"""Explicit provisioning only; inference never imports this downloader."""
import argparse
import hashlib
import json
import os
from pathlib import Path
import urllib.request

HERE = Path(__file__).resolve().parent


def digest(path):
    with path.open("rb") as source:
        return hashlib.file_digest(source, "sha256").hexdigest()


def verified(path, spec):
    return path.is_file() and path.stat().st_size == spec["bytes"] and digest(path) == spec["sha256"]


def main():
    parser = argparse.ArgumentParser(description="Explicitly download ~136 MB of pinned, verified model artifacts")
    parser.add_argument("--model-dir", type=Path, default=HERE / "model")
    args = parser.parse_args()
    manifest = json.loads((HERE / "model-manifest.json").read_text())
    for spec in manifest["files"]:
        target = args.model_dir / spec["path"]
        if verified(target, spec):
            print(f"Verified existing {spec['path']}")
            continue
        target.parent.mkdir(parents=True, exist_ok=True)
        temporary = target.with_suffix(target.suffix + ".part")
        url = f"https://huggingface.co/{manifest['model_id']}/resolve/{manifest['revision']}/{spec['path']}"
        print(f"Downloading {spec['path']} ({spec['bytes']} bytes)", flush=True)
        try:
            request = urllib.request.Request(url, headers={"User-Agent": "Searchi-semantic-proof/0.1"})
            with urllib.request.urlopen(request, timeout=60) as response, temporary.open("wb") as output:
                total = 0
                while chunk := response.read(1024 * 1024):
                    total += len(chunk)
                    if total > spec["bytes"]:
                        raise ValueError("Download exceeds manifest size")
                    output.write(chunk)
            if not verified(temporary, spec):
                raise ValueError(f"Size or SHA256 mismatch for {spec['path']}")
            os.replace(temporary, target)
            print(f"Verified SHA256 {spec['sha256']}")
        finally:
            temporary.unlink(missing_ok=True)


if __name__ == "__main__":
    main()