nix/hosts/elara/build-tarball.nix

{
  config,
  pkgs,
  lib,
  ...
}:
# FIXME: https://github.com/nix-community/NixOS-WSL/issues/343
# FIXME: https://github.com/nix-community/NixOS-WSL/issues/612
{
  system.build.tarballBuilder = lib.mkForce (
    pkgs.writeShellApplication {
      name = "nixos-wsl-tarball-builder";

      runtimeInputs = [
        config.nix.package
        pkgs.coreutils
        pkgs.e2fsprogs
        pkgs.gnutar
        pkgs.nixos-install-tools
        pkgs.pigz
      ];

      text = ''
        if ! [ "$EUID" -eq 0 ]; then
          echo "This script must be run as root!"
          exit 1
        fi

        out="nixos-wsl.tar.gz"
        extra_files=""

        positional=()
        while [ $# -gt 0 ]; do
          case "$1" in
            --extra-files=*)
              extra_files="''${1#*=}"
              ;;
            --extra-files)
              shift
              extra_files="$1"
              ;;
            -*)
              echo "Unknown option: $1"
              echo "Usage: $0 [--extra-files PATH] [output.tar.gz]"
              exit 1
              ;;
            *)
              positional+=("$1")
              ;;
          esac
          shift
        done

        if [ ''${#positional[@]} -gt 0 ]; then
          out="''${positional[0]}"
        fi

        root=$(mktemp -p "''${TMPDIR:-/tmp}" -d nixos-wsl-tarball.XXXXXXXXXX)
        # FIXME: fails in CI for some reason, but we don't really care because it's CI
        trap 'chattr -Rf -i "$root" || true && rm -rf "$root" || true' INT TERM EXIT

        if [ -n "$extra_files" ]; then
          echo "[NixOS-WSL] Copying extra files to $root..."
          cp --verbose --archive --no-target-directory "$extra_files" "$root"
        fi

        chmod o+rx "$root"

        echo "[NixOS-WSL] Installing..."
        nixos-install \
          --root "$root" \
          --no-root-passwd \
          --system ${config.system.build.toplevel} \
          --substituters ""

        echo "[NixOS-WSL] Adding channel..."
        nixos-enter --root "$root" --command 'HOME=/root nix-channel --add https://github.com/nix-community/NixOS-WSL/archive/refs/heads/main.tar.gz nixos-wsl'

        echo "[NixOS-WSL] Compressing..."
        tar -C "$root" \
          -c \
          --sort=name \
          --mtime='@1' \
          --owner=0 \
          --group=0 \
          --numeric-owner \
          . \
        | pigz > "$out"
      '';
    }
  );
}