make affection dependency and nixify

cabal.project

@@ -0,0 +1,3 @@
+packages:
+  ./
+  ./extern/*/

pituicat.cabal

@@ -20,5 +20,6 @@ executable pituicat
   -- other-modules:
   -- other-extensions:
   build-depends:       base ^>=4.13.0.0
+                     , affection
   hs-source-dirs:      src
   default-language:    Haskell2010

shell.nix

@@ -0,0 +1,48 @@
+{ nixpkgs ? import <nixpkgs> {}, compiler ? "default", doBenchmark ? false }:
+
+let
+
+  inherit (nixpkgs) pkgs;
+
+  affection = with haskellPackages; callPackage(
+    { mkDerivation, base, bytestring, clock, containers, glib, linear
+    , monad-loops, monad-parallel, mtl, OpenGL, sdl2, stdenv, stm, text
+    , uuid, vector
+    }:
+    mkDerivation {
+      pname = "affection";
+      version = "0.0.0.10";
+      src = ./extern/affection;
+      isLibrary = true;
+      isExecutable = true;
+      libraryHaskellDepends = [
+        base bytestring clock containers glib linear monad-loops
+        monad-parallel mtl OpenGL sdl2 stm text uuid vector
+      ];
+      homepage = "https://github.com/nek0/affection#readme";
+      description = "A simple Game Engine using SDL";
+      license = stdenv.lib.licenses.lgpl3;
+    }) {};
+
+  f = { mkDerivation, base, stdenv }:
+      mkDerivation {
+        pname = "pituicat";
+        version = "0.0.0.0";
+        src = ./.;
+        isLibrary = false;
+        isExecutable = true;
+        executableHaskellDepends = [ affection base ];
+        license = stdenv.lib.licenses.gpl3;
+      };
+
+  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