{ config, pkgs, ... }:

let
  dependencies = pkgs: with pkgs; [ filepath
                                    directory
                                    cryptonite
                                    bytestring
                                    uuid
                                    aeson
                                    aeson-pretty
                                    mtl
                                  ];

in rec {
  nixpkgs.overlays = [(self: super: {
    mlmmj-exposed = super.stdenv.mkDerivation rec {
      name = "mlmmj-expose";
      
      src = ./mlmmj-expose;

      phases = [ "unpackPhase" "patchPhase" "buildPhase" "installPhase" ];

      env = self.haskellPackages.ghcWithPackages dependencies;
      import (pkgs) mlmmj;

      patchPhase = ''
        substituteAllInPlace mlmmj-expose.hs
      '';

      buildPhase = ''
        ${env}/bin/ghc -o mlmmj-expose -odir . -hidir . mlmmj-expose.hs
      '';

      installPhase = ''
        mkdir -p $out/bin
        cp mlmmj-expose $out/bin/.mlmmj-expose

        for f in mlmmj-exposed mlmmj-expose mlmmj-get-exposed mlmmj-serve-exposed; do
          ln -s .mlmmj-expose $out/bin/$f
        done
      '';
    };
  })];
  environment.systemPackages = with pkgs; [ mlmmj-exposed ];
}