from gerbonara import *
from shapely import *

stack = layers.LayerStack.open('/home/jaseg/proj/ihsm-strain-gage-controller-hw/pcb/gerber')
# Let's work in mm here. Gerbonara will take care to convert units when the file is in US customary units.
(x1, y1), (x2, y2) = stack.bounding_box(unit=utils.MM)

for l in [stack['bottom mask'], stack['top mask']]:

    # The solder mask gerber layer by convention is "negative". That is, a "dark" polarity (drawn) Gerber primitive
    # will result in an opening in the solder mask. Conversely, an empty gerber file would lead to the entire board
    # being covered in solder mask.
    #
    # Here, we add a rectangle covering the entire board so the entire board is *free* of solder mask.

    new = [graphic_objects.Region(
        [(x1, y1), (x1, y2), (x2, y2), (x2, y1), (x1, y1)],
        unit=utils.MM,
        polarity_dark=True)]

    # Iterate through all objects on the solder mask layer. In later KiCad versions, everything on the solder mask
    # layer is exported as a Gerber region, which is a really bad idea, but makes things easy for us here.
    for obj in l.objects:
        if not obj.polarity_dark:
            continue

        if isinstance(obj, graphic_objects.Region):
            regions = []
        else:
            regions = [graphic_objects.Region.from_arc_poly(prim.to_arc_poly())
                for prim in obj.to_primitives(unit=utils.MM)]

        for obj in regions:
            # Convert the region to a shapely line string
            ls = LineString(obj.outline).normalize()

            # Ask shapely to offset the line string by 1 mm
            out = ls.offset_curve(obj.unit(1, 'mm'))

            # For negative offsets, this operation can result in an object being split up into multiple parts, so we
            # might get back a MultiLineString instead of a LineString.
            for ls in (out.geoms if hasattr(out, 'geoms') else [out]):

                # Convert the resulting shapely object back to a Gerber region.
                new.append(graphic_objects.Region(
                    unit=obj.unit,
                    polarity_dark=not obj.polarity_dark,
                    outline=list(ls.coords)))

    # Append the new objects to the original layer data
    l.objects = new + l.objects
# Write the modified layer stack to a new Gerber directory
stack.save_to_directory('/tmp/out')