shell.nix

{ nixpkgs ? import <nixpkgs> {}, compiler ? "default", doBenchmark ? false }:

let

  inherit (nixpkgs) pkgs;

  f = { mkDerivation, Agda, base, containers, haskell-src-exts
      , stdenv
      }:
      mkDerivation {
        pname = "agda2hs";
        version = "1.0";
        src = ./.;
        isLibrary = false;
        isExecutable = true;
        executableHaskellDepends = [
          Agda base containers haskell-src-exts
        ];
        description = "Compiling Agda code to readable Haskell";
        license = stdenv.lib.licenses.bsd3;
      };

  haskellPackages = if compiler == "default"
                       then pkgs.haskellPackages
                       else pkgs.haskell.packages.${compiler};

  variant = if doBenchmark then pkgs.haskell.lib.doBenchmark else pkgs.lib.id;

  drv = variant (haskellPackages.callPackage f {});

in

  if pkgs.lib.inNixShell then drv.env else drv