#!/bin/bash
#
# backup-keybase-dated
# John Simpson <jms1@jms1.net> 2018-04-25
# Last update: 2018-08-13
#
# Backs up the current user's /keybase directory to a dated directory,
# using the most recent dated directory as a base.
#
# This script should be installed in the directory which will be the "parent"
# of the dated backups.
#
###############################################################################
#
# Copyright (C) 2018 John Simpson.
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License, version 2 or 3,
# as published by the Free Software Foundation.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program; if not, write to the Free Software
# Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
# or visit http://www.gnu.org/licenses/gpl.txt
#
###############################################################################

PATH="/usr/bin:/bin:/usr/local/bin"
BAKDIR="$( dirname "$( realpath "$0" )" )"
SHOW="-q"
ROTATE=""

usage() {
    MSG="${1:-}"

    cat <<EOF
$0 [-r ___] [-q] [-v]

Uses rsync to make a "dated" backup of the current user's /keybase/ filesystem.
Any files which have not been changed since the previous backup are stored as
hard links in order to save disk space.

The dated backup images are stored under $BAKDIR

-r ___  Rotate the backup directories. The value specifies how many previous
        directories to save. If not specified, no rotation will be done, and
        any old directories will need to be cleaned up manually.

-q      Quiet. Sent to the 'rsync' command.

-v      Verbose. Sent to the 'rsync' command.

The 'rsync' command which does the copy will have EITHER '-q' or '-v' added to
it (but not both), depending on which option appears latest on this script's
command line. If neither option is present, '$SHOW' will be used by default.

EOF

    if [[ -n "$MSG" ]]
    then
        echo $MSG
        exit 1
    fi

    exit 0
}

###############################################################################
###############################################################################
###############################################################################

if [[ -z "$BAKDIR" ]]
then
    echo "ERROR: unable to set BAKDIR, cannot continue"
    exit 1
fi

if [[ ( "$BAKDIR" =~ ^/keybase/ )           \
   || ( "$BAKDIR" =~ ^/Volumes/Keybase/ )   \
   || ( "$BAKDIR" =~ ^/Volumes/Keybase\  )  ]]
then
    echo "ERROR: BAKDIR cannot be stored within Keybase"
    exit 1
fi

while getopts ":r:qvh" OPT
do
    case $OPT in
        r)  ROTATE=$OPTARG
            ;;
        q)  SHOW="-q"
            ;;
        v)  SHOW="-v"
            ;;
        h)  usage
            ;;
        ?)  usage "ERROR: unknown option \"$OPTARG\""
            ;;
    esac
done

shift $((OPTIND-1))

########################################

if [[ ! -d /keybase/private ]]
then
    echo "ERROR: /keybase/private is not a directory"
    exit 1
fi

if [[ ! -d "$BAKDIR" ]]
then
    echo "ERROR: $BAKDIR is not a directory"
    exit 1
fi

########################################
# Figure out if we have a "previous" backup to link from
# If not, the script will do a "first" backup.

if [[ -e "$BAKDIR/.good" ]]
then
    PREVDIR="$BAKDIR/.good"
else
    PREV=$( ls -1tr "$BAKDIR" | grep ^2 | tail -1 )
    if [[ -n "${PREV:-}" ]]
    then
        PREVDIR="$BAKDIR/$PREV"
    else
        PREVDIR=""
    fi
fi

if [[ -n "$PREVDIR" ]]
then
    LINKPREV="--link-dest=$PREVDIR"
else
    LINKPREV=""
fi

########################################
# Set up the directory for "this" backup

NOW=$( date -u +%Y-%m-%dT%H:%M:%S+00 )
THISDIR="$BAKDIR/$NOW"
if [[ -e "$THISDIR" ]]
then
    echo "ERROR: $THISDIR already exists"
    exit 1
fi

mkdir -m 0755 "$THISDIR" || exit 1

########################################
# Do the deed

if [[ -n "$LINKPREV" ]]
then
    echo "===== Previous backup: $PREVDIR ====="
else
    echo "===== No previous backup ====="
fi

echo "===== Starting backup: $THISDIR ====="

SRC="/keybase"

OTHER="-L -O --chmod=u+w,go="

set -x
rsync -az $SHOW $LINKPREV $OTHER "$SRC/" "$THISDIR/"
set +x

rv=$?

echo "===== Backup finished, rv=$rv ====="

########################################
# If the backup was successful,
# or if the only failure was due to source files disappearing,
# - mark it as "ok"
# - change the ".good" link
# - delete old backup images

OK=false
if [[ "$rv" =  "0" ]] ; then OK=true ; fi
if [[ "$rv" = "24" ]] ; then OK=true ; fi

if $OK
then
    ########################################
    # Mark the directory as OK
    # Change the ".good" link

    echo "===== Marking $NOW as OK ====="
    mv "$THISDIR" "$THISDIR.ok"

    echo "===== Pointing \".good\" to \"$NOW.ok\" ====="
    rm -f "$BAKDIR/.good"
    ln -s "$NOW.ok" "$BAKDIR/.good"

    ########################################
    # Possibly delete old backup images

    DEL=""
    if [[ -n "$ROTATE" ]]
    then
        DEL=$( ls -1r "$BAKDIR" | sed "1,${ROTATE}d" )
    fi

    if [[ -n "$DEL" ]]
    then
        echo "===== Removing old backup directories ====="

        DIRS=""
        for DIR in $DEL
        do
            echo "$BAKDIR/$DIR"
            DIRS="$DIRS $BAKDIR/$DIR "
        done

        time rm -rf $DIRS
    elif [[ -n "$ROTATE" ]]
    then
        echo "===== Not more than ${ROTATE} old backup directories to delete ====="
    fi
    exit 0
else
    echo "WARNING: bypassing rotation because rsync failed"
    exit 1
fi