import pytest
from rpython.rlib import rvmprof

class FakeVMProf(object):

    def __init__(self):
        self._enabled = False
        self._ignore_signals = 1

    # --- VMProf official API ---
    # add fake methods as needed by the tests

    def stop_sampling(self):
        self._ignore_signals += 1

    def start_sampling(self):
        assert self._ignore_signals > 0, ('calling start_sampling() without '
                                          'the corresponding stop_sampling()?')
        self._ignore_signals -= 1

    # --- FakeVMProf specific API ---
    # this API is not part of rvmprof, but available only inside tests using
    # fakevmprof

    @property
    def is_sampling_enabled(self):
        return self._ignore_signals == 0

    def check_status(self):
        """
        To be called during test teardown
        """
        if self._ignore_signals != 1:
            msg = ('Invalid value for fakevmprof._ignore_signals: expected 1, '
                   'got %d. This probably means that you called '
                   '{start,stop}_sampling() a wrong number of times')
            raise ValueError, msg % self._ignore_signals


@pytest.fixture
def fakevmprof(request, monkeypatch):
    fake = FakeVMProf()
    monkeypatch.setattr(rvmprof.rvmprof, '_vmprof_instance', fake)
    request.addfinalizer(fake.check_status)
    return fake