import pypdf


def main(source, out, section_length):
    assert section_length % 4 == 0
    in_reader = pypdf.PdfReader(source)
    out_writer = pypdf.PdfWriter()

    to_add = section_length - len(in_reader.pages) % section_length
    add_before = to_add // 2
    add_after = to_add - add_before

    pages = [pypdf.PageObject.create_blank_page(in_reader) for _ in range(add_before)]
    pages += in_reader.pages
    pages += [pypdf.PageObject.create_blank_page(in_reader) for _ in range(add_after)]

    for sig_start in range(0, len(in_reader.pages), section_length):
        for side in range(section_length // 4):
            top = [
                sig_start + section_length - side - 1,
                sig_start + side,
            ]
            bottom = [
                sig_start + section_length // 2 + side,
                sig_start + section_length // 2 + side - 1,
            ]

            if side % 2 != 0:
                top = list(reversed(top))
                bottom = list(reversed(bottom))


            print(top)
            print(bottom)

        continue
        for si, pi in enumerate(range(sig_start, sig_start + section_length)):
            page_box = pages[pi]
            trans = pypdf.Transformation()

            if si >= section_length // 4 and si < 3 * section_length // 4:
                trans = trans.rotate(180)

            trans = trans.scale(0.5, 0.5)