#!/bin/bash

#< Template for writing your own nagios plugins
# accepts usage such as:
# plugin_name -c critical_threshold -w warning_threshold -v

# Executables
BASENAME="/usr/bin/basename"
ECHO="/bin/echo"
EGREP="/usr/bin/egrep"

# Variable initialistion
CRITICAL_FLAG="0"
WARNING_FLAG="0"
VERBOSE_FLAG="0"

THIS_PROG=$( ${BASENAME} $0 )

# Exit Status Codes
OK=0
WARNING=1
CRITICAL=2
UNKNOWN=3

function usage {
   ${ECHO} "Usage: ${THIS_PROG} -w  -c  [-v]" >&2
}

function print_error {
   ${ECHO} "Error: $@" >&2
}

function check_remaining_args {
   if [ "$1" -ne "0" ]; then
      (( VERBOSE_FLAG )) && {
         print_error "Remaining argument count not zero"
      }
      usage
      ${ECHO} "UNKNOWN: Extra arguments passed to plugin"
      exit ${UNKNOWN}
   fi
}

function parse_args {
   ERROR_COUNT=0
   if [ "${CRITICAL_FLAG}" -ne "1" ]; then
      (( VERBOSE_FLAG )) && {
         print_error "-c option not present"
      }
      (( ERROR_COUNT = ERROR_COUNT + 1 ))
   else
      # Let's check that the critical threshold contains a sane value
      ${ECHO} "${CRITICAL_THRESHOLD}" | ${EGREP} '^[0-9]+%?$' >/dev/null 2>&1
      if [ "$?" -ne "0" ]; then
         (( VERBOSE_FLAG )) && {
            print_error "Invalid critical threshold value passed"
         }
         (( ERROR_COUNT = ERROR_COUNT + 1 ))
      fi
      # This should never be true, a usage error would be thrown by the getopts while loop
      if [ -z "${CRITICAL_THRESHOLD}" ]; then
      (( VERBOSE_FLAG )) && {
         print_error "Critical threshold not set"
      }
      (( ERROR_COUNT = ERROR_COUNT + 1 ))
      fi
   fi

   if [ "${WARNING_FLAG}" -ne "1" ]; then
      (( VERBOSE_FLAG )) && {
         print_error "-w option not present"
      }
      (( ERROR_COUNT = ERROR_COUNT + 1 ))
   else
      # Let's check that the warning threshold contains a sane value
      ${ECHO} "${WARNING_THRESHOLD}" | ${EGREP} '^[0-9]+%?$' >/dev/null 2>&1
      if [ "$?" -ne "0" ]; then
         (( VERBOSE_FLAG )) && {
            print_error "Invalid warning threshold value passed"
         }
         (( ERROR_COUNT = ERROR_COUNT + 1 ))
      fi
      # This should never be true, a usage error would be thrown by the getopts while loop
      if [ -z "${WARNING_THRESHOLD}" ]; then
      (( VERBOSE_FLAG )) && {
         print_error "Warning threshold not set"
      }
      (( ERROR_COUNT = ERROR_COUNT + 1 ))
      fi
   fi
   if [ "${ERROR_COUNT}" -gt "0" ]; then
      (( VERBOSE_FLAG )) && {
         print_error "${ERROR_COUNT} error(s) found whilst parsing arguments"
      }
      ${ECHO} "UNKNOWN: Errors encountered passing plugin arguments"
      exit ${UNKNOWN}
   fi
}

# Nagios recommends multiple level verbosity (e.g. -vvv)
# but we will not bother with that
while getopts ":c:w:v" OPTION; do
  case ${OPTION} in
    "c")   if [ "${CRITICAL_FLAG}" -ne "0" ]; then
              (( VERBOSE_FLAG )) && {
                 print_error "More than one -c option specified"
              }
              ${ECHO} "UNKNOWN: More than one -c option passed to plugin"
              exit "${UNKNOWN}"
           fi
           CRITICAL_FLAG="1"
           CRITICAL_THRESHOLD="${OPTARG}"
           ;;
    "w")   if [ "${WARNING_FLAG}" -ne "0" ]; then
              (( VERBOSE_FLAG )) && {
                 print_error "More than one -w option specified"
              }
              ${ECHO} "UNKNOWN: More than one -w option passed to plugin"
              exit "${UNKNOWN}"
           fi
           WARNING_FLAG="1"
           WARNING_THRESHOLD="${OPTARG}"
           ;;
    "v")   VERBOSE_FLAG="1"
           ;;
     * )   usage
           exit ${UNKNOWN}
           ;;
  esac
done

# Even though we're not expecting extra args, let's be thorough
shift $(( ${OPTIND} - 1 ))

check_remaining_args "$#"
parse_args

exit ${OK}