# Copyright 2011 OpenStack Foundation.
# All Rights Reserved.
#
#    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.

import errno
import logging
import os
from typing import TypeAlias, TypedDict

from oslo_config import cfg

LOG = logging.getLogger(__name__)


class CacheEntry(TypedDict):
    data: str
    mtime: float


CacheT: TypeAlias = dict[str, CacheEntry]


def read_cached_file(
    cache: CacheT, filename: str, force_reload: bool = False
) -> tuple[bool, str]:
    """Read from a file if it has been modified.

    :param cache: dictionary to hold opaque cache.
    :param filename: the file path to read.
    :param force_reload: Whether to reload the file.
    :returns: A tuple with a boolean specifying if the data is fresh
              or not.
    """

    if force_reload:
        delete_cached_file(cache, filename)

    reloaded = False
    try:
        mtime = os.path.getmtime(filename)
    except OSError as err:
        msg = err.strerror
        LOG.error(
            'Config file not found %(filename)s: %(msg)s',
            {'filename': filename, 'msg': msg},
        )
        return True, ''

    cache_info = cache.setdefault(filename, {'data': '', 'mtime': 0})

    if not cache_info or mtime > cache_info.get('mtime', 0):
        LOG.debug('Reloading cached file %s', filename)
        try:
            with open(filename) as fap:
                cache_info['data'] = fap.read()
        except OSError as err:
            msg = err.strerror
            err_code = err.errno
            LOG.error(
                'IO error loading %(filename)s: %(msg)s',
                {'filename': filename, 'msg': msg},
            )
            if err_code == errno.EACCES:
                raise cfg.ConfigFilesPermissionDeniedError([filename])
        except OSError as err:
            msg = err.strerror
            LOG.error(
                'Config file not found %(filename)s: %(msg)s',
                {'filename': filename, 'msg': msg},
            )
            raise cfg.ConfigFilesNotFoundError([filename])
        cache_info['mtime'] = mtime
        reloaded = True
    return (reloaded, cache_info['data'])


def delete_cached_file(cache: CacheT, filename: str) -> None:
    """Delete cached file if present.

    :param cache: dictionary to hold opaque cache.
    :param filename: filename to delete
    """
    try:
        del cache[filename]
    except KeyError:
        pass
