# -*- coding: utf-8 -*-
"""
The ``dateutil.zoneinfo`` module was originally designed to work with a tarball
shipped with ``dateutil``. Since ``dateutil`` now uses data from the same
sources as :py:mod:`zoneinfo`, this module is no longer necessary.

.. caution::
    This module is deprecated, and its functionality has been dramatically
    curtailed. It is recommended that you adopt the standard library module
    :py:mod:`zoneinfo` or :func:`dateutil.tz.gettz` instead.

"""

import json
import sys
import warnings
from tarfile import TarFile

import six

from dateutil import _tzdata_impl
from dateutil.tz import tzfile as _tzfile

__all__ = ["get_zonefile_instance", "gettz", "gettz_db_metadata"]

ZONEFILENAME = None
METADATA_FN = 'METADATA'


def _importer_stacklevel():
    """The ``stacklevel`` that attributes a warning to the importing code.

    This module can be imported through ``dateutil.__getattr__`` (e.g. by
    ``from dateutil import zoneinfo``), which calls
    ``importlib.import_module``; the warnings machinery skips the import
    system's own frames, but not those two, so skip them here.
    """
    level = 1
    frame = sys._getframe(1)  # The body of this module
    while frame.f_back is not None:
        frame = frame.f_back
        filename = frame.f_code.co_filename
        if "importlib" in filename and "_bootstrap" in filename:
            # Since Python 3.5, the warnings machinery skips these frames
            # without counting them; before that they count like any other.
            if sys.version_info < (3, 5):
                level += 1
            continue

        level += 1
        if frame.f_globals.get("__name__") not in ("importlib", "dateutil"):
            return level

    return 2


warnings.warn(
    "The `dateutil.zoneinfo` module has been replaced with a wrapper around "
    "the tzdata package, and its use is deprecated, to be removed in a future "
    "version. Use the standard library module `zoneinfo` or `dateutil.tz` "
    "instead.",
    DeprecationWarning,
    stacklevel=_importer_stacklevel(),
)


tzfile = _tzfile

class ZoneInfoFile(object):
    def __init__(self, zonefile_stream=None):
        if zonefile_stream is not None:
            self._load_legacy_zonefile_stream(zonefile_stream)
        else:
            self._eager_load_tzdata()

    def _eager_load_tzdata(self):
        try:
            import tzdata
        except ImportError as e:
            six.raise_from(
                ImportError(
                    "The tzdata module is required to use ZoneInfoFile; either add "
                    "a dependency on tzdata or migrate away from dateutil.zoneinfo."
                ),
                e,
            )

        zone_dict = {}

        for key in _tzdata_impl._load_tzdata_keys():
            with _tzdata_impl._load_tzdata(key) as f:
                zone_dict[key] = tzfile(f, key=key)

        self.zones = zone_dict
        self.metadata = {
            "metadata_version": "3.0",
            "tzversion": tzdata.IANA_VERSION,
        }

    def _load_legacy_zonefile_stream(self, zonefile_stream):
        with TarFile.open(fileobj=zonefile_stream) as tf:
            self.zones = {
                zf.name: tzfile(tf.extractfile(zf), filename=zf.name)
                for zf in tf.getmembers()
                if zf.isfile() and zf.name != METADATA_FN
            }
            # deal with links: They'll point to their parent object. Less
            # waste of memory
            links = {
                zl.name: self.zones[zl.linkname]
                for zl in tf.getmembers()
                if zl.islnk() or zl.issym()
            }
            self.zones.update(links)
            try:
                metadata_json = tf.extractfile(tf.getmember(METADATA_FN))
                metadata_str = metadata_json.read().decode("UTF-8")
                self.metadata = json.loads(metadata_str)
            except KeyError:
                # no metadata in tar file
                self.metadata = None

    def get(self, name, default=None):
        """
        Wrapper for :func:`ZoneInfoFile.zones.get`. This is a convenience method
        for retrieving zones from the zone dictionary.

        :param name:
            The name of the zone to retrieve. (Generally IANA zone names)

        :param default:
            The value to return in the event of a missing key.

        .. versionadded:: 2.6.0

        """
        return self.zones.get(name, default)


# The current API has gettz as a module function, although in fact it taps into
# a stateful class. So as a workaround for now, without changing the API, we
# will create a new "global" class instance the first time a user requests a
# timezone. Ugly, but adheres to the api.
#
# TODO: Remove after deprecation period.
_CLASS_ZONE_INSTANCE = []


def get_zonefile_instance(new_instance=False):
    """
    This is a convenience function which provides a :class:`ZoneInfoFile`
    instance using the data provided by the ``dateutil`` package. By default, it
    caches a single instance of the ZoneInfoFile object and returns that.

    :param new_instance:
        If ``True``, a new instance of :class:`ZoneInfoFile` is instantiated and
        used as the cached instance for the next call. Otherwise, new instances
        are created only as necessary.

    :return:
        Returns a :class:`ZoneInfoFile` object.

    .. versionadded:: 2.6
    """
    if new_instance:
        zif = None
    else:
        zif = getattr(get_zonefile_instance, '_cached_instance', None)

    if zif is None:
        zif = ZoneInfoFile()

        get_zonefile_instance._cached_instance = zif

    return zif


def gettz(name):
    """
    This retrieves a time zone from the ``tzdata`` package.

    :param name:
        An IANA-style time zone name, as found in the zoneinfo file.

    :return:
        Returns a :class:`dateutil.tz.tzfile` time zone object.

    .. warning::
        It is generally inadvisable to use this function, and it is only
        provided for API compatibility with earlier versions. This is *not*
        equivalent to ``dateutil.tz.gettz()``, which selects an appropriate
        time zone based on the inputs, favoring system zoneinfo. This is ONLY
        for accessing the dateutil-specific zoneinfo (which may be out of
        date compared to the system zoneinfo).

    .. deprecated:: 2.6
        If you need to use a specific zoneinfofile over the system zoneinfo,
        instantiate a :class:`dateutil.zoneinfo.ZoneInfoFile` object and call
        :func:`dateutil.zoneinfo.ZoneInfoFile.get(name)` instead.

        Use :func:`get_zonefile_instance` to retrieve an instance of the
        dateutil-provided zoneinfo.
    """
    warnings.warn("zoneinfo.gettz() will be removed in future versions, "
                  "to use the dateutil-provided zoneinfo files, instantiate a "
                  "ZoneInfoFile object and use ZoneInfoFile.zones.get() "
                  "instead. See the documentation for details.",
                  DeprecationWarning)

    if len(_CLASS_ZONE_INSTANCE) == 0:
        _CLASS_ZONE_INSTANCE.append(ZoneInfoFile())
    return _CLASS_ZONE_INSTANCE[0].zones.get(name)


def gettz_db_metadata():
    """Get the zonefile metadata

    :returns:
        A dictionary with the database metadata

    .. deprecated:: 2.6
        See deprecation warning in :func:`zoneinfo.gettz`. To get metadata,
        query the attribute ``zoneinfo.ZoneInfoFile.metadata``.
    """
    warnings.warn("zoneinfo.gettz_db_metadata() will be removed in future "
                  "versions, to use the dateutil-provided zoneinfo files, "
                  "ZoneInfoFile object and query the 'metadata' attribute "
                  "instead. See the documentation for details.",
                  DeprecationWarning)

    if len(_CLASS_ZONE_INSTANCE) == 0:
        _CLASS_ZONE_INSTANCE.append(ZoneInfoFile())
    return _CLASS_ZONE_INSTANCE[0].metadata