#!/bin/bash
#
# This is a simple backup script using duplicity. It's supposed to serve as a
# starting point and to be adjusted to your system.
#
# Important steps:
#  - define a host "backup" in root's .ssh/config
#  - read the script and adjust to your needs
#  - export BORG_REPO in your environment or create a wrapper in $PATH that
#    does it for calls to borg (my preference). For details on the variable
#    see man borg

set -e

main() {
	if [[ $UID != 0 ]]; then
		exec sudo "$0" "$@"
	fi

	TMPDIR="$(mktemp -d "/tmp/${0##*/}.XXXXXX")"
	trap "rm -rf '${TMPDIR}'" EXIT TERM

	# if you want to encrypt the backups remove --no-encryption in the duplicity call
	# and uncomment the lines that contain PASSPHRASE
	#PASSPHRASE="randomstringhere"

	# these mountpoints will be excluded
	excludeMountpoints=(
	/tmp
	/sys
	/dev
	/proc
	/run
	/mnt/levant/nfs
	/media
	)

	# these mountpoints will be included
	includeMountpoints=(
	/
	/boot
	/home
	/mnt/data
	)

	# first line that matches wins
	IFS='' read -r -d '' excludeList <<EOF || true
+ /home/flo/.local/share/Steam/steamapps/common/Counter-Strike Global Offensive/csgo/cfg
- /home/*/.local/share/Steam/steamapps/common/*/*
- /home/*/.cache/*
- /home/*/.claws-mail/imapcache
- /root/.cache/*
- /var/cache/pacman/pkg/*
EOF

	# same as above, but for borg backup. Note that borg uses a different
	# syntax and does not support including lower level directories
	# (TODO: verify this claim)
	IFS='' read -r -d '' excludeList_borg <<EOF || true
sh:/home/flo/tmp/*
sh:/home/*/.cache/*
sh:/root/.cache/*
sh:/var/cache/pacman/pkg/*
EOF

	exclude_mountpoints
	echo "$excludeList" > "$TMPDIR/exclude-list"
	echo "$excludeList_borg" > "$TMPDIR/exclude-list-borg"

	# save some data that's useful for restores
	local backupDataDir=/root/backup-data/
	mkdir -p "$backupDataDir"
	fdisk -l > "$backupDataDir/fdisk"
	vgdisplay > "$backupDataDir/vgdisplay"
	pvdisplay > "$backupDataDir/pvdisplay"
	lvdisplay > "$backupDataDir/lvdisplay"
	lvdisplay > "$backupDataDir/lvdisplay"
	df -a > "$backupDataDir/df"
	findmnt -l > "$backupDataDir/findmnt"

	backup_borg /

	#local backupdir="$HOSTNAME-backup/full-backup"
	#backup_duplicity / "sftp://backup/$backupdir/" --exclude-filelist "$TMPDIR/exclude-list"
	#ssh backup "touch $backupdir/last-backup-timestamp"
}

backup_duplicity() {
	local src=$1
	local dest=$2
	shift 2
	local -a options=()

	if [[ $(date +%d ) == '1' ]]; then
		# try to only run full backups on day 1 each month
		options+=(--full-if-older-than 2D)
	else
		# force a full backup once in a while
		options+=(--full-if-older-than 30D)
	fi

	#export PASSPHRASE
	HOME=/root duplicity \
		-v5 \
		--numeric-owner \
		--volsize 250 \
		--allow-source-mismatch \
		--asynchronous-upload \
		--no-encryption \
		"${options[@]}" "$@" "$src" "$dest"

	HOME=/root duplicity --force remove-older-than 120D "$dest"
	#export PASSPHRASE=""
}

backup_borg() {
	local src=$1

	borg create \
		-v \
		--numeric-owner \
		--compression lz4 \
		--stats \
		--progress \
		--exclude-from "$TMPDIR/exclude-list-borg" \
		"::backup-$(date "+%Y%m%d-%H%M%S")" "$src"

	borg prune -v --keep-within 3m
}

### support functions below ###

##
#  usage : in_array( $needle, $haystack )
# return : 0 - found
#          1 - not found
##
in_array() {
    local needle=$1; shift
    local item
    for item in "$@"; do
        [[ $item = "$needle" ]] && return 0 # Found
    done
    return 1 # Not Found
}

# same as in_array except 0 is returned if any item in haystack starts with needle
in_array_startswith() {
    local needle=$1; shift
    local item
    for item in "$@"; do
        [[ "$needle" == "$item"* ]] && return 0 # Found
    done
    return 1 # Not Found
}

exclude_mountpoints() {
	local error=0

	for fs in "${excludeMountpoints[@]}"; do
		excludeList+="- $fs/*"$'\n'
		excludeList_borg+="sh:$fs/*"$'\n'
	done

	while read line; do
		local mountpoint=$(echo "$line" | cut -d\  -f2 | sed 's#\040# #g;')

		if ! in_array $mountpoint "${includeMountpoints[@]}"; then
			if ! in_array_startswith "$mountpoint/" "${excludeMountpoints[@]/%//}"; then
				error=1
				echo "Warning: mountpoint not excluded or included: $mountpoint" >&2
			fi
		fi
	done </etc/mtab

	if ((error)); then
		exit 1
	fi
}

main "$@"