nix-gc: init service

default.nix

@@ -40,6 +40,7 @@ let
         ./modules/services/kwm.nix
         ./modules/services/emacs.nix
         ./modules/services/nix-daemon.nix
+        ./modules/services/nix-gc.nix
         ./modules/programs/bash.nix
         ./modules/programs/fish.nix
         ./modules/programs/nix-script.nix

modules/services/nix-gc.nix

@@ -0,0 +1,55 @@
+{ config, lib, pkgs, ... }:
+
+with lib;
+
+let
+  cfg = config.nix.gc;
+in
+
+{
+  options = {
+    nix.gc = {
+
+      automatic = mkOption {
+        default = false;
+        type = types.bool;
+        description = "Automatically run the garbage collector at a specific time.";
+      };
+
+      # TODO: parse dates
+      # dates = mkOption {
+      #   default = "03:15";
+      #   type = types.str;
+      #   description = ''
+      #     Specification (in the format described by
+      #     <citerefentry><refentrytitle>systemd.time</refentrytitle>
+      #     <manvolnum>5</manvolnum></citerefentry>) of the time at
+      #     which the garbage collector will run.
+      #   '';
+      # };
+
+      options = mkOption {
+        default = "";
+        example = "--max-freed $((64 * 1024**3))";
+        type = types.str;
+        description = ''
+          Options given to <filename>nix-collect-garbage</filename> when the
+          garbage collector is run automatically.
+        '';
+      };
+
+    };
+  };
+
+  config = mkIf cfg.automatic {
+
+    launchd.daemons.nix-gc = {
+      command = "${config.nix.package}/bin/nix-collect-garbage ${cfg.options}";
+      serviceConfig.RunAtLoad = false;
+      serviceConfig.StartCalendarInterval = mkDefault
+        [ { Hour = 3; Minute = 15; }
+        ];
+    };
+
+  };
+}