{ pkgs, ... }:

with pkgs;

let
  mkDerivation =
    { srcs ? ./elm-srcs.nix
    , src
    , name
    , srcdir ? "./src"
    , targets ? []
    , registryDat ? ./registry.dat
    , outputJavaScript ? false
    }:
    stdenv.mkDerivation {
      inherit name src;

      buildInputs = [ elmPackages.elm ]
        ++ lib.optional outputJavaScript nodePackages.uglify-js;

      buildPhase = elmPackages.fetchElmDeps {
        elmPackages = import srcs;
        elmVersion = "0.19.1";
        inherit registryDat;
      };

      installPhase = let
        elmfile = module: "${srcdir}/${builtins.replaceStrings ["."] ["/"] module}.elm";
        extension = if outputJavaScript then "js" else "html";
      in ''
        mkdir -p $out/share/doc
        ${lib.concatStrings (map (module: ''
          echo "compiling ${elmfile module}"
          elm make ${elmfile module} --output $out/${module}.${extension} --docs $out/share/doc/${module}.json
          ${lib.optionalString outputJavaScript ''
            echo "minifying ${elmfile module}"
            uglifyjs $out/${module}.${extension} --compress 'pure_funcs="F2,F3,F4,F5,F6,F7,F8,F9,A2,A3,A4,A5,A6,A7,A8,A9",pure_getters,keep_fargs=false,unsafe_comps,unsafe' \
                | uglifyjs --mangle --output $out/${module}.min.${extension}
          ''}
        '') targets)}
      '';
    };
  mainDotElm = mkDerivation {
    name = "elm-app-0.1.0";
    srcs = ./elm-srcs.nix;
    src = ./.;
    targets = ["Main"];
    srcdir = "./src";
    outputJavaScript = true;
  };
in stdenv.mkDerivation {
  name = "habit-screens";
  buildInputs = [];
  src = builtins.path { path = ./.; name = "habit-screens"; };
  buildPhase = ''
    mkdir -p $out
    cp index.html output.css ${mainDotElm}/Main.min.js $out
  '';
  dontInstall = true;
}