# Fetches a chicken egg from henrietta using `chicken-install -r'
# See: http://wiki.call-cc.org/chicken-projects/egg-index-4.html

{ stdenv, chicken }:
{ name, version, md5 ? "", sha256 ? "" }:

stdenv.mkDerivation {
  name = "chicken-${name}-export";
  builder = ./builder.sh;
  buildInputs = [ chicken ];

  outputHashAlgo = if sha256 == "" then "md5" else "sha256";
  outputHashMode = "recursive";
  outputHash = if sha256 == "" then md5 else sha256;

  inherit version;

  eggName = name;

  impureEnvVars = [
    # We borrow these environment variables from the caller to allow
    # easy proxy configuration.  This is impure, but a fixed-output
    # derivation like fetchurl is allowed to do so since its result is
    # by definition pure.
    "http_proxy" "https_proxy" "ftp_proxy" "all_proxy" "no_proxy"
  ];
}