#!/bin/sh

_usage () {
	cat <<EOF
Usage: ${1##*/} [-m METHOD] [-v] FILES|FOLDERS

Create an archive in current folder from a single or multiples
files/folders. Each input entry will be at archive root (no absolute path is
used). If only one file/folder is given as input, then the archive is named
after this input. Otherwise it is named after current PWD.

  -h:  Display this help.
  -i:  The archive is created without owner/group information. (GNU tar only.)
  -m:  Choose compression method.
         * gz:   gzip (default).
         * none: Simple tar archive.
         * xz:   LZMA.
  -s:  Archive each input entry an individual file.
  -v:  Exclude VCS data. (GNU tar only.)
EOF
}

OUTPATH="$PWD"
ARCEXT=".gz"
ARCOPT="z"
OPTIONS=""
OPT_SPLIT=false
while getopts ":him:sv" opt; do
	case $opt in
	h)
		_usage "$0"
		exit 1 ;;
	i)
		OPTIONS="$OPTIONS --owner=root --group=root --numeric-owner" ;;
	m)
		[ "$OPTARG" = "gz" ] && ARCEXT=".gz" && ARCOPT="z"
		[ "$OPTARG" = "xz" ] && ARCEXT=".xz" && ARCOPT="J"
		[ "$OPTARG" = "none" ] && ARCEXT="" && ARCOPT=""
		;;
	s)
		OPT_SPLIT=true ;;
	v)
		OPTIONS="$OPTIONS --exclude-vcs" ;;
	\?)
		_usage "$0"
		exit 1 ;;
	esac
done


shift $(($OPTIND - 1))

if [ $# -eq 0 ]; then
	_usage "$0"
	exit 1
fi

## We need 'realpath' since we need to work on the real path for the input
## files/folders and the archive location. Otherwise we could have troubles with
## circular symlinks and so on.
if ! command -v realpath >/dev/null 2>&1; then
	echo >&2 "'realpath' not found in PATH. Exiting."
	exit 1
fi

_archive () {
	## Only one input entry: use it as base name for the archive.
	if [ $# -eq 1 ]; then
		REALPATH="$(realpath "$1")"
		OUTFILE="${REALPATH##*/}-$(date +%F-%H%M%S).tar${ARCEXT}"
	else
		OUTFILE="${PWD##*/}-$(date +%F-%H%M%S).tar${ARCEXT}"
	fi

	REALPWD="$(realpath "$PWD")"
	for i; do
		REALPATH="$(realpath "$i")"

		## Check if one of the arguments is current folder. We need to make sure the
		## archive is not created in an input folder, otherwise it will include
		## itself.
		if [ "$REALPATH" = "$REALPWD" ]; then
			OUTPATH="$(realpath "$REALPWD/..")"
			break
		fi
	done

	if [ ! -w "$OUTPATH" ]; then
		echo "[$OUTPATH] is not writable. Exiting."
		return
	fi

	echo "==> [$OUTPATH/$OUTFILE]"
	for i; do
		REALPATH="$(realpath "$i")"
		echo "${REALPATH}" >&2
		echo "-C '${REALPATH%/*}'"
		echo "${REALPATH##*/}"
	done | tar $OPTIONS -${ARCOPT}cf "$OUTPATH/$OUTFILE" -T -
}

if $OPT_SPLIT; then
	for j ; do
		_archive "$j"
	done
else
	_archive "$@"
fi