"""Moteur Numerotation de pages."""

from pypdf import PdfReader, PdfWriter
from reportlab.pdfgen import canvas
from reportlab.lib.units import mm
from .pdf_utils import get_page_size
import io


POSITIONS = {
    "haut-gauche": ("left", "top"),
    "haut-centre": ("center", "top"),
    "haut-droite": ("right", "top"),
    "milieu-gauche": ("left", "middle"),
    "milieu-centre": ("center", "middle"),
    "milieu-droite": ("right", "middle"),
    "bas-gauche": ("left", "bottom"),
    "bas-centre": ("center", "bottom"),
    "bas-droite": ("right", "bottom"),
}


def add_page_numbers(input_path, output_path, position="bas-centre",
                     font_name="Helvetica", font_size=10, color=(0, 0, 0),
                     prefix="", suffix="", start_number=1,
                     margin_x=10*mm, margin_y=10*mm,
                     apply_to="all"):
    """Ajouter des numeros de page.

    position: cle de POSITIONS
    apply_to: "all", "even", "odd"
    """
    reader = PdfReader(input_path)
    writer = PdfWriter()

    h_align, v_align = POSITIONS.get(position, ("center", "bottom"))
    total_pages = len(reader.pages)

    for i, page in enumerate(reader.pages):
        page_num = start_number + i

        # Filtre pair/impair
        if apply_to == "even" and page_num % 2 != 0:
            writer.add_page(page)
            continue
        if apply_to == "odd" and page_num % 2 == 0:
            writer.add_page(page)
            continue

        w, h = get_page_size(page)

        # Generer le texte
        text = f"{prefix}{page_num}{suffix}"

        # Creer overlay avec le numero
        packet = io.BytesIO()
        c = canvas.Canvas(packet, pagesize=(w, h))
        c.setFont(font_name, font_size)
        c.setFillColorRGB(*color)

        # Calculer la position
        text_width = c.stringWidth(text, font_name, font_size)

        if h_align == "left":
            x = margin_x
        elif h_align == "right":
            x = w - margin_x - text_width
        else:
            x = (w - text_width) / 2

        if v_align == "top":
            y = h - margin_y - font_size
        elif v_align == "middle":
            y = (h - font_size) / 2
        else:
            y = margin_y

        c.drawString(x, y, text)
        c.showPage()
        c.save()

        packet.seek(0)
        overlay_reader = PdfReader(packet)
        page.merge_page(overlay_reader.pages[0])
        writer.add_page(page)

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