#!/bin/bash

 # VCS Backup

 # Copyright © 2019 František Kučera (Frantovo.cz, GlobalCode.info)

 #

 # This program is free software: you can redistribute it and/or modify

 # it under the terms of the GNU General Public License as published by

 # the Free Software Foundation, either version 3 of the License, or

 # (at your option) any later version.

 #

 # 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, see <http://www.gnu.org/licenses/>.

 # Server-side configuration:

 VCS_BACKUP_DATA_DIR="/mnt/data";

 VCS_BACKUP_CURRENT_DIR="$VCS_BACKUP_DATA_DIR/current";

 VCS_BACKUP_CONFIG_DIR="$VCS_BACKUP_DATA_DIR/config";

 VCS_BACKUP_SNAPSHOT_DIR="$VCS_BACKUP_DATA_DIR/snapshot";

 VCS_BACKUP_SUBVOLUME_SOCKET="/run/vcs-backup-subvolume";

 VCS_BACKUP_CLONE_SOCKET="/run/vcs-backup-clone";

 VCS_BACKUP_USER="vcs-backup";

 VCS_BACKUP_MANAGER="vcs-backup-manager";

 # Installation – check and do it by hand:

 # There should be already mounted Btrfs at $VCS_BACKUP_DATA_DIR

 installInstructions() {

 cp vcs-backup.sh /usr/local/bin/

 adduser --disabled-password "$VCS_BACKUP"

 adduser --disabled-password "$VCS_BACKUP_MANAGER"

 mkdir "$VCS_BACKUP_CURRENT_DIR";

 mkdir "$VCS_BACKUP_CONFIG_DIR";

 mkdir "$VCS_BACKUP_SNAPSHOT_DIR";

 chown "${VCS_BACKUP_USER}:${VCS_BACKUP_USER}" "$VCS_BACKUP_CURRENT_DIR"

 chown "${VCS_BACKUP_MANAGER}:${VCS_BACKUP_MANAGER}" "$VCS_BACKUP_CONFIG_DIR"

 }

 # --- Private functions: ---------------------------------------------------------------------------

 # Environment: all

 # $1 = VCS type: hg, git

 # $2 = URL

 isValidTypeAndURL() { ([[ "$1" == "hg" || "$1" == "git" ]]) && [[ $(echo "$2" | wc -l) == 1 ]] && [[ $(echo "$2" | grep -E '^(http|https|ssh)://([a-zA-Z0-9_-][a-zA-Z0-9_-.]*/?)+$' | wc -l) == 1 ]]; }

 # Environment: all

 # $1 = path to the config file

 loadConfigFile() { if [ -f "$1" ]; then . "$1"; else echo "Missing config file: $1" >&2; exit 1; fi }

 # Environment: server

 # $1 = URL

 urlToRelativeDirectoryPath() {

 	echo "$1" | sed -E 's@^[^:]+://@@g';

 }

 # --- Public interface functions: ------------------------------------------------------------------

 # Environment: client

 # $1 = VCS type: hg, git

 # $2 = URL

 vcs_backup_public_clientSubmitBackupRequest() {

 	if isValidTypeAndURL "$1" "$2"; then

 		loadConfigFile ~/.config/vcs-backup/client.cfg

 		${VCS_BACKUP_SSH_COMMAND[@]} vcs-backup.sh serverSubmitBackupRequest "$1" "$2"

 	else

 		echo "Unsupported VCS type: '$1' or URL: '$2'" >&2;

 	fi

 }

 # Environment: server

 # $1 = VCS type: hg, git

 # $2 = URL

 vcs_backup_public_serverSubmitBackupRequest() {

 	if isValidTypeAndURL "$1" "$2"; then

 		loadConfigFile "/etc/vcs-backup/server.cfg";

 		relativePath=$1/$(urlToRelativeDirectoryPath "$2");

 		absolutePath="$VCS_BACKUP_CONFIG_DIR/$relativePath";

 		mkdir -p "$absolutePath";

 		echo "$1" > "$absolutePath/type.txt"

 		echo "$2" > "$absolutePath/url.txt"

 		echo "submited" > "$absolutePath/state.txt"

 		setfacl -m u:${VCS_BACKUP_USER}:r  "$absolutePath/type.txt"

 		setfacl -m u:${VCS_BACKUP_USER}:r  "$absolutePath/url.txt"

 		setfacl -m u:${VCS_BACKUP_USER}:rw "$absolutePath/state.txt"

 		echo "$relativePath" | socat -u - unix-send:${VCS_BACKUP_SUBVOLUME_SOCKET};

 	else

 		echo "Unsupported VCS type: '$1' or URL: '$2'" >&2;

 	fi

 }

 # Environment: server

 # Should be started as a systemd/init service.

 # - reads messages from from the subvolume socket – message contains the relative directory path

 # - creates a subvolume for given repository + necesary parent directories

 # - sends a message to the clone service → start cloning into the created subvolume

 vcs_backup_public_serverStartSubvolumeService() {

 	socat -u "unix-recv:${VCS_BACKUP_SUBVOLUME_SOCKET},group=${VCS_BACKUP_MANAGER},mode=770" - | while read d; do

 		mkdir -p $(dirname "$VCS_BACKUP_CURRENT_DIR/$d");

 		btrfs subvolume create "$VCS_BACKUP_CURRENT_DIR/$d" && \

 		echo "subvolumeCreated" > "$VCS_BACKUP_CONFIG_DIR/$d/state.txt" && \

 		chown "${VCS_BACKUP_USER}:${VCS_BACKUP_USER}" "$VCS_BACKUP_CURRENT_DIR/$d" && \

 		echo "$d" | socat -u - unix-send:${VCS_BACKUP_CLONE_SOCKET};

 	done

 }

 # Environment: server

 # should be started as a systemd/init service

 vcs_backup_public_serverStartCloneService() {

 	socat -u "unix-recv:${VCS_BACKUP_CLONE_SOCKET},mode=700" - | while read d; do

 		# FIXME: hg vs. git, clone

 		vcsType=$(cat "$VCS_BACKUP_CONFIG_DIR/$d/type.txt");

 		url=$(cat "$VCS_BACKUP_CONFIG_DIR/$d/url.txt");

 		if isValidTypeAndURL "$vcsType" "$url"; then

 			if   [[ "$vcsType" == "hg"  ]]; then  hg clone -U     "$url" "$VCS_BACKUP_CURRENT_DIR/$d";

 			elif [[ "$vcsType" == "git" ]]; then git clone --bare "$url" "$VCS_BACKUP_CURRENT_DIR/$d";

 			fi && echo "cloned" > "$VCS_BACKUP_CONFIG_DIR/$d/state.txt";

 		else

 			echo "Unsupported VCS type: '$vcsType' or URL: '$url'" >&2;

 		fi

 		# TODO: call-back to the client if client is waiting (socket exist in the config dir)

 	done

 }

 # --- Single entry-point: --------------------------------------------------------------------------

 PATH="/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin";

 PUBLIC_FUNCTION_PREFIX="vcs_backup_public_";

 if type -t "$PUBLIC_FUNCTION_PREFIX$1" > /dev/null; then

 	"$PUBLIC_FUNCTION_PREFIX${@:1}";

 else

 	echo "Unsupported sub-command: $1" >&2

 	echo "Available sub-commands:" >&2

 	declare -F | grep "$PUBLIC_FUNCTION_PREFIX" | sed "s/.*$PUBLIC_FUNCTION_PREFIX/  /g" >&2

 	exit 1;

 fi