# Copyright (C) 2018 Riedel Communications GmbH & Co. KG
#
# Modifications Copyright 2018 British Broadcasting Corporation
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

import time
import socket
import os
from requests.compat import json
from jsonschema import ValidationError
from urllib.parse import urlparse
from dnslib import QTYPE
from copy import deepcopy
from collections import defaultdict
from pathlib import Path
from zeroconf import ServiceBrowser, ServiceInfo, Zeroconf

from .. import Config as CONFIG
from ..MdnsListener import MdnsListener
from ..GenericTest import GenericTest, NMOSTestException, NMOS_WIKI_URL
from ..IS04Utils import IS04Utils
from ..TestHelper import get_default_ip, is_ip_address, load_resolved_schema, check_content_type

# IPMX Note: for IS-04 tests we do not attempt to isolate the senders and receivers to only those
#            selected on the command line. We assume that the testing of all the resource is ok
#            unless there is a requirement to have active/inactive senders snd receivers in which
#            case we will apply the filter.
from ..IPMXUtils import filter_resources

NODE_API_KEY = "node"
RECEIVER_CAPS_KEY = "receiver-caps"
CAPS_REGISTER_KEY = "caps-register"
GROUPHINT_KEY = "grouphint"
ASSET_KEY = "asset"


class IS0401Test(GenericTest):
    """
    Runs IS-04-01-Test
    """
    def __init__(self, apis, registries, node, dns_server, auths, **kwargs):
        GenericTest.__init__(self, apis, auths=auths, **kwargs)
        self.invalid_registry = registries[0]
        self.primary_registry = registries[1]
        self.registries = registries[1:]
        self.node = node
        self.dns_server = dns_server
        self.auth = auths[0] if auths else None
        self.node_url = self.apis[NODE_API_KEY]["url"]
        self.registry_basics_done = False
        self.registry_basics_data = []
        self.registry_primary_data = None
        self.registry_invalid_data = None
        self.node_basics_data = {
            "self": None, "devices": None, "sources": None,
            "flows": None, "senders": None, "receivers": None
        }
        self.is04_utils = IS04Utils(self.node_url)
        self.zc = None
        self.zc_listener = None

    def set_up_tests(self):
        self.zc = Zeroconf()
        self.zc_listener = MdnsListener(self.zc)
        if self.dns_server:
            self.dns_server.load_zone(self.apis[NODE_API_KEY]["version"], self.protocol, self.authorization,
                                      "test_data/IS0401/dns_records.zone", CONFIG.PORT_BASE+100)
            print(" * Waiting for up to {} seconds for a DNS query before executing tests"
                  .format(CONFIG.DNS_SD_ADVERT_TIMEOUT))
            self.dns_server.wait_for_query(
                QTYPE.PTR,
                [
                    "_nmos-register._tcp.{}.".format(CONFIG.DNS_DOMAIN),
                    "_nmos-registration._tcp.{}.".format(CONFIG.DNS_DOMAIN)
                ],
                CONFIG.DNS_SD_ADVERT_TIMEOUT
            )
            # Wait for a short time to allow the device to react after performing the query
            time.sleep(CONFIG.API_PROCESSING_TIMEOUT)

    def tear_down_tests(self):
        if self.zc:
            self.zc.close()
            self.zc = None
        if self.dns_server:
            self.dns_server.reset()

    def _strict_service_name(self, info):
        # avoid zeroconf._exceptions.BadTypeInNameException: Service name (nmos-registration) must be <= 15 bytes
        return len(info.type[1:info.type.find('.')]) <= 15

    def _mdns_info(self, port, service_type, txt={}, api_ver=None, api_proto=None, api_auth=None, ip=None):
        """Get an mDNS ServiceInfo object in order to create an advertisement"""
        if api_ver is None:
            api_ver = self.apis[NODE_API_KEY]["version"]
        if api_proto is None:
            api_proto = self.protocol
        if api_auth is None:
            api_auth = self.authorization

        if ip is None:
            ip = get_default_ip()
            hostname = "nmos-mocks.local."
        else:
            hostname = ip.replace(".", "-") + ".local."

        # TODO: Add another test which checks support for parsing CSV string in api_ver
        txt = {**txt, 'api_ver': api_ver, 'api_proto': api_proto, 'api_auth': str(api_auth).lower()}

        info = ServiceInfo(service_type,
                           "NMOSTestSuite{}{}.{}".format(port, api_proto, service_type),
                           addresses=[socket.inet_aton(ip)], port=port,
                           properties=txt, server=hostname)
        return info

    def _registry_mdns_info(self, port, priority=0, api_ver=None, api_proto=None, api_auth=None, ip=None):
        service_type = "_nmos-registration._tcp.local."
        if self.is04_utils.compare_api_version(self.apis[NODE_API_KEY]["version"], "v1.3") >= 0:
            service_type = "_nmos-register._tcp.local."

        txt = {'pri': str(priority)}

        return self._mdns_info(port, service_type, txt, api_ver, api_proto, api_auth, ip)

    def _node_mdns_info(self, port, api_ver=None, api_proto=None, api_auth=None, ip=None):
        service_type = "_nmos-node._tcp.local."

        txt = {'ver_slf': 0, 'ver_src': 0, 'ver_flw': 0, 'ver_dvc': 0, 'ver_snd': 0, 'ver_rcv': 0}

        return self._mdns_info(port, service_type, txt, api_ver, api_proto, api_auth, ip)

    def do_node_basics_prereqs(self):
        """Collect a copy of each of the Node's resources"""
        for resource in self.node_basics_data:
            url = "{}{}".format(self.node_url, resource)
            valid, r = self.do_request("GET", url)
            if valid and r.status_code == 200:
                try:
                    self.node_basics_data[resource] = r.json()
                except Exception:
                    pass

    def do_registry_basics_prereqs(self):
        """Advertise a registry and collect data from any Nodes which discover it"""

        if self.registry_basics_done:
            return

        if not CONFIG.ENABLE_DNS_SD:
            self.do_node_basics_prereqs()
            return

        if CONFIG.DNS_SD_MODE == "multicast":
            registry_mdns = []
            priority = 0

            # Add advertisement with invalid version
            info = self._registry_mdns_info(self.invalid_registry.get_data().port, priority, "v9.0")
            registry_mdns.append(info)
            # Add advertisement with invalid protocol
            info = self._registry_mdns_info(self.invalid_registry.get_data().port, priority, None, "invalid")
            registry_mdns.append(info)

            # Add advertisement for primary and failover registries
            for registry in self.registries[0:-1]:
                info = self._registry_mdns_info(registry.get_data().port, priority)
                registry_mdns.append(info)
                priority += 10

            # Add a fake advertisement for a timeout simulating registry
            info = self._registry_mdns_info(444, priority, ip="192.0.2.1")
            registry_mdns.append(info)
            priority += 10

            # Add the final real registry advertisement
            info = self._registry_mdns_info(self.registries[-1].get_data().port, priority)
            registry_mdns.append(info)

        # Reset all registries to clear previous heartbeats, etc.
        self.invalid_registry.reset()
        for registry in self.registries:
            registry.reset()

        self.invalid_registry.enable()
        self.primary_registry.enable()

        if CONFIG.DNS_SD_MODE == "multicast":
            # Advertise the primary registry and invalid ones at pri 0, and allow the Node to do a basic registration
            if self.is04_utils.compare_api_version(self.apis[NODE_API_KEY]["version"], "v1.0") != 0:
                # self.zc.register_service(registry_mdns[0], strict=self._strict_service_name(registry_mdns[0]))
                # self.zc.register_service(registry_mdns[1], strict=self._strict_service_name(registry_mdns[1]))
                self.zc.register_service(registry_mdns[0])
                self.zc.register_service(registry_mdns[1])
            # self.zc.register_service(registry_mdns[2], strict=self._strict_service_name(registry_mdns[2]))
            self.zc.register_service(registry_mdns[2])

        # Wait for n seconds after advertising the service for the first POST from a Node
        start_time = time.time()
        while time.time() < start_time + CONFIG.DNS_SD_ADVERT_TIMEOUT:
            if self.primary_registry.has_registrations():
                break
            if self.invalid_registry.has_registrations():
                break
            time.sleep(0.2)

        # Wait until we're sure the Node has registered everything it intends to, and we've had at least one heartbeat
        while (time.time() - self.primary_registry.last_time) < CONFIG.HEARTBEAT_INTERVAL + 1 or \
              (time.time() - self.invalid_registry.last_time) < CONFIG.HEARTBEAT_INTERVAL + 1:
            time.sleep(0.2)

        # Collect matching resources from the Node
        self.do_node_basics_prereqs()

        # Ensure we have two heartbeats from the Node, assuming any are arriving (for test_05)
        if len(self.primary_registry.get_data().heartbeats) > 0 or len(self.invalid_registry.get_data().heartbeats) > 0:
            # It is heartbeating, but we don't have enough of them yet
            while len(self.primary_registry.get_data().heartbeats) < 2 and \
                    len(self.invalid_registry.get_data().heartbeats) < 2:
                time.sleep(0.2)

            # Once registered, advertise all other registries at different (ascending) priorities
            for index, registry in enumerate(self.registries[1:]):
                registry.enable()

            if CONFIG.DNS_SD_MODE == "multicast":
                for info in registry_mdns[3:]:
                    # self.zc.register_service(info, strict=self._strict_service_name(info))
                    self.zc.register_service(info)

            # Kill registries one by one to collect data around failover
            self.invalid_registry.disable()
            for index, registry in enumerate(self.registries):
                registry.disable()

                # Prevent access to an out of bounds index below
                if (index + 1) >= len(self.registries):
                    break

                # in event of testing HTTPS support, the TLS handshake seems to take nearly 2 seconds, so
                # when the first registry is disabled, an additional few seconds is needed to ensure the node
                # has a chance to make a connection to it, receive the 5xx error, and make a connection to
                # the next one
                if CONFIG.ENABLE_HTTPS:
                    heartbeat_countdown = CONFIG.HEARTBEAT_INTERVAL + 1 + 5
                else:
                    heartbeat_countdown = CONFIG.HEARTBEAT_INTERVAL + 1

                # Wait an extra heartbeat interval when dealing with the timout test
                # This allows a Node's connection to time out and then register with the next mock registry
                if (index + 2) == len(self.registries):
                    heartbeat_countdown += CONFIG.HEARTBEAT_INTERVAL

                while len(self.registries[index + 1].get_data().heartbeats) < 1 and heartbeat_countdown > 0:
                    # Wait until the heartbeat interval has elapsed or a heartbeat has been received
                    time.sleep(0.2)
                    heartbeat_countdown -= 0.2

                if len(self.registries[index + 1].get_data().heartbeats) < 1:
                    # Testing has failed at this point, so we might as well abort
                    break

        # Clean up mDNS advertisements and disable registries
        if CONFIG.DNS_SD_MODE == "multicast":
            for info in registry_mdns:
                self.zc.unregister_service(info)
        self.invalid_registry.disable()
        for index, registry in enumerate(self.registries):
            registry.disable()

        self.registry_basics_done = True
        for registry in self.registries:
            self.registry_basics_data.append(registry.get_data())
        self.registry_invalid_data = self.invalid_registry.get_data()

        # If the Node preferred the invalid registry, don't penalise it for other tests which check the general
        # interactions are correct
        if len(self.registry_invalid_data.posts) > 0:
            self.registry_primary_data = self.registry_invalid_data
        else:
            self.registry_primary_data = self.registry_basics_data[0]

    def test_01(self, test):
        """Node can discover network registration service via multicast DNS"""

        if not CONFIG.ENABLE_DNS_SD or CONFIG.DNS_SD_MODE != "multicast":
            return test.DISABLED("This test cannot be performed when ENABLE_DNS_SD is False or DNS_SD_MODE is not "
                                 "'multicast'")

        self.do_registry_basics_prereqs()

        registry_data = self.registry_primary_data
        if len(registry_data.posts) > 0:
            return test.PASS()

        return test.FAIL("Node did not attempt to register with the advertised registry.")

    def test_01_01(self, test):
        """Node does not attempt to register with an unsuitable registry"""

        if self.is04_utils.compare_api_version(self.apis[NODE_API_KEY]["version"], "v1.0") == 0:
            return test.NA("Nodes running v1.0 do not check DNS-SD api_ver and api_proto TXT records")

        if not CONFIG.ENABLE_DNS_SD or CONFIG.DNS_SD_MODE != "multicast":
            return test.DISABLED("This test cannot be performed when ENABLE_DNS_SD is False or DNS_SD_MODE is not "
                                 "'multicast'")

        self.do_registry_basics_prereqs()

        if len(self.registry_invalid_data.posts) > 0:
            return test.FAIL("Node incorrectly registered with a registry advertising an invalid 'api_ver' or "
                             "'api_proto'")

        return test.PASS()

    def test_02(self, test):
        """Node can discover network registration service via unicast DNS"""

        if not CONFIG.ENABLE_DNS_SD or CONFIG.DNS_SD_MODE != "unicast":
            return test.DISABLED("This test cannot be performed when ENABLE_DNS_SD is False or DNS_SD_MODE is not "
                                 "'unicast'")

        self.do_registry_basics_prereqs()

        registry_data = self.registry_primary_data
        if len(registry_data.posts) > 0:
            return test.PASS()

        return test.FAIL("Node did not attempt to register with the advertised registry.")

    def test_02_01(self, test):
        """Node does not attempt to register with an unsuitable registry"""

        if self.is04_utils.compare_api_version(self.apis[NODE_API_KEY]["version"], "v1.0") == 0:
            return test.NA("Nodes running v1.0 do not check DNS-SD api_ver and api_proto TXT records")

        if not CONFIG.ENABLE_DNS_SD or CONFIG.DNS_SD_MODE != "unicast":
            return test.DISABLED("This test cannot be performed when ENABLE_DNS_SD is False or DNS_SD_MODE is not "
                                 "'unicast'")

        self.do_registry_basics_prereqs()

        if len(self.registry_invalid_data.posts) > 0:
            return test.FAIL("Node incorrectly registered with a registry advertising an invalid 'api_ver' or "
                             "'api_proto'")

        return test.PASS()

    def test_03(self, test):
        """Registration API interactions use the correct headers"""

        if not CONFIG.ENABLE_DNS_SD:
            return test.DISABLED("This test cannot be performed when ENABLE_DNS_SD is False")

        self.do_registry_basics_prereqs()

        registry_data = self.registry_primary_data
        if len(registry_data.posts) == 0:
            return test.UNCLEAR("No registrations found")

        ctype_warn = ""
        for resource in registry_data.posts:
            ctype_valid, ctype_message = check_content_type(resource[1]["headers"])
            if not ctype_valid:
                return test.FAIL(ctype_message)
            elif ctype_message and not ctype_warn:
                ctype_warn = ctype_message

            accept_valid, accept_message = self.check_accept(resource[1]["headers"])
            if not accept_valid:
                return test.FAIL(accept_message)

            if "Transfer-Encoding" not in resource[1]["headers"]:
                if "Content-Length" not in resource[1]["headers"]:
                    return test.FAIL("One or more Node POSTs did not include Content-Length")
            else:
                if "Content-Length" in resource[1]["headers"]:
                    return test.FAIL("API signalled both Transfer-Encoding and Content-Length")

        if ctype_warn:
            return test.WARNING(ctype_warn)
        else:
            return test.PASS()

    def test_03_01(self, test):
        """Registration API interactions use the correct versioned path"""

        if not CONFIG.ENABLE_DNS_SD:
            return test.DISABLED("This test cannot be performed when ENABLE_DNS_SD is False")

        api = self.apis[NODE_API_KEY]

        self.do_registry_basics_prereqs()

        registry_data = self.registry_primary_data
        if len(registry_data.posts) == 0:
            return test.UNCLEAR("No registrations found")

        for resource in registry_data.posts:
            if resource[1]["version"] != api["version"]:
                return test.FAIL("One or more Node POSTs used version '{}' instead of '{}'"
                                 .format(resource[1]["version"], api["version"]))

        for resource in registry_data.deletes:
            if resource[1]["version"] != api["version"]:
                return test.FAIL("One or more Node DELETEs used version '{}' instead of '{}'"
                                 .format(resource[1]["version"], api["version"]))

        for resource in registry_data.heartbeats:
            if resource[1]["version"] != api["version"]:
                return test.FAIL("One or more Node heartbeats used version '{}' instead of '{}'"
                                 .format(resource[1]["version"], api["version"]))

        return test.PASS()

    def get_registry_resource(self, res_type, res_id):
        """Get a specific resource ID from the mock registry, or a real registry if DNS-SD is disabled"""
        found_resource = None
        if CONFIG.ENABLE_DNS_SD:
            # Look up data in local mock registry
            registry_data = self.registry_primary_data
            for resource in registry_data.posts:
                if resource[1]["payload"]["type"] == res_type and resource[1]["payload"]["data"]["id"] == res_id:
                    found_resource = resource[1]["payload"]["data"]
        else:
            # Look up data from a configured Query API
            url = "{}://{}:{}/x-nmos/query/{}/{}s/{}".format(
                self.protocol,
                CONFIG.QUERY_API_HOST,
                str(CONFIG.QUERY_API_PORT),
                self.apis[NODE_API_KEY]["version"],
                res_type,
                res_id
            )

            try:
                valid, r = self.do_request("GET", url)
                if valid and r.status_code == 200:
                    found_resource = r.json()
                else:
                    raise Exception
            except Exception:
                print(" * ERROR: Unable to load resource from the configured Query API ({}:{})".format(
                    CONFIG.QUERY_API_HOST,
                    CONFIG.QUERY_API_PORT
                ))
        return found_resource

    def get_node_resources(self, res_type):
        """Get resources matching a specific type from the Node API"""
        if res_type == "node":
            res_type = "self"
        else:
            res_type = res_type + "s"
        resp_json = self.node_basics_data[res_type]
        resources = {}
        if resp_json is None:
            raise ValueError
        elif isinstance(resp_json, dict):
            resources[resp_json["id"]] = resp_json
        else:
            for resource in resp_json:
                resources[resource["id"]] = resource
        return resources

    def do_test_matching_resource(self, test, res_type):
        """Check that a resource held in the registry matches the resource held by the Node API"""
        try:
            node_resources = self.get_node_resources(res_type)

            if len(node_resources) == 0:
                return test.UNCLEAR("No {} resources were found on the Node.".format(res_type.title()))

            for res_id in node_resources:
                reg_resource = self.get_registry_resource(res_type, res_id)
                if not reg_resource:
                    return test.FAIL("{} {} was not found in the registry.".format(res_type.title(), res_id))
                elif reg_resource != node_resources[res_id]:
                    return test.FAIL("Node API JSON does not match data in registry for "
                                     "{} {}. registry {} node {}".format(res_type.title(), res_id, reg_resource, node_resources[res_id]))

            return test.PASS()
        except ValueError:
            return test.FAIL("Failed to reach Node API or invalid JSON received!")

    def parent_resource_type(self, res_type):
        """Find the parent resource type required for a given resource type"""
        if res_type == "device":
            return "node"
        elif res_type == "flow" and \
                self.is04_utils.compare_api_version(self.apis[NODE_API_KEY]["version"], "v1.0") <= 0:
            return "source"
        elif res_type in ["sender", "receiver", "source", "flow"]:
            return "device"
        else:
            return None

    def preceding_resource_type(self, res_type):
        """Find the preceding resource type recommended for a given resource type,
        if different than the parent resource type"""
        # The recommendation ensures e.g. that a Query API client would find the Source and Flow
        # associated with a particular Sender
        if res_type == "flow" and \
                self.is04_utils.compare_api_version(self.apis[NODE_API_KEY]["version"], "v1.0") > 0:
            return "source"
        elif res_type == "sender":
            return "flow"
        else:
            return None

    def do_test_referential_integrity(self, test, res_type):
        """Check that the parents for a specific resource type are held in the mock registry,
        and the recommended order for referential integrity has been adhered to"""

        api = self.apis[NODE_API_KEY]
        api_docs_numbered = self.is04_utils.compare_api_version(api["version"], "v1.2") <= 0

        # Look up data in local mock registry
        registry_data = self.registry_primary_data
        parent_type = self.parent_resource_type(res_type)
        registered_parents = []
        preceding_type = self.preceding_resource_type(res_type)
        registered_preceding = []

        preceding_warn = ""
        found_resource = False
        try:
            # Cycle over registrations in order
            for resource in registry_data.posts:
                rtype = resource[1]["payload"]["type"]
                rdata = resource[1]["payload"]["data"]
                if rtype == parent_type:
                    registered_parents.append(rdata["id"])
                elif preceding_type and rtype == preceding_type:
                    registered_preceding.append(rdata["id"])
                elif rtype == res_type:
                    found_resource = True
                    if rdata[parent_type + "_id"] not in registered_parents:
                        return test.FAIL("{} '{}' was registered before its referenced '{}' '{}'"
                                         .format(res_type.title(), rdata["id"],
                                                 parent_type + "_id", rdata[parent_type + "_id"]))
                    if preceding_type and rdata[preceding_type + "_id"] and \
                            rdata[preceding_type + "_id"] not in registered_preceding and not preceding_warn:
                        preceding_warn = "{} '{}' was registered before its referenced '{}' '{}'" \
                                         .format(res_type.title(), rdata["id"],
                                                 preceding_type + "_id", rdata[preceding_type + "_id"])
            if preceding_warn:
                return test.WARNING(preceding_warn,
                                    "https://specs.amwa.tv/is-04/branches/{}"
                                    "/docs/{}Behaviour_-_Registration.html#referential-integrity"
                                    .format(api["spec_branch"], "4.1._" if api_docs_numbered else ""))
            elif found_resource:
                return test.PASS()
            else:
                return test.UNCLEAR("No {} resources were registered with the mock registry.".format(res_type.title()))
        except KeyError as e:
            return test.FAIL("Unable to find expected key in the registered {}: {}".format(res_type.title(), e))

    def test_04(self, test):
        """Node can register a valid Node resource with the network registration service,
        matching its Node API self resource"""

        self.do_registry_basics_prereqs()

        return self.do_test_matching_resource(test, "node")

    def test_05(self, test):
        """Node maintains itself in the registry via periodic calls to the health resource"""

        if not CONFIG.ENABLE_DNS_SD:
            return test.DISABLED("This test cannot be performed when ENABLE_DNS_SD is False")

        api = self.apis[NODE_API_KEY]
        api_docs_numbered = self.is04_utils.compare_api_version(api["version"], "v1.2") <= 0

        self.do_registry_basics_prereqs()

        registry_data = self.registry_primary_data
        if len(registry_data.heartbeats) < 2:
            return test.FAIL("Not enough heartbeats were made in the time period.")

        initial_node = registry_data.posts[0]

        last_hb = None
        for heartbeat in registry_data.heartbeats:
            # Ensure the Node ID for heartbeats matches the registrations
            if heartbeat[1]["node_id"] != initial_node[1]["payload"]["data"]["id"]:
                return test.FAIL("Heartbeats matched a different Node ID to the initial registration.")

            if last_hb:
                # Check frequency of heartbeats matches the defaults
                time_diff = heartbeat[0] - last_hb[0]
                if time_diff > CONFIG.HEARTBEAT_INTERVAL + 0.5:
                    return test.FAIL("Heartbeats are not frequent enough.")
                elif time_diff < CONFIG.HEARTBEAT_INTERVAL - 0.5:
                    return test.FAIL("Heartbeats are too frequent.")
            else:
                # For first heartbeat, check against Node registration
                if (heartbeat[0] - initial_node[0]) > CONFIG.HEARTBEAT_INTERVAL + 0.5:
                    return test.FAIL("First heartbeat occurred too long after initial Node registration.")

            # Ensure the heartbeat request body is empty
            if heartbeat[1]["payload"] is not bytes():
                return test.WARNING("Heartbeat POST contained a payload body.",
                                    "https://specs.amwa.tv/is-04/branches/{}"
                                    "/docs/{}APIs_-_Client_Side_Implementation_Notes.html#empty-request-bodies"
                                    .format(api["spec_branch"], "2.2._" if api_docs_numbered else ""))

            if "Content-Type" in heartbeat[1]["headers"]:
                return test.WARNING("Heartbeat POST contained a Content-Type header.",
                                    "https://specs.amwa.tv/is-04/branches/{}"
                                    "/docs/{}APIs_-_Client_Side_Implementation_Notes.html#empty-request-bodies"
                                    .format(api["spec_branch"], "2.2._" if api_docs_numbered else ""))

            if "Transfer-Encoding" not in heartbeat[1]["headers"]:
                if "Content-Length" not in heartbeat[1]["headers"] or \
                        int(heartbeat[1]["headers"]["Content-Length"]) != 0:
                    # The NMOS spec currently says Content-Length: 0 is OPTIONAL, but it is RECOMMENDED in RFC 7230
                    # and omitting it causes problems for commonly deployed HTTP servers
                    return test.WARNING("Heartbeat POST did not contain a valid Content-Length header.",
                                        "https://specs.amwa.tv/is-04/branches/{}"
                                        "/docs/{}APIs_-_Client_Side_Implementation_Notes.html#empty-request-bodies"
                                        .format(api["spec_branch"], "2.2._" if api_docs_numbered else ""))
            else:
                if "Content-Length" in heartbeat[1]["headers"]:
                    return test.FAIL("API signalled both Transfer-Encoding and Content-Length")

            accept_valid, accept_message = self.check_accept(heartbeat[1]["headers"])
            if not accept_valid:
                return test.FAIL(accept_message)

            last_hb = heartbeat

        return test.PASS()

    def test_07(self, test):
        """Node can register a valid Device resource with the network registration service, matching its
        Node API Device resource"""

        self.do_registry_basics_prereqs()

        return self.do_test_matching_resource(test, "device")

    def test_07_01(self, test):
        """Registered Device was POSTed after a matching referenced Node"""

        if not CONFIG.ENABLE_DNS_SD:
            return test.DISABLED("This test cannot be performed when ENABLE_DNS_SD is False")

        self.do_registry_basics_prereqs()

        return self.do_test_referential_integrity(test, "device")

    def test_08(self, test):
        """Node can register a valid Source resource with the network
        registration service, matching its Node API Source resource"""

        self.do_registry_basics_prereqs()

        return self.do_test_matching_resource(test, "source")

    def test_08_01(self, test):
        """Registered Source was POSTed after a matching referenced Device"""

        if not CONFIG.ENABLE_DNS_SD:
            return test.DISABLED("This test cannot be performed when ENABLE_DNS_SD is False")

        self.do_registry_basics_prereqs()

        return self.do_test_referential_integrity(test, "source")

    def test_09(self, test):
        """Node can register a valid Flow resource with the network
        registration service, matching its Node API Flow resource"""

        self.do_registry_basics_prereqs()

        return self.do_test_matching_resource(test, "flow")

    def test_09_01(self, test):
        """Registered Flow was POSTed after a matching referenced Device or Source"""

        if not CONFIG.ENABLE_DNS_SD:
            return test.DISABLED("This test cannot be performed when ENABLE_DNS_SD is False")

        self.do_registry_basics_prereqs()

        return self.do_test_referential_integrity(test, "flow")

    def test_10(self, test):
        """Node can register a valid Sender resource with the network
        registration service, matching its Node API Sender resource"""

        self.do_registry_basics_prereqs()

        return self.do_test_matching_resource(test, "sender")

    def test_10_01(self, test):
        """Registered Sender was POSTed after a matching referenced Device"""

        if not CONFIG.ENABLE_DNS_SD:
            return test.DISABLED("This test cannot be performed when ENABLE_DNS_SD is False")

        self.do_registry_basics_prereqs()

        return self.do_test_referential_integrity(test, "sender")

    def test_11(self, test):
        """Node can register a valid Receiver resource with the network
        registration service, matching its Node API Receiver resource"""

        self.do_registry_basics_prereqs()

        return self.do_test_matching_resource(test, "receiver")

    def test_11_01(self, test):
        """Registered Receiver was POSTed after a matching referenced Device"""

        if not CONFIG.ENABLE_DNS_SD:
            return test.DISABLED("This test cannot be performed when ENABLE_DNS_SD is False")

        self.do_registry_basics_prereqs()

        return self.do_test_referential_integrity(test, "receiver")

    def test_12(self, test):
        """Node advertises a Node type mDNS announcement with no ver_* TXT records
        in the presence of a Registration API (v1.0, v1.1 and v1.2)"""

        if not CONFIG.ENABLE_DNS_SD:
            return test.DISABLED("This test cannot be performed when ENABLE_DNS_SD is False")

        api = self.apis[NODE_API_KEY]

        if self.is04_utils.compare_api_version(api["version"], "v1.3") >= 0:
            return test.DISABLED("This test is disabled for Nodes >= v1.3")

        node_list = self.collect_mdns_announcements()

        for node in node_list:
            port = node.port
            if port != api["port"]:
                continue
            for address in node.addresses:
                address = socket.inet_ntoa(address)
                if address != api["ip"]:
                    continue
                properties = self.convert_bytes(node.properties)
                for prop in properties:
                    if "ver_" in prop:
                        return test.FAIL("Found 'ver_' TXT record while Node is registered.")

                if self.is04_utils.compare_api_version(api["version"], "v1.1") >= 0:
                    if "api_ver" not in properties:
                        return test.FAIL("No 'api_ver' TXT record found in Node API advertisement.")
                    elif api["version"] not in properties["api_ver"].split(","):
                        return test.FAIL("Node does not claim to support version under test.")

                    if "api_proto" not in properties:
                        return test.FAIL("No 'api_proto' TXT record found in Node API advertisement.")
                    elif properties["api_proto"] != self.protocol:
                        return test.FAIL("API protocol ('api_proto') TXT record is not '{}'.".format(self.protocol))

                if self.is04_utils.compare_api_version(api["version"], "v1.3") >= 0:
                    if "api_auth" not in properties:
                        return test.FAIL("No 'api_auth' TXT record found in Node API advertisement.")
                    elif properties["api_auth"] != str(self.authorization).lower():
                        return test.FAIL("API authorization ('api_auth') TXT record is not '{}'."
                                         .format(str(self.authorization).lower()))

                return test.PASS()

        return test.WARNING("No matching mDNS announcement found for Node with IP/Port {}:{}. This will not affect "
                            "operation in registered mode but may indicate a lack of support for peer to peer "
                            "operation.".format(api["ip"], api["port"]),
                            NMOS_WIKI_URL + "/IS-04#nodes-peer-to-peer-mode")

    def test_12_01(self, test):
        """Node does not advertise a Node type mDNS announcement in the presence of a Registration API (v1.3+)"""

        if not CONFIG.ENABLE_DNS_SD:
            return test.DISABLED("This test cannot be performed when ENABLE_DNS_SD is False")

        api = self.apis[NODE_API_KEY]

        if self.is04_utils.compare_api_version(api["version"], "v1.3") < 0:
            return test.DISABLED("This test is disabled for Nodes < v1.3")

        node_list = self.collect_mdns_announcements()

        for node in node_list:
            port = node.port
            if port != api["port"]:
                continue
            for address in node.addresses:
                address = socket.inet_ntoa(address)
                if address != api["ip"]:
                    continue
                properties = self.convert_bytes(node.properties)
                if "api_ver" not in properties:
                    return test.FAIL("No 'api_ver' TXT record found in Node API advertisement.")

                min_version_lt_v1_3 = False
                for api_version in properties["api_ver"].split(","):
                    if self.is04_utils.compare_api_version(api_version, "v1.3") < 0:
                        min_version_lt_v1_3 = True

                if not min_version_lt_v1_3:
                    return test.WARNING("Nodes which support v1.3+ only should not advertise via mDNS when in "
                                        "registered mode.")

        return test.PASS()

    def test_13(self, test):
        """PUTing to a Receiver target resource with a Sender resource payload is accepted
        and connects the Receiver to a stream"""

        if CONFIG.DNS_SD_MODE == "multicast":
            sender_info = self._node_mdns_info(self.node.port)

        valid, receivers = self.do_request("GET", self.node_url + "receivers")
        if not valid or receivers.status_code != 200:
            return test.FAIL("Unexpected response from the Node API: {}".format(receivers))

        try:
            found_rtp = False
            formats_tested = defaultdict(int)
            warn_sdp_untested = ""
            for receiver in receivers.json():
                if not receiver["transport"].startswith("urn:x-nmos:transport:rtp"):
                    continue
                found_rtp = True

                caps = receiver["caps"]

                if receiver["format"] == "urn:x-nmos:format:video":
                    media_type = caps["media_types"][0] if "media_types" in caps else "video/raw"
                elif receiver["format"] == "urn:x-nmos:format:audio":
                    media_type = caps["media_types"][0] if "media_types" in caps else "audio/L24"
                elif receiver["format"] == "urn:x-nmos:format:data":
                    media_type = caps["media_types"][0] if "media_types" in caps else "video/smpte291"
                elif receiver["format"] == "urn:x-nmos:format:mux":
                    media_type = caps["media_types"][0] if "media_types" in caps else "video/SMPTE2022-6"
                else:
                    return test.FAIL("Unexpected Receiver format: {}".format(receiver["format"]))

                if CONFIG.MAX_TEST_ITERATIONS > 0:
                    # Limit maximum number of Receivers of each format that are tested
                    if CONFIG.MAX_TEST_ITERATIONS <= formats_tested[receiver["format"]]:
                        continue

                supported_media_types = [
                    "video/raw",
                    "video/jxsv",
                    "audio/L16",
                    "audio/L24",
                    "audio/L32",
                    "video/smpte291",
                    "video/SMPTE2022-6"
                ]
                if media_type not in supported_media_types:
                    if not warn_sdp_untested:
                        warn_sdp_untested = "Could not test Receiver {} because this test cannot generate SDP data " \
                            "for media_type '{}'".format(receiver["id"], media_type)
                    continue

                if CONFIG.DNS_SD_MODE == "multicast":
                    # Advertise the sender to allow the Node to find it to make connection
                    self.zc.register_service(sender_info)

                api = self.apis[NODE_API_KEY]
                request_data = self.node.get_sender(media_type, api["version"])
                self.do_receiver_put(test, receiver["id"], request_data)

                if CONFIG.DNS_SD_MODE == "multicast":
                    self.zc.unregister_service(sender_info)

                time.sleep(CONFIG.API_PROCESSING_TIMEOUT)

                valid, response = self.do_request("GET", self.node_url + "receivers/" + receiver["id"])
                if not valid or response.status_code != 200:
                    return test.FAIL("Unexpected response from the Node API: {}".format(receiver))

                receiver = response.json()
                if receiver["subscription"]["sender_id"] != request_data["id"]:
                    return test.FAIL("Node API Receiver {} subscription does not reflect the subscribed "
                                     "Sender ID".format(receiver["id"]))

                if self.is04_utils.compare_api_version(api["version"], "v1.2") >= 0:
                    if not receiver["subscription"]["active"]:
                        return test.FAIL("Node API Receiver {} subscription does not indicate an active "
                                         "subscription".format(receiver["id"]))

                formats_tested[receiver["format"]] += 1

            if warn_sdp_untested:
                return test.MANUAL(warn_sdp_untested)
            elif found_rtp:
                return test.PASS()
        except json.JSONDecodeError:
            return test.FAIL("Non-JSON response returned from Node API")
        except KeyError as e:
            return test.FAIL("Unable to find expected key: {}".format(e))

        return test.UNCLEAR("Node API does not expose any RTP Receivers")

    def test_14(self, test):
        """PUTing to a Receiver target resource with an empty JSON object payload is accepted and
        disconnects the Receiver from a stream"""

        valid, receivers = self.do_request("GET", self.node_url + "receivers")
        if not valid or receivers.status_code != 200:
            return test.FAIL("Unexpected response from the Node API: {}".format(receivers))

        try:
            test_receiver = None
            for receiver in receivers.json():
                if not receiver["transport"].startswith("urn:x-nmos:transport:rtp"):
                    continue
                test_receiver = receiver
                break

            if test_receiver is not None:
                self.do_receiver_put(test, test_receiver["id"], {})

                time.sleep(CONFIG.API_PROCESSING_TIMEOUT)

                valid, response = self.do_request("GET", self.node_url + "receivers/" + test_receiver["id"])
                if not valid or response.status_code != 200:
                    return test.FAIL("Unexpected response from the Node API: {}".format(test_receiver))

                receiver = response.json()
                if receiver["subscription"]["sender_id"] is not None:
                    return test.FAIL("Node API Receiver {} subscription does not reflect the subscribed "
                                     "Sender ID".format(receiver["id"]))

                api = self.apis[NODE_API_KEY]
                if self.is04_utils.compare_api_version(api["version"], "v1.2") >= 0:
                    if receiver["subscription"]["active"]:
                        return test.FAIL("Node API Receiver {} subscription does not indicate an inactive "
                                         "subscription".format(receiver["id"]))

                return test.PASS()
        except json.JSONDecodeError:
            return test.FAIL("Non-JSON response returned from Node API")
        except KeyError as e:
            return test.FAIL("Unable to find expected key: {}".format(e))

        return test.UNCLEAR("Node API does not expose any RTP Receivers")

    def test_15(self, test):
        """Node correctly selects a Registration API based on advertised priorities"""

        if not CONFIG.ENABLE_DNS_SD:
            return test.DISABLED("This test cannot be performed when ENABLE_DNS_SD is False")

        self.do_registry_basics_prereqs()

        last_hb = None
        last_registry = None
        # All but the first and last registry can be used for priority tests. The last one is reserved for timeout tests
        for index, registry_data in enumerate(self.registry_basics_data[1:-1]):
            if len(registry_data.heartbeats) < 1:
                return test.FAIL("Node never made contact with registry {} advertised on port {}"
                                 .format(index + 1, registry_data.port))

            first_hb_to_registry = registry_data.heartbeats[0]
            if last_hb:
                if first_hb_to_registry < last_hb:
                    return test.FAIL("Node sent a heartbeat to the registry on port {} before the registry on port {}, "
                                     "despite their priorities requiring the opposite behaviour"
                                     .format(registry_data.port, last_registry.port))

            last_hb = first_hb_to_registry
            last_registry = registry_data

        return test.PASS()

    def test_16(self, test):
        """Node correctly fails over between advertised Registration APIs when one fails"""

        if not CONFIG.ENABLE_DNS_SD:
            return test.DISABLED("This test cannot be performed when ENABLE_DNS_SD is False")

        self.do_registry_basics_prereqs()

        # All but the first and last registry can be used for failover tests. The last one is reserved for timeout tests
        for index, registry_data in enumerate(self.registry_basics_data[1:-1]):
            if len(registry_data.heartbeats) < 1:
                return test.FAIL("Node never made contact with registry {} advertised on port {}"
                                 .format(index + 1, registry_data.port))

            if index > 0:
                for resource in registry_data.posts:
                    if resource[1]["payload"]["type"] == "node":
                        return test.FAIL("Node re-registered its resources when it failed over to a new registry, when "
                                         "it should only have issued a heartbeat")

        return test.PASS()

    def test_16_01(self, test):
        """Node correctly handles Registration APIs whose connections time out"""

        if not CONFIG.ENABLE_DNS_SD:
            return test.DISABLED("This test cannot be performed when ENABLE_DNS_SD is False")

        self.do_registry_basics_prereqs()

        # The second to last registry will intentionally cause a timeout. Check here that the Node successfully times
        # out its attempted connection within a heartbeat period and then registers with the next available one.
        registry_data = self.registry_basics_data[-1]
        if len(registry_data.heartbeats) < 1:
            return test.WARNING("Node never made contact with registry {} advertised on port {}"
                                .format(len(self.registry_basics_data), registry_data.port))

        for resource in registry_data.posts:
            if resource[1]["payload"]["type"] == "node":
                return test.WARNING("Node re-registered its resources when it failed over to a new registry, when it "
                                    "should only have issued a heartbeat")

        return test.PASS()

    def test_17(self, test):
        """All Node resources use different UUIDs"""

        uuids = set()
        valid, response = self.do_request("GET", self.node_url + "self")
        if not valid or response.status_code != 200:
            return test.FAIL("Unexpected response from the Node API: {}".format(response))
        try:
            uuids.add(response.json()["id"])
        except json.JSONDecodeError:
            return test.FAIL("Non-JSON response returned from Node API")
        except KeyError as e:
            return test.FAIL("Unable to find expected key: {}".format(e))

        for resource_type in ["devices", "sources", "flows", "senders", "receivers"]:
            valid, response = self.do_request("GET", self.node_url + resource_type)
            if not valid or response.status_code != 200:
                return test.FAIL("Unexpected response from the Node API: {}".format(response))
            try:
                for resource in response.json():
                    if resource["id"] in uuids:
                        return test.FAIL("Duplicate ID '{}' found in Node API '{}' resource".format(resource["id"],
                                                                                                    resource_type))
                    uuids.add(resource["id"])
            except json.JSONDecodeError:
                return test.FAIL("Non-JSON response returned from Node API")
            except KeyError as e:
                return test.FAIL("Unable to find expected key: {}".format(e))

        return test.PASS()

    def test_17_01(self, test):
        """All Devices refer to their attached Senders and Receivers"""

        # store references from Devices to Senders and Receivers
        from_devices = {}
        # store references to Devices from Senders and Receivers
        to_devices = {}

        # get all the Node's Devices
        valid, response = self.do_request("GET", self.node_url + "devices")
        if not valid or response.status_code != 200:
            return test.FAIL("Unexpected response from the Node API: {}".format(response))
        try:
            for resource in response.json():
                from_devices[resource["id"]] = {
                    "senders": set(resource["senders"]),
                    "receivers": set(resource["receivers"])
                }
        except json.JSONDecodeError:
            return test.FAIL("Non-JSON response returned from Node API")
        except KeyError as e:
            return test.FAIL("Unable to find expected key: {}".format(e))

        if len(from_devices) == 0:
            return test.UNCLEAR("Node API does not expose any Devices")

        # get all the Node's Senders and Receivers
        empty_refs = {"senders": set(), "receivers": set()}
        for resource_type in ["senders", "receivers"]:
            valid, response = self.do_request("GET", self.node_url + resource_type)
            if not valid or response.status_code != 200:
                return test.FAIL("Unexpected response from the Node API: {}".format(response))
            try:
                for resource in response.json():
                    id = resource["device_id"]
                    if id not in to_devices:
                        to_devices[id] = deepcopy(empty_refs)
                    to_devices[id][resource_type].add(resource["id"])
            except json.JSONDecodeError:
                return test.FAIL("Non-JSON response returned from Node API")
            except KeyError as e:
                return test.FAIL("Unable to find expected key: {}".format(e))

        found_empty_refs = False

        for id, from_device in from_devices.items():
            if id not in to_devices:
                if from_device == empty_refs:
                    # no Senders or Receivers are attached to this Device
                    continue
                else:
                    return test.FAIL("Device '{}' references one or more unknown Senders or Receivers."
                                     .format(id))
            to_device = to_devices[id]
            if from_device == empty_refs:
                # Device appears not to be populating the deprecated attributes
                found_empty_refs = True
            else:
                for refs in ["senders", "receivers"]:
                    if len(from_device[refs] - to_device[refs]) > 0:
                        return test.FAIL("Device '{}' references one or more unknown {}."
                                         .format(id, refs.title()))
                    elif len(to_device[refs] - from_device[refs]) > 0:
                        return test.FAIL("Device '{}' does not have a reference to one or more of its {}."
                                         .format(id, refs.title()))
                    # else: references from Device to its Senders and Receivers
                    # match references from Senders and Receivers to that Device

        if found_empty_refs:
            return test.WARNING("One or more Devices do not have references to any of their Senders or Receivers. "
                                "(The 'senders' and 'receivers' attributes are deprecated since IS-04 v1.2.)")

        return test.PASS()

    def test_18(self, test):
        """All Node clocks are unique, and relate to any visible Sources' clocks"""

        api = self.apis[NODE_API_KEY]
        if self.is04_utils.compare_api_version(api["version"], "v1.1") < 0:
            return test.NA("Clocks are not available until IS-04 v1.1")

        clocks = set()
        valid, response = self.do_request("GET", self.node_url + "self")
        if not valid or response.status_code != 200:
            return test.FAIL("Unexpected response from the Node API: {}".format(response))
        try:
            for clock in response.json()["clocks"]:
                clock_name = clock["name"]
                if clock_name in clocks:
                    return test.FAIL("Duplicate clock name '{}' found in Node API self resource".format(clock_name))
                clocks.add(clock_name)
        except json.JSONDecodeError:
            return test.FAIL("Non-JSON response returned from Node API")
        except KeyError as e:
            return test.FAIL("Unable to find expected key: {}".format(e))

        valid, response = self.do_request("GET", self.node_url + "sources")
        if not valid or response.status_code != 200:
            return test.FAIL("Unexpected response from the Node API: {}".format(response))
        try:
            for source in response.json():
                clock_name = source["clock_name"]
                if clock_name not in clocks and clock_name is not None:
                    return test.FAIL("Source '{}' uses a non-existent clock name '{}'".format(source["id"], clock_name))
        except json.JSONDecodeError:
            return test.FAIL("Non-JSON response returned from Node API")
        except KeyError as e:
            return test.FAIL("Unable to find expected key: {}".format(e))

        return test.PASS()

    def test_19(self, test):
        """All Node interfaces are unique, and relate to any visible Senders and Receivers' interface_bindings"""

        api = self.apis[NODE_API_KEY]
        if self.is04_utils.compare_api_version(api["version"], "v1.2") < 0:
            return test.NA("Interfaces are not available until IS-04 v1.2")

        interfaces = set()
        valid, response = self.do_request("GET", self.node_url + "self")
        if not valid or response.status_code != 200:
            return test.FAIL("Unexpected response from the Node API: {}".format(response))
        try:
            for interface in response.json()["interfaces"]:
                interface_name = interface["name"]
                if interface_name not in interfaces:
                    interfaces.add(interface_name)
                else:
                    return test.FAIL("Duplicate interface name '{}' found in Node API self resource"
                                     .format(interface_name))
        except json.JSONDecodeError:
            return test.FAIL("Non-JSON response returned from Node API")
        except KeyError as e:
            return test.FAIL("Unable to find expected key: {}".format(e))

        for binder_type in ["senders", "receivers"]:
            valid, response = self.do_request("GET", self.node_url + binder_type)
            if not valid or response.status_code != 200:
                return test.FAIL("Unexpected response from the Node API: {}".format(response))
            try:
                for binder in response.json():
                    if not IS04Utils.transport_uses_interface_bindings(binder["transport"]):
                        continue
                    interface_bindings = binder["interface_bindings"]
                    if len(interface_bindings) == 0:
                        return test.FAIL("{} '{}' does not list any interface_bindings"
                                         .format(binder_type.capitalize().rstrip("s"), binder["id"]))
                    for interface_name in interface_bindings:
                        if interface_name not in interfaces:
                            return test.FAIL("{} '{}' uses a non-existent interface name '{}'"
                                             .format(binder_type.capitalize().rstrip("s"),
                                                     binder["id"],
                                                     interface_name))
            except json.JSONDecodeError:
                return test.FAIL("Non-JSON response returned from Node API")
            except KeyError as e:
                return test.FAIL("Unable to find expected key: {}".format(e))

        if len(interfaces) == 0:
            return test.UNCLEAR("Node 'interfaces' is empty")

        return test.PASS()

    def test_19_01(self, test):
        """All bound Node interfaces have attached_network_device info"""

        api = self.apis[NODE_API_KEY]
        if self.is04_utils.compare_api_version(api["version"], "v1.3") < 0:
            return test.NA("Attached network device info is not available until IS-04 v1.3")

        interfaces = {}
        valid, response = self.do_request("GET", self.node_url + "self")
        if not valid or response.status_code != 200:
            return test.FAIL("Unexpected response from the Node API: {}".format(response))
        try:
            for interface in response.json()["interfaces"]:
                interface_name = interface["name"]
                if interface_name not in interfaces:
                    interfaces[interface_name] = interface
        except json.JSONDecodeError:
            return test.FAIL("Non-JSON response returned from Node API")
        except KeyError as e:
            return test.FAIL("Unable to find expected key: {}".format(e))

        attached_network_device_warn = False

        for binder_type in ["senders", "receivers"]:
            valid, response = self.do_request("GET", self.node_url + binder_type)
            if not valid or response.status_code != 200:
                return test.FAIL("Unexpected response from the Node API: {}".format(response))
            try:
                for binder in response.json():
                    interface_bindings = binder["interface_bindings"]
                    for interface_name in interface_bindings:
                        if interface_name not in interfaces:
                            pass
                        elif "attached_network_device" not in interfaces[interface_name]:
                            attached_network_device_warn = True
            except json.JSONDecodeError:
                return test.FAIL("Non-JSON response returned from Node API")
            except KeyError as e:
                return test.FAIL("Unable to find expected key: {}".format(e))

        if len(interfaces) == 0:
            return test.UNCLEAR("Node 'interfaces' is empty")
        elif attached_network_device_warn:
            return test.OPTIONAL("One or more Node 'interfaces' used by a Sender or Receiver is missing "
                                 "'attached_network_device' info",
                                 NMOS_WIKI_URL + "/IS-04#nodes-interface-neighbour-information")

        return test.PASS()

    def test_20(self, test):
        """Node's resources correctly signal the current protocol and IP/hostname"""

        found_api_endpoint = False
        found_href = False

        href_hostname_warn = False
        api_endpoint_host_warn = False
        service_href_scheme_warn = False
        service_href_hostname_warn = False
        service_href_auth_warn = False
        control_href_scheme_warn = False
        control_href_hostname_warn = False
        control_href_auth_warn = False
        manifest_href_scheme_warn = False
        manifest_href_hostname_warn = False

        api = self.apis[NODE_API_KEY]
        valid, response = self.do_request("GET", self.node_url + "self")
        if not valid or response.status_code != 200:
            return test.FAIL("Unexpected response from the Node API: {}".format(response))
        try:
            node_self = response.json()
            if not node_self["href"].startswith(self.protocol + "://"):
                return test.FAIL("Node 'href' does not match the current protocol")
            if node_self["href"].startswith("https://") and is_ip_address(urlparse(node_self["href"]).hostname):
                href_hostname_warn = True
            if self.is04_utils.compare_api_version(api["version"], "v1.1") >= 0:
                for endpoint in node_self["api"]["endpoints"]:
                    if endpoint["protocol"] != self.protocol:
                        return test.FAIL("One or more Node 'api.endpoints' do not match the current protocol")
                    if self.is04_utils.compare_api_version(api["version"], "v1.3") >= 0:
                        if self.authorization is not endpoint.get("authorization", False):
                            return test.FAIL("One or more Node 'api.endpoints' do not match the current authorization "
                                             "mode")
                    if endpoint["host"].lower().rstrip('.') == api["hostname"].lower().rstrip('.') and \
                            endpoint["port"] == api["port"]:
                        found_api_endpoint = True
                    if self.is04_utils.compare_urls(node_self["href"], "{}://{}:{}"
                                                    .format(endpoint["protocol"], endpoint["host"], endpoint["port"])):
                        found_href = True
                    if endpoint["protocol"] == "https" and is_ip_address(endpoint["host"]):
                        api_endpoint_host_warn = True
            for service in node_self["services"]:
                if service["type"].startswith("urn:x-nmos:"):
                    href = service["href"]
                    # Only warn about these at the end so that more major failures are flagged first
                    # Protocols other than HTTP and WebSocket may be used, so don't incorrectly flag those too
                    if href.startswith("http") and not href.startswith(self.protocol + "://"):
                        service_href_scheme_warn = True
                    if href.startswith("ws") and not href.startswith(self.ws_protocol + "://"):
                        service_href_scheme_warn = True
                    if (href.startswith("https://") or href.startswith("wss://")) and \
                            is_ip_address(urlparse(href).hostname):
                        service_href_hostname_warn = True
                    if self.is04_utils.compare_api_version(api["version"], "v1.3") >= 0 and \
                            service["type"].startswith("urn:x-nmos:"):
                        if self.authorization is not service.get("authorization", False):
                            service_href_auth_warn = True
        except json.JSONDecodeError:
            return test.FAIL("Non-JSON response returned from Node API")
        except KeyError as e:
            return test.FAIL("Unable to find expected key: {}".format(e))

        if self.is04_utils.compare_api_version(api["version"], "v1.1") >= 0:
            if not found_api_endpoint:
                return test.FAIL("None of the Node 'api.endpoints' match the current protocol, IP/hostname and port")

            if not found_href:
                return test.FAIL("None of the Node 'api.endpoints' match the Node 'href'")

            valid, response = self.do_request("GET", self.node_url + "devices")
            if not valid or response.status_code != 200:
                return test.FAIL("Unexpected response from the Node API: {}".format(response))
            try:
                node_devices = response.json()
                for device in node_devices:
                    for control in device["controls"]:
                        if control["type"].startswith("urn:x-nmos:"):
                            href = control["href"]
                            # Only warn about these at the end so that more major failures are flagged first
                            # Protocols other than HTTP and WebSocket may be used, so don't incorrectly flag those too
                            if href.startswith("http") and not href.startswith(self.protocol + "://"):
                                control_href_scheme_warn = True
                            if href.startswith("ws") and not href.startswith(self.ws_protocol + "://"):
                                control_href_scheme_warn = True
                            if (href.startswith("https://") or href.startswith("wss://")) and \
                                    is_ip_address(urlparse(href).hostname):
                                control_href_hostname_warn = True
                            if self.is04_utils.compare_api_version(api["version"], "v1.3") >= 0 and \
                                    control["type"].startswith("urn:x-nmos:"):
                                if self.authorization is not control.get("authorization", False):
                                    control_href_auth_warn = True
            except json.JSONDecodeError:
                return test.FAIL("Non-JSON response returned from Node API")
            except KeyError as e:
                return test.FAIL("Unable to find expected key: {}".format(e))

        valid, response = self.do_request("GET", self.node_url + "senders")
        if not valid or response.status_code != 200:
            return test.FAIL("Unexpected response from the Node API: {}".format(response))
        try:
            node_senders = response.json()
            for sender in node_senders:
                href = sender["manifest_href"]
                if href is not None and href.startswith("http") and not href.startswith(self.protocol + "://"):
                    manifest_href_scheme_warn = True
                if href is not None and href.startswith("https://") and is_ip_address(urlparse(href).hostname):
                    manifest_href_hostname_warn = True
        except json.JSONDecodeError:
            return test.FAIL("Non-JSON response returned from Node API")
        except KeyError as e:
            return test.FAIL("Unable to find expected key: {}".format(e))

        if href_hostname_warn:
            return test.WARNING("Node 'href' value has an IP address not a hostname")
        elif api_endpoint_host_warn:
            return test.WARNING("One or more Node 'api.endpoints.host' values are an IP address not a hostname")
        elif service_href_hostname_warn:
            return test.WARNING("One or more Node service 'href' values have an IP address not a hostname")
        elif control_href_hostname_warn:
            return test.WARNING("One or more Device control 'href' values have an IP address not a hostname")
        elif manifest_href_hostname_warn:
            return test.WARNING("One or more Sender 'manifest_href' values have an IP address not a hostname")
        elif service_href_scheme_warn:
            return test.WARNING("One or more Node service 'href' values do not match the current protocol")
        elif control_href_scheme_warn:
            return test.WARNING("One or more Device control 'href' values do not match the current protocol")
        elif manifest_href_scheme_warn:
            return test.WARNING("One or more Sender 'manifest_href' values do not match the current protocol")
        elif service_href_auth_warn:
            return test.WARNING("One or more Node 'x-nmos' services do not match the current authorization mode")
        elif control_href_auth_warn:
            return test.WARNING("One or more Device 'x-nmos' controls do not match the current authorization mode")

        return test.PASS()

    def test_20_01(self, test):
        """Sender manifests use the expected Content-Type"""

        valid, response = self.do_request("GET", self.node_url + "senders")
        if not valid or response.status_code != 200:
            return test.FAIL("Unexpected response from the Node API: {}".format(response))
        try:
            access_error = False
            content_type_warn = None
            node_senders = filter_resources(response.json(), "senders")
            for sender in node_senders:
                if not sender["transport"].startswith("urn:x-nmos:transport:rtp"):
                    continue

                href = sender["manifest_href"]
                if not href:
                    access_error = True
                    continue

                if self.authorization and urlparse(href).path.startswith("/x-nmos/connection"):
                    token = self.auth.generate_token(["connection"], True)
                    headers = {"Authorization": "Bearer {}".format(token)}
                else:
                    headers = None
                valid, response = self.do_request("GET", href, headers=headers)
                if valid and response.status_code == 200:
                    valid, message = check_content_type(response.headers, "application/sdp")
                    if not content_type_warn and (not valid or message != ""):
                        content_type_warn = message
                elif valid and response.status_code == 404:
                    access_error = True
                else:
                    return test.FAIL("Unexpected response from manifest_href '{}': {}"
                                     .format(href, response))

            if len(node_senders) == 0:
                return test.UNCLEAR("No Sender resources were found on the Node.")

            if access_error:
                return test.UNCLEAR("One or more of the tested Senders had null or empty 'manifest_href' or "
                                    "returned a 404 HTTP code. Please ensure all Senders are enabled and re-test.")

            if content_type_warn:
                return test.WARNING(content_type_warn)
        except json.JSONDecodeError:
            return test.FAIL("Non-JSON response returned from Node API")
        except KeyError as e:
            return test.FAIL("Unable to find expected key: {}".format(e))

        return test.PASS()

    def test_21(self, test):
        """Node correctly interprets a 200 code from a registry upon initial registration"""

        if not CONFIG.ENABLE_DNS_SD:
            return test.DISABLED("This test cannot be performed when ENABLE_DNS_SD is False")

        registry_info = self._registry_mdns_info(self.primary_registry.get_data().port, 0)

        # Reset the registry to clear previous heartbeats, and enable in 200 test mode
        self.primary_registry.reset()
        self.primary_registry.enable(first_reg=True)

        if CONFIG.DNS_SD_MODE == "multicast":
            # Advertise a registry at pri 0 and allow the Node to do a basic registration
            # self.zc.register_service(registry_info, strict=self._strict_service_name(registry_info))
            self.zc.register_service(registry_info)

        # Wait for n seconds after advertising the service for the first POST and then DELETE from a Node
        self.primary_registry.wait_for_registration(CONFIG.DNS_SD_ADVERT_TIMEOUT)
        self.primary_registry.wait_for_delete(CONFIG.HEARTBEAT_INTERVAL + 1)

        # Wait for the Node to finish its interactions
        while (time.time() - self.primary_registry.last_time) < CONFIG.HEARTBEAT_INTERVAL + 1:
            time.sleep(0.2)

        # By this point we should have had at least one Node POST and a corresponding DELETE
        if CONFIG.DNS_SD_MODE == "multicast":
            self.zc.unregister_service(registry_info)
        self.primary_registry.disable()

        # Get the relevant Node ID
        url = "{}self".format(self.node_url)
        valid, r = self.do_request("GET", url)
        if valid and r.status_code == 200:
            try:
                # Check that a POST and DELETE match the Node's ID
                node_id = r.json()["id"]
                found_post = False
                for resource in self.primary_registry.get_data().posts:
                    if resource[1]["payload"]["type"] == "node" and resource[1]["payload"]["data"]["id"] == node_id:
                        found_post = True
                if not found_post:
                    return test.FAIL("Node did not attempt to make contact with the registry")
                found_delete = False
                found_extra_deletes = False
                for resource in self.primary_registry.get_data().deletes:
                    if resource[1]["type"] == "node" and resource[1]["id"] == node_id:
                        found_delete = True
                    elif resource[1]["type"] != "node":
                        found_extra_deletes = True
                if not found_delete:
                    return test.FAIL("Node did not attempt to DELETE itself having encountered a 200 code on initial "
                                     "registration")
                elif found_extra_deletes:
                    return test.WARNING("Node DELETEd more than just its 'node' resource. This is unnecessary when "
                                        "encountering a 200 code on initial registration")
            except json.JSONDecodeError:
                return test.FAIL("Non-JSON response returned from Node API")
            except KeyError as e:
                return test.FAIL("Unable to find expected key: {}".format(e))
        else:
            return test.FAIL("Unexpected responses from Node API self resource")

        return test.PASS()

    def test_22(self, test):
        """Node resource IDs persist over a reboot"""

        return test.MANUAL("This check must be performed manually, or via use of the following tool",
                           "https://github.com/AMWA-TV/nmos-testing/blob/master/utilities/uuid-checker/README.md")

    def test_23(self, test):
        """Senders and Receivers correctly use BCP-002-01 grouping syntax"""

        api = self.apis[GROUPHINT_KEY]

        grouphint = "urn:x-nmos:tag:grouphint/v1.0"

        found_groups = False
        found_senders_receivers = False

        for target in ["senders", "receivers"]:
            groups = {"node": {}, "device": {}}
            for resource_name in [target]:
                valid, response = self.do_request("GET", self.node_url + resource_name)
                if valid and response.status_code == 200:
                    try:
                        for resource in response.json():
                            found_senders_receivers = True
                            if resource["device_id"] not in groups["device"]:
                                groups["device"][resource["device_id"]] = {}
                            for tag_name, tag_value in resource["tags"].items():
                                if tag_name != grouphint:
                                    continue
                                if not isinstance(tag_value, list) or len(tag_value) == 0:
                                    return test.FAIL("Group tag for {} {} is not an array or has too few items"
                                                     .format(resource_name.capitalize().rstrip("s"), resource["id"]))
                                found_groups = True
                                for group_def in tag_value:
                                    group_params = group_def.split(":")
                                    group_scope = "device"

                                    # Perform basic validation on the group syntax
                                    if len(group_params) < 2:
                                        return test.FAIL("Group syntax for {} {} has too few parameters"
                                                         .format(resource_name.capitalize().rstrip("s"),
                                                                 resource["id"]))
                                    elif len(group_params) > 3:
                                        return test.FAIL("Group syntax for {} {} has too many parameters"
                                                         .format(resource_name.capitalize().rstrip("s"),
                                                                 resource["id"]))
                                    elif len(group_params) == 3:
                                        if group_params[2] not in ["device", "node"]:
                                            return test.FAIL("Group syntax for {} {} uses an invalid group scope: {}"
                                                             .format(resource_name.capitalize().rstrip("s"),
                                                                     resource["id"], group_params[2]))
                                        group_scope = group_params[2]

                                    # Ensure we have a reference to the group name stored
                                    if group_scope == "node":
                                        if group_params[0] not in groups["node"]:
                                            groups["node"][group_params[0]] = {}
                                        group_ref = groups["node"][group_params[0]]
                                    elif group_scope == "device":
                                        if group_params[0] not in groups["device"][resource["device_id"]]:
                                            groups["device"][resource["device_id"]][group_params[0]] = {}
                                        group_ref = groups["device"][resource["device_id"]][group_params[0]]

                                    # Check for duplicate roles within groups
                                    if group_params[1] in group_ref:
                                        return test.FAIL("Duplicate role found in group {} for resources {} and {}"
                                                         .format(group_params[0], resource["id"],
                                                                 group_ref[group_params[1]]))
                                    else:
                                        group_ref[group_params[1]] = resource["id"]

                    except json.JSONDecodeError:
                        return test.FAIL("Non-JSON response returned from Node API")
                    except KeyError as e:
                        return test.FAIL("Unable to find expected key: {}".format(e))

        if not found_senders_receivers:
            return test.UNCLEAR("No Sender or Receiver resources were found on the Node")
        elif found_groups:
            return test.PASS()
        else:
            return test.OPTIONAL("No BCP-002-01 groups were identified in Sender or Receiver tags",
                                 "https://specs.amwa.tv/bcp-002-01/branches/{}"
                                 "/docs/Natural_Grouping.html"
                                 .format(api["spec_branch"]))

    def test_24(self, test):
        """Periodic Sources specify a 'grain_rate'"""

        valid, response = self.do_request("GET", self.node_url + "sources")
        if valid and response.status_code == 200:
            try:
                for resource in response.json():
                    # Currently testing where it would be particularly unusual to find a non-periodic Source
                    if resource["format"] in ["urn:x-nmos:format:video",
                                              "urn:x-nmos:format:mux"]:
                        if "grain_rate" not in resource:
                            return test.WARNING("Source {} MUST specify a 'grain_rate' if it is periodic"
                                                .format(resource["id"]))
                        source_rate = resource["grain_rate"]
                        if source_rate.get("numerator", 0) == 0 or source_rate.get("denominator", 1) == 0:
                            return test.FAIL("Source {} 'grain_rate' is invalid: {}"
                                             .format(resource["id"], source_rate))
                if len(response.json()) > 0:
                    return test.PASS()
            except json.JSONDecodeError:
                return test.FAIL("Non-JSON response returned from Node API")
            except KeyError as e:
                return test.FAIL("Unable to find expected key: {}".format(e))

        return test.UNCLEAR("No Source resources were found on the Node")

    def test_24_01(self, test):
        """Periodic Flows' 'grain_rate' is divisible by their parent Source 'grain_rate'"""

        source_valid, source_response = self.do_request("GET", self.node_url + "sources")
        flow_valid, flow_response = self.do_request("GET", self.node_url + "flows")

        if source_valid and flow_valid and source_response.status_code == 200 and flow_response.status_code == 200:
            try:
                sources = {source["id"]: source for source in source_response.json()}
                flows = flow_response.json()
                for flow in flows:
                    if "grain_rate" in flow:
                        source = sources[flow["source_id"]]
                        if "grain_rate" not in source:
                            return test.FAIL("Source {} MUST specify a 'grain_rate' because one or more of its "
                                             "child Flows specify a 'grain_rate'".format(source["id"]))
                        flow_rate = flow["grain_rate"]
                        if flow_rate.get("numerator", 0) == 0 or flow_rate.get("denominator", 1) == 0:
                            return test.FAIL("Flow {} 'grain_rate' is invalid: {}".format(flow["id"], flow_rate))
                        source_rate = source["grain_rate"]
                        if source_rate.get("numerator", 0) == 0 or source_rate.get("denominator", 1) == 0:
                            return test.FAIL("Source {} 'grain_rate' is invalid: {}"
                                             .format(source["id"], source_rate))
                        if ((source_rate["numerator"] * flow_rate.get("denominator", 1)) %
                           (flow_rate["numerator"] * source_rate.get("denominator", 1))):
                            return test.FAIL("Flow {} 'grain_rate' MUST be integer divisible by the Source "
                                             "'grain_rate'".format(flow["id"]))
                    elif flow["format"] in ["urn:x-nmos:format:video",
                                            "urn:x-nmos:format:mux"]:
                        return test.WARNING("Flow {} SHOULD specify a 'grain_rate' if it is periodic"
                                            .format(flow["id"]))
                if len(flow_response.json()) > 0:
                    return test.PASS()
            except json.JSONDecodeError:
                return test.FAIL("Non-JSON response returned from Node API")
            except KeyError:
                return test.FAIL("No Source found for one or more advertised Flows")

        return test.UNCLEAR("No Source or Flow resources were found on the Node")

    def test_25(self, test):
        """Receivers expose expected 'caps' for their API version"""

        api = self.apis[NODE_API_KEY]
        api_docs_numbered = self.is04_utils.compare_api_version(api["version"], "v1.2") <= 0

        if self.is04_utils.compare_api_version(api["version"], "v1.1") < 0:
            return test.NA("Capabilities are not used before API v1.1")

        receivers_valid, receivers_response = self.do_request("GET", self.node_url + "receivers")

        no_receivers = True
        if receivers_valid and receivers_response.status_code == 200:
            try:
                for receiver in receivers_response.json():
                    no_receivers = False
                    if "media_types" not in receiver["caps"]:
                        return test.WARNING("Receiver 'caps' should include a list of accepted 'media_types', unless "
                                            "this Receiver can handle any 'media_type'",
                                            "https://specs.amwa.tv/is-04/branches/{}"
                                            "/docs/{}Behaviour_-_Nodes.html#all-resources"
                                            .format(api["spec_branch"], "4.3._" if api_docs_numbered else ""))
                    if self.is04_utils.compare_api_version(api["version"], "v1.3") >= 0:
                        if receiver["format"] == "urn:x-nmos:format:data" and \
                               receiver["transport"] in ["urn:x-nmos:transport:websocket", "urn:x-nmos:transport:mqtt"]:
                            # Technically this is a bit IS-07 specific, but it may still be best placed here for now
                            if "event_types" not in receiver["caps"]:
                                return test.WARNING("Receiver 'caps' should include a list of accepted 'event_types' "
                                                    "if the Receiver accepts IS-07 events, unless this Receiver can "
                                                    "handle any 'event_type'",
                                                    "https://specs.amwa.tv/is-04/branches/{}"
                                                    "/docs/{}Behaviour_-_Nodes.html#all-resources"
                                                    .format(api["spec_branch"], "4.3._" if api_docs_numbered else ""))
            except json.JSONDecodeError:
                return test.FAIL("Non-JSON response returned from Node API")
            except KeyError as e:
                return test.FAIL("Unable to find expected key in the Receiver: {}".format(e))

        if no_receivers:
            return test.UNCLEAR("No Receivers were found on the Node")
        else:
            return test.PASS()

    def test_26(self, test):
        """Source 'format' matches Flow 'format'"""

        source_valid, source_response = self.do_request("GET", self.node_url + "sources")
        flow_valid, flow_response = self.do_request("GET", self.node_url + "flows")

        if source_valid and flow_valid and source_response.status_code == 200 and flow_response.status_code == 200:
            try:
                sources = {source["id"]: source for source in source_response.json()}
                flows = flow_response.json()
                for flow in flows:
                    source = sources[flow["source_id"]]
                    if flow["format"] != source["format"]:
                        return test.FAIL("Source {} and Flow {} 'format' does not match"
                                         .format(source["id"], flow["id"]))
                if len(flow_response.json()) > 0:
                    return test.PASS()
            except json.JSONDecodeError:
                return test.FAIL("Non-JSON response returned from Node API")
            except KeyError:
                return test.FAIL("No Source found for one or more advertised Flows")

        return test.UNCLEAR("No Source or Flow resources were found on the Node")

    def test_27_1(self, test):
        """Node API implements BCP-004-01 Receiver Capabilities"""

        api = self.apis[RECEIVER_CAPS_KEY]
        reg_api = self.apis[CAPS_REGISTER_KEY]

        receivers_valid, receivers_response = self.do_request("GET", self.node_url + "receivers")

        schema = load_resolved_schema(api["spec_path"], "receiver_constraint_sets.json")
        # workaround to load the Capabilities register schema as if with load_resolved_schema directly
        # but with the base_uri of the Receiver Capabilities schemas
        reg_schema_file = str(Path(os.path.abspath(reg_api["spec_path"])) / "capabilities/constraint_set.json")
        with open(reg_schema_file, "r") as f:
            reg_schema_obj = json.load(f)
        reg_schema = load_resolved_schema(api["spec_path"], schema_obj=reg_schema_obj)

        no_receivers = True
        no_constraint_sets = True
        if receivers_valid and receivers_response.status_code == 200:
            try:
                for receiver in receivers_response.json():
                    no_receivers = False
                    if "constraint_sets" in receiver["caps"]:
                        no_constraint_sets = False
                        try:
                            self.validate_schema(receiver, schema)
                        except ValidationError as e:
                            return test.FAIL("Receiver {} does not comply with the BCP-004-01 schema: "
                                             "{}".format(receiver["id"], str(e)),
                                             "https://specs.amwa.tv/bcp-004-01/branches/{}"
                                             "/docs/Receiver_Capabilities.html"
                                             "#validating-parameter-constraints-and-constraint-sets"
                                             .format(api["spec_branch"]))
                        for constraint_set in receiver["caps"]["constraint_sets"]:
                            try:
                                self.validate_schema(constraint_set, reg_schema)
                            except ValidationError as e:
                                return test.FAIL("Receiver {} does not comply with the Capabilities register schema: "
                                                 "{}".format(receiver["id"], str(e)),
                                                 "https://specs.amwa.tv/bcp-004-01/branches/{}"
                                                 "/docs/Receiver_Capabilities.html"
                                                 "#behaviour-receivers"
                                                 .format(api["spec_branch"]))
                            found_param_constraint = False
                            for param_constraint in constraint_set:
                                if not param_constraint.startswith("urn:x-nmos:cap:meta:"):
                                    found_param_constraint = True
                                    break
                            if not found_param_constraint:
                                return test.FAIL("Receiver {} caps includes a constraint set without any "
                                                 "parameter constraints".format(receiver["id"]),
                                                 "https://specs.amwa.tv/bcp-004-01/branches/{}"
                                                 "/docs/Receiver_Capabilities.html"
                                                 "#constraint-sets"
                                                 .format(api["spec_branch"]))
            except json.JSONDecodeError:
                return test.FAIL("Non-JSON response returned from Node API")
            except KeyError as e:
                return test.FAIL("Unable to find expected key in the Receiver: {}".format(e))

        if no_receivers:
            return test.UNCLEAR("No Receivers were found on the Node")
        elif no_constraint_sets:
            return test.OPTIONAL("No BCP-004-01 'constraint_sets' were identified in Receiver caps",
                                 "https://specs.amwa.tv/bcp-004-01/branches/{}"
                                 "/docs/Receiver_Capabilities.html#listing-constraint-sets"
                                 .format(api["spec_branch"]))
        else:
            return test.PASS()

    def test_27_2(self, test):
        """Receiver 'caps' version is valid"""

        api = self.apis[RECEIVER_CAPS_KEY]

        receivers_valid, receivers_response = self.do_request("GET", self.node_url + "receivers")

        no_receivers = True
        no_caps_version = True
        if receivers_valid and receivers_response.status_code == 200:
            try:
                for receiver in receivers_response.json():
                    no_receivers = False
                    if "version" in receiver["caps"]:
                        no_caps_version = False
                        caps_version = receiver["caps"]["version"]
                        core_version = receiver["version"]
                        if self.is04_utils.compare_resource_version(caps_version, core_version) > 0:
                            return test.FAIL("Receiver {} caps version is later than resource version"
                                             .format(receiver["id"]),
                                             "https://specs.amwa.tv/bcp-004-01/branches/{}"
                                             "/docs/Receiver_Capabilities.html#behaviour-receivers"
                                             .format(api["spec_branch"]))
            except json.JSONDecodeError:
                return test.FAIL("Non-JSON response returned from Node API")
            except KeyError as e:
                return test.FAIL("Unable to find expected key in the Receiver: {}".format(e))

        if no_receivers:
            return test.UNCLEAR("No Receivers were found on the Node")
        elif no_caps_version:
            return test.OPTIONAL("No Receiver caps versions were found",
                                 "https://specs.amwa.tv/bcp-004-01/branches/{}"
                                 "/docs/Receiver_Capabilities.html#capabilities-version"
                                 .format(api["spec_branch"]))
        else:
            return test.PASS()

    def test_27_3(self, test):
        """Receiver 'caps' parameter constraints should be listed in the Capabilities register"""

        api = self.apis[RECEIVER_CAPS_KEY]
        reg_api = self.apis[CAPS_REGISTER_KEY]

        # load the Capabilities register schema as JSON as we're only interested in the list of properties
        reg_schema_file = str(Path(os.path.abspath(reg_api["spec_path"])) / "capabilities/constraint_set.json")
        with open(reg_schema_file, "r") as f:
            reg_schema_obj = json.load(f)

        receivers_valid, receivers_response = self.do_request("GET", self.node_url + "receivers")

        no_receivers = True
        no_constraint_sets = True
        warn_unregistered = ""
        if receivers_valid and receivers_response.status_code == 200:
            try:
                for receiver in receivers_response.json():
                    no_receivers = False
                    if "constraint_sets" in receiver["caps"]:
                        no_constraint_sets = False
                        for constraint_set in receiver["caps"]["constraint_sets"]:
                            # keys in each constraint set must be either parameter constraints
                            # or constraint set metadata, both of which are listed in the schema
                            for param_constraint in constraint_set:
                                if param_constraint not in reg_schema_obj["properties"] and not warn_unregistered:
                                    warn_unregistered = "Receiver {} caps includes an unregistered " \
                                        "parameter constraint '{}'".format(receiver["id"], param_constraint)
            except json.JSONDecodeError:
                return test.FAIL("Non-JSON response returned from Node API")
            except KeyError as e:
                return test.FAIL("Unable to find expected key in the Receiver: {}".format(e))

        if no_receivers:
            return test.UNCLEAR("No Receivers were found on the Node")
        elif no_constraint_sets:
            return test.OPTIONAL("No BCP-004-01 'constraint_sets' were identified in Receiver caps",
                                 "https://specs.amwa.tv/bcp-004-01/branches/{}"
                                 "/docs/Receiver_Capabilities.html#listing-constraint-sets"
                                 .format(api["spec_branch"]))
        elif warn_unregistered:
            return test.WARNING(warn_unregistered,
                                "https://specs.amwa.tv/bcp-004-01/branches/{}"
                                "/docs/Receiver_Capabilities.html#defining-parameter-constraints"
                                .format(api["spec_branch"]))
        else:
            return test.PASS()

    def test_27_4(self, test):
        """Node API implements BCP-004-01 Receiver Capabilities constraint set labels"""
        return self.do_test_constraint_set_meta(test, "label", "human-readable labels", warn_not_all=True)

    def test_27_5(self, test):
        """Node API implements BCP-004-01 Receiver Capabilities constraint set preferences"""
        return self.do_test_constraint_set_meta(test, "preference", "preferences")

    def test_27_6(self, test):
        """Node API implements BCP-004-01 Receiver Capabilities enabled/disabled constraint sets"""
        return self.do_test_constraint_set_meta(test, "enabled", "enabled/disabled flags")

    def do_test_constraint_set_meta(self, test, meta, description, warn_not_all=False):
        api = self.apis[RECEIVER_CAPS_KEY]

        receivers_valid, receivers_response = self.do_request("GET", self.node_url + "receivers")

        no_receivers = True
        no_constraint_sets = True
        no_meta = True
        all_meta = True
        if receivers_valid and receivers_response.status_code == 200:
            try:
                for receiver in receivers_response.json():
                    no_receivers = False
                    if "constraint_sets" in receiver["caps"]:
                        no_constraint_sets = False
                        for constraint_set in receiver["caps"]["constraint_sets"]:
                            if "urn:x-nmos:cap:meta:" + meta in constraint_set:
                                no_meta = False
                            else:
                                all_meta = False
            except json.JSONDecodeError:
                return test.FAIL("Non-JSON response returned from Node API")
            except KeyError as e:
                return test.FAIL("Unable to find expected key in the Receiver: {}".format(e))

        if no_receivers:
            return test.UNCLEAR("No Receivers were found on the Node")
        elif no_constraint_sets:
            return test.OPTIONAL("No BCP-004-01 'constraint_sets' were identified in Receiver caps",
                                 "https://specs.amwa.tv/bcp-004-01/branches/{}"
                                 "/docs/Receiver_Capabilities.html#listing-constraint-sets"
                                 .format(api["spec_branch"]))
        elif no_meta:
            return test.OPTIONAL("No BCP-004-01 'constraint_sets' have {}".format(description),
                                 "https://specs.amwa.tv/bcp-004-01/branches/{}"
                                 "/docs/Receiver_Capabilities.html#constraint-set-{}"
                                 .format(api["spec_branch"], meta))
        elif warn_not_all and not all_meta:
            return test.WARNING("Only some BCP-004-01 'constraint_sets' have {}".format(description),
                                "https://specs.amwa.tv/bcp-004-01/branches/{}"
                                "/docs/Receiver_Capabilities.html#constraint-set-{}"
                                .format(api["spec_branch"], meta))
        else:
            return test.PASS()

    def test_27_7(self, test):
        """Receiver 'caps' parameter constraints should be used with the correct format"""

        # general_constraints = [
        #     "urn:x-nmos:cap:format:media_type",
        #     "urn:x-nmos:cap:format:grain_rate",
        #     "urn:x-nmos:cap:format:bit_rate",
        #     "urn:x-nmos:cap:transport:bit_rate",
        #     "urn:x-nmos:cap:transport:st2110_21_sender_type"
        # ]
        video_specific_constraints = [
            "urn:x-nmos:cap:format:frame_width",
            "urn:x-nmos:cap:format:frame_height",
            "urn:x-nmos:cap:format:interlace_mode",
            "urn:x-nmos:cap:format:colorspace",
            "urn:x-nmos:cap:format:transfer_characteristic",
            "urn:x-nmos:cap:format:color_sampling",
            "urn:x-nmos:cap:format:component_depth",
            "urn:x-nmos:cap:format:profile",
            "urn:x-nmos:cap:format:level",
            "urn:x-nmos:cap:format:sublevel",
            "urn:x-nmos:cap:transport:packet_transmission_mode"
        ]
        audio_specific_constraints = [
            "urn:x-nmos:cap:format:channel_count",
            "urn:x-nmos:cap:format:sample_rate",
            "urn:x-nmos:cap:format:sample_depth",
            "urn:x-nmos:cap:transport:packet_time",
            "urn:x-nmos:cap:transport:max_packet_time"
        ]
        data_specific_constraints = [
            "urn:x-nmos:cap:format:event_type"
        ]
        format_specific_constraints = {
            "urn:x-nmos:format:video": video_specific_constraints,
            "urn:x-nmos:format:audio": audio_specific_constraints,
            "urn:x-nmos:format:data": data_specific_constraints,
            "urn:x-nmos:format:mux": []
        }

        api = self.apis[RECEIVER_CAPS_KEY]

        receivers_valid, receivers_response = self.do_request("GET", self.node_url + "receivers")

        no_receivers = True
        no_constraint_sets = True
        warn_format = ""
        if receivers_valid and receivers_response.status_code == 200:
            try:
                for receiver in receivers_response.json():
                    no_receivers = False
                    if "constraint_sets" in receiver["caps"]:
                        no_constraint_sets = False
                        format = receiver["format"]
                        wrong_constraints = [c for f in format_specific_constraints if f != format
                                             for c in format_specific_constraints[f]]
                        for constraint_set in receiver["caps"]["constraint_sets"]:
                            for param_constraint in constraint_set:
                                if param_constraint in wrong_constraints and not warn_format:
                                    warn_format = "Receiver {} caps includes a parameter constraint '{}' " \
                                        "that is not relevant for {}".format(receiver["id"], param_constraint, format)
            except json.JSONDecodeError:
                return test.FAIL("Non-JSON response returned from Node API")
            except KeyError as e:
                return test.FAIL("Unable to find expected key in the Receiver: {}".format(e))

        if no_receivers:
            return test.UNCLEAR("No Receivers were found on the Node")
        elif no_constraint_sets:
            return test.OPTIONAL("No BCP-004-01 'constraint_sets' were identified in Receiver caps",
                                 "https://specs.amwa.tv/bcp-004-01/branches/{}"
                                 "/docs/Receiver_Capabilities.html#listing-constraint-sets"
                                 .format(api["spec_branch"]))
        elif warn_format:
            return test.WARNING(warn_format)
        else:
            return test.PASS()

    def test_27_8(self, test):
        """Receiver 'caps' media type constraints should be used consistently"""

        media_type = "urn:x-nmos:cap:format:media_type"

        api = self.apis[RECEIVER_CAPS_KEY]

        receivers_valid, receivers_response = self.do_request("GET", self.node_url + "receivers")

        no_receivers = True
        no_constraint_sets = True
        if receivers_valid and receivers_response.status_code == 200:
            try:
                for receiver in receivers_response.json():
                    no_receivers = False
                    caps = receiver["caps"]
                    if "media_types" in caps and "constraint_sets" in caps:
                        no_constraint_sets = False
                        media_types = caps["media_types"]
                        for constraint_set in caps["constraint_sets"]:
                            if media_type in constraint_set:
                                if "enum" in constraint_set[media_type]:
                                    if not set(constraint_set[media_type]["enum"]).issubset(set(media_types)):
                                        return test.FAIL("Receiver {} caps includes a value for the parameter "
                                                         "constraint '{}' that is excluded by 'media_types'"
                                                         .format(receiver["id"], media_type))
            except json.JSONDecodeError:
                return test.FAIL("Non-JSON response returned from Node API")
            except KeyError as e:
                return test.FAIL("Unable to find expected key in the Receiver: {}".format(e))

        if no_receivers:
            return test.UNCLEAR("No Receivers were found on the Node")
        elif no_constraint_sets:
            return test.OPTIONAL("No BCP-004-01 'constraint_sets' were identified in Receiver caps",
                                 "https://specs.amwa.tv/bcp-004-01/branches/{}"
                                 "/docs/Receiver_Capabilities.html#listing-constraint-sets"
                                 .format(api["spec_branch"]))
        else:
            return test.PASS()

    def test_28(self, test):
        """Node and Device resources correctly use BCP-002-02 distinguishing information"""

        api = self.apis[ASSET_KEY]

        manufacturer = "urn:x-nmos:tag:asset:manufacturer/v1.0"
        product = "urn:x-nmos:tag:asset:product/v1.0"
        instance_id = "urn:x-nmos:tag:asset:instance-id/v1.0"
        function = "urn:x-nmos:tag:asset:function/v1.0"
        res_tags = {
            "node": [manufacturer, product, instance_id],
            "device": [manufacturer, product, instance_id, function]
        }

        self.do_node_basics_prereqs()

        not_implemented = True
        missing_tag = None
        uniques = set()

        for res_type in ["node", "device"]:
            try:
                node_resources = self.get_node_resources(res_type)

                if not node_resources:
                    return test.UNCLEAR("No {} resources were found on the Node.".format(res_type.title()))

                for res_id, resource in node_resources.items():
                    tags = resource["tags"]
                    for tag in res_tags[res_type]:
                        if tag in tags:
                            not_implemented = False
                            if len(tags[tag]) == 0 or (tag != function and len(tags[tag]) > 1):
                                return test.FAIL("{} {} has {} '{}' tag values."
                                                 .format(res_type.title(), res_id, len(tags[tag]), tag))
                            if any([len(value) == 0 for value in tags[tag]]):
                                return test.FAIL("{} {} has an empty '{}' tag value."
                                                 .format(res_type.title(), res_id, tag))
                        elif not missing_tag:
                            missing_tag = "{} {} has no '{}' tag.".format(res_type.title(), res_id, tag)
                    unique = (
                        res_type,
                        tags.get(manufacturer, [None])[0],
                        tags.get(product, [None])[0],
                        tags.get(instance_id, [None])[0]
                    )
                    if unique in uniques:
                        return test.FAIL("{} {} does not have unique asset tags.".format(res_type.title(), res_id))
                    uniques.add(unique)

            except ValueError:
                return test.FAIL("Failed to reach Node API or invalid JSON received!")
            except KeyError as e:
                return test.FAIL("Unable to find expected key in the {} {}: {}".format(res_type.title(), res_id, e))

        if not_implemented:
            return test.OPTIONAL("No BCP-002-02 asset tags were present on the Node or Devices",
                                 "https://specs.amwa.tv/bcp-002-02/branches/{}"
                                 "/docs/Overview.html"
                                 .format(api["spec_branch"]))
        elif missing_tag:
            return test.FAIL(missing_tag)
        else:
            return test.PASS()

    def do_receiver_put(self, test, receiver_id, data):
        """Perform a PUT to the Receiver 'target' resource with the specified data"""

        valid, put_response = self.do_request("PUT", self.node_url + "receivers/" + receiver_id + "/target", json=data)
        if not valid:
            raise NMOSTestException(test.FAIL("Unexpected response from the Node API: {}".format(put_response)))

        if put_response.status_code == 501:
            api = self.apis[NODE_API_KEY]
            if self.is04_utils.compare_api_version(api["version"], "v1.3") >= 0:
                raise NMOSTestException(test.OPTIONAL("Node indicated that basic connection management is not "
                                                      "supported",
                                                      NMOS_WIKI_URL + "/IS-04#nodes-basic-connection-management"))
            else:
                raise NMOSTestException(test.WARNING("501 'Not Implemented' status code is not supported below API "
                                                     "version v1.3",
                                                     NMOS_WIKI_URL + "/IS-04#nodes-basic-connection-management"))
        elif put_response.status_code != 202:
            raise NMOSTestException(test.FAIL("Receiver target PUT did not produce a 202 (or 501) response code: "
                                              "{}. Please ensure SDP_PREFERENCES match the node under test."
                                              .format(put_response.status_code)))

        schema = self.get_schema(NODE_API_KEY, "PUT", "/receivers/{receiverId}/target", put_response.status_code)
        valid, message = self.check_response(schema, "PUT", put_response)
        if valid:
            # if message:
            #     return WARNING somehow...
            pass
        else:
            raise NMOSTestException(test.FAIL(message))

    def collect_mdns_announcements(self):
        """Helper function to collect Node mDNS announcements in the presence of a Registration API"""

        registry_info = self._registry_mdns_info(self.primary_registry.get_data().port, 0)

        # Reset the registry to clear previous data, although we won't be checking it
        self.primary_registry.reset()
        self.primary_registry.enable()

        if CONFIG.DNS_SD_MODE == "multicast":
            # Advertise a registry at pri 0 and allow the Node to do a basic registration
            # self.zc.register_service(registry_info, strict=self._strict_service_name(registry_info))
            self.zc.register_service(registry_info)

        # Wait for n seconds after advertising the service for the first POST from a Node
        self.primary_registry.wait_for_registration(CONFIG.DNS_SD_ADVERT_TIMEOUT)

        ServiceBrowser(self.zc, "_nmos-node._tcp.local.", self.zc_listener)
        time.sleep(CONFIG.DNS_SD_BROWSE_TIMEOUT)
        node_list = self.zc_listener.get_service_list()

        # Withdraw the registry advertisement now we've performed a browse for Node advertisements
        if CONFIG.DNS_SD_MODE == "multicast":
            self.zc.unregister_service(registry_info)
        self.primary_registry.disable()

        return node_list
