"""
Setup script for BitLinear PyTorch extension.

This script builds the C++/CUDA extension using PyTorch's built-in
cpp_extension utilities. It handles:
    - CPU-only builds (development)
    - CUDA builds (production)
    - Conditional compilation based on CUDA availability
"""

import os
import torch
from setuptools import setup, find_packages
from torch.utils.cpp_extension import (
    BuildExtension,
    CppExtension,
    CUDAExtension,
    CUDA_HOME,
)

# Package metadata
VERSION = "0.1.0"
DESCRIPTION = "BitLinear: Ultra-Low-Precision Linear Layers for PyTorch"
LONG_DESCRIPTION = """
A research-grade PyTorch extension for ultra-low-precision (1.58-bit) ternary 
linear layers inspired by BitNet and recent JMLR work on ternary representations 
of neural networks.

Features:
- Drop-in replacement for nn.Linear with ternary weights
- 20x memory compression
- Optimized CUDA kernels for GPU acceleration
- Greedy ternary decomposition for improved expressiveness
"""

# Determine if CUDA is available
def cuda_is_available():
    """Check if CUDA is available for compilation."""
    return torch.cuda.is_available() and CUDA_HOME is not None


def get_extensions():
    """
    Build extension modules based on CUDA availability.
    
    Returns:
        List of extension modules to compile
    """
    # Source files
    source_dir = os.path.join("bitlinear", "cpp")
    sources = [os.path.join(source_dir, "bitlinear.cpp")]
    
    # Compiler flags
    extra_compile_args = {
        "cxx": ["-O3", "-std=c++17"],
    }
    
    # Define macros
    define_macros = []
    
    if cuda_is_available():
        print("CUDA detected, building with GPU support")
        
        # Add CUDA source
        sources.append(os.path.join(source_dir, "bitlinear_kernel.cu"))
        
        # CUDA compiler flags
        extra_compile_args["nvcc"] = [
            "-O3",
            "-std=c++17",
            "--use_fast_math",
            "-gencode=arch=compute_70,code=sm_70",  # V100
            "-gencode=arch=compute_75,code=sm_75",  # T4, RTX 20xx
            "-gencode=arch=compute_80,code=sm_80",  # A100
            "-gencode=arch=compute_86,code=sm_86",  # RTX 30xx
            "-gencode=arch=compute_89,code=sm_89",  # RTX 40xx
            "-gencode=arch=compute_90,code=sm_90",  # H100
        ]
        
        # Define CUDA macro
        define_macros.append(("WITH_CUDA", None))
        
        # Create CUDA extension
        extension = CUDAExtension(
            name="bitlinear_cpp",
            sources=sources,
            extra_compile_args=extra_compile_args,
            define_macros=define_macros,
        )
    else:
        print("CUDA not detected, building CPU-only version")
        
        # Create CPU-only extension
        extension = CppExtension(
            name="bitlinear_cpp",
            sources=sources,
            extra_compile_args=extra_compile_args["cxx"],
            define_macros=define_macros,
        )
    
    return [extension]


# Read requirements
def read_requirements():
    """Read requirements from requirements.txt if it exists."""
    req_file = "requirements.txt"
    if os.path.exists(req_file):
        with open(req_file, "r") as f:
            return [line.strip() for line in f if line.strip() and not line.startswith("#")]
    return []


# Main setup
setup(
    name="bitlinear",
    version=VERSION,
    author="BitLinear Contributors",
    description=DESCRIPTION,
    long_description=LONG_DESCRIPTION,
    long_description_content_type="text/markdown",
    url="https://github.com/yourusername/bitlinear",  # TODO: Update with actual repo
    packages=find_packages(),
    ext_modules=get_extensions(),
    cmdclass={
        "build_ext": BuildExtension.with_options(no_python_abi_suffix=True)
    },
    install_requires=[
        "torch>=2.0.0",
        "numpy>=1.20.0",
    ],
    extras_require={
        "dev": [
            "pytest>=7.0.0",
            "pytest-cov>=4.0.0",
            "black>=22.0.0",
            "flake8>=5.0.0",
            "mypy>=0.990",
        ],
        "test": [
            "pytest>=7.0.0",
            "pytest-cov>=4.0.0",
        ],
    },
    python_requires=">=3.8",
    classifiers=[
        "Development Status :: 3 - Alpha",
        "Intended Audience :: Science/Research",
        "Topic :: Scientific/Engineering :: Artificial Intelligence",
        "License :: OSI Approved :: MIT License",
        "Programming Language :: Python :: 3",
        "Programming Language :: Python :: 3.8",
        "Programming Language :: Python :: 3.9",
        "Programming Language :: Python :: 3.10",
        "Programming Language :: Python :: 3.11",
        "Programming Language :: C++",
        "Programming Language :: Python :: Implementation :: CPython",
    ],
    keywords="pytorch deep-learning quantization ternary bitnet transformer",
    project_urls={
        "Bug Reports": "https://github.com/yourusername/bitlinear/issues",
        "Source": "https://github.com/yourusername/bitlinear",
        "Documentation": "https://github.com/yourusername/bitlinear/blob/main/README.md",
    },
)