from . import *
from udsoncan.Response import Response
from udsoncan.exceptions import *
import struct


class ReadDataByIdentifier(BaseService):
    _sid = 0x22
    _use_subfunction = False


    supported_negative_response = [	 Response.Code.IncorrectMessageLengthOrInvalidFormat,
                                                    Response.Code.ConditionsNotCorrect,
                                                    Response.Code.RequestOutOfRange,
                                                    Response.Code.SecurityAccessDenied
                                                    ]	

    @classmethod
    def validate_didlist_input(cls, dids):
        if not isinstance(dids, int) and not isinstance(dids, list):
            raise ValueError("Data Identifier must either be an integer or a list of integer")

        if isinstance(dids, int):
            ServiceHelper.validate_int(dids, min=0, max=0xFFFF, name='Data Identifier')

        if isinstance(dids, list):
            for did in dids:
                ServiceHelper.validate_int(did, min=0, max=0xFFFF, name='Data Identifier')


        return [dids] if not isinstance(dids, list) else dids

    @classmethod
    def make_request(cls, didlist, didconfig):
        """
        Generates a request for ReadDataByIdentifier

        :param didlist: List of data identifier to read.
        :type didlist: list[int]

        :param didconfig: Definition of DID codecs. Dictionary mapping a DID (int) to a valid :ref:`DidCodec<DidCodec>` class or pack/unpack string 
        :type didconfig: dict[int] = :ref:`DidCodec<DidCodec>`

        :raises ValueError: If parameters are out of range, missing or wrong type
        :raises ConfigError: If didlist contains a DID not defined in didconfig
        """		
        from udsoncan import Request
        from udsoncan import DidCodec

        didlist = cls.validate_didlist_input(didlist)

        req = Request(cls)
        ServiceHelper.check_did_config(didlist, didconfig)

        did_reading_all_data = None
        for did in didlist:
            if did not in didconfig:    # Already checked in check_did_config. Paranoid check
                raise ConfigError(key=did, msg='Actual data identifier configuration contains no definition for data identifier 0x%04x' % did)
                
            codec = DidCodec.from_config(didconfig[did])
            try:
                length = len(codec)
                if did_reading_all_data is not None:
                    raise ValueError('Did 0x%04X is configured to read the rest of the payload (__len__ raisong ReadAllRemainingData), but a subsequent DID is requested (0x%04x)' % (did_reading_all_data, did))
            except DidCodec.ReadAllRemainingData:
                if did_reading_all_data is not None:
                    raise ValueError('It is impossible to read 2 DIDs configured to read the rest of the payload (__len__ raising ReadAllRemainingData). Dids are : 0x%04X and 0x%04X' % (did_reading_all_data, did))
                did_reading_all_data = did

        req.data = struct.pack('>'+'H'*len(didlist), *didlist) #Encode list of DID

        return req

    @classmethod
    def interpret_response(cls, response, didlist, didconfig, tolerate_zero_padding=True):
        """
        Populates the response ``service_data`` property with an instance of :class:`ReadDataByIdentifier.ResponseData<udsoncan.services.ReadDataByIdentifier.ResponseData>`

        :param response: The received response to interpret
        :type response: :ref:`Response<Response>`

        :param didlist:  List of data identifiers used for the request.
        :type didlist: list[int]

        :param didconfig: Definition of DID codecs. Dictionary mapping a DID (int) to a valid :ref:`DidCodec<DidCodec>` class or pack/unpack string 
        :type didconfig: dict[int] = :ref:`DidCodec<DidCodec>`

        :param tolerate_zero_padding: Ignore trailing zeros in the response data avoiding raising false :class:`InvalidResponseException<udsoncan.exceptions.InvalidResponseException>`.
        :type tolerate_zero_padding: bool

        :raises ValueError: If parameters are out of range, missing or wrong type
        :raises ConfigError: If ``didlist`` parameter or response contains a DID not defined in ``didconfig``.
        :raises InvalidResponseException: If response data is incomplete or if DID data does not match codec length.
        """	
        from udsoncan import DidCodec

        didlist = cls.validate_didlist_input(didlist)
        didconfig = ServiceHelper.check_did_config(didlist, didconfig)

        response.service_data = cls.ResponseData()
        response.service_data.values = {}

        # Parsing algorithm to extract DID value
        offset = 0
        while True:
            if len(response.data) <= offset:
                break	# Done

            if len(response.data) <= offset +1:
                if tolerate_zero_padding and response.data[-1] == 0:	# One extra byte, but it's a 0 and we accept that. So we're done
                    break
                raise InvalidResponseException(response, "Response given by server is incomplete.")

            did = struct.unpack('>H', response.data[offset:offset+2])[0]	# Get the DID number
            if did == 0 and did not in didconfig and tolerate_zero_padding: # We read two zeros and that is not a DID bu we accept that. So we're done.
                if response.data[offset:] == b'\x00' * (len(response.data) - offset):
                    break

            if did not in didconfig:	# Already checked in check_did_config. Paranoid check
                raise ConfigError(key=did, msg='Actual data identifier configuration contains no definition for data identifier 0x%04x' % did)

            codec = DidCodec.from_config(didconfig[did])
            offset+=2

            try:
                payload_size = len(codec)
            except DidCodec.ReadAllRemainingData:
                payload_size = len(response.data) - offset

            if len(response.data) < offset+payload_size:
                raise InvalidResponseException(response, "Value for data identifier 0x%04x was incomplete according to definition in configuration" % did)

            subpayload = response.data[offset:offset+payload_size]
            offset += payload_size	# Codec must define a __len__ function that matches the encoded payload length.
            val = codec.decode(subpayload)
            response.service_data.values[did] = val

        return response

    class ResponseData(BaseResponseData):
        """
        .. data:: values

                Dictionary mapping the DID (int) with the value returned by the associated :ref:`DidCodec<DidCodec>`.decode method
        """				
        def __init__(self):
            super().__init__(ReadDataByIdentifier)

            self.values = None
