{ lib, stdenv, fetchurl, flex, bison, python3, autoreconfHook, gnulib, libtool, bash
, gettext, ncurses, libusb-compat-0_1, freetype, qemu, lvm2, unifont, pkg-config
, buildPackages
, fetchpatch
, pkgsBuildBuild
, nixosTests
, fuse # only needed for grub-mount
, runtimeShell
, zfs ? null
, efiSupport ? false
, zfsSupport ? false
, xenSupport ? false
, kbdcompSupport ? false, ckbcomp
}:

with lib;
let
  pcSystems = {
    i686-linux.target = "i386";
    x86_64-linux.target = "i386";
  };

  efiSystemsBuild = {
    i686-linux.target = "i386";
    x86_64-linux.target = "x86_64";
    armv7l-linux.target = "arm";
    aarch64-linux.target = "aarch64";
  };

  # For aarch64, we need to use '--target=aarch64-efi' when building,
  # but '--target=arm64-efi' when installing. Insanity!
  efiSystemsInstall = {
    i686-linux.target = "i386";
    x86_64-linux.target = "x86_64";
    armv7l-linux.target = "arm";
    aarch64-linux.target = "arm64";
  };

  canEfi = any (system: stdenv.hostPlatform.system == system) (mapAttrsToList (name: _: name) efiSystemsBuild);
  inPCSystems = any (system: stdenv.hostPlatform.system == system) (mapAttrsToList (name: _: name) pcSystems);

  version = "2.06";

in (

assert efiSupport -> canEfi;
assert zfsSupport -> zfs != null;
assert !(efiSupport && xenSupport);

stdenv.mkDerivation rec {
  pname = "grub";
  inherit version;

  src = fetchurl {
    url = "mirror://gnu/grub/grub-${version}.tar.xz";
    sha256 = "sha256-t56kSvkbk9F80/6Ava5u1DdwZ4qaWuGSzOqAPrtlfuE=";
  };

  patches = [
    ./fix-bash-completion.patch
    (fetchpatch {
      name = "Add-hidden-menu-entries.patch";
      # https://lists.gnu.org/archive/html/grub-devel/2016-04/msg00089.html
      url = "https://marc.info/?l=grub-devel&m=146193404929072&q=mbox";
      sha256 = "00wa1q5adiass6i0x7p98vynj9vsz1w0gn1g4dgz89v35mpyw2bi";
    })

    # Pull upstream patch to fix linkage against binutils-2.36.
    (fetchpatch {
      name = "binutils-2.36";
      url = "https://git.savannah.gnu.org/cgit/grub.git/patch/?id=b98275138bf4fc250a1c362dfd2c8b1cf2421701";
      sha256 = "001m058bsl2pcb0ii84jfm5ias8zgzabrfy6k2cc9w6w1y51ii82";
    })
  ];

  postPatch = if kbdcompSupport then ''
    sed -i util/grub-kbdcomp.in -e 's@\bckbcomp\b@${ckbcomp}/bin/ckbcomp@'
  '' else ''
    echo '#! ${runtimeShell}' > util/grub-kbdcomp.in
    echo 'echo "Compile grub2 with { kbdcompSupport = true; } to enable support for this command."' >> util/grub-kbdcomp.in
  '';

  depsBuildBuild = [ buildPackages.stdenv.cc ];
  nativeBuildInputs = [ bison flex python3 pkg-config gettext freetype autoreconfHook ];
  buildInputs = [ ncurses libusb-compat-0_1 freetype lvm2 fuse libtool bash ]
    ++ optional doCheck qemu
    ++ optional zfsSupport zfs;

  strictDeps = true;

  hardeningDisable = [ "all" ];

  separateDebugInfo = !xenSupport;

  # Work around a bug in the generated flex lexer (upstream flex bug?)
  NIX_CFLAGS_COMPILE = "-Wno-error";

  preConfigure =
    '' for i in "tests/util/"*.in
       do
         sed -i "$i" -e's|/bin/bash|${stdenv.shell}|g'
       done

       # Apparently, the QEMU executable is no longer called
       # `qemu-system-i386', even on i386.
       #
       # In addition, use `-nodefaults' to avoid errors like:
       #
       #  chardev: opening backend "stdio" failed
       #  qemu: could not open serial device 'stdio': Invalid argument
       #
       # See <http://www.mail-archive.com/qemu-devel@nongnu.org/msg22775.html>.
       sed -i "tests/util/grub-shell.in" \
           -e's/qemu-system-i386/qemu-system-x86_64 -nodefaults/g'

      unset CPP # setting CPP intereferes with dependency calculation

      patchShebangs .

      substituteInPlace ./configure --replace '/usr/share/fonts/unifont' '${unifont}/share/fonts'
    '';

  configureFlags = [
    "--enable-grub-mount" # dep of os-prober
  ] ++ optionals (stdenv.hostPlatform != stdenv.buildPlatform) [
    # grub doesn't do cross-compilation as usual and tries to use unprefixed
    # tools to target the host. Provide toolchain information explicitly for
    # cross builds.
    #
    # Ref: # https://github.com/buildroot/buildroot/blob/master/boot/grub2/grub2.mk#L108
    "TARGET_CC=${stdenv.cc.targetPrefix}cc"
    "TARGET_NM=${stdenv.cc.targetPrefix}nm"
    "TARGET_OBJCOPY=${stdenv.cc.targetPrefix}objcopy"
    "TARGET_RANLIB=${stdenv.cc.targetPrefix}ranlib"
    "TARGET_STRIP=${stdenv.cc.targetPrefix}strip"
  ] ++ optional zfsSupport "--enable-libzfs"
    ++ optionals efiSupport [ "--with-platform=efi" "--target=${efiSystemsBuild.${stdenv.hostPlatform.system}.target}" "--program-prefix=" ]
    ++ optionals xenSupport [ "--with-platform=xen" "--target=${efiSystemsBuild.${stdenv.hostPlatform.system}.target}"];

  # save target that grub is compiled for
  grubTarget = if efiSupport
               then "${efiSystemsInstall.${stdenv.hostPlatform.system}.target}-efi"
               else if inPCSystems
                    then "${pcSystems.${stdenv.hostPlatform.system}.target}-pc"
                    else "";

  doCheck = false;
  enableParallelBuilding = true;

  postInstall = ''
    # Avoid a runtime reference to gcc
    sed -i $out/lib/grub/*/modinfo.sh -e "/grub_target_cppflags=/ s|'.*'|' '|"
    # just adding bash to buildInputs wasn't enough to fix the shebang
    substituteInPlace $out/lib/grub/*/modinfo.sh \
      --replace ${buildPackages.bash} "/usr/bin/bash"
  '';

  passthru.tests = {
    nixos-grub = nixosTests.grub;
    nixos-install-simple = nixosTests.installer.simple;
    nixos-install-grub1 = nixosTests.installer.grub1;
    nixos-install-grub-uefi = nixosTests.installer.simpleUefiGrub;
    nixos-install-grub-uefi-spec = nixosTests.installer.simpleUefiGrubSpecialisation;
  };

  meta = with lib; {
    description = "GNU GRUB, the Grand Unified Boot Loader (2.x beta)";

    longDescription =
      '' GNU GRUB is a Multiboot boot loader. It was derived from GRUB, GRand
         Unified Bootloader, which was originally designed and implemented by
         Erich Stefan Boleyn.

         Briefly, the boot loader is the first software program that runs when a
         computer starts.  It is responsible for loading and transferring
         control to the operating system kernel software (such as the Hurd or
         the Linux).  The kernel, in turn, initializes the rest of the
         operating system (e.g., GNU).
      '';

    homepage = "https://www.gnu.org/software/grub/";

    license = licenses.gpl3Plus;

    platforms = platforms.gnu ++ platforms.linux;

    maintainers = [ maintainers.samueldr ];
  };
})