nixos/modules/laptop/battery.nix

{ config, lib, ... }:

let
  inherit (lib) mkOption types;

  singleBat = {
    START_CHARGE_THRESH_BAT0 = 65;
    STOP_CHARGE_THRESH_BAT0 = 85;
  };

  doubleBat = singleBat // {
    START_CHARGE_THRESH_BAT1 = 65;
    STOP_CHARGE_THRESH_BAT1 = 85;
  };

in {
  options.batMode = mkOption {
    type = types.enum [ "single" "double" ];
    default = "single";
  };

  config = {
    powerManagement.powertop.enable = true;

    services.upower = {
      enable = true;

      # In accordance with waybar battery colors
      percentageLow = 30;
      percentageCritical = 20;
      percentageAction = 15;

      criticalPowerAction = "PowerOff"; # This can destroy work
      usePercentageForPolicy = true;
    };

    services.tlp = {
      enable = true;
      settings = if config.batMode == "single" then singleBat else doubleBat;
    };
  };
}