#!/usr/bin/env python3
"""Sample physical GPU load during a GO-authorized A/B case."""
import argparse
import json
import pathlib
import subprocess
import time


def main():
    p = argparse.ArgumentParser()
    p.add_argument("--output", type=pathlib.Path, required=True)
    p.add_argument("--interval", type=float, default=1.0)
    p.add_argument("--go", action="store_true")
    args = p.parse_args()
    if not args.go:
        p.error("No GPU monitoring before explicit --go")
    args.output.parent.mkdir(parents=True, exist_ok=True)
    cmd = ["nvidia-smi", "--query-gpu=uuid,name,memory.used,utilization.gpu,power.draw",
           "--format=csv,noheader,nounits"]
    with args.output.open("w") as out:
        while True:
            sample = subprocess.run(cmd, capture_output=True, text=True, timeout=15)
            record = {"time": time.time(), "returncode": sample.returncode,
                      "rows": [line.strip() for line in sample.stdout.splitlines() if line.strip()],
                      "error": sample.stderr.strip() if sample.returncode else ""}
            out.write(json.dumps(record) + "\n")
            out.flush()
            time.sleep(args.interval)


if __name__ == "__main__":
    main()