"""Expliziter, SHA-256-geprüfter Download des lokalen Erkennungsmodells."""

import argparse
import hashlib
import json
import os
from pathlib import Path
import tempfile
import urllib.request


def main():
    root = Path(__file__).resolve().parent.parent
    parser = argparse.ArgumentParser(description=__doc__)
    parser.add_argument("--state-dir", type=Path, default=Path(os.environ.get("HALLOWEEN_STATE_DIR", root / "data")))
    args = parser.parse_args()
    manifest = json.loads((root / "halloween/nanodet-model.json").read_text())
    target = args.state_dir / "models" / manifest["file"]
    if target.exists() and hashlib.sha256(target.read_bytes()).hexdigest() == manifest["sha256"]:
        print(f"Modell bereits geprüft: {target}")
        return
    target.parent.mkdir(parents=True, exist_ok=True)
    temp = None
    try:
        with tempfile.NamedTemporaryFile(dir=target.parent, delete=False) as output:
            temp = Path(output.name)
            digest, size = hashlib.sha256(), 0
            with urllib.request.urlopen(manifest["url"], timeout=30) as response:
                while block := response.read(65536):
                    size += len(block)
                    if size > manifest["size"]:
                        raise ValueError("Modell größer als erwartet")
                    digest.update(block)
                    output.write(block)
            if size != manifest["size"] or digest.hexdigest() != manifest["sha256"]:
                raise ValueError("Modell-Prüfsumme oder Größe stimmt nicht")
            output.flush()
            os.fsync(output.fileno())
        os.replace(temp, target)
        print(f"Modell installiert und SHA-256 geprüft: {target}")
    finally:
        if temp is not None:
            temp.unlink(missing_ok=True)


if __name__ == "__main__":
    main()