# Copyright 2021, Canonical Ltd.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

"""Module to handle errors and bailing out of an event/hook."""

import logging
from contextlib import contextmanager

from ops.charm import CharmBase
from ops.model import BlockedStatus

logger = logging.getLogger(__name__)


class GuardException(Exception):
    """GuardException."""

    pass


class BlockedException(Exception):
    """Charm is blocked."""

    pass


@contextmanager
def guard(
    charm: "CharmBase",
    section: str,
    handle_exception: bool = True,
    log_traceback: bool = True,
    **__
) -> None:
    """Context manager to handle errors and bailing out of an event/hook.

    The nature of Juju is that all the information may not be available to run
    a set of actions.  This context manager allows a section of code to be
    'guarded' so that it can be bailed at any time.

    It also handles errors which can be interpreted as a Block rather than the
    charm going into error.

    :param charm: the charm class (so that unit status can be set)
    :param section: the name of the section (for debugging/info purposes)
    :handle_exception: whether to handle the exception to a BlockedStatus()
    :log_traceback: whether to log the traceback for debugging purposes.
    :raises: Exception if handle_exception is False
    """
    logger.info("Entering guarded section: '%s'", section)
    try:
        yield
        logging.info("Completed guarded section fully: '%s'", section)
    except GuardException as e:
        logger.info(
            "Guarded Section: Early exit from '%s' due to '%s'.",
            section,
            str(e),
        )
    except BlockedException as e:
        logger.warning(
            "Charm is blocked in section '%s' due to '%s'", section, str(e)
        )
        charm.unit.status = BlockedStatus(e.msg)
    except Exception as e:
        # something else went wrong
        if handle_exception:
            logging.error(
                "Exception raised in secion '%s': %s", section, str(e)
            )
            if log_traceback:
                import traceback

                logging.error(traceback.format_exc())
                charm.unit.status = BlockedStatus(
                    "Error in charm (see logs): {}".format(str(e))
                )
            return
        raise