"""Moteur Joindre deux pages."""

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


def join_pages(input_path, output_path, direction="horizontal"):
    """Joindre les pages par paires.

    direction: "horizontal" (cote a cote) ou "vertical" (dessus/dessous)
    """
    reader = PdfReader(input_path)
    pages = reader.pages
    writer = PdfWriter()

    for i in range(0, len(pages), 2):
        page1 = pages[i]
        page2 = pages[i + 1] if i + 1 < len(pages) else None

        w1, h1 = get_page_size(page1)

        if page2:
            w2, h2 = get_page_size(page2)
        else:
            w2, h2 = w1, h1

        if direction == "horizontal":
            new_w = w1 + w2
            new_h = max(h1, h2)
            sheet = PageObject.create_blank_page(width=new_w, height=new_h)

            overlay1 = PageObject.create_blank_page(width=new_w, height=new_h)
            overlay1.merge_page(page1)
            sheet.merge_page(overlay1)

            if page2:
                overlay2 = PageObject.create_blank_page(width=new_w, height=new_h)
                overlay2.merge_page(page2)
                overlay2.add_transformation(Transformation().translate(w1, 0))
                sheet.merge_page(overlay2)
        else:  # vertical
            new_w = max(w1, w2)
            new_h = h1 + h2
            sheet = PageObject.create_blank_page(width=new_w, height=new_h)

            overlay1 = PageObject.create_blank_page(width=new_w, height=new_h)
            overlay1.merge_page(page1)
            overlay1.add_transformation(Transformation().translate(0, h2))
            sheet.merge_page(overlay1)

            if page2:
                overlay2 = PageObject.create_blank_page(width=new_w, height=new_h)
                overlay2.merge_page(page2)
                sheet.merge_page(overlay2)

        writer.add_page(sheet)

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