First Commit

2026-05-31 10:17:09 +07:00
commit 17a9c69379
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+# 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
+
+
+def assign_lag_time(
+    file: ifcopenshell.file, rel_sequence: ifcopenshell.entity_instance, lag_value: str, duration_type: str = "WORKTIME"
+) -> ifcopenshell.entity_instance:
+    """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.
+    :param lag_value: An ISO standardised duration string.
+    :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.
+    :return: The newly created IfcLagTime
+
+    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.sequence.add_work_schedule(model, name="Construction Schedule A")
+
+        # Let's imagine a root construction task
+        construction = ifcopenshell.api.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.sequence.add_task(model,
+            parent_task=construction, name="Formwork", identification="C.1")
+        time = ifcopenshell.api.sequence.add_task_time(model, task=formwork)
+        ifcopenshell.api.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.sequence.add_task(model,
+            parent_task=construction, name="Reinforcement", identification="C.2")
+        time = ifcopenshell.api.sequence.add_task_time(model, task=reinforcement)
+        ifcopenshell.api.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.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.sequence.assign_lag_time(model, rel_sequence=sequence, lag_value="P1D")
+    """
+    duration = file.create_entity("IfcDuration", ifcopenshell.util.date.datetime2ifc(lag_value, "IfcDuration"))
+    lag_time = file.create_entity("IfcLagTime", DurationType=duration_type, LagValue=duration)
+    if rel_sequence.is_a("IfcRelSequence"):
+        if (current_lag_time := rel_sequence.TimeLag) and file.get_total_inverses(current_lag_time) == 1:
+            file.remove(current_lag_time)
+    rel_sequence.TimeLag = lag_time
+    return lag_time