"Chord Drill Sergeant" -> "Learn Piano Chords"

In the spirit of "keep it simple, stupid", I am naming this application as
closely to the functionality as I can imagine.

website/sandbox/learnpianochords/default.nix

@@ -0,0 +1,60 @@
+{ pkgs ? <nixpkgs>, ... }:
+
+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_10_x.uglify-js;
+
+      buildPhase = pkgs.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 = "learn-piano-chords";
+  buildInputs = [];
+  src = ./.;
+  buildPhase = ''
+    mkdir -p $out
+    cp index.html output.css ${mainDotElm}/Main.min.js $out
+  '';
+  dontInstall = true;
+}