Added battery notify (currently don't work)

I'm fighting with udev to get it work properly.

modules/system/power.nix

@@ -13,6 +13,6 @@ in with lib; {
     powerManagement.powertop.enable = true;
     services.upower.enable = true;
 
-    environment.systemPackages = with pkgs; [ powertop ];
+    environment.systemPackages = with pkgs; [ powertop tpacpi-bat ];
   };
 }

pkgs/battery-notify.nix

@@ -0,0 +1,58 @@
+{ pkgs, ... }:
+let
+  xpub = pkgs.fetchurl {
+    url =
+      "https://raw.githubusercontent.com/Ventto/xpub/f2eadaaf9c8539abbd46b23c0b2f6d93d2ebd658/src/xpub.sh";
+    sha256 = "sha256-88t9lr6DxrWrg6E4YsWGzYV9/GbRgwLafAklXHObqsI=";
+    executable = true;
+  };
+in pkgs.writeShellScriptBin "battery-notify" ''
+  #!${pkgs.bash}/bin/bash
+
+  # ''${DISPLAY:=":0"}
+  #: $\{XUSER:=":james"\}
+
+  touch /tmp/battery-notify
+  echo "display:$DISPLAY" >> /tmp/battery-notify
+  echo "tty:$TTY" >> /tmp/battery-notify
+  echo "XUSER:$XUSER" >> /tmp/battery-notify
+  echo "DBUS_SESSION_BUS_ADDRESS:$DBUS_SESSION_BUS_ADDRESS" >> /tmp/battery-notify
+
+  export $(${xpub}) ;
+  function last_chance {
+      if [ -f /tmp/last_chance ] ; then
+          echo "There already exist another processing doing this. Aborting."
+          exit
+      else
+          ${pkgs.coreutils}/bin/touch /tmp/last_chance
+      fi
+
+      countdown=30
+      while [[ $(${pkgs.coreutils}/bin/cat /sys/class/power_supply/AC/online) -eq 0 ]] ; do
+          if [[ countdown -gt 0 ]] ; then
+              ${pkgs.libnotify}/bin/notify-send -h string:x-canonical-private-synchronous:battery -u critical " Critical Battery - Suspension imminent." "You have $countdown seconds." ; sleep 1
+              let "countdown=countdown-1"
+          else
+              ${pkgs.libnotify}/bin/notify-send -h string:x-canonical-private-synchronous:battery -u low " Critical Battery" "PlaceHolder"
+              break;
+          fi
+      done
+
+      ${pkgs.coreutils}/bin/rm /tmp/last_chance
+  }
+
+  case $1 in
+      charging)
+          ${pkgs.libnotify}/bin/notify-send -h string:x-canonical-private-synchronous:battery -u low " Power Connected" "Battery at $(${pkgs.coreutils}/bin/cat /sys/class/power_supply/BAT0/capacity)%";;
+      discharging)
+          ${pkgs.libnotify}/bin/notify-send -h string:x-canonical-private-synchronous:battery -u low " Power Disconnected" "Battery at $(${pkgs.coreutils}/bin/cat /sys/class/power_supply/BAT0/capacity)%";;
+      warn)
+          ${pkgs.libnotify}/bin/notify-send -h string:x-canonical-private-synchronous:battery -u normal " Discharging" "Battery at $(${pkgs.coreutils}/bin/cat /sys/class/power_supply/BAT0/capacity)%";;
+      danger)
+          ${pkgs.libnotify}/bin/notify-send -h string:x-canonical-private-synchronous:battery -u critical " Low Battery" "Battery at $(${pkgs.coreutils}/bin/cat /sys/class/power_supply/BAT0/capacity)%. Will suspend soon.";;
+      ohfuck)
+          last_chance ;;
+      *)
+            echo "invalid command" ;;
+  esac
+''

pkgs/default.nix

@@ -1,5 +1,6 @@
 self: super: {
   brightness-sh = super.callPackage ./brightness.nix { inherit super; };
+  battery-notify = super.callPackage ./battery-notify.nix { inherit super; };
   sway-entry = super.callPackage ./sway-entry.nix { inherit super; };
   volume-sh = super.callPackage ./volume.nix { inherit super; };
 }