import base64
from io import BytesIO

import qrcode
from django.conf import settings

from .models import Reservation


CHECK_IN_PREVIEW_PATH = "/api/check-ins/preview/"


def build_check_in_preview_url(raw_check_in_token):
    return f"{settings.SITE_BASE_URL}{CHECK_IN_PREVIEW_PATH}?token={raw_check_in_token}"


def generate_check_in_qr_png(raw_check_in_token):
    qr_image = qrcode.make(build_check_in_preview_url(raw_check_in_token))
    buffer = BytesIO()
    qr_image.save(buffer, format="PNG")
    return buffer.getvalue()


def generate_check_in_qr_base64(*, reservation, raw_check_in_token):
    if reservation.status != Reservation.Status.CONFIRMED:
        raise ValueError("QR codes are available only for confirmed reservations.")

    png_bytes = generate_check_in_qr_png(raw_check_in_token)
    encoded = base64.b64encode(png_bytes).decode("ascii")
    return f"data:image/png;base64,{encoded}"