#!/usr/bin/env bash
set -euo pipefail

camera_serial="${1:-}"
camera_label="${2:-camera}"
capture_width="${OMNI_CAMERA_DISCOVERY_WIDTH:-1280}"
capture_height="${OMNI_CAMERA_DISCOVERY_HEIGHT:-720}"
timeout_sec="${OMNI_CAMERA_DISCOVERY_TIMEOUT_SEC:-10}"

die() {
  echo "[camera-discovery] ${camera_label}: $*" >&2
  exit 1
}

[[ -n "${camera_serial}" ]] || die "camera serial is required"
[[ "${timeout_sec}" =~ ^[0-9]+$ ]] || die "OMNI_CAMERA_DISCOVERY_TIMEOUT_SEC must be a non-negative integer"

command -v udevadm >/dev/null 2>&1 || die "missing required command: udevadm"
command -v v4l2-ctl >/dev/null 2>&1 || die "missing required command: v4l2-ctl"

shopt -s nullglob
deadline=$((SECONDS + timeout_sec))

while true; do
  matches=()
  serial_nodes=()

  for device in /dev/video*; do
    [[ -c "${device}" ]] || continue
    device_serial="$(
      udevadm info --query=property --name="${device}" 2>/dev/null \
        | sed -n 's/^ID_SERIAL_SHORT=//p' \
        | head -1
    )"
    [[ "${device_serial}" == "${camera_serial}" ]] || continue
    serial_nodes+=("${device}")

    formats="$(v4l2-ctl -d "${device}" --list-formats-ext 2>/dev/null || true)"
    grep -q "'MJPG'" <<<"${formats}" || continue
    grep -q "Size: Discrete ${capture_width}x${capture_height}" <<<"${formats}" || continue
    matches+=("${device}")
  done

  if (( ${#matches[@]} == 1 )); then
    echo "[camera-discovery] ${camera_label}: serial=${camera_serial} -> ${matches[0]} (MJPG ${capture_width}x${capture_height})" >&2
    printf '%s\n' "${matches[0]}"
    exit 0
  fi
  if (( ${#matches[@]} > 1 )); then
    die "serial=${camera_serial} matched multiple MJPG nodes: ${matches[*]}"
  fi
  if (( SECONDS >= deadline )); then
    if (( ${#serial_nodes[@]} == 0 )); then
      die "serial=${camera_serial} was not found under /dev/video*"
    fi
    die "serial=${camera_serial} has no MJPG ${capture_width}x${capture_height} node; serial nodes: ${serial_nodes[*]}"
  fi
  sleep 0.2
done