src/Mod/Fem/femobjects/constraint_electricchargedensity.py

# SPDX-License-Identifier: LGPL-2.1-or-later

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# *   Copyright (c) 2025 Mario Passaglia <mpassaglia[at]cbc.uba.ar>         *
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__title__ = "FreeCAD FEM constraint electric charge density document object"
__author__ = "Mario Passaglia"
__url__ = "https://www.freecad.org"

## @package constraint_electricchargedensity
#  \ingroup FEM
#  \brief constraint electric charge density object


from FreeCAD import Units
from FreeCAD import Base

from . import base_fempythonobject

_PropHelper = base_fempythonobject._PropHelper


class ConstraintElectricChargeDensity(base_fempythonobject.BaseFemPythonObject):

    Type = "Fem::ConstraintElectricChargeDensity"

    def __init__(self, obj):
        super().__init__(obj)

        for prop in self._get_properties():
            prop.add_to_object(obj)

    def _get_properties(self):
        prop = []

        prop.append(
            _PropHelper(
                type="App::PropertyVolumeChargeDensity",
                name="SourceChargeDensity",
                group="Electric Charge Density",
                doc="Free electric charge per unit volume at the sources",
                value="0 C/mm^3",
            )
        )
        prop.append(
            _PropHelper(
                type="App::PropertySurfaceChargeDensity",
                name="InterfaceChargeDensity",
                group="Electric Charge Density",
                doc="Free electric charge per unit surface at the boundaries",
                value="0 C/mm^2",
            )
        )
        prop.append(
            _PropHelper(
                type="App::PropertyElectricCharge",
                name="TotalCharge",
                group="Electric Charge Density",
                doc="Total free electric charge",
                value="0 C",
            )
        )
        prop.append(
            _PropHelper(
                type="App::PropertyBool",
                name="Concentrated",
                group="Electric Charge Density",
                doc="Use concentrated charges at the nodes",
                value=False,
            )
        )
        prop.append(
            _PropHelper(
                type="App::PropertyEnumeration",
                name="Mode",
                group="Electric Charge Density",
                doc="Switch quantity input mode",
                value=["Interface", "Source", "Total Interface", "Total Source"],
            )
        )

        return prop

    def onDocumentRestored(self, obj):
        print("restored", obj.Name)
        # update old project with new properties
        for prop in self._get_properties():
            try:
                obj.getPropertyByName(prop.name)
            except Base.PropertyError:
                prop.add_to_object(obj)

    def onChanged(self, obj, prop):
        print("change", prop)
        if prop == "Mode":
            if obj.Mode == "Total Source":
                obj.setPropertyStatus("Concentrated", "-ReadOnly")
            else:
                obj.setPropertyStatus("Concentrated", "ReadOnly")

    def get_total_source_density(self, obj):
        """
        Calculate density for `Total Source` mode.
        """
        size = 0
        items = []
        for feat, sub_elem in obj.References:
            for name in sub_elem:
                sub = feat.getSubObject(name)
                if sub.ShapeType == "Solid":
                    size += sub.Volume
                    items.append(name)
                elif sub.ShapeType == "Face":
                    size += sub.Area
                    items.append(name)

        if items:
            vol = Units.Quantity(f"{size} mm^3")
            return obj.TotalCharge / vol

    def get_total_interface_density(self, obj):
        """
        Calculate density for `Total Interface` mode.
        """
        size = 0
        items = []
        for feat, sub_elem in obj.References:
            for name in sub_elem:
                sub = feat.getSubObject(name)
                if sub.ShapeType == "Face":
                    size += sub.Area
                    items.append(name)
                elif sub.ShapeType == "Edge":
                    size += sub.Length
                    items.append(name)

        if items:
            area = Units.Quantity(f"{size} mm^2")
            return obj.TotalCharge / area