# 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.util.date


class Usecase:
    def __init__(self, file, rel_sequence=None, lag_value=None, duration_type="WORKTIME"):
        """Assign a lag time to a sequence relationship between tasks

        A task sequence (e.g. finish to start) may optionally have a lag time
        defined. This is a fundamental concept in construction scheduling. The
        lag is defined as a duration, and the duration is typically either
        calendar based (i.e.  follows the working times and holidays of the
        calendar) or elapsed time based (i.e. 24/7).

        A sequence may only have a single lag time defined. Negative lag times
        are allowed.

        :param rel_sequence: The IfcRelSequence to assign the lag time to.
        :type rel_sequence: ifcopenshell.entity_instance.entity_instance
        :param lag_value: An ISO standardised duration string.
        :type lag_value: str
        :param duration_type: Choose from WORKTIME for the associated
            calendar-based lag times (this is the most common scenario and is
            recommended as a default), or ELAPSEDTIME to not follow the
            calendar. You may also choose NOTDEFINED but the behaviour of this
            is unclear.
        :type duration_type: str
        :return: The newly created IfcLagTime
        :rtype: ifcopenshell.entity_instance.entity_instance

        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 imagine a root construction task
            construction = ifcopenshell.api.run("sequence.add_task", model,
                work_schedule=schedule, name="Construction", identification="C")

            # Let's imagine we're doing a typically formwork, reinforcement,
            # pour sequence. Let's start with the formwork. It'll take us 2
            # days.
            formwork = ifcopenshell.api.run("sequence.add_task", model,
                parent_task=construction, name="Formwork", identification="C.1")
            time = ifcopenshell.api.run("sequence.add_task_time", model, task=formwork)
            ifcopenshell.api.run("sequence.edit_task_time", model,
                task_time=time, attributes={"ScheduleStart": "2000-01-01", "ScheduleDuration": "P2D"})

            # Now let's do the reinforcement. It'll take us another 2 days.
            reinforcement = ifcopenshell.api.run("sequence.add_task", model,
                parent_task=construction, name="Reinforcement", identification="C.2")
            time = ifcopenshell.api.run("sequence.add_task_time", model, task=reinforcement)
            ifcopenshell.api.run("sequence.edit_task_time", model,
                task_time=time, attributes={"ScheduleStart": "2000-01-01", "ScheduleDuration": "P2D"})

            # Now let's say the formwork must finish before the reinforcement
            # can start. This is a typical finish to start relationship (FS).
            sequence = ifcopenshell.api.run("sequence.assign_sequence", model,
                relating_process=formwork, related_process=reinforcement)

            # Now typically there would be no lag time between formwork and
            # reinforcement, but let's pretend that we had to allow 1 day gap
            # for whatever reason.
            ifcopenshell.api.run("sequence.assign_lag_time", model, rel_sequence=sequence, lag_value="P1D")
        """
        self.file = file
        self.settings = {
            "rel_sequence": rel_sequence,
            "lag_value": lag_value,
            "duration_type": duration_type,
        }

    def execute(self):
        lag_value = self.file.createIfcDuration(
            ifcopenshell.util.date.datetime2ifc(
                self.settings["lag_value"], "IfcDuration"
            )
        )
        lag_time = self.file.create_entity(
            "IfcLagTime",
            **{
                "DurationType": self.settings["duration_type"],
                "LagValue": lag_value,
            }
        )
        if self.settings["rel_sequence"].is_a("IfcRelSequence"):
            if (
                self.settings["rel_sequence"].TimeLag
                and len(self.file.get_inverse(self.settings["rel_sequence"].TimeLag))
                == 1
            ):
                self.file.remove(self.settings["rel_sequence"].TimeLag)
        self.settings["rel_sequence"].TimeLag = lag_time
