#!/usr/bin/env bash
# Replay a recorded session's CAN frames through the decoder, so displays react as
# if the car were live. Runs on the car Orin (sudo: vcan and the decoder service).
#
#   usage: scripts/replay-session.sh SESSION_DIR [SKIP_S]
#     SESSION_DIR  e.g. /var/lib/yukart/recordings/000001-20261013T170050
#     SKIP_S       seconds of the recording to skip first (default 0)
#
# Frames go onto a virtual interface, vcan_replay, never can_pcan: the recorder only
# watches can_pcan, so a replay is never recorded as a drive. The decoder service is
# stopped for the replay (one MQTT client id) and a decoder runs on vcan_replay instead;
# however the replay ends (finished, Ctrl-C, killed), the service comes back and the
# interface goes. Values carry the replay's own timing; nothing marks them as replayed.
set -euo pipefail

SESSION="${1:?usage: replay-session.sh SESSION_DIR [SKIP_S]}"
SKIP="${2:-0}"
IF=vcan_replay
ls "$SESSION"/can-*.log* >/dev/null

cleanup() {
  [ -n "${DEC:-}" ] && kill "$DEC" 2>/dev/null || true
  sudo ip link del "$IF" 2>/dev/null || true
  sudo systemctl start yukart-decoder
  echo "replay: done; yukart-decoder back on can_pcan"
}
trap cleanup EXIT INT TERM

sudo modprobe vcan
sudo ip link add "$IF" type vcan 2>/dev/null || true
sudo ip link set "$IF" up
sudo systemctl stop yukart-decoder
/usr/local/bin/yukart-decoder --can "$IF" &
DEC=$!
sleep 1

echo "replay: $SESSION from +${SKIP} s onto $IF"
# candump -L lines: "(1791878450.945008) can_pcan 139#...". Skip by the first frame's time.
zstdcat -f "$SESSION"/can-*.log* 2>/dev/null \
  | awk -v skip="$SKIP" '{ t = substr($1, 2, length($1) - 2) + 0; if (NR == 1) t0 = t; if (t - t0 >= skip) print }' \
  | canplayer "$IF=can_pcan"