import os
import torch
import warnings
from typing import Optional
from tilelang.contrib import nvcc
from torch.utils.cpp_extension import load, _import_module_from_library
from tilelang import env

# Define paths
compress_util = os.path.join(env.TILELANG_TEMPLATE_PATH, "tl_templates/cuda/compress_sm90.cu")
# Cache directory for compiled extensions
_CACHE_DIR = os.path.join(env.TILELANG_CACHE_DIR, "sparse_compressor")
os.makedirs(_CACHE_DIR, exist_ok=True)


def _get_cached_lib():
    name = 'compress_lib'
    cached_path = os.path.join(_CACHE_DIR, f"{name}.so")

    if os.path.exists(cached_path):
        try:
            return _import_module_from_library(name, cached_path)
        except Exception:
            # If loading fails, recompile
            pass

    # Set TORCH_CUDA_ARCH_LIST
    env._initialize_torch_cuda_arch_flags()

    # Compile if not cached or loading failed
    return load(
        name=name,
        sources=[compress_util],
        extra_cuda_cflags=[
            '-O2',
            '-std=c++17',
            '-lineinfo',
            f'-I{env.CUTLASS_INCLUDE_DIR}',
            f'-I{env.CUTLASS_INCLUDE_DIR}/../tools/util/include',
            '-arch=sm_90',
        ],
        build_directory=_CACHE_DIR,
    )


def compress_sm90(A: torch.Tensor, block_k: int,
                  transposed: bool) -> tuple[torch.Tensor, torch.Tensor]:
    if block_k > 128:
        block_k = 128
        # Ref: https://github.com/NVIDIA/cutlass/blob/c2ad7c5b20f131c4ba33601860f1da3f9c9df0f3/include/cutlass/gemm/collective/builders/sm90_sparse_gmma_builder.inl#L145-L146
        warnings.warn(
            f"block_k {block_k} is too large, set to 128 for sm90 compression.", stacklevel=2)
    # Load the library (will use cache if available)
    compress_lib = _get_cached_lib()

    return compress_lib.compress_sm90(A, block_k, transposed)


def compress_sm80(A: torch.Tensor, transposed: bool) -> tuple[torch.Tensor, torch.Tensor]:
    try:
        from torch.sparse import to_sparse_semi_structured, SparseSemiStructuredTensor
    except ImportError as err:
        raise ImportError("SparseSemiStructuredTensor is not available in this version of PyTorch. "
                          "Please install a compatible version.") from err
    orig_val = SparseSemiStructuredTensor._FORCE_CUTLASS
    try:
        SparseSemiStructuredTensor._FORCE_CUTLASS = True
        if transposed is not False:
            raise NotImplementedError("transposed flag is deprecated by pytorch")
        compressed = to_sparse_semi_structured(A)
        return compressed.packed, compressed.meta
    finally:
        SparseSemiStructuredTensor._FORCE_CUTLASS = orig_val


def compress(A: torch.Tensor,
             transposed: bool,
             arch: Optional[str] = None,
             **kwargs) -> tuple[torch.Tensor, torch.Tensor]:
    """
    Compress a tensor using the appropriate method based on the CUDA architecture.
    """
    if arch is None:
        arch = nvcc.get_target_compute_version()

    compute_version = nvcc.parse_compute_version(arch)

    if compute_version >= (9, 0):
        return compress_sm90(A, transposed=transposed, **kwargs)
    elif compute_version >= (8, 0):
        return compress_sm80(A, transposed=transposed)
    else:
        raise ValueError(f"Unsupported CUDA compute version: {compute_version}. "
                         "Supported versions are sm_80 and sm_90.")
