# Copyright (c) 2022-2025, NVIDIA CORPORATION & AFFILIATES. All rights reserved.
#
# See LICENSE for license information.

"""PyTorch related extensions."""
import os
from pathlib import Path

import setuptools

from .utils import all_files_in_dir, cuda_version, get_cuda_include_dirs, debug_build_enabled


def setup_pytorch_extension(
    csrc_source_files,
    csrc_header_files,
    common_header_files,
) -> setuptools.Extension:
    """Setup CUDA extension for PyTorch support"""

    # Source files
    csrc_source_files = Path(csrc_source_files)
    extensions_dir = csrc_source_files / "extensions"
    sources = [
        csrc_source_files / "common.cpp",
    ] + all_files_in_dir(extensions_dir)

    # Header files
    include_dirs = get_cuda_include_dirs()
    include_dirs.extend(
        [
            common_header_files,
            common_header_files / "common",
            common_header_files / "common" / "include",
            csrc_header_files,
        ]
    )

    # Compiler flags
    cxx_flags = ["-O3", "-fvisibility=hidden"]
    if debug_build_enabled():
        cxx_flags.append("-g")
        cxx_flags.append("-UNDEBUG")
    else:
        cxx_flags.append("-g0")

    # Version-dependent CUDA options
    try:
        version = cuda_version()
    except FileNotFoundError:
        print("Could not determine CUDA version")
    else:
        if version < (12, 0):
            raise RuntimeError("Transformer Engine requires CUDA 12.0 or newer")

    if bool(int(os.getenv("NVTE_UB_WITH_MPI", "0"))):
        assert (
            os.getenv("MPI_HOME") is not None
        ), "MPI_HOME=/path/to/mpi must be set when compiling with NVTE_UB_WITH_MPI=1!"
        mpi_path = Path(os.getenv("MPI_HOME"))
        include_dirs.append(mpi_path / "include")
        cxx_flags.append("-DNVTE_UB_WITH_MPI")

    library_dirs = []
    libraries = []
    if bool(int(os.getenv("NVTE_ENABLE_NVSHMEM", 0))):
        assert (
            os.getenv("NVSHMEM_HOME") is not None
        ), "NVSHMEM_HOME must be set when compiling with NVTE_ENABLE_NVSHMEM=1"
        nvshmem_home = Path(os.getenv("NVSHMEM_HOME"))
        include_dirs.append(nvshmem_home / "include")
        library_dirs.append(nvshmem_home / "lib")
        libraries.append("nvshmem_host")
        cxx_flags.append("-DNVTE_ENABLE_NVSHMEM")

    # Construct PyTorch CUDA extension
    sources = [str(path) for path in sources]
    include_dirs = [str(path) for path in include_dirs]
    from torch.utils.cpp_extension import CppExtension

    return CppExtension(
        name="transformer_engine_torch",
        sources=[str(src) for src in sources],
        include_dirs=[str(inc) for inc in include_dirs],
        extra_compile_args={"cxx": cxx_flags},
        libraries=[str(lib) for lib in libraries],
        library_dirs=[str(lib_dir) for lib_dir in library_dirs],
    )
