#!/usr/bin/env bash
# SPDX-License-Identifier: GPL-3.0-or-later

set -u

KIOSK_CONFIG_FILE="${KIOSK_CONFIG_FILE:-$HOME/.config/ha-kiosk/config}"
if [[ -r "$KIOSK_CONFIG_FILE" ]]; then
  # shellcheck source=/dev/null
  source "$KIOSK_CONFIG_FILE"
fi
: "${KIOSK_ID:=kiosk}"
: "${COMMAND_ROOT:=kiosk/commands}"
: "${STATUS_ROOT:=kiosk/status}"
AVAILABILITY_TOPIC="${STATUS_ROOT}/${KIOSK_ID}/availability"
PING_TOPIC="${COMMAND_ROOT}/${KIOSK_ID}/availability/ping"
PUBLISH_INTERVAL_SECONDS="${AVAILABILITY_INTERVAL_SECONDS:-30}"

publish_available() {
  /usr/bin/mosquitto_pub -r -t "$AVAILABILITY_TOPIC" -m "ON"
}

# Keep the MQTT connection that owns the Last Will open in the background.
/usr/bin/mosquitto_sub \
  -t "$PING_TOPIC" \
  --will-topic "$AVAILABILITY_TOPIC" \
  --will-payload "OFF" \
  --will-retain &
subscriber_pid=$!

cleanup() {
  kill "$subscriber_pid" 2>/dev/null || true
  wait "$subscriber_pid" 2>/dev/null || true
}
trap cleanup EXIT INT TERM

# Reassert retained availability after Mosquitto reconnects internally. The
# Last Will has already published OFF when a broker connection was lost.
while kill -0 "$subscriber_pid" 2>/dev/null; do
  publish_available || true
  sleep "$PUBLISH_INTERVAL_SECONDS"
done

wait "$subscriber_pid"