shell.nix

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

let

  inherit (nixpkgs) pkgs;

  f = { mkDerivation, aeson, aeson-pretty, base, base16-bytestring
      , bytestring, containers, cryptohash-sha1, directory
      , directory-tree, filepath, hlibgit2, hspec, lens, lib
      , optparse-applicative, pandoc, pcre-heavy, pcre-light, QuickCheck
      , text
      }:
      mkDerivation {
        pname = "answers-script";
        version = "0.1.0.0";
        src = ./.;
        isLibrary = true;
        isExecutable = true;
        libraryHaskellDepends = [
          aeson aeson-pretty base base16-bytestring bytestring containers
          cryptohash-sha1 directory directory-tree filepath hlibgit2 lens
          pandoc pcre-heavy pcre-light text
        ];
        executableHaskellDepends = [ base optparse-applicative ];
        testHaskellDepends = [
          base bytestring directory directory-tree filepath hspec QuickCheck
        ];
        doCheck = false;
        license = "unknown";
        mainProgram = "answers-script";
      };

  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