import struct
from typing import Optional, Union, List


class DataMessage:
    """It is typing used of the abstract interface of ReSampleEntry which is defined in c extension.

    **Response Message Format**

    ::

        |               |   1           |       2       |           3   |
        0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2
        -----------------------------------------------------------------
        | header        | data ........................................ |

    header
        message header

        ===== ==================
        value description
        ===== ==================
        0     system message
        1     parameter error
        2     general message
        3     data message
        ===== ==================

    1.  system message (header=0)

        ::

            |               |   1           |       2       |           3   |
            0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2
            -----------------------------------------------------------------
            | header=0xFF   | length        | message ..................... |


    #.  data message

        see :class:`DataMessageEncoderType` for more detail

    **Command format**

    1.  command

        1.  greeting

            echo greeting

            response: ``greeting``

        #.  sync, sync:DEVICE, sync:DEVICE,...

            return current Data server is sync or not.

            response: ``start:DEVICE``, ``stop:DEVICE`` for each connected device

        #.  broadcast:MESSAGE

            broadcast MESSAGE, send to controller

        #.  start, stop

            start/stop routine data streaming.

    2.  response

        1.  scan, scan:update, scan:done

            controller scanned, found device updated

        #.  connected, connected:DEVICE

            device connected

        #.  disconnected, disconnected:DEVICE

            device disconnected

        #.  start:DEVICE,..., stop:DEVICE,...

        #.  low_power:STATE (ups power using)

        #.  message::MESSAGE, message:DEVICE:MESSAGE

            data notify message

        #.  broadcast:MESSAGE

            broadcast MESSAGE, receive from controller

        #.  info:MESSAGE, warn:MESSAGE, error:MESSAGE

            message for command response

    """

    HEADER_SYSTEM = 0xFF

    __slots__ = ()

    GREETING = 'greeting'
    SYNC = 'sync'
    BROADCAST = 'broadcast'
    START_DATA_STREAM = 'start'
    STOP_DATA_STREAM = 'stop'

    SCAN = 'scan'
    SCAN_STATE = ('', 'update', 'done')

    LOW_POWER = 'low_power'
    LOW_POWER_STATE = ('UPS', 'EXT', 'OFF')

    @classmethod
    def response(cls, message: str) -> bytes:
        message = message.encode()

        return struct.pack('<2B%ds' % len(message), cls.HEADER_SYSTEM, len(message), message)

    @classmethod
    def greeting(cls) -> str:
        return cls.GREETING

    @classmethod
    def scan(cls, state: Optional[str] = None) -> str:
        if state is None:
            return cls.SCAN + ':done'
        elif state == '':
            return cls.SCAN
        elif state in cls.SCAN_STATE:
            return cls.SCAN + ':' + state
        else:
            raise ValueError()

    @classmethod
    def sync(cls, sync: bool) -> str:
        return 'start' if sync else 'stop'

    @classmethod
    def low_power(cls, ups_state: str):
        if ups_state in cls.LOW_POWER_STATE:
            return cls.LOW_POWER + ':' + ups_state
        else:
            raise ValueError()

    @classmethod
    def start(cls, device: Union[None, int, List[int]] = None) -> str:
        if device is None:
            return 'start'
        elif isinstance(device, int):
            return 'start:' + str(device)
        else:
            return 'start:' + ','.join(map(str, device))

    @classmethod
    def stop(cls, device: Union[None, int, List[int]] = None) -> str:
        if device is None:
            return 'stop'
        elif isinstance(device, int):
            return 'stop:' + str(device)
        else:
            return 'stop:' + ','.join(map(str, device))

    @classmethod
    def message(cls, message: str, device: Optional[int] = None) -> str:
        if device is None:
            return 'message::' + message
        else:
            return 'message:' + str(device) + ':' + message

    @classmethod
    def broadcast(cls, message: str) -> str:
        return 'broadcast:' + message

    @classmethod
    def connected(cls, device: Optional[int] = None) -> str:
        if device is None:
            return 'connected'
        else:
            return 'connected:' + str(device)

    @classmethod
    def disconnected(cls, device: Optional[int] = None) -> str:
        if device is None:
            return 'disconnected'
        else:
            return 'disconnected:' + str(device)

    @classmethod
    def info(cls, message: str) -> str:
        return 'info:' + message

    @classmethod
    def warn(cls, message: str) -> str:
        return 'warn:' + message

    @classmethod
    def error(cls, message: str) -> str:
        return 'error:' + message