#!/bin/sh

set -eu

build_dir="${build_dir:-/tmp/nixos-vm}"
mount_point="${mount_point:-/tmp/fs}"
qcow2="${qcow2:-${build_dir}/$(hostname -s).qcow2}"

echo "[+] configuration:"
echo "    build dir:    ${build_dir}"
echo "  mount point:    ${mount_point}"
echo "        image:    ${qcow2}"

build_nixos_vm () {
    echo "[+] updating NixOS config"
    cd /etc/nixos
    doas git pull --rebase local master

    if [[ -d "${build_dir}" ]]
    then
	echo "[+] removing ${build_dir}"
	sleep 2
	rm -r "${build_dir}"
    fi

    mkdir "${build_dir}"
    cd "${build_dir}"
    doas nixos-rebuild build-vm

    echo "[+] Spinning up VM; kill it when you see the line"
    echo "	'Virtualisation disk image created.'"
    "${build_dir}/result/bin/run-$(hostname -s)-vm"
    doas qemu-img resize "${qcow2}" 256G

    doas modprobe nbd max_part=8

    echo "[+] connecting to network block driver"
    echo "    note: on failure, you may need to manually run"
    echo "    doas qemu-nbd --disconnect /dev/nbd0"
    doas qemu-nbd --connect=/dev/nbd0 ${qcow2}

    if [[ -d "${mount_point}" ]]
    then
	echo "[+] removing ${mount_point}"
	sleep 2
	rm -r "${mount_point}"
    fi

    mkdir -p "${mount_point}"
    doas mount /dev/nbd0 "${mount_point}"

    rsync --progress --exclude 'data' --exclude 'tmp' --exclude 'src' \
	  -auvz "${HOME}/" "${mount_point}/home/kyle/"

    echo "[+] finished, cleaning up"
    doas umount "${mount_point}"
    doas qemu-nbd --disconnect /dev/nbd0
    doas rmdir "${mount_point}"
}

cleanup () {
    if [[ -d "${build_dir}" ]]
    then
	echo "[+] removing ${build_dir}"
	sleep 2
	rm -r "${build_dir}"
    fi

    if [[ ! -z "$(mount | grep /dev/nbd0)" ]]
    then
	echo "[+] unmounting network block device"
	doas umount /dev/nbd0
    fi

    echo "[+] disconnecting network block device"
    echo "    it's okay if this fails"
    doas qemu-nbd --disconnect /dev/nbd0

    if [[ -d "${mount_point}" ]]
    then
	echo "[+] removing ${mount_point}"
	sleep 2
	rm -r "${mount_point}"
    fi
}

case "${1:-build}" in
    build)
	build_nixos_vm
	;;
    cleanup)
	cleanup
	;;
    *)
	echo "[!] Valid commands are build, cleanup"
	exit 1
	;;
esac