"""GPU load readout via nvidia-smi (present in the container thanks to the
NVIDIA Container Toolkit's `utility` capability). Returns None if unavailable —
the UI just shows n/a (e.g. CPU-fallback run)."""
import subprocess


def read_gpu() -> dict | None:
    try:
        out = subprocess.run(
            [
                "nvidia-smi",
                "--query-gpu=utilization.gpu,memory.used,memory.total,temperature.gpu",
                "--format=csv,noheader,nounits",
            ],
            capture_output=True, text=True, timeout=5, check=True,
        ).stdout.strip().splitlines()
    except (OSError, subprocess.SubprocessError):
        return None
    if not out:
        return None
    parts = [p.strip() for p in out[0].split(",")]
    try:
        return {
            "util_pct": int(float(parts[0])),
            "mem_used_mb": int(float(parts[1])),
            "mem_total_mb": int(float(parts[2])),
            "temp_c": int(float(parts[3])),
        }
    except (ValueError, IndexError):
        return None