Migrate to snowfall lib

modules/nixos/system/hw/power/default.nix

@@ -0,0 +1,42 @@
+{ lib, config, pkgs, ... }:
+let cfg = config.hostcfg.make.power;
+in {
+  config = lib.mkIf cfg {
+    services.tlp = {
+      enable = true;
+      settings = {
+        START_CHARGE_THRESH_BAT0 = 75;
+        STOP_CHARGE_THRESH_BAT0 = 90;
+        CPU_SCALING_GOVERNOR_ON_AC = "performance";
+        CPU_SCALING_GOVERNOR_ON_BAT = "powersave";
+      };
+    };
+
+    systemd.user.services.battery_monitor = {
+      wants = [ "display-manager.service" ];
+      wantedBy = [ "graphical-session.target" ];
+      script = ''
+        prev_val=100
+        check () { [[ $1 -ge $val ]] && [[ $1 -lt $prev_val ]]; }
+        notify () {
+        ${pkgs.libnotify}/bin/notify-send -a Battery "$@" \
+            -h "int:value:$val" "Discharging" "$val%, $remaining"
+        }
+        while true; do
+        IFS=: read _ bat0 < <(${pkgs.acpi}/bin/acpi -b)
+        IFS=\ , read status val remaining <<<"$bat0"
+        val=''${val%\%}
+        if [[ $status = Discharging ]]; then
+            echo "$val%, $remaining"
+            if check 30 || check 25 || check 20; then notify
+            elif check 15 || [[ $val -le 10 ]]; then notify -u critical
+            fi
+        fi
+        prev_val=$val
+        # Sleep longer when battery is high to save CPU
+        if [[ $val -gt 30 ]]; then sleep 10m; elif [[ $val -ge 20 ]]; then sleep 5m; else sleep 1m; fi
+        done
+      '';
+    };
+  };
+}