{ fetchurl, lib, stdenv }@args:

let

  buildFirefoxXpiAddon = lib.makeOverridable ({ stdenv ? args.stdenv
    , fetchurl ? args.fetchurl, pname, version, addonId, url, sha256, meta, ...
    }:
    stdenv.mkDerivation {
      name = "${pname}-${version}";

      inherit meta;

      src = fetchurl { inherit url sha256; };

      preferLocalBuild = true;
      allowSubstitutes = true;

      buildCommand = ''
        dst="$out/share/mozilla/extensions/{ec8030f7-c20a-464f-9b0e-13a3a9e97384}"
        mkdir -p "$dst"
        install -v -m644 "$src" "$dst/${addonId}.xpi"
      '';
    });

  packages = import ./generated-firefox-addons.nix {
    inherit buildFirefoxXpiAddon fetchurl lib stdenv;
  };

in packages // {
  inherit buildFirefoxXpiAddon;

  seventv = let
    version = "v3.0.10.1000";
  in buildFirefoxXpiAddon {
    pname = "seventv";
    inherit version;
    addonId = "moz-addon@7tv.app";
    url = "https://extension.7tv.gg/${version}/ext.xpi";
    sha256 = "sha256-dZyjFayvnLebSZHjMTTQFjcsxxpmc1aL5q17mLF3kG8=";
    meta = with lib; {
      homepage = "https://7tv.app/";
      description = "The Web Extension for 7TV, bringing new features, emotes, vanity and performance to Twitch, Kick & YouTube";
      license = licenses.asl20;
      platforms = platforms.all;
    };
  };
}