models.py

"""Route53Backend class with methods for supported APIs."""
import itertools
from collections import defaultdict
import re

import string
import random
import uuid
from jinja2 import Template

from moto.route53.exceptions import (
    HostedZoneNotEmpty,
    InvalidActionValue,
    InvalidCloudWatchArn,
    LastVPCAssociation,
    NoSuchCloudWatchLogsLogGroup,
    NoSuchDelegationSet,
    NoSuchHealthCheck,
    NoSuchHostedZone,
    NoSuchQueryLoggingConfig,
    PublicZoneVPCAssociation,
    QueryLoggingConfigAlreadyExists,
)
from moto.core import BaseBackend, BaseModel, CloudFormationModel, get_account_id
from moto.core.utils import BackendDict
from moto.utilities.paginator import paginate
from .utils import PAGINATION_MODEL

ROUTE53_ID_CHOICE = string.ascii_uppercase + string.digits


def create_route53_zone_id():
    # New ID's look like this Z1RWWTK7Y8UDDQ
    return "".join([random.choice(ROUTE53_ID_CHOICE) for _ in range(0, 15)])


class DelegationSet(BaseModel):
    def __init__(self, caller_reference, name_servers, delegation_set_id):
        self.caller_reference = caller_reference
        self.name_servers = name_servers or [
            "ns-2048.awsdns-64.com",
            "ns-2049.awsdns-65.net",
            "ns-2050.awsdns-66.org",
            "ns-2051.awsdns-67.co.uk",
        ]
        self.id = delegation_set_id or "".join(
            [random.choice(ROUTE53_ID_CHOICE) for _ in range(5)]
        )
        self.location = f"https://route53.amazonaws.com/delegationset/{self.id}"


class HealthCheck(CloudFormationModel):
    def __init__(self, health_check_id, caller_reference, health_check_args):
        self.id = health_check_id
        self.ip_address = health_check_args.get("ip_address")
        self.port = health_check_args.get("port") or 80
        self.type_ = health_check_args.get("type")
        self.resource_path = health_check_args.get("resource_path")
        self.fqdn = health_check_args.get("fqdn")
        self.search_string = health_check_args.get("search_string")
        self.request_interval = health_check_args.get("request_interval") or 30
        self.failure_threshold = health_check_args.get("failure_threshold") or 3
        self.health_threshold = health_check_args.get("health_threshold")
        self.measure_latency = health_check_args.get("measure_latency") or False
        self.inverted = health_check_args.get("inverted") or False
        self.disabled = health_check_args.get("disabled") or False
        self.enable_sni = health_check_args.get("enable_sni") or False
        self.children = health_check_args.get("children") or None
        self.caller_reference = caller_reference

    @property
    def physical_resource_id(self):
        return self.id

    @staticmethod
    def cloudformation_name_type():
        return None

    @staticmethod
    def cloudformation_type():
        # https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/aws-resource-route53-healthcheck.html
        return "AWS::Route53::HealthCheck"

    @classmethod
    def create_from_cloudformation_json(
        cls, resource_name, cloudformation_json, region_name, **kwargs
    ):
        properties = cloudformation_json["Properties"]["HealthCheckConfig"]
        health_check_args = {
            "ip_address": properties.get("IPAddress"),
            "port": properties.get("Port"),
            "type": properties["Type"],
            "resource_path": properties.get("ResourcePath"),
            "fqdn": properties.get("FullyQualifiedDomainName"),
            "search_string": properties.get("SearchString"),
            "request_interval": properties.get("RequestInterval"),
            "failure_threshold": properties.get("FailureThreshold"),
        }
        health_check = route53_backend.create_health_check(
            caller_reference=resource_name, health_check_args=health_check_args
        )
        return health_check

    def to_xml(self):
        template = Template(
            """<HealthCheck>
            <Id>{{ health_check.id }}</Id>
            <CallerReference>{{ health_check.caller_reference }}</CallerReference>
            <HealthCheckConfig>
                {% if health_check.type_ != "CALCULATED" %}
                    <IPAddress>{{ health_check.ip_address }}</IPAddress>
                    <Port>{{ health_check.port }}</Port>
                {% endif %}
                <Type>{{ health_check.type_ }}</Type>
                {% if health_check.resource_path %}
                    <ResourcePath>{{ health_check.resource_path }}</ResourcePath>
                {% endif %}
                {% if health_check.fqdn %}
                    <FullyQualifiedDomainName>{{ health_check.fqdn }}</FullyQualifiedDomainName>
                {% endif %}
                {% if health_check.type_ != "CALCULATED" %}
                    <RequestInterval>{{ health_check.request_interval }}</RequestInterval>
                    <FailureThreshold>{{ health_check.failure_threshold }}</FailureThreshold>
                    <MeasureLatency>{{ health_check.measure_latency }}</MeasureLatency>
                {% endif %}
                {% if health_check.type_ == "CALCULATED" %}
                    <HealthThreshold>{{ health_check.health_threshold }}</HealthThreshold>
                {% endif %}
                <Inverted>{{ health_check.inverted }}</Inverted>
                <Disabled>{{ health_check.disabled }}</Disabled>
                <EnableSNI>{{ health_check.enable_sni }}</EnableSNI>
                {% if health_check.search_string %}
                    <SearchString>{{ health_check.search_string }}</SearchString>
                {% endif %}
                {% if health_check.children %}
                    <ChildHealthChecks>
                    {% for child in health_check.children %}
                        <member>{{ child }}</member>
                    {% endfor %}
                    </ChildHealthChecks>
                {% endif %}
            </HealthCheckConfig>
            <HealthCheckVersion>1</HealthCheckVersion>
        </HealthCheck>"""
        )
        return template.render(health_check=self)


class RecordSet(CloudFormationModel):
    def __init__(self, kwargs):
        self.name = kwargs.get("Name")
        self.type_ = kwargs.get("Type")
        self.ttl = kwargs.get("TTL", 0)
        self.records = kwargs.get("ResourceRecords", [])
        self.set_identifier = kwargs.get("SetIdentifier")
        self.weight = kwargs.get("Weight", 0)
        self.region = kwargs.get("Region")
        self.health_check = kwargs.get("HealthCheckId")
        self.hosted_zone_name = kwargs.get("HostedZoneName")
        self.hosted_zone_id = kwargs.get("HostedZoneId")
        self.alias_target = kwargs.get("AliasTarget", [])
        self.failover = kwargs.get("Failover", [])
        self.geo_location = kwargs.get("GeoLocation", [])

    @staticmethod
    def cloudformation_name_type():
        return "Name"

    @staticmethod
    def cloudformation_type():
        # https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/aws-resource-route53-recordset.html
        return "AWS::Route53::RecordSet"

    @classmethod
    def create_from_cloudformation_json(
        cls, resource_name, cloudformation_json, region_name, **kwargs
    ):
        properties = cloudformation_json["Properties"]

        zone_name = properties.get("HostedZoneName")
        if zone_name:
            hosted_zone = route53_backend.get_hosted_zone_by_name(zone_name)
        else:
            hosted_zone = route53_backend.get_hosted_zone(properties["HostedZoneId"])
        record_set = hosted_zone.add_rrset(properties)
        return record_set

    @classmethod
    def update_from_cloudformation_json(
        cls, original_resource, new_resource_name, cloudformation_json, region_name
    ):
        cls.delete_from_cloudformation_json(
            original_resource.name, cloudformation_json, region_name
        )
        return cls.create_from_cloudformation_json(
            new_resource_name, cloudformation_json, region_name
        )

    @classmethod
    def delete_from_cloudformation_json(
        cls, resource_name, cloudformation_json, region_name
    ):
        # this will break if you changed the zone the record is in,
        # unfortunately
        properties = cloudformation_json["Properties"]

        zone_name = properties.get("HostedZoneName")
        if zone_name:
            hosted_zone = route53_backend.get_hosted_zone_by_name(zone_name)
        else:
            hosted_zone = route53_backend.get_hosted_zone(properties["HostedZoneId"])

        try:
            hosted_zone.delete_rrset({"Name": resource_name})
        except KeyError:
            pass

    @property
    def physical_resource_id(self):
        return self.name

    def delete(self, *args, **kwargs):  # pylint: disable=unused-argument
        """Not exposed as part of the Route 53 API - used for CloudFormation. args are ignored"""
        hosted_zone = route53_backend.get_hosted_zone_by_name(self.hosted_zone_name)
        if not hosted_zone:
            hosted_zone = route53_backend.get_hosted_zone(self.hosted_zone_id)
        hosted_zone.delete_rrset({"Name": self.name, "Type": self.type_})


def reverse_domain_name(domain_name):
    if domain_name.endswith("."):  # normalize without trailing dot
        domain_name = domain_name[:-1]
    return ".".join(reversed(domain_name.split(".")))


class FakeZone(CloudFormationModel):
    def __init__(
        self,
        name,
        id_,
        private_zone,
        comment=None,
        delegation_set=None,
    ):
        self.name = name
        self.id = id_
        self.vpcs = []
        if comment is not None:
            self.comment = comment
        self.private_zone = private_zone
        self.rrsets = []
        self.delegation_set = delegation_set

    def add_rrset(self, record_set):
        record_set = RecordSet(record_set)
        self.rrsets.append(record_set)
        return record_set

    def upsert_rrset(self, record_set):
        new_rrset = RecordSet(record_set)
        for i, rrset in enumerate(self.rrsets):
            if (
                rrset.name == new_rrset.name
                and rrset.type_ == new_rrset.type_
                and rrset.set_identifier == new_rrset.set_identifier
            ):
                self.rrsets[i] = new_rrset
                break
        else:
            self.rrsets.append(new_rrset)
        return new_rrset

    def delete_rrset(self, rrset):
        self.rrsets = [
            record_set
            for record_set in self.rrsets
            if record_set.name != rrset["Name"]
            or (rrset.get("Type") is not None and record_set.type_ != rrset["Type"])
        ]

    def delete_rrset_by_id(self, set_identifier):
        self.rrsets = [
            record_set
            for record_set in self.rrsets
            if record_set.set_identifier != set_identifier
        ]

    def add_vpc(self, vpc_id, vpc_region):
        vpc = {}
        if vpc_id is not None:
            vpc["vpc_id"] = vpc_id
        if vpc_region is not None:
            vpc["vpc_region"] = vpc_region
        if vpc_id or vpc_region:
            self.vpcs.append(vpc)
        return vpc

    def delete_vpc(self, vpc_id):
        self.vpcs = [vpc for vpc in self.vpcs if vpc["vpc_id"] != vpc_id]

    def get_record_sets(self, start_type, start_name):
        def predicate(rrset):
            rrset_name_reversed = reverse_domain_name(rrset.name)
            start_name_reversed = reverse_domain_name(start_name)
            return rrset_name_reversed < start_name_reversed or (
                rrset_name_reversed == start_name_reversed and rrset.type_ < start_type
            )

        record_sets = sorted(
            self.rrsets,
            key=lambda rrset: (reverse_domain_name(rrset.name), rrset.type_),
        )

        if start_name:
            start_type = start_type or ""
            record_sets = itertools.dropwhile(predicate, record_sets)

        return record_sets

    @property
    def physical_resource_id(self):
        return self.id

    @staticmethod
    def cloudformation_name_type():
        return "Name"

    @staticmethod
    def cloudformation_type():
        # https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/aws-resource-route53-hostedzone.html
        return "AWS::Route53::HostedZone"

    @classmethod
    def create_from_cloudformation_json(
        cls, resource_name, cloudformation_json, region_name, **kwargs
    ):
        hosted_zone = route53_backend.create_hosted_zone(
            resource_name, private_zone=False
        )
        return hosted_zone


class RecordSetGroup(CloudFormationModel):
    def __init__(self, hosted_zone_id, record_sets):
        self.hosted_zone_id = hosted_zone_id
        self.record_sets = record_sets

    @property
    def physical_resource_id(self):
        return f"arn:aws:route53:::hostedzone/{self.hosted_zone_id}"

    @staticmethod
    def cloudformation_name_type():
        return None

    @staticmethod
    def cloudformation_type():
        # https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/aws-resource-route53-recordsetgroup.html
        return "AWS::Route53::RecordSetGroup"

    @classmethod
    def create_from_cloudformation_json(
        cls, resource_name, cloudformation_json, region_name, **kwargs
    ):
        properties = cloudformation_json["Properties"]

        zone_name = properties.get("HostedZoneName")
        if zone_name:
            hosted_zone = route53_backend.get_hosted_zone_by_name(zone_name)
        else:
            hosted_zone = route53_backend.get_hosted_zone(properties["HostedZoneId"])
        record_sets = properties["RecordSets"]
        for record_set in record_sets:
            hosted_zone.add_rrset(record_set)

        record_set_group = RecordSetGroup(hosted_zone.id, record_sets)
        return record_set_group


class QueryLoggingConfig(BaseModel):

    """QueryLoggingConfig class; this object isn't part of Cloudformation."""

    def __init__(
        self, query_logging_config_id, hosted_zone_id, cloudwatch_logs_log_group_arn
    ):
        self.hosted_zone_id = hosted_zone_id
        self.cloudwatch_logs_log_group_arn = cloudwatch_logs_log_group_arn
        self.query_logging_config_id = query_logging_config_id
        self.location = f"https://route53.amazonaws.com/2013-04-01/queryloggingconfig/{self.query_logging_config_id}"

    def to_xml(self):
        template = Template(
            """<QueryLoggingConfig>
                <CloudWatchLogsLogGroupArn>{{ query_logging_config.cloudwatch_logs_log_group_arn }}</CloudWatchLogsLogGroupArn>
                <HostedZoneId>{{ query_logging_config.hosted_zone_id }}</HostedZoneId>
                <Id>{{ query_logging_config.query_logging_config_id }}</Id>
            </QueryLoggingConfig>"""
        )
        # The "Location" value must be put into the header; that's done in
        # responses.py.
        return template.render(query_logging_config=self)


class Route53Backend(BaseBackend):
    def __init__(self, region_name, account_id):
        super().__init__(region_name, account_id)
        self.zones = {}
        self.health_checks = {}
        self.resource_tags = defaultdict(dict)
        self.query_logging_configs = {}
        self.delegation_sets = dict()

    def create_hosted_zone(
        self,
        name,
        private_zone,
        vpcid=None,
        vpcregion=None,
        comment=None,
        delegation_set_id=None,
    ):
        new_id = create_route53_zone_id()
        delegation_set = self.create_reusable_delegation_set(
            caller_reference=f"DelSet_{name}", delegation_set_id=delegation_set_id
        )
        # default delegation set does not contains id
        if not delegation_set_id:
            delegation_set.id = ""
        new_zone = FakeZone(
            name,
            new_id,
            private_zone=private_zone,
            comment=comment,
            delegation_set=delegation_set,
        )
        # default nameservers are also part of rrset
        record_set = {
            "Name": name,
            "ResourceRecords": delegation_set.name_servers,
            "TTL": "172800",
            "Type": "NS",
        }
        new_zone.add_rrset(record_set)
        new_zone.add_vpc(vpcid, vpcregion)
        self.zones[new_id] = new_zone
        return new_zone

    def get_dnssec(self, zone_id):
        # check if hosted zone exists
        self.get_hosted_zone(zone_id)

    def associate_vpc(self, zone_id, vpcid, vpcregion):
        zone = self.get_hosted_zone(zone_id)
        if not zone.private_zone:
            raise PublicZoneVPCAssociation()
        zone.add_vpc(vpcid, vpcregion)
        return zone

    def disassociate_vpc(self, zone_id, vpcid):
        zone = self.get_hosted_zone(zone_id)
        if len(zone.vpcs) <= 1:
            raise LastVPCAssociation()
        zone.delete_vpc(vpcid)
        return zone

    def change_tags_for_resource(self, resource_id, tags):
        if "Tag" in tags:
            if isinstance(tags["Tag"], list):
                for tag in tags["Tag"]:
                    self.resource_tags[resource_id][tag["Key"]] = tag["Value"]
            else:
                key, value = (tags["Tag"]["Key"], tags["Tag"]["Value"])
                self.resource_tags[resource_id][key] = value
        else:
            if "Key" in tags:
                if isinstance(tags["Key"], list):
                    for key in tags["Key"]:
                        del self.resource_tags[resource_id][key]
                else:
                    del self.resource_tags[resource_id][tags["Key"]]

    def list_tags_for_resource(self, resource_id):
        if resource_id in self.resource_tags:
            return self.resource_tags[resource_id]
        return {}

    def list_resource_record_sets(self, zone_id, start_type, start_name, max_items):
        """
        The StartRecordIdentifier-parameter is not yet implemented
        """
        the_zone = self.get_hosted_zone(zone_id)
        all_records = list(the_zone.get_record_sets(start_type, start_name))
        records = all_records[0:max_items]
        next_record = all_records[max_items] if len(all_records) > max_items else None
        next_start_name = next_record.name if next_record else None
        next_start_type = next_record.type_ if next_record else None
        is_truncated = next_record is not None
        return records, next_start_name, next_start_type, is_truncated

    def change_resource_record_sets(self, zoneid, change_list):
        the_zone = self.get_hosted_zone(zoneid)
        for value in change_list:
            action = value["Action"]

            if action not in ("CREATE", "UPSERT", "DELETE"):
                raise InvalidActionValue(action)

            record_set = value["ResourceRecordSet"]

            cleaned_record_name = record_set["Name"].strip(".")
            cleaned_hosted_zone_name = the_zone.name.strip(".")

            if not cleaned_record_name.endswith(cleaned_hosted_zone_name):
                error_msg = f"""
                An error occurred (InvalidChangeBatch) when calling the ChangeResourceRecordSets operation:
                RRSet with DNS name {record_set["Name"]} is not permitted in zone {the_zone.name}
                """
                return error_msg

            if not record_set["Name"].endswith("."):
                record_set["Name"] += "."

            if action in ("CREATE", "UPSERT"):
                if "ResourceRecords" in record_set:
                    resource_records = list(record_set["ResourceRecords"].values())[0]
                    if not isinstance(resource_records, list):
                        # Depending on how many records there are, this may
                        # or may not be a list
                        resource_records = [resource_records]
                    record_set["ResourceRecords"] = [
                        x["Value"] for x in resource_records
                    ]
                if action == "CREATE":
                    the_zone.add_rrset(record_set)
                else:
                    the_zone.upsert_rrset(record_set)
            elif action == "DELETE":
                if "SetIdentifier" in record_set:
                    the_zone.delete_rrset_by_id(record_set["SetIdentifier"])
                else:
                    the_zone.delete_rrset(record_set)
        return None

    def list_hosted_zones(self):
        return self.zones.values()

    def list_hosted_zones_by_name(self, dnsname):
        if dnsname:
            dnsname = dnsname[0]
            if dnsname[-1] != ".":
                dnsname += "."
            zones = [zone for zone in self.list_hosted_zones() if zone.name == dnsname]
        else:
            # sort by names, but with domain components reversed
            # see http://boto3.readthedocs.io/en/latest/reference/services/route53.html#Route53.Client.list_hosted_zones_by_name

            def sort_key(zone):
                domains = zone.name.split(".")
                if domains[-1] == "":
                    domains = domains[-1:] + domains[:-1]
                return ".".join(reversed(domains))

            zones = self.list_hosted_zones()
            zones = sorted(zones, key=sort_key)
        return dnsname, zones

    def list_hosted_zones_by_vpc(self, vpc_id):
        """
        Pagination is not yet implemented
        """
        zone_list = []
        for zone in self.list_hosted_zones():
            if zone.private_zone is True:
                this_zone = self.get_hosted_zone(zone.id)
                for vpc in this_zone.vpcs:
                    if vpc["vpc_id"] == vpc_id:
                        zone_list.append(
                            {
                                "HostedZoneId": zone.id,
                                "Name": zone.name,
                                "Owner": {"OwningAccount": get_account_id()},
                            }
                        )

        return zone_list

    def get_hosted_zone(self, id_):
        the_zone = self.zones.get(id_.replace("/hostedzone/", ""))
        if not the_zone:
            raise NoSuchHostedZone(id_)
        return the_zone

    def get_hosted_zone_count(self):
        return len(self.list_hosted_zones())

    def get_hosted_zone_by_name(self, name):
        for zone in self.list_hosted_zones():
            if zone.name == name:
                return zone
        return None

    def delete_hosted_zone(self, id_):
        # Verify it exists
        zone = self.get_hosted_zone(id_)
        if len(zone.rrsets) > 0:
            for rrset in zone.rrsets:
                if rrset.type_ != "NS" and rrset.type_ != "SOA":
                    raise HostedZoneNotEmpty()
        return self.zones.pop(id_.replace("/hostedzone/", ""), None)

    def update_hosted_zone_comment(self, id_, comment):
        zone = self.get_hosted_zone(id_)
        zone.comment = comment
        return zone

    def create_health_check(self, caller_reference, health_check_args):
        health_check_id = str(uuid.uuid4())
        health_check = HealthCheck(health_check_id, caller_reference, health_check_args)
        self.health_checks[health_check_id] = health_check
        return health_check

    def list_health_checks(self):
        return self.health_checks.values()

    def delete_health_check(self, health_check_id):
        return self.health_checks.pop(health_check_id, None)

    def get_health_check(self, health_check_id):
        health_check = self.health_checks.get(health_check_id)
        if not health_check:
            raise NoSuchHealthCheck(health_check_id)
        return health_check

    @staticmethod
    def _validate_arn(region, arn):
        match = re.match(rf"arn:aws:logs:{region}:\d{{12}}:log-group:.+", arn)
        if not arn or not match:
            raise InvalidCloudWatchArn()

        # The CloudWatch Logs log group must be in the "us-east-1" region.
        match = re.match(r"^(?:[^:]+:){3}(?P<region>[^:]+).*", arn)
        if match.group("region") != "us-east-1":
            raise InvalidCloudWatchArn()

    def create_query_logging_config(self, region, hosted_zone_id, log_group_arn):
        """Process the create_query_logging_config request."""
        # Does the hosted_zone_id exist?
        response = self.list_hosted_zones()
        zones = list(response) if response else []
        for zone in zones:
            if zone.id == hosted_zone_id:
                break
        else:
            raise NoSuchHostedZone(hosted_zone_id)

        # Ensure CloudWatch Logs log ARN is valid, otherwise raise an error.
        self._validate_arn(region, log_group_arn)

        # Note:  boto3 checks the resource policy permissions before checking
        # whether the log group exists.  moto doesn't have a way of checking
        # the resource policy, so in some instances moto will complain
        # about a log group that doesn't exist whereas boto3 will complain
        # that "The resource policy that you're using for Route 53 query
        # logging doesn't grant Route 53 sufficient permission to create
        # a log stream in the specified log group."

        from moto.logs import logs_backends  # pylint: disable=import-outside-toplevel

        response = logs_backends[region].describe_log_groups()
        log_groups = response[0] if response else []
        for entry in log_groups:
            if log_group_arn == entry["arn"]:
                break
        else:
            # There is no CloudWatch Logs log group with the specified ARN.
            raise NoSuchCloudWatchLogsLogGroup()

        # Verify there is no existing query log config using the same hosted
        # zone.
        for query_log in self.query_logging_configs.values():
            if query_log.hosted_zone_id == hosted_zone_id:
                raise QueryLoggingConfigAlreadyExists()

        # Create an instance of the query logging config.
        query_logging_config_id = str(uuid.uuid4())
        query_logging_config = QueryLoggingConfig(
            query_logging_config_id, hosted_zone_id, log_group_arn
        )
        self.query_logging_configs[query_logging_config_id] = query_logging_config
        return query_logging_config

    def delete_query_logging_config(self, query_logging_config_id):
        """Delete query logging config, if it exists."""
        if query_logging_config_id not in self.query_logging_configs:
            raise NoSuchQueryLoggingConfig()
        self.query_logging_configs.pop(query_logging_config_id)

    def get_query_logging_config(self, query_logging_config_id):
        """Return query logging config, if it exists."""
        if query_logging_config_id not in self.query_logging_configs:
            raise NoSuchQueryLoggingConfig()
        return self.query_logging_configs[query_logging_config_id]

    @paginate(pagination_model=PAGINATION_MODEL)
    def list_query_logging_configs(self, hosted_zone_id=None):
        """Return a list of query logging configs."""
        if hosted_zone_id:
            # Does the hosted_zone_id exist?
            response = self.list_hosted_zones()
            zones = list(response) if response else []
            for zone in zones:
                if zone.id == hosted_zone_id:
                    break
            else:
                raise NoSuchHostedZone(hosted_zone_id)

        return list(self.query_logging_configs.values())

    def create_reusable_delegation_set(
        self, caller_reference, delegation_set_id=None, hosted_zone_id=None
    ):
        name_servers = None
        if hosted_zone_id:
            hosted_zone = self.get_hosted_zone(hosted_zone_id)
            name_servers = hosted_zone.delegation_set.name_servers
        delegation_set = DelegationSet(
            caller_reference, name_servers, delegation_set_id
        )
        self.delegation_sets[delegation_set.id] = delegation_set
        return delegation_set

    def list_reusable_delegation_sets(self):
        """
        Pagination is not yet implemented
        """
        return self.delegation_sets.values()

    def delete_reusable_delegation_set(self, delegation_set_id):
        self.delegation_sets.pop(delegation_set_id, None)

    def get_reusable_delegation_set(self, delegation_set_id):
        if delegation_set_id not in self.delegation_sets:
            raise NoSuchDelegationSet(delegation_set_id)
        return self.delegation_sets[delegation_set_id]


route53_backends = BackendDict(
    Route53Backend, "route53", use_boto3_regions=False, additional_regions=["global"]
)
route53_backend = route53_backends["global"]