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"""Zero-overhead NVTX range wrapper.

Off by default. Enable via `--enable-nvtx` or `TOKENSPEED_NVTX=1`.
`nvtx_range(...)` is dual-purpose — context manager or decorator:

    @nvtx_range("forward", color="blue")
    def forward(self, ...): ...

    with nvtx_range("sampling", color="yellow"):
        backend.sample(...)

The `_enabled` check is re-read at each call, so a decorator applied at
import time still arms once the CLI flag flips the flag at runtime.
"""

from __future__ import annotations

import functools

from tokenspeed_kernel.platform import current_platform

from tokenspeed.runtime.utils.env import envs

if current_platform().is_nvidia:
    import nvtx
    from nvtx.colors import _NVTX_COLORS
else:
    nvtx = None
    _NVTX_COLORS = ()

NVTX_DOMAIN: str = "tokenspeed"

# Built-in colors — keeping tokenspeed self-contained (no matplotlib
# dependency for color resolution). Anything else falls back to "blue"
# rather than crashing the server.
_VALID_COLORS = frozenset(c for c in _NVTX_COLORS if c is not None)

_nvtx_available = nvtx is not None
_enabled: bool = _nvtx_available and envs.TOKENSPEED_NVTX.get()


def set_nvtx_enabled(enabled: bool) -> None:
    global _enabled
    _enabled = _nvtx_available and enabled


class _Range:
    __slots__ = ("name", "color", "category")

    def __init__(
        self,
        name: str,
        color: str,
        category: str | None,
    ) -> None:
        self.name = name
        self.color = color
        self.category = category

    def __enter__(self):
        if _enabled:
            nvtx.push_range(
                message=self.name,
                color=self.color,
                domain=NVTX_DOMAIN,
                category=self.category,
            )
        return self

    def __exit__(self, *exc):
        if _enabled:
            nvtx.pop_range(domain=NVTX_DOMAIN)
        return False

    def __call__(self, func):
        name, color, category = self.name, self.color, self.category

        @functools.wraps(func)
        def wrapper(*args, **kwargs):
            if not _enabled:
                return func(*args, **kwargs)
            nvtx.push_range(
                message=name, color=color, domain=NVTX_DOMAIN, category=category
            )
            try:
                return func(*args, **kwargs)
            finally:
                nvtx.pop_range(domain=NVTX_DOMAIN)

        return wrapper


def nvtx_range(
    name: str,
    *,
    color: str = "blue",
    category: str | None = None,
) -> _Range:
    if color not in _VALID_COLORS:
        color = "blue"
    return _Range(name, color, category)