#!/bin/sh

set -eu

_="${XDG_DATA_HOME:=$HOME/.local/share}"
_="${XDG_DATA_DIRS:=/usr/local/share:/usr/share}"
_="${XDG_CONFIG_HOME:=$HOME/.config}"
_="${XDG_CONFIG_DIRS:=/etc}"

TARBACK_REMOTE_DEFAULT=
TARBACK_TRANSFORM_REMOTE_COMMAND_DEFAULT=
TARBACK_TRANSFORM_REMOTE_ARGUMENT_COMMAND_DEFAULT=
# shellcheck disable=SC2016 # disable variable not expanding hint
TARBACK_TAR_CREATE_COMMAND_DEFAULT='tar c -C "$1" .'
# shellcheck disable=SC2016 # disable variable not expanding hint
TARBACK_TAR_CREATE_ALT_COMMAND_DEFAULT='tar c -C "$(dirname "$1")" "$(basename "$1")"'
TARBACK_TAR_CREATE_USE_ALT_COMMAND_DEFAULT='[ ! -d "$1" ]'
# shellcheck disable=SC2016 # disable variable not expanding hint
TARBACK_TAR_EXTRACT_COMMAND_DEFAULT='tar x -C "$1"'
# shellcheck disable=SC2016 # disable variable not expanding hint
TARBACK_TAR_EXTRACT_ALT_COMMAND_DEFAULT='tar x -C "$(dirname "$1")"'
TARBACK_TAR_EXTRACT_USE_ALT_COMMAND_DEFAULT='[ ! -e "$1" ] && [ -d "$(dirname "$1")" ]'
TARBACK_COMPRESSION_DEFAULT='xz'
TARBACK_SPLIT_DEFAULT="split -b $((128*1024*1024)) -"
TARBACK_MERGE_DEFAULT='cat'
TARBACK_PLUGIN_SEARCH_PATH_DEFAULT="$(dirname "$0"):$XDG_DATA_HOME:$XDG_DATA_DIRS"
TARBACK_CONFIG_SEARCH_PATH_DEFAULT="$(dirname "$0"):$XDG_CONFIG_HOME:$XDG_CONFIG_DIRS"

_="${TARBACK_PLUGIN_SEARCH_PATH:=$TARBACK_PLUGIN_SEARCH_PATH_DEFAULT}"
_="${TARBACK_CONFIG_SEARCH_PATH:=$TARBACK_CONFIG_SEARCH_PATH_DEFAULT}"
TARBACK_PLUGIN_SEARCH_PATH="$(echo "$TARBACK_PLUGIN_SEARCH_PATH" | tr ':'  '\n')"
TARBACK_CONFIG_SEARCH_PATH="$(echo "$TARBACK_CONFIG_SEARCH_PATH" | tr ':'  '\n' | tac)"

# load configs
for config_dir in $TARBACK_CONFIG_SEARCH_PATH; do
    config_file="$config_dir/tarback/config.sh"
    [ ! -f "$config_file" ] && continue
    . "$config_file"
done

# example: TARBACK_REMOTE="ssh myuser@myserver" ./tarback ...
TARBACK_REMOTE="${TARBACK_REMOTE:-$TARBACK_REMOTE_DEFAULT}"
# 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_DEFAULT}"
_="${TARBACK_TRANSFORM_REMOTE_ARGUMENT_COMMAND:=$TARBACK_TRANSFORM_REMOTE_ARGUMENT_COMMAND_DEFAULT}"
_="${TARBACK_TAR_CREATE_COMMAND:=$TARBACK_TAR_CREATE_COMMAND_DEFAULT}"
_="${TARBACK_TAR_CREATE_ALT_COMMAND:=$TARBACK_TAR_CREATE_ALT_COMMAND_DEFAULT}"
_="${TARBACK_TAR_CREATE_USE_ALT_COMMAND:=$TARBACK_TAR_CREATE_USE_ALT_COMMAND_DEFAULT}"
_="${TARBACK_TAR_EXTRACT_COMMAND:=$TARBACK_TAR_EXTRACT_COMMAND_DEFAULT}"
_="${TARBACK_TAR_EXTRACT_ALT_COMMAND:=$TARBACK_TAR_EXTRACT_ALT_COMMAND_DEFAULT}"
_="${TARBACK_TAR_EXTRACT_USE_ALT_COMMAND:=$TARBACK_TAR_EXTRACT_USE_ALT_COMMAND_DEFAULT}"
_="${TARBACK_COMPRESSION:=$TARBACK_COMPRESSION_DEFAULT}"
_="${TARBACK_SPLIT:=$TARBACK_SPLIT_DEFAULT}"
_="${TARBACK_MERGE:=$TARBACK_MERGE_DEFAULT}"
_="${TARBACK_EXTENSION:=tar.$TARBACK_COMPRESSION}"

_transform_split_name() {
    case "$1" in
        *"$TARBACK_EXTENSION")
            n="$1"
            ;;
        *)
            n="$1.$TARBACK_EXTENSION"
            ;;
    esac
    command_name="$(echo "$TARBACK_SPLIT" | awk '{print $1}')"
    if echo "$command_name" | grep -q 'split'; then
        n="$n.part"
    fi
    echo "$n"
}

_transform_remote() {
    r="$1"
    if [ -n "$TARBACK_TRANSFORM_REMOTE_COMMAND" ]; then
        r="$("$TARBACK_TRANSFORM_REMOTE_COMMAND" "$r")"
    fi
    echo "$r"
}

_transform_argument() {
    a="$1"
    if [ -n "$TARBACK_TRANSFORM_REMOTE_ARGUMENT_COMMAND" ]; then
        a="$("$TARBACK_TRANSFORM_REMOTE_ARGUMENT_COMMAND" "$a")"
    fi
    echo "$a"
}

_create() {
    # $1 ... src
    # $2 ... dst
    src="$1"
    dst="$(_transform_split_name "$2")"
    if ! sh -c "$TARBACK_TAR_CREATE_USE_ALT_COMMAND" - "$src"; then
        tarback_tar_create_command="$TARBACK_TAR_CREATE_COMMAND"
    else
        tarback_tar_create_command="$TARBACK_TAR_CREATE_ALT_COMMAND"
    fi
    tarback_tar_create_command="$(_transform_remote "$tarback_tar_create_command")"
    $TARBACK_REMOTE sh -c "$tarback_tar_create_command" - "$(_transform_argument "$src")" \
        | $TARBACK_COMPRESSION \
        | $TARBACK_SPLIT "$dst"
}

create() {
    _create "$@"
}

_restore() {
    src="$(_transform_split_name "$1")"
    dst="$2"
    if ! sh -c "$TARBACK_TAR_EXTRACT_USE_ALT_COMMAND" - "$dst"; then
        tarback_tar_extract_command="$TARBACK_TAR_EXTRACT_COMMAND"
    else
        tarback_tar_extract_command="$TARBACK_TAR_EXTRACT_ALT_COMMAND"
    fi
    tarback_tar_extract_command="$(_transform_remote "$tarback_tar_extract_command")"
    $TARBACK_MERGE "$src"* \
        | $TARBACK_COMPRESSION --decompress --stdout \
        | $TARBACK_REMOTE sh -c "$tarback_tar_extract_command" - "$(_transform_argument "$dst")"
}

restore() {
    _restore "$@"
}

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

shift $((OPTIND-1))

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