# Microsoft Azure Linux Agent
#
# Copyright 2020 Microsoft 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.
#
# Requires Python 2.6+ and Openssl 1.0+
import json
import sys

from azurelinuxagent.common import logger
from azurelinuxagent.common.AgentGlobals import AgentGlobals
from azurelinuxagent.common.event import WALAEventOperation, add_event
from azurelinuxagent.common.future import ustr, urlparse, datetime_min_utc
from azurelinuxagent.common.protocol.extensions_goal_state import ExtensionsGoalState, GoalStateChannel, VmSettingsParseError
from azurelinuxagent.common.protocol.restapi import VMAgentFamily, Extension, ExtensionRequestedState, ExtensionSettings
from azurelinuxagent.common.utils import timeutil
from azurelinuxagent.common.utils.flexible_version import FlexibleVersion

# The 'encodedSignature' property is only supported on newer versions of HGAP.
_MIN_HGAP_VERSION_FOR_EXT_SIGNATURE = FlexibleVersion("1.0.8.159")

class ExtensionsGoalStateFromVmSettings(ExtensionsGoalState):
    def __init__(self, etag, json_text, correlation_id):
        super(ExtensionsGoalStateFromVmSettings, self).__init__()
        self._id = "etag_{0}".format(etag)
        self._etag = etag
        self._svd_sequence_number = 0
        self._hostga_plugin_correlation_id = correlation_id
        self._text = json_text
        self._host_ga_plugin_version = FlexibleVersion('0.0.0.0')
        self._schema_version = FlexibleVersion('0.0.0.0')
        self._activity_id = AgentGlobals.GUID_ZERO
        self._correlation_id = AgentGlobals.GUID_ZERO
        self._created_on_timestamp = timeutil.create_utc_timestamp(datetime_min_utc)
        self._source = None
        self._status_upload_blob = None
        self._status_upload_blob_type = None
        self._required_features = []
        self._on_hold = False
        self._agent_families = []
        self._extensions = []

        try:
            self._parse_vm_settings(json_text)
            self._do_common_validations()
        except Exception as e:
            message = "Error parsing vmSettings [HGAP: {0} Etag:{1}]: {2}".format(self._host_ga_plugin_version, etag, ustr(e))
            raise VmSettingsParseError(message, etag, self.get_redacted_text())

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

    @property
    def etag(self):
        return self._etag

    @property
    def svd_sequence_number(self):
        return self._svd_sequence_number

    @property
    def host_ga_plugin_version(self):
        return self._host_ga_plugin_version

    @property
    def schema_version(self):
        return self._schema_version

    @property
    def activity_id(self):
        """
        The CRP activity id
        """
        return self._activity_id

    @property
    def correlation_id(self):
        """
        The correlation id for the CRP operation
        """
        return self._correlation_id

    @property
    def hostga_plugin_correlation_id(self):
        """
        The correlation id for the call to the HostGAPlugin vmSettings API
        """
        return self._hostga_plugin_correlation_id

    @property
    def created_on_timestamp(self):
        """
        Timestamp assigned by the CRP (time at which the goal state was created)
        """
        return self._created_on_timestamp

    @property
    def channel(self):
        return GoalStateChannel.HostGAPlugin

    @property
    def source(self):
        return self._source

    @property
    def status_upload_blob(self):
        return self._status_upload_blob

    @property
    def status_upload_blob_type(self):
        return self._status_upload_blob_type

    def _set_status_upload_blob_type(self, value):
        self._status_upload_blob_type = value

    @property
    def required_features(self):
        return self._required_features

    @property
    def on_hold(self):
        return self._on_hold

    @property
    def agent_families(self):
        return self._agent_families

    @property
    def extensions(self):
        return self._extensions

    def get_redacted_text(self):
        try:
            text = self._text

            if self.status_upload_blob is not None:
                parsed = urlparse(self.status_upload_blob)
                original = text
                text = text.replace(parsed.query, "***REDACTED***")
                if text == original:
                    raise Exception('Could not redact the status upload blob')

            for ext_handler in self._extensions:
                for extension in ext_handler.settings:
                    if extension.protectedSettings is not None:
                        original = text
                        text = text.replace(extension.protectedSettings, "***REDACTED***")
                        if text == original:
                            return 'Could not redact protectedSettings for {0}'.format(extension.name)

            return text
        except Exception as e:
            return "Error redacting text: {0}".format(e)

    def _parse_vm_settings(self, json_text):
        vm_settings = _CaseFoldedDict.from_dict(json.loads(json_text))
        self._parse_simple_attributes(vm_settings)
        self._parse_status_upload_blob(vm_settings)
        self._parse_required_features(vm_settings)
        self._parse_agent_manifests(vm_settings)
        self._parse_extensions(vm_settings)

    def _parse_simple_attributes(self, vm_settings):
        # Sample:
        #     {
        #         "hostGAPluginVersion": "1.0.8.115",
        #         "vmSettingsSchemaVersion": "0.0",
        #         "activityId": "a33f6f53-43d6-4625-b322-1a39651a00c9",
        #         "correlationId": "9a47a2a2-e740-4bfc-b11b-4f2f7cfe7d2e",
        #         "inSvdSeqNo": 1,
        #         "extensionsLastModifiedTickCount": 637726657706205217,
        #         "extensionGoalStatesSource": "FastTrack",
        #         ...
        #     }

        # The HGAP version is included in some messages, so parse it first
        host_ga_plugin_version = vm_settings.get("hostGAPluginVersion")
        if host_ga_plugin_version is not None:
            self._host_ga_plugin_version = FlexibleVersion(host_ga_plugin_version)

        self._activity_id = self._string_to_id(vm_settings.get("activityId"))
        self._correlation_id = self._string_to_id(vm_settings.get("correlationId"))
        self._svd_sequence_number = self._string_to_id(vm_settings.get("inSvdSeqNo"))
        self._created_on_timestamp = self._ticks_to_utc_timestamp(vm_settings.get("extensionsLastModifiedTickCount"))

        schema_version = vm_settings.get("vmSettingsSchemaVersion")
        if schema_version is not None:
            self._schema_version = FlexibleVersion(schema_version)

        on_hold = vm_settings.get("onHold")
        if on_hold is not None:
            self._on_hold = on_hold

        self._source = vm_settings.get("extensionGoalStatesSource")
        if self._source is None:
            self._source = "UNKNOWN"

    def _parse_status_upload_blob(self, vm_settings):
        # Sample:
        # {
        #     ...
        #     "statusUploadBlob": {
        #         "statusBlobType": "BlockBlob",
        #         "value": "https://dcrcl3a0xs.blob.core.windows.net/$system/edp0plkw2b.86f4ae0a-61f8-48ae-9199-40f402d56864.status?sv=2018-03-28&sr=b&sk=system-1&sig=KNWgC2%3d&se=9999-01-01T00%3a00%3a00Z&sp=w"
        #     },
        #     ...
        # }
        status_upload_blob = vm_settings.get("statusUploadBlob")
        if status_upload_blob is None:
            self._status_upload_blob = None
            self._status_upload_blob_type = "BlockBlob"
        else:
            self._status_upload_blob = status_upload_blob.get("value")
            if self._status_upload_blob is None:
                raise Exception("Missing statusUploadBlob.value")
            self._status_upload_blob_type = status_upload_blob.get("statusBlobType")
            if self._status_upload_blob_type is None:
                self._status_upload_blob_type = "BlockBlob"

    def _parse_required_features(self, vm_settings):
        # Sample:
        # {
        #     ...
        #     "requiredFeatures": [
        #         {
        #             "name": "MultipleExtensionsPerHandler"
        #         }
        #     ],
        #     ...
        # }
        required_features = vm_settings.get("requiredFeatures")
        if required_features is not None:
            if not isinstance(required_features, list):
                raise Exception("requiredFeatures should be an array (got {0})".format(required_features))

            def get_required_features_names():
                for feature in required_features:
                    name = feature.get("name")
                    if name is None:
                        raise Exception("A required feature is missing the 'name' property (got {0})".format(feature))
                    yield name

            self._required_features.extend(get_required_features_names())

    def _parse_agent_manifests(self, vm_settings):
        # Sample:
        # {
        #     ...
        #     "gaFamilies": [
        #         {
        #             "name": "Prod",
        #             "version": "9.9.9.9",
        #             "from_version": "9.9.9.9",
        #             "isVersionFromRSM": true,
        #             "isVMEnabledForRSMUpgrades": true,
        #             "uris": [
        #                 "https://zrdfepirv2cdm03prdstr01a.blob.core.windows.net/7d89d439b79f4452950452399add2c90/Microsoft.OSTCLinuxAgent_Prod_uscentraleuap_manifest.xml",
        #                 "https://ardfepirv2cdm03prdstr01a.blob.core.windows.net/7d89d439b79f4452950452399add2c90/Microsoft.OSTCLinuxAgent_Prod_uscentraleuap_manifest.xml"
        #             ]
        #         },
        #         {
        #             "name": "Test",
        #             "uris": [
        #                 "https://zrdfepirv2cdm03prdstr01a.blob.core.windows.net/7d89d439b79f4452950452399add2c90/Microsoft.OSTCLinuxAgent_Test_uscentraleuap_manifest.xml",
        #                 "https://ardfepirv2cdm03prdstr01a.blob.core.windows.net/7d89d439b79f4452950452399add2c90/Microsoft.OSTCLinuxAgent_Test_uscentraleuap_manifest.xml"
        #             ]
        #         }
        #     ],
        #     ...
        # }
        families = vm_settings.get("gaFamilies")
        if families is None:
            return
        if not isinstance(families, list):
            raise Exception("gaFamilies should be an array (got {0})".format(families))

        for family in families:
            name = family["name"]
            version = family.get("version")
            from_version = family.get("fromVersion")
            is_version_from_rsm = family.get("isVersionFromRSM")
            is_vm_enabled_for_rsm_upgrades = family.get("isVMEnabledForRSMUpgrades")
            uris = family.get("uris")
            if uris is None:
                uris = []
            agent_family = VMAgentFamily(name)
            agent_family.version = version
            agent_family.from_version = from_version
            agent_family.is_version_from_rsm = is_version_from_rsm
            agent_family.is_vm_enabled_for_rsm_upgrades = is_vm_enabled_for_rsm_upgrades
            for u in uris:
                agent_family.uris.append(u)
            self._agent_families.append(agent_family)

    def _parse_extensions(self, vm_settings):
        # Sample (NOTE: The first sample is single-config, the second multi-config):
        # {
        #     ...
        #     "extensionGoalStates": [
        #         {
        #             "name": "Microsoft.Azure.Monitor.AzureMonitorLinuxAgent",
        #             "version": "1.9.1",
        #             "location": "https://zrdfepirv2cbn04prdstr01a.blob.core.windows.net/a47f0806d764480a8d989d009c75007d/Microsoft.Azure.Monitor_AzureMonitorLinuxAgent_useast2euap_manifest.xml",
        #             "state": "enabled",
        #             "autoUpgrade": true,
        #             "runAsStartupTask": false,
        #             "isJson": true,
        #             "useExactVersion": true,
        #             "encodedSignature": "MIIn...",
        #             "settingsSeqNo": 0,
        #             "settings": [
        #                 {
        #                     "protectedSettingsCertThumbprint": "BD447EF71C3ADDF7C837E84D630F3FAC22CCD22F",
        #                     "protectedSettings": "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",
        #                     "publicSettings": "{\"GCS_AUTO_CONFIG\":true}"
        #                 }
        #             ],
        #             "dependsOn": [
        #                 ...
        #             ]
        #         },
        #         {
        #             "name": "Microsoft.CPlat.Core.RunCommandHandlerLinux",
        #             "version": "1.2.0",
        #             "location": "https://umsavbvncrpzbnxmxzmr.blob.core.windows.net/f4086d41-69f9-3103-78e0-8a2c7e789d0f/f4086d41-69f9-3103-78e0-8a2c7e789d0f_manifest.xml",
        #             "failoverlocation": "https://umsajbjtqrb3zqjvgb2z.blob.core.windows.net/f4086d41-69f9-3103-78e0-8a2c7e789d0f/f4086d41-69f9-3103-78e0-8a2c7e789d0f_manifest.xml",
        #             "additionalLocations": [
        #                 "https://umsawqtlsshtn5v2nfgh.blob.core.windows.net/f4086d41-69f9-3103-78e0-8a2c7e789d0f/f4086d41-69f9-3103-78e0-8a2c7e789d0f_manifest.xml"
        #             ],
        #             "state": "enabled",
        #             "autoUpgrade": true,
        #             "runAsStartupTask": false,
        #             "isJson": true,
        #             "useExactVersion": true,
        #             "settingsSeqNo": 0,
        #             "isMultiConfig": true,
        #             "settings": [
        #                 {
        #                     "publicSettings": "{\"source\":{\"script\":\"echo '4abb1e88-f349-41f8-8442-247d9fdfcac5'\"}}",
        #                     "seqNo": 0,
        #                     "extensionName": "MCExt1",
        #                     "extensionState": "enabled"
        #                 },
        #                 {
        #                     "publicSettings": "{\"source\":{\"script\":\"echo 'e865c9bc-a7b3-42c6-9a79-cfa98a1ee8b3'\"}}",
        #                     "seqNo": 0,
        #                     "extensionName": "MCExt2",
        #                     "extensionState": "enabled"
        #                 },
        #                 {
        #                     "publicSettings": "{\"source\":{\"script\":\"echo 'f923e416-0340-485c-9243-8b84fb9930c6'\"}}",
        #                     "seqNo": 0,
        #                     "extensionName": "MCExt3",
        #                     "extensionState": "enabled"
        #                 }
        #             ],
        #             "dependsOn": [
        #                 ...
        #            ]
        #         }
        #         ...
        #     ]
        #     ...
        # }
        extension_goal_states = vm_settings.get("extensionGoalStates")
        if extension_goal_states is not None:
            if not isinstance(extension_goal_states, list):
                raise Exception("extension_goal_states should be an array (got {0})".format(type(extension_goal_states)))  # report only the type, since the value may contain secrets
            for extension_gs in extension_goal_states:
                extension = Extension()

                extension.name = extension_gs['name']
                extension.version = extension_gs['version']
                extension.state = extension_gs['state']
                # The 'encodedSignature' property is optional. If absent, it may mean the VmSettings API does not support
                # it, or the extension is not signed. In either case, we set extension.encoded_signature to an empty string.
                encoded_signature = extension_gs.get('encodedSignature')
                extension.encoded_signature = "" if encoded_signature is None else encoded_signature

                if extension.state not in ExtensionRequestedState.All:
                    raise Exception('Invalid extension state: {0} ({1})'.format(extension.state, extension.name))
                is_multi_config = extension_gs.get('isMultiConfig')
                if is_multi_config is not None:
                    extension.supports_multi_config = is_multi_config
                location = extension_gs.get('location')
                if location is not None:
                    extension.manifest_uris.append(location)
                fail_over_location = extension_gs.get('failoverLocation')
                if fail_over_location is not None:
                    extension.manifest_uris.append(fail_over_location)
                additional_locations = extension_gs.get('additionalLocations')
                if additional_locations is not None:
                    if not isinstance(additional_locations, list):
                        raise Exception('additionalLocations should be an array (got {0})'.format(additional_locations))
                    extension.manifest_uris.extend(additional_locations)

                #
                # Settings
                #
                settings_list = extension_gs.get('settings')
                if settings_list is not None:
                    if not isinstance(settings_list, list):
                        raise Exception("'settings' should be an array (extension: {0})".format(extension.name))
                    if not extension.supports_multi_config and len(settings_list) > 1:
                        raise Exception("Single-config extension includes multiple settings (extension: {0})".format(extension.name))

                    for s in settings_list:
                        settings = ExtensionSettings()
                        public_settings = s.get('publicSettings')
                        # Note that publicSettings, protectedSettings and protectedSettingsCertThumbprint can be None; do not change this to, for example,
                        # empty, since those values are serialized to the extension's status file and extensions may depend on the current implementation
                        # (for example, no public settings would currently be serialized as '"publicSettings": null')
                        settings.publicSettings = None if public_settings is None else json.loads(public_settings)
                        settings.protectedSettings = s.get('protectedSettings')
                        thumbprint = s.get('protectedSettingsCertThumbprint')
                        if thumbprint is None and settings.protectedSettings is not None:
                            raise Exception("The certificate thumbprint for protected settings is missing (extension: {0})".format(extension.name))
                        settings.certificateThumbprint = thumbprint

                        # in multi-config each settings have their own name, sequence number and state
                        if extension.supports_multi_config:
                            settings.name = s['extensionName']
                            settings.sequenceNumber = s['seqNo']
                            settings.state = s['extensionState']
                        else:
                            settings.name = extension.name
                            settings.sequenceNumber = extension_gs['settingsSeqNo']
                            settings.state = extension.state
                        extension.settings.append(settings)

                #
                # Dependency level
                #
                depends_on = extension_gs.get("dependsOn")
                if depends_on is not None:
                    self._parse_dependency_level(depends_on, extension)

                self._extensions.append(extension)


    @staticmethod
    def _parse_dependency_level(depends_on, extension):
        # Sample (NOTE: The first sample is single-config, the second multi-config):
        # {
        #     ...
        #     "extensionGoalStates": [
        #         {
        #             "name": "Microsoft.Azure.Monitor.AzureMonitorLinuxAgent",
        #             ...
        #             "settings": [
        #                 ...
        #             ],
        #             "dependsOn": [
        #                 {
        #                     "DependsOnExtension": [
        #                         {
        #                             "handler": "Microsoft.Azure.Security.Monitoring.AzureSecurityLinuxAgent"
        #                         }
        #                     ],
        #                     "dependencyLevel": 1
        #                 }
        #             ]
        #         },
        #         {
        #             "name": "Microsoft.CPlat.Core.RunCommandHandlerLinux",
        #             ...
        #             "isMultiConfig": true,
        #             "settings": [
        #                 {
        #                     ...
        #                     "extensionName": "MCExt1",
        #                 },
        #                 {
        #                     ...
        #                     "extensionName": "MCExt2",
        #                 },
        #                 {
        #                     ...
        #                     "extensionName": "MCExt3",
        #                 }
        #             ],
        #             "dependsOn": [
        #                 {
        #                     "dependsOnExtension": [
        #                         {
        #                             "extension": "...",
        #                             "handler": "..."
        #                         },
        #                         {
        #                             "extension": "...",
        #                             "handler": "..."
        #                         }
        #                     ],
        #                     "dependencyLevel": 2,
        #                     "name": "MCExt1"
        #                 },
        #                 {
        #                     "dependsOnExtension": [
        #                         {
        #                             "extension": "...",
        #                             "handler": "..."
        #                         }
        #                     ],
        #                     "dependencyLevel": 1,
        #                     "name": "MCExt2"
        #                 }
        #                 ...
        #             ]
        #     ...
        # }
        if not isinstance(depends_on, list):
            raise Exception('dependsOn should be an array ({0}) (got {1})'.format(extension.name, depends_on))

        if not extension.supports_multi_config:
            # single-config
            length = len(depends_on)
            if length > 1:
                raise Exception('dependsOn should be an array with exactly one item for single-config extensions ({0}) (got {1})'.format(extension.name, depends_on))
            if length == 0:
                logger.warn('dependsOn is an empty array for extension {0}; setting the dependency level to 0'.format(extension.name))
                dependency_level = 0
            else:
                dependency_level = depends_on[0]['dependencyLevel']
                depends_on_extension = depends_on[0].get('dependsOnExtension')
                if depends_on_extension is None:
                    # TODO: Consider removing this check and its telemetry after a few releases if we do not receive any telemetry indicating
                    #       that dependsOnExtension is actually missing from the vmSettings
                    message = 'Missing dependsOnExtension on extension {0}'.format(extension.name)
                    logger.warn(message)
                    add_event(WALAEventOperation.ProvisionAfterExtensions, message=message, is_success=False, log_event=False)
                else:
                    message = '{0} depends on {1}'.format(extension.name, depends_on_extension)
                    logger.info(message)
                    add_event(WALAEventOperation.ProvisionAfterExtensions, message=message, is_success=True, log_event=False)
            if len(extension.settings) == 0:
                message = 'Extension {0} does not have any settings. Will ignore dependency (dependency level: {1})'.format(extension.name, dependency_level)
                logger.warn(message)
                add_event(WALAEventOperation.ProvisionAfterExtensions, message=message, is_success=False, log_event=False)
            else:
                extension.settings[0].dependencyLevel = dependency_level
        else:
            # multi-config
            settings_by_name = {}
            for settings in extension.settings:
                settings_by_name[settings.name] = settings

            for dependency in depends_on:
                settings = settings_by_name.get(dependency["name"])
                if settings is None:
                    raise Exception("Dependency '{0}' does not correspond to any of the settings in the extension (settings: {1})".format(dependency["name"], settings_by_name.keys()))
                settings.dependencyLevel = dependency["dependencyLevel"]

    def supports_encoded_signature(self):
        """
        Returns True if the HGAP version supports the 'encoded_signature' extension property.
        """
        return self._host_ga_plugin_version >= _MIN_HGAP_VERSION_FOR_EXT_SIGNATURE


#
# TODO: The current implementation of the vmSettings API uses inconsistent cases on the names of the json items it returns.
#       To work around that, we use _CaseFoldedDict to query those json items in a case-insensitive matter, Do not use
#       _CaseFoldedDict for other purposes. Remove it once the vmSettings API is updated.
#
class _CaseFoldedDict(dict):
    @staticmethod
    def from_dict(dictionary):
        case_folded = _CaseFoldedDict()
        for key, value in dictionary.items():
            case_folded[key] = _CaseFoldedDict._to_case_folded_dict_item(value)
        return case_folded

    def get(self, key):
        return super(_CaseFoldedDict, self).get(_casefold(key))

    def has_key(self, key):
        return super(_CaseFoldedDict, self).get(_casefold(key))

    def __getitem__(self, key):
        return super(_CaseFoldedDict, self).__getitem__(_casefold(key))

    def __setitem__(self, key, value):
        return super(_CaseFoldedDict, self).__setitem__(_casefold(key), value)

    def __contains__(self, key):
        return  super(_CaseFoldedDict, self).__contains__(_casefold(key))

    @staticmethod
    def _to_case_folded_dict_item(item):
        if isinstance(item, dict):
            case_folded_dict = _CaseFoldedDict()
            for key, value in item.items():
                case_folded_dict[_casefold(key)] = _CaseFoldedDict._to_case_folded_dict_item(value)
            return case_folded_dict
        if isinstance(item, list):
            return [_CaseFoldedDict._to_case_folded_dict_item(list_item) for list_item in item]
        return item

    def copy(self):
        raise NotImplementedError()

    @staticmethod
    def fromkeys(*args, **kwargs):
        raise NotImplementedError()

    def pop(self, key, default=None):
        raise NotImplementedError()

    def setdefault(self, key, default=None):
        raise NotImplementedError()

    def update(self, E=None, **F):  # known special case of dict.update
        raise NotImplementedError()

    def __delitem__(self, *args, **kwargs):
        raise NotImplementedError()


# casefold() does not exist on Python 2 so we use lower() there
def _casefold(string):
    if sys.version_info[0] == 2:
        return type(string).lower(string)  # the type of "string" can be unicode or str
    # Class 'str' has no 'casefold' member (no-member) -- Disabled: This warning shows up on Python 2.7 pylint runs
    # but this code is actually not executed on Python 2.
    return str.casefold(string)  # pylint: disable=no-member





