#!/usr/bin/sh
# vim:set ts=3:

set -e
shopt -s extglob

POOL="pool"
QUOTA="16G"

[[ -n ${SUDO_UID} ]] || exec /usr/bin/sudo $0

if [[ -n ${SIUEUSER} ]] && id -Gn ${SUDO_UID} | grep -q -w professors; then
	MECH_UID=$(id -u ${SIUEUSER})
	if ! [[ -n ${MECH_UID} ]]; then
		echo -e "\nERROR: Invalid value specified for SIUEUSER" 1>&2
		exit 1
	fi
else
	MECH_UID=${SUDO_UID}
fi

if [[ -z ${INSTANCE} ]]; then
	INSTANCE=0
else
	if ! [[ ${INSTANCE} =~ ^[0-9]$ ]]; then
		echo -e "\nERROR: Invalid value specified for INSTANCE" 1>&2
		exit 1
	fi
fi

ID="${MECH_UID#14}${INSTANCE}"

USERNAME="$(getent passwd ${MECH_UID} | cut -d ':' -f 1)"
SRVRNAME="${USERNAME}-${INSTANCE}"
SRVRPATH="/srv/${USERNAME}/${SRVRNAME}"

if [[ -n ${STARTNAT} ]] && id -Gn ${SUDO_UID} | grep -q -w professors; then
	INTERNET="--network-veth-extra=vn-${SRVRNAME}:host9"
fi

if [[ -n ${TEMPLATE} ]]; then
	if zfs list -o name | grep -q "^${POOL}/${SRVRNAME}$"; then
		echo -e "\nERROR: TEMPLATE specified for existing instance ${SRVRNAME}. Remove TEMPLATE and retry." 1>&2
		exit 1
	fi

	if ! [[ ${TEMPLATE} =~ ^[0-9]{3}\.[0-9](@[0-9]{12})?$ ]]; then
		echo -e "\nERROR: Invalid value specified for TEMPLATE" 1>&2
		exit 1
	fi

	if ! [[ ${TEMPLATE} =~ @ ]]; then
		TEMPLATE=$(grep -m 1 "^${POOL}/${TEMPLATE}@" ${0%/*}/default)
		if [[ -z ${TEMPLATE} ]]; then
			echo -e "\nERROR: Invalid value specified for TEMPLATE" 1>&2
			exit 1
		fi
	fi
fi

#if ! ip link list ${SRVRNAME} &> /dev/null; then
#	ip tuntap add dev ${SRVRNAME} mod tap
#	ip link set up ${SRVRNAME}
#fi
#
#if ! ip link list ns-${SRVRNAME} &> /dev/null; then
#	ip link add link ${SRVRNAME} name ns-${SRVRNAME} type macvlan mode passthru
#fi

mkdir -p ${SRVRPATH%/*}
if ! mountpoint -q ${SRVRPATH}; then
	if ! zfs list -o name | grep -q "^${POOL}/${SRVRNAME}$"; then
		if ! [[ -n ${TEMPLATE} ]]; then
			echo -e "\nERROR: TEMPLATE not specified for new instance ${SRVRNAME}. Specify TEMPLATE and retry." 1>&2
			exit 1
		fi

		zfs clone -o mountpoint=${SRVRPATH} ${TEMPLATE} ${POOL}/${SRVRNAME}
		zfs set quota=${QUOTA} ${POOL}/${SRVRNAME}

		TEMP=${ID##*(0)}
		for i in {2..0}; do
			ADDRESS[$i]=$(($TEMP%256))
			TEMP=$(($TEMP/256))
		done
	
		IFS='.' command eval 'NAT="10.${ADDRESS[*]}/8"'

		mkdir -p ${SRVRPATH}/etc/systemd/resolved.conf.d
		cat <<- END > ${SRVRPATH}/etc/systemd/resolved.conf.d/llmnr.conf
			[Resolve]
			LLMNR=true
		END

		cat <<- END > ${SRVRPATH}/etc/systemd/network/00-host0.network
			[Match]
			Virtualization=container
			Name=host0

			[Network]
			LinkLocalAddressing=0
			ConfigureWithoutCarrier=1
			Address=192.168.0.$((10+${INSTANCE}))/24
		END
	
		cat <<- END > ${SRVRPATH}/etc/systemd/network/00-host9.network
			[Match]
			Name=host9
	
			[Network]
			LinkLocalAddressing=0
			ConfigureWithoutCarrier=1
			Address=$NAT
			Gateway=10.255.255.254
			LLMNR=false
			DNS=146.163.252.126
			DNS=146.163.252.127
		END
	else
		zfs mount ${POOL}/${SRVRNAME}
	fi
fi

if machinectl show ${SRVRNAME} &> /dev/null; then
	OPTIONS="--quiet --wait --machine=${SRVRNAME} --collect --service-type=exec"
	if [[ -n ${SSH_ORIGINAL_COMMAND} ]]; then
		exec systemd-run ${OPTIONS} --pipe /usr/bin/bash -c "${SSH_ORIGINAL_COMMAND}"
	else
		exec systemd-run ${OPTIONS} --pty --send-sighup /usr/bin/login -H -f root
	fi
fi

if [[ -z ${SSH_ORIGINAL_COMMAND} ]]; then
	exec systemd-nspawn --settings=trusted --quiet --console=interactive \
	--link-journal=no --resolv-conf=off --timezone=off --capability=all --boot \
	--directory=${SRVRPATH} --private-users=false --bind-ro=/sys/module \
	--bind-ro=/lib/modules --network-zone=${USERNAME} ${INTERNET}
	# ip link del ns-${SRVRNAME}
	# ip link del ${SRVRNAME}
else
	echo -e "\nERROR: ${SRVRNAME} is not running" 1>&2
	exit 1
fi