"""Moteur Insertion de pages blanches."""

from pypdf import PdfReader, PdfWriter
from .pdf_utils import get_page_size


def insert_blank_pages(input_path, output_path, mode="after", position=None,
                       every_n=None, target_multiple=None, page_size=None):
    """Inserer des pages blanches.

    mode: "before", "after", "every_n", "pad_to_multiple"
    position: numero de page (1-based) pour before/after
    every_n: inserer apres chaque N pages
    target_multiple: arrondir au multiple de N
    page_size: (w, h) en points ou None pour meme taille que page adjacente
    """
    reader = PdfReader(input_path)
    writer = PdfWriter()

    if mode == "pad_to_multiple" and target_multiple:
        for page in reader.pages:
            writer.add_page(page)
        num = len(reader.pages)
        remainder = num % target_multiple
        if remainder != 0:
            to_add = target_multiple - remainder
            last_w, last_h = get_page_size(reader.pages[-1])
            w, h = page_size if page_size else (last_w, last_h)
            for _ in range(to_add):
                writer.add_blank_page(w, h)

    elif mode == "every_n" and every_n:
        for i, page in enumerate(reader.pages):
            writer.add_page(page)
            if (i + 1) % every_n == 0 and i + 1 < len(reader.pages):
                w, h = get_page_size(page)
                bw, bh = page_size if page_size else (w, h)
                writer.add_blank_page(bw, bh)

    elif mode in ("before", "after") and position:
        idx = position - 1  # 0-based
        for i, page in enumerate(reader.pages):
            if mode == "before" and i == idx:
                w, h = get_page_size(page)
                bw, bh = page_size if page_size else (w, h)
                writer.add_blank_page(bw, bh)
            writer.add_page(page)
            if mode == "after" and i == idx:
                w, h = get_page_size(page)
                bw, bh = page_size if page_size else (w, h)
                writer.add_blank_page(bw, bh)
    else:
        for page in reader.pages:
            writer.add_page(page)

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