"""Moteur Demonter les pages — couper en 2 sans reordonner."""

from pypdf import PdfReader, PdfWriter, PageObject, Transformation
from .pdf_utils import get_page_size


def disassemble_pages(input_path, output_path):
    """Demonter un PDF : couper chaque page en 2 moities (gauche puis droite).

    Contrairement a Delivretiser, les pages ne sont PAS remises dans l'ordre
    du livret. On obtient simplement 2x plus de pages dans l'ordre de lecture.
    """
    reader = PdfReader(input_path)
    writer = PdfWriter()

    for page in reader.pages:
        w, h = get_page_size(page)
        half_w = w / 2

        # Moitie gauche
        left_page = PageObject.create_blank_page(width=half_w, height=h)
        left_overlay = PageObject.create_blank_page(width=half_w, height=h)
        left_overlay.merge_page(page)
        left_overlay.mediabox.upper_right = (half_w, h)
        left_page.merge_page(left_overlay)
        writer.add_page(left_page)

        # Moitie droite
        right_page = PageObject.create_blank_page(width=half_w, height=h)
        right_overlay = PageObject.create_blank_page(width=half_w, height=h)
        right_overlay.merge_page(page)
        right_overlay.add_transformation(Transformation().translate(-half_w, 0))
        right_overlay.mediabox.upper_right = (half_w, h)
        right_page.merge_page(right_overlay)
        writer.add_page(right_page)

    with open(output_path, "wb") as f:
        writer.write(f)
    return output_path