#!/bin/bash

# Author: Carl Baldwin & Alan Pippin
# Description: This script takes a snapshot of the given zfs filesystem.
#              It also employs an intelligent algorithm to roll off,
#              or destroy, old snapshots.

# source our configuration
config="${0%/*}/zfs-scripts.conf"
[ -e "${config}.dist" ] && . ${config}.dist
[ -e "${config}" ] && . ${config}

if [[ -z "$SNAP_UNDER_TEST" ]]; then
    exec >> $logdir/zfs-autosnap.log 2>&1
fi

# This script makes the following assumptions/requirements:
#  * this script only handles one zfs filesystem, a wrapper should be created
#    to handle more
#  * this script handles all snapshots that are named in this format:
#    YYYY-MM-DD.hh.mm
#  * It ignores other snapshots that don't follow this naming convention

# This converts the YYYY-MM-DD.hh.mm format to an integer.
datetime_to_minutes() {
  perl -n -e '/(\d+)-(\d+)-(\d+)\.(\d+)\.(\d+)/; print $1 * 527040 + $2 * 44640 + $3 * 1440 + $4 * 60 + $5,"\n"'
}

# This converts date/time from YYYY-MM-DD.hh.mm to an integer that aligns
# things to prefer certain times such as the first of the month or midnight,
# etc
datetime_to_minutes2() {
  perl -n -e '/(\d+)-(\d+)-(\d+)\.(\d+)\.(\d+)/;
              $monthadj=int(($2-1)/3)-1; # Prefer months numbered 1,4,7 and 10
              $dayadj=$3 == 1 ? -1 : 0;  # Make sure day 1 is prefered
              $minadj=int($5/15);        # Prefer multiples of 15 minutes
              $houradj=int($4/3);        # Prefer midnight,noon,etc
              $intvalue=(
                1048576 *   $1
              + 65536   * ( $2 + $monthadj )
              + 2048    * ( $3 + $dayadj )
              + 64      * ( $4 + $houradj )
              +             $5 + $minadj
              );
              print $intvalue,"\n"'
}

# filesystem: This is the zfs filesystem to snapshot
# mountpoint: This is the mountpoint of the zfs filesystem to snapshot
# numsnapshots: This number is the number of equally spaced snapshots that should exist over any given period in the past
# maxagedays: This is the maximum number of days to keep any snapshot around for (0=infinite) (default=0).
filesystem=$1
mountpoint=${2-/$1}
numsnapshots=${3-12}
maxagedays=${4-0}
pool=`echo "$filesystem" | awk -F '/' '{ print $1 }'`

if [ -z "$filesystem" ] || [ -z "$mountpoint" ] || [ -z "$numsnapshots" ] || [ -z "$maxagedays" ]; then
   echo "-E- Usage: $0 <filesystem> <mountpoint> <numsnapshots> <maxagedays>"
   exit 1
fi

if [ -z "$SNAP_UNDER_TEST" -a ! -d "$mountpoint" ]; then
   echo "-E- Unable to find the mountpoint: $mountpoint"
   exit 1
fi

if [ -n "$SNAP_UNDER_TEST" ]; then
    snapshotdir="./snapshot"
else
    snapshotdir="${mountpoint}/.zfs/snapshot"
fi

if [ ! -d "$snapshotdir" ]; then
   echo "-E- Unable to find the snapshotdir: $snapshotdir"
   exit 1
fi

# Check to see if this zfs filesystem has a scrub being performed on it now.
# If it does, we cannot perform any snapshot create or destroy operations.
if [ -z "$SNAP_UNDER_TEST" ]; then
    zpool status $pool | grep scrub: | grep "in progress" > /dev/null 2>&1
    if [ $? == 0 ]; then
       echo "-W- The zfs pool '$pool' is currently being scrubbed. Skipping all snapshot operations."
       exit 0
    fi
fi

snapshot() {
    echo "-I- Creating $1"
    if [ -z "$SNAP_UNDER_TEST" ]; then
        zfs snapshot "$1"
    else
        mkdir -p snapshot/$(dirname "$(echo "$1" | sed 's,.*@,,')")
        touch snapshot/"$(echo "$1" | sed 's,.*@,,')"
    fi
}

destroy() {
    echo "-I- Destroying old $1"
    if [ -z "$SNAP_UNDER_TEST" ]; then
        zfs destroy "$1"
    else
        rm -f "$1"
    fi
}

# Get the various components of the date
datetime=${ZFSDATETIME:-$(date +%Y-%m-%d.%H.%M)}

# Create the snapshot for this minute
snapshot "${filesystem}@${datetime}"

minutes=$(echo $datetime | datetime_to_minutes)

if ! mkdir "$lockdir" >/dev/null 2>&1; then
  echo "-W- The zfs filesystem has been locked down. Skipping snapshot cleanup."
  exit 0
fi
cleanup() { rm -rf "$lockdir"; }
trap cleanup EXIT

# Trim them down
snapshots=$(ls -d ${snapshotdir}/????-??-??.??.?? 2>/dev/null)
for snapshot in $snapshots; do
  snapminutes=$(echo "$snapshot" | sed 's,.*/,,' | datetime_to_minutes)
  snapminutes2=$(echo "$snapshot" | sed 's,.*/,,' | datetime_to_minutes2)
  age=$((minutes - snapminutes))
  window=1
  while true; do
    if [ $age -lt $((window * numsnapshots)) ]; then
      case $((snapminutes2 % window)) in
        0) ;;
        *)
          snapname=${filesystem}$(echo "$snapshot" |
                                  sed 's,/\(.*\)/.zfs/snapshot/\(.*\),@\2,')
          destroy "$snapname"
        ;;
      esac
      break
    fi
    window=$((window*2))
  done
  if [ $maxagedays -gt 0 ] && [ $age -gt $((maxagedays * 24 * 60)) ]; then
    snapname=${filesystem}$(echo "$snapshot" |
                            sed 's,/\(.*\)/.zfs/snapshot/\(.*\),@\2,')
    destroy "$snapname"
  fi
done