import argparse
import io
import json
from pathlib import Path

from PIL import Image
import webdataset as wds


def decode_sample(sample: dict) -> dict:
    frames = [
        Image.open(io.BytesIO(sample[f"jpg-{i:02d}"])).convert("RGB")
        for i in range(8)
    ]
    metadata = json.loads(sample["json"])
    return {
        "id": metadata["id"],
        "label": metadata["label"],
        "frames": frames,
        "__key__": sample["__key__"],
    }


def parse_args() -> argparse.Namespace:
    parser = argparse.ArgumentParser(description="Load Camera Motion WebDataset shards.")
    parser.add_argument("--dataset-root", type=Path, required=True, help="Folder containing the staged HF dataset files.")
    parser.add_argument("--split", choices=["train", "val", "test"], default="train")
    parser.add_argument("--limit", type=int, default=3, help="Number of samples to print.")
    return parser.parse_args()


def main() -> None:
    args = parse_args()
    shards = sorted(str(path) for path in args.dataset_root.glob(f"{args.split}-*.tar"))
    if not shards:
        raise SystemExit(f"No shards found for split {args.split} in {args.dataset_root}")

    dataset = wds.WebDataset(shards, shardshuffle=False).map(decode_sample)
    for index, sample in enumerate(dataset):
        print(
            json.dumps(
                {
                    "index": index,
                    "id": sample["id"],
                    "label": sample["label"],
                    "num_frames": len(sample["frames"]),
                    "frame_size": sample["frames"][0].size,
                    "webdataset_key": sample["__key__"],
                },
                indent=2,
            )
        )
        if index + 1 >= args.limit:
            break


if __name__ == "__main__":
    main()