nichts/modules/other/xdg.nix

{
  config,
  pkgs,
  ...
}: let
  inherit (config.modules.other.system) username;
  hmCfg = config.home-manager.users.${username};

  primary_browser = "Schizofox.desktop";
  mail_client = "thunderbird.desktop";
  file_manager = "nautilus.desktop";
  media_player = "mpv.desktop";
  image_viewer = "imv.desktop";
  text_editor = "helix.desktop";
  terminal = "foot.desktop";
  pdf_viewer = "org.gnome.Evince.desktop";
in {
  environment.sessionVariables = {
    TERMINAL = "${terminal}";
    XDG_CACHE_HOME = hmCfg.xdg.cacheHome;
  };

  home-manager.users.${username} = {
    home.packages = [pkgs.xdg-utils];
    xdg = {
      cacheHome = "${hmCfg.home.homeDirectory}/.cache";
      configHome = "${hmCfg.home.homeDirectory}/.config";
      dataHome = "${hmCfg.home.homeDirectory}/.local/share";
      stateHome = "${hmCfg.home.homeDirectory}/.local/state";
      mimeApps = {
        enable = true;
        defaultApplications = {
          "text/html" = [primary_browser];
          "x-scheme-handler/http" = [primary_browser];
          "x-scheme-handler/https" = [primary_browser];
          "x-scheme-handler/about" = [primary_browser];
          "x-scheme-handler/unknown" = [primary_browser];
          "x-scheme-handler/mailto" = [mail_client];
          "message/rfc822" = [mail_client];
          "x-scheme-handler/mid" = [mail_client];
          "inode/directory" = [file_manager];
          "audio/mp3" = [media_player];
          "audio/ogg" = [media_player];
          "audio/mpeg" = [media_player];
          "audio/aac" = [media_player];
          "audio/opus" = [media_player];
          "audio/wav" = [media_player];
          "audio/webm" = [media_player];
          "audio/3gpp" = [media_player];
          "audio/3gpp2" = [media_player];
          "video/mp4" = [media_player];
          "video/x-msvideo" = [media_player];
          "video/mpeg" = [media_player];
          "video/ogg" = [media_player];
          "video/mp2t" = [media_player];
          "video/webm" = [media_player];
          "video/3gpp" = [media_player];
          "video/3gpp2" = [media_player];
          "image/png" = [image_viewer];
          "image/jpeg" = [image_viewer];
          "image/gif" = [image_viewer];
          "image/avif" = [image_viewer];
          "image/bmp" = [image_viewer];
          "image/vnd.microsoft.icon" = [image_viewer];
          "image/svg+xml" = [image_viewer];
          "image/tiff" = [image_viewer];
          "image/webp" = [image_viewer];
          "text/plain" = [text_editor];
          "application/pdf" = [pdf_viewer];
        };
      };
    };
  };
}