Nomarchy/modules/nixos/power.nix

# Active power management. One concern, one file: this is the system
# side — the power daemon (power-profiles-daemon by default, or TLP),
# thermald, and the battery charge limit. The profile *switcher* and the
# Waybar *indicator* live home-side (rofi.nix / waybar.nix); they self-
# gate on powerprofilesctl being present, so there's no system→home wiring
# to keep in sync (the same way the Waybar battery widget auto-hides on
# desktops). See the roadmap in README.md.
{ config, lib, pkgs, ... }:

let
  cfg = config.nomarchy.system.power;
  ppd = cfg.backend == "ppd";
  tlp = cfg.backend == "tlp";
in
{
  config = lib.mkIf cfg.enable {
    # PPD and TLP both drive CPU/platform power — running both fights.
    # `backend` selects exactly one; this assertion only fires if a
    # downstream force-enables the other service directly.
    assertions = [{
      assertion = !(config.services.power-profiles-daemon.enable
        && config.services.tlp.enable);
      message = ''
        nomarchy: power-profiles-daemon and TLP are mutually exclusive.
        Pick one with nomarchy.system.power.backend ("ppd" or "tlp").
      '';
    }];

    # Unprivileged profile switching (the menu/Waybar) goes through
    # polkit, already enabled distro-wide in default.nix.
    services.power-profiles-daemon.enable = lib.mkDefault ppd;
    services.tlp.enable = lib.mkDefault tlp;

    # thermald is Intel-only, so off unless asked (the installer enables
    # it on a GenuineIntel CPU). Sits happily next to either backend.
    services.thermald.enable = lib.mkDefault cfg.thermal.enable;

    # Battery charge limit via sysfs. PPD can't cap charge at all, and
    # TLP's own knob only applies under TLP — so a tiny oneshot writes
    # the threshold directly, independent of the backend. Re-applied on
    # AC state changes by the udev rule below (some firmwares reset the
    # threshold when the charger is unplugged).
    #
    # Instant menu path (user decision 2026-07-10): the threshold node is
    # group-writable for `users` so nomarchy-menu can echo live without
    # rebuild; this oneshot still owns boot + AC-replug re-apply. Prefer
    # live theme-state.json under /home/*/.nomarchy so a menu change
    # survives reboot before the next sys-rebuild bakes the Nix option.
    systemd.services.nomarchy-battery-charge-limit = lib.mkIf cfg.laptop {
      description = "Apply battery charge end threshold from state or config";
      wantedBy = [ "multi-user.target" ];
      path = [ pkgs.jq pkgs.coreutils ];
      serviceConfig = {
        Type = "oneshot";
        RemainAfterExit = true;
      };
      script = ''
        set -euo pipefail
        # Baked generation default (empty = full charge / no cap).
        limit=${if cfg.batteryChargeLimit != null then toString cfg.batteryChargeLimit else ""}
        # Prefer the newest live state write (menu path, no rebuild yet).
        for st in /home/*/.nomarchy/theme-state.json; do
          [ -r "$st" ] || continue
          v=$(jq -r '.settings.power.batteryChargeLimit // empty' "$st" 2>/dev/null || true)
          case "$v" in
            ""|null|Null) ;;
            *[!0-9]*) ;;
            *) limit=$v ;;
          esac
        done
        [ -n "$limit" ] || limit=100
        # Name-agnostic system batteries (BACKLOG #60).
        for d in /sys/class/power_supply/*/; do
          [ "$(cat "$d/type" 2>/dev/null)" = Battery ] || continue
          [ "$(cat "$d/scope" 2>/dev/null || echo System)" = Device ] && continue
          thresh="$d/charge_control_end_threshold"
          [ -e "$thresh" ] || continue
          # Keep the node group-writable for the menu's live path (udev
          # sets this on add; re-assert after firmware recreates attrs).
          chgrp users "$thresh" 2>/dev/null || true
          chmod 0664 "$thresh" 2>/dev/null || true
          # Some firmwares (Dell) reset the threshold on unplug *after*
          # the udev event — write once, wait, write again.
          echo "$limit" > "$thresh" 2>/dev/null || true
          sleep 1
          echo "$limit" > "$thresh" 2>/dev/null || true
        done
        exit 0
      '';
    };

    # Writable threshold for the logged-in user (menu live apply) + AC
    # re-apply of the oneshot. Laptop only; no-op when the attr is absent.
    # Immediate + delayed restart: Dell/Latitude firmware often stomps the
    # threshold to 100 right after unplug; a single immediate oneshot
    # loses the race (hardware: unplug→100, plug→80). systemd-run hands
    # the delayed restart off so udev's short RUN budget is not held.
    services.udev.extraRules = lib.mkIf cfg.laptop (
      let
        systemctl = "${config.systemd.package}/bin/systemctl";
        systemdRun = "${config.systemd.package}/bin/systemd-run";
      in ''
        SUBSYSTEM=="power_supply", ATTR{type}=="Battery", TEST=="charge_control_end_threshold", GROUP="users", MODE="0664"
        SUBSYSTEM=="power_supply", ATTR{type}=="Mains", RUN+="${systemctl} --no-block restart nomarchy-battery-charge-limit.service"
        SUBSYSTEM=="power_supply", ATTR{type}=="Mains", RUN+="${systemdRun} --no-block --collect --on-active=2s --timer-property=AccuracySec=200ms ${systemctl} --no-block restart nomarchy-battery-charge-limit.service"
      ''
    );

    # Unprivileged restart of the oneshot so the menu can re-apply as
    # root when the threshold node is not (yet) user-writable.
    security.polkit.extraConfig = lib.mkIf cfg.laptop ''
      polkit.addRule(function(action, subject) {
          if (action.id == "org.freedesktop.systemd1.manage-units" &&
              subject.isInGroup("users")) {
              var unit = action.lookup("unit");
              if (unit == "nomarchy-battery-charge-limit.service") {
                  return polkit.Result.YES;
              }
          }
      });
    '';
  };
}