bucket.py

# Copyright 2014 Google LLC
#
# 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.

"""Create / interact with Google Cloud Storage buckets."""

import base64
import copy
import datetime
import functools
import json
import warnings

import six
from six.moves.urllib.parse import urlsplit

from google.api_core import page_iterator
from google.api_core import datetime_helpers
from google.cloud._helpers import _datetime_to_rfc3339
from google.cloud._helpers import _NOW
from google.cloud._helpers import _rfc3339_nanos_to_datetime
from google.cloud.exceptions import NotFound
from google.api_core.iam import Policy
from google.cloud.storage import _signing
from google.cloud.storage._helpers import _add_generation_match_parameters
from google.cloud.storage._helpers import _PropertyMixin
from google.cloud.storage._helpers import _scalar_property
from google.cloud.storage._helpers import _validate_name
from google.cloud.storage._signing import generate_signed_url_v2
from google.cloud.storage._signing import generate_signed_url_v4
from google.cloud.storage._helpers import _bucket_bound_hostname_url
from google.cloud.storage.acl import BucketACL
from google.cloud.storage.acl import DefaultObjectACL
from google.cloud.storage.blob import Blob
from google.cloud.storage.constants import _DEFAULT_TIMEOUT
from google.cloud.storage.constants import ARCHIVE_STORAGE_CLASS
from google.cloud.storage.constants import COLDLINE_STORAGE_CLASS
from google.cloud.storage.constants import DUAL_REGION_LOCATION_TYPE
from google.cloud.storage.constants import (
    DURABLE_REDUCED_AVAILABILITY_LEGACY_STORAGE_CLASS,
)
from google.cloud.storage.constants import MULTI_REGIONAL_LEGACY_STORAGE_CLASS
from google.cloud.storage.constants import MULTI_REGION_LOCATION_TYPE
from google.cloud.storage.constants import NEARLINE_STORAGE_CLASS
from google.cloud.storage.constants import REGIONAL_LEGACY_STORAGE_CLASS
from google.cloud.storage.constants import REGION_LOCATION_TYPE
from google.cloud.storage.constants import STANDARD_STORAGE_CLASS
from google.cloud.storage.notification import BucketNotification
from google.cloud.storage.notification import NONE_PAYLOAD_FORMAT
from google.cloud.storage.retry import DEFAULT_RETRY
from google.cloud.storage.retry import DEFAULT_RETRY_IF_GENERATION_SPECIFIED
from google.cloud.storage.retry import DEFAULT_RETRY_IF_ETAG_IN_JSON
from google.cloud.storage.retry import DEFAULT_RETRY_IF_METAGENERATION_SPECIFIED


_UBLA_BPO_ENABLED_MESSAGE = (
    "Pass only one of 'uniform_bucket_level_access_enabled' / "
    "'bucket_policy_only_enabled' to 'IAMConfiguration'."
)
_BPO_ENABLED_MESSAGE = (
    "'IAMConfiguration.bucket_policy_only_enabled' is deprecated.  "
    "Instead, use 'IAMConfiguration.uniform_bucket_level_access_enabled'."
)
_UBLA_BPO_LOCK_TIME_MESSAGE = (
    "Pass only one of 'uniform_bucket_level_access_lock_time' / "
    "'bucket_policy_only_lock_time' to 'IAMConfiguration'."
)
_BPO_LOCK_TIME_MESSAGE = (
    "'IAMConfiguration.bucket_policy_only_lock_time' is deprecated.  "
    "Instead, use 'IAMConfiguration.uniform_bucket_level_access_lock_time'."
)
_LOCATION_SETTER_MESSAGE = (
    "Assignment to 'Bucket.location' is deprecated, as it is only "
    "valid before the bucket is created. Instead, pass the location "
    "to `Bucket.create`."
)
_API_ACCESS_ENDPOINT = "https://storage.googleapis.com"


def _blobs_page_start(iterator, page, response):
    """Grab prefixes after a :class:`~google.cloud.iterator.Page` started.

    :type iterator: :class:`~google.api_core.page_iterator.Iterator`
    :param iterator: The iterator that is currently in use.

    :type page: :class:`~google.cloud.api.core.page_iterator.Page`
    :param page: The page that was just created.

    :type response: dict
    :param response: The JSON API response for a page of blobs.
    """
    page.prefixes = tuple(response.get("prefixes", ()))
    iterator.prefixes.update(page.prefixes)


def _item_to_blob(iterator, item):
    """Convert a JSON blob to the native object.

    .. note::

        This assumes that the ``bucket`` attribute has been
        added to the iterator after being created.

    :type iterator: :class:`~google.api_core.page_iterator.Iterator`
    :param iterator: The iterator that has retrieved the item.

    :type item: dict
    :param item: An item to be converted to a blob.

    :rtype: :class:`.Blob`
    :returns: The next blob in the page.
    """
    name = item.get("name")
    blob = Blob(name, bucket=iterator.bucket)
    blob._set_properties(item)
    return blob


def _item_to_notification(iterator, item):
    """Convert a JSON blob to the native object.

    .. note::

        This assumes that the ``bucket`` attribute has been
        added to the iterator after being created.

    :type iterator: :class:`~google.api_core.page_iterator.Iterator`
    :param iterator: The iterator that has retrieved the item.

    :type item: dict
    :param item: An item to be converted to a blob.

    :rtype: :class:`.BucketNotification`
    :returns: The next notification being iterated.
    """
    return BucketNotification.from_api_repr(item, bucket=iterator.bucket)


class LifecycleRuleConditions(dict):
    """Map a single lifecycle rule for a bucket.

    See: https://cloud.google.com/storage/docs/lifecycle

    :type age: int
    :param age: (Optional) Apply rule action to items whose age, in days,
                exceeds this value.

    :type created_before: datetime.date
    :param created_before: (Optional) Apply rule action to items created
                           before this date.

    :type is_live: bool
    :param is_live: (Optional) If true, apply rule action to non-versioned
                    items, or to items with no newer versions. If false, apply
                    rule action to versioned items with at least one newer
                    version.

    :type matches_storage_class: list(str), one or more of
                                 :attr:`Bucket.STORAGE_CLASSES`.
    :param matches_storage_class: (Optional) Apply rule action to items which
                                  whose storage class matches this value.

    :type number_of_newer_versions: int
    :param number_of_newer_versions: (Optional) Apply rule action to versioned
                                     items having N newer versions.

    :type days_since_custom_time: int
    :param days_since_custom_time: (Optional) Apply rule action to items whose number of days
                                   elapsed since the custom timestamp. This condition is relevant
                                   only for versioned objects. The value of the field must be a non
                                   negative integer. If it's zero, the object version will become
                                   eligible for lifecycle action as soon as it becomes custom.

    :type custom_time_before: :class:`datetime.date`
    :param custom_time_before: (Optional)  Date object parsed from RFC3339 valid date, apply rule action
                               to items whose custom time is before this date. This condition is relevant
                               only for versioned objects, e.g., 2019-03-16.

    :type days_since_noncurrent_time: int
    :param days_since_noncurrent_time: (Optional) Apply rule action to items whose number of days
                                        elapsed since the non current timestamp. This condition
                                        is relevant only for versioned objects. The value of the field
                                        must be a non negative integer. If it's zero, the object version
                                        will become eligible for lifecycle action as soon as it becomes
                                        non current.

    :type noncurrent_time_before: :class:`datetime.date`
    :param noncurrent_time_before: (Optional) Date object parsed from RFC3339 valid date, apply
                                   rule action to items whose non current time is before this date.
                                   This condition is relevant only for versioned objects, e.g, 2019-03-16.

    :raises ValueError: if no arguments are passed.
    """

    def __init__(
        self,
        age=None,
        created_before=None,
        is_live=None,
        matches_storage_class=None,
        number_of_newer_versions=None,
        days_since_custom_time=None,
        custom_time_before=None,
        days_since_noncurrent_time=None,
        noncurrent_time_before=None,
        _factory=False,
    ):
        conditions = {}

        if age is not None:
            conditions["age"] = age

        if created_before is not None:
            conditions["createdBefore"] = created_before.isoformat()

        if is_live is not None:
            conditions["isLive"] = is_live

        if matches_storage_class is not None:
            conditions["matchesStorageClass"] = matches_storage_class

        if number_of_newer_versions is not None:
            conditions["numNewerVersions"] = number_of_newer_versions

        if days_since_custom_time is not None:
            conditions["daysSinceCustomTime"] = days_since_custom_time

        if custom_time_before is not None:
            conditions["customTimeBefore"] = custom_time_before.isoformat()

        if not _factory and not conditions:
            raise ValueError("Supply at least one condition")

        if days_since_noncurrent_time is not None:
            conditions["daysSinceNoncurrentTime"] = days_since_noncurrent_time

        if noncurrent_time_before is not None:
            conditions["noncurrentTimeBefore"] = noncurrent_time_before.isoformat()

        super(LifecycleRuleConditions, self).__init__(conditions)

    @classmethod
    def from_api_repr(cls, resource):
        """Factory:  construct instance from resource.

        :type resource: dict
        :param resource: mapping as returned from API call.

        :rtype: :class:`LifecycleRuleConditions`
        :returns: Instance created from resource.
        """
        instance = cls(_factory=True)
        instance.update(resource)
        return instance

    @property
    def age(self):
        """Conditon's age value."""
        return self.get("age")

    @property
    def created_before(self):
        """Conditon's created_before value."""
        before = self.get("createdBefore")
        if before is not None:
            return datetime_helpers.from_iso8601_date(before)

    @property
    def is_live(self):
        """Conditon's 'is_live' value."""
        return self.get("isLive")

    @property
    def matches_storage_class(self):
        """Conditon's 'matches_storage_class' value."""
        return self.get("matchesStorageClass")

    @property
    def number_of_newer_versions(self):
        """Conditon's 'number_of_newer_versions' value."""
        return self.get("numNewerVersions")

    @property
    def days_since_custom_time(self):
        """Conditon's 'days_since_custom_time' value."""
        return self.get("daysSinceCustomTime")

    @property
    def custom_time_before(self):
        """Conditon's 'custom_time_before' value."""
        before = self.get("customTimeBefore")
        if before is not None:
            return datetime_helpers.from_iso8601_date(before)

    @property
    def days_since_noncurrent_time(self):
        """Conditon's 'days_since_noncurrent_time' value."""
        return self.get("daysSinceNoncurrentTime")

    @property
    def noncurrent_time_before(self):
        """Conditon's 'noncurrent_time_before' value."""
        before = self.get("noncurrentTimeBefore")
        if before is not None:
            return datetime_helpers.from_iso8601_date(before)


class LifecycleRuleDelete(dict):
    """Map a lifecycle rule deleting matching items.

    :type kw: dict
    :params kw: arguments passed to :class:`LifecycleRuleConditions`.
    """

    def __init__(self, **kw):
        conditions = LifecycleRuleConditions(**kw)
        rule = {"action": {"type": "Delete"}, "condition": dict(conditions)}
        super(LifecycleRuleDelete, self).__init__(rule)

    @classmethod
    def from_api_repr(cls, resource):
        """Factory:  construct instance from resource.

        :type resource: dict
        :param resource: mapping as returned from API call.

        :rtype: :class:`LifecycleRuleDelete`
        :returns: Instance created from resource.
        """
        instance = cls(_factory=True)
        instance.update(resource)
        return instance


class LifecycleRuleSetStorageClass(dict):
    """Map a lifecycle rule updating storage class of matching items.

    :type storage_class: str, one of :attr:`Bucket.STORAGE_CLASSES`.
    :param storage_class: new storage class to assign to matching items.

    :type kw: dict
    :params kw: arguments passed to :class:`LifecycleRuleConditions`.
    """

    def __init__(self, storage_class, **kw):
        conditions = LifecycleRuleConditions(**kw)
        rule = {
            "action": {"type": "SetStorageClass", "storageClass": storage_class},
            "condition": dict(conditions),
        }
        super(LifecycleRuleSetStorageClass, self).__init__(rule)

    @classmethod
    def from_api_repr(cls, resource):
        """Factory:  construct instance from resource.

        :type resource: dict
        :param resource: mapping as returned from API call.

        :rtype: :class:`LifecycleRuleDelete`
        :returns: Instance created from resource.
        """
        action = resource["action"]
        instance = cls(action["storageClass"], _factory=True)
        instance.update(resource)
        return instance


_default = object()


class IAMConfiguration(dict):
    """Map a bucket's IAM configuration.

    :type bucket: :class:`Bucket`
    :params bucket: Bucket for which this instance is the policy.

    :type uniform_bucket_level_access_enabled: bool
    :params bucket_policy_only_enabled:
        (Optional) Whether the IAM-only policy is enabled for the bucket.

    :type uniform_bucket_level_access_locked_time: :class:`datetime.datetime`
    :params uniform_bucket_level_locked_time:
        (Optional) When the bucket's IAM-only policy was enabled.
        This value should normally only be set by the back-end API.

    :type bucket_policy_only_enabled: bool
    :params bucket_policy_only_enabled:
        Deprecated alias for :data:`uniform_bucket_level_access_enabled`.

    :type bucket_policy_only_locked_time: :class:`datetime.datetime`
    :params bucket_policy_only_locked_time:
        Deprecated alias for :data:`uniform_bucket_level_access_locked_time`.
    """

    def __init__(
        self,
        bucket,
        uniform_bucket_level_access_enabled=_default,
        uniform_bucket_level_access_locked_time=_default,
        bucket_policy_only_enabled=_default,
        bucket_policy_only_locked_time=_default,
    ):
        if bucket_policy_only_enabled is not _default:

            if uniform_bucket_level_access_enabled is not _default:
                raise ValueError(_UBLA_BPO_ENABLED_MESSAGE)

            warnings.warn(_BPO_ENABLED_MESSAGE, DeprecationWarning, stacklevel=2)
            uniform_bucket_level_access_enabled = bucket_policy_only_enabled

        if bucket_policy_only_locked_time is not _default:

            if uniform_bucket_level_access_locked_time is not _default:
                raise ValueError(_UBLA_BPO_LOCK_TIME_MESSAGE)

            warnings.warn(_BPO_LOCK_TIME_MESSAGE, DeprecationWarning, stacklevel=2)
            uniform_bucket_level_access_locked_time = bucket_policy_only_locked_time

        if uniform_bucket_level_access_enabled is _default:
            uniform_bucket_level_access_enabled = False

        data = {
            "uniformBucketLevelAccess": {"enabled": uniform_bucket_level_access_enabled}
        }
        if uniform_bucket_level_access_locked_time is not _default:
            data["uniformBucketLevelAccess"]["lockedTime"] = _datetime_to_rfc3339(
                uniform_bucket_level_access_locked_time
            )
        super(IAMConfiguration, self).__init__(data)
        self._bucket = bucket

    @classmethod
    def from_api_repr(cls, resource, bucket):
        """Factory:  construct instance from resource.

        :type bucket: :class:`Bucket`
        :params bucket: Bucket for which this instance is the policy.

        :type resource: dict
        :param resource: mapping as returned from API call.

        :rtype: :class:`IAMConfiguration`
        :returns: Instance created from resource.
        """
        instance = cls(bucket)
        instance.update(resource)
        return instance

    @property
    def bucket(self):
        """Bucket for which this instance is the policy.

        :rtype: :class:`Bucket`
        :returns: the instance's bucket.
        """
        return self._bucket

    @property
    def uniform_bucket_level_access_enabled(self):
        """If set, access checks only use bucket-level IAM policies or above.

        :rtype: bool
        :returns: whether the bucket is configured to allow only IAM.
        """
        ubla = self.get("uniformBucketLevelAccess", {})
        return ubla.get("enabled", False)

    @uniform_bucket_level_access_enabled.setter
    def uniform_bucket_level_access_enabled(self, value):
        ubla = self.setdefault("uniformBucketLevelAccess", {})
        ubla["enabled"] = bool(value)
        self.bucket._patch_property("iamConfiguration", self)

    @property
    def uniform_bucket_level_access_locked_time(self):
        """Deadline for changing :attr:`uniform_bucket_level_access_enabled` from true to false.

        If the bucket's :attr:`uniform_bucket_level_access_enabled` is true, this property
        is time time after which that setting becomes immutable.

        If the bucket's :attr:`uniform_bucket_level_access_enabled` is false, this property
        is ``None``.

        :rtype: Union[:class:`datetime.datetime`, None]
        :returns:  (readonly) Time after which :attr:`uniform_bucket_level_access_enabled` will
                   be frozen as true.
        """
        ubla = self.get("uniformBucketLevelAccess", {})
        stamp = ubla.get("lockedTime")
        if stamp is not None:
            stamp = _rfc3339_nanos_to_datetime(stamp)
        return stamp

    @property
    def bucket_policy_only_enabled(self):
        """Deprecated alias for :attr:`uniform_bucket_level_access_enabled`.

        :rtype: bool
        :returns: whether the bucket is configured to allow only IAM.
        """
        return self.uniform_bucket_level_access_enabled

    @bucket_policy_only_enabled.setter
    def bucket_policy_only_enabled(self, value):
        warnings.warn(_BPO_ENABLED_MESSAGE, DeprecationWarning, stacklevel=2)
        self.uniform_bucket_level_access_enabled = value

    @property
    def bucket_policy_only_locked_time(self):
        """Deprecated alias for :attr:`uniform_bucket_level_access_locked_time`.

        :rtype: Union[:class:`datetime.datetime`, None]
        :returns:
            (readonly) Time after which :attr:`bucket_policy_only_enabled` will
            be frozen as true.
        """
        return self.uniform_bucket_level_access_locked_time


class Bucket(_PropertyMixin):
    """A class representing a Bucket on Cloud Storage.

    :type client: :class:`google.cloud.storage.client.Client`
    :param client: A client which holds credentials and project configuration
                   for the bucket (which requires a project).

    :type name: str
    :param name: The name of the bucket. Bucket names must start and end with a
                 number or letter.

    :type user_project: str
    :param user_project: (Optional) the project ID to be billed for API
                         requests made via this instance.
    """

    _MAX_OBJECTS_FOR_ITERATION = 256
    """Maximum number of existing objects allowed in iteration.

    This is used in Bucket.delete() and Bucket.make_public().
    """

    STORAGE_CLASSES = (
        STANDARD_STORAGE_CLASS,
        NEARLINE_STORAGE_CLASS,
        COLDLINE_STORAGE_CLASS,
        ARCHIVE_STORAGE_CLASS,
        MULTI_REGIONAL_LEGACY_STORAGE_CLASS,  # legacy
        REGIONAL_LEGACY_STORAGE_CLASS,  # legacy
        DURABLE_REDUCED_AVAILABILITY_LEGACY_STORAGE_CLASS,  # legacy
    )
    """Allowed values for :attr:`storage_class`.

    Default value is :attr:`STANDARD_STORAGE_CLASS`.

    See
    https://cloud.google.com/storage/docs/json_api/v1/buckets#storageClass
    https://cloud.google.com/storage/docs/storage-classes
    """

    _LOCATION_TYPES = (
        MULTI_REGION_LOCATION_TYPE,
        REGION_LOCATION_TYPE,
        DUAL_REGION_LOCATION_TYPE,
    )
    """Allowed values for :attr:`location_type`."""

    def __init__(self, client, name=None, user_project=None):
        """
        property :attr:`name`
            Get the bucket's name.
        """
        name = _validate_name(name)
        super(Bucket, self).__init__(name=name)
        self._client = client
        self._acl = BucketACL(self)
        self._default_object_acl = DefaultObjectACL(self)
        self._label_removals = set()
        self._user_project = user_project

    def __repr__(self):
        return "<Bucket: %s>" % (self.name,)

    @property
    def client(self):
        """The client bound to this bucket."""
        return self._client

    def _set_properties(self, value):
        """Set the properties for the current object.

        :type value: dict or :class:`google.cloud.storage.batch._FutureDict`
        :param value: The properties to be set.
        """
        self._label_removals.clear()
        return super(Bucket, self)._set_properties(value)

    @property
    def user_project(self):
        """Project ID to be billed for API requests made via this bucket.

        If unset, API requests are billed to the bucket owner.

        A user project is required for all operations on Requester Pays buckets.

        See https://cloud.google.com/storage/docs/requester-pays#requirements for details.

        :rtype: str
        """
        return self._user_project

    @classmethod
    def from_string(cls, uri, client=None):
        """Get a constructor for bucket object by URI.

        :type uri: str
        :param uri: The bucket uri pass to get bucket object.

        :type client: :class:`~google.cloud.storage.client.Client` or
                      ``NoneType``
        :param client: (Optional) The client to use.

        :rtype: :class:`google.cloud.storage.bucket.Bucket`
        :returns: The bucket object created.

        Example:
            Get a constructor for bucket object by URI..

            >>> from google.cloud import storage
            >>> from google.cloud.storage.bucket import Bucket
            >>> client = storage.Client()
            >>> bucket = Bucket.from_string("gs://bucket", client)
        """
        scheme, netloc, path, query, frag = urlsplit(uri)

        if scheme != "gs":
            raise ValueError("URI scheme must be gs")

        return cls(client, name=netloc)

    def blob(
        self,
        blob_name,
        chunk_size=None,
        encryption_key=None,
        kms_key_name=None,
        generation=None,
    ):
        """Factory constructor for blob object.

        .. note::
          This will not make an HTTP request; it simply instantiates
          a blob object owned by this bucket.

        :type blob_name: str
        :param blob_name: The name of the blob to be instantiated.

        :type chunk_size: int
        :param chunk_size: The size of a chunk of data whenever iterating
                           (in bytes). This must be a multiple of 256 KB per
                           the API specification.

        :type encryption_key: bytes
        :param encryption_key:
            (Optional) 32 byte encryption key for customer-supplied encryption.

        :type kms_key_name: str
        :param kms_key_name:
            (Optional) Resource name of KMS key used to encrypt blob's content.

        :type generation: long
        :param generation: (Optional) If present, selects a specific revision of
                           this object.

        :rtype: :class:`google.cloud.storage.blob.Blob`
        :returns: The blob object created.
        """
        return Blob(
            name=blob_name,
            bucket=self,
            chunk_size=chunk_size,
            encryption_key=encryption_key,
            kms_key_name=kms_key_name,
            generation=generation,
        )

    def notification(
        self,
        topic_name=None,
        topic_project=None,
        custom_attributes=None,
        event_types=None,
        blob_name_prefix=None,
        payload_format=NONE_PAYLOAD_FORMAT,
        notification_id=None,
    ):
        """Factory:  create a notification resource for the bucket.

        See: :class:`.BucketNotification` for parameters.

        :rtype: :class:`.BucketNotification`
        """
        return BucketNotification(
            self,
            topic_name=topic_name,
            topic_project=topic_project,
            custom_attributes=custom_attributes,
            event_types=event_types,
            blob_name_prefix=blob_name_prefix,
            payload_format=payload_format,
            notification_id=notification_id,
        )

    def exists(
        self,
        client=None,
        timeout=_DEFAULT_TIMEOUT,
        if_metageneration_match=None,
        if_metageneration_not_match=None,
        retry=DEFAULT_RETRY,
    ):
        """Determines whether or not this bucket exists.

        If :attr:`user_project` is set, bills the API request to that project.

        :type client: :class:`~google.cloud.storage.client.Client` or
                      ``NoneType``
        :param client: (Optional) The client to use. If not passed, falls back
                       to the ``client`` stored on the current bucket.

        :type timeout: float or tuple
        :param timeout: (Optional) The amount of time, in seconds, to wait
            for the server response.

            Can also be passed as a tuple (connect_timeout, read_timeout).
            See :meth:`requests.Session.request` documentation for details.

        :type if_metageneration_match: long
        :param if_metageneration_match: (Optional) Make the operation conditional on whether the
                                        blob's current metageneration matches the given value.

        :type if_metageneration_not_match: long
        :param if_metageneration_not_match: (Optional) Make the operation conditional on whether the
                                            blob's current metageneration does not match the given value.

        :type retry: google.api_core.retry.Retry or google.cloud.storage.retry.ConditionalRetryPolicy
        :param retry: (Optional) How to retry the RPC. A None value will disable retries.
            A google.api_core.retry.Retry value will enable retries, and the object will
            define retriable response codes and errors and configure backoff and timeout options.

            A google.cloud.storage.retry.ConditionalRetryPolicy value wraps a Retry object and
            activates it only if certain conditions are met. This class exists to provide safe defaults
            for RPC calls that are not technically safe to retry normally (due to potential data
            duplication or other side-effects) but become safe to retry if a condition such as
            if_metageneration_match is set.

            See the retry.py source code and docstrings in this package (google.cloud.storage.retry) for
            information on retry types and how to configure them.

        :rtype: bool
        :returns: True if the bucket exists in Cloud Storage.
        """
        client = self._require_client(client)
        # We only need the status code (200 or not) so we seek to
        # minimize the returned payload.
        query_params = {"fields": "name"}

        if self.user_project is not None:
            query_params["userProject"] = self.user_project

        _add_generation_match_parameters(
            query_params,
            if_metageneration_match=if_metageneration_match,
            if_metageneration_not_match=if_metageneration_not_match,
        )
        try:
            # We intentionally pass `_target_object=None` since fields=name
            # would limit the local properties.
            client._connection.api_request(
                method="GET",
                path=self.path,
                query_params=query_params,
                _target_object=None,
                timeout=timeout,
                retry=retry,
            )
            # NOTE: This will not fail immediately in a batch. However, when
            #       Batch.finish() is called, the resulting `NotFound` will be
            #       raised.
            return True
        except NotFound:
            return False

    def create(
        self,
        client=None,
        project=None,
        location=None,
        predefined_acl=None,
        predefined_default_object_acl=None,
        timeout=_DEFAULT_TIMEOUT,
        retry=DEFAULT_RETRY,
    ):
        """DEPRECATED. Creates current bucket.

        .. note::
          Direct use of this method is deprecated. Use ``Client.create_bucket()`` instead.

        If the bucket already exists, will raise
        :class:`google.cloud.exceptions.Conflict`.

        :type client: :class:`~google.cloud.storage.client.Client` or
                      ``NoneType``
        :param client: (Optional) The client to use. If not passed, falls back
                       to the ``client`` stored on the current bucket.

        :type project: str
        :param project: (Optional) The project under which the bucket is to
                        be created. If not passed, uses the project set on
                        the client.
        :raises ValueError: if ``project`` is None and client's
                            :attr:`project` is also None.

        :type location: str
        :param location: (Optional) The location of the bucket. If not passed,
                         the default location, US, will be used. See
                         https://cloud.google.com/storage/docs/bucket-locations

        :type predefined_acl: str
        :param predefined_acl:
            (Optional) Name of predefined ACL to apply to bucket. See:
            https://cloud.google.com/storage/docs/access-control/lists#predefined-acl

        :type predefined_default_object_acl: str
        :param predefined_default_object_acl:
            (Optional) Name of predefined ACL to apply to bucket's objects. See:
            https://cloud.google.com/storage/docs/access-control/lists#predefined-acl

        :type timeout: float or tuple
        :param timeout: (Optional) The amount of time, in seconds, to wait
            for the server response.

            Can also be passed as a tuple (connect_timeout, read_timeout).
            See :meth:`requests.Session.request` documentation for details.

        :type retry: google.api_core.retry.Retry or google.cloud.storage.retry.ConditionalRetryPolicy
        :param retry: (Optional) How to retry the RPC. A None value will disable retries.
            A google.api_core.retry.Retry value will enable retries, and the object will
            define retriable response codes and errors and configure backoff and timeout options.

            A google.cloud.storage.retry.ConditionalRetryPolicy value wraps a Retry object and
            activates it only if certain conditions are met. This class exists to provide safe defaults
            for RPC calls that are not technically safe to retry normally (due to potential data
            duplication or other side-effects) but become safe to retry if a condition such as
            if_metageneration_match is set.

            See the retry.py source code and docstrings in this package (google.cloud.storage.retry) for
            information on retry types and how to configure them.
        """
        warnings.warn(
            "Bucket.create() is deprecated and will be removed in future."
            "Use Client.create_bucket() instead.",
            PendingDeprecationWarning,
            stacklevel=1,
        )

        client = self._require_client(client)
        client.create_bucket(
            bucket_or_name=self,
            project=project,
            user_project=self.user_project,
            location=location,
            predefined_acl=predefined_acl,
            predefined_default_object_acl=predefined_default_object_acl,
            timeout=timeout,
            retry=retry,
        )

    def update(
        self,
        client=None,
        timeout=_DEFAULT_TIMEOUT,
        if_metageneration_match=None,
        if_metageneration_not_match=None,
        retry=DEFAULT_RETRY_IF_METAGENERATION_SPECIFIED,
    ):
        """Sends all properties in a PUT request.

        Updates the ``_properties`` with the response from the backend.

        If :attr:`user_project` is set, bills the API request to that project.

        :type client: :class:`~google.cloud.storage.client.Client` or
                      ``NoneType``
        :param client: the client to use. If not passed, falls back to the
                       ``client`` stored on the current object.

        :type timeout: float or tuple
        :param timeout: (Optional) The amount of time, in seconds, to wait
            for the server response.

            Can also be passed as a tuple (connect_timeout, read_timeout).
            See :meth:`requests.Session.request` documentation for details.

        :type if_metageneration_match: long
        :param if_metageneration_match: (Optional) Make the operation conditional on whether the
                                        blob's current metageneration matches the given value.

        :type if_metageneration_not_match: long
        :param if_metageneration_not_match: (Optional) Make the operation conditional on whether the
                                            blob's current metageneration does not match the given value.

        :type retry: google.api_core.retry.Retry or google.cloud.storage.retry.ConditionalRetryPolicy
        :param retry: (Optional) How to retry the RPC. A None value will disable retries.
            A google.api_core.retry.Retry value will enable retries, and the object will
            define retriable response codes and errors and configure backoff and timeout options.

            A google.cloud.storage.retry.ConditionalRetryPolicy value wraps a Retry object and
            activates it only if certain conditions are met. This class exists to provide safe defaults
            for RPC calls that are not technically safe to retry normally (due to potential data
            duplication or other side-effects) but become safe to retry if a condition such as
            if_metageneration_match is set.

            See the retry.py source code and docstrings in this package (google.cloud.storage.retry) for
            information on retry types and how to configure them.
        """
        super(Bucket, self).update(
            client=client,
            timeout=timeout,
            if_metageneration_match=if_metageneration_match,
            if_metageneration_not_match=if_metageneration_not_match,
            retry=retry,
        )

    def reload(
        self,
        client=None,
        projection="noAcl",
        timeout=_DEFAULT_TIMEOUT,
        if_metageneration_match=None,
        if_metageneration_not_match=None,
        retry=DEFAULT_RETRY,
    ):
        """Reload properties from Cloud Storage.

        If :attr:`user_project` is set, bills the API request to that project.

        :type client: :class:`~google.cloud.storage.client.Client` or
                      ``NoneType``
        :param client: the client to use. If not passed, falls back to the
                       ``client`` stored on the current object.

        :type projection: str
        :param projection: (Optional) If used, must be 'full' or 'noAcl'.
                           Defaults to ``'noAcl'``. Specifies the set of
                           properties to return.

        :type timeout: float or tuple
        :param timeout: (Optional) The amount of time, in seconds, to wait
            for the server response.

            Can also be passed as a tuple (connect_timeout, read_timeout).
            See :meth:`requests.Session.request` documentation for details.

        :type if_metageneration_match: long
        :param if_metageneration_match: (Optional) Make the operation conditional on whether the
                                        blob's current metageneration matches the given value.

        :type if_metageneration_not_match: long
        :param if_metageneration_not_match: (Optional) Make the operation conditional on whether the
                                            blob's current metageneration does not match the given value.

        :type retry: google.api_core.retry.Retry or google.cloud.storage.retry.ConditionalRetryPolicy
        :param retry: (Optional) How to retry the RPC. A None value will disable retries.
            A google.api_core.retry.Retry value will enable retries, and the object will
            define retriable response codes and errors and configure backoff and timeout options.

            A google.cloud.storage.retry.ConditionalRetryPolicy value wraps a Retry object and
            activates it only if certain conditions are met. This class exists to provide safe defaults
            for RPC calls that are not technically safe to retry normally (due to potential data
            duplication or other side-effects) but become safe to retry if a condition such as
            if_metageneration_match is set.

            See the retry.py source code and docstrings in this package (google.cloud.storage.retry) for
            information on retry types and how to configure them.
        """
        super(Bucket, self).reload(
            client=client,
            projection=projection,
            timeout=timeout,
            if_metageneration_match=if_metageneration_match,
            if_metageneration_not_match=if_metageneration_not_match,
            retry=retry,
        )

    def patch(
        self,
        client=None,
        timeout=_DEFAULT_TIMEOUT,
        if_metageneration_match=None,
        if_metageneration_not_match=None,
        retry=DEFAULT_RETRY_IF_METAGENERATION_SPECIFIED,
    ):
        """Sends all changed properties in a PATCH request.

        Updates the ``_properties`` with the response from the backend.

        If :attr:`user_project` is set, bills the API request to that project.

        :type client: :class:`~google.cloud.storage.client.Client` or
                      ``NoneType``
        :param client: the client to use. If not passed, falls back to the
                       ``client`` stored on the current object.

        :type timeout: float or tuple
        :param timeout: (Optional) The amount of time, in seconds, to wait
            for the server response.

            Can also be passed as a tuple (connect_timeout, read_timeout).
            See :meth:`requests.Session.request` documentation for details.

        :type if_metageneration_match: long
        :param if_metageneration_match: (Optional) Make the operation conditional on whether the
                                        blob's current metageneration matches the given value.

        :type if_metageneration_not_match: long
        :param if_metageneration_not_match: (Optional) Make the operation conditional on whether the
                                            blob's current metageneration does not match the given value.

        :type retry: google.api_core.retry.Retry or google.cloud.storage.retry.ConditionalRetryPolicy
        :param retry: (Optional) How to retry the RPC. A None value will disable retries.
            A google.api_core.retry.Retry value will enable retries, and the object will
            define retriable response codes and errors and configure backoff and timeout options.

            A google.cloud.storage.retry.ConditionalRetryPolicy value wraps a Retry object and
            activates it only if certain conditions are met. This class exists to provide safe defaults
            for RPC calls that are not technically safe to retry normally (due to potential data
            duplication or other side-effects) but become safe to retry if a condition such as
            if_metageneration_match is set.

            See the retry.py source code and docstrings in this package (google.cloud.storage.retry) for
            information on retry types and how to configure them.
        """
        # Special case: For buckets, it is possible that labels are being
        # removed; this requires special handling.
        if self._label_removals:
            self._changes.add("labels")
            self._properties.setdefault("labels", {})
            for removed_label in self._label_removals:
                self._properties["labels"][removed_label] = None

        # Call the superclass method.
        super(Bucket, self).patch(
            client=client,
            timeout=timeout,
            if_metageneration_match=if_metageneration_match,
            if_metageneration_not_match=if_metageneration_not_match,
            retry=retry,
        )

    @property
    def acl(self):
        """Create our ACL on demand."""
        return self._acl

    @property
    def default_object_acl(self):
        """Create our defaultObjectACL on demand."""
        return self._default_object_acl

    @staticmethod
    def path_helper(bucket_name):
        """Relative URL path for a bucket.

        :type bucket_name: str
        :param bucket_name: The bucket name in the path.

        :rtype: str
        :returns: The relative URL path for ``bucket_name``.
        """
        return "/b/" + bucket_name

    @property
    def path(self):
        """The URL path to this bucket."""
        if not self.name:
            raise ValueError("Cannot determine path without bucket name.")

        return self.path_helper(self.name)

    def get_blob(
        self,
        blob_name,
        client=None,
        encryption_key=None,
        generation=None,
        timeout=_DEFAULT_TIMEOUT,
        if_generation_match=None,
        if_generation_not_match=None,
        if_metageneration_match=None,
        if_metageneration_not_match=None,
        retry=DEFAULT_RETRY,
        **kwargs
    ):
        """Get a blob object by name.

        This will return None if the blob doesn't exist:

        .. literalinclude:: snippets.py
          :start-after: [START get_blob]
          :end-before: [END get_blob]
          :dedent: 4

        If :attr:`user_project` is set, bills the API request to that project.

        :type blob_name: str
        :param blob_name: The name of the blob to retrieve.

        :type client: :class:`~google.cloud.storage.client.Client` or
                      ``NoneType``
        :param client: (Optional) The client to use.  If not passed, falls back
                       to the ``client`` stored on the current bucket.

        :type encryption_key: bytes
        :param encryption_key:
            (Optional) 32 byte encryption key for customer-supplied encryption.
            See
            https://cloud.google.com/storage/docs/encryption#customer-supplied.

        :type generation: long
        :param generation: (Optional) If present, selects a specific revision of
                           this object.

        :type timeout: float or tuple
        :param timeout: (Optional) The amount of time, in seconds, to wait
            for the server response.

            Can also be passed as a tuple (connect_timeout, read_timeout).
            See :meth:`requests.Session.request` documentation for details.

        :type if_generation_match: long
        :param if_generation_match: (Optional) Make the operation conditional on whether
                                    the blob's current generation matches the given value.
                                    Setting to 0 makes the operation succeed only if there
                                    are no live versions of the blob.

        :type if_generation_not_match: long
        :param if_generation_not_match: (Optional) Make the operation conditional on whether
                                        the blob's current generation does not match the given
                                        value. If no live blob exists, the precondition fails.
                                        Setting to 0 makes the operation succeed only if there
                                        is a live version of the blob.

        :type if_metageneration_match: long
        :param if_metageneration_match: (Optional) Make the operation conditional on whether the
                                        blob's current metageneration matches the given value.

        :type if_metageneration_not_match: long
        :param if_metageneration_not_match: (Optional) Make the operation conditional on whether the
                                            blob's current metageneration does not match the given value.

        :type retry: google.api_core.retry.Retry or google.cloud.storage.retry.ConditionalRetryPolicy
        :param retry: (Optional) How to retry the RPC. A None value will disable retries.
            A google.api_core.retry.Retry value will enable retries, and the object will
            define retriable response codes and errors and configure backoff and timeout options.

            A google.cloud.storage.retry.ConditionalRetryPolicy value wraps a Retry object and
            activates it only if certain conditions are met. This class exists to provide safe defaults
            for RPC calls that are not technically safe to retry normally (due to potential data
            duplication or other side-effects) but become safe to retry if a condition such as
            if_metageneration_match is set.

            See the retry.py source code and docstrings in this package (google.cloud.storage.retry) for
            information on retry types and how to configure them.

        :param kwargs: Keyword arguments to pass to the
                       :class:`~google.cloud.storage.blob.Blob` constructor.

        :rtype: :class:`google.cloud.storage.blob.Blob` or None
        :returns: The blob object if it exists, otherwise None.
        """
        blob = Blob(
            bucket=self,
            name=blob_name,
            encryption_key=encryption_key,
            generation=generation,
            **kwargs
        )
        try:
            # NOTE: This will not fail immediately in a batch. However, when
            #       Batch.finish() is called, the resulting `NotFound` will be
            #       raised.
            blob.reload(
                client=client,
                timeout=timeout,
                if_generation_match=if_generation_match,
                if_generation_not_match=if_generation_not_match,
                if_metageneration_match=if_metageneration_match,
                if_metageneration_not_match=if_metageneration_not_match,
                retry=retry,
            )
        except NotFound:
            return None
        else:
            return blob

    def list_blobs(
        self,
        max_results=None,
        page_token=None,
        prefix=None,
        delimiter=None,
        start_offset=None,
        end_offset=None,
        include_trailing_delimiter=None,
        versions=None,
        projection="noAcl",
        fields=None,
        client=None,
        timeout=_DEFAULT_TIMEOUT,
        retry=DEFAULT_RETRY,
    ):
        """DEPRECATED. Return an iterator used to find blobs in the bucket.

        .. note::
          Direct use of this method is deprecated. Use ``Client.list_blobs`` instead.

        If :attr:`user_project` is set, bills the API request to that project.

        :type max_results: int
        :param max_results:
            (Optional) The maximum number of blobs to return.

        :type page_token: str
        :param page_token:
            (Optional) If present, return the next batch of blobs, using the
            value, which must correspond to the ``nextPageToken`` value
            returned in the previous response.  Deprecated: use the ``pages``
            property of the returned iterator instead of manually passing the
            token.

        :type prefix: str
        :param prefix: (Optional) Prefix used to filter blobs.

        :type delimiter: str
        :param delimiter: (Optional) Delimiter, used with ``prefix`` to
                          emulate hierarchy.

        :type start_offset: str
        :param start_offset:
            (Optional) Filter results to objects whose names are
            lexicographically equal to or after ``startOffset``. If
            ``endOffset`` is also set, the objects listed will have names
            between ``startOffset`` (inclusive) and ``endOffset`` (exclusive).

        :type end_offset: str
        :param end_offset:
            (Optional) Filter results to objects whose names are
            lexicographically before ``endOffset``. If ``startOffset`` is also
            set, the objects listed will have names between ``startOffset``
            (inclusive) and ``endOffset`` (exclusive).

        :type include_trailing_delimiter: boolean
        :param include_trailing_delimiter:
            (Optional) If true, objects that end in exactly one instance of
            ``delimiter`` will have their metadata included in ``items`` in
            addition to ``prefixes``.

        :type versions: bool
        :param versions: (Optional) Whether object versions should be returned
                         as separate blobs.

        :type projection: str
        :param projection: (Optional) If used, must be 'full' or 'noAcl'.
                           Defaults to ``'noAcl'``. Specifies the set of
                           properties to return.

        :type fields: str
        :param fields:
            (Optional) Selector specifying which fields to include
            in a partial response. Must be a list of fields. For
            example to get a partial response with just the next
            page token and the name and language of each blob returned:
            ``'items(name,contentLanguage),nextPageToken'``.
            See: https://cloud.google.com/storage/docs/json_api/v1/parameters#fields

        :type client: :class:`~google.cloud.storage.client.Client`
        :param client: (Optional) The client to use.  If not passed, falls back
                       to the ``client`` stored on the current bucket.

        :type timeout: float or tuple
        :param timeout: (Optional) The amount of time, in seconds, to wait
            for the server response.

            Can also be passed as a tuple (connect_timeout, read_timeout).
            See :meth:`requests.Session.request` documentation for details.

        :type retry: google.api_core.retry.Retry or google.cloud.storage.retry.ConditionalRetryPolicy
        :param retry: (Optional) How to retry the RPC. A None value will disable retries.
            A google.api_core.retry.Retry value will enable retries, and the object will
            define retriable response codes and errors and configure backoff and timeout options.

            A google.cloud.storage.retry.ConditionalRetryPolicy value wraps a Retry object and
            activates it only if certain conditions are met. This class exists to provide safe defaults
            for RPC calls that are not technically safe to retry normally (due to potential data
            duplication or other side-effects) but become safe to retry if a condition such as
            if_metageneration_match is set.

            See the retry.py source code and docstrings in this package (google.cloud.storage.retry) for
            information on retry types and how to configure them.

        :rtype: :class:`~google.api_core.page_iterator.Iterator`
        :returns: Iterator of all :class:`~google.cloud.storage.blob.Blob`
                  in this bucket matching the arguments.

        Example:
            List blobs in the bucket with user_project.

            >>> from google.cloud import storage
            >>> client = storage.Client()

            >>> bucket = storage.Bucket(client, "my-bucket-name", user_project="my-project")
            >>> all_blobs = list(client.list_blobs(bucket))
        """
        client = self._require_client(client)
        return client.list_blobs(
            self,
            max_results=max_results,
            page_token=page_token,
            prefix=prefix,
            delimiter=delimiter,
            start_offset=start_offset,
            end_offset=end_offset,
            include_trailing_delimiter=include_trailing_delimiter,
            versions=versions,
            projection=projection,
            fields=fields,
            timeout=timeout,
            retry=retry,
        )

    def list_notifications(
        self, client=None, timeout=_DEFAULT_TIMEOUT, retry=DEFAULT_RETRY
    ):
        """List Pub / Sub notifications for this bucket.

        See:
        https://cloud.google.com/storage/docs/json_api/v1/notifications/list

        If :attr:`user_project` is set, bills the API request to that project.

        :type client: :class:`~google.cloud.storage.client.Client` or
                      ``NoneType``
        :param client: (Optional) The client to use.  If not passed, falls back
                       to the ``client`` stored on the current bucket.
        :type timeout: float or tuple
        :param timeout: (Optional) The amount of time, in seconds, to wait
            for the server response.

            Can also be passed as a tuple (connect_timeout, read_timeout).
            See :meth:`requests.Session.request` documentation for details.

        :type retry: google.api_core.retry.Retry or google.cloud.storage.retry.ConditionalRetryPolicy
        :param retry: (Optional) How to retry the RPC. A None value will disable retries.
            A google.api_core.retry.Retry value will enable retries, and the object will
            define retriable response codes and errors and configure backoff and timeout options.

            A google.cloud.storage.retry.ConditionalRetryPolicy value wraps a Retry object and
            activates it only if certain conditions are met. This class exists to provide safe defaults
            for RPC calls that are not technically safe to retry normally (due to potential data
            duplication or other side-effects) but become safe to retry if a condition such as
            if_metageneration_match is set.

            See the retry.py source code and docstrings in this package (google.cloud.storage.retry) for
            information on retry types and how to configure them.

        :rtype: list of :class:`.BucketNotification`
        :returns: notification instances
        """
        client = self._require_client(client)
        path = self.path + "/notificationConfigs"
        api_request = functools.partial(
            client._connection.api_request, timeout=timeout, retry=retry
        )
        iterator = page_iterator.HTTPIterator(
            client=client,
            api_request=api_request,
            path=path,
            item_to_value=_item_to_notification,
        )
        iterator.bucket = self
        return iterator

    def get_notification(
        self,
        notification_id,
        client=None,
        timeout=_DEFAULT_TIMEOUT,
        retry=DEFAULT_RETRY,
    ):
        """Get Pub / Sub notification for this bucket.

        See:
        https://cloud.google.com/storage/docs/json_api/v1/notifications/get

        If :attr:`user_project` is set, bills the API request to that project.

        :type notification_id: str
        :param notification_id: The notification id to retrieve the notification configuration.

        :type client: :class:`~google.cloud.storage.client.Client` or
                      ``NoneType``
        :param client: (Optional) The client to use.  If not passed, falls back
                       to the ``client`` stored on the current bucket.
        :type timeout: float or tuple
        :param timeout: (Optional) The amount of time, in seconds, to wait
            for the server response.

            Can also be passed as a tuple (connect_timeout, read_timeout).
            See :meth:`requests.Session.request` documentation for details.

        :type retry: google.api_core.retry.Retry or google.cloud.storage.retry.ConditionalRetryPolicy
        :param retry: (Optional) How to retry the RPC. A None value will disable retries.
            A google.api_core.retry.Retry value will enable retries, and the object will
            define retriable response codes and errors and configure backoff and timeout options.

            A google.cloud.storage.retry.ConditionalRetryPolicy value wraps a Retry object and
            activates it only if certain conditions are met. This class exists to provide safe defaults
            for RPC calls that are not technically safe to retry normally (due to potential data
            duplication or other side-effects) but become safe to retry if a condition such as
            if_metageneration_match is set.

            See the retry.py source code and docstrings in this package (google.cloud.storage.retry) for
            information on retry types and how to configure them.

        :rtype: :class:`.BucketNotification`
        :returns: notification instance.

        Example:
            Get notification using notification id.

            >>> from google.cloud import storage
            >>> client = storage.Client()
            >>> bucket = client.get_bucket('my-bucket-name')  # API request.
            >>> notification = bucket.get_notification(notification_id='id')  # API request.

        """
        notification = self.notification(notification_id=notification_id)
        notification.reload(client=client, timeout=timeout, retry=retry)
        return notification

    def delete(
        self,
        force=False,
        client=None,
        timeout=_DEFAULT_TIMEOUT,
        if_metageneration_match=None,
        if_metageneration_not_match=None,
        retry=DEFAULT_RETRY,
    ):
        """Delete this bucket.

        The bucket **must** be empty in order to submit a delete request. If
        ``force=True`` is passed, this will first attempt to delete all the
        objects / blobs in the bucket (i.e. try to empty the bucket).

        If the bucket doesn't exist, this will raise
        :class:`google.cloud.exceptions.NotFound`. If the bucket is not empty
        (and ``force=False``), will raise :class:`google.cloud.exceptions.Conflict`.

        If ``force=True`` and the bucket contains more than 256 objects / blobs
        this will cowardly refuse to delete the objects (or the bucket). This
        is to prevent accidental bucket deletion and to prevent extremely long
        runtime of this method.

        If :attr:`user_project` is set, bills the API request to that project.

        :type force: bool
        :param force: If True, empties the bucket's objects then deletes it.

        :type client: :class:`~google.cloud.storage.client.Client` or
                      ``NoneType``
        :param client: (Optional) The client to use. If not passed, falls back
                       to the ``client`` stored on the current bucket.

        :type timeout: float or tuple
        :param timeout: (Optional) The amount of time, in seconds, to wait
            for the server response on each request.

            Can also be passed as a tuple (connect_timeout, read_timeout).
            See :meth:`requests.Session.request` documentation for details.

        :type if_metageneration_match: long
        :param if_metageneration_match: (Optional) Make the operation conditional on whether the
                                        blob's current metageneration matches the given value.

        :type if_metageneration_not_match: long
        :param if_metageneration_not_match: (Optional) Make the operation conditional on whether the
                                            blob's current metageneration does not match the given value.

        :type retry: google.api_core.retry.Retry or google.cloud.storage.retry.ConditionalRetryPolicy
        :param retry: (Optional) How to retry the RPC. A None value will disable retries.
            A google.api_core.retry.Retry value will enable retries, and the object will
            define retriable response codes and errors and configure backoff and timeout options.

            A google.cloud.storage.retry.ConditionalRetryPolicy value wraps a Retry object and
            activates it only if certain conditions are met. This class exists to provide safe defaults
            for RPC calls that are not technically safe to retry normally (due to potential data
            duplication or other side-effects) but become safe to retry if a condition such as
            if_metageneration_match is set.

            See the retry.py source code and docstrings in this package (google.cloud.storage.retry) for
            information on retry types and how to configure them.

        :raises: :class:`ValueError` if ``force`` is ``True`` and the bucket
                 contains more than 256 objects / blobs.
        """
        client = self._require_client(client)
        query_params = {}

        if self.user_project is not None:
            query_params["userProject"] = self.user_project

        _add_generation_match_parameters(
            query_params,
            if_metageneration_match=if_metageneration_match,
            if_metageneration_not_match=if_metageneration_not_match,
        )
        if force:
            blobs = list(
                self.list_blobs(
                    max_results=self._MAX_OBJECTS_FOR_ITERATION + 1,
                    client=client,
                    timeout=timeout,
                )
            )
            if len(blobs) > self._MAX_OBJECTS_FOR_ITERATION:
                message = (
                    "Refusing to delete bucket with more than "
                    "%d objects. If you actually want to delete "
                    "this bucket, please delete the objects "
                    "yourself before calling Bucket.delete()."
                ) % (self._MAX_OBJECTS_FOR_ITERATION,)
                raise ValueError(message)

            # Ignore 404 errors on delete.
            self.delete_blobs(
                blobs, on_error=lambda blob: None, client=client, timeout=timeout
            )

        # We intentionally pass `_target_object=None` since a DELETE
        # request has no response value (whether in a standard request or
        # in a batch request).
        client._connection.api_request(
            method="DELETE",
            path=self.path,
            query_params=query_params,
            _target_object=None,
            timeout=timeout,
            retry=retry,
        )

    def delete_blob(
        self,
        blob_name,
        client=None,
        generation=None,
        timeout=_DEFAULT_TIMEOUT,
        if_generation_match=None,
        if_generation_not_match=None,
        if_metageneration_match=None,
        if_metageneration_not_match=None,
        retry=DEFAULT_RETRY_IF_GENERATION_SPECIFIED,
    ):
        """Deletes a blob from the current bucket.

        If the blob isn't found (backend 404), raises a
        :class:`google.cloud.exceptions.NotFound`.

        For example:

        .. literalinclude:: snippets.py
          :start-after: [START delete_blob]
          :end-before: [END delete_blob]
          :dedent: 4

        If :attr:`user_project` is set, bills the API request to that project.

        :type blob_name: str
        :param blob_name: A blob name to delete.

        :type client: :class:`~google.cloud.storage.client.Client` or
                      ``NoneType``
        :param client: (Optional) The client to use. If not passed, falls back
                       to the ``client`` stored on the current bucket.

        :type generation: long
        :param generation: (Optional) If present, permanently deletes a specific
                           revision of this object.

        :type timeout: float or tuple
        :param timeout: (Optional) The amount of time, in seconds, to wait
            for the server response.

            Can also be passed as a tuple (connect_timeout, read_timeout).
            See :meth:`requests.Session.request` documentation for details.

        :type if_generation_match: long
        :param if_generation_match: (Optional) Make the operation conditional on whether
                                    the blob's current generation matches the given value.
                                    Setting to 0 makes the operation succeed only if there
                                    are no live versions of the blob.

        :type if_generation_not_match: long
        :param if_generation_not_match: (Optional) Make the operation conditional on whether
                                        the blob's current generation does not match the given
                                        value. If no live blob exists, the precondition fails.
                                        Setting to 0 makes the operation succeed only if there
                                        is a live version of the blob.

        :type if_metageneration_match: long
        :param if_metageneration_match: (Optional) Make the operation conditional on whether the
                                        blob's current metageneration matches the given value.

        :type if_metageneration_not_match: long
        :param if_metageneration_not_match: (Optional) Make the operation conditional on whether the
                                            blob's current metageneration does not match the given value.

        :type retry: google.api_core.retry.Retry or google.cloud.storage.retry.ConditionalRetryPolicy
        :param retry: (Optional) How to retry the RPC. A None value will disable retries.
            A google.api_core.retry.Retry value will enable retries, and the object will
            define retriable response codes and errors and configure backoff and timeout options.

            A google.cloud.storage.retry.ConditionalRetryPolicy value wraps a Retry object and
            activates it only if certain conditions are met. This class exists to provide safe defaults
            for RPC calls that are not technically safe to retry normally (due to potential data
            duplication or other side-effects) but become safe to retry if a condition such as
            if_metageneration_match is set.

            See the retry.py source code and docstrings in this package (google.cloud.storage.retry) for
            information on retry types and how to configure them.

        :raises: :class:`google.cloud.exceptions.NotFound` (to suppress
                 the exception, call ``delete_blobs``, passing a no-op
                 ``on_error`` callback, e.g.:

        .. literalinclude:: snippets.py
            :start-after: [START delete_blobs]
            :end-before: [END delete_blobs]
            :dedent: 4

        """
        client = self._require_client(client)
        blob = Blob(blob_name, bucket=self, generation=generation)

        query_params = copy.deepcopy(blob._query_params)
        _add_generation_match_parameters(
            query_params,
            if_generation_match=if_generation_match,
            if_generation_not_match=if_generation_not_match,
            if_metageneration_match=if_metageneration_match,
            if_metageneration_not_match=if_metageneration_not_match,
        )
        # We intentionally pass `_target_object=None` since a DELETE
        # request has no response value (whether in a standard request or
        # in a batch request).
        client._connection.api_request(
            method="DELETE",
            path=blob.path,
            query_params=query_params,
            _target_object=None,
            timeout=timeout,
            retry=retry,
        )

    def delete_blobs(
        self,
        blobs,
        on_error=None,
        client=None,
        timeout=_DEFAULT_TIMEOUT,
        if_generation_match=None,
        if_generation_not_match=None,
        if_metageneration_match=None,
        if_metageneration_not_match=None,
        retry=DEFAULT_RETRY_IF_GENERATION_SPECIFIED,
    ):
        """Deletes a list of blobs from the current bucket.

        Uses :meth:`delete_blob` to delete each individual blob.

        If :attr:`user_project` is set, bills the API request to that project.

        :type blobs: list
        :param blobs: A list of :class:`~google.cloud.storage.blob.Blob`-s or
                      blob names to delete.

        :type on_error: callable
        :param on_error: (Optional) Takes single argument: ``blob``. Called
                         called once for each blob raising
                         :class:`~google.cloud.exceptions.NotFound`;
                         otherwise, the exception is propagated.

        :type client: :class:`~google.cloud.storage.client.Client`
        :param client: (Optional) The client to use.  If not passed, falls back
                       to the ``client`` stored on the current bucket.

        :type timeout: float or tuple
        :param timeout: (Optional) The amount of time, in seconds, to wait
            for the server response. The timeout applies to each individual
            blob delete request.

            Can also be passed as a tuple (connect_timeout, read_timeout).
            See :meth:`requests.Session.request` documentation for details.

        :type if_generation_match: list of long
        :param if_generation_match: (Optional) Make the operation conditional on whether
                                    the blob's current generation matches the given value.
                                    Setting to 0 makes the operation succeed only if there
                                    are no live versions of the blob. The list must match
                                    ``blobs`` item-to-item.

        :type if_generation_not_match: list of long
        :param if_generation_not_match: (Optional) Make the operation conditional on whether
                                        the blob's current generation does not match the given
                                        value. If no live blob exists, the precondition fails.
                                        Setting to 0 makes the operation succeed only if there
                                        is a live version of the blob. The list must match
                                        ``blobs`` item-to-item.

        :type if_metageneration_match: list of long
        :param if_metageneration_match: (Optional) Make the operation conditional on whether the
                                        blob's current metageneration matches the given value.
                                        The list must match ``blobs`` item-to-item.

        :type if_metageneration_not_match: list of long
        :param if_metageneration_not_match: (Optional) Make the operation conditional on whether the
                                            blob's current metageneration does not match the given value.
                                            The list must match ``blobs`` item-to-item.

        :type retry: google.api_core.retry.Retry or google.cloud.storage.retry.ConditionalRetryPolicy
        :param retry: (Optional) How to retry the RPC. A None value will disable retries.
            A google.api_core.retry.Retry value will enable retries, and the object will
            define retriable response codes and errors and configure backoff and timeout options.

            A google.cloud.storage.retry.ConditionalRetryPolicy value wraps a Retry object and
            activates it only if certain conditions are met. This class exists to provide safe defaults
            for RPC calls that are not technically safe to retry normally (due to potential data
            duplication or other side-effects) but become safe to retry if a condition such as
            if_metageneration_match is set.

            See the retry.py source code and docstrings in this package (google.cloud.storage.retry) for
            information on retry types and how to configure them.

        :raises: :class:`~google.cloud.exceptions.NotFound` (if
                 `on_error` is not passed).

        Example:
            Delete blobs using generation match preconditions.

            >>> from google.cloud import storage

            >>> client = storage.Client()
            >>> bucket = client.bucket("bucket-name")

            >>> blobs = [bucket.blob("blob-name-1"), bucket.blob("blob-name-2")]
            >>> if_generation_match = [None] * len(blobs)
            >>> if_generation_match[0] = "123"  # precondition for "blob-name-1"

            >>> bucket.delete_blobs(blobs, if_generation_match=if_generation_match)
        """
        _raise_if_len_differs(
            len(blobs),
            if_generation_match=if_generation_match,
            if_generation_not_match=if_generation_not_match,
            if_metageneration_match=if_metageneration_match,
            if_metageneration_not_match=if_metageneration_not_match,
        )
        if_generation_match = iter(if_generation_match or [])
        if_generation_not_match = iter(if_generation_not_match or [])
        if_metageneration_match = iter(if_metageneration_match or [])
        if_metageneration_not_match = iter(if_metageneration_not_match or [])

        for blob in blobs:
            try:
                blob_name = blob
                if not isinstance(blob_name, six.string_types):
                    blob_name = blob.name
                self.delete_blob(
                    blob_name,
                    client=client,
                    timeout=timeout,
                    if_generation_match=next(if_generation_match, None),
                    if_generation_not_match=next(if_generation_not_match, None),
                    if_metageneration_match=next(if_metageneration_match, None),
                    if_metageneration_not_match=next(if_metageneration_not_match, None),
                    retry=retry,
                )
            except NotFound:
                if on_error is not None:
                    on_error(blob)
                else:
                    raise

    def copy_blob(
        self,
        blob,
        destination_bucket,
        new_name=None,
        client=None,
        preserve_acl=True,
        source_generation=None,
        timeout=_DEFAULT_TIMEOUT,
        if_generation_match=None,
        if_generation_not_match=None,
        if_metageneration_match=None,
        if_metageneration_not_match=None,
        if_source_generation_match=None,
        if_source_generation_not_match=None,
        if_source_metageneration_match=None,
        if_source_metageneration_not_match=None,
        retry=DEFAULT_RETRY_IF_GENERATION_SPECIFIED,
    ):
        """Copy the given blob to the given bucket, optionally with a new name.

        If :attr:`user_project` is set, bills the API request to that project.

        :type blob: :class:`google.cloud.storage.blob.Blob`
        :param blob: The blob to be copied.

        :type destination_bucket: :class:`google.cloud.storage.bucket.Bucket`
        :param destination_bucket: The bucket into which the blob should be
                                   copied.

        :type new_name: str
        :param new_name: (Optional) The new name for the copied file.

        :type client: :class:`~google.cloud.storage.client.Client` or
                      ``NoneType``
        :param client: (Optional) The client to use. If not passed, falls back
                       to the ``client`` stored on the current bucket.

        :type preserve_acl: bool
        :param preserve_acl: DEPRECATED. This argument is not functional!
                             (Optional) Copies ACL from old blob to new blob.
                             Default: True.

        :type source_generation: long
        :param source_generation: (Optional) The generation of the blob to be
                                  copied.

        :type timeout: float or tuple
        :param timeout: (Optional) The amount of time, in seconds, to wait
            for the server response.

            Can also be passed as a tuple (connect_timeout, read_timeout).
            See :meth:`requests.Session.request` documentation for details.

        :type if_generation_match: long
        :param if_generation_match: (Optional) Makes the operation
                                    conditional on whether the destination
                                    object's current generation matches the
                                    given value. Setting to 0 makes the
                                    operation succeed only if there are no
                                    live versions of the object.

        :type if_generation_not_match: long
        :param if_generation_not_match: (Optional) Makes the operation
                                        conditional on whether the
                                        destination object's current
                                        generation does not match the given
                                        value. If no live object exists,
                                        the precondition fails. Setting to
                                        0 makes the operation succeed only
                                        if there is a live version
                                        of the object.

        :type if_metageneration_match: long
        :param if_metageneration_match: (Optional) Makes the operation
                                        conditional on whether the
                                        destination object's current
                                        metageneration matches the given
                                        value.

        :type if_metageneration_not_match: long
        :param if_metageneration_not_match: (Optional) Makes the operation
                                            conditional on whether the
                                            destination object's current
                                            metageneration does not match
                                            the given value.

        :type if_source_generation_match: long
        :param if_source_generation_match: (Optional) Makes the operation
                                           conditional on whether the source
                                           object's generation matches the
                                           given value.

        :type if_source_generation_not_match: long
        :param if_source_generation_not_match: (Optional) Makes the operation
                                               conditional on whether the source
                                               object's generation does not match
                                               the given value.

        :type if_source_metageneration_match: long
        :param if_source_metageneration_match: (Optional) Makes the operation
                                               conditional on whether the source
                                               object's current metageneration
                                               matches the given value.

        :type if_source_metageneration_not_match: long
        :param if_source_metageneration_not_match: (Optional) Makes the operation
                                                   conditional on whether the source
                                                   object's current metageneration
                                                   does not match the given value.

        :type retry: google.api_core.retry.Retry or google.cloud.storage.retry.ConditionalRetryPolicy
        :param retry: (Optional) How to retry the RPC. A None value will disable retries.
            A google.api_core.retry.Retry value will enable retries, and the object will
            define retriable response codes and errors and configure backoff and timeout options.

            A google.cloud.storage.retry.ConditionalRetryPolicy value wraps a Retry object and
            activates it only if certain conditions are met. This class exists to provide safe defaults
            for RPC calls that are not technically safe to retry normally (due to potential data
            duplication or other side-effects) but become safe to retry if a condition such as
            if_metageneration_match is set.

            See the retry.py source code and docstrings in this package (google.cloud.storage.retry) for
            information on retry types and how to configure them.

        :rtype: :class:`google.cloud.storage.blob.Blob`
        :returns: The new Blob.

        Example:
            Copy a blob including ACL.

            >>> from google.cloud import storage

            >>> client = storage.Client(project="project")

            >>> bucket = client.bucket("bucket")
            >>> dst_bucket = client.bucket("destination-bucket")

            >>> blob = bucket.blob("file.ext")
            >>> new_blob = bucket.copy_blob(blob, dst_bucket)
            >>> new_blob.acl.save(blob.acl)
        """
        client = self._require_client(client)
        query_params = {}

        if self.user_project is not None:
            query_params["userProject"] = self.user_project

        if source_generation is not None:
            query_params["sourceGeneration"] = source_generation

        _add_generation_match_parameters(
            query_params,
            if_generation_match=if_generation_match,
            if_generation_not_match=if_generation_not_match,
            if_metageneration_match=if_metageneration_match,
            if_metageneration_not_match=if_metageneration_not_match,
            if_source_generation_match=if_source_generation_match,
            if_source_generation_not_match=if_source_generation_not_match,
            if_source_metageneration_match=if_source_metageneration_match,
            if_source_metageneration_not_match=if_source_metageneration_not_match,
        )

        if new_name is None:
            new_name = blob.name

        new_blob = Blob(bucket=destination_bucket, name=new_name)
        api_path = blob.path + "/copyTo" + new_blob.path
        copy_result = client._connection.api_request(
            method="POST",
            path=api_path,
            query_params=query_params,
            _target_object=new_blob,
            timeout=timeout,
            retry=retry,
        )

        if not preserve_acl:
            new_blob.acl.save(acl={}, client=client, timeout=timeout)

        new_blob._set_properties(copy_result)
        return new_blob

    def rename_blob(
        self,
        blob,
        new_name,
        client=None,
        timeout=_DEFAULT_TIMEOUT,
        if_generation_match=None,
        if_generation_not_match=None,
        if_metageneration_match=None,
        if_metageneration_not_match=None,
        if_source_generation_match=None,
        if_source_generation_not_match=None,
        if_source_metageneration_match=None,
        if_source_metageneration_not_match=None,
        retry=DEFAULT_RETRY_IF_GENERATION_SPECIFIED,
    ):
        """Rename the given blob using copy and delete operations.

        If :attr:`user_project` is set, bills the API request to that project.

        Effectively, copies blob to the same bucket with a new name, then
        deletes the blob.

        .. warning::

          This method will first duplicate the data and then delete the
          old blob.  This means that with very large objects renaming
          could be a very (temporarily) costly or a very slow operation.
          If you need more control over the copy and deletion, instead
          use `google.cloud.storage.blob.Blob.copy_to` and
          `google.cloud.storage.blob.Blob.delete` directly.

        :type blob: :class:`google.cloud.storage.blob.Blob`
        :param blob: The blob to be renamed.

        :type new_name: str
        :param new_name: The new name for this blob.

        :type client: :class:`~google.cloud.storage.client.Client` or
                      ``NoneType``
        :param client: (Optional) The client to use.  If not passed, falls back
                       to the ``client`` stored on the current bucket.

        :type timeout: float or tuple
        :param timeout: (Optional) The amount of time, in seconds, to wait
            for the server response. The timeout applies to each individual
            request.

            Can also be passed as a tuple (connect_timeout, read_timeout).
            See :meth:`requests.Session.request` documentation for details.

        :type if_generation_match: long
        :param if_generation_match: (Optional) Makes the operation
                                    conditional on whether the destination
                                    object's current generation matches the
                                    given value. Setting to 0 makes the
                                    operation succeed only if there are no
                                    live versions of the object.

        :type if_generation_not_match: long
        :param if_generation_not_match: (Optional) Makes the operation
                                        conditional on whether the
                                        destination object's current
                                        generation does not match the given
                                        value. If no live object exists,
                                        the precondition fails. Setting to
                                        0 makes the operation succeed only
                                        if there is a live version
                                        of the object.

        :type if_metageneration_match: long
        :param if_metageneration_match: (Optional) Makes the operation
                                        conditional on whether the
                                        destination object's current
                                        metageneration matches the given
                                        value.

        :type if_metageneration_not_match: long
        :param if_metageneration_not_match: (Optional) Makes the operation
                                            conditional on whether the
                                            destination object's current
                                            metageneration does not match
                                            the given value.

        :type if_source_generation_match: long
        :param if_source_generation_match: (Optional) Makes the operation
                                           conditional on whether the source
                                           object's generation matches the
                                           given value. Also used in the
                                           delete request.

        :type if_source_generation_not_match: long
        :param if_source_generation_not_match: (Optional) Makes the operation
                                               conditional on whether the source
                                               object's generation does not match
                                               the given value. Also used in the
                                               delete request.

        :type if_source_metageneration_match: long
        :param if_source_metageneration_match: (Optional) Makes the operation
                                               conditional on whether the source
                                               object's current metageneration
                                               matches the given value.Also used in the
                                               delete request.

        :type if_source_metageneration_not_match: long
        :param if_source_metageneration_not_match: (Optional) Makes the operation
                                                   conditional on whether the source
                                                   object's current metageneration
                                                   does not match the given value.
                                                   Also used in the delete request.

        :type retry: google.api_core.retry.Retry or google.cloud.storage.retry.ConditionalRetryPolicy
        :param retry: (Optional) How to retry the RPC. A None value will disable retries.
            A google.api_core.retry.Retry value will enable retries, and the object will
            define retriable response codes and errors and configure backoff and timeout options.

            A google.cloud.storage.retry.ConditionalRetryPolicy value wraps a Retry object and
            activates it only if certain conditions are met. This class exists to provide safe defaults
            for RPC calls that are not technically safe to retry normally (due to potential data
            duplication or other side-effects) but become safe to retry if a condition such as
            if_metageneration_match is set.

            See the retry.py source code and docstrings in this package (google.cloud.storage.retry) for
            information on retry types and how to configure them.

        :rtype: :class:`Blob`
        :returns: The newly-renamed blob.
        """
        same_name = blob.name == new_name

        new_blob = self.copy_blob(
            blob,
            self,
            new_name,
            client=client,
            timeout=timeout,
            if_generation_match=if_generation_match,
            if_generation_not_match=if_generation_not_match,
            if_metageneration_match=if_metageneration_match,
            if_metageneration_not_match=if_metageneration_not_match,
            if_source_generation_match=if_source_generation_match,
            if_source_generation_not_match=if_source_generation_not_match,
            if_source_metageneration_match=if_source_metageneration_match,
            if_source_metageneration_not_match=if_source_metageneration_not_match,
            retry=retry,
        )

        if not same_name:
            blob.delete(
                client=client,
                timeout=timeout,
                if_generation_match=if_source_generation_match,
                if_generation_not_match=if_source_generation_not_match,
                if_metageneration_match=if_source_metageneration_match,
                if_metageneration_not_match=if_source_metageneration_not_match,
                retry=retry,
            )
        return new_blob

    @property
    def cors(self):
        """Retrieve or set CORS policies configured for this bucket.

        See http://www.w3.org/TR/cors/ and
             https://cloud.google.com/storage/docs/json_api/v1/buckets

        .. note::

           The getter for this property returns a list which contains
           *copies* of the bucket's CORS policy mappings.  Mutating the list
           or one of its dicts has no effect unless you then re-assign the
           dict via the setter.  E.g.:

           >>> policies = bucket.cors
           >>> policies.append({'origin': '/foo', ...})
           >>> policies[1]['maxAgeSeconds'] = 3600
           >>> del policies[0]
           >>> bucket.cors = policies
           >>> bucket.update()

        :setter: Set CORS policies for this bucket.
        :getter: Gets the CORS policies for this bucket.

        :rtype: list of dictionaries
        :returns: A sequence of mappings describing each CORS policy.
        """
        return [copy.deepcopy(policy) for policy in self._properties.get("cors", ())]

    @cors.setter
    def cors(self, entries):
        """Set CORS policies configured for this bucket.

        See http://www.w3.org/TR/cors/ and
             https://cloud.google.com/storage/docs/json_api/v1/buckets

        :type entries: list of dictionaries
        :param entries: A sequence of mappings describing each CORS policy.
        """
        self._patch_property("cors", entries)

    default_event_based_hold = _scalar_property("defaultEventBasedHold")
    """Are uploaded objects automatically placed under an even-based hold?

    If True, uploaded objects will be placed under an event-based hold to
    be released at a future time. When released an object will then begin
    the retention period determined by the policy retention period for the
    object bucket.

    See https://cloud.google.com/storage/docs/json_api/v1/buckets

    If the property is not set locally, returns ``None``.

    :rtype: bool or ``NoneType``
    """

    @property
    def default_kms_key_name(self):
        """Retrieve / set default KMS encryption key for objects in the bucket.

        See https://cloud.google.com/storage/docs/json_api/v1/buckets

        :setter: Set default KMS encryption key for items in this bucket.
        :getter: Get default KMS encryption key for items in this bucket.

        :rtype: str
        :returns: Default KMS encryption key, or ``None`` if not set.
        """
        encryption_config = self._properties.get("encryption", {})
        return encryption_config.get("defaultKmsKeyName")

    @default_kms_key_name.setter
    def default_kms_key_name(self, value):
        """Set default KMS encryption key for objects in the bucket.

        :type value: str or None
        :param value: new KMS key name (None to clear any existing key).
        """
        encryption_config = self._properties.get("encryption", {})
        encryption_config["defaultKmsKeyName"] = value
        self._patch_property("encryption", encryption_config)

    @property
    def labels(self):
        """Retrieve or set labels assigned to this bucket.

        See
        https://cloud.google.com/storage/docs/json_api/v1/buckets#labels

        .. note::

           The getter for this property returns a dict which is a *copy*
           of the bucket's labels.  Mutating that dict has no effect unless
           you then re-assign the dict via the setter.  E.g.:

           >>> labels = bucket.labels
           >>> labels['new_key'] = 'some-label'
           >>> del labels['old_key']
           >>> bucket.labels = labels
           >>> bucket.update()

        :setter: Set labels for this bucket.
        :getter: Gets the labels for this bucket.

        :rtype: :class:`dict`
        :returns: Name-value pairs (string->string) labelling the bucket.
        """
        labels = self._properties.get("labels")
        if labels is None:
            return {}
        return copy.deepcopy(labels)

    @labels.setter
    def labels(self, mapping):
        """Set labels assigned to this bucket.

        See
        https://cloud.google.com/storage/docs/json_api/v1/buckets#labels

        :type mapping: :class:`dict`
        :param mapping: Name-value pairs (string->string) labelling the bucket.
        """
        # If any labels have been expressly removed, we need to track this
        # so that a future .patch() call can do the correct thing.
        existing = set([k for k in self.labels.keys()])
        incoming = set([k for k in mapping.keys()])
        self._label_removals = self._label_removals.union(existing.difference(incoming))
        mapping = {k: str(v) for k, v in mapping.items()}

        # Actually update the labels on the object.
        self._patch_property("labels", copy.deepcopy(mapping))

    @property
    def etag(self):
        """Retrieve the ETag for the bucket.

        See https://tools.ietf.org/html/rfc2616#section-3.11 and
             https://cloud.google.com/storage/docs/json_api/v1/buckets

        :rtype: str or ``NoneType``
        :returns: The bucket etag or ``None`` if the bucket's
                  resource has not been loaded from the server.
        """
        return self._properties.get("etag")

    @property
    def id(self):
        """Retrieve the ID for the bucket.

        See https://cloud.google.com/storage/docs/json_api/v1/buckets

        :rtype: str or ``NoneType``
        :returns: The ID of the bucket or ``None`` if the bucket's
                  resource has not been loaded from the server.
        """
        return self._properties.get("id")

    @property
    def iam_configuration(self):
        """Retrieve IAM configuration for this bucket.

        :rtype: :class:`IAMConfiguration`
        :returns: an instance for managing the bucket's IAM configuration.
        """
        info = self._properties.get("iamConfiguration", {})
        return IAMConfiguration.from_api_repr(info, self)

    @property
    def lifecycle_rules(self):
        """Retrieve or set lifecycle rules configured for this bucket.

        See https://cloud.google.com/storage/docs/lifecycle and
             https://cloud.google.com/storage/docs/json_api/v1/buckets

        .. note::

           The getter for this property returns a list which contains
           *copies* of the bucket's lifecycle rules mappings.  Mutating the
           list or one of its dicts has no effect unless you then re-assign
           the dict via the setter.  E.g.:

           >>> rules = bucket.lifecycle_rules
           >>> rules.append({'origin': '/foo', ...})
           >>> rules[1]['rule']['action']['type'] = 'Delete'
           >>> del rules[0]
           >>> bucket.lifecycle_rules = rules
           >>> bucket.update()

        :setter: Set lifestyle rules for this bucket.
        :getter: Gets the lifestyle rules for this bucket.

        :rtype: generator(dict)
        :returns: A sequence of mappings describing each lifecycle rule.
        """
        info = self._properties.get("lifecycle", {})
        for rule in info.get("rule", ()):
            action_type = rule["action"]["type"]
            if action_type == "Delete":
                yield LifecycleRuleDelete.from_api_repr(rule)
            elif action_type == "SetStorageClass":
                yield LifecycleRuleSetStorageClass.from_api_repr(rule)
            else:
                raise ValueError("Unknown lifecycle rule: {}".format(rule))

    @lifecycle_rules.setter
    def lifecycle_rules(self, rules):
        """Set lifestyle rules configured for this bucket.

        See https://cloud.google.com/storage/docs/lifecycle and
             https://cloud.google.com/storage/docs/json_api/v1/buckets

        :type rules: list of dictionaries
        :param rules: A sequence of mappings describing each lifecycle rule.
        """
        rules = [dict(rule) for rule in rules]  # Convert helpers if needed
        self._patch_property("lifecycle", {"rule": rules})

    def clear_lifecyle_rules(self):
        """Set lifestyle rules configured for this bucket.

        See https://cloud.google.com/storage/docs/lifecycle and
             https://cloud.google.com/storage/docs/json_api/v1/buckets
        """
        self.lifecycle_rules = []

    def add_lifecycle_delete_rule(self, **kw):
        """Add a "delete" rule to lifestyle rules configured for this bucket.

        See https://cloud.google.com/storage/docs/lifecycle and
             https://cloud.google.com/storage/docs/json_api/v1/buckets

        .. literalinclude:: snippets.py
          :start-after: [START add_lifecycle_delete_rule]
          :end-before: [END add_lifecycle_delete_rule]
          :dedent: 4

        :type kw: dict
        :params kw: arguments passed to :class:`LifecycleRuleConditions`.
        """
        rules = list(self.lifecycle_rules)
        rules.append(LifecycleRuleDelete(**kw))
        self.lifecycle_rules = rules

    def add_lifecycle_set_storage_class_rule(self, storage_class, **kw):
        """Add a "delete" rule to lifestyle rules configured for this bucket.

        See https://cloud.google.com/storage/docs/lifecycle and
             https://cloud.google.com/storage/docs/json_api/v1/buckets

        .. literalinclude:: snippets.py
          :start-after: [START add_lifecycle_set_storage_class_rule]
          :end-before: [END add_lifecycle_set_storage_class_rule]
          :dedent: 4

        :type storage_class: str, one of :attr:`STORAGE_CLASSES`.
        :param storage_class: new storage class to assign to matching items.

        :type kw: dict
        :params kw: arguments passed to :class:`LifecycleRuleConditions`.
        """
        rules = list(self.lifecycle_rules)
        rules.append(LifecycleRuleSetStorageClass(storage_class, **kw))
        self.lifecycle_rules = rules

    _location = _scalar_property("location")

    @property
    def location(self):
        """Retrieve location configured for this bucket.

        See https://cloud.google.com/storage/docs/json_api/v1/buckets and
        https://cloud.google.com/storage/docs/bucket-locations

        Returns ``None`` if the property has not been set before creation,
        or if the bucket's resource has not been loaded from the server.
        :rtype: str or ``NoneType``
        """
        return self._location

    @location.setter
    def location(self, value):
        """(Deprecated) Set `Bucket.location`

        This can only be set at bucket **creation** time.

        See https://cloud.google.com/storage/docs/json_api/v1/buckets and
        https://cloud.google.com/storage/docs/bucket-locations

        .. warning::

            Assignment to 'Bucket.location' is deprecated, as it is only
            valid before the bucket is created. Instead, pass the location
            to `Bucket.create`.
        """
        warnings.warn(_LOCATION_SETTER_MESSAGE, DeprecationWarning, stacklevel=2)
        self._location = value

    @property
    def location_type(self):
        """Retrieve or set the location type for the bucket.

        See https://cloud.google.com/storage/docs/storage-classes

        :setter: Set the location type for this bucket.
        :getter: Gets the the location type for this bucket.

        :rtype: str or ``NoneType``
        :returns:
            If set, one of
            :attr:`~google.cloud.storage.constants.MULTI_REGION_LOCATION_TYPE`,
            :attr:`~google.cloud.storage.constants.REGION_LOCATION_TYPE`, or
            :attr:`~google.cloud.storage.constants.DUAL_REGION_LOCATION_TYPE`,
            else ``None``.
        """
        return self._properties.get("locationType")

    def get_logging(self):
        """Return info about access logging for this bucket.

        See https://cloud.google.com/storage/docs/access-logs#status

        :rtype: dict or None
        :returns: a dict w/ keys, ``logBucket`` and ``logObjectPrefix``
                  (if logging is enabled), or None (if not).
        """
        info = self._properties.get("logging")
        return copy.deepcopy(info)

    def enable_logging(self, bucket_name, object_prefix=""):
        """Enable access logging for this bucket.

        See https://cloud.google.com/storage/docs/access-logs

        :type bucket_name: str
        :param bucket_name: name of bucket in which to store access logs

        :type object_prefix: str
        :param object_prefix: prefix for access log filenames
        """
        info = {"logBucket": bucket_name, "logObjectPrefix": object_prefix}
        self._patch_property("logging", info)

    def disable_logging(self):
        """Disable access logging for this bucket.

        See https://cloud.google.com/storage/docs/access-logs#disabling
        """
        self._patch_property("logging", None)

    @property
    def metageneration(self):
        """Retrieve the metageneration for the bucket.

        See https://cloud.google.com/storage/docs/json_api/v1/buckets

        :rtype: int or ``NoneType``
        :returns: The metageneration of the bucket or ``None`` if the bucket's
                  resource has not been loaded from the server.
        """
        metageneration = self._properties.get("metageneration")
        if metageneration is not None:
            return int(metageneration)

    @property
    def owner(self):
        """Retrieve info about the owner of the bucket.

        See https://cloud.google.com/storage/docs/json_api/v1/buckets

        :rtype: dict or ``NoneType``
        :returns: Mapping of owner's role/ID. Returns ``None`` if the bucket's
                  resource has not been loaded from the server.
        """
        return copy.deepcopy(self._properties.get("owner"))

    @property
    def project_number(self):
        """Retrieve the number of the project to which the bucket is assigned.

        See https://cloud.google.com/storage/docs/json_api/v1/buckets

        :rtype: int or ``NoneType``
        :returns: The project number that owns the bucket or ``None`` if
                  the bucket's resource has not been loaded from the server.
        """
        project_number = self._properties.get("projectNumber")
        if project_number is not None:
            return int(project_number)

    @property
    def retention_policy_effective_time(self):
        """Retrieve the effective time of the bucket's retention policy.

        :rtype: datetime.datetime or ``NoneType``
        :returns: point-in time at which the bucket's retention policy is
                  effective, or ``None`` if the property is not
                  set locally.
        """
        policy = self._properties.get("retentionPolicy")
        if policy is not None:
            timestamp = policy.get("effectiveTime")
            if timestamp is not None:
                return _rfc3339_nanos_to_datetime(timestamp)

    @property
    def retention_policy_locked(self):
        """Retrieve whthere the bucket's retention policy is locked.

        :rtype: bool
        :returns: True if the bucket's policy is locked, or else False
                  if the policy is not locked, or the property is not
                  set locally.
        """
        policy = self._properties.get("retentionPolicy")
        if policy is not None:
            return policy.get("isLocked")

    @property
    def retention_period(self):
        """Retrieve or set the retention period for items in the bucket.

        :rtype: int or ``NoneType``
        :returns: number of seconds to retain items after upload or release
                  from event-based lock, or ``None`` if the property is not
                  set locally.
        """
        policy = self._properties.get("retentionPolicy")
        if policy is not None:
            period = policy.get("retentionPeriod")
            if period is not None:
                return int(period)

    @retention_period.setter
    def retention_period(self, value):
        """Set the retention period for items in the bucket.

        :type value: int
        :param value:
            number of seconds to retain items after upload or release from
            event-based lock.

        :raises ValueError: if the bucket's retention policy is locked.
        """
        policy = self._properties.setdefault("retentionPolicy", {})
        if value is not None:
            policy["retentionPeriod"] = str(value)
        else:
            policy = None
        self._patch_property("retentionPolicy", policy)

    @property
    def self_link(self):
        """Retrieve the URI for the bucket.

        See https://cloud.google.com/storage/docs/json_api/v1/buckets

        :rtype: str or ``NoneType``
        :returns: The self link for the bucket or ``None`` if
                  the bucket's resource has not been loaded from the server.
        """
        return self._properties.get("selfLink")

    @property
    def storage_class(self):
        """Retrieve or set the storage class for the bucket.

        See https://cloud.google.com/storage/docs/storage-classes

        :setter: Set the storage class for this bucket.
        :getter: Gets the the storage class for this bucket.

        :rtype: str or ``NoneType``
        :returns:
            If set, one of
            :attr:`~google.cloud.storage.constants.NEARLINE_STORAGE_CLASS`,
            :attr:`~google.cloud.storage.constants.COLDLINE_STORAGE_CLASS`,
            :attr:`~google.cloud.storage.constants.ARCHIVE_STORAGE_CLASS`,
            :attr:`~google.cloud.storage.constants.STANDARD_STORAGE_CLASS`,
            :attr:`~google.cloud.storage.constants.MULTI_REGIONAL_LEGACY_STORAGE_CLASS`,
            :attr:`~google.cloud.storage.constants.REGIONAL_LEGACY_STORAGE_CLASS`,
            or
            :attr:`~google.cloud.storage.constants.DURABLE_REDUCED_AVAILABILITY_LEGACY_STORAGE_CLASS`,
            else ``None``.
        """
        return self._properties.get("storageClass")

    @storage_class.setter
    def storage_class(self, value):
        """Set the storage class for the bucket.

        See https://cloud.google.com/storage/docs/storage-classes

        :type value: str
        :param value:
            One of
            :attr:`~google.cloud.storage.constants.NEARLINE_STORAGE_CLASS`,
            :attr:`~google.cloud.storage.constants.COLDLINE_STORAGE_CLASS`,
            :attr:`~google.cloud.storage.constants.ARCHIVE_STORAGE_CLASS`,
            :attr:`~google.cloud.storage.constants.STANDARD_STORAGE_CLASS`,
            :attr:`~google.cloud.storage.constants.MULTI_REGIONAL_LEGACY_STORAGE_CLASS`,
            :attr:`~google.cloud.storage.constants.REGIONAL_LEGACY_STORAGE_CLASS`,
            or
            :attr:`~google.cloud.storage.constants.DURABLE_REDUCED_AVAILABILITY_LEGACY_STORAGE_CLASS`,
        """
        if value not in self.STORAGE_CLASSES:
            raise ValueError("Invalid storage class: %s" % (value,))
        self._patch_property("storageClass", value)

    @property
    def time_created(self):
        """Retrieve the timestamp at which the bucket was created.

        See https://cloud.google.com/storage/docs/json_api/v1/buckets

        :rtype: :class:`datetime.datetime` or ``NoneType``
        :returns: Datetime object parsed from RFC3339 valid timestamp, or
                  ``None`` if the bucket's resource has not been loaded
                  from the server.
        """
        value = self._properties.get("timeCreated")
        if value is not None:
            return _rfc3339_nanos_to_datetime(value)

    @property
    def versioning_enabled(self):
        """Is versioning enabled for this bucket?

        See  https://cloud.google.com/storage/docs/object-versioning for
        details.

        :setter: Update whether versioning is enabled for this bucket.
        :getter: Query whether versioning is enabled for this bucket.

        :rtype: bool
        :returns: True if enabled, else False.
        """
        versioning = self._properties.get("versioning", {})
        return versioning.get("enabled", False)

    @versioning_enabled.setter
    def versioning_enabled(self, value):
        """Enable versioning for this bucket.

        See  https://cloud.google.com/storage/docs/object-versioning for
        details.

        :type value: convertible to boolean
        :param value: should versioning be enabled for the bucket?
        """
        self._patch_property("versioning", {"enabled": bool(value)})

    @property
    def requester_pays(self):
        """Does the requester pay for API requests for this bucket?

        See https://cloud.google.com/storage/docs/requester-pays for
        details.

        :setter: Update whether requester pays for this bucket.
        :getter: Query whether requester pays for this bucket.

        :rtype: bool
        :returns: True if requester pays for API requests for the bucket,
                  else False.
        """
        versioning = self._properties.get("billing", {})
        return versioning.get("requesterPays", False)

    @requester_pays.setter
    def requester_pays(self, value):
        """Update whether requester pays for API requests for this bucket.

        See https://cloud.google.com/storage/docs/using-requester-pays for
        details.

        :type value: convertible to boolean
        :param value: should requester pay for API requests for the bucket?
        """
        self._patch_property("billing", {"requesterPays": bool(value)})

    def configure_website(self, main_page_suffix=None, not_found_page=None):
        """Configure website-related properties.

        See https://cloud.google.com/storage/docs/hosting-static-website

        .. note::
          This (apparently) only works
          if your bucket name is a domain name
          (and to do that, you need to get approved somehow...).

        If you want this bucket to host a website, just provide the name
        of an index page and a page to use when a blob isn't found:

        .. literalinclude:: snippets.py
          :start-after: [START configure_website]
          :end-before: [END configure_website]
          :dedent: 4

        You probably should also make the whole bucket public:

        .. literalinclude:: snippets.py
            :start-after: [START make_public]
            :end-before: [END make_public]
            :dedent: 4

        This says: "Make the bucket public, and all the stuff already in
        the bucket, and anything else I add to the bucket.  Just make it
        all public."

        :type main_page_suffix: str
        :param main_page_suffix: The page to use as the main page
                                 of a directory.
                                 Typically something like index.html.

        :type not_found_page: str
        :param not_found_page: The file to use when a page isn't found.
        """
        data = {"mainPageSuffix": main_page_suffix, "notFoundPage": not_found_page}
        self._patch_property("website", data)

    def disable_website(self):
        """Disable the website configuration for this bucket.

        This is really just a shortcut for setting the website-related
        attributes to ``None``.
        """
        return self.configure_website(None, None)

    def get_iam_policy(
        self,
        client=None,
        requested_policy_version=None,
        timeout=_DEFAULT_TIMEOUT,
        retry=DEFAULT_RETRY,
    ):
        """Retrieve the IAM policy for the bucket.

        See
        https://cloud.google.com/storage/docs/json_api/v1/buckets/getIamPolicy

        If :attr:`user_project` is set, bills the API request to that project.

        :type client: :class:`~google.cloud.storage.client.Client` or
                      ``NoneType``
        :param client: (Optional) The client to use.  If not passed, falls back
                       to the ``client`` stored on the current bucket.

        :type requested_policy_version: int or ``NoneType``
        :param requested_policy_version: (Optional) The version of IAM policies to request.
                                         If a policy with a condition is requested without
                                         setting this, the server will return an error.
                                         This must be set to a value of 3 to retrieve IAM
                                         policies containing conditions. This is to prevent
                                         client code that isn't aware of IAM conditions from
                                         interpreting and modifying policies incorrectly.
                                         The service might return a policy with version lower
                                         than the one that was requested, based on the
                                         feature syntax in the policy fetched.

        :type timeout: float or tuple
        :param timeout: (Optional) The amount of time, in seconds, to wait
            for the server response.

            Can also be passed as a tuple (connect_timeout, read_timeout).
            See :meth:`requests.Session.request` documentation for details.

        :type retry: google.api_core.retry.Retry or google.cloud.storage.retry.ConditionalRetryPolicy
        :param retry: (Optional) How to retry the RPC. A None value will disable retries.
            A google.api_core.retry.Retry value will enable retries, and the object will
            define retriable response codes and errors and configure backoff and timeout options.

            A google.cloud.storage.retry.ConditionalRetryPolicy value wraps a Retry object and
            activates it only if certain conditions are met. This class exists to provide safe defaults
            for RPC calls that are not technically safe to retry normally (due to potential data
            duplication or other side-effects) but become safe to retry if a condition such as
            if_metageneration_match is set.

            See the retry.py source code and docstrings in this package (google.cloud.storage.retry) for
            information on retry types and how to configure them.

        :rtype: :class:`google.api_core.iam.Policy`
        :returns: the policy instance, based on the resource returned from
                  the ``getIamPolicy`` API request.

        Example:

        .. code-block:: python

           from google.cloud.storage.iam import STORAGE_OBJECT_VIEWER_ROLE

           policy = bucket.get_iam_policy(requested_policy_version=3)

           policy.version = 3

           # Add a binding to the policy via it's bindings property
           policy.bindings.append({
               "role": STORAGE_OBJECT_VIEWER_ROLE,
               "members": {"serviceAccount:account@project.iam.gserviceaccount.com", ...},
               # Optional:
               "condition": {
                   "title": "prefix"
                   "description": "Objects matching prefix"
                   "expression": "resource.name.startsWith(\"projects/project-name/buckets/bucket-name/objects/prefix\")"
               }
           })

           bucket.set_iam_policy(policy)
        """
        client = self._require_client(client)
        query_params = {}

        if self.user_project is not None:
            query_params["userProject"] = self.user_project

        if requested_policy_version is not None:
            query_params["optionsRequestedPolicyVersion"] = requested_policy_version

        info = client._connection.api_request(
            method="GET",
            path="%s/iam" % (self.path,),
            query_params=query_params,
            _target_object=None,
            timeout=timeout,
            retry=retry,
        )
        return Policy.from_api_repr(info)

    def set_iam_policy(
        self,
        policy,
        client=None,
        timeout=_DEFAULT_TIMEOUT,
        retry=DEFAULT_RETRY_IF_ETAG_IN_JSON,
    ):
        """Update the IAM policy for the bucket.

        See
        https://cloud.google.com/storage/docs/json_api/v1/buckets/setIamPolicy

        If :attr:`user_project` is set, bills the API request to that project.

        :type policy: :class:`google.api_core.iam.Policy`
        :param policy: policy instance used to update bucket's IAM policy.

        :type client: :class:`~google.cloud.storage.client.Client` or
                      ``NoneType``
        :param client: (Optional) The client to use.  If not passed, falls back
                       to the ``client`` stored on the current bucket.

        :type timeout: float or tuple
        :param timeout: (Optional) The amount of time, in seconds, to wait
            for the server response.

            Can also be passed as a tuple (connect_timeout, read_timeout).
            See :meth:`requests.Session.request` documentation for details.

        :type retry: google.api_core.retry.Retry or google.cloud.storage.retry.ConditionalRetryPolicy
        :param retry: (Optional) How to retry the RPC. A None value will disable retries.
            A google.api_core.retry.Retry value will enable retries, and the object will
            define retriable response codes and errors and configure backoff and timeout options.

            A google.cloud.storage.retry.ConditionalRetryPolicy value wraps a Retry object and
            activates it only if certain conditions are met. This class exists to provide safe defaults
            for RPC calls that are not technically safe to retry normally (due to potential data
            duplication or other side-effects) but become safe to retry if a condition such as
            if_metageneration_match is set.

            See the retry.py source code and docstrings in this package (google.cloud.storage.retry) for
            information on retry types and how to configure them.

        :rtype: :class:`google.api_core.iam.Policy`
        :returns: the policy instance, based on the resource returned from
                  the ``setIamPolicy`` API request.
        """
        client = self._require_client(client)
        query_params = {}

        if self.user_project is not None:
            query_params["userProject"] = self.user_project

        resource = policy.to_api_repr()
        resource["resourceId"] = self.path
        info = client._connection.api_request(
            method="PUT",
            path="%s/iam" % (self.path,),
            query_params=query_params,
            data=resource,
            _target_object=None,
            timeout=timeout,
            retry=retry,
        )
        return Policy.from_api_repr(info)

    def test_iam_permissions(
        self, permissions, client=None, timeout=_DEFAULT_TIMEOUT, retry=DEFAULT_RETRY
    ):
        """API call:  test permissions

        See
        https://cloud.google.com/storage/docs/json_api/v1/buckets/testIamPermissions

        If :attr:`user_project` is set, bills the API request to that project.

        :type permissions: list of string
        :param permissions: the permissions to check

        :type client: :class:`~google.cloud.storage.client.Client` or
                      ``NoneType``
        :param client: (Optional) The client to use.  If not passed, falls back
                       to the ``client`` stored on the current bucket.

        :type timeout: float or tuple
        :param timeout: (Optional) The amount of time, in seconds, to wait
            for the server response.

            Can also be passed as a tuple (connect_timeout, read_timeout).
            See :meth:`requests.Session.request` documentation for details.

        :type retry: google.api_core.retry.Retry or google.cloud.storage.retry.ConditionalRetryPolicy
        :param retry: (Optional) How to retry the RPC. A None value will disable retries.
            A google.api_core.retry.Retry value will enable retries, and the object will
            define retriable response codes and errors and configure backoff and timeout options.

            A google.cloud.storage.retry.ConditionalRetryPolicy value wraps a Retry object and
            activates it only if certain conditions are met. This class exists to provide safe defaults
            for RPC calls that are not technically safe to retry normally (due to potential data
            duplication or other side-effects) but become safe to retry if a condition such as
            if_metageneration_match is set.

            See the retry.py source code and docstrings in this package (google.cloud.storage.retry) for
            information on retry types and how to configure them.

        :rtype: list of string
        :returns: the permissions returned by the ``testIamPermissions`` API
                  request.
        """
        client = self._require_client(client)
        query_params = {"permissions": permissions}

        if self.user_project is not None:
            query_params["userProject"] = self.user_project

        path = "%s/iam/testPermissions" % (self.path,)
        resp = client._connection.api_request(
            method="GET",
            path=path,
            query_params=query_params,
            timeout=timeout,
            retry=retry,
        )
        return resp.get("permissions", [])

    def make_public(
        self,
        recursive=False,
        future=False,
        client=None,
        timeout=_DEFAULT_TIMEOUT,
        retry=DEFAULT_RETRY,
    ):
        """Update bucket's ACL, granting read access to anonymous users.

        :type recursive: bool
        :param recursive: If True, this will make all blobs inside the bucket
                          public as well.

        :type future: bool
        :param future: If True, this will make all objects created in the
                       future public as well.

        :type client: :class:`~google.cloud.storage.client.Client` or
                      ``NoneType``
        :param client: (Optional) The client to use.  If not passed, falls back
                       to the ``client`` stored on the current bucket.
        :type timeout: float or tuple
        :param timeout: (Optional) The amount of time, in seconds, to wait
            for the server response. The timeout applies to each underlying
            request.

            Can also be passed as a tuple (connect_timeout, read_timeout).
            See :meth:`requests.Session.request` documentation for details.

        :type retry: google.api_core.retry.Retry or google.cloud.storage.retry.ConditionalRetryPolicy
        :param retry: (Optional) How to retry the RPC. A None value will disable retries.
            A google.api_core.retry.Retry value will enable retries, and the object will
            define retriable response codes and errors and configure backoff and timeout options.

            A google.cloud.storage.retry.ConditionalRetryPolicy value wraps a Retry object and
            activates it only if certain conditions are met. This class exists to provide safe defaults
            for RPC calls that are not technically safe to retry normally (due to potential data
            duplication or other side-effects) but become safe to retry if a condition such as
            if_metageneration_match is set.

            See the retry.py source code and docstrings in this package (google.cloud.storage.retry) for
            information on retry types and how to configure them.

        :raises ValueError:
            If ``recursive`` is True, and the bucket contains more than 256
            blobs.  This is to prevent extremely long runtime of this
            method.  For such buckets, iterate over the blobs returned by
            :meth:`list_blobs` and call
            :meth:`~google.cloud.storage.blob.Blob.make_public`
            for each blob.
        """
        self.acl.all().grant_read()
        self.acl.save(client=client, timeout=timeout)

        if future:
            doa = self.default_object_acl
            if not doa.loaded:
                doa.reload(client=client, timeout=timeout)
            doa.all().grant_read()
            doa.save(client=client, timeout=timeout)

        if recursive:
            blobs = list(
                self.list_blobs(
                    projection="full",
                    max_results=self._MAX_OBJECTS_FOR_ITERATION + 1,
                    client=client,
                    timeout=timeout,
                    retry=retry,
                )
            )
            if len(blobs) > self._MAX_OBJECTS_FOR_ITERATION:
                message = (
                    "Refusing to make public recursively with more than "
                    "%d objects. If you actually want to make every object "
                    "in this bucket public, iterate through the blobs "
                    "returned by 'Bucket.list_blobs()' and call "
                    "'make_public' on each one."
                ) % (self._MAX_OBJECTS_FOR_ITERATION,)
                raise ValueError(message)

            for blob in blobs:
                blob.acl.all().grant_read()
                blob.acl.save(client=client, timeout=timeout)

    def make_private(
        self,
        recursive=False,
        future=False,
        client=None,
        timeout=_DEFAULT_TIMEOUT,
        retry=DEFAULT_RETRY,
    ):
        """Update bucket's ACL, revoking read access for anonymous users.

        :type recursive: bool
        :param recursive: If True, this will make all blobs inside the bucket
                          private as well.

        :type future: bool
        :param future: If True, this will make all objects created in the
                       future private as well.

        :type client: :class:`~google.cloud.storage.client.Client` or
                      ``NoneType``
        :param client: (Optional) The client to use.  If not passed, falls back
                       to the ``client`` stored on the current bucket.

        :type timeout: float or tuple
        :param timeout: (Optional) The amount of time, in seconds, to wait
            for the server response. The timeout applies to each underlying
            request.

            Can also be passed as a tuple (connect_timeout, read_timeout).
            See :meth:`requests.Session.request` documentation for details.

        :type retry: google.api_core.retry.Retry or google.cloud.storage.retry.ConditionalRetryPolicy
        :param retry: (Optional) How to retry the RPC. A None value will disable retries.
            A google.api_core.retry.Retry value will enable retries, and the object will
            define retriable response codes and errors and configure backoff and timeout options.

            A google.cloud.storage.retry.ConditionalRetryPolicy value wraps a Retry object and
            activates it only if certain conditions are met. This class exists to provide safe defaults
            for RPC calls that are not technically safe to retry normally (due to potential data
            duplication or other side-effects) but become safe to retry if a condition such as
            if_metageneration_match is set.

            See the retry.py source code and docstrings in this package (google.cloud.storage.retry) for
            information on retry types and how to configure them.

        :raises ValueError:
            If ``recursive`` is True, and the bucket contains more than 256
            blobs.  This is to prevent extremely long runtime of this
            method.  For such buckets, iterate over the blobs returned by
            :meth:`list_blobs` and call
            :meth:`~google.cloud.storage.blob.Blob.make_private`
            for each blob.
        """
        self.acl.all().revoke_read()
        self.acl.save(client=client, timeout=timeout)

        if future:
            doa = self.default_object_acl
            if not doa.loaded:
                doa.reload(client=client, timeout=timeout)
            doa.all().revoke_read()
            doa.save(client=client, timeout=timeout)

        if recursive:
            blobs = list(
                self.list_blobs(
                    projection="full",
                    max_results=self._MAX_OBJECTS_FOR_ITERATION + 1,
                    client=client,
                    timeout=timeout,
                    retry=retry,
                )
            )
            if len(blobs) > self._MAX_OBJECTS_FOR_ITERATION:
                message = (
                    "Refusing to make private recursively with more than "
                    "%d objects. If you actually want to make every object "
                    "in this bucket private, iterate through the blobs "
                    "returned by 'Bucket.list_blobs()' and call "
                    "'make_private' on each one."
                ) % (self._MAX_OBJECTS_FOR_ITERATION,)
                raise ValueError(message)

            for blob in blobs:
                blob.acl.all().revoke_read()
                blob.acl.save(client=client, timeout=timeout)

    def generate_upload_policy(self, conditions, expiration=None, client=None):
        """Create a signed upload policy for uploading objects.

        This method generates and signs a policy document. You can use
        `policy documents`_ to allow visitors to a website to upload files to
        Google Cloud Storage without giving them direct write access.

        For example:

        .. literalinclude:: snippets.py
            :start-after: [START policy_document]
            :end-before: [END policy_document]
            :dedent: 4

        .. _policy documents:
            https://cloud.google.com/storage/docs/xml-api\
            /post-object#policydocument

        :type expiration: datetime
        :param expiration: (Optional) Expiration in UTC. If not specified, the
                           policy will expire in 1 hour.

        :type conditions: list
        :param conditions: A list of conditions as described in the
                          `policy documents`_ documentation.

        :type client: :class:`~google.cloud.storage.client.Client`
        :param client: (Optional) The client to use.  If not passed, falls back
                       to the ``client`` stored on the current bucket.

        :rtype: dict
        :returns: A dictionary of (form field name, form field value) of form
                  fields that should be added to your HTML upload form in order
                  to attach the signature.
        """
        client = self._require_client(client)
        credentials = client._base_connection.credentials
        _signing.ensure_signed_credentials(credentials)

        if expiration is None:
            expiration = _NOW() + datetime.timedelta(hours=1)

        conditions = conditions + [{"bucket": self.name}]

        policy_document = {
            "expiration": _datetime_to_rfc3339(expiration),
            "conditions": conditions,
        }

        encoded_policy_document = base64.b64encode(
            json.dumps(policy_document).encode("utf-8")
        )
        signature = base64.b64encode(credentials.sign_bytes(encoded_policy_document))

        fields = {
            "bucket": self.name,
            "GoogleAccessId": credentials.signer_email,
            "policy": encoded_policy_document.decode("utf-8"),
            "signature": signature.decode("utf-8"),
        }

        return fields

    def lock_retention_policy(
        self, client=None, timeout=_DEFAULT_TIMEOUT, retry=DEFAULT_RETRY
    ):
        """Lock the bucket's retention policy.

        :type client: :class:`~google.cloud.storage.client.Client` or
                      ``NoneType``
        :param client: (Optional) The client to use.  If not passed, falls back
                       to the ``client`` stored on the blob's bucket.

        :type timeout: float or tuple
        :param timeout: (Optional) The amount of time, in seconds, to wait
            for the server response.

            Can also be passed as a tuple (connect_timeout, read_timeout).
            See :meth:`requests.Session.request` documentation for details.

        :type retry: google.api_core.retry.Retry or google.cloud.storage.retry.ConditionalRetryPolicy
        :param retry: (Optional) How to retry the RPC. A None value will disable retries.
            A google.api_core.retry.Retry value will enable retries, and the object will
            define retriable response codes and errors and configure backoff and timeout options.

            A google.cloud.storage.retry.ConditionalRetryPolicy value wraps a Retry object and
            activates it only if certain conditions are met. This class exists to provide safe defaults
            for RPC calls that are not technically safe to retry normally (due to potential data
            duplication or other side-effects) but become safe to retry if a condition such as
            if_metageneration_match is set.

            See the retry.py source code and docstrings in this package (google.cloud.storage.retry) for
            information on retry types and how to configure them.

        :raises ValueError:
            if the bucket has no metageneration (i.e., new or never reloaded);
            if the bucket has no retention policy assigned;
            if the bucket's retention policy is already locked.
        """
        if "metageneration" not in self._properties:
            raise ValueError("Bucket has no retention policy assigned: try 'reload'?")

        policy = self._properties.get("retentionPolicy")

        if policy is None:
            raise ValueError("Bucket has no retention policy assigned: try 'reload'?")

        if policy.get("isLocked"):
            raise ValueError("Bucket's retention policy is already locked.")

        client = self._require_client(client)

        query_params = {"ifMetagenerationMatch": self.metageneration}

        if self.user_project is not None:
            query_params["userProject"] = self.user_project

        path = "/b/{}/lockRetentionPolicy".format(self.name)
        api_response = client._connection.api_request(
            method="POST",
            path=path,
            query_params=query_params,
            _target_object=self,
            timeout=timeout,
            retry=retry,
        )
        self._set_properties(api_response)

    def generate_signed_url(
        self,
        expiration=None,
        api_access_endpoint=_API_ACCESS_ENDPOINT,
        method="GET",
        headers=None,
        query_parameters=None,
        client=None,
        credentials=None,
        version=None,
        virtual_hosted_style=False,
        bucket_bound_hostname=None,
        scheme="http",
    ):
        """Generates a signed URL for this bucket.

        .. note::

            If you are on Google Compute Engine, you can't generate a signed
            URL using GCE service account. Follow `Issue 50`_ for updates on
            this. If you'd like to be able to generate a signed URL from GCE,
            you can use a standard service account from a JSON file rather
            than a GCE service account.

        .. _Issue 50: https://github.com/GoogleCloudPlatform/\
                      google-auth-library-python/issues/50

        If you have a bucket that you want to allow access to for a set
        amount of time, you can use this method to generate a URL that
        is only valid within a certain time period.

        If ``bucket_bound_hostname`` is set as an argument of :attr:`api_access_endpoint`,
        ``https`` works only if using a ``CDN``.

        Example:
            Generates a signed URL for this bucket using bucket_bound_hostname and scheme.

            >>> from google.cloud import storage
            >>> client = storage.Client()
            >>> bucket = client.get_bucket('my-bucket-name')
            >>> url = bucket.generate_signed_url(expiration='url-expiration-time', bucket_bound_hostname='mydomain.tld',
            >>>                                  version='v4')
            >>> url = bucket.generate_signed_url(expiration='url-expiration-time', bucket_bound_hostname='mydomain.tld',
            >>>                                  version='v4',scheme='https')  # If using ``CDN``

        This is particularly useful if you don't want publicly
        accessible buckets, but don't want to require users to explicitly
        log in.

        :type expiration: Union[Integer, datetime.datetime, datetime.timedelta]
        :param expiration: Point in time when the signed URL should expire. If
                           a ``datetime`` instance is passed without an explicit
                           ``tzinfo`` set,  it will be assumed to be ``UTC``.

        :type api_access_endpoint: str
        :param api_access_endpoint: (Optional) URI base.

        :type method: str
        :param method: The HTTP verb that will be used when requesting the URL.

        :type headers: dict
        :param headers:
            (Optional) Additional HTTP headers to be included as part of the
            signed URLs.  See:
            https://cloud.google.com/storage/docs/xml-api/reference-headers
            Requests using the signed URL *must* pass the specified header
            (name and value) with each request for the URL.

        :type query_parameters: dict
        :param query_parameters:
            (Optional) Additional query parameters to be included as part of the
            signed URLs.  See:
            https://cloud.google.com/storage/docs/xml-api/reference-headers#query

        :type client: :class:`~google.cloud.storage.client.Client` or
                      ``NoneType``
        :param client: (Optional) The client to use.  If not passed, falls back
                       to the ``client`` stored on the blob's bucket.


        :type credentials: :class:`google.auth.credentials.Credentials` or
                           :class:`NoneType`
        :param credentials: The authorization credentials to attach to requests.
                            These credentials identify this application to the service.
                            If none are specified, the client will attempt to ascertain
                            the credentials from the environment.

        :type version: str
        :param version: (Optional) The version of signed credential to create.
                        Must be one of 'v2' | 'v4'.

        :type virtual_hosted_style: bool
        :param virtual_hosted_style:
            (Optional) If true, then construct the URL relative the bucket's
            virtual hostname, e.g., '<bucket-name>.storage.googleapis.com'.

        :type bucket_bound_hostname: str
        :param bucket_bound_hostname:
            (Optional) If pass, then construct the URL relative to the bucket-bound hostname.
            Value cane be a bare or with scheme, e.g., 'example.com' or 'http://example.com'.
            See: https://cloud.google.com/storage/docs/request-endpoints#cname

        :type scheme: str
        :param scheme:
            (Optional) If ``bucket_bound_hostname`` is passed as a bare hostname, use
            this value as the scheme.  ``https`` will work only when using a CDN.
            Defaults to ``"http"``.

        :raises: :exc:`ValueError` when version is invalid.
        :raises: :exc:`TypeError` when expiration is not a valid type.
        :raises: :exc:`AttributeError` if credentials is not an instance
                of :class:`google.auth.credentials.Signing`.

        :rtype: str
        :returns: A signed URL you can use to access the resource
                  until expiration.
        """
        if version is None:
            version = "v2"
        elif version not in ("v2", "v4"):
            raise ValueError("'version' must be either 'v2' or 'v4'")

        if virtual_hosted_style:
            api_access_endpoint = "https://{bucket_name}.storage.googleapis.com".format(
                bucket_name=self.name
            )
        elif bucket_bound_hostname:
            api_access_endpoint = _bucket_bound_hostname_url(
                bucket_bound_hostname, scheme
            )
        else:
            resource = "/{bucket_name}".format(bucket_name=self.name)

        if virtual_hosted_style or bucket_bound_hostname:
            resource = "/"

        if credentials is None:
            client = self._require_client(client)
            credentials = client._credentials

        if version == "v2":
            helper = generate_signed_url_v2
        else:
            helper = generate_signed_url_v4

        return helper(
            credentials,
            resource=resource,
            expiration=expiration,
            api_access_endpoint=api_access_endpoint,
            method=method.upper(),
            headers=headers,
            query_parameters=query_parameters,
        )


def _raise_if_len_differs(expected_len, **generation_match_args):
    """
    Raise an error if any generation match argument
    is set and its len differs from the given value.

    :type expected_len: int
    :param expected_len: Expected argument length in case it's set.

    :type generation_match_args: dict
    :param generation_match_args: Lists, which length must be checked.

    :raises: :exc:`ValueError` if any argument set, but has an unexpected length.
    """
    for name, value in generation_match_args.items():
        if value is not None and len(value) != expected_len:
            raise ValueError(
                "'{}' length must be the same as 'blobs' length".format(name)
            )