#!/usr/bin/env bash

set -e

release="${1:-unstable}"
arch="${2:-x86_64}"

if [ "$(uname -m)" != "${arch}" ]
then
	echo "Cross building is not supported" >&2
	exit 1
fi

# In a non-nixos system we first need to install nix
if ! [ -x "$(command -v nix)" ]
then
	# Prepare /nix
	sudo mkdir /nix
	sudo chown build /nix
	# Install nix
	curl -L https://nixos.org/nix/install > ~/install-nix
	sh ~/install-nix --no-daemon --no-channel-add
	# Activate nix
	. ~/.nix-profile/etc/profile.d/nix.sh
fi

# Check that nix works
nix --extra-experimental-features nix-command store ping || nix ping-store # legacy fallback

# We switch to a nixos channel.
# This is important because the nixos-* channels,
# in contrast with the nixpkgs-* ones, must pass some additional
# tests (such as being able to boot) before advancing.
nix-channel --add "https://nixos.org/channels/nixos-${release}" nixpkgs
nix-channel --update
# Generate the image
nix-build image.nix
# result/root.img.qcow2 is on a read-only mount. Copy and chmod it.
mkdir -p "${release}/${arch}"
cp "result/nixos.qcow2" "${release}/${arch}/root.img.qcow2"
chmod u+w "${release}/${arch}/root.img.qcow2"