"""
Copyright 2020 The Magma Authors.

This source code is licensed under the BSD-style license found in the
LICENSE file in the root directory of this source tree.

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.
"""

from logger import EnodebdLogger as logger
from state_machines.enb_acs_manager import StateMachineManager
from spyne.decorator import rpc
from spyne.model.complex import ComplexModelBase
from spyne.server.wsgi import WsgiMethodContext
from spyne.service import ServiceBase

from . import models

# Allow methods without 'self' as first input. Required by spyne
# pylint: disable=no-self-argument

# RPC methods supported by ACS
RPC_METHODS = ['Inform', 'GetRPCMethods', 'TransferComplete']
RPC_RESPONSES = [method + 'Response' for method in RPC_METHODS]
# RPC methods supported by CPE
CPE_RPC_METHODS = [
    'SetParameterValues',
    'GetParameterValues',
    'GetParameterNames',
    'SetParameterAttributes',
    'GetParameterAttributes',
    'AddObject',
    'DeleteObject',
    'Download',
    'Reboot',
]
CPE_RPC_RESPONSES = [method + 'Response' for method in CPE_RPC_METHODS]
# ACS RPC methods that are not explicitly described by the spec (hence shouldn't
# be advertised by GetRPCMethods). Note: No responses for these
PSEUDO_RPC_METHODS = ['Fault']
# Top-level CWMP header elements. Namespaces should be preserved on these (since
# they are not within other CWMP elements)
TOP_LEVEL_HEADER_ELEMENTS = ['ID', 'HoldRequests']


def fill_response_header(ctx):
    """ Echo message ID from input header to output header, when responding to
        CPE->ACS RPC calls """
    ctx.out_header = models.ID(mustUnderstand='1')
    ctx.out_header.Data = ctx.in_header.Data


class AutoConfigServer(ServiceBase):
    """ TR-069 ACS implementation. The TR-069/CWMP RPC messages are defined, as
        per cwmp-1-0.xsd schema definition, in the RPC decorators below. These
        RPC methods are intended to be called by TR-069-compliant customer
        premesis equipment (CPE), over the SOAP/HTTP interface defined by
        TR-069.

        Per spyne documentation, this class is never instantiated, so all RPC
        functions are implicitly staticmethods. Hence use static class variables
        to hold state.
        This also means that only a single thread can be used (since there are
        no locks).
        Note that staticmethod decorator can't be used in conjunction with rpc
        decorator.
    """
    __out_header__ = models.ID
    __in_header__ = models.ID
    _acs_to_cpe_queue = None
    _cpe_to_acs_queue = None

    """ Set maxEnvelopes to 1, as per TR-069 spec """
    _max_envelopes = 1

    @classmethod
    def set_state_machine_manager(
        cls,
        state_machine_manager: StateMachineManager,
    ) -> None:
        cls.state_machine_manager = state_machine_manager

    @classmethod
    def _handle_tr069_message(
        cls,
        ctx: WsgiMethodContext,
        message: ComplexModelBase,
    ) -> ComplexModelBase:
        # Log incoming msg
        if hasattr(message, 'as_dict'):
            logger.debug('Handling TR069 message: %s', str(type(message)))
        else:
            logger.debug('Handling TR069 message.')

        req = cls._get_tr069_response_from_sm(ctx, message)

        # Log outgoing msg
        if hasattr(req, 'as_dict'):
            logger.debug('Sending TR069 message: %s', str(req.as_dict()))
        else:
            logger.debug('Sending TR069 message.')

        # Set header
        ctx.out_header = models.ID(mustUnderstand='1')
        ctx.out_header.Data = 'null'

        # Set return message name
        if isinstance(req, models.DummyInput):
            # Generate 'empty' request to CPE using empty message name
            ctx.descriptor.out_message.Attributes.sub_name = 'EmptyHttp'
            return models.AcsToCpeRequests()
        ctx.descriptor.out_message.Attributes.sub_name = req.__class__.__name__
        return cls._generate_acs_to_cpe_request_copy(req)

    @classmethod
    def _get_tr069_response_from_sm(
            cls,
            ctx: WsgiMethodContext,
            message: ComplexModelBase,
    ) -> ComplexModelBase:
        # We want to blanket-catch all exceptions because a problem with one
        # tr-069 session shouldn't tank the service for all other enodeB's
        # being managed
        try:
            return cls.state_machine_manager.handle_tr069_message(ctx, message)
        except Exception:   # pylint: disable=broad-except
            logger.exception(
                'Unexpected exception from state machine manager, returning '
                'empty request',
            )
            return models.DummyInput()

    @staticmethod
    def _generate_acs_to_cpe_request_copy(request):
        """ Create an AcsToCpeRequests instance with all the appropriate
            members set from the input request. AcsToCpeRequests is a union of
            all request messages, so field names match.
        """
        request_out = models.AcsToCpeRequests()
        for parameter in request.get_flat_type_info(request.__class__):
            try:
                setattr(request_out, parameter, getattr(request, parameter))
            except AttributeError:
                # Allow un-set parameters. If CPE can't handle this, it will
                # respond with an error message
                pass

        return request_out

    # CPE->ACS RPC calls

    @rpc(
        models.GetRPCMethods,
        _returns=models.GetRPCMethodsResponse,
        _body_style="bare",
        _operation_name="GetRPCMethods",
        _out_message_name="GetRPCMethodsResponse",
    )
    def get_rpc_methods(ctx, request):
        """ GetRPCMethods RPC call is terminated here. No need to pass to higher
            layer """
        fill_response_header(ctx)
        resp = AutoConfigServer._handle_tr069_message(ctx, request)
        return resp

    @rpc(
        models.Inform,
        _returns=models.InformResponse,
        _body_style="bare",
        _operation_name="Inform",
        _out_message_name="InformResponse",
    )
    def inform(ctx, request):
        """ Inform response generated locally """
        fill_response_header(ctx)
        resp = AutoConfigServer._handle_tr069_message(ctx, request)
        resp.MaxEnvelopes = AutoConfigServer._max_envelopes
        return resp

    @rpc(
        models.TransferComplete,
        _returns=models.TransferCompleteResponse,
        _body_style="bare",
        _operation_name="TransferComplete",
        _out_message_name="TransferCompleteResponse",
    )
    def transfer_complete(ctx, request):
        fill_response_header(ctx)
        resp = AutoConfigServer._handle_tr069_message(ctx, request)
        resp.MaxEnvelopes = AutoConfigServer._max_envelopes
        return resp

    # Spyne does not handle no input or SimpleModel input for 'bare' function
    # DummyInput is unused
    # pylint: disable=unused-argument
    @rpc(
        models.DummyInput,
        _returns=models.AcsToCpeRequests,
        _out_message_name="EmptyHttp",
        _body_style='bare',
        _operation_name="EmptyHttp",
    )
    def empty_http(ctx, dummy):
        # Function to handle empty HTTP request
        return AutoConfigServer._handle_tr069_message(ctx, dummy)

    # CPE->ACS responses to ACS->CPE RPC calls

    @rpc(
        models.SetParameterValuesResponse,
        _returns=models.AcsToCpeRequests,
        _out_message_name="MessageNameToBeReplaced",
        _body_style='bare',
        _operation_name="SetParameterValuesResponse",
    )
    def set_parameter_values_response(ctx, response):
        return AutoConfigServer._handle_tr069_message(ctx, response)

    @rpc(
        models.GetParameterValuesResponse,
        _returns=models.AcsToCpeRequests,
        _out_message_name="MessageNameToBeReplaced",
        _body_style='bare',
        _operation_name="GetParameterValuesResponse",
    )
    def get_parameter_values_response(ctx, response):
        return AutoConfigServer._handle_tr069_message(ctx, response)

    @rpc(
        models.GetParameterNamesResponse,
        _returns=models.AcsToCpeRequests,
        _out_message_name="MessageNameToBeReplaced",
        _body_style='bare',
        _operation_name="GetParameterNamesResponse",
    )
    def get_parameter_names_response(ctx, response):
        return AutoConfigServer._handle_tr069_message(ctx, response)

    @rpc(
        models.SetParameterAttributesResponse,
        _returns=models.AcsToCpeRequests,
        _out_message_name="MessageNameToBeReplaced",
        _body_style='bare',
        _operation_name="SetParameterAttributesResponse",
    )
    def set_parameter_attributes_response(ctx, response):
        return AutoConfigServer._handle_tr069_message(ctx, response)

    @rpc(
        models.GetParameterAttributesResponse,
        _returns=models.AcsToCpeRequests,
        _out_message_name="MessageNameToBeReplaced",
        _body_style='bare',
        _operation_name="GetParameterAttributesResponse",
    )
    def get_parameter_attributes_response(ctx, response):
        return AutoConfigServer._handle_tr069_message(ctx, response)

    @rpc(
        models.AddObjectResponse,
        _returns=models.AcsToCpeRequests,
        _out_message_name="MessageNameToBeReplaced",
        _body_style='bare',
        _operation_name="AddObjectResponse",
    )
    def add_object_response(ctx, response):
        return AutoConfigServer._handle_tr069_message(ctx, response)

    @rpc(
        models.DeleteObjectResponse,
        _returns=models.AcsToCpeRequests,
        _out_message_name="MessageNameToBeReplaced",
        _body_style='bare',
        _operation_name="DeleteObjectResponse",
    )
    def delete_object_response(ctx, response):
        return AutoConfigServer._handle_tr069_message(ctx, response)

    @rpc(
        models.DownloadResponse,
        _returns=models.AcsToCpeRequests,
        _out_message_name="MessageNameToBeReplaced",
        _body_style='bare',
        _operation_name="DownloadResponse",
    )
    def download_response(ctx, response):
        return AutoConfigServer._handle_tr069_message(ctx, response)

    @rpc(
        models.RebootResponse,
        _returns=models.AcsToCpeRequests,
        _out_message_name="MessageNameToBeReplaced",
        _body_style='bare',
        _operation_name="RebootResponse",
    )
    def reboot_response(ctx, response):
        return AutoConfigServer._handle_tr069_message(ctx, response)

    @rpc(
        models.Fault,
        _returns=models.AcsToCpeRequests,
        _out_message_name="MessageNameToBeReplaced",
        _body_style='bare',
        _operation_name="Fault",
    )
    def fault(ctx, response):
        return AutoConfigServer._handle_tr069_message(ctx, response)


def on_method_return_string(ctx):
    """
    By default, spyne adds a namespace to every single XML element.
    There isn't a way to change this behavior, and the spyne-recommended way
    to fix this is by doing string manipulation. The TR-069 spec mandates that
    only the top-level CWMP elements contain namespaces. Hence this
    function is to remove namespaces from all elements except top-level CWMP
    elements (e.g. RPC request/response names, header elements).
    """
    # Format strings for XML tags, corresponding to:
    # 1) Normal start or end tag (without attribute)
    # 2) Open and close tag (when no attributes or sub-structures exist)
    # 3) Tag containing attributes
    # We don't just look for 'cwmp:%s' (with no character after %s) because this
    # would pick up all tags that start with the tag of interest (e.g
    # cwmp:SetParameterAttributes would also match
    # cwmp:SetParameterAttributesStruct)

    XML_FORMAT_STRS = [
        ["cwmp:%s>", "!!!TEMP_MOD!!!:%s>"],
        ["cwmp:%s/>", "!!!TEMP_MOD!!!:%s/>"],
        ["cwmp:%s ", "!!!TEMP_MOD!!!:%s "],
    ]
    fields_to_preserve_ns = list(RPC_METHODS) + list(RPC_RESPONSES) + \
        list(CPE_RPC_METHODS) + list(CPE_RPC_RESPONSES) + \
        list(PSEUDO_RPC_METHODS) + list(TOP_LEVEL_HEADER_ELEMENTS)
    for field in fields_to_preserve_ns:
        for formats in XML_FORMAT_STRS:
            orig_str = formats[0] % field
            temp_str = formats[1] % field
            ctx.out_string[0] = ctx.out_string[0].replace(
                orig_str.encode('ascii'), temp_str.encode('ascii'),
            )

    # Also preserve namespace inside strings, e.g. for arrayType="cwmp:..."
    orig_str = "=\"cwmp:"
    temp_str = "=\"!!!TEMP_MOD!!!:"
    ctx.out_string[0] = ctx.out_string[0].replace(
        orig_str.encode('ascii'), temp_str.encode('ascii'),
    )
    orig_str = "=\'cwmp:"
    temp_str = "=\'!!!TEMP_MOD!!!:"
    ctx.out_string[0] = ctx.out_string[0].replace(
        orig_str.encode('ascii'), temp_str.encode('ascii'),
    )

    ctx.out_string[0] = ctx.out_string[0].replace(b'cwmp:', b'')
    ctx.out_string[0] = ctx.out_string[0].replace(b'!!!TEMP_MOD!!!:', b'cwmp:')

    # Special-case handling so that 'EmptyHttp' RPC will be called using
    # completely empty HTTP request (not even containing a SOAP envelope), as
    # per TR-069 spec.
    if(ctx.descriptor.out_message.Attributes.sub_name == 'EmptyHttp'):
        ctx.out_string = [b'']

AutoConfigServer.event_manager.add_listener(
    'method_return_string',
    on_method_return_string,
)