#!/usr/bin/env bash
# Grab one camera frame to a local JPEG.
# Usage: snap out.jpg
set -uo pipefail

[ $# -eq 1 ] || { echo "usage: snap out.jpg" >&2; exit 1; }
OUT="$1"

# The camera occasionally throws a transient I/O error or wedges; retry a
# few times with a hard timeout so a bad state can never hang the caller.
for attempt in 1 2 3; do
  if timeout 25 rpicam-still -n -t 800 --width 2592 --height 1944 -o /dev/shm/snap.jpg 2>/dev/null; then
    mv /dev/shm/snap.jpg "$OUT"
    echo "$OUT"
    exit 0
  fi
  sleep 3
done

# Camera busy (some process owns it) — fall back to the vilib MJPEG stream, if running.
: > /tmp/_stream.raw
curl -s --max-time 5 "http://localhost:9000/mjpg" -o /tmp/_stream.raw 2>/dev/null || true
if python3 - "$OUT" <<'PY'
import sys
d = open('/tmp/_stream.raw', 'rb').read()
i = d.find(b'\xff\xd8'); j = d.find(b'\xff\xd9', i)
if i < 0 or j <= i:
    sys.exit(1)
open(sys.argv[1], 'wb').write(d[i:j+2])
PY
then
  echo "$OUT"
else
  echo "ERROR: camera did not produce a frame after 3 attempts and no fallback stream" >&2
  exit 1
fi