nix/module.nix: expand nixos module for configuring hyprland

Expand the nixos module to be able to configure hyprland, just like the
current home-manager module does.

nix/module.nix

@@ -11,11 +11,209 @@ inputs: {
   portalPackage = inputs.self.packages.${system}.xdg-desktop-portal-hyprland.override {
     hyprland = cfg.finalPackage;
   };
+
+# basically 1:1 taken from https://github.com/nix-community/home-manager/blob/master/modules/services/window-managers/hyprland.nix
+  toHyprconf = {
+    attrs,
+    indentLevel ? 0,
+    importantPrefixes ? ["$"],
+  }: let
+    inherit
+      (lib)
+      all
+      concatMapStringsSep
+      concatStrings
+      concatStringsSep
+      filterAttrs
+      foldl
+      generators
+      hasPrefix
+      isAttrs
+      isList
+      mapAttrsToList
+      replicate
+      ;
+
+    initialIndent = concatStrings (replicate indentLevel "  ");
+
+    toHyprconf' = indent: attrs: let
+      sections =
+        filterAttrs (n: v: isAttrs v || (isList v && all isAttrs v)) attrs;
+
+      mkSection = n: attrs:
+        if lib.isList attrs
+        then (concatMapStringsSep "\n" (a: mkSection n a) attrs)
+        else ''
+          ${indent}${n} {
+          ${toHyprconf' "  ${indent}" attrs}${indent}}
+        '';
+
+      mkFields = generators.toKeyValue {
+        listsAsDuplicateKeys = true;
+        inherit indent;
+      };
+
+      allFields =
+        filterAttrs (n: v: !(isAttrs v || (isList v && all isAttrs v)))
+        attrs;
+
+      isImportantField = n: _:
+        foldl (acc: prev:
+          if hasPrefix prev n
+          then true
+          else acc)
+        false
+        importantPrefixes;
+
+      importantFields = filterAttrs isImportantField allFields;
+
+      fields =
+        builtins.removeAttrs allFields
+        (mapAttrsToList (n: _: n) importantFields);
+    in
+      mkFields importantFields
+      + concatStringsSep "\n" (mapAttrsToList mkSection sections)
+      + mkFields fields;
+  in
+    toHyprconf' initialIndent attrs;
 in {
-  config = {
+  options = {
     programs.hyprland = {
-      package = lib.mkDefault package;
+      plugins = lib.mkOption {
-      portalPackage = lib.mkDefault portalPackage;
+        type = with lib.types; listOf (either package path);
+        default = [];
+        description = ''
+          List of Hyprland plugins to use. Can either be packages or
+          absolute plugin paths.
+        '';
+      };
+
+      settings = lib.mkOption {
+        type = with lib.types; let
+          valueType =
+            nullOr (oneOf [
+              bool
+              int
+              float
+              str
+              path
+              (attrsOf valueType)
+              (listOf valueType)
+            ])
+            // {
+              description = "Hyprland configuration value";
+            };
+        in
+          valueType;
+        default = {};
+        description = ''
+          Hyprland configuration written in Nix. Entries with the same key
+          should be written as lists. Variables' and colors' names should be
+          quoted. See <https://wiki.hyprland.org> for more examples.
+
+          ::: {.note}
+          Use the [](#programs.hyprland.plugins) option to
+          declare plugins.
+          :::
+
+        '';
+        example = lib.literalExpression ''
+          {
+            decoration = {
+              shadow_offset = "0 5";
+              "col.shadow" = "rgba(00000099)";
+            };
+
+            "$mod" = "SUPER";
+
+            bindm = [
+              # mouse movements
+              "$mod, mouse:272, movewindow"
+              "$mod, mouse:273, resizewindow"
+              "$mod ALT, mouse:272, resizewindow"
+            ];
+          }
+        '';
+      };
+
+      extraConfig = lib.mkOption {
+        type = lib.types.lines;
+        default = "";
+        example = ''
+          # window resize
+          bind = $mod, S, submap, resize
+
+          submap = resize
+          binde = , right, resizeactive, 10 0
+          binde = , left, resizeactive, -10 0
+          binde = , up, resizeactive, 0 -10
+          binde = , down, resizeactive, 0 10
+          bind = , escape, submap, reset
+          submap = reset
+        '';
+        description = ''
+          Extra configuration lines to add to `/etc/xdg/hypr/hyprland.conf`.
+        '';
+      };
+
+      sourceFirst =
+        lib.mkEnableOption ''
+          putting source entries at the top of the configuration
+        ''
+        // {
+          default = true;
+        };
+
+      importantPrefixes = lib.mkOption {
+        type = with lib.types; listOf str;
+        default =
+          ["$" "bezier" "name"]
+          ++ lib.optionals cfg.sourceFirst ["source"];
+        example = ["$" "bezier"];
+        description = ''
+          List of prefix of attributes to source at the top of the config.
+        '';
+      };
     };
   };
+  config =
+    {
+      programs.hyprland = {
+        package = lib.mkDefault package;
+        portalPackage = lib.mkDefault portalPackage;
+      };
+    }
+    // lib.mkIf cfg.enable {
+      environment.systemPackages = lib.concatLists [
+        (lib.optional (cfg.xwayland.enable) pkgs.xwayland)
+      ];
+      environment.etc."xdg/hypr/hyprland.conf" = let
+        shouldGenerate = cfg.extraConfig != "" || cfg.settings != {} || cfg.plugins != [];
+
+        pluginsToHyprconf = plugins:
+          toHyprconf {
+            attrs = {
+              plugin = let
+                mkEntry = entry:
+                  if lib.types.package.check entry
+                  then "${entry}/lib/lib${entry.pname}.so"
+                  else entry;
+              in
+                map mkEntry cfg.plugins;
+            };
+            inherit (cfg) importantPrefixes;
+          };
+      in
+        lib.mkIf shouldGenerate {
+          text =
+            lib.optionalString (cfg.plugins != [])
+            (pluginsToHyprconf cfg.plugins)
+            + lib.optionalString (cfg.settings != {})
+            (toHyprconf {
+              attrs = cfg.settings;
+              inherit (cfg) importantPrefixes;
+            })
+            + lib.optionalString (cfg.extraConfig != "") cfg.extraConfig;
+        };
+    };
 }