system/services/greetd: remove cage and use niri for greeter

hosts/default.nix

@@ -9,9 +9,7 @@ in {
     system = "x86_64-linux";
     modules = [
       ./vamos
-
       inputs.self.nixosModules.theme
-
       inputs.nixos-hardware.nixosModules.framework-13-7040-amd
     ];
   };

system/services/greetd.nix

@@ -1,23 +1,80 @@
 {
+  inputs,
+  config,
   lib,
   pkgs,
-  config,
   ...
-}: {
-  services.greetd = {
+}: let
+  inherit (lib) getExe evalModules;
+  inherit (inputs) niri;
+in {
+  services.greetd = let
+    home-config = config.home-manager.users.nezia;
+    # huge thanks to https://github.com/sodiboo/system/blob/262e7e80ac9ae0511f8565713feaa8315d084025/login.mod.nix#L22-L67
+    # this is needed because we are also importing the default settings
+    niri-cfg-modules = evalModules {
+      modules = [
+        niri.lib.internal.settings-module
+        (let
+          cfg = home-config.programs.niri.settings;
+        in {
+          programs.niri.settings = {
+            inherit (cfg) input outputs layout;
+            hotkey-overlay.skip-at-startup = true;
+            # causes a deprecation warning otherwise
+            cursor = builtins.removeAttrs cfg.cursor ["hide-on-key-press"];
+
+            window-rules = [
+              {
+                draw-border-with-background = false;
+                clip-to-geometry = true;
+                geometry-corner-radius = {
+                  top-left = 8.0;
+                  top-right = 8.0;
+                  bottom-left = 8.0;
+                  bottom-right = 8.0;
+                };
+              }
+            ];
+          };
+        })
+      ];
+    };
+
+    # validates config and creates a derivation
+    niri-config = niri.lib.internal.validated-config-for pkgs config.programs.niri.package niri-cfg-modules.config.programs.niri.finalConfig;
+  in {
     enable = true;
-    settings = rec {
-      initial_session = {
-        command = ''
-          ${lib.getExe pkgs.greetd.tuigreet}
-            --time
-            --asterisks
-            --user-menu
-            --cmd ${lib.getExe config.programs.niri.package} --session
-        '';
+    settings = {
+      default_session = let
+        niri = getExe config.programs.niri.package;
+        regreet = getExe config.programs.regreet.package;
+      in {
+        # TODO: kill niri after logging in so we don't have to wait for greetd to do it (can get pretty long)
+        command = "${niri} -c ${niri-config} -- ${regreet}";
         user = "greeter";
       };
-      default_session = initial_session;
+    };
+  };
+  programs.regreet = {
+    enable = true;
+    theme = {
+      inherit (config.theme.gtk.theme) name package;
+    };
+    iconTheme = {
+      inherit (config.theme.gtk.iconTheme) name package;
+    };
+    cursorTheme = {
+      inherit (config.theme.cursorTheme) name package;
+    };
+    settings = {
+      background = {
+        path = config.theme.wallpaper;
+        fit = "Fill";
+      };
+      GTK = {
+        application_prefer_dark_theme = true;
+      };
     };
   };
   security.pam.services = {