feat: Add Firefox theme

flake.nix

@@ -14,6 +14,12 @@
       repo = "Tokyonight-rofi-theme";
       flake = false;
     };
+    tokyonight-firefox = {
+      type = "github";
+      owner = "D4rkKaizen";
+      repo = "FirefoxCSS-TokyoNight";
+      flake = false;
+    };
   };
 
   outputs = inputs@{ self, ... }: {

modules/home-manager/firefox.nix

@@ -0,0 +1,63 @@
+{ inputs, config, lib, ... }:
+let cfg = config.programs.firefox.tokyonight;
+in {
+  options.programs.firefox.tokyonight =
+    (lib.tn.mkTokyonightOpt "tokyonight firefox") // {
+      profileName = lib.mkOption {
+        type = lib.types.str;
+        description = "The name of your Firefox profile to apply the theme to";
+        example = "default";
+      };
+      extraUserChromeCSS = lib.mkOption {
+        type = lib.types.lines;
+        default = "";
+        example = ''
+          * {
+            font-family: 'Some other font';
+          }
+        '';
+      };
+      extraUserContentCSS = lib.mkOption {
+        type = lib.types.lines;
+        description = "Extra CSS to add to userContent.css";
+        default = "";
+        example = ''
+          @-moz-document url("about:home"),
+          url("about:blank"),
+          url("about:newtab") {
+            // remove background
+            body::before {
+              background: none!important;
+            }
+          }
+        '';
+      };
+    };
+  config = lib.mkMerge [
+    (lib.mkIf cfg.enable {
+      home.file.".mozilla/firefox/default/chrome/firefox-tokyonight-theme" = {
+        # don't include
+        source = "${inputs.tokyonight-firefox}/firefox-css/chrome";
+        recursive = true;
+      };
+      programs.firefox.profiles.${cfg.profileName} = {
+        settings = {
+          "toolkit.legacyUserProfileCustomizations.stylesheets" =
+            true; # Enable customChrome.cs
+          "svg.context-properties.content.enabled" =
+            true; # Enable SVG context-propertes
+        };
+        userChrome = ''
+          @import "firefox-tokyonight-theme/userChrome.css";
+
+          ${cfg.extraUserChromeCSS}
+        '';
+        userContent = ''
+          @import "firefox-tokyonight-theme/userContent.css";
+
+          ${cfg.extraUserContentCSS}
+        '';
+      };
+    })
+  ];
+}