#!/bin/bash
# Version: 0.3.1
# Copyright (c) 2005-2022:
#   Darren 'Tadgy' Austin <darren (at) afterdark.org.uk>
# Licensed under the terms of the GNU General Public License version 3.

EXEC=""
ARGS=()
PIDFILE=""

# Allow configuration in /etc/default to override.
# Additional available variables:
#   ENVIRONMENT=()	# Extra environment passed to $EXEC.  Must be an array.
#   EXTRA_ARGS=()	# Extra arguments passed to $EXEC.  Must be an array.
#   SLAY_DELAY=""	# Delay between the SIGTERM and SIGKILL on a 'stop'.  Default: 2s.
#   RESTART_DELAY=""	# Delay between stopping and starting on a 'restart'.  Default: 2s.
# shellcheck disable=SC1090
[[ -e "/etc/default/${0##*rc.}" ]] && { source "/etc/default/${0##*rc.}" || return 1 2>/dev/null || exit 1; }

error() {
  printf "%s: %s: %s\\n" "${BASH_SOURCE[0]##*/}" "${EXEC##*/}" "$*" >&2
}

checkconfigured() {
  # This function can be used to perform any pre-start tests; hopfully to insure the daemon
  # can start correctly, before actually trying to start it.  A return value of 0 means the
  # tests were passed and the daemon should be started.  Any other value prevents the
  # daemon from being started, and an error message will be emitted.
  return 0
}

checkstatus() {
  # shellcheck disable=SC2155
  local RUNPIDS="$({ pgrep -f "$EXEC"; pgrep -F "$PIDFILE" 2>/dev/null; } | sort -u )"
  if [[ -n "$RUNPIDS" ]]; then
    printf "%s: %s: %s" "${BASH_SOURCE[0]##*/}" "${EXEC##*/}" "running"
    if [[ -n "$PIDFILE" ]]; then
      if [[ ! -e "$PIDFILE" ]]; then
        printf "%s" ", but .pid file does not exist"
      elif ! grep "\<$(<"$PIDFILE")\>" <<<"$RUNPIDS" >/dev/null 2>&1; then
        printf "%s" ", but .pid file is stale"
      fi
    fi
    printf "\\n"
  else
    printf "%s: %s: %s\\n" "${BASH_SOURCE[0]##*/}" "${EXEC##*/}" "stopped"
    return 1
  fi
  return 0
}

startdaemon() {
  if [[ ! -e "$EXEC" ]]; then
    error "not found"
    return 2
  elif [[ ! -x "$EXEC" ]]; then
    error "not executable"
    return 2
  elif ! checkconfigured; then
    error "not started - pre-start checks failed"
    return 2
  fi
  # shellcheck disable=SC2048,SC2086
  ${ENVIRONMENT:+declare ${ENVIRONMENT[*]};} "$EXEC" ${ARGS[*]} ${EXTRA_ARGS[*]}
  # shellcheck disable=SC2181
  if (( $? != 0 )); then
    error "error starting daemon"
    return 2
  else
    return 0
  fi
}

stopdaemon() {
  kill -TERM "$(pgrep -f "$EXEC" | tr $'\n' " ")" >/dev/null 2>&1
  [[ -e "$PIDFILE" ]] && {
    sleep 0.5
    kill -TERM "$(<"$PIDFILE")" >/dev/null 2>&1
  }
  sleep "${SLAY_DELAY:-2}"
  checkstatus >/dev/null && {
    error "failed to stop gracefully - slaying"
    kill -KILL "$({ cat "$PIDFILE"; pgrep -f "$EXEC"; } 2>/dev/null | sort -u | tr $'\n' " ")" >/dev/null 2>&1
  }
  return 0
}

case "$1" in
  'start')
    if checkstatus >/dev/null; then
      error "already running"
      printf "  %s\\n" "Try: ${BASH_SOURCE[0]} status" >&2
      RET=1
    else
      startdaemon
      RET=$?
    fi
    ;;
  'stop')
    if ! checkstatus >/dev/null; then
      error "not running"
      printf "  %s\\n" "Try: ${BASH_SOURCE[0]} status" >&2
      RET=1
    else
      stopdaemon
      RET=$?
    fi
    ;;
  'restart')
    checkstatus >/dev/null
    (( $? != 3 )) && {
      stopdaemon >/dev/null 2>&1
      sleep "${RESTART_DELAY:-2}"
    }
    startdaemon
    RET=$?
    ;;
  'status')
    checkstatus
    RET=$?
    ;;
  *)
    printf "%s\\n" "Usage: ${BASH_SOURCE[0]} <start|stop|restart|status>" >&2
    RET=1
    ;;
esac

return $RET 2>/dev/null || exit $RET