#!/bin/sh
set -e
svr=""
ssh_conf="ssh/config"
ssh_key="ssh/id_ed25519"
_backup_type="daily"
_suffix="tar.zst"
force=false


_date_for_type() {
case "$1" in
daily) date +%Y-%m-%d ;;
weekly) date +%Y-%U ;;
monthly) date +%Y-%m ;;
*) date +%s ;; # somehow, a bad type so just default to unix timestamp
esac
}

__help() {
cat <<EOF
$0 -svr <server> [opts]

Create a backup for <server>, defaults to daily. Calls <server>/backup.sh
on the remote host and saves the stdout. It's up to the server's
specific backup script to determine the specifics of that format. Tarballs
are suggested, but snapshots, cpio archives, etc can all be used.

Where [opts] are one of:

-ssh_conf <filename> # For ssh configuration i.e. -F flag on ssh
-ssh_key <filename>  # SSH key to use, passed in as -i to ssh
-type <daily|monthly|weekly> # Passed to the subscript, and changes output dir
-suffix <suffix> # Defaults to 'tar.zst', but could be anything, should match
                 # the output of the server's specific backup script
-force # Normally we bail if a backup exists, this will force overwrite

Normal usage is that weekly and monthly backups are full, and the daily
backups only include files that were changed in the past 24 hours, usually
via find command and piping a list of input files to tar.

A separate ./cleanup.sh script can take care of removing the old backups
on a schedule that you prefer.
EOF
exit 2
}

while [ $# -gt 0 ] ; do case $1 in
	-svr) svr="$2"; shift ; shift ;;
	-ssh_conf) ssh_conf="$2"; shift ; shift ;;
	-ssh_key) ssh_key="$2"; shift ; shift ;;
	-type) _backup_type="$2"; shift ; shift ;;
	-suffix) _suffix="$2"; shift ; shift ;;
	-force) force=true ; shift ;;
	*) __help ;; 
esac ; done

_err=0
if [ -z "$svr" ] ; then
	echo "-svr flag needs to be set"
	_err=1
fi
if [ -z "$ssh_conf" ] ; then
	echo "-ssh_conf flag needs to be set"
	_err=1
fi
if [ -z "$ssh_key" ] ; then
	echo "-ssh_key flag needs to be set"
	_err=1
fi

if ! [ -x "$svr/backup.sh" ] ; then
	echo "$svr/backup.sh should exist and be executable!"
	_err=1
fi

case "$_backup_type" in
	daily|weekly|monthly) true ;;
	*) echo "Bad backup type: '$_backup_type' valid options are daily, weekly, or monthly"; _err=1 ;;
esac

if [ "$_err" -ne 0 ] ; then
	exit "$_err"
fi

ssh -F "$ssh_conf" -i "$ssh_key" "$svr" "mkdir -p /root/.backup"
ssh -F "$ssh_conf" -i "$ssh_key" "$svr" "cat > /root/.backup/script.sh" < "$svr/backup.sh"
ssh -F "$ssh_conf" -i "$ssh_key" "$svr" "chmod +x /root/.backup/script.sh"


outfile="$svr/$_backup_type/$(_date_for_type "$_backup_type").$_suffix"
mkdir -p "$(dirname "$outfile")"
if [ -e "$outfile" ] ; then
	echo "BACKUP FILE EXISTS ALREADY: $outfile" 
	if $force ; then
		echo "OVERWRITING"
	else
		exit 1
	fi
fi
ssh -F "$ssh_conf" -i "$ssh_key" "$svr" "/root/.backup/script.sh \"$_backup_type\"" | pv > "$outfile"