#!/bin/sh

set -e

XDG_DATA_HOME="${XDG_DATA_HOME:-$HOME/.local/share}"
XDG_DATA_DIRS="${XDG_DATA_DIRS:-/usr/local/share:/usr/share}"

# example: TARBACK_REMOTE="ssh myuser@myserver" ./tarback ...
TARBACK_REMOTE="${TARBACK_REMOTE:-}"
# maybe the command needs to be transformed before being passed to the
# remote command, see _transform_ssh_command for an example
TARBACK_TRANSFORM_REMOTE_COMMAND="${TARBACK_TRANSFORM_REMOTE_COMMAND:-}"
# shellcheck disable=SC2016 # disable variable not expanding hint
[ -z "$TARBACK_TAR_CREATE_COMMAND" ] \
    && TARBACK_TAR_CREATE_COMMAND='tar c -C "$(dirname "$1")" "$(basename "$1")"'
# shellcheck disable=SC2016 # disable variable not expanding hint
[ -z "$TARBACK_TAR_EXTRACT_COMMAND" ] \
    && TARBACK_TAR_EXTRACT_COMMAND='tar x -C "$(dirname "$1")"'
[ -z "$TARBACK_COMPRESSION" ] && TARBACK_COMPRESSION="xz"
[ -z "$TARBACK_SPLIT" ] && TARBACK_SPLIT="split -b $((128*1024*1024)) -"
[ -z "$TARBACK_MERGE" ] && TARBACK_MERGE='cat'
[ -z "$TARBACK_PLUGIN_SEARCH_PATH" ] \
    && TARBACK_PLUGIN_SEARCH_PATH="$(dirname "$0"):$XDG_DATA_HOME:$XDG_DATA_DIRS"

TARBACK_PLUGIN_SEARCH_PATH="$(echo "$TARBACK_PLUGIN_SEARCH_PATH" | tr ':'  '\n')"

_transform_split_name() {
    command_name="$(echo "$TARBACK_SPLIT" | awk '{print $1}')"
    if echo "$command_name" | grep -q 'split'; then
        echo "$1.part"
    else
        echo "$1"
    fi
}

_transform_ssh_command() {
    command_name="$(echo "$TARBACK_REMOTE" | awk '{print $1}')"
    if echo "$command_name" | grep -q 'ssh'; then
        echo "'$1'"
    else
        echo "$1"
    fi
}

_transform_remote() {
    r="$1"
    # TODO add more transformers
    for t in _transform_ssh_command "$TARBACK_TRANSFORM_REMOTE_COMMAND"; do
        [ -z "$t" ] && continue # skip empty transformers
        r="$("$t" "$r")"
    done
    echo "$r"
}

create() {
    # $1 ... src
    # $2 ... dst
    src="$1"
    dst="$(_transform_split_name "$2")"
    tarback_tar_create_command="$(_transform_remote "$TARBACK_TAR_CREATE_COMMAND")"
    $TARBACK_REMOTE sh -c "$tarback_tar_create_command" - "$src" \
        | $TARBACK_COMPRESSION \
        | $TARBACK_SPLIT "$dst"
}

restore() {
    src="$(_transform_split_name "$1")"
    dst="$2"
    tarback_tar_extract_command="$(_transform_remote "$TARBACK_TAR_EXTRACT_COMMAND")"
    $TARBACK_MERGE "$src"* \
        | $TARBACK_COMPRESSION --decompress --stdout \
        | $TARBACK_REMOTE sh -c "$tarback_tar_extract_command" - "$dst"
}

short_options='p:'
while getopts "$short_options" arg; do
    case "$arg" in
        p)
            # source plugin file
            # shellcheck disable=SC1090 # disable cannot follow source
            sourced=false
            for loc in $TARBACK_PLUGIN_SEARCH_PATH; do
                if [ -e "$loc/tarback/$OPTARG.sh" ]; then
                    . "$loc/tarback/$OPTARG.sh"
                    sourced=true
                    break
                fi
            done
            if ! "$sourced"; then
                echo "couldn't find plugin $OPTARG" >&2
                exit 1
            fi
            shift 2
            ;;
        *)
            echo "unknown option $1" >&2
            exit 1
            ;;
    esac
done

case "$1" in
    create)
        shift
        if [ "$#" -eq 2 ]; then
            create "$@"
        else
            echo 'not enough arguments, expected 2: src dest' >&2
            exit 1
        fi
        ;;
    restore)
        shift
        if [ "$#" -eq 2 ]; then
            restore "$@"
        else
            echo 'not enough arguments, expected 2: src dest' >&2
            exit 1
        fi
        ;;
esac