try:
    del App.Flatpack
except:
    pass

ad = Gui.ActiveDocument.Document

def selectionContainsAssembly():
    sel = Gui.Selection.getSelection()

    if not sel or not hasattr(sel[0], 'Type') or sel[0].Type != 'Assembly':
        return False

    return sel[0]

class FlatpackGroupViewProvider():
    def __init__(self, group):
        self.Proxy = group

class FlatpackWBTools():
    def createDatumPlaneOnLink(self, part):
        plane = part.newObject('PartDesign::Plane', 'DatumPlane')

        return plane

    def createGroup(self, asm):
        #pack = ad.addObject('App::Part', 'Flatpack')
        #pack.Type = 'Flatpack'

        #FlatpackGroupViewProvider(pack)

        #asm.Visibility = False

        self.links = self.findLinks(asm)

        assembly_bodies = []

        for link in self.links:
            if link.LinkedObject not in assembly_bodies:
                assembly_bodies.append(link.LinkedObject)

            continue

        for body in assembly_bodies:
            sketch_planes = {}
            sketch_pockets = {}
            sketch_pads = {}

            for lcs in self.findLCS(body.OutList):
                base = lcs.Placement.Base
                z = base.z

                if sketch_planes.get(z) is None:
                    # create new plane to hold sketch
                    plane = self.createDatumPlaneOnLink(body)
                    plane.Visibility = False
                    plane.Placement.Base.z = z

                    sketch_planes[z] = plane
                else:
                    plane = sketch_planes[z]

                bb = body.Shape.BoundBox
                if self.insideBB(bb, lcs.Placement.Base):
                    sketch_book = sketch_pockets
                    sketch_label = 'Inside'
                else:
                    sketch_book = sketch_pads
                    sketch_label = 'Outside'

                if sketch_book.get(z) is None:
                    sketch = self.createSketch(body, plane)
                    sketch.Visibility = False
                    sketch.Label = sketch_label
                    sketch_book[z] = sketch
                else:
                    sketch = sketch_book[z]

                tab_length = abs(bb.ZMin) + bb.ZMax

                sketch.addGeometry(Part.LineSegment(App.Vector(base.x-10, base.y - (tab_length / 2), 0), App.Vector(base.x+10, base.y - (tab_length / 2), 0)), False)
                sketch.addGeometry(Part.LineSegment(App.Vector(base.x+10, base.y - (tab_length / 2), 0), App.Vector(base.x+10, base.y + tab_length / 2, 0)), False)
                sketch.addGeometry(Part.LineSegment(App.Vector(base.x+10, base.y + tab_length / 2, 0), App.Vector(base.x-10, base.y + tab_length / 2, 0)), False)
                sketch.addGeometry(Part.LineSegment(App.Vector(base.x-10, base.y + tab_length / 2, 0), App.Vector(base.x-10, base.y - (tab_length / 2), 0)), False)

            for z in sketch_pads:
                sketch = sketch_pads[z]
                pad = link.LinkedObject.newObject('PartDesign::Pad', 'Pad')
                pad.Profile = sketch
                pad.Length = tab_length
                pad.Midplane = 1
                pad.Refine = 1

            for z in sketch_pockets:
                sketch = sketch_pockets[z]
                pad = link.LinkedObject.newObject('PartDesign::Pocket', 'Pocket')
                pad.Profile = sketch
                pad.Length = tab_length
                pad.Midplane = 1
                pad.Refine = 1

    def createSketch(self, part, attached_to):
        sketch = part.newObject('Sketcher::SketchObject', 'Sketch')

        # determine face orientation....

        sketch.Support = (attached_to, ['Face001'])
        sketch.MapMode = 'FlatFace'

        return sketch

    def findAssembly(self):
        sel = selectionContainsAssembly()

        if not sel:
            return False

        return sel

    def findLinks(self, asm, discard_origin = False):
        return [] if not asm else [el for el in asm.OutList if el.TypeId == 'App::Link']

    def findLCS(self, obj_list):
        return [ l for l in obj_list if l.TypeId == 'PartDesign::CoordinateSystem' ]

    def getLinkOwner(self, link):
        return link.LinkedObject

    def insideBB(self, bb, p):
        return (p.x > bb.XMin and p.x < bb.XMax) and (p.y > bb.YMin and p.y < bb.YMax) and (p.z > bb.ZMin and p.z < bb.ZMax)

FP = App.Flatpack = FlatpackWBTools()
asm = Gui.ActiveDocument.Document.getObject('Model')

asm = FP.findAssembly()

if asm:
    ad.openTransaction('flatpack')
    FP.createGroup(asm)
    ad.commitTransaction()
else:
    print('No Assembly selected.')

ad.recompute()