plasma-manager/modules/widgets/system-monitor.nix

{ lib, ... }:
let
  inherit (lib) mkOption types;

  # KDE expects a key/value pair like this:
  # ```ini
  # highPrioritySensorIds=["cpu/all/usage", "cpu/all/averageTemperature"]
  # ```
  #
  # Which is **different** to what would happen if you pass a list of strings to the JS script:
  # ```ini
  # highPrioritySensorIds=cpu/all/usage,cpu/all/averageTemperature
  # ```
  #
  # So, to satisfy the expected format we must quote the ENTIRE string as a valid JS string,
  # which means constructing a string that looks like this in the source code:
  # "[\"cpu/all/usage\", \"cpu/all/averageTemperature\"]"
  toEscapedList = ids:
    if ids != null
    then "[${lib.concatMapStringsSep ", " (x: ''\"${x}\"'') ids}]"
    else null;

  mkListOption = mkOption {
    type = with types; nullOr (listOf str);
    default = null;
    apply = toEscapedList;
  };

  # {name, color} -> {name, value}
  # Convert the sensor attrset into a name-value pair expected by listToAttrs
  toColorKV =
    { name
    , color
    , label
    ,
    }: {
      inherit name;
      value = color;
    };
  toLabelKV =
    { name
    , color
    , label
    ,
    }: {
      inherit name;
      value = label;
    };
in
{
  systemMonitor = {
    description = "A system monitor widget.";

    opts = {
      # See https://invent.kde.org/plasma/plasma-workspace/-/blob/master/applets/systemmonitor/systemmonitor/package/contents/config/main.xml for the accepted raw options 

      title = mkOption {
        type = with types; nullOr str;
        default = null;
        description = "The title of this system monitor.";
      };
      showTitle = mkOption {
        type = with types; nullOr bool;
        default = null;
        description = "Show or hide the title.";
      };
      showLegend = mkOption {
        type = with types; nullOr bool;
        default = null;
        description = "Show or hide the legend.";
      };
      displayStyle = mkOption {
        type = with types; nullOr str;
        default = null;
        example = "org.kde.ksysguard.barchart";
        description = "The display style of the chart. Uses the internal plugin name.";
      };
      sensors = mkOption {
        type = with types;
          nullOr (listOf (submodule {
            options = {
              name = mkOption {
                type = str;
                example = "cpu/all/usage";
                description = "The name of the sensor.";
              };
              color = mkOption {
                type = str; # TODO maybe use a better type
                example = "255,255,255";
                description = "The color of the sensor, as a string containing 8-bit integral RGB values separated by commas";
              };
              label = mkOption {
                type = str;
                example = "CPU %";
                description = "The label of the sensor.";
              };
            };
          }));
        default = null;
        example = [{
          name = "gpu/gpu1/usage";
          color = "180,190,254";
          label = "GPU %";
        }];
        description = ''
          The list of sensors displayed as a part of the graph/chart.
        '';
        apply = sensors: lib.optionalAttrs (sensors != null) {
          SensorColors = builtins.listToAttrs (map toColorKV sensors);
          SensorLabels = builtins.listToAttrs (map toLabelKV sensors);
          Sensors.highPrioritySensorIds = toEscapedList (map (s: s.name) sensors);
        };
      };

      totalSensors = mkListOption // {
        example = [ "cpu/all/usage" ];
        description = ''
          The list of "total sensors" displayed on top of the graph/chart.
        '';
      };
      textOnlySensors = mkListOption // {
        example = [ "cpu/all/averageTemperature" "cpu/all/averageFrequency" ];
        description = ''
          The list of text-only sensors, displayed in the pop-up upon clicking the widget.
        '';
      };
      range = {
        from = mkOption {
          type = with lib.types; nullOr (ints.between 0 100);
          default = null;
          description = "The lower range the sensors can take.";
        };
        to = mkOption {
          type = with lib.types; nullOr (ints.between 0 100);
          default = null;
          description = "The upper range the sensors can take.";
        };
      };
    };

    convert =
      { title
      , showTitle
      , showLegend
      , displayStyle
      , totalSensors
      , sensors
      , textOnlySensors
      , range
      }: {
        name = "org.kde.plasma.systemmonitor";
        config = lib.filterAttrsRecursive (_: v: v != null)
          (lib.recursiveUpdate
            ({
              Appearance = {
                inherit title;
                inherit showTitle;
                chartFace = displayStyle;
              };
              Sensors = {
                lowPrioritySensorIds = textOnlySensors;
                totalSensors = totalSensors;
              };
              "org.kde.ksysguard.piechart/General" = {
                inherit showLegend;
                rangeAuto = (range.from == null && range.to == null);
                rangeFrom = range.from;
                rangeTo = range.to;
              };
            })
            sensors);
      };
  };
}