home/modules: add automation for direnv

home/home.nix

@@ -52,6 +52,7 @@ in {
     ./modules/programs/gpg
     ./modules/programs/neovim/auto-clean-swapfiles.nix
     ./modules/programs/nix-index/auto-update-database.nix
+    ./modules/programs/direnv/auto-prune.nix
   ] ++ (optionals graphics [
     ./config/gtk.nix
 

home/modules/programs/direnv/auto-prune.nix

@@ -0,0 +1,51 @@
+{ config, pkgs, lib, ... }:
+let
+  cfg = config.programs.direnv;
+in
+{
+  options.programs.direnv.auto-prune-allowed-dirs = {
+    enable = lib.mkEnableOption "automatic pruning of direnv dirs";
+
+    onCalendar = lib.mkOption {
+      type = lib.types.str;
+      default = "daily";
+      example = "weekly";
+      # TODO: link to systemd manpage for format.
+      description = "How often to prune dirs.";
+    };
+  };
+
+  config = lib.mkIf cfg.auto-prune-allowed-dirs.enable {
+    systemd.user.services.direnv-auto-prune-allowed-dirs = {
+      Unit = {
+        Description = "Prune unused allowed directories for direnv";
+        Documentation = [ "man:direnv(1)" ];
+        ConditionPathExists = "${config.xdg.dataHome}/direnv/allow";
+      };
+
+      Service = {
+        Type = "oneshot";
+        CPUSchedulingPolicy = "idle";
+        IOSchedulingClass = "idle";
+        ExecStart = "${lib.getExe cfg.package} prune";
+      };
+    };
+
+    systemd.user.timers.direnv-auto-prune-allowed-dirs = {
+      Unit = {
+        Description = "Prune unused allowed directories for direnv";
+        Documentation = [ "man:direnv(1)" ];
+      };
+
+      Timer = {
+        Unit = "direnv-auto-prune-allowed-dirs.service";
+        OnCalendar = cfg.auto-prune-allowed-dirs.onCalendar;
+        Persistent = true;
+      };
+
+      Install = {
+        WantedBy = [ "timers.target" ];
+      };
+    };
+  };
+}

home/programs/direnv/default.nix

@@ -1,13 +1,11 @@
 { config, ... }:
 {
-  imports = [
-    ./auto-prune.nix
-  ];
-
   programs.direnv = {
     enable = true;
     enableZshIntegration = true;
     nix-direnv.enable = true;
     enableNushellIntegration = config.programs.nushell.enable;
+
+    auto-prune-allowed-dirs.enable = true;
   };
 }