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

let

  cfg = config.programs.custom.vim;

  nix-xptemplates = pkgs.writeTextFile {
    name = "nix-xptemplates";
    destination = "/ftplugin/nix/nix.xpt.vim";
    text = # vim
      ''
        XPTemplate priority=personal

        XPT option " tips
        `name^ = mkOption {
          type = with types; `type^;
          description = ${"''"}
              `cursor^
          ${"''"};
        };

        XPT package " tips
        { config, lib, ... }:
        {
          `cursor^
        }

        XPT terranix" tips
        { config, lib, pkgs, ... }:
        with lib;
        let
          cfg = config.`name^;
        in {

          options.`name^ = mkOption {
            default = {};
            type = with types; attrsOf (submodule ({ name, ... }:{
              options = {
                enable = mkEnableOption "`name^.name";
              };
            }));
          };

          config =
            let
              allConfigs = cfg
            in
              mkIf (cfg != {} ){
                `cursor^
              };
        }

        XPT module " tips
        { config, lib, pkgs, ... }:

        with lib;

        let

          cfg = config.`name^;

        in {

          options.`name^ = {
              enable = mkEnableOption "enable `name^";
          };

          config = mkIf cfg.enable {
              `cursor^
          };
        }

        XPT shell " tips
        { pkgs ?  import <nixpkgs> {} }:
        pkgs.mkShell {

          # needed pkgs
          # -----------
          buildInputs = with pkgs; [
              `name^
          ];

          # run this on start
          # -----------------
          shellHook = ${"''"}
            HISTFILE=${"$"}{toString ./.}/.history
          ${"''"};
        }

        XPT fhsUser " tips
        { pkgs ? import <nixpkgs> {} }:
        (pkgs.buildFHSUserEnv {
        name = "fhs-user-env";

        targetPkgs = pkgs: with pkgs; [
          # core stuff
          # ----------
          vim silver-searcher curl coreutils git tig

          # common X dependencies
          # ---------------------
          atk cairo dbus eudev expat fontconfig freetype gdk_pixbuf glib gnome3.GConf gtk2-x11
          mesa_glu nspr nss pango xlibs.libXScrnSaver xlibs.libXcomposite xlibs.libXcursor
          xlibs.libXdamage xlibs.libXfixes xlibs.libXi xlibs.libXrender xlibs.libXtst xorg.libX11
          xorg.libXext xorg.libXinerama xorg.libxcb
          liblo zlib fftw minixml libcxx alsaLib glibc

          # new stuff
          # ---------
          `cursor^

        ];

        # multilib packages
        # -----------------
        # these are packages compiled 32bit and 64bit
        multiPkgs = pkgs: with pkgs; [
        ];

        # environment variables
        # ---------------------
        profile = ${"''"}
          export TERM="xterm"
          ${"''"};

        }).env

      '';
  };

  # active plugins
  # --------------
  extra-runtimepath = with pkgs;
    lib.concatMapStringsSep "," (pkg: "${pkg.rtp}") [
      vimPlugins.Syntastic
      vimPlugins.ack-vim
      vimPlugins.airline
      vimPlugins.vim-nix
      vimPlugins.xptemplate
    ];

  # the vimrc
  # ---------
  vimrc = pkgs.writeText "vimrc" ''

    " turn on linenumbers
    " to turn of :set nonumber
    :set number

    " show Trailing Whitespaces
    :set list listchars=tab:»·,trail:¶

    " Map leader is the key for shortcuts
    nnoremap <SPACE> <Nop>
    let mapleader = "\<Space>"

    " move blocks of text in visual mode
    " does not work correctly
    vmap <up> xkP`[V`]
    vmap <down> xp`[V`]

    " search/grep case insensitive
    :set ignorecase

    " tabs should always be 2 spaces
    set et ts=2 sts=2 sw=2

    " installed vim-plugins
    set runtimepath=${extra-runtimepath},$VIMRUNTIME,$HOME/.vim,${nix-xptemplates}

    " syntax highlighting on
    syntax on

    " xptemplates
    " -----------
    " a plugin to insert snippets on demand
    set nocompatible
    filetype plugin on

    " enable cursor cross
    " -------------------
    ":hi CursorLine   cterm=NONE ctermbg=darkred ctermfg=white guibg=darkred guifg=white
    ":hi CursorColumn cterm=NONE ctermbg=darkred ctermfg=white guibg=darkred guifg=white
    :hi CursorLine   cterm=NONE ctermbg=0 guibg=#073642
    :hi CursorColumn cterm=NONE ctermbg=0 guibg=#073642
    set cursorline
    set cursorcolumn

    " save view
    " ---------
    augroup AutoSaveFolds
      autocmd!
      autocmd BufWinLeave * mkview
      autocmd BufWinEnter * silent loadview
    augroup END

    " some language stuff
    " -------------------
    :map <leader>s :setlocal spell spelllang=en

  '';

in
{

  # no options
  options.programs.custom.vim.enable = lib.mkEnableOption "vim";

  config = lib.mkIf cfg.enable {
    # create vimrc
    # ------------
    # and load it as config for vim
    environment.variables.VIMINIT = ":so /etc/vimrc";
    environment.etc.vimrc.source = vimrc;

    # set vim to the default editor
    # -----------------------------
    programs.vim.defaultEditor = true;

    # install vim
    # -----------
    environment.systemPackages = [ pkgs.vim ];
  };

}