# Copyright 1999-2026 Gentoo Authors
# Distributed under the terms of the GNU General Public License v2

EAPI=8

DISTUTILS_USE_PEP517=setuptools
PYTHON_COMPAT=( python3_{12..13} )
DISTUTILS_SINGLE_IMPL=1

inherit distutils-r1 cuda

DESCRIPTION="Modular primitives for high-performance differentiable rendering"
HOMEPAGE="https://github.com/NVlabs/nvdiffrast"
SRC_URI="https://github.com/NVlabs/nvdiffrast/archive/refs/tags/v${PV}.tar.gz -> ${P}.gh.tar.gz"

LICENSE="NVIDIA-nvdiffrast"
SLOT="0"
KEYWORDS="~amd64"
# NVIDIA Source Code License (non-commercial): no mirroring / binary redist.
RESTRICT="bindist mirror"

# nvdiffrast 0.4.0 compiles its CUDA ops (_nvdiffrast_c) at build time via
# torch's cpp_extension (older versions JIT'd at first use). torch reads CC/CXX
# for nvcc's -ccbin, so pin them to the cuda-eclass gcc (<=15 for CUDA 13.x).
# ninja stays a runtime dep for the GL-context plugin nvdiffrast still JITs.
RDEPEND="
	sci-ml/caffe2[${PYTHON_SINGLE_USEDEP}]
	app-alternatives/ninja
	$(python_gen_cond_dep '
		dev-python/numpy[${PYTHON_USEDEP}]
	')
"
DEPEND="${RDEPEND}"
BDEPEND="
	app-alternatives/ninja
	$(python_gen_cond_dep '
		>=dev-python/setuptools-64[${PYTHON_USEDEP}]
		dev-python/wheel[${PYTHON_USEDEP}]
	')
"

src_prepare() {
	distutils-r1_src_prepare
}

src_compile() {
	local gccdir
	gccdir=$(cuda_gccdir) || die
	export CC="${gccdir}/gcc" CXX="${gccdir}/g++"
	# Build only for the GPU(s) actually present. An explicit
	# TORCH_CUDA_ARCH_LIST (e.g. from make.conf) always wins; otherwise
	# probe the native compute capability with nvcc's device query
	# (e.g. 86 -> 8.6) so each host compiles just what it can run. If no
	# GPU is visible at build time (headless / binhost), leave it unset
	# and let torch's cpp_extension fall back to its full arch list.
	if [[ -z ${TORCH_CUDA_ARCH_LIST} ]]; then
		cuda_add_sandbox -w
		local native_cc
		native_cc=$(__nvcc_device_query 2>/dev/null)
		[[ ${native_cc} =~ ^[0-9]{2,}$ ]] &&
			export TORCH_CUDA_ARCH_LIST="${native_cc%?}.${native_cc: -1}"
	fi
	export FORCE_CUDA=1 MAX_JOBS="${MAX_JOBS:-4}"

	distutils-r1_src_compile
}