import math
import cadquery as Cq

def torsion_spring(radius=12,
                   height=20,
                   thickness=2,
                   omega=90,
                   tail_length=25):
    """
    Produces a torsion spring with abridged geometry since sweep is very slow in
    cq-editor.
    """
    base = (
        Cq.Workplane('XY')
        .cylinder(height=height, radius=radius,
                  centered=(True, True, False))
    )
    base.faces(">Z").tag("top")
    base.faces("<Z").tag("bot")
    result = (
        base
        .cylinder(height=height, radius=radius - thickness, combine='s',
                  centered=(True, True, True))
        .transformed(
            offset=(0, radius-thickness),
            rotate=(0, 0, 0))
        .box(
            length=tail_length,
            width=thickness,
            height=thickness,
            centered=False)
        .copyWorkplane(Cq.Workplane('XY'))
        .transformed(
            offset=(0, 0, height - thickness),
            rotate=(0, 0, omega))
        .center(-tail_length, radius-thickness)
        .box(
            length=tail_length,
            width=thickness,
            height=thickness,
            centered=False)
    )
    result.polyline([(0, radius, 0), (tail_length, radius, 0)],
                    forConstruction=True).tag("directrix_bot")
    c, s = math.cos(omega * math.pi / 180), math.sin(omega * math.pi / 180)
    result.polyline([
        (s * tail_length, c * radius - s * tail_length, height),
        (c * tail_length + s * radius, c * radius - s * tail_length, height)],
        forConstruction=True).tag("directrix_top")
    return result