#!/bin/bash

if [[ -z "$1" || -z "$2" ]] ; then
	echo "usage: $0 <volume> <density>" >&2
	exit 1
fi

timestamp () {
	t="`echo \"$1\" |sed -e 's/^.*@zb-//' |tr 'p_' '+ '`"
	date --date="$t" +%s
}

density="$2"
timenow=`date +%s`
lasttime=0

zfs list -t snapshot -r -d 1 -H "$1" |awk '{print $1;}' | while read l ; do
	echo `timestamp "$l"` "$l"
done |sort -n | while read l ; do
	curtime=${l%% *}
	snapname=${l#* }

	if [ "$curtime" -ge "$timenow" ] ; then
		break
	fi
	
	if [ `echo "$density*($curtime-$lasttime)/($timenow-$lasttime)"` -lt 1] ; then
		zfs destroy "$snapname"
	else
		lasttime="$curtime"
	fi
done