set -euo pipefail

usage() {
	echo "Usage: $(basename "$0") [-n <flake name>] [-fqwx] <nixos-rebuild args...>
	This script is a wrapper around nixos-rebuild, designed to simplify applying configurations and testing in vm. Requires super-user privileges.

	examples:
		$(basename "$0") -n nixos switch
		- switch configuration to flake named nixos

		$(basename "$0") -f switch
		- switch configuration and don't ask confirmation

		$(basename "$0") -fwx
		- build a fresh vm image and run it

	-f
		Don't ask for confirmation about deleting the /etc/nixos directory.
	-n name
		Flake name. Defaults to your hostname.
	-q
		Don't output messages from this script.
	-w
		Wipes the vm disk file before running qemu, has no effect if not using the -x option.
		Building the vm after making changes to configs lead to errors without this.
	-x
		Run the vm automatically after build. This implies 'build-vm' argument.
		Also forwards host port 2222 to quest port 22." 1>&2
	exit 1
}

log() {
	if [ "$quiet" != true ]; then
		echo "[$(basename "$0")] $@"
	fi
}

die() {
	echo "$@"
	exit 1
}

[ "$#" -eq 0 ] && usage

original_dir="$(realpath ./)"
source_dir="$(realpath "$(dirname "$0")")"

name="$(hostname)"
wipe_vm=""
execute_vm=""
force=""
quiet=""

while getopts ":n::fqwx" o; do
	case "${o}" in
		n)
			name="$OPTARG"
			;;
		f)
			force=true
			;;
		q)
			quiet=true
			;;
		w)
			wipe_vm=true
			;;
		x)
			execute_vm=true
			;;
		*)
			usage
			;;
	esac
done
shift $((OPTIND-1))

if [ ! -d "$source_dir" ]; then
	die "$source_dir is not a directory"
fi

dest_dir="/etc/nixos"
if [ "$(realpath "$dest_dir")" != "$(realpath "$source_dir")" ]; then
	if [ "$force" != true ]; then
		confirm="n"
		read -p "This will remove your /etc/nixos directory! Do you want to proceed? (y/n) " confirm
		case "$confirm" in
			y) ;;
			*) die "aborting...";;
		esac
	fi
	log "Clearing /etc/nixos"
	rm -rf "$dest_dir"
	log "Copying $source_dir to $dest_dir"
	cp -r "$source_dir" "$dest_dir"
	cd "$dest_dir" || exit 1
else
	log "WARNING: It's recommended to clone this repo somewhere else than $dest_dir"
fi

sed -Ei 's;^(hardware-configuration.nix)$;#\1;' .gitignore
[ ! -f 'hardware-configuration.nix' ] && log "Adding hardware-configuration.nix" && nixos-generate-config --show-hardware-config > hardware-configuration.nix
git add hardware-configuration.nix

cd "$original_dir" || exit 1
if [ "$execute_vm" = true ]; then
	# Run the vm and forward ports
	[ "$wipe_vm" = true ] && rm -f *.qcow2
	log "Running: nixos-rebuild --flake \"$dest_dir/#${name}\" $@ build-vm && QEMU_NET_OPTS=\"hostfwd=tcp::2222-:22\" ./result/bin/run-${name}-vm"
	nixos-rebuild --flake "$dest_dir/#${name}" "$@" build-vm && QEMU_NET_OPTS="hostfwd=tcp::2222-:22" ./result/bin/run-${name}-vm
else
	log "Running: nixos-rebuild --flake \"$dest_dir/#${name}\" $@"
	nixos-rebuild --flake "$dest_dir/#${name}" "$@"
fi