#!/bin/bash

# remove-old-backups version #VERSION#

[ -r "#ETCDIR#/backup.conf" ] && \
  . "#ETCDIR#/backup.conf"

usage () {
  >&2 echo \
'Usage: remove-old-backups [-n]
Remove backups older than one year, keeping only one backup per month.

Options:
#HELPTEXT#  #
  -n         only print what would be removed'
  [ -n "$1" ] && exit $1
  exit 1
}

no_action=false

if [ $# -eq 1 ]
then
  if [ "x$1" == 'x--help' ]
  then
    usage 0
  elif [ "x$1" == 'x--version' ]
  then
    >&2 echo '#VERSION#'
    exit 0
  elif [ "x$1" == 'x-n' ]
  then
    no_action=true
  else
    usage
  fi
elif [ $# -gt 1 ]
then
  usage
fi

backups=$(
  printf '%s\n' "${backups[@]}" | \
    cut -d' ' -f1 | \
    while read -r dir; do \
      if [ $(ls "$dir" | wc -l) -lt 30 ]; then
        continue;
      fi
      ls -1 "$dir" | \
        sed -n '
          s,^\([0-9]\{4\}\)_\([0-9]\{2\}\)_\([0-9]\{2\}\)$,'"${dir}"'\0 \3 \2 \1 '"${dir}"',
          T
          p
        '
    done
)

{
  printf '%s\n' "${backups}" | \
    sort -k5,5 -k4,4 -k3,3 -k2,2 -k1,1 | \
    uniq -f2
  printf '%s\n' "${backups}" | \
    sed "$(
      for dist in $(seq 0 20 180); do
        printf '/ %s \S\+$/p\n' \
          "$(date '+%m %Y' -d@$(($(date +%s)-24*60*60*${dist})))"
      done | \
        sort -u
    )"
} | \
  cut -d' ' -f1 | \
  sort | \
  uniq -u | \
  while read -r dir; do
    echo rm -rf --one-file-system "${dir}"
    if ! ${no_action}; then
      rm -rf --one-file-system "${dir}"
    fi
  done