# SPDX-License-Identifier: Apache-2.0
# SPDX-FileCopyrightText: Copyright contributors to the vLLM project

import contextlib
import dataclasses
import sys
import traceback
from collections.abc import Callable, Generator


@dataclasses.dataclass
class BlameResult:
    found: bool = False
    trace_stack: str = ""


@contextlib.contextmanager
def blame(func: Callable) -> Generator[BlameResult, None, None]:
    """
    Trace the function calls to find the first function that satisfies the
    condition. The trace stack will be stored in the result.

    Usage:

    ```python
    with blame(lambda: some_condition()) as result:
        # do something

    if result.found:
        print(result.trace_stack)
    """
    result = BlameResult()

    def _trace_calls(frame, event, arg=None):
        nonlocal result
        if event in ["call", "return"]:
            # for every function call or return
            try:
                # Temporarily disable the trace function
                sys.settrace(None)
                # check condition here
                if not result.found and func():
                    result.found = True
                    result.trace_stack = "".join(traceback.format_stack())
                # Re-enable the trace function
                sys.settrace(_trace_calls)
            except NameError:
                # modules are deleted during shutdown
                pass
        return _trace_calls

    try:
        sys.settrace(_trace_calls)
        yield result
    finally:
        sys.settrace(None)
