import io
import logging
import mock

import pytest


@pytest.fixture
def caplog_text(request):
    """
    A fixture that returns a function that returns caplog.text

    caplog isn't available in pytest in all of our target releases; this either
    uses caplog.text if available, or a shim which replicates what it does.

    Specifically, bionic is the first Ubuntu release to contain a version of
    pytest new enough for the caplog fixture to be present.  In xenial, the
    python3-pytest-catchlog package provides the same functionality (this is
    the code that was later integrated in to pytest).  For trusty, there is no
    packaged alternative to this shim.

    (It returns a function so that the requester can decide when to examine the
    logs; if it returned caplog.text directly, that would always be empty.)
    """
    log_level = getattr(request, 'param', logging.INFO)
    try:
        try:
            caplog = request.getfixturevalue('caplog')
        except AttributeError:
            # Older versions of pytest only have getfuncargvalue, which is now
            # deprecated in favour of getfixturevalue
            caplog = request.getfuncargvalue('caplog')
        caplog.set_level(log_level)

        def _func():
            return caplog.text
    except LookupError:
        # If the caplog fixture isn't available, shim something in ourselves
        root = logging.getLogger()
        root.setLevel(log_level)
        handler = logging.StreamHandler(io.StringIO())
        handler.setFormatter(
            logging.Formatter(
                "%(filename)-25s %(lineno)4d %(levelname)-8s %(message)s"))
        root.addHandler(handler)

        def _func():
            return handler.stream.getvalue()

        def clear_handlers():
            logging.root.handlers = []

        request.addfinalizer(clear_handlers)
    return _func


@pytest.yield_fixture
def logging_sandbox():
    # Monkeypatch a replacement root logger, so that our changes to logging
    # configuration don't persist outside of the test
    root_logger = logging.RootLogger(logging.WARNING)

    with mock.patch.object(logging, 'root', root_logger):
        with mock.patch.object(logging.Logger, 'root', root_logger):
            with mock.patch.object(logging.Logger, 'manager',
                                   logging.Manager(root_logger)):
                yield
