depot/third_party/nixpkgs/pkgs/build-support/alternatives/lapack/default.nix

{ lib, stdenv
, lapack-reference, openblas
, isILP64 ? false
, lapackProvider ? openblas }:

let

  version = "3";
  canonicalExtension = if stdenv.hostPlatform.isLinux
                       then "${stdenv.hostPlatform.extensions.sharedLibrary}.${version}"
                       else stdenv.hostPlatform.extensions.sharedLibrary;

  lapackImplementation = lib.getName lapackProvider;
  lapackProvider' = if lapackImplementation == "mkl"
                  then lapackProvider
                  else lapackProvider.override { blas64 = isILP64; };

in

assert isILP64 -> lapackImplementation == "mkl" || lapackProvider'.blas64;

stdenv.mkDerivation {
  pname = "lapack";
  inherit version;

  outputs = [ "out" "dev" ];

  meta = (lapackProvider'.meta or {}) // {
    description = "${lib.getName lapackProvider'} with just the LAPACK C and FORTRAN ABI";
  };

  passthru = {
    inherit isILP64;
    provider = lapackProvider';
    implementation = lapackImplementation;
  };

  # TODO: drop this forced rebuild, as it was needed just once.
  rebuild_salt = if stdenv.isDarwin && stdenv.isx86_64 then "J4AQ" else null;

  dontBuild = true;
  dontConfigure = true;
  unpackPhase = "src=$PWD";

  dontPatchELF = true;

  installPhase = (''
  mkdir -p $out/lib $dev/include $dev/lib/pkgconfig

  liblapack="${lib.getLib lapackProvider'}/lib/liblapack${canonicalExtension}"

  if ! [ -e "$liblapack" ]; then
    echo "$liblapack does not exist, ${lapackProvider'.name} does not provide liblapack."
    exit 1
  fi

  cp -L "$liblapack" $out/lib/liblapack${canonicalExtension}
  chmod +w $out/lib/liblapack${canonicalExtension}

'' + (lib.optionalString (stdenv.hostPlatform.parsed.kernel.execFormat.name == "elf") ''
  patchelf --set-soname liblapack${canonicalExtension} $out/lib/liblapack${canonicalExtension}
  patchelf --set-rpath "$(patchelf --print-rpath $out/lib/liblapack${canonicalExtension}):${lapackProvider'}/lib" $out/lib/liblapack${canonicalExtension}
'') + ''

  if [ "$out/lib/liblapack${canonicalExtension}" != "$out/lib/liblapack${stdenv.hostPlatform.extensions.sharedLibrary}" ]; then
    ln -s $out/lib/liblapack${canonicalExtension} "$out/lib/liblapack${stdenv.hostPlatform.extensions.sharedLibrary}"
  fi

  install -D ${lib.getDev lapack-reference}/include/lapack.h $dev/include/lapack.h

  cat <<EOF > $dev/lib/pkgconfig/lapack.pc
Name: lapack
Version: ${version}
Description: LAPACK FORTRAN implementation
Cflags: -I$dev/include
Libs: -L$out/lib -llapack
EOF

  liblapacke="${lib.getLib lapackProvider'}/lib/liblapacke${canonicalExtension}"

  if ! [ -e "$liblapacke" ]; then
    echo "$liblapacke does not exist, ${lapackProvider'.name} does not provide liblapacke."
    exit 1
  fi

  cp -L "$liblapacke" $out/lib/liblapacke${canonicalExtension}
  chmod +w $out/lib/liblapacke${canonicalExtension}

'' + (lib.optionalString (stdenv.hostPlatform.parsed.kernel.execFormat.name == "elf") ''
  patchelf --set-soname liblapacke${canonicalExtension} $out/lib/liblapacke${canonicalExtension}
  patchelf --set-rpath "$(patchelf --print-rpath $out/lib/liblapacke${canonicalExtension}):${lib.getLib lapackProvider'}/lib" $out/lib/liblapacke${canonicalExtension}
'') + ''

  if [ -f "$out/lib/liblapacke.so.3" ]; then
    ln -s $out/lib/liblapacke.so.3 $out/lib/liblapacke.so
  fi

  cp ${lib.getDev lapack-reference}/include/lapacke{,_mangling,_config,_utils}.h $dev/include

  cat <<EOF > $dev/lib/pkgconfig/lapacke.pc
Name: lapacke
Version: ${version}
Description: LAPACK C implementation
Cflags: -I$dev/include
Libs: -L$out/lib -llapacke
EOF
'' + lib.optionalString (lapackImplementation == "mkl") ''
  mkdir -p $out/nix-support
  echo 'export MKL_INTERFACE_LAYER=${lib.optionalString isILP64 "I"}LP64,GNU' > $out/nix-support/setup-hook
  ln -s $out/lib/liblapack${canonicalExtension} $out/lib/libmkl_rt${stdenv.hostPlatform.extensions.sharedLibrary}
  ln -sf ${lapackProvider'}/include/* $dev/include
'');
}