{ config, lib, pkgs, ... }:

with lib;

let
  cfg = config.services.virtualboxHost;
  virtualbox = config.boot.kernelPackages.virtualbox.override {
    inherit (cfg) enableHardening;
  };

in

{
  options.services.virtualboxHost = {
    enable = mkOption {
      type = types.bool;
      default = false;
      description = ''
        Whether to enable host-side support for VirtualBox.

        <note><para>
          In order to pass USB devices from the host to the guests, the user
          needs to be in the <literal>vboxusers</literal> group.
        </para></note>
      '';
    };

    addNetworkInterface = mkOption {
      type = types.bool;
      default = true;
      description = ''
        Automatically set up a vboxnet0 host-only network interface.
      '';
    };

    enableHardening = mkOption {
      type = types.bool;
      default = false;
      description = ''
        Enable hardened VirtualBox, which ensures that only the binaries in the
        system path get access to the devices exposed by the kernel modules
        instead of all users in the vboxusers group.

        <important><para>
          Disabling this can put your system's security at risk, as local users
          in the vboxusers group can tamper with the VirtualBox device files.
        </para></important>
      '';
    };
  };

  config = mkIf cfg.enable (mkMerge [{
    boot.kernelModules = [ "vboxdrv" "vboxnetadp" "vboxnetflt" ];
    boot.extraModulePackages = [ virtualbox ];
    environment.systemPackages = [ virtualbox ];

    warnings = mkIf (!cfg.enableHardening) (singleton (
      "Hardening is currently disabled for VirtualBox, because of some " +
      "issues in conjunction with host-only-interfaces. If you don't use " +
      "hostonlyifs, it's strongly recommended to set " +
      "`services.virtualboxHost.enableHardening = true'!"
    ));

    security.setuidOwners = let
      mkSuid = program: {
        inherit program;
        source = "${virtualbox}/libexec/virtualbox/${program}";
        owner = "root";
        group = "vboxusers";
        setuid = true;
      };
    in mkIf cfg.enableHardening (map mkSuid [
      "VBoxHeadless"
      "VBoxNetAdpCtl"
      "VBoxNetDHCP"
      "VBoxNetNAT"
      "VBoxSDL"
      "VBoxVolInfo"
      "VirtualBox"
    ]);

    users.extraGroups.vboxusers.gid = config.ids.gids.vboxusers;

    services.udev.extraRules =
      ''
        KERNEL=="vboxdrv",    OWNER="root", GROUP="vboxusers", MODE="0660", TAG+="systemd"
        KERNEL=="vboxdrvu",   OWNER="root", GROUP="root",      MODE="0666", TAG+="systemd"
        KERNEL=="vboxnetctl", OWNER="root", GROUP="vboxusers", MODE="0660", TAG+="systemd"
        SUBSYSTEM=="usb_device", ACTION=="add", RUN+="${virtualbox}/libexec/virtualbox/VBoxCreateUSBNode.sh $major $minor $attr{bDeviceClass}"
        SUBSYSTEM=="usb", ACTION=="add", ENV{DEVTYPE}=="usb_device", RUN+="${virtualbox}/libexec/virtualbox/VBoxCreateUSBNode.sh $major $minor $attr{bDeviceClass}"
        SUBSYSTEM=="usb_device", ACTION=="remove", RUN+="${virtualbox}/libexec/virtualbox/VBoxCreateUSBNode.sh --remove $major $minor"
        SUBSYSTEM=="usb", ACTION=="remove", ENV{DEVTYPE}=="usb_device", RUN+="${virtualbox}/libexec/virtualbox/VBoxCreateUSBNode.sh --remove $major $minor"
      '';

    # Since we lack the right setuid binaries, set up a host-only network by default.
  } (mkIf cfg.addNetworkInterface {
    systemd.services."vboxnet0" =
      { description = "VirtualBox vboxnet0 Interface";
        requires = [ "dev-vboxnetctl.device" ];
        after = [ "dev-vboxnetctl.device" ];
        wantedBy = [ "network.target" "sys-subsystem-net-devices-vboxnet0.device" ];
        path = [ virtualbox ];
        serviceConfig.RemainAfterExit = true;
        serviceConfig.Type = "oneshot";
        serviceConfig.PrivateTmp = true;
        environment.VBOX_USER_HOME = "/tmp";
        script =
          ''
            if ! [ -e /sys/class/net/vboxnet0 ]; then
              VBoxManage hostonlyif create
              cat /tmp/VBoxSVC.log >&2
            fi
          '';
        postStop =
          ''
            VBoxManage hostonlyif remove vboxnet0
          '';
      };

    networking.interfaces.vboxnet0.ip4 = [ { address = "192.168.56.1"; prefixLength = 24; } ];
  })]);
}