system-alternatives

#!/system/bin/sh
set -e
DB=/botbrew/var/lib/system-alternatives
HASHDB="${DB}/md5"
str_hash() {	# <string>
	echo "$1" | md5sum | awk '{ print $1 }'
}
file_hash() {	# <path>
	md5sum "$1" | awk '{ print $1 }'
}
master_restore() {	# <master> <path-hash>
	MASTER="$1"
	PHASH="$2"
	if [ -e "${HASHDB}/${PHASH}/master" ]; then
		busybox dd if="${HASHDB}/${PHASH}/master" of="$MASTER"
		if [ -e "${MASTER}" ]; then
			return
		else
			return 1
		fi
	else
		return 1
	fi
}
master_check() {	# <master> <path-hash> [<alternative>]
	MASTER="$1"
	PHASH="$2"
	ALT="$3"
	if [ -e "${MASTER}" ]; then
		if [ "${ALT}" != "" ]; then
			if [ -e "${ALT}" ] && [ "`file_hash "${MASTER}"`" != "`file_hash "${ALT}"`" ]; then
				return 1
			else
				return 0
			fi
		else
			if [ -e "${HASHDB}/${PHASH}/master" ] && [ "`file_hash "${MASTER}"`" != "`file_hash "${HASHDB}/${PHASH}/master"`" ]; then
				return 1
			else
				return 0
			fi
		fi
	else
		if [ "${ALT}" != "" ]; then
			if [ -e "${ALT}" ]; then
				return 1
			else
				return 0
			fi
		else
			if [ -e "${HASHDB}/${PHASH}/master" ]; then
				return 1
			else
				return 0
			fi
		fi
	fi
}
master_ensure() {	# <master> <path-hash> [<file-hash>]
	MASTER="$1"
	PHASH="$2"
	FHASH="$3"
	if [ -e "${MASTER}" ]; then
		if [ "${FHASH}" = "" ]; then FHASH=`file_hash "${MASTER}"`; fi
		busybox mkdir -p "${HASHDB}/${PHASH}/history"
		busybox ln -sf "${MASTER}" "${HASHDB}/${PHASH}/link"
		if ! [ -e "${HASHDB}/${PHASH}/history/${FHASH}" ]; then
			# master hasn't been seen before
			busybox dd if="$MASTER" of="${HASHDB}/${PHASH}/master"
			busybox ln -sf "../master" "${HASHDB}/${PHASH}/history/${FHASH}"
		fi
	elif master_restore "${MASTER}" "${PHASH}"; then
		master_ensure "${MASTER}" "${PHASH}"
	else
		return 1
	fi
}
master_clean() {
	for item in "${HASHDB}/"*"/history/"*; do
		if ! [ -e "${item}" ]; then
			rm "${item}" || true
		fi
	done
}
case "$1" in
	check)	# <master> [<alternative>]
		shift
		MASTER=`busybox readlink -f "$1"`
		ALT=`busybox readlink -f "$2"`
		PHASH=`str_hash "${MASTER}"`
		master_check "${MASTER}" "${PHASH}" "${ALT}"
		;;
	install)	# <master> <alternative>
		shift
		MASTER=`busybox readlink -f "$1"`
		ALT=`busybox readlink -f "$2"`
		PHASH=`str_hash "${MASTER}"`
		master_ensure "${MASTER}" "${PHASH}"
		if [ -e "${ALT}" ]; then
			FHASH=`file_hash "${ALT}"`
			busybox ln -sf "${ALT}" "${HASHDB}/${PHASH}/history/${FHASH}"
			busybox dd if="${ALT}" of="${MASTER}"
		else
			echo "${ALT}"
		fi
		;;
	list)	# <master>
		shift
		MASTER=`busybox readlink -f "$1"`
		PHASH=`str_hash "${MASTER}"`
		for item in "${HASHDB}/${PHASH}/history/"*; do
			if [ -L "${item}" ]; then
				echo `busybox readlink -f "${item}"`
			fi
		done
		;;
	restore)	# <master>
		shift
		MASTER=`busybox readlink -f "$1"`
		PHASH=`str_hash "${MASTER}"`
		master_ensure "${MASTER}" "${PHASH}"
		master_restore "${MASTER}" "${PHASH}"
		rm -r "${HASHDB}/${PHASH}"
		;;
	clean)
		master_clean
		;;
	selftest)
		echo "\033[1m*** SELFTEST\033[0m"
		TEST="/system/framework/test"
		DIR="/cache/sa-test"
		busybox mkdir -p "${DIR}"
		echo "\033[1m*** creating test files\033[0m"
		set -x
		echo "test0" > "${DIR}/t0"
		echo "test1" > "${DIR}/t1"
		echo "test2" > "${DIR}/t2"
		echo "test3" > "${DIR}/t3"
		echo "test4" > "${DIR}/t4"
		set +x
		echo "\033[1m*** installing master file\033[0m"
		set -x
		cp "${DIR}/t0" "${TEST}"; cat "${TEST}"
		set +x
		echo "\033[1m*** installing \`t1' containing 'test1'\033[0m"
		set -x
		"$0" install "${TEST}" "${DIR}/t1"; cat "${TEST}"
		set +x
		echo "\033[1m*** installing \`t2' containing 'test2'\033[0m"
		set -x
		"$0" install "${TEST}" "${DIR}/t2"; cat "${TEST}"
		set +x
		echo "\033[1m*** known alternatives:\033[0m"
		set -x
		"$0" list "${TEST}"
		set +x
		echo "\033[1m*** checking difference between master and \`t1'\033[0m"
		set -x
		"$0" check "${TEST}" "${DIR}/t1" && echo "same" || echo "different"
		set +x
		echo "\033[1m*** checking difference between master and \`t2'\033[0m"
		set -x
		"$0" check "${TEST}" "${DIR}/t2" && echo "same" || echo "different"
		set +x
		echo "\033[1m*** checking difference between master and backup\033[0m"
		set -x
		"$0" check "${TEST}" && echo "same" || echo "different"
		set +x
		echo "\033[1m*** restoring master file\033[0m"
		set -x
		"$0" restore "${TEST}"; cat "${TEST}"
		set +x
		echo "\033[1m*** installing test files\033[0m"
		set -x
		"$0" install "${TEST}" "${DIR}/t1"
		"$0" install "${TEST}" "${DIR}/t2"
		cat "${TEST}"
		set +x
		echo "\033[1m*** known alternatives:\033[0m"
		set -x
		"$0" list "${TEST}"
		set +x
		echo "\033[1m*** updating master file\033[0m"
		set -x
		cp "${DIR}/t3" "${TEST}"; cat "${TEST}"
		set +x
		echo "\033[1m*** restoring master file\033[0m"
		set -x
		"$0" restore "${TEST}"; cat "${TEST}"
		set +x
		echo "\033[1m*** updating master file\033[0m"
		set -x
		cp "${DIR}/t3" "${TEST}"; cat "${TEST}"
		set +x
		echo "\033[1m*** installing \`t4' containing 'test4'\033[0m"
		set -x
		"$0" install "${TEST}" "${DIR}/t4"; cat "${TEST}"
		set +x
		echo "\033[1m*** restoring master file\033[0m"
		set -x
		"$0" restore "${TEST}"; cat "${TEST}"
		set +x
		echo "\033[1m*** cleaning up\033[0m"
		set -x
		rm -r "${DIR}"
		"$0" clean
		set +x
		echo "\033[1m*** known alternatives:\033[0m"
		set -x
		"$0" list "${TEST}"
		set +x
		rm "${TEST}"
		;;
esac