{ stdenv, fetchFromGitHub, cmake, gettext, msgpack, libtermkey, libiconv
, libuv, lua, ncurses, pkgconfig
, unibilium, xsel, gperf
, libvterm-neovim
, glibcLocales ? null, procps ? null

# now defaults to false because some tests can be flaky (clipboard etc)
, doCheck ? false
, nodejs ? null, fish ? null, python ? null
}:

with stdenv.lib;

let
  neovimLuaEnv = lua.withPackages(ps:
    (with ps; [ lpeg luabitop mpack ]
    ++ optionals doCheck [
        nvim-client luv coxpcall busted luafilesystem penlight inspect
      ]
    ));

  pyEnv = python.withPackages(ps: [ ps.pynvim ps.msgpack ]);
in
  stdenv.mkDerivation rec {
    pname = "neovim-unwrapped";
    version = "0.4.3";

    src = fetchFromGitHub {
      owner = "neovim";
      repo = "neovim";
      rev = "v${version}";
      sha256 = "03p7pic7hw9yxxv7fbgls1f42apx3lik2k6mpaz1a109ngyc5kaj";
    };

    patches = [
      # introduce a system-wide rplugin.vim in addition to the user one
      # necessary so that nix can handle `UpdateRemotePlugins` for the plugins
      # it installs. See https://github.com/neovim/neovim/issues/9413.
      ./system_rplugin_manifest.patch
    ];

    dontFixCmake = true;
    enableParallelBuilding = true;

    buildInputs = [
      gperf
      libtermkey
      libuv
      libvterm-neovim
      lua.pkgs.luv.libluv
      msgpack
      ncurses
      neovimLuaEnv
      unibilium
    ] ++ optional stdenv.isDarwin libiconv
      ++ optionals doCheck [ glibcLocales procps ]
    ;

    inherit doCheck;

    # to be exhaustive, one could run
    # make oldtests too
    checkPhase = ''
      make functionaltest
    '';

    nativeBuildInputs = [
      cmake
      gettext
      pkgconfig
    ];

    # extra programs test via `make functionaltest`
    checkInputs = [
      fish
      nodejs
      pyEnv      # for src/clint.py
    ];


    # nvim --version output retains compilation flags and references to build tools
    postPatch = ''
      substituteInPlace src/nvim/version.c --replace NVIM_VERSION_CFLAGS "";
    '';
    # check that the above patching actually works
    disallowedReferences = [ stdenv.cc ];

    cmakeFlags = [
      "-DGPERF_PRG=${gperf}/bin/gperf"
      "-DLUA_PRG=${neovimLuaEnv.interpreter}"
    ]
    # FIXME: this is verry messy and strange.
    ++ optional (!stdenv.isDarwin) "-DLIBLUV_LIBRARY=${lua.pkgs.luv}/lib/lua/${lua.luaversion}/luv.so"
    ++ optional (stdenv.isDarwin) "-DLIBLUV_LIBRARY=${lua.pkgs.luv.libluv}/lib/lua/${lua.luaversion}/libluv.dylib"
    ++ optional doCheck "-DBUSTED_PRG=${neovimLuaEnv}/bin/busted"
    ++ optional (!lua.pkgs.isLuaJIT) "-DPREFER_LUA=ON"
    ;

    # triggers on buffer overflow bug while running tests
    hardeningDisable = [ "fortify" ];

    preConfigure = stdenv.lib.optionalString stdenv.isDarwin ''
      substituteInPlace src/nvim/CMakeLists.txt --replace "    util" ""
    '';

    postInstall = stdenv.lib.optionalString stdenv.isLinux ''
      sed -i -e "s|'xsel|'${xsel}/bin/xsel|g" $out/share/nvim/runtime/autoload/provider/clipboard.vim
    '';

    # export PATH=$PWD/build/bin:${PATH}
    shellHook=''
      export VIMRUNTIME=$PWD/runtime
    '';

    meta = {
      description = "Vim text editor fork focused on extensibility and agility";
      longDescription = ''
        Neovim is a project that seeks to aggressively refactor Vim in order to:
        - Simplify maintenance and encourage contributions
        - Split the work between multiple developers
        - Enable the implementation of new/modern user interfaces without any
          modifications to the core source
        - Improve extensibility with a new plugin architecture
      '';
      homepage    = "https://www.neovim.io";
      # "Contributions committed before b17d96 by authors who did not sign the
      # Contributor License Agreement (CLA) remain under the Vim license.
      # Contributions committed after b17d96 are licensed under Apache 2.0 unless
      # those contributions were copied from Vim (identified in the commit logs
      # by the vim-patch token). See LICENSE for details."
      license = with licenses; [ asl20 vim ];
      maintainers = with maintainers; [ manveru rvolosatovs ma27 ];
      platforms   = platforms.unix;
    };
  }