#!/bin/sh
set -ef

# assume that both data.tar and control.tar are compressed with same compressor
# if dpkg-deb can handle control.tar.* then it will handle data.tar.* too
if dpkg-deb --ctrl-tarfile "$1" >/dev/null 2>&1 ; then
	exec dpkg-deb --fsys-tarfile "$1"
fi

# here we're unpacking data.tar.* manually

me=${0##*/}
log() { echo "${me}: $*" 1>&2 ; }

have_cmd() {
	if ! command -v "$1" >/dev/null ; then
		log "unable to find '$1' - install package '$2' first"
		exit 1
	fi
}

have_cmd ar binutils

# naive test for .deb file
ar t "$1" >/dev/null

data_tar=
while read -r pkg_member ; do
	[ -n "${pkg_member}" ] || continue

	if [ -n "${data_tar}" ] ; then
		log "extra data tarball '${pkg_member}' in package $1 - bailing out"
		exit 1
	fi

	data_tar="${pkg_member}"
done <<-EOF
$(ar t "$1" | grep -E '^data\.tar')
EOF

if [ -z "${data_tar}" ] ; then
	log "unable to find data.tar.* in $1 - bailing out"
	exit 1
fi

decomp= ; decomp_pkg=
case "${data_tar}" in
data.tar.gz)  decomp='gzip' decomp_pkg='gzip' ;;
data.tar.xz)  decomp='xz'   decomp_pkg='xz-utils' ;;
data.tar.zst) decomp='zstd' decomp_pkg='zstd' ;;
*)
	log "unable to handle '${data_tar}' from $1 - compression type isn't known to script"
	exit 1
;;
esac

have_cmd ${decomp} ${decomp_pkg}

ar p "$1" "${data_tar}" | ${decomp} -d