#!/usr/bin/env bash
set -o errexit
set -o nounset
set -o pipefail

LOG_FILE="/var/log/ailab-disk-watch.log"
threshold="${AILAB_DISK_THRESHOLD:-85}"

if ((EUID != 0)); then
  printf 'CRITICAL: this script must run as root to write %s\n' "$LOG_FILE" >&2
  exit 2
fi

if [[ ! "$threshold" =~ ^[0-9]+$ ]] || ((threshold < 1 || threshold > 100)); then
  printf 'CRITICAL: AILAB_DISK_THRESHOLD must be an integer from 1 to 100\n' >&2
  exit 2
fi

exec > >(tee -a "$LOG_FILE") 2>&1
printf '\n[%s] Disk usage check; threshold=%s%%\n' "$(date --iso-8601=seconds)" "$threshold"

status=0
while read -r filesystem _blocks _used available use_percent mountpoint; do
  usage="${use_percent%\%}"

  if [[ ! "$usage" =~ ^[0-9]+$ ]]; then
    printf 'WARNING: unable to parse usage for %s mounted on %s\n' "$filesystem" "$mountpoint"
    status=1
  elif ((usage >= threshold)); then
    printf 'WARNING: %s mounted on %s is %s used; threshold=%s%%; available=%s KB\n' \
      "$filesystem" "$mountpoint" "$use_percent" "$threshold" "$available"
    status=1
  else
    printf 'OK: %s mounted on %s is %s used\n' "$filesystem" "$mountpoint" "$use_percent"
  fi
done < <(df -P -x tmpfs -x devtmpfs | awk 'NR > 1 {print $1, $2, $3, $4, $5, $6}')

exit "$status"