#!/bin/sh

set -e

NCPUS=$(sysctl hw.ncpuonline | sed 's/.*=//')

# Try to find a valid way to become root if not already
SUDO=
if [ -e '/etc/doas.conf' ]; then
	SUDO='/usr/bin/doas'
elif [ -x '/usr/local/bin/sudo' ]; then
	SUDO='/usr/local/bin/sudo'
fi

# Bail out if not root and neither sudo or doas was found.
_uid=$(id -u)
if [ -z ${SUDO} -a \( ${_uid} -ne 0 \) ]; then
	echo 'Need a way to become root, neither sudo or doas found...' 1>&2
	exit 1
elif [ ${_uid} -eq 0 ]; then
	# Clear SUDO if already root
	SUDO=
fi

# Find the source tree for the base system
if [ -e /etc/mk.conf ]; then
	BSDSRCDIR=$(make -f /etc/mk.conf -V BSDSRCDIR)
	BSDOBJDIR=$(make -f /etc/mk.conf -V BSDOBJDIR)
fi
BSDSRCDIR=${BSDSRCDIR:=/usr/src}
BSDOBJDIR=${BSDOBJDIR:=/usr/obj}

START_TIME=$(date)
# Make a backup of kernel config files before cleaning /usr/obj
_kernel_obj_tar=$(mktemp) || {
	echo "Unable to create temporary file for kernel obj backup"
	exit 1
}

if stat -q -f '' /usr/obj/sys/arch/*/compile/[GR]* ; then
	tar -czf ${_kernel_obj_tar} /usr/obj/sys/arch/*/compile/[GR]*
else
	rm ${_kernel_obj_tar}
fi

cd ${BSDOBJDIR} && mkdir -p .old && ${SUDO} mv * .old && ${SUDO} rm -rf .old &
cd ${BSDSRCDIR} && ${SUDO} make obj
cd ${BSDSRCDIR} || { echo "Unable to chdir to source directory" ; exit 1; }
${SUDO} make build -j ${NCPUS}
RESULT=$?
test -f ${_kernel_obj_tar} && \
	tar -C / -xzphf ${_kernel_obj_tar} && rm ${_kernel_obj_tar}
END_TIME=$(date)
echo "Build started at ${START_TIME}, ended at ${END_TIME}"
exit ${RESULT}