dunst: implement settings parameter

modules/services/dunst.nix

@@ -2,6 +2,22 @@
 
 with lib;
 
+let
+
+  cfg = config.services.dunst;
+  toDunstIni = generators.toINI {
+    mkKeyValue = key: value:
+    let
+      value' =
+        if isBool value then (if value then "yes" else "no")
+        else if isString value then "\"${value}\""
+        else toString value;
+    in
+      "${key}=${value'}";
+  };
+
+in
+
 {
   meta.maintainers = [ maintainers.rycee ];
 
@@ -10,14 +26,32 @@ with lib;
       enable = mkEnableOption "the dunst notification daemon";
 
       settings = mkOption {
-        type = types.attrs;
+        type = types.attrsOf types.attrs;
         default = {};
         description = "Configuration written to ~/.config/dunstrc";
+        example = literalExample ''
+          {
+            global = {
+              geometry = "300x5-30+50";
+              transparency = 10;
+              frame_color = "#eceff1";
+              font = "Droid Sans 9";
+            };
+
+            urgency_normal = {
+              background = "#37474f";
+              foreground = "#eceff1";
+              timeout = 10;
+            };
+          };
+        '';
       };
     };
   };
 
-  config = mkIf config.services.dunst.enable {
+  config = mkIf cfg.enable (
+    mkMerge [
+      {
         home.file.".local/share/dbus-1/services/org.knopwob.dunst.service".source =
           "${pkgs.dunst}/share/dbus-1/services/org.knopwob.dunst.service";
 
@@ -34,5 +68,11 @@ with lib;
             ExecStart = "${pkgs.dunst}/bin/dunst";
           };
         };
-  };
+      }
+
+      (mkIf (cfg.settings != {}) {
+        home.file.".config/dunst/dunstrc".text = toDunstIni cfg.settings;
+      })
+    ]
+  );
 }