{ pkgs, ... }:
let

  container =
    { config, ... }:
    {
      # We re-use the NixOS container option ...
      boot.isContainer = true;
      # ... and revert unwanted defaults
      networking.useHostResolvConf = false;

      # use networkd to obtain systemd network setup
      networking.useNetworkd = true;
      networking.useDHCP = false;

      # systemd-nspawn expects /sbin/init
      boot.loader.initScript.enable = true;

      imports = [ ../modules/profiles/minimal.nix ];

      system.stateVersion = config.system.nixos.release;

      nixpkgs.pkgs = pkgs;
    };

  containerSystem =
    (import ../lib/eval-config.nix {
      system = null;
      modules = [ container ];
    }).config.system.build.toplevel;

  containerName = "container";
  containerRoot = "/var/lib/machines/${containerName}";

  containerTarball = pkgs.callPackage ../lib/make-system-tarball.nix {
    storeContents = [
      {
        object = containerSystem;
        symlink = "/nix/var/nix/profiles/system";
      }
    ];

    contents = [
      {
        source = containerSystem + "/etc/os-release";
        target = "/etc/os-release";
      }
      {
        source = containerSystem + "/init";
        target = "/sbin/init";
      }
    ];
  };
in
{
  name = "systemd-machinectl";

  nodes.machine =
    { lib, ... }:
    {
      # use networkd to obtain systemd network setup
      networking.useNetworkd = true;
      networking.useDHCP = false;

      # do not try to access cache.nixos.org
      nix.settings.substituters = lib.mkForce [ ];

      # auto-start container
      systemd.targets.machines.wants = [ "systemd-nspawn@${containerName}.service" ];

      virtualisation.additionalPaths = [
        containerSystem
        containerTarball
      ];

      systemd.tmpfiles.rules = [
        "d /var/lib/machines/shared-decl 0755 root root - -"
      ];
      systemd.nspawn.shared-decl = {
        execConfig = {
          Boot = false;
          Parameters = "${containerSystem}/init";
        };
        filesConfig = {
          BindReadOnly = "/nix/store";
        };
      };

      systemd.nspawn.${containerName} = {
        filesConfig = {
          # workaround to fix kernel namespaces; needed for Nix sandbox
          # https://github.com/systemd/systemd/issues/27994#issuecomment-1704005670
          Bind = "/proc:/run/proc";
        };
      };

      systemd.services."systemd-nspawn@${containerName}" = {
        serviceConfig.Environment = [
          # Disable tmpfs for /tmp
          "SYSTEMD_NSPAWN_TMPFS_TMP=0"

          # force unified cgroup delegation, which would be the default
          # if systemd could check the capabilities of the installed systemd.
          # see also: https://github.com/NixOS/nixpkgs/pull/198526
          "SYSTEMD_NSPAWN_UNIFIED_HIERARCHY=1"
        ];
        overrideStrategy = "asDropin";
      };

      # open DHCP for container
      networking.firewall.extraCommands = ''
        ${pkgs.iptables}/bin/iptables -A nixos-fw -i ve-+ -p udp -m udp --dport 67 -j nixos-fw-accept
      '';
    };

  testScript = ''
    start_all()
    machine.wait_for_unit("default.target");

    # Test machinectl start stop of shared-decl
    machine.succeed("machinectl start shared-decl");
    machine.wait_until_succeeds("systemctl -M shared-decl is-active default.target");
    machine.succeed("machinectl stop shared-decl");

    # create containers root
    machine.succeed("mkdir -p ${containerRoot}");

    # start container with shared nix store by using same arguments as for systemd-nspawn@.service
    machine.succeed("systemd-run systemd-nspawn --machine=${containerName} --network-veth -U --bind-ro=/nix/store ${containerSystem}/init")
    machine.wait_until_succeeds("systemctl -M ${containerName} is-active default.target");

    # Test machinectl stop
    machine.succeed("machinectl stop ${containerName}");

    # Install container
    # Workaround for nixos-install
    machine.succeed("chmod o+rx /var/lib/machines");
    machine.succeed("nixos-install --root ${containerRoot} --system ${containerSystem} --no-channel-copy --no-root-passwd");

    # Allow systemd-nspawn to apply user namespace on immutable files
    machine.succeed("chattr -i ${containerRoot}/var/empty");

    # Test machinectl start
    machine.succeed("machinectl start ${containerName}");
    machine.wait_until_succeeds("systemctl -M ${containerName} is-active default.target");

    # Test systemd-nspawn configured unified cgroup delegation
    # see also:
    # https://github.com/systemd/systemd/blob/main/docs/CGROUP_DELEGATION.md#three-different-tree-setups-
    machine.succeed('systemd-run --pty --wait -M ${containerName} /run/current-system/sw/bin/stat --format="%T" --file-system /sys/fs/cgroup > fstype')
    machine.succeed('test $(tr -d "\\r" < fstype) = cgroup2fs')

    # Test if systemd-nspawn provides a working environment for nix to build derivations
    # https://nixos.org/guides/nix-pills/07-working-derivation
    machine.succeed('systemd-run --pty --wait -M ${containerName} /run/current-system/sw/bin/nix-instantiate --expr \'derivation { name = "myname"; builder = "/bin/sh"; args = [ "-c" "echo foo > $out" ]; system = "${pkgs.system}"; }\' --add-root /tmp/drv')
    machine.succeed('systemd-run --pty --wait -M ${containerName} /run/current-system/sw/bin/nix-store --option substitute false --realize /tmp/drv')

    # Test nss_mymachines without nscd
    machine.succeed('LD_LIBRARY_PATH="/run/current-system/sw/lib" getent -s hosts:mymachines hosts ${containerName}');

    # Test nss_mymachines via nscd
    machine.succeed("getent hosts ${containerName}");

    # Test systemd-nspawn network configuration to container
    machine.succeed("networkctl --json=short status ve-${containerName} | ${pkgs.jq}/bin/jq -e '.OperationalState == \"routable\"'");

    # Test systemd-nspawn network configuration to host
    machine.succeed("machinectl shell ${containerName} /run/current-system/sw/bin/networkctl --json=short status host0 | ${pkgs.jq}/bin/jq -r '.OperationalState == \"routable\"'");

    # Test systemd-nspawn network configuration
    machine.succeed("ping -n -c 1 ${containerName}");

    # Test systemd-nspawn uses a user namespace
    machine.succeed("test $(machinectl status ${containerName} | grep 'UID Shift: ' | wc -l) = 1")

    # Test systemd-nspawn reboot
    machine.succeed("machinectl shell ${containerName} /run/current-system/sw/bin/reboot");
    machine.wait_until_succeeds("systemctl -M ${containerName} is-active default.target");

    # Test machinectl reboot
    machine.succeed("machinectl reboot ${containerName}");
    machine.wait_until_succeeds("systemctl -M ${containerName} is-active default.target");

    # Restart machine
    machine.shutdown()
    machine.start()
    machine.wait_for_unit("default.target");

    # Test auto-start
    machine.succeed("machinectl show ${containerName}")

    # Test machinectl stop
    machine.succeed("machinectl stop ${containerName}");
    machine.wait_until_succeeds("test $(systemctl is-active systemd-nspawn@${containerName}) = inactive");

    # Test tmpfs for /tmp
    machine.fail("mountpoint /tmp");

    # Show to to delete the container
    machine.succeed("chattr -i ${containerRoot}/var/empty");
    machine.succeed("rm -rf ${containerRoot}");

    # Test import tarball, start, stop and remove
    machine.succeed("machinectl import-tar ${containerTarball}/tarball/*.tar* ${containerName}");
    machine.succeed("machinectl start ${containerName}");
    machine.wait_until_succeeds("systemctl -M ${containerName} is-active default.target");
    machine.succeed("machinectl stop ${containerName}");
    machine.wait_until_succeeds("test $(systemctl is-active systemd-nspawn@${containerName}) = inactive");
    machine.succeed("machinectl remove ${containerName}");
  '';
}
