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

{
  # Only apply the Neovim NixOS module options on Linux.
  config = lib.mkIf pkgs.stdenv.isLinux {
    programs.neovim = {
      enable = true;
      defaultEditor = true;

      configure = {
        customRC = ''
          set title
          set go=a
          set mouse=a
          set nohlsearch
          set number
          let mapleader=","

          lua << EOF
            local config_file = os.getenv("HOME")..'/.local/share/nvim_color_scheme'
            local f = io.open(config_file, "r")
            if f ~= nil then
                local system_theme = f:read()
                io.close(f)
                if system_theme == 'dark' then
                    vim.cmd("set bg=dark")
                elseif system_theme == 'light' then
                    vim.cmd("set bg=light")
                else
                    print('warning: expected value "light" or "dark"')
                    print('  got:', system_theme)
                    print('  expected path:', config_file)
                end
            else
                print('warning: nvim color scheme not found')
                print('  expected path:', config_file)
            end
          EOF

          colorscheme catppuccin " catppuccin-latte, catppuccin-frappe, catppuccin-macchiato, catppuccin-mocha

          " netrw (dir listing) settings
          let g:netrw_liststyle = 3
          let g:netrw_banner = 0
          let g:netrw_browse_split = 3
          let g:netrw_winsize = 25  " % of page

          set listchars=tab:→\ ,space:·,nbsp:␣,trail:•,eol:¶,precedes:«,extends:»
          set clipboard+=unnamedplus

          " Replace-all is aliased to S.
          nnoremap S :%s//g<Left><Left>

          " save file with ,w
          map <leader>w :w<cr><Space>

          " spellcheck
          set spell spelllang=en_us
          setlocal spell! spelllang=en_us
        '';

        # vimPlugins inspired from Alexnortung
        # https://discourse.nixos.org/t/neovim-no-longer-uses-config-or-plugins/13399/4
        packages.nix = with pkgs.vimPlugins; {
          start = [
            vim-surround    # shortcuts for setting () {} etc.
            vim-gitgutter   # git diff in sign column
            # vim-airline   # nice and light status bar (disabled for tmux)
            # coc-nvim coc-* plugins (disabled for now)
            vim-nix         # nix highlight
            vimtex          # latex stuff
            fzf-vim         # fuzzy finder through vim
            nerdtree        # file structure inside nvim
            rainbow         # color parenthesis
            # gruvbox-nvim  # theme
            catppuccin-nvim # theme
            goyo-vim        # write prose
            limelight-vim   # prose paragraph highlighter
          ];
          opt = [];
        };
      };
    };
  };
}