"""Make TileLang unimportable, the way it is on a card where it was never installed.

Two independent switches, because the two scenarios need different things:

* ``DEEPINFER_SIMULATE_NO_TILELANG=1`` -- ``tilelang`` and ``tvm_ffi`` are gone. This is the
  target state of the torch-reference bring-up: `tile_kernels` itself is installed (it is a
  plain Python package), but none of its compiled kernels can be built or loaded.
* ``DEEPINFER_SIMULATE_NO_TILE_KERNELS=1`` -- additionally removes `tile_kernels`. Stricter
  than any real deployment needs to be, useful only to prove that no interface module reaches
  for it at import time.

Blocking by meta path rather than by uninstalling matters because the image ships its own
tilelang in system site-packages, and a venv that inherits it silently gets the package back.
It also must live in `sitecustomize`: the engine spawns one process per data-parallel rank,
and an import in the parent would not follow them.
"""

import os

_blocked = []
if os.environ.get("DEEPINFER_SIMULATE_NO_TILELANG"):
    _blocked += ["tilelang", "tvm_ffi"]
if os.environ.get("DEEPINFER_SIMULATE_NO_TILE_KERNELS"):
    _blocked += ["tile_kernels"]

if _blocked:
    import sys
    from importlib.abc import MetaPathFinder

    _BLOCKED = tuple(_blocked)

    class _Blocked(MetaPathFinder):
        def find_spec(
            self,
            fullname: str,
            path: object = None,
            target: object = None,
        ) -> None:
            if fullname.split(".")[0] in _BLOCKED:
                # Raise rather than return None: a finder returning None only says "not mine",
                # and the remaining finders would happily locate the installed package. Raising
                # is the only way a meta path entry can actually make something unimportable.
                # `importlib.util.find_spec` will raise too, so probes must expect that.
                raise ModuleNotFoundError(
                    f"No module named {fullname!r} (blocked: simulating a host without it)",
                    name=fullname,
                )
            return None

    sys.meta_path.insert(0, _Blocked())
    for _name in list(sys.modules):
        if _name.split(".")[0] in _BLOCKED:
            del sys.modules[_name]