

            mytyperel = typerel

        else:

            for vref in var.references():

                rel = vref.relation()

                if rel and rel.is_types_restriction():

                    mytyperel = rel

                    break

            else:

                mytyperel = None

        possibletypes = allpossibletypes[varname]

        if mytyperel is not None:

            # variable as already some types restriction. new possible types

            # can only be a subset of existing ones, so only remove no more

            # possible types

            for cst in mytyperel.get_nodes(n.Constant):

                if not cst.value in possibletypes:

                    cst.parent.remove(cst)

        else:

            # we have to add types restriction

            if stinfo.get('scope') is not None:

                rel = var.scope.add_type_restriction(var, possibletypes)

            else:

                # tree is not annotated yet, no scope set so add the restriction

                # to the root

                rel = newroot.add_type_restriction(var, possibletypes)

            stinfo['typerel'] = rel

        stinfo['possibletypes'] = possibletypes

def remove_solutions(origsolutions, solutions, defined):

    """when a rqlst has been generated from another by introducing security

    assertions, this method returns solutions which are contained in orig

    solutions

    """

    newsolutions = []

    for origsol in origsolutions:

        for newsol in solutions[:]:

            for var, etype in origsol.items():

                try:

                    if newsol[var] != etype:

                        try:

                            defined[var].stinfo['possibletypes'].remove(newsol[var])

                        except KeyError:

                            pass

                        break

                except KeyError:

                    # variable has been rewritten

                    continue

            else:

                newsolutions.append(newsol)

                solutions.remove(newsol)

    return newsolutions

class Unsupported(Exception):

    """raised when an rql expression can't be inserted in some rql query

    because it create an unresolvable query (eg no solutions found)

    """

class RQLRewriter(object):

    """insert some rql snippets into another rql syntax tree

    this class *isn't thread safe*

    """

    def __init__(self, session):

        self.session = session

        vreg = session.vreg

        self.schema = vreg.schema

        self.annotate = vreg.rqlhelper.annotate

        self._compute_solutions = vreg.solutions

    def compute_solutions(self):

        self.annotate(self.select)

        try:

            self._compute_solutions(self.session, self.select, self.kwargs)

        except TypeResolverException:

            raise Unsupported(str(self.select))

        if len(self.select.solutions) < len(self.solutions):

            raise Unsupported()

    def rewrite(self, select, snippets, solutions, kwargs, existingvars=None):

        """

        snippets: (varmap, list of rql expression)

                  with varmap a *tuple* (select var, snippet var)

        """

        self.select = select

        self.solutions = solutions

        self.kwargs = kwargs

        self.u_varname = None

        self.removing_ambiguity = False

        self.exists_snippet = {}

        self.pending_keys = []

        self.existingvars = existingvars

        self._insert_scope = None

        # we have to annotate the rqlst before inserting snippets, even though

        # we'll have to redo it latter

        self.annotate(select)

        self.insert_snippets(snippets)

        if not self.exists_snippet and self.u_varname:

            # U has been inserted than cancelled, cleanup

            select.undefine_variable(select.defined_vars[self.u_varname])

        # clean solutions according to initial solutions

        newsolutions = remove_solutions(solutions, select.solutions,

                                        select.defined_vars)

        assert len(newsolutions) >= len(solutions), (

            'rewritten rql %s has lost some solutions, there is probably '

            'something wrong in your schema permission (for instance using a '

            'RQLExpression which insert a relation which doesn\'t exists in '

            'the schema)\nOrig solutions: %s\nnew solutions: %s' % (

            select, solutions, newsolutions))

        if len(newsolutions) > len(solutions):

            newsolutions = self.remove_ambiguities(snippets, newsolutions)

        select.solutions = newsolutions

        add_types_restriction(self.schema, select)

    def insert_snippets(self, snippets, varexistsmap=None):

        self.rewritten = {}

        for varmap, rqlexprs in snippets:

            if isinstance(varmap, dict):

                varmap = tuple(sorted(varmap.items()))

            else:

                assert isinstance(varmap, tuple), varmap

            if varexistsmap is not None and not varmap in varexistsmap:

                continue

            self.insert_varmap_snippets(varmap, rqlexprs, varexistsmap)

    def insert_varmap_snippets(self, varmap, rqlexprs, varexistsmap):

        self.varmap = varmap

        self.revvarmap = {}

        self.varinfos = []

        for i, (selectvar, snippetvar) in enumerate(varmap):

            assert snippetvar in 'SOX'

            self.revvarmap[snippetvar] = (selectvar, i)

            vi = {}

            self.varinfos.append(vi)

            try:

                vi['const'] = typed_eid(selectvar) # XXX gae

                vi['rhs_rels'] = vi['lhs_rels'] = {}

            except ValueError:

                try:

                    vi['stinfo'] = sti = self.select.defined_vars[selectvar].stinfo

                except KeyError:

                    # variable may have been moved to a newly inserted subquery

                    # we should insert snippet in that subquery

                    subquery = self.select.aliases[selectvar].query

                    assert len(subquery.children) == 1

                    subselect = subquery.children[0]

                    RQLRewriter(self.session).rewrite(subselect, [(varmap, rqlexprs)],

                                                      subselect.solutions, self.kwargs)

                    return

                if varexistsmap is None:

                    vi['rhs_rels'] = dict( (r.r_type, r) for r in sti['rhsrelations'])

                    vi['lhs_rels'] = dict( (r.r_type, r) for r in sti['relations']

                                           if not r in sti['rhsrelations'])

                else:

                    vi['rhs_rels'] = vi['lhs_rels'] = {}

        parent = None

        inserted = False

        for rqlexpr in rqlexprs:

            self.current_expr = rqlexpr

            if varexistsmap is None:

                try:

                    new = self.insert_snippet(varmap, rqlexpr.snippet_rqlst, parent)

                except Unsupported:

                    continue

                inserted = True

                if new is not None:

                    self.exists_snippet[rqlexpr] = new

                parent = parent or new

            else:

                # called to reintroduce snippet due to ambiguity creation,

                # so skip snippets which are not introducing this ambiguity

                exists = varexistsmap[varmap]

                if self.exists_snippet[rqlexpr] is exists:

                    self.insert_snippet(varmap, rqlexpr.snippet_rqlst, exists)

        if varexistsmap is None and not inserted:

            # no rql expression found matching rql solutions. User has no access right

            raise Unauthorized() # XXX bad constraint when inserting constraints

    def insert_snippet(self, varmap, snippetrqlst, parent=None):

        new = snippetrqlst.where.accept(self)

        existing = self.existingvars

        self.existingvars = None

        try:

            return self._insert_snippet(varmap, parent, new)

        finally:

            self.existingvars = existing

    def _insert_snippet(self, varmap, parent, new):

        if new is not None:

            if self._insert_scope is None:

                insert_scope = None

                for vi in self.varinfos:

                    scope = vi.get('stinfo', {}).get('scope', self.select)

                    if insert_scope is None:

                        insert_scope = scope

                    else:

                        insert_scope = common_parent(scope, insert_scope)

            else:

                insert_scope = self._insert_scope

            if any(vi.get('stinfo', {}).get('optrelations') for vi in self.varinfos):

                assert parent is None

                self._insert_scope = self.snippet_subquery(varmap, new)

                self.insert_pending()

                self._insert_scope = None

                return

            if not isinstance(new, (n.Exists, n.Not)):

                new = n.Exists(new)

            if parent is None:

                insert_scope.add_restriction(new)

            else:

                grandpa = parent.parent

                or_ = n.Or(parent, new)

                grandpa.replace(parent, or_)

            if not self.removing_ambiguity:

                try:

                    self.compute_solutions()

                except Unsupported:

                    # some solutions have been lost, can't apply this rql expr

                    if parent is None:

                        self.select.remove_node(new, undefine=True)

                    else:

                        parent.parent.replace(or_, or_.children[0])

                        self._cleanup_inserted(new)

                    raise

                else:

                    self._insert_scope = new

                    self.insert_pending()

                    self._insert_scope = None

            return new

        self.insert_pending()

    def insert_pending(self):

        """pending_keys hold variable referenced by U has_<action>_permission X

        relation.

        Once the snippet introducing this has been inserted and solutions

        recomputed, we have to insert snippet defined for <action> of entity

        types taken by X

        """

        while self.pending_keys:

            key, action = self.pending_keys.pop()

            try:

                varname = self.rewritten[key]

            except KeyError:

                try:

                    varname = self.revvarmap[key[-1]][0]

                except KeyError:

                    # variable isn't used anywhere else, we can't insert security

                    raise Unauthorized()

            ptypes = self.select.defined_vars[varname].stinfo['possibletypes']

            if len(ptypes) > 1:

                # XXX dunno how to handle this

                self.session.error(

                    'cant check security of %s, ambigous type for %s in %s',

                    self.select, varname, key[0]) # key[0] == the rql expression

                raise Unauthorized()

            etype = iter(ptypes).next()

            eschema = self.schema.eschema(etype)

            if not eschema.has_perm(self.session, action):

                rqlexprs = eschema.get_rqlexprs(action)

                if not rqlexprs:

                    raise Unauthorized()

                self.insert_snippets([({varname: 'X'}, rqlexprs)])

    def snippet_subquery(self, varmap, transformedsnippet):

        """introduce the given snippet in a subquery"""

        subselect = stmts.Select()

        snippetrqlst = n.Exists(transformedsnippet.copy(subselect))

        aliases = []

        rels_done = set()

        for i, (selectvar, snippetvar) in enumerate(varmap):

            subselectvar = subselect.get_variable(selectvar)

            subselect.append_selected(n.VariableRef(subselectvar))

            aliases.append(selectvar)

            vi = self.varinfos[i]

            need_null_test = False

            stinfo = vi['stinfo']

            for rel in stinfo['relations']:

                if rel in rels_done:

                    continue

                rels_done.add(rel)

                rschema = self.schema.rschema(rel.r_type)

                if rschema.final or (rschema.inlined and

                                     not rel in stinfo['rhsrelations']):

                    rel.children[0].name = selectvar # XXX explain why

                    subselect.add_restriction(rel.copy(subselect))

                    for vref in rel.children[1].iget_nodes(n.VariableRef):

                        if isinstance(vref.variable, n.ColumnAlias):

                            # XXX could probably be handled by generating the

                            # subquery into the detected subquery

                            raise BadSchemaDefinition(

                                "cant insert security because of usage two inlined "

                                "relations in this query. You should probably at "

                                "least uninline %s" % rel.r_type)

                        subselect.append_selected(vref.copy(subselect))

                        aliases.append(vref.name)

                    self.select.remove_node(rel)

                    # when some inlined relation has to be copied in the

                    # subquery, we need to test that either value is NULL or

                    # that the snippet condition is satisfied

                    if rschema.inlined and rel.optional:

                        need_null_test = True

            if need_null_test:

                snippetrqlst = n.Or(

                    n.make_relation(subselectvar, 'is', (None, None), n.Constant,

                                    operator='='),

                    snippetrqlst)