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

with lib;

let
  cfg = config.services.boinc;
  allowRemoteGuiRpcFlag = optionalString cfg.allowRemoteGuiRpc "--allow_remote_gui_rpc";

  fhsEnv = pkgs.buildFHSUserEnv {
    name = "boinc-fhs-env";
    targetPkgs = pkgs': [ cfg.package ] ++ cfg.extraEnvPackages;
    runScript = "/bin/boinc_client";
  };
  fhsEnvExecutable = "${fhsEnv}/bin/${fhsEnv.name}";

in
  {
    options.services.boinc = {
      enable = mkOption {
        type = types.bool;
        default = false;
        description = lib.mdDoc ''
          Whether to enable the BOINC distributed computing client. If this
          option is set to true, the boinc_client daemon will be run as a
          background service. The boinccmd command can be used to control the
          daemon.
        '';
      };

      package = mkOption {
        type = types.package;
        default = pkgs.boinc;
        defaultText = literalExpression "pkgs.boinc";
        description = lib.mdDoc ''
          Which BOINC package to use.
        '';
      };

      dataDir = mkOption {
        type = types.path;
        default = "/var/lib/boinc";
        description = lib.mdDoc ''
          The directory in which to store BOINC's configuration and data files.
        '';
      };

      allowRemoteGuiRpc = mkOption {
        type = types.bool;
        default = false;
        description = lib.mdDoc ''
          If set to true, any remote host can connect to and control this BOINC
          client (subject to password authentication). If instead set to false,
          only the hosts listed in {var}`dataDir`/remote_hosts.cfg will be allowed to
          connect.

          See also: <http://boinc.berkeley.edu/wiki/Controlling_BOINC_remotely#Remote_access>
        '';
      };

      extraEnvPackages = mkOption {
        type = types.listOf types.package;
        default = [];
        example = literalExpression "[ pkgs.virtualbox ]";
        description = lib.mdDoc ''
          Additional packages to make available in the environment in which
          BOINC will run. Common choices are:

          - {var}`pkgs.virtualbox`:
            The VirtualBox virtual machine framework. Required by some BOINC
            projects, such as ATLAS@home.
          - {var}`pkgs.ocl-icd`:
            OpenCL infrastructure library. Required by BOINC projects that
            use OpenCL, in addition to a device-specific OpenCL driver.
          - {var}`pkgs.linuxPackages.nvidia_x11`:
            Provides CUDA libraries. Required by BOINC projects that use
            CUDA. Note that this requires an NVIDIA graphics device to be
            present on the system.

            Also provides OpenCL drivers for NVIDIA GPUs;
            {var}`pkgs.ocl-icd` is also needed in this case.
        '';
      };
    };

    config = mkIf cfg.enable {
      environment.systemPackages = [cfg.package];

      users.users.boinc = {
        group = "boinc";
        createHome = false;
        description = "BOINC Client";
        home = cfg.dataDir;
        isSystemUser = true;
      };
      users.groups.boinc = {};

      systemd.tmpfiles.rules = [
        "d '${cfg.dataDir}' - boinc boinc - -"
      ];

      systemd.services.boinc = {
        description = "BOINC Client";
        after = ["network.target"];
        wantedBy = ["multi-user.target"];
        script = ''
          ${fhsEnvExecutable} --dir ${cfg.dataDir} ${allowRemoteGuiRpcFlag}
        '';
        serviceConfig = {
          User = "boinc";
          Nice = 10;
        };
      };
    };

    meta = {
      maintainers = with lib.maintainers; [kierdavis];
    };
  }