"""Point flashinfer/vLLM at the pip CUDA toolkit and skip JIT that needs nvcc."""

from __future__ import annotations

import os
import sys
from pathlib import Path


def find_cuda_home() -> Path | None:
    existing = os.environ.get("CUDA_HOME") or os.environ.get("CUDA_PATH")
    if existing:
        home = Path(existing)
        if (home / "bin" / "nvcc").is_file():
            return home
    # Do not resolve() sys.executable — venv/bin/python is a symlink to
    # /usr/bin/python3.x, which walks out of the venv and misses nvidia/cu*.
    prefixes = [
        Path(sys.prefix),
        Path(getattr(sys, "base_prefix", sys.prefix)),
        Path(sys.executable).parent.parent,
    ]
    seen: set[Path] = set()
    for prefix in prefixes:
        if prefix in seen:
            continue
        seen.add(prefix)
        matches = sorted(prefix.glob("lib/python*/site-packages/nvidia/cu*/bin/nvcc"))
        if matches:
            return matches[-1].parent.parent
    return None


def apply(*, disable_flashinfer_sampler: bool = True, gdn_backend: str = "triton") -> Path | None:
    """Set env for this process and every vLLM worker it later spawns."""
    home = find_cuda_home()
    if home is not None:
        os.environ["CUDA_HOME"] = str(home)
        os.environ["CUDA_PATH"] = str(home)
        os.environ["PATH"] = f"{home / 'bin'}:{os.environ.get('PATH', '')}"
        _link_system_cuda(home)
        _ensure_lib64(home)
        print(f"CUDA_HOME={home}", flush=True)
    if disable_flashinfer_sampler:
        os.environ.setdefault("VLLM_USE_FLASHINFER_SAMPLER", "0")
    if gdn_backend:
        os.environ.setdefault("ALBEDO_GDN_PREFILL_BACKEND", gdn_backend)
    # Per-process Triton cache. Shared /root/.triton/cache races on overlayfs;
    # /dev/shm is noexec and cannot mmap compiled .so files.
    cache = Path("/workspace/data/triton-cache") / f"pid-{os.getpid()}"
    cache.mkdir(parents=True, exist_ok=True)
    os.environ["TRITON_CACHE_DIR"] = str(cache)
    os.environ.setdefault("TRITON_HOME", "/workspace/data/triton-cache/home")
    return home


def _link_system_cuda(home: Path) -> None:
    target = Path("/usr/local/cuda")
    if target.exists() or target.is_symlink():
        return
    try:
        target.symlink_to(home)
        print(f"linked {target} -> {home}", flush=True)
    except OSError as exc:
        print(f"could not link {target}: {exc}", flush=True)


def _ensure_lib64(home: Path) -> None:
    lib64 = home / "lib64"
    lib = home / "lib"
    if lib64.exists() or not lib.is_dir():
        return
    try:
        lib64.symlink_to("lib")
    except OSError:
        pass