"""Convert a gateway session log (t, direction, arbitration_id, is_extended,
dlc, data_hex, relayed) into a plain capture CSV (timestamp_ms,
arbitration_id, is_extended, dlc, data_hex) that replay_source.py /
gateway/replay_to_bus.py can play back.

Usage:
    python tools/gateway_log_to_capture.py captures/gateway_20260829_164540.csv \\
        --direction car->eps --out captures/replay_car_to_eps.csv

Only rows that were actually relayed are kept by default (--include-blocked
to keep everything, e.g. to inspect what was withheld).
"""
import argparse
import csv
import sys
from pathlib import Path


def main() -> int:
    parser = argparse.ArgumentParser(description=__doc__, formatter_class=argparse.RawDescriptionHelpFormatter)
    parser.add_argument("gateway_log", help="Gateway session CSV to convert")
    parser.add_argument("--direction", default="car->eps", choices=["car->eps", "eps->car"])
    parser.add_argument("--out", required=True, help="Output capture CSV path")
    parser.add_argument("--include-blocked", action="store_true", help="Also keep frames that were NOT relayed")
    args = parser.parse_args()

    src = Path(args.gateway_log)
    out = Path(args.out)

    written = 0
    with open(src, newline="") as fin, open(out, "w", newline="") as fout:
        reader = csv.DictReader(fin)
        writer = csv.writer(fout)
        writer.writerow(["timestamp_ms", "arbitration_id", "is_extended", "dlc", "data_hex"])
        for row in reader:
            if row["direction"] != args.direction:
                continue
            if not args.include_blocked and row["relayed"] != "1":
                continue
            writer.writerow(
                [
                    round(float(row["t"]) * 1000),
                    row["arbitration_id"],
                    row["is_extended"],
                    row["dlc"],
                    row["data_hex"],
                ]
            )
            written += 1

    print(f"Wrote {written} frames ({args.direction}) to {out}", file=sys.stderr)
    return 0


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