home-manager/modules/misc/xdg-mime-apps.nix

{
  config,
  lib,
  pkgs,
  ...
}:

let
  inherit (lib) mkOption types;

  cfg = config.xdg.mimeApps;

  strListOrSingleton = with types; coercedTo (either (listOf str) str) lib.toList (listOf str);

in
{
  meta.maintainers = with lib.maintainers; [ euxane ];

  options.xdg.mimeApps = {
    enable = mkOption {
      type = types.bool;
      default = false;
      description = ''
        Whether to manage {file}`$XDG_CONFIG_HOME/mimeapps.list`.

        The generated file is read-only.
      '';
    };

    # descriptions from
    # https://specifications.freedesktop.org/mime-apps-spec/mime-apps-spec-1.0.1.html

    associations.added = mkOption {
      type = types.attrsOf strListOrSingleton;
      default = { };
      example = lib.literalExpression ''
        {
          "mimetype1" = [ "foo1.desktop" "foo2.desktop" "foo3.desktop" ];
          "mimetype2" = "foo4.desktop";
        }
      '';
      description = ''
        Defines additional associations of applications with
        mimetypes, as if the .desktop file was listing this mimetype
        in the first place.
      '';
    };

    associations.removed = mkOption {
      type = types.attrsOf strListOrSingleton;
      default = { };
      example = {
        "mimetype1" = "foo5.desktop";
      };
      description = ''
        Removes associations of applications with mimetypes, as if the
        .desktop file was *not* listing this
        mimetype in the first place.
      '';
    };

    defaultApplications = mkOption {
      type = types.attrsOf strListOrSingleton;
      default = { };
      example = lib.literalExpression ''
        {
          "mimetype1" = [ "default1.desktop" "default2.desktop" ];
        }
      '';
      description = ''
        The default application to be used for a given mimetype. This
        is, for instance, the one that will be started when
        double-clicking on a file in a file manager. If the
        application is no longer installed, the next application in
        the list is attempted, and so on.
      '';
    };
  };

  config = lib.mkMerge [
    {
      # Given a package that installs .desktop files in the usual location,
      # return a mapping from mime types to lists of desktop file names. This is
      # suitable for use with `xdg.mimeApps.defaultApplications`.
      lib.xdg.mimeAssociations =
        let
          processLines =
            str: lib.zipAttrs (lib.filter (e: e != null) (map processLine (lib.splitString "\n" str)));

          processLine =
            str:
            let
              entry = lib.splitString ";" str;
              k = lib.elemAt entry 0;
              v = lib.elemAt entry 1;
            in
            if lib.length entry == 2 then { ${k} = v; } else null;

          associations =
            ps:
            pkgs.runCommand "mime-assoc" { inherit ps; } ''
              for p in $ps ; do
                for path in "$p"/share/applications/*.desktop ; do
                  name="''${path##*/}"
                  sed -n -E "/^MimeType=/ { s/.*=//; s/;?$|;/;$name\n/g; p; }" "$path"
                done
              done > "$out"
            '';
        in
        p: processLines (builtins.readFile (associations p));
    }

    (lib.mkIf cfg.enable {
      assertions = [
        (lib.hm.assertions.assertPlatform "xdg.mimeApps" pkgs lib.platforms.linux)
      ];

      # Deprecated but still used by some applications.
      xdg.dataFile."applications/mimeapps.list".source = config.xdg.configFile."mimeapps.list".source;

      xdg.configFile."mimeapps.list".text =
        let
          joinValues = lib.mapAttrs (n: lib.concatStringsSep ";");
        in
        lib.generators.toINI { } {
          "Added Associations" = joinValues cfg.associations.added;
          "Removed Associations" = joinValues cfg.associations.removed;
          "Default Applications" = joinValues cfg.defaultApplications;
        };
    })
  ];
}