# 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


class Usecase:
    def __init__(self, file, relating_process=None, related_object=None):
        """Unassigns a process and object relationship

        See ifcopenshell.api.sequence.assign_process for details.

        :param relating_process: The IfcTask in the relationship.
        :type relating_process: ifcopenshell.entity_instance.entity_instance
        :param related_object: The related object.
        :type related_object: ifcopenshell.entity_instance.entity_instance
        :return: None
        :rtype: None

        Example:

        .. code:: python

            # Let's imagine we are creating a construction schedule. All tasks
            # need to be part of a work schedule.
            schedule = ifcopenshell.api.run("sequence.add_work_schedule", model, name="Construction Schedule A")

            # Let's create a construction task. Note that the predefined type is
            # important to distinguish types of tasks.
            task = ifcopenshell.api.run("sequence.add_task", model,
                work_schedule=schedule, name="Demolish existing", identification="A", predefined_type="DEMOLITION")

            # Let's say we have a wall somewhere.
            wall = ifcopenshell.api.run("root.create_entity", model, ifc_class="IfcWall")

            # Let's demolish that wall!
            ifcopenshell.api.run("sequence.assign_process", model, relating_process=task, related_object=wall)

            # Change our mind.
            ifcopenshell.api.run("sequence.unassign_process", model, relating_process=task, related_object=wall)
        """
        self.file = file
        self.settings = {
            "relating_process": relating_process,
            "related_object": related_object,
        }

    def execute(self):
        for rel in self.settings["related_object"].HasAssignments or []:
            if (
                not rel.is_a("IfcRelAssignsToProcess")
                or rel.RelatingProcess != self.settings["relating_process"]
            ):
                continue
            if len(rel.RelatedObjects) == 1:
                return self.file.remove(rel)
            related_objects = list(rel.RelatedObjects)
            related_objects.remove(self.settings["related_object"])
            rel.RelatedObjects = related_objects
            ifcopenshell.api.run(
                "owner.update_owner_history", self.file, **{"element": rel}
            )
            return rel