#!/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

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

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

# naive test for .deb file
# also check `ar' presense
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

decomp=
case "${data_tar}" in
data.tar.gz)  decomp='gzip' ;;
data.tar.xz)  decomp='xz'   ;;
data.tar.zst) decomp='zstd' ;;
esac

if [ -z "${decomp}" ] ; then
	log "unable to handle '${data_tar}' from $1 - compression type isn't known to script"
	exit 1
fi

if ! command -v ${decomp} >/dev/null ; then
	log "enable to find '${decomp}'"
	exit 1
fi

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