{ stdenv, targetPackages
, buildPlatform, hostPlatform, targetPlatform

# build-tools
, bootPkgs, alex, happy
, autoconf, automake, coreutils, fetchgit, perl, python3

, libiconv ? null, ncurses

, # If enabled, GHC will be built with the GPL-free but slower integer-simple
  # library instead of the faster but GPLed integer-gmp library.
  enableIntegerSimple ? false, gmp ? null

, version ? "8.4.20180115"
}:

assert !enableIntegerSimple -> gmp != null;

let
  inherit (bootPkgs) ghc;

  rev = "3e3a096885c0fcd0703edbeffb4e47f5cbd8f4cc";

  # TODO(@Ericson2314) Make unconditional
  targetPrefix = stdenv.lib.optionalString
    (targetPlatform != hostPlatform)
    "${targetPlatform.config}-";

  buildMK = stdenv.lib.optionalString enableIntegerSimple ''
    INTEGER_LIBRARY = integer-simple
  '' + stdenv.lib.optionalString (targetPlatform != hostPlatform) ''
    BuildFlavour = perf-cross
  '';
in
stdenv.mkDerivation rec {
  inherit version rev;
  name = "${targetPrefix}ghc-${version}";

  src = fetchgit {
    url = "git://git.haskell.org/ghc.git";
    inherit rev;
    sha256 = "06slymbsd7vsfp4hh40v7cxf7nmp0kvlni2wfq7ag5wlqh04slgs";
  };

  postPatch = "patchShebangs .";

  preConfigure = ''
    echo -n "${buildMK}" > mk/build.mk
    echo ${version} >VERSION
    echo ${rev} >GIT_COMMIT_ID
    ./boot
    sed -i -e 's|-isysroot /Developer/SDKs/MacOSX10.5.sdk||' configure
  '' + stdenv.lib.optionalString (!stdenv.isDarwin) ''
    export NIX_LDFLAGS+=" -rpath $out/lib/ghc-${version}"
  '' + stdenv.lib.optionalString stdenv.isDarwin ''
    export NIX_LDFLAGS+=" -no_dtrace_dof"
  '';

  buildInputs = [ ghc perl autoconf automake happy alex python3 ];

  enableParallelBuilding = true;

  configureFlags = [
    "CC=${stdenv.cc}/bin/cc"
    "--with-curses-includes=${ncurses.dev}/include" "--with-curses-libraries=${ncurses.out}/lib"
    "--datadir=$doc/share/doc/ghc"
  ] ++ stdenv.lib.optional (! enableIntegerSimple) [
    "--with-gmp-includes=${gmp.dev}/include" "--with-gmp-libraries=${gmp.out}/lib"
  ] ++ stdenv.lib.optional stdenv.isDarwin [
    "--with-iconv-includes=${libiconv}/include" "--with-iconv-libraries=${libiconv}/lib"
  ];

  # required, because otherwise all symbols from HSffi.o are stripped, and
  # that in turn causes GHCi to abort
  stripDebugFlags = [ "-S" ] ++ stdenv.lib.optional (!targetPlatform.isDarwin) "--keep-file-symbols";

  checkTarget = "test";

  postInstall = ''
    paxmark m $out/lib/${name}/bin/${if targetPlatform != hostPlatform then "ghc" else "{ghc,haddock}"}

    # Install the bash completion file.
    install -D -m 444 utils/completion/ghc.bash $out/share/bash-completion/completions/${targetPrefix}ghc

    # Patch scripts to include "readelf" and "cat" in $PATH.
    for i in "$out/bin/"*; do
      test ! -h $i || continue
      egrep --quiet '^#!' <(head -n 1 $i) || continue
      sed -i -e '2i export PATH="$PATH:${stdenv.lib.makeBinPath [ targetPackages.stdenv.cc.bintools coreutils ]}"' $i
    done
  '';

  outputs = [ "out" "doc" ];

  passthru = {
    inherit bootPkgs targetPrefix;
  };

  meta = {
    homepage = http://haskell.org/ghc;
    description = "The Glasgow Haskell Compiler";
    maintainers = with stdenv.lib.maintainers; [ marcweber andres peti ];
    inherit (ghc.meta) license platforms;
  };

}