import argparse
import os
import sys


# parse_args: function definition for ScanSlicer behavior.
def parse_args(argv=None):
    parser = argparse.ArgumentParser(
        prog="scanslicer",
        description="ScanSlicer Qt UI (Wayland/X11)",
    )
    parser.add_argument(
        "path",
        nargs="?",
        help="Optional input directory containing images",
    )
    parser.add_argument(
        "--backend",
        choices=("auto", "wayland", "x11"),
        default="auto",
        help="Display backend selection (default: auto)",
    )
    return parser.parse_args(argv)


# _detect_backend_from_qpa_env: function definition for ScanSlicer behavior.
def _detect_backend_from_qpa_env():
    qpa_value = os.environ.get("QT_QPA_PLATFORM", "").strip().lower()
    if not qpa_value:
        return None

    tokens = [token.strip() for token in qpa_value.split(";") if token.strip()]
    for token in tokens:
        if token == "wayland":
            return "wayland"
        if token in ("xcb", "x11"):
            return "x11"
    return None