{ config, lib, ... }:

with lib;

{
  ###### interface

  options = {

    hardware.trackpoint = {

      enable = mkOption {
        default = false;
        type = types.bool;
        description = ''
          Enable sensitivity and speed configuration for trackpoints.
        '';
      };

      sensitivity = mkOption {
        default = 128;
        example = 255;
        type = types.int;
        description = ''
          Configure the trackpoint sensitivity. By default, the kernel
          configures 128.
        '';
      };

      speed = mkOption {
        default = 97;
        example = 255;
        type = types.int;
        description = ''
          Configure the trackpoint speed. By default, the kernel
          configures 97.
        '';
      };

      emulateWheel = mkOption {
        default = false;
        type = types.bool;
        description = ''
          Enable scrolling while holding the middle mouse button.
        '';
      };

      fakeButtons = mkOption {
        default = false;
        type = types.bool;
        description = ''
          Switch to "bare" PS/2 mouse support in case Trackpoint buttons are not recognized
          properly. This can happen for example on models like the L430, T450, T450s, on
          which the Trackpoint buttons are actually a part of the Synaptics touchpad.
        '';
      };

      device = mkOption {
        default = "TPPS/2 IBM TrackPoint";
        type = types.str;
        description = ''
          The device name of the trackpoint. You can check with xinput.
          Some newer devices (example x1c6) use "TPPS/2 Elan TrackPoint".
        '';
      };

    };

  };

  ###### implementation

  config =
    let
      cfg = config.hardware.trackpoint;
    in
    mkMerge [
      (mkIf cfg.enable {
        services.udev.extraRules = ''
          ACTION=="add|change", SUBSYSTEM=="input", ATTR{name}=="${cfg.device}", ATTR{device/speed}="${toString cfg.speed}", ATTR{device/sensitivity}="${toString cfg.sensitivity}"
        '';

        systemd.services.trackpoint = {
          wantedBy = [ "sysinit.target" ];
          before = [
            "sysinit.target"
            "shutdown.target"
          ];
          conflicts = [ "shutdown.target" ];
          unitConfig.DefaultDependencies = false;
          serviceConfig.Type = "oneshot";
          serviceConfig.RemainAfterExit = true;
          serviceConfig.ExecStart = ''
            ${config.systemd.package}/bin/udevadm trigger --attr-match=name="${cfg.device}"
          '';
        };
      })

      (mkIf (cfg.emulateWheel) {
        services.xserver.inputClassSections = [
          ''
            Identifier "Trackpoint Wheel Emulation"
            MatchProduct "${
              if cfg.fakeButtons then
                "PS/2 Generic Mouse"
              else
                "ETPS/2 Elantech TrackPoint|Elantech PS/2 TrackPoint|TPPS/2 IBM TrackPoint|DualPoint Stick|Synaptics Inc. Composite TouchPad / TrackPoint|ThinkPad USB Keyboard with TrackPoint|USB Trackpoint pointing device|Composite TouchPad / TrackPoint|${cfg.device}"
            }"
            MatchDevicePath "/dev/input/event*"
            Option "EmulateWheel" "true"
            Option "EmulateWheelButton" "2"
            Option "Emulate3Buttons" "false"
            Option "XAxisMapping" "6 7"
            Option "YAxisMapping" "4 5"
          ''
        ];
      })

      (mkIf cfg.fakeButtons {
        boot.extraModprobeConfig = "options psmouse proto=bare";
      })
    ];
}
