# XDG stands for "Cross-Desktop Group", with X used to mean "cross".
# It's a bunch of specifications from freedesktop.org intended to standardize desktops and
# other GUI applications on various systems (primarily Unix-like) to be interoperable:
#   https://www.freedesktop.org/wiki/Specifications/
{ config, pkgs, ... }: {
  home.packages = with pkgs; [
    xdg-utils # provides cli tools such as `xdg-mime` `xdg-open`
    xdg-user-dirs
  ];

  xdg = {
    enable = true;
    cacheHome = config.home.homeDirectory + "/.cache";

    # manage $XDG_CONFIG_HOME/mimeapps.list
    # xdg search all desktop entries from $XDG_DATA_DIRS, check it by command:
    #  echo $XDG_DATA_DIRS
    # the system-level desktop entries can be list by command:
    #   ls -l /run/current-system/sw/share/applications/
    # the user-level desktop entries can be list by command(user ryan):
    #  ls /etc/profiles/per-user/ryan/share/applications/
    mimeApps = {
      enable = true;
      # defaultApplications =
      #   let
      #     browser = [ "microsoft-edge.desktop" ];
      #   in
      #   {
      #     "application/json" = browser;
      #     "application/pdf" = browser; # TODO: pdf viewer

      #     "text/html" = browser;
      #     "text/xml" = browser;
      #     "application/xml" = browser;
      #     "application/xhtml+xml" = browser;
      #     "application/xhtml_xml" = browser;
      #     "application/rdf+xml" = browser;
      #     "application/rss+xml" = browser;
      #     "application/x-extension-htm" = browser;
      #     "application/x-extension-html" = browser;
      #     "application/x-extension-shtml" = browser;
      #     "application/x-extension-xht" = browser;
      #     "application/x-extension-xhtml" = browser;

      #     "x-scheme-handler/about" = browser;
      #     "x-scheme-handler/ftp" = browser;
      #     "x-scheme-handler/http" = browser;
      #     "x-scheme-handler/https" = browser;
      #     "x-scheme-handler/unknown" = browser;

      #     "x-scheme-handler/discord" = [ "discord.desktop" ];
      #     "x-scheme-handler/tg" = [ "telegramdesktop.desktop" ];

      #     "audio/*" = [ "vlc.desktop" ];
      #     "video/*" = [ "vlc.dekstop" ];
      #     "image/*" = [ "imv.desktop" ];
      #     "image/gif" = [ "imv.desktop" ];
      #     "image/jpeg" = [ "imv.desktop" ];
      #     "image/png" = [ "imv.desktop" ];
      #     "image/webp" = [ "imv.desktop" ];
      #   };

      associations.removed =
        {
          # ......
        };
    };

    userDirs = {
      enable = false;
      createDirectories = false;
      extraConfig = {
        XDG_SCREENSHOTS_DIR = "${config.xdg.userDirs.pictures}/Screenshots";
      };
    };
  };
}