#!/bin/bash
# chkconfig: 2345 95 05
# description: Linux Sensor
### BEGIN INIT INFO
# Provides:          linux-sensor
# Required-Start:    $network $remote_fs
# Required-Stop:     $network $remote_fs
# Default-Start:     2 3 4 5
# Default-Stop:      0 1 6
# Short-Description: Linux Sensor
### END INIT INFO

DAEMON=/usr/local/bin/linux-sensor
PIDFILE=/var/run/linux-sensor.pid
LOGFILE=/var/log/linux-sensor.log

resolve_pid() {
  if command -v pgrep >/dev/null 2>&1; then
    pgrep -f "^$DAEMON run" | head -1
  else
    for p in /proc/[0-9]*; do
      [ -r "$p/cmdline" ] || continue
      if head -c 4096 "$p/cmdline" 2>/dev/null | tr -d '\0' | grep -q "^$DAEMON run"; then
        basename "$p"; break
      fi
    done
  fi
}

start() {
  P=$(resolve_pid)
  if [ -n "$P" ]; then
    echo "linux-sensor already running (pid $P)"
    echo "$P" > "$PIDFILE"
    return 0
  fi
  echo -n "Starting linux-sensor: "
  ( nohup setsid "$DAEMON" run >>"$LOGFILE" 2>&1 < /dev/null & ) >/dev/null 2>&1
  sleep 1
  P=$(resolve_pid)
  if [ -n "$P" ]; then
    echo "$P" > "$PIDFILE"
    echo "OK (pid $P)"
  else
    echo "FAILED (see $LOGFILE)"
    return 1
  fi
}

stop() {
  echo -n "Stopping linux-sensor: "
  # Don't trust just the pidfile — it can be stale or wrong (pgrep is
  # camouflage-proof: cmdline is unchanged, only /proc/N/comm is).
  P=$(resolve_pid)
  if [ -z "$P" ] && [ -f "$PIDFILE" ]; then
    P=$(cat "$PIDFILE" 2>/dev/null)
    if [ -n "$P" ] && ! [ -r "/proc/$P/cmdline" ]; then P=""; fi
  fi
  if [ -n "$P" ]; then
    kill "$P" 2>/dev/null
    # WAIT for the process to actually die. Without this, a fast `restart`
    # races: the agent has SIGTERM handlers that take a moment to drain
    # goroutines, so `sleep 1; start` would find the still-living agent,
    # say "already running", and never spawn a new one. Then the old one
    # finishes dying and nothing is left. Wait up to 15s, SIGKILL on timeout.
    i=0
    while [ -d "/proc/$P" ] && [ $i -lt 15 ]; do
      sleep 1
      i=$((i + 1))
    done
    [ -d "/proc/$P" ] && kill -9 "$P" 2>/dev/null
  fi
  rm -f "$PIDFILE"
  echo "OK"
}

status() {
  P=$(resolve_pid)
  if [ -n "$P" ]; then
    echo "linux-sensor is running (pid $P)"
    return 0
  fi
  echo "linux-sensor is not running"
  return 3
}

case "$1" in
  start)   start;;
  stop)    stop;;
  restart) stop; sleep 1; start;;
  status)  status;;
  *) echo "Usage: $0 {start|stop|restart|status}"; exit 2;;
esac