"""Read one sample from a shard with nothing but the standard library, safetensors and zstd.

    python examples/read_one_sample.py data/validation/validation-00000-of-00001.tar
"""
import io
import json
import sys
import tarfile

import zstandard
from safetensors.numpy import load as st_load

COMPRESSED = {"mesh.safetensors", "queries.safetensors", "visibility.safetensors",
              "meta.json"}


def members_of_first_sample(tar_path):
    """The tar is written so a sample's members are always adjacent."""
    with tarfile.open(tar_path, "r:") as tf:
        key, out = None, {}
        for m in tf:
            if not m.isfile():
                continue
            k = m.name.rsplit("/", 1)[-1].split(".", 1)[0]
            if key is None:
                key = k
            if k != key:
                break
            name = m.name.rsplit("/", 1)[-1][len(k) + 1:]
            out[name] = tf.extractfile(m).read()
        return key, out


def decode(name, blob):
    if name.endswith(".zst"):
        blob, name = zstandard.ZstdDecompressor().decompress(blob), name[:-4]
    if name == "meta.json":
        return json.loads(blob)
    if name.endswith(".safetensors"):
        return st_load(blob)
    return blob                                     # a PNG, still encoded


if __name__ == "__main__":
    uid, raw = members_of_first_sample(sys.argv[1])
    payload = {}
    for name, blob in raw.items():
        clean = name[:-4] if name.endswith(".zst") else name
        payload[clean] = decode(name, blob)

    print(f"uid {uid}")
    mesh, q = payload["mesh.safetensors"], payload["queries.safetensors"]
    print(f"  faces {mesh['faces'].shape[0]:,}  vertices {mesh['vertices'].shape[0]:,}")
    for fam in ("xatlas", "smart_uv", "partial"):
        valid = (q[f"{fam}_valid_mask"] > 0).mean()
        print(f"  {fam:9s} texture {q[f'{fam}_gt_texture'].shape} "
              f"valid {valid:.1%}")
    vis = payload["visibility.safetensors"]["xatlas_vis"]
    print(f"  visibility {vis.shape}  visible texels per view "
          f"{[int((vis[i] == 2).sum()) for i in range(vis.shape[0])]}")
    views = [k for k in payload if k.endswith(".png")]
    print(f"  views {sorted(views)}")
    meta = payload["meta.json"]
    print(f"  release {meta.get('release_version')}  schema {meta.get('schema_version')}")