#!/bin/bash
# I, Ian Kelling, follow the GNU license recommendations at
# https://www.gnu.org/licenses/license-recommendations.en.html. They
# recommend that small programs, < 300 lines, be licensed under the
# Apache License 2.0. This file contains or is part of one or more small
# programs. If a small program grows beyond 300 lines, I plan to switch
# its license to GPL.

# Copyright 2024 Ian Kelling

# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at

#     http://www.apache.org/licenses/LICENSE-2.0

# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.



# requires 1.4.0 to run with multiple units due to bug before that:
# https://github.com/prometheus/node_exporter/pull/2475

set -eE -o pipefail
trap 'echo "$0:$LINENO:error: \"$BASH_COMMAND\" returned $?" >&2' ERR

if [[ ! $SERVICE_RESULT ]]; then
  echo "$0: error, no SERVICE_RESULT var."
  exit 1
fi

ser_name="$1"

if [[ ! $ser_name ]]; then
  echo "$0: error, no arg service name passed."
  exit 1
fi

dir=/var/lib/prometheus/node-exporter
if [[ ! -e $dir  ]]; then
  exit 0
fi

f=$dir/${ser_name}-result.prom
ftmp=$f.$$


write_count=false
if [[ -s $f ]]; then
  # https://www.freedesktop.org/software/systemd/man/systemd.exec.html
  if [[ $SERVICE_RESULT != success ]]; then
    write_count=true
    read -r _ count <$f
    case $count in
      ''|*[!0-9]*)
        count=0
        ;;
      *)
        count=$(( count + 1 ))
        ;;
    esac
  fi
else
  count=0
  write_count=true
fi

if $write_count; then
  printf 'node_systemd_unit_result_fail_count{name="%s"} %s\n' "$ser_name" "$count" >$ftmp
  mv $ftmp $f
fi