{pkgs, ...}: {
  environment.variables = {EDITOR = "vim";};

  environment.systemPackages = with pkgs; [
    # Add python packages required by NeoVim in NixOS
    (python3.withPackages (ps: [
      ps.pygments
    ]))
    (neovim.override {
      vimAlias = true;
      configure = {
        packages.myPlugins = with pkgs.vimPlugins; {
          start = [
            deoplete-nvim # an extensible and asynchronous completion framework
            formatter-nvim # A format runner for neovim
            fugitive # Vim Git wrapper
            fzf-vim # Full path fuzzy file, buffer, mru, tag, finder for Vim
            #haskell-vim # Syntax Highlighting and Indentation for Haskell
            indentLine # Display thin vertical lines at each indentation level
            lualine-nvim
            YouCompleteMe # A code-completion engine for Vim
            neomake # asynchronously run programs like vim-terraform
            nerdcommenter # Comment functions so powerful—no comment necessary
            nerdtree # File system explorer
            nerdtree-git-plugin # Plugin for nerdtree showing git status
            nvim-treesitter # configurations and abstraction layer for Neovim.
            onedarkpro-nvim # Dark and light themes for Neovim
            supertab # Allows you to use <Tab> for all your insert completion
            syntastic # Syntax checking hacks
            vim-terraform # tab completion, syntax highlighting, indentation
            vim-terraform-completion
            vim-cue # Cue filetype plugin for Vim
            vim-lastplace
            vim-markdown-toc # Generate table of contents for Markdown files
            vim-nix # Support for writing Nix expressions in vim
            vim-numbertoggle # Toggle between relative / absolute line numbers automatically
            vim-one
          ];
          opt = [];
        };
        # Write a custom Neovim config for NixOS
        customRC = ''
          " Preferred global default settings:
          set mouse=                    " disable mouse input
          set nocompatible
          set backspace=indent,eol,start
          set number relativenumber     " Enable relative line numbers by default
          set cursorline                " Highlight the current line number
          set smartindent               " Automatically insert extra level of indentation
          set tabstop=4                 " Default tabstop
          set shiftwidth=4              " Default indent spacing
          set expandtab                 " Expand [TABS] to spaces
          syntax on                     " Enable syntax highlighting
          set t_Co=256                  " Use 265 colors in vim
          set background=dark           " Set the default background scheme
          colorscheme onedark           " Set the default colour scheme
          "let g:one_allow_italics = 1   " I love italic for comments
          set spell spelllang=en_au     " Defaul spell checking language
          set spellfile=~/.vim-spell.en.utf-8.add    " Add the spellfile
          hi clear SpellBad             " Clear any unwanted default settings
          hi SpellBad cterm=underline   " Set the spell checking highlight style
          hi SpellBad ctermbg=NONE      " Set the spell checking highlight background
          match ErrorMsg '\s\+$'        "

          nnoremap <silent> <C-p> :Files<CR>
          nnoremap <silent> <Leader>f :Rg<CR>
          set grepprg=rg\ --vimgrep\ --smart-case\ --follow

          "call togglebg#map("<F10>")   " Toggle background colour between dark|light

          set laststatus=2   " Set up the status line so it's coloured and always on

          " Removes trailing spaces:
          function! TrimWhiteSpace()
              %s/\s\+$//e
          endfunction

          " Trigger for numbertoggle to switch modes
          nnoremap <silent> <C-n> :set relativenumber!<CR>

          " Tab settings
          let g:SuperTabDefaultCompletionType = 'context'
          let g:SuperTabContextTextOmniPrecedence = ['&omnifunc','&completefunc']
          let g:SuperTabRetainCompletionType=2

          inoremap <expr><Enter>  pumvisible() ? "\<C-Y>" : "\<Enter>"
          inoremap <expr><TAB>  pumvisible() ? "\<C-n>" : "\<TAB>"

          nnoremap <silent> <Leader>RemoveTrailingWhiteSpace :call TrimWhiteSpace()<CR>
          autocmd FileWritePre    * :call TrimWhiteSpace()
          autocmd FileAppendPre   * :call TrimWhiteSpace()
          autocmd FilterWritePre  * :call TrimWhiteSpace()
          autocmd BufWritePre     * :call TrimWhiteSpace()

          augroup FormatAutogroup
            autocmd!
            autocmd BufWritePost * silent! FormatWrite
          augroup END

          " FIXME: Currently always set to dark due to issues with Termonad Solarized theme
          " Light during the day, dark during the night
          let hour = strftime("%H")
          if 7 <= hour && hour < 17
            "set background=dark
            hi Normal guibg=NONE ctermbg=NONE   " Set a transparent background
            hi NormalNC guibg=NONE ctermbg=NONE " Set a transparent background
          else
            "set background=dark
            hi Normal guibg=NONE ctermbg=NONE   " Set a transparent background
            hi NormalNC guibg=NONE ctermbg=NONE " Set a transparent background
          endif

          " Transparent editing of gpg encrypted files.
          " By Wouter Hanegraaff <wouter@blub.net>
          augroup encrypted
              au!

              " First make sure nothing is written to ~/.viminfo while editing an encrypted file.
              autocmd BufReadPre,FileReadPre      *.gpg set viminfo=
              " We don't want a swap file, as it writes unencrypted data to disk
              autocmd BufReadPre,FileReadPre      *.gpg set noswapfile
              " Switch to binary mode to read the encrypted file
              autocmd BufReadPre,FileReadPre      *.gpg set bin
              autocmd BufReadPre,FileReadPre      *.gpg let ch_save = &ch|set ch=2
              autocmd BufReadPost,FileReadPost    *.gpg '[,']!gpg --decrypt 2> /dev/null
              " Switch to normal mode for editing
              autocmd BufReadPost,FileReadPost    *.gpg set nobin
              autocmd BufReadPost,FileReadPost    *.gpg let &ch = ch_save|unlet ch_save
              autocmd BufReadPost,FileReadPost    *.gpg execute ":doautocmd BufReadPost " . expand("%:r")

              " Convert all text to encrypted text before writing
              autocmd BufWritePre,FileWritePre    *.gpg   '[,']!gpg --default-key=7E66C3B5CDE94A4A --default-recipient-self -ae 2>/dev/null
              " Undo the encryption so we are back in the normal text, directly
              " after the file has been written.
              autocmd BufWritePost,FileWritePost    *.gpg   u
          augroup END

          " Manage ISO files
          augroup iso
              au!

              " First make sure nothing is written to ~/.viminfo while editing an encrypted file.
              autocmd BufReadPre,FileReadPre      *.iso set viminfo=
              " We don't want a swap file, as it writes unencrypted data to disk
              autocmd BufReadPre,FileReadPre      *.iso set noswapfile
              " Switch to binary mode to read the encrypted file
              autocmd BufReadPre,FileReadPre      *.iso set bin
              autocmd BufReadPre,FileReadPre      *.iso let ch_save = &ch|set ch=2
              autocmd BufReadPost,FileReadPost    *.iso '[,']!gpg --decrypt 2> /dev/null
              " Switch to normal mode for editing
              autocmd BufReadPost,FileReadPost    *.iso set nobin
              autocmd BufReadPost,FileReadPost    *.iso let &ch = ch_save|unlet ch_save
              autocmd BufReadPost,FileReadPost    *.iso execute ":doautocmd BufReadPost " . expand("%:r")

              " Convert all text to encrypted text before writing
              autocmd BufWritePre,FileWritePre    *.iso   '[,']!gpg --default-key=A4122FF3971B6865 --default-recipient-self -ae 2>/dev/null
              " Undo the encryption so we are back in the normal text, directly
              " after the file has been written.
              autocmd BufWritePost,FileWritePost    *.iso   u
          augroup END

          " Use persistent history.
          if !isdirectory("/tmp/.vim-undo-dir")
              call mkdir("/tmp/.vim-undo-dir", "", 0700)
          endif
          set undodir=/tmp/.vim-undo-dir
          set undofile

          " My Markdown environment
          function! MarkdownSettings()
              set textwidth=79
              set spell spelllang=en_au
          endfunction
          autocmd BufNewFile,BufFilePre,BufRead *.mdwn :call MarkdownSettings()
          autocmd BufNewFile,BufFilePre,BufRead *.md :call MarkdownSettings()

          " My ReStructured Text environment
          function! ReStructuredSettings()
              set textwidth=79
              set spell spelllang=en_au
              hi clear SpellBad             " Clear any unwanted default settings
              hi SpellBad cterm=underline   " Set the spell checking highlight style
              hi SpellBad ctermbg=NONE      " Set the spell checking highlight background
          endfunction
          autocmd BufNewFile,BufFilePre,BufRead *.rst :call ReStructuredSettings()
          autocmd BufNewFile,BufFilePre,BufRead *.txt :call ReStructuredSettings()

          " My LaTeX environment:
          function! LaTeXSettings()
              set textwidth=79
              set spell spelllang=en_au
          endfunction
          autocmd BufNewFile,BufFilePre,BufRead *.tex :call LaTeXSettings()

          " Settings for my Haskell environment:
          function! HaskellSettings()
              set tabstop=2
              set shiftwidth=2
              set expandtab
              set textwidth=79
              "let g:haskell_enable_quantification = 1   " to enable highlighting of `forall`
              "let g:haskell_enable_recursivedo = 1      " to enable highlighting of `mdo` and `rec`
              "let g:haskell_enable_arrowsyntax = 1      " to enable highlighting of `proc`
              "let g:haskell_enable_pattern_synonyms = 1 " to enable highlighting of `pattern`
              "let g:haskell_enable_typeroles = 1        " to enable highlighting of type roles
              "let g:haskell_enable_static_pointers = 1  " to enable highlighting of `static`
              "let g:haskell_backpack = 1
          endfunction
          autocmd BufNewFile,BufFilePre,BufRead *.hs :call HaskellSettings()

          " Settings for my Nix environment:
          function! NixSettings()
              set tabstop=2
              set shiftwidth=2
              set expandtab
              set textwidth=79
              set filetype=nix
          endfunction
          autocmd BufNewFile,BufFilePre,BufRead *.nix :call NixSettings()

          " Settings for my Cue environment:
          function! CueSettings()
              set noexpandtab
              set tabstop=2
              set shiftwidth=2
              set textwidth=79
              let g:cue_fmt_on_save = 1
          endfunction
          autocmd BufNewFile,BufFilePre,BufRead *.cue :call CueSettings()

          " Settings for my Rust environment:
          function! RustSettings()
              set tabstop=4
              set shiftwidth=4
              set expandtab
              set textwidth=79
              let g:rustfmt_autosave = 1
          endfunction
          autocmd BufNewFile,BufFilePre,BufRead *.rs :call RustSettings()

          " Settings for my Crystal environment:
          function! CrystalSettings()
              set tabstop=2
              set shiftwidth=2
              set expandtab
              set textwidth=79
              set filetype=crystal
          endfunction
          autocmd BufNewFile,BufFilePre,BufRead *.cr :call CrystalSettings()

          " Settings for my Golang environment:
          function! GoSettings()
              set tabstop=7
              set shiftwidth=7
              set noexpandtab
          endfunction
          autocmd BufNewFile,BufFilePre,BufRead *.go :call GoSettings()

          " Settings for my Python environment:
          function! PythonSettings()
              set tabstop=4
              set shiftwidth=4
              set expandtab
              set textwidth=79
              set spell!
          endfunction
          autocmd BufNewFile,BufFilePre,BufRead *.py :call PythonSettings()

          " My Mutt environment
          function! MuttSettings()
              set textwidth=79
              set spell spelllang=en_au
              hi clear SpellBad             " Clear any unwanted default settings
              hi SpellBad cterm=underline   " Set the spell checking highlight style
              hi SpellBad ctermbg=NONE      " Set the spell checking highlight background
          endfunction
          autocmd BufNewFile,BufFilePre,BufRead mutt-* :call MuttSettings()
          autocmd BufNewFile,BufFilePre,BufRead neomutt-* :call MuttSettings()

          " Settings for my C environment:
          function! CSettings()
              set tabstop=2
              set shiftwidth=2
              set expandtab
              set textwidth=79
          endfunction
          autocmd BufNewFile,BufFilePre,BufRead *.c :call CSettings()

          " Settings for my YAML environment:
          function! YAMLSettings()
              set tabstop=2
              set shiftwidth=2
              set expandtab
              set textwidth=79
              set spell spelllang=en_au
              hi clear SpellBad             " Clear any unwanted default settings
              hi SpellBad cterm=underline   " Set the spell checking highlight style
              hi SpellBad ctermbg=NONE      " Set the spell checking highlight background
          endfunction
          autocmd BufNewFile,BufFilePre,BufRead *.yaml :call YAMLSettings()
          autocmd BufNewFile,BufFilePre,BufRead *.yml :call YAMLSettings()

          " Settings for my Bash environment:
          function! BashSettings()
              set tabstop=4
              set shiftwidth=4
              set expandtab
              set textwidth=79
              set spell!
          endfunction
          autocmd BufNewFile,BufFilePre,BufRead *.sh :call BashSettings()

          lua <<EOF
            local treefmt = {
              function()
                return {
                  exe = "treefmt",
                  args = {"--stdin", vim.fn.fnameescape(vim.api.nvim_buf_get_name(0))},
                  stdin = true,
                }
              end
            }
            require("formatter").setup({
              filetype = {
                crystal = treefmt,
                cue = treefmt,
                go = treefmt,
                haskell = treefmt,
                javascript = treefmt,
                lua = treefmt,
                mint = treefmt,
                markdown = treefmt,
                nix = treefmt,
                rego = treefmt,
                ruby = treefmt,
                rust = treefmt,
                vim = treefmt,
              }
            })
          EOF
        '';
      };
    })
  ];
}