#! /bin/sh

dir=
suffix=
retainweeks=3
dry_run=
verbose=:

help() {
  cat <<EOF
usage: $0 [OPTIONS] DIR
cleans up old backup files in DIR

OPTIONS are:
  -s, --suffix SUF        consider only file names ending in SUF
  -r, --retain N          retain N last weeks of backups (default $retainweeks)
  -v, --verbose           verbosely list what is being done
  -n, --dry-run           do nothing, print what would have been done
  -h, --help              print this help list

EOF
  exit 0
}

while [ $# -ne 0 ]
do
  case $1 in
  -s|--suffix) shift; suffix=$1;;
  -r|--retain) shift; retainweeks=$1;;
  -v|--verbose) verbose=echo;;
  -n|--dry-run) dry_run=echo; verbose=echo;;
  -h|--help) help;;
  --) shift; break;;
  -*) echo >&2 "$0: unrecognized option $1"
      exit 1;;
  *)  break
  esac
  shift
done

case $# in
0) echo >&2 "$0: not enough arguments"
   exit 1;;
1) dir=$1;;
*) echo >&2 "$0: too many arguments"
   exit 1;;
esac

thisweek=$(date +%U)
lastweek=$((thisweek - retainweeks))

$verbose \# removing files older than week $lastweek 

if [ -z "$suffix" ]; then
  find $dir -type f -printf '%f\n' 
else
  find $dir -type f -name "*$suffix" -printf '%f\n' 
fi | 
 while read name
 do 
   $verbose \# considering $name 
   week=$(expr "$name" : '[^-][^-]*-\([0-9][0-9]*\)-.*')
   if [ $week -le $lastweek ]; then
     $verbose \# removing $name
     $dry_run rm $dir/$name
   fi
 done