/*
compressDrvWeb compresses a derivation for common web server use.

Useful when one wants to pre-compress certain static assets and pass them to
the web server. For example, `pkgs.gamja` creates this derivation:

    /nix/store/2wn1qbk8gp4y2m8xvafxv1b2dcdqj8fz-gamja-1.0.0-beta.9/
    ├── index.2fd01148.js
    ├── index.2fd01148.js.map
    ├── index.37aa9a8a.css
    ├── index.37aa9a8a.css.map
    ├── index.html
    └── manifest.webmanifest

`pkgs.compressDrvWeb pkgs.gamja`:

    /nix/store/f5ryid7zrw2hid7h9kil5g5j29q5r2f7-gamja-1.0.0-beta.9-compressed
    ├── index.2fd01148.js -> /nix/store/2wn1qbk8gp4y2m8xvafxv1b2dcdqj8fz-gamja-1.0.0-beta.9/index.2fd01148.js
    ├── index.2fd01148.js.br
    ├── index.2fd01148.js.gz
    ├── index.2fd01148.js.map -> /nix/store/2wn1qbk8gp4y2m8xvafxv1b2dcdqj8fz-gamja-1.0.0-beta.9/index.2fd01148.js.map
    ├── index.2fd01148.js.map.br
    ├── index.2fd01148.js.map.gz
    ├── index.37aa9a8a.css -> /nix/store/2wn1qbk8gp4y2m8xvafxv1b2dcdqj8fz-gamja-1.0.0-beta.9/index.37aa9a8a.css
    ├── index.37aa9a8a.css.br
    ├── index.37aa9a8a.css.gz
    ├── index.37aa9a8a.css.map -> /nix/store/2wn1qbk8gp4y2m8xvafxv1b2dcdqj8fz-gamja-1.0.0-beta.9/index.37aa9a8a.css.map
    ├── index.37aa9a8a.css.map.br
    ├── index.37aa9a8a.css.map.gz
    ├── index.html -> /nix/store/2wn1qbk8gp4y2m8xvafxv1b2dcdqj8fz-gamja-1.0.0-beta.9/index.html
    ├── index.html.br
    ├── index.html.gz
    ├── manifest.webmanifest -> /nix/store/2wn1qbk8gp4y2m8xvafxv1b2dcdqj8fz-gamja-1.0.0-beta.9/manifest.webmanifest
    ├── manifest.webmanifest.br
    └── manifest.webmanifest.gz


When this `-compressed` directory is passed to a properly configured web
server, it will serve those pre-compressed files:

    $ curl -I -H 'Accept-Encoding: br' https://irc.example.org/
    <...>
    content-encoding: br
    <...>

For example, a caddy configuration snippet for gamja to serve
the static assets (JS, CSS files) pre-compressed:

    virtualHosts."irc.example.org".extraConfig = ''
      root * ${pkgs.compressDrvWeb pkgs.gamja {}}
      file_server browse {
          precompressed br gzip
      }
    '';

This feature is also available in nginx via `ngx_brotli` and
`ngx_http_gzip_static_module`.

Inputs:
- formats :: [String]

    List of file extensions to compress.

    Default: common formats that compress well. The list may be expanded.

- extraFormats :: [String]

    Extra extensions to compress in addition to `formats`.

- compressors :: [String]

    A list of compressor names to use. Each element will need to have
    an associated compressor in the same arguments (see below).

    Default: ["gz" "br"]

  - extraCompressors :: [String]

    Extra compressors in addition to `compressors`.

- compressor-<COMPRESSOR> :: String

    Map a desired extension (e.g. `gz`) to a compress program.

    The compressor program that will be executed to get the `COMPRESSOR`
    extension. The program is passed to xargs like this:

      xargs -I{} -n1 ${prog}

    Default:

      compressor-gz = "${zopfli}/bin/zopfli --keep {}";
      compressor-br = "${brotli}/bin/brotli --keep --no-copy-stat {}";
*/
{
  lib,
  zopfli,
  brotli,
  compressDrv,
}: drv: {
  formats ? ["css" "js" "svg" "ttf" "eot" "txt" "xml" "map" "html" "json" "webmanifest"],
  extraFormats ? [],
  compressors ? ["gz" "br"],
  extraCompressors ? [],
  ...
} @ args:
compressDrv drv ({
    formats = formats ++ extraFormats;
    compressors = compressors ++ extraCompressors;
    compressor-gz = "${zopfli}/bin/zopfli --keep {}";
    compressor-br = "${brotli}/bin/brotli --keep --no-copy-stat {}";
  }
  // lib.filterAttrs (k: _: (lib.hasPrefix "compressor-" k)) args)