scripts/build_release_metadata.py

#!/usr/bin/env python3
"""Build split lists and a compact manifest for a nuScenes-NRS release.

This maintainer utility reads only the derived mask directories and (optionally)
the official sample/scene metadata. It never copies or publishes raw nuScenes
files. The generated files are deterministic when the mask directories and
metadata are unchanged.
"""

from __future__ import annotations

import argparse
import hashlib
import json
from pathlib import Path


EXPECTED = {"training": 3182, "validation": 805}


def load_json(path: Path):
    with path.open("r", encoding="utf-8") as handle:
        return json.load(handle)


def sha256_file(path: Path) -> str:
    digest = hashlib.sha256()
    with path.open("rb") as handle:
        for block in iter(lambda: handle.read(1024 * 1024), b""):
            digest.update(block)
    return digest.hexdigest()


def main() -> int:
    parser = argparse.ArgumentParser()
    parser.add_argument("--release-root", type=Path, required=True)
    parser.add_argument(
        "--metadata-dir",
        type=Path,
        default=None,
        help="Optional v1.0-trainval directory containing sample.json and scene.json",
    )
    args = parser.parse_args()
    root = args.release_root.resolve()
    split_dir = root / "splits"
    split_dir.mkdir(parents=True, exist_ok=True)

    samples = {}
    scenes = {}
    if args.metadata_dir:
        samples = {row["token"]: row for row in load_json(args.metadata_dir / "sample.json")}
        scenes = {row["token"]: row for row in load_json(args.metadata_dir / "scene.json")}

    manifest = {
        "dataset": "nuScenes-NRS",
        "release_version": "1.0.0",
        "source": {
            "dataset": "nuScenes v1.0-trainval plus the matching lidarseg release",
            "raw_data_redistributed": False,
            "camera": "CAM_FRONT",
            "lidar": "LIDAR_TOP",
        },
        "mask": {
            "format": "PNG",
            "dtype": "uint8",
            "channels": 3,
            "resolution": [1600, 900],
            "encoding_rgb": {"road": [255, 0, 0], "background": [0, 0, 0]},
            "filename": "<sample-token>.png",
        },
        "generation": {
            "lidarseg_class": 24,
            "lidarseg_class_name": "drivable_surface",
            "projection": "LiDAR_TOP -> ego -> global -> camera ego -> CAM_FRONT",
            "delaunay_max_edge_px": 40.0,
            "closing_kernel": [15, 15],
            "closing_iterations": 2,
            "douglas_peucker_factor": 0.01,
            "minimum_contour_area_px": 1000,
            "erosion_kernel": [5, 5],
            "erosion_iterations": 1,
        },
        "splits": {},
    }

    all_tokens = {}
    for split, expected in EXPECTED.items():
        mask_dir = root / split / "masks"
        files = sorted(mask_dir.glob("*.png"))
        tokens = [path.stem for path in files]
        if len(files) != expected:
            raise SystemExit(f"{split}: expected {expected} masks, found {len(files)}")
        if len(set(tokens)) != len(tokens):
            raise SystemExit(f"{split}: duplicate mask tokens")
        if any(len(token) != 32 for token in tokens):
            bad = next(token for token in tokens if len(token) != 32)
            raise SystemExit(f"{split}: non-token filename stem {bad!r}")
        split_file = split_dir / f"{split}.txt"
        split_file.write_text("".join(f"{token}\n" for token in tokens), encoding="utf-8")
        scene_tokens = set()
        scene_names = set()
        if samples:
            missing = [token for token in tokens if token not in samples]
            if missing:
                raise SystemExit(f"{split}: {len(missing)} tokens absent from sample.json")
            scene_tokens = {samples[token]["scene_token"] for token in tokens}
            scene_names = {scenes[token]["name"] for token in scene_tokens if token in scenes}
        manifest["splits"][split] = {
            "mask_count": len(files),
            "scene_count": len(scene_tokens) if samples else None,
            "scene_tokens_sha256": hashlib.sha256(
                "\n".join(sorted(scene_tokens)).encode("utf-8")
            ).hexdigest()
            if samples
            else None,
            "scene_names": sorted(scene_names) if samples else None,
            "token_list": f"splits/{split}.txt",
            "mask_directory": f"{split}/masks",
            "token_list_sha256": sha256_file(split_file),
        }
        for token in tokens:
            all_tokens.setdefault(token, []).append(split)

    overlap = sorted(token for token, splits in all_tokens.items() if len(splits) > 1)
    if overlap:
        raise SystemExit(f"training/validation overlap: {len(overlap)} tokens")
    if samples:
        train_scenes = {
            samples[token]["scene_token"]
            for token, splits in all_tokens.items()
            if splits == ["training"]
        }
        val_scenes = {
            samples[token]["scene_token"]
            for token, splits in all_tokens.items()
            if splits == ["validation"]
        }
        if train_scenes & val_scenes:
            raise SystemExit("training/validation scene overlap detected")
        manifest["split_policy"] = {
            "scene_disjoint": True,
            "training_scene_count": len(train_scenes),
            "validation_scene_count": len(val_scenes),
        }
    else:
        manifest["split_policy"] = {"scene_disjoint": None}

    manifest_path = root / "dataset_manifest.json"
    manifest_path.write_text(
        json.dumps(manifest, ensure_ascii=False, indent=2) + "\n", encoding="utf-8"
    )
    print(json.dumps({"release_root": str(root), "manifest": str(manifest_path), "masks": len(all_tokens)}, indent=2))
    return 0


if __name__ == "__main__":
    raise SystemExit(main())