# Copyright 2015, Tresys Technology, LLC
#
# SPDX-License-Identifier: LGPL-2.1-only
#
from typing import Iterable

from .descriptors import CriteriaDescriptor, CriteriaSetDescriptor
from .exception import ConstraintUseError
from .mixins import MatchObjClass, MatchPermission
from .policyrep import AnyConstraint, ConstraintRuletype
from .query import PolicyQuery
from .util import match_in_set


class ConstraintQuery(MatchObjClass, MatchPermission, PolicyQuery):

    """
    Query constraint rules, (mls)constrain/(mls)validatetrans.

    Parameter:
    policy            The policy to query.

    Keyword Parameters/Class attributes:
    ruletype          The list of rule type(s) to match.
    tclass            The object class(es) to match.
    tclass_regex      If true, use a regular expression for
                      matching the rule's object class.
    perms             The permission(s) to match.
    perms_equal       If true, the permission set of the rule
                      must exactly match the permissions
                      criteria.  If false, any set intersection
                      will match.
    perms_regex       If true, regular expression matching will be used
                      on the permission names instead of set logic.
    role              The name of the role to match in the
                      constraint expression.
    role_indirect     If true, members of an attribute will be
                      matched rather than the attribute itself.
    role_regex        If true, regular expression matching will
                      be used on the role.
    type_             The name of the type/attribute to match in the
                      constraint expression.
    type_indirect     If true, members of an attribute will be
                      matched rather than the attribute itself.
    type_regex        If true, regular expression matching will
                      be used on the type/attribute.
    user              The name of the user to match in the
                      constraint expression.
    user_regex        If true, regular expression matching will
                      be used on the user.
    """

    ruletype = CriteriaSetDescriptor(enum_class=ConstraintRuletype)
    user = CriteriaDescriptor("user_regex", "lookup_user")
    user_regex: bool = False
    role = CriteriaDescriptor("role_regex", "lookup_role")
    role_regex: bool = False
    role_indirect: bool = True
    type_ = CriteriaDescriptor("type_regex", "lookup_type_or_attr")
    type_regex: bool = False
    type_indirect: bool = True

    def _match_expr(self, expr, criteria, indirect, regex):
        """
        Match roles/types/users in a constraint expression,
        optionally by expanding the contents of attributes.

        Parameters:
        expr        The expression to match.
        criteria    The criteria to match.
        indirect    If attributes in the expression should be expanded.
        regex       If regular expression matching should be used.
        """

        if indirect:
            obj = set()
            for item in expr:
                obj.update(item.expand())
        else:
            obj = expr

        return match_in_set(obj, criteria, regex)

    def results(self) -> Iterable[AnyConstraint]:
        """Generator which yields all matching constraints rules."""
        self.log.info("Generating constraint results from {0.policy}".format(self))
        self.log.debug("Ruletypes: {0.ruletype}".format(self))
        self._match_object_class_debug(self.log)
        self._match_perms_debug(self.log)
        self.log.debug("User: {0.user!r}, regex: {0.user_regex}".format(self))
        self.log.debug("Role: {0.role!r}, regex: {0.role_regex}".format(self))
        self.log.debug("Type: {0.type_!r}, regex: {0.type_regex}".format(self))

        for c in self.policy.constraints():
            if self.ruletype:
                if c.ruletype not in self.ruletype:
                    continue

            if not self._match_object_class(c):
                continue

            try:
                if not self._match_perms(c):
                    continue
            except ConstraintUseError:
                continue

            if self.role and not self._match_expr(
                    c.expression.roles,
                    self.role,
                    self.role_indirect,
                    self.role_regex):
                continue

            if self.type_ and not self._match_expr(
                    c.expression.types,
                    self.type_,
                    self.type_indirect,
                    self.type_regex):
                continue

            if self.user and not self._match_expr(
                    c.expression.users,
                    self.user,
                    False,
                    self.user_regex):
                continue

            yield c
