#!/usr/bin/env python3
"""Minimal example: inspect and load slices from the UrbanFlow-oneObstacle-NoTrip HDF5 files.

Usage:
    python load_example.py path/to/file.h5
"""
import sys
import h5py


def inspect(path):
    with h5py.File(path, "r") as f:
        print(f"File: {path}\n")

        def walk(group, prefix=""):
            for key in group.keys():
                item = group[key]
                if isinstance(item, h5py.Dataset):
                    print(f"{prefix}{key}: shape={item.shape} dtype={item.dtype}")
                else:
                    print(f"{prefix}{key}/")
                    walk(item, prefix + "  ")

        walk(f)
        if f.attrs:
            print("\nattrs:", dict(f.attrs))

        # Datasets are large (the 3D Train file is ~2.1 TB) -- always slice,
        # never f["U"][:], which would try to load the whole array into RAM.
        if "U" in f:
            print("\nFirst snapshot of U, shape:", f["U"][0].shape)
            print("Sample values U[0, 0, :5, :5]:\n", f["U"][0, 0, :5, :5] if f["U"].ndim == 4 else f["U"][0, :5, :5])


if __name__ == "__main__":
    if len(sys.argv) != 2:
        print(__doc__)
        sys.exit(1)
    inspect(sys.argv[1])