{ lib, stdenv, fetchurl, nspr, perl, zlib
, sqlite, ninja
, darwin, fixDarwinDylibNames, buildPackages
, useP11kit ? true, p11-kit
, # allow FIPS mode. Note that this makes the output non-reproducible.
  # https://developer.mozilla.org/en-US/docs/Mozilla/Projects/NSS/NSS_Tech_Notes/nss_tech_note6
  enableFIPS ? false
}:

let
  nssPEM = fetchurl {
    url = "http://dev.gentoo.org/~polynomial-c/mozilla/nss-3.15.4-pem-support-20140109.patch.xz";
    sha256 = "10ibz6y0hknac15zr6dw4gv9nb5r5z9ym6gq18j3xqx7v7n3vpdw";
  };

  # NOTE: Whenever you updated this version check if the `cacert` package also
  #       needs an update. You can run the regular updater script for cacerts.
  #       It will rebuild itself using the version of this package (NSS) and if
  #       an update is required do the required changes to the expression.
  #       Example: nix-shell ./maintainers/scripts/update.nix --argstr package cacert
  version = "3.64";
  underscoreVersion = builtins.replaceStrings ["."] ["_"] version;

in stdenv.mkDerivation rec {
  pname = "nss";
  inherit version;

  src = fetchurl {
    url = "mirror://mozilla/security/nss/releases/NSS_${underscoreVersion}_RTM/src/${pname}-${version}.tar.gz";
    sha256 = "09hivz4qf3dw7m21lshw34l0yncinwn4ax5w3rpkm71f2wkm85yk";
  };

  depsBuildBuild = [ buildPackages.stdenv.cc ];

  nativeBuildInputs = [ perl ninja (buildPackages.python3.withPackages (ps: with ps; [ gyp ])) ]
    ++ lib.optionals stdenv.hostPlatform.isDarwin [ darwin.cctools fixDarwinDylibNames ];

  buildInputs = [ zlib sqlite ];

  propagatedBuildInputs = [ nspr ];

  prePatch = ''
    # strip the trailing whitespace from the patch line and the renamed CKO_NETSCAPE_ enum to CKO_NSS_
    xz -d < ${nssPEM} | sed \
       -e 's/-DIRS = builtins $/-DIRS = . builtins/g' \
       -e 's/CKO_NETSCAPE_/CKO_NSS_/g' \
       -e 's/CKT_NETSCAPE_/CKT_NSS_/g' \
       | patch -p1

    patchShebangs nss

    for f in nss/coreconf/config.gypi nss/build.sh nss/coreconf/config.gypi; do
      substituteInPlace "$f" --replace "/usr/bin/env" "${buildPackages.coreutils}/bin/env"
    done

    substituteInPlace nss/coreconf/config.gypi --replace "/usr/bin/grep" "${buildPackages.coreutils}/bin/env grep"
  '';

  patches =
    [
      # Based on http://patch-tracker.debian.org/patch/series/dl/nss/2:3.15.4-1/85_security_load.patch
      ./85_security_load.patch
      ./ckpem.patch
      ./fix-cross-compilation.patch
    ];

  patchFlags = [ "-p0" ];

  postPatch = lib.optionalString stdenv.hostPlatform.isDarwin ''
     substituteInPlace nss/coreconf/Darwin.mk --replace '@executable_path/$(notdir $@)' "$out/lib/\$(notdir \$@)"
     substituteInPlace nss/coreconf/config.gypi --replace "'DYLIB_INSTALL_NAME_BASE': '@executable_path'" "'DYLIB_INSTALL_NAME_BASE': '$out/lib'"
   '';

  outputs = [ "out" "dev" "tools" ];

  preConfigure = "cd nss";

  buildPhase = let
    getArch = platform: if platform.isx86_64 then "x64"
          else if platform.isx86_32 then "ia32"
          else if platform.isAarch32 then "arm"
          else if platform.isAarch64 then "arm64"
          else if platform.isPower && platform.is64bit then (
            if platform.isLittleEndian then "ppc64le" else "ppc64"
          )
          else platform.parsed.cpu.name;
    # yes, this is correct. nixpkgs uses "host" for the platform the binary will run on whereas nss uses "host" for the platform that the build is running on
    target = getArch stdenv.hostPlatform;
    host = getArch stdenv.buildPlatform;
  in ''
    runHook preBuild

    sed -i 's|nss_dist_dir="$dist_dir"|nss_dist_dir="'$out'"|;s|nss_dist_obj_dir="$obj_dir"|nss_dist_obj_dir="'$out'"|' build.sh
    ./build.sh -v --opt \
      --with-nspr=${nspr.dev}/include:${nspr.out}/lib \
      --system-sqlite \
      --enable-legacy-db \
      --target ${target} \
      -Dhost_arch=${host} \
      -Duse_system_zlib=1 \
      --enable-libpkix \
      ${lib.optionalString enableFIPS "--enable-fips"} \
      ${lib.optionalString stdenv.isDarwin "--clang"} \
      ${lib.optionalString (stdenv.hostPlatform != stdenv.buildPlatform) "--disable-tests"}

    runHook postBuild
  '';

  NIX_CFLAGS_COMPILE = "-Wno-error -DNIX_NSS_LIBDIR=\"${placeholder "out"}/lib/\"";

  installPhase = ''
    runHook preInstall

    rm -rf $out/private
    find $out -name "*.TOC" -delete
    mv $out/public $out/include

    ln -s lib $out/lib64

    # Upstream issue: https://bugzilla.mozilla.org/show_bug.cgi?id=530672
    # https://gitweb.gentoo.org/repo/gentoo.git/plain/dev-libs/nss/files/nss-3.32-gentoo-fixups.patch?id=af1acce6c6d2c3adb17689261dfe2c2b6771ab8a
    NSS_MAJOR_VERSION=`grep "NSS_VMAJOR" lib/nss/nss.h | awk '{print $3}'`
    NSS_MINOR_VERSION=`grep "NSS_VMINOR" lib/nss/nss.h | awk '{print $3}'`
    NSS_PATCH_VERSION=`grep "NSS_VPATCH" lib/nss/nss.h | awk '{print $3}'`
    PREFIX="$out"

    mkdir -p $out/lib/pkgconfig
    sed -e "s,%prefix%,$PREFIX," \
        -e "s,%exec_prefix%,$PREFIX," \
        -e "s,%libdir%,$PREFIX/lib64," \
        -e "s,%includedir%,$dev/include/nss," \
        -e "s,%NSS_VERSION%,$NSS_MAJOR_VERSION.$NSS_MINOR_VERSION.$NSS_PATCH_VERSION,g" \
        -e "s,%NSPR_VERSION%,4.16,g" \
        pkg/pkg-config/nss.pc.in > $out/lib/pkgconfig/nss.pc
    chmod 0644 $out/lib/pkgconfig/nss.pc

    sed -e "s,@prefix@,$PREFIX," \
        -e "s,@MOD_MAJOR_VERSION@,$NSS_MAJOR_VERSION," \
        -e "s,@MOD_MINOR_VERSION@,$NSS_MINOR_VERSION," \
        -e "s,@MOD_PATCH_VERSION@,$NSS_PATCH_VERSION," \
        pkg/pkg-config/nss-config.in > $out/bin/nss-config
    chmod 0755 $out/bin/nss-config
  '';

  postInstall = lib.optionalString useP11kit ''
    # Replace built-in trust with p11-kit connection
    ln -sf ${p11-kit}/lib/pkcs11/p11-kit-trust.so $out/lib/libnssckbi.so
  '';

  postFixup = let
    isCross = stdenv.hostPlatform != stdenv.buildPlatform;
    nss = if isCross then buildPackages.nss.tools else "$out";
  in
  (lib.optionalString enableFIPS (''
    for libname in freebl3 nssdbm3 softokn3
    do '' +
    (if stdenv.isDarwin
     then ''
       libfile="$out/lib/lib$libname.dylib"
       DYLD_LIBRARY_PATH=$out/lib:${nspr.out}/lib \
     '' else ''
       libfile="$out/lib/lib$libname.so"
       LD_LIBRARY_PATH=$out/lib:${nspr.out}/lib \
     '') + ''
        ${nss}/bin/shlibsign -v -i "$libfile"
    done
  '')) +
  ''
    moveToOutput bin "$tools"
    moveToOutput bin/nss-config "$dev"
    moveToOutput lib/libcrmf.a "$dev" # needed by firefox, for example
    rm -f "$out"/lib/*.a

    runHook postInstall
  '';

  meta = with lib; {
    homepage = "https://developer.mozilla.org/en-US/docs/NSS";
    description = "A set of libraries for development of security-enabled client and server applications";
    license = licenses.mpl20;
    platforms = platforms.all;
  };
}