#!/usr/bin/env bash

# called before backup
borgwrapper_pre_backup() {
	return;
}

# called after backup
borgwrapper_post_backup() {
	return;
}

# usage
usage() {
USAGE=$(cat <<EOF
Usage: borgwrapper [CONFIG_FILE (absolute path)]

A script which wraps the most common use case for borg: creating a backup and sending a notification.

If no CONFIG_FILE is given, \$HOME/.borgwrapper.conf is used. This fallback option
has to exist if no other CONFIG_FILE exists. Otherwise the script exits.

Configuration can be done in any file and any pre-defined variable can be overwritten.

The following are at least required for the script to work:
- BORGWRAPPER_BACKUP_NAME // [a-z09], should be unique for multiple backups (with the same remote user)
- BORGWRAPPER_BACKUP_FILES // an array of files and directories to backup, e.g. =('/home', '/root')
- BORGWRAPPER_BACKUP_REPOSITORY // trailing slash, add "user@host:/dir/" if remote

The following are optional or have reasonable defaults:
- BORGWRAPPER_BACKUP_PASSWORD='' // the password if needed
- BORGWRAPPER_BACKUP_TIMESTAMP_FORMAT=$(date "+%s")
- BORGWRAPPER_BACKUP_PRUNE=true // prune the repository (cleans old backups; uses \$BORGWRAPPER_BACKUP_KEEP_IN_DAYS)? false|true
- BORGWRAPPER_BACKUP_KEEP_IN_DAYS=60 // in days, integer only (used for prune)
- BORGWRAPPER_BACKUP_CHECK=true // checks entire repository, this is slow! false|true
- BORGWRAPPER_BACKUP_CHECK_MAX_AGE_IN_SECONDS=604800 // determine when "borg check" has to run by comparing current time with latest run check (determined by last mod time of \$BORGWRAPPER_BACKUP_CHECK_FILE). default is 7 days, 0 will always run the check
- BORGWRAPPER_BACKUP_CHECK_FILE="~/.borgwrapper-\$BORGWRAPPER_BACKUP_NAME.check" // used for time comparison
- BORGWRAPPER_BACKUP_LOG=true // log? false|true
- BORGWRAPPER_BACKUP_LOG_PRUNE=true // overwrite old log for each execution? false|true
- BORGWRAPPER_BACKUP_LOG_FILE="~/.borgwrapper-\$BORGWRAPPER_BACKUP_NAME.log" // log file to save output to to
- BORGWRAPPER_BACKUP_NOTIFY_VIA_MAIL=false // send email (\$BORGWRAPPER_BACKUP_LOG has to be set to true)? false|true
- BORGWRAPPER_BACKUP_NOTIFY_MAIL_ADDRESS="" // mail.rc has to be configured
- BORGWRAPPER_BACKUP_NOTIFY_UI=false // use notify-send for UI notification? false|true
- BORGWRAPPER_BACKUP_COMPRESSION="lz4" // compress repository
- BORGWRAPPER_BACKUP_ENCRYPTION="none" // encrypt repository

Borg specific values can also be overwritten and have reasonable defaults:
- BORG_BINARY=borg; // defaults to /usr/bin/borg (determined by 'which borg'), adjust to a virtualenv if needed
- BORGWRAPPER_BORG_INIT_PARAMS="init --encryption=\$BORGWRAPPER_BACKUP_ENCRYPTION"; // encryption=none|repokey-blake2|...
- BORGWRAPPER_BORG_CREATE_PARAMS="create -v -s -p -C \$BORGWRAPPER_BACKUP_COMPRESSION";
- BORGWRAPPER_BORG_CHECK_PARAMS="check -v";
- BORGWRAPPER_BORG_PRUNE_PARAMS="prune -v -s -d \$BORGWRAPPER_BACKUP_KEEP_IN_DAYS";
- BORGWRAPPER_BORG_LIST_PARAMS="list -v";
- BORGWRAPPER_BORG_INFO_PARAMS="info";

More information can be found in the docs: https://borgbackup.readthedocs.io

The following functions are executed before and after the backup and can also be overwritten in the config file by redefining them:
- borgwrapper_pre_backup
- borgwrapper_post_backup

You can copy this script to '/usr/local/bin' and use create a custom CONFIG_FILE as user. Examples can be found in '/usr/share/doc/<scriptname>'.
EOF
)
	echo "$USAGE";
}

set -e;

# helper functions
source_config() {
    local config=$1;
    local configFallback=$2;

    if [[ ! -f "$config" ]]; then
        if [[ ! -f "$configFallback" ]]; then
            echo "No config file specified and could not find default in '${configFallback}'!";
            echo "";
            usage;
            exit 1;
        else
            config=${configFallback};
        fi
    fi

    set -a;
    source "${config}";
    set +a;
}
apply_defaults() {
    [[ -z ${BORGWRAPPER_BACKUP_PASSWORD} ]] && BORGWRAPPER_BACKUP_PASSWORD='';
    [[ -z ${BORGWRAPPER_BACKUP_TIMESTAMP_FORMAT} ]] && BORGWRAPPER_BACKUP_TIMESTAMP_FORMAT=$(date "+%s");
    [[ -z ${BORGWRAPPER_BACKUP_PRUNE} ]] && BORGWRAPPER_BACKUP_PRUNE=true;
    [[ -z ${BORGWRAPPER_BACKUP_KEEP_IN_DAYS} ]] && BORGWRAPPER_BACKUP_KEEP_IN_DAYS=60;
    [[ -z ${BORGWRAPPER_BACKUP_CHECK} ]] && BORGWRAPPER_BACKUP_CHECK=true;
    [[ -z ${BORGWRAPPER_BACKUP_CHECK_MAX_AGE_IN_SECONDS} ]] && BORGWRAPPER_BACKUP_CHECK_MAX_AGE_IN_SECONDS=604800;
    [[ -z ${BORGWRAPPER_BACKUP_CHECK_FILE} ]] && BORGWRAPPER_BACKUP_CHECK_FILE="$HOME/.borgwrapper-${BORGWRAPPER_BACKUP_NAME}.check";
    [[ -z ${BORGWRAPPER_BACKUP_LOG} ]] && BORGWRAPPER_BACKUP_LOG=true;
    [[ -z ${BORGWRAPPER_BACKUP_LOG_PRUNE} ]] && BORGWRAPPER_BACKUP_LOG_PRUNE=true;
    [[ -z ${BORGWRAPPER_BACKUP_LOG_FILE} ]] && BORGWRAPPER_BACKUP_LOG_FILE="$HOME/.borgwrapper-${BORGWRAPPER_BACKUP_NAME}.log";
    [[ -z ${BORGWRAPPER_BACKUP_NOTIFY_VIA_MAIL} ]] && BORGWRAPPER_BACKUP_NOTIFY_VIA_MAIL=false;
    [[ -z ${BORGWRAPPER_BACKUP_NOTIFY_MAIL_ADDRESS} ]] && BORGWRAPPER_BACKUP_NOTIFY_MAIL_ADDRESS="";
    [[ -z ${BORGWRAPPER_BACKUP_NOTIFY_UI} ]] && BORGWRAPPER_BACKUP_NOTIFY_UI=false;
    [[ -z ${BORGWRAPPER_BACKUP_COMPRESSION} ]] && BORGWRAPPER_BACKUP_COMPRESSION=none;
    [[ -z ${BORGWRAPPER_BACKUP_ENCRYPTION} ]] && BORGWRAPPER_BACKUP_ENCRYPTION=none;
    [[ -z ${BORG_BINARY} ]] && BORG_BINARY=$(which borg);
    [[ -z ${BORGWRAPPER_BORG_INIT_PARAMS} ]] && BORGWRAPPER_BORG_INIT_PARAMS="init --encryption=${BORGWRAPPER_BACKUP_ENCRYPTION}";
    [[ -z ${BORGWRAPPER_BORG_CREATE_PARAMS} ]] && BORGWRAPPER_BORG_CREATE_PARAMS="create -v -s -p -C ${BORGWRAPPER_BACKUP_COMPRESSION}";
    [[ -z ${BORGWRAPPER_BORG_CHECK_PARAMS} ]] && BORGWRAPPER_BORG_CHECK_PARAMS="check -v";
    [[ -z ${BORGWRAPPER_BORG_PRUNE_PARAMS} ]] && BORGWRAPPER_BORG_PRUNE_PARAMS="prune -v -s -d ${BORGWRAPPER_BACKUP_KEEP_IN_DAYS}";
	[[ -z ${BORGWRAPPER_BORG_LIST_PARAMS} ]] && BORGWRAPPER_BORG_LIST_PARAMS="list -v";
	[[ -z ${BORGWRAPPER_BORG_INFO_PARAMS} ]] && BORGWRAPPER_BORG_INFO_PARAMS="info";
}
check_required() {
    if [[ -z ${BORGWRAPPER_BACKUP_REPOSITORY} ]]; then
    	echo "BORGWRAPPER_BACKUP_REPOSITORY is required"
        exit 1;
    fi
    if [[ -z ${BORGWRAPPER_BACKUP_NAME} ]]; then
    	echo "BORGWRAPPER_BACKUP_NAME is required"
        exit 1;
    fi
    type ${BORG_BINARY} >/dev/null 2>&1 || { echo >&2 "Require '${BORG_BINARY}' (binary) but it's not installed. Aborting."; exit 1; }
}

# define wrapper functions
backup() {
	echo "Using ${BORG_BINARY} as binary";
	borgwrapper_pre_backup;

	if [ ! -z "${BORGWRAPPER_BACKUP_PASSWORD}" ]; then
	    export BORG_PASSPHRASE=${BORGWRAPPER_BACKUP_PASSWORD};
	fi

	# init hint
	echo "Hint: If you haven't, you need to create the borg repository manually before first run if it doesn't exist:";
	echo "${BORG_BINARY} ${BORGWRAPPER_BORG_INIT_PARAMS} ${BORGWRAPPER_BACKUP_REPOSITORY}${BORGWRAPPER_BACKUP_NAME}";

	# create
	${BORG_BINARY} ${BORGWRAPPER_BORG_CREATE_PARAMS} ${BORGWRAPPER_BACKUP_REPOSITORY}${BORGWRAPPER_BACKUP_NAME}::${BORGWRAPPER_BACKUP_TIMESTAMP_FORMAT} "${BORGWRAPPER_BACKUP_FILES[@]}";

	# notify UI
	if [ "${BORGWRAPPER_BACKUP_NOTIFY_UI}" = true ]; then
	    notify-send "Started backup" ${BORGWRAPPER_BACKUP_REPOSITORY}${BORGWRAPPER_BACKUP_NAME}::${BORGWRAPPER_BACKUP_TIMESTAMP_FORMAT};
	fi

	# check
	if [ "${BORGWRAPPER_BACKUP_CHECK}" = true ]; then

	    # use for first time creation
	    doCheck=false

	    if [ ! -f "${BORGWRAPPER_BACKUP_CHECK_FILE}" ]; then
	        touch ${BORGWRAPPER_BACKUP_CHECK_FILE}
	        doCheck=true
	    fi

	    # compare date
	    lastMod=$(date -r ${BORGWRAPPER_BACKUP_CHECK_FILE} +%s)
	    age=$((${BORGWRAPPER_BACKUP_TIMESTAMP_FORMAT} - ${lastMod}))

	    if [ "$age" -gt "${BORGWRAPPER_BACKUP_CHECK_MAX_AGE_IN_SECONDS}" ]; then
	        doCheck=true
	    fi


	    if [ "$doCheck" = true ]; then
	        ${BORG_BINARY} ${BORGWRAPPER_BORG_CHECK_PARAMS} ${BORGWRAPPER_BACKUP_REPOSITORY}${BORGWRAPPER_BACKUP_NAME};
	        touch ${BORGWRAPPER_BACKUP_CHECK_FILE}
	    fi
	fi

	# prune
	if [ "${BORGWRAPPER_BACKUP_PRUNE}" = true ]; then
	    ${BORG_BINARY} ${BORGWRAPPER_BORG_PRUNE_PARAMS} ${BORGWRAPPER_BACKUP_REPOSITORY}${BORGWRAPPER_BACKUP_NAME};
	fi

	# log
	if [ "${BORGWRAPPER_BACKUP_LOG}" = true ]; then

	    if [ "${BORGWRAPPER_BACKUP_LOG_PRUNE}" = true ] && [ -f "${BORGWRAPPER_BACKUP_LOG_FILE}" ]; then
	        rm ${BORGWRAPPER_BACKUP_LOG_FILE};
	    fi

	    touch ${BORGWRAPPER_BACKUP_LOG_FILE};
	    ${BORG_BINARY} ${BORGWRAPPER_BORG_LIST_PARAMS} ${BORGWRAPPER_BACKUP_REPOSITORY}${BORGWRAPPER_BACKUP_NAME} >> ${BORGWRAPPER_BACKUP_LOG_FILE};
	    echo "---" >> ${BORGWRAPPER_BACKUP_LOG_FILE};
	    ${BORG_BINARY} ${BORGWRAPPER_BORG_INFO_PARAMS} ${BORGWRAPPER_BACKUP_REPOSITORY}${BORGWRAPPER_BACKUP_NAME}::${BORGWRAPPER_BACKUP_TIMESTAMP_FORMAT} >> ${BORGWRAPPER_BACKUP_LOG_FILE};

	    if [ "${BORGWRAPPER_BACKUP_NOTIFY_VIA_MAIL}" = true ]; then
	    	local hostname=$(hostname)
	        cat ${BORGWRAPPER_BACKUP_LOG_FILE}|mailx -Ssendwait -s "[borgwrapper on ${hostname}] ${BORGWRAPPER_BACKUP_REPOSITORY}${BORGWRAPPER_BACKUP_NAME}::${BORGWRAPPER_BACKUP_TIMESTAMP_FORMAT} finished" ${BORGWRAPPER_BACKUP_NOTIFY_MAIL_ADDRESS};
	    fi
	fi

	# notify UI
	if [ "${BORGWRAPPER_BACKUP_NOTIFY_UI}" = true ]; then
	    notify-send "Finished backup" ${BORGWRAPPER_BACKUP_REPOSITORY}${BORGWRAPPER_BACKUP_NAME}::${BORGWRAPPER_BACKUP_TIMESTAMP_FORMAT};
	fi

	borgwrapper_post_backup;
}

# check requirements
CONFIG_FILE="$1";
FALLBACK_CONFIG_FILE="${HOME}/.borgwrapper.conf";
source_config "${CONFIG_FILE}" "${FALLBACK_CONFIG_FILE}";
apply_defaults;
check_required;

COMMAND="backup"
case "$COMMAND" in
	backup)
		backup;
		;;
	*)
		echo "Unsupported command or no command given" >&2
		usage;
		exit 1
		;;
esac