#!/bin/bash

# format: db-dumps-YYYY-MM-DD.sql.gz
BACKUPS="/home/backups/db-dump-*"

DAILY_COUNT="14"
WEEKLY_COUNT="8"
MONTHLY_COUNT="12"

# -----

TODAY=$(date +%Y%m%d)
TODAY_WEEKDAY=$(date +%w)


TEMPFILE=$(mktemp)

# create list
for offset in `seq 0 $DAILY_COUNT`; do
    tmp=$(date +%Y-%m-%d -d "-$offset days")
    echo $tmp >> $TEMPFILE
done

for offset in `seq 0 $WEEKLY_COUNT`; do
    calc=$[$offset * 7]
    calc=$[$calc + $TODAY_WEEKDAY]

    tmp=$(date +%Y-%m-%d -d "-$calc days")
    echo $tmp >> $TEMPFILE
done

for offset in `seq 0 $MONTHLY_COUNT`; do
    calc=$[$offset * 28]
    calc=$[$calc + $TODAY_WEEKDAY]

    tmp=$(date +%Y-%m-%d -d "-$calc days")
    echo $tmp >> $TEMPFILE
done

# remove files not on the list
ls -1 ${BACKUPS} | while read filename; do
    filedate=$(echo $filename | awk -F'-' '{print $3-$4-$5}')

    grep $filedate $TEMPFILE &> /dev/null || rm $filename
done

rm $TEMPFILE