# IfcOpenShell - IFC toolkit and geometry engine
# Copyright (C) 2021 Dion Moult <dion@thinkmoult.com>
#
# This file is part of IfcOpenShell.
#
# IfcOpenShell 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 3 of the License, or
# (at your option) any later version.
#
# IfcOpenShell 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 IfcOpenShell.  If not, see <http://www.gnu.org/licenses/>.

import ifcopenshell
import ifcopenshell.api
import ifcopenshell.util.element


class Usecase:
    def __init__(self, file: ifcopenshell.file, related_objects: list[ifcopenshell.entity_instance]):
        """Unassigns related_objects from their nests.

        An object (the whole within a decomposition) is Nested by zero or one more smaller objects.
        This function will remove this nesting relationship.

        If the object is not part of a nesting relationship, nothing will happen.

        :param related_objects: The list of children of the nesting relationship,
            typically IfcElements.
        :type related_objects: list[ifcopenshell.entity_instance.entity_instance]
        :return: None
        :rtype: None

        Example:

        .. code:: python

            task = ifcopenshell.api.run("root.create_entity", model, ifc_class="IfcTasks")
            subtask1 = ifcopenshell.api.run("root.create_entity", model, ifc_class="IfcTask")
            subtask2 = ifcopenshell.api.run("root.create_entity", model, ifc_class="IfcTask")
            ifcopenshell.api.run("nest.assign_object", model, related_objects=[subtask1], relating_object=task)
            ifcopenshell.api.run("nest.assign_object", model, related_objects=[subtask2], relating_object=task)
            # nothing is returned
            rel = ifcopenshell.api.run("nest.unassign_object", model, related_objects=[subtask1])
            # nothing is returned, relationship is removed
            ifcopenshell.api.run("nest.unassign_object", model, related_objects=[subtask2])
        """
        self.file = file
        self.settings = {"related_objects": related_objects}

    def execute(self) -> None:
        related_objects = set(self.settings["related_objects"])
        rels = set(rel for object in related_objects if (rel := next((rel for rel in object.Nests), None)))

        for rel in rels:
            related_objects = set(rel.RelatedObjects) - related_objects
            if related_objects:
                rel.RelatedObjects = list(related_objects)
                ifcopenshell.api.run("owner.update_owner_history", self.file, **{"element": rel})
            else:
                history = rel.OwnerHistory
                self.file.remove(rel)
                if history:
                    ifcopenshell.util.element.remove_deep2(self.file, history)