"""Extract the CAN-IO board's own digital IO timeline (IN1-4/OUT1-2) from a
gateway session log, by pulling out its status frames (arbitration ID
0x100, see can-io/PROTOCOL.md) - the board sends one immediately on any
input/output change plus a 1s heartbeat, so this recovers when each
channel was high/low over the session (at that resolution - a change that
gets undone within a couple of debounce/scheduling ticks might not get its
own frame, only the surrounding samples).

Usage:
    python tools/extract_dio_timeline.py captures/gateway_20260829_164540.csv \\
        --out captures/dio_20260829.csv
"""
import argparse
import csv
from pathlib import Path

CAN_ID_STATUS = 0x100


def bits(n: int, count: int) -> str:
    return "".join(str((n >> i) & 1) for i in range(count))


def main() -> int:
    parser = argparse.ArgumentParser(description=__doc__, formatter_class=argparse.RawDescriptionHelpFormatter)
    parser.add_argument("gateway_log")
    parser.add_argument("--out", required=True, help="Output CSV path (t, inputs, outputs)")
    args = parser.parse_args()

    samples = []
    with open(args.gateway_log, newline="") as f:
        for row in csv.DictReader(f):
            if int(row["arbitration_id"], 16) != CAN_ID_STATUS:
                continue
            data = bytes.fromhex(row["data_hex"])
            if len(data) < 2:
                continue
            samples.append((float(row["t"]), data[0], data[1]))

    with open(args.out, "w", newline="") as f:
        w = csv.writer(f)
        w.writerow(["t", "inputs", "outputs"])
        for t, ins, outs in samples:
            w.writerow([t, ins, outs])

    print(f"Wrote {len(samples)} status samples to {args.out}\n")
    print("Transitions (IN1-4 / OUT1-2, bit0 first):")
    prev = None
    for t, ins, outs in samples:
        cur = (ins, outs)
        if cur != prev:
            print(f"  t={t:8.3f}s  IN={bits(ins, 4)}  OUT={bits(outs, 2)}")
            prev = cur

    return 0


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