#!/usr/bin/env bash
# Clusev restart-sentinel watcher — runs on the HOST (never in a container).
#
# Watches for the restart sentinel file the dashboard writes (via a shared bind
# mount, see docker-compose.prod.yml: ./run -> storage/app/restart-signal) and,
# when it appears, restarts the prod stack, then deletes the sentinel.
#
# SECURITY: the panel container gets NO Docker socket. It only writes a marker
# file. This scoped host unit is the ONLY thing that talks to Docker — so a panel
# compromise cannot drive arbitrary `docker` commands.
#
# Two ways to run it:
#   1. systemd .path unit (preferred) — clusev-restart.path triggers
#      clusev-restart.service, which runs this script ONCE per sentinel.
#      Invoke as:  watch.sh once
#   2. Standalone poll/inotify loop (fallback, no systemd) — runs forever:
#      Invoke as:  watch.sh loop
#
# Config via env (with sane defaults):
#   CLUSEV_DIR      project dir holding docker-compose.prod.yml (default: script's repo root)
#   CLUSEV_SIGNAL   absolute path of the sentinel file (default: $CLUSEV_DIR/run/restart.request)
#   CLUSEV_POLL     poll interval seconds for the loop fallback (default: 5)
set -euo pipefail

# Resolve the repo root: docker/restart-sentinel/ -> ../../
SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
DEFAULT_DIR="$(cd "${SCRIPT_DIR}/../.." && pwd)"

CLUSEV_DIR="${CLUSEV_DIR:-$DEFAULT_DIR}"
CLUSEV_SIGNAL="${CLUSEV_SIGNAL:-${CLUSEV_DIR}/run/restart.request}"
CLUSEV_POLL="${CLUSEV_POLL:-5}"
COMPOSE_FILE="${CLUSEV_DIR}/docker-compose.prod.yml"

log() { printf '%s clusev-restart: %s\n' "$(date -Is)" "$*"; }

# Restart the stack and consume the sentinel. `up -d` (not bare `restart`) so a
# changed image/config is also applied and any down service is brought back.
do_restart() {
  [ -f "$COMPOSE_FILE" ] || { log "compose file not found: $COMPOSE_FILE — skipping"; return 1; }

  log "restart requested — applying (docker compose up -d) in ${CLUSEV_DIR}"
  if docker compose -f "$COMPOSE_FILE" up -d; then
    log "stack restarted"
  else
    log "docker compose up -d FAILED — leaving sentinel so it retries"
    return 1
  fi

  rm -f "$CLUSEV_SIGNAL" && log "sentinel cleared: $CLUSEV_SIGNAL"
}

# One shot: only act if the sentinel is actually present (the .path unit guarantees this,
# but a manual invocation might not).
run_once() {
  if [ -f "$CLUSEV_SIGNAL" ]; then
    do_restart
  else
    log "no sentinel at $CLUSEV_SIGNAL — nothing to do"
  fi
}

# Fallback loop for hosts without systemd: prefer inotifywait, else poll.
run_loop() {
  log "watching $CLUSEV_SIGNAL (loop mode)"
  if command -v inotifywait >/dev/null 2>&1; then
    # Act once on startup in case the sentinel already exists, then block on events.
    [ -f "$CLUSEV_SIGNAL" ] && do_restart || true
    while true; do
      # Watch the directory (the file is created/moved into it) for create/move events.
      inotifywait -q -e create -e moved_to -e close_write "$(dirname "$CLUSEV_SIGNAL")" >/dev/null 2>&1 || true
      [ -f "$CLUSEV_SIGNAL" ] && do_restart || true
    done
  else
    log "inotifywait not found — polling every ${CLUSEV_POLL}s"
    while true; do
      [ -f "$CLUSEV_SIGNAL" ] && do_restart || true
      sleep "$CLUSEV_POLL"
    done
  fi
}

case "${1:-once}" in
  once) run_once ;;
  loop) run_loop ;;
  *) log "usage: $0 [once|loop]"; exit 64 ;;
esac