"""Work out the message order that precedes the EPS coming online.

Takes a gateway session log where the EPS *did* wake up, finds the moment
it first transmits (its own IDs, not relayed car traffic), and reports what
the car sent before that - first-seen times, and how the CAS terminal
message 0x130 progressed. That progression is the thing a synthetic
transmit set has to reproduce: a static payload can't walk the EPS through
the same states the car does.

Usage:
    python tools/analyze_startup_order.py captures/gateway_20260829_164540.csv
"""
import argparse
import csv
from collections import defaultdict
from pathlib import Path

# The EPS's own transmissions, per eps-comms/findings.md. 0x100 is our
# CAN-IO board's status frame, so it is deliberately not in this set.
EPS_IDS = {0x1FB, 0x4B0, 0x5B0}

TERMINAL = {0x00: "off", 0x40: "terminal_R", 0x41: "terminal_15",
            0x45: "engine_running", 0x55: "cranking", 0x80: "wake_up"}


def main() -> int:
    parser = argparse.ArgumentParser(description=__doc__, formatter_class=argparse.RawDescriptionHelpFormatter)
    parser.add_argument("gateway_log")
    parser.add_argument("--window", type=float, default=None,
                        help="Only consider car frames within N seconds before the EPS wakes")
    args = parser.parse_args()

    rows = []
    with open(args.gateway_log, newline="") as f:
        for row in csv.DictReader(f):
            rows.append((float(row["t"]), row["direction"], int(row["arbitration_id"], 16),
                         bytes.fromhex(row["data_hex"])))
    rows.sort(key=lambda r: r[0])

    wake = next((t for t, d, aid, _ in rows if d == "eps->car" and aid in EPS_IDS), None)
    if wake is None:
        print("The EPS never transmitted in this log - pick one where it came online.")
        return 1
    print(f"EPS first transmits at t={wake:.3f}s\n")

    first_seen = {}
    counts = defaultdict(int)
    for t, direction, aid, _ in rows:
        if direction != "car->eps":
            continue
        counts[aid] += 1
        first_seen.setdefault(aid, t)

    before = {aid: t for aid, t in first_seen.items() if t < wake}
    after = {aid: t for aid, t in first_seen.items() if t >= wake}
    if args.window is not None:
        before = {aid: t for aid, t in before.items() if t >= wake - args.window}

    print(f"Car IDs present BEFORE the EPS woke ({len(before)}):")
    for aid, t in sorted(before.items(), key=lambda kv: kv[1]):
        print(f"  t={t:7.3f}s  0x{aid:03X}  ({counts[aid]} frames total)")

    if after:
        print(f"\nCar IDs that only appeared AFTER ({len(after)}) - not needed to wake it:")
        for aid, t in sorted(after.items(), key=lambda kv: kv[1]):
            print(f"  t={t:7.3f}s  0x{aid:03X}")

    print("\n0x130 CAS terminal progression (the state walk to reproduce):")
    prev = None
    for t, direction, aid, data in rows:
        if direction != "car->eps" or aid != 0x130 or not data:
            continue
        if data[0] != prev:
            marker = "   <-- EPS wakes around here" if prev is not None and t >= wake > 0 and abs(t - wake) < 1.5 else ""
            print(f"  t={t:7.3f}s  b0=0x{data[0]:02X} {TERMINAL.get(data[0], '?'):15s}{marker}")
            prev = data[0]

    print("\nPayload variety in the pre-wake window (how much each ID actually moves):")
    seen_payloads = defaultdict(set)
    for t, direction, aid, data in rows:
        if direction == "car->eps" and t < wake:
            seen_payloads[aid].add(data)
    static = [aid for aid, s in seen_payloads.items() if len(s) == 1]
    varying = sorted(((len(s), aid) for aid, s in seen_payloads.items() if len(s) > 1), reverse=True)
    print(f"  {len(static)} IDs sent one fixed payload: " +
          ", ".join(f"0x{a:03X}" for a in sorted(static)))
    print("  IDs whose payload changed (these need live counters/values, not a frozen capture):")
    for n, aid in varying[:15]:
        print(f"    0x{aid:03X}: {n} distinct payloads")

    return 0


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