#!/usr/bin/env bash

set -euo pipefail

sizeWarn=''
sizeCrit=''
timeWarn=''
timeCrit=''
bucket=''
key=''

usage() {
  cat <<USAGE

$0: check objects size and time at Amazon S3

Usage:
  $0 [options]

Options:

  -f <path>            AWS CLI credentials file

  -b <bucket>          S3 bucket name, required
  -k <key>             object key, e. g. "hosts/foo/bar.gz"

  -s <spec in bytes>   object size warning threshold
  -S <spec in bytes>   object size critical threshold

  -t <spec in sec>     object age warning threshold
  -T <spec in sec>     object age critical threshold

Examples:

  $0 -b foobucket # check the bucket is available
  $0 -b foobucket -k hosts/foo/file.gz
  $0 -b foobucket -k hosts/foo/file.gz -t 86400
  $0 -b foobucket -k hosts/foo/file.gz -t 3600: -s 1000:

USAGE
}

die () {
  echo "$0: " "$@" >&2
  exit 1
}

while [ $# -gt 0 ]; do
  case "$1" in
    -f) export AWS_SHARED_CREDENTIALS_FILE="$2"; shift 2;;
    -b) bucket="$2"; shift 2;;
    -k) key="$2"; shift 2;;
    -s) sizeWarn="$2"; shift 2;;
    -S) sizeCrit="$2"; shift 2;;
    -t) timeWarn="$2"; shift 2;;
    -T) timeCrit="$2"; shift 2;;
    -h|--help) usage; exit 1;;
    *) die "unsupported argument: $1";;
  esac
done

inrange () {
  local r v
  local v1 v2
  local outter
  local sIFS

  r="$1"
  v="$2"

  case "$r" in
    @*) outter=true; r="${r/@/}";;
    *) outter=false;;
  esac

  sIFS=$IFS

  IFS=:
  set -- $r
  v1=${1-}
  v2=${2-}
  IFS=$sIFS

  case "$v1" in
    $r) v2=$v1; v1=0;;
    ~*)  v1=;;
  esac

  if $outter; then
    { [ -n "$v1" ] && [ "$v" -lt "$v1" ]; } || { [ -n "$v2" ] && [ "$v" -gt "$v2" ]; }
  else
    { [ -z "$v1" ] || [ "$v" -gt "$v1" ]; } && { [ -z "$v2" ] || [ "$v" -lt "$v2" ]; }
  fi
}

humanSize() {
  local n u

  n=$1
  for u in B KiB MiB GiB TiB; do
    if (( n > 1024 )); then
      (( n /= 1024 ))
    else
      break
    fi
  done

  echo "${n} ${u}"
}


[ -n "$bucket" ] || die "missing S3 bucket"

if [ -z "$key" ]; then
  if out=$(aws s3api head-bucket --bucket "$bucket" 2>&1); then
    echo "OK: bucket $bucket exists and is accessible"
    exit 0
  else
    printf 'CRITICAL: %s\n' "$(echo "$out" | grep .)"
    exit 2
  fi
fi

if ! out=$(aws s3api head-object --bucket "$bucket" --key "$key" 2>&1); then
  printf 'UNKNOWN: %s\n' "$(echo "$out" | grep .)"
  exit 3
fi

json=$out

size=$(echo "$json" | jq -r .ContentLength)
date=$(echo "$json" | jq -r .LastModified)

date_s=$(date -d "$date" +%s)
now_s=$(date -d now +%s)
age_s=$((now_s - date_s))
size_h=$(humanSize "$size")

stat="size=${size}B;${sizeWarn};${sizeCrit};0 age=${age_s}s;${timeWarn};${timeCrit}"

if [ -n "$timeCrit" ] && ! inrange "$timeCrit" "$age_s"; then
  echo "CRITICAL: last modified $date|$stat"
  exit 2
fi

if [ -n "$sizeCrit" ] && ! inrange "$sizeCrit" "$size"; then
  echo "CRITICAL: size $size_h|$stat"
  exit 2
fi

if [ -n "$timeWarn" ] && ! inrange "$timeWarn" "$age_s"; then
  echo "WARNING: last modified $date|$stat"
  exit 1
fi

if [ -n "$sizeWarn" ] && ! inrange "$sizeWarn" "$size"; then
  echo "WARNING: size $size_h|$stat"
  exit 1
fi

echo "OK: size $size_h, last modified $date|$stat"
exit 0