# Source code for canlib.linlib.channel

    from collections import namedtuple
    import ctypes as ct

    from ..frame import LINFrame
    from .. import VersionNumber
    from .enums import ChannelType, Setup, MessageFlag
    from .structures import MessageInfo
    from .wrapper import dll

    FirmwareVersion = namedtuple('FirmwareVersion', 'boot_version app_version')

    def openChannel(channel_number, channel_type, bps=None):
        """Open a channel to a LIN interface.

        Args:
            channel_number (`int`): The number of the channel. This is the same
                channel number as used by `canlib.canlib.ppenChannel`.
            channel_type (`ChannelType`): Whether the LIN interface will be a
                master or slave.
            bps (`int` or `None`): If not `None`, `Channel.setBitrate` will be called with
                this value before the channel is returned.

        Returns:
            (`Channel`): The opened channel

        Note:
            For DRV Lin: The cable must be powered and connected to a LAPcan channel.
            For Kvaser LIN Leaf: The Leaf must be powered from the LIN side.

        """
        handle = dll.linOpenChannel(channel_number, channel_type)
        channel = Channel(handle)
        if bps is not None:
            channel.setBitrate(bps)
        return channel

    def openMaster(channel_number, bps=None):
        """Open a channel as a master

        This function simply calls `openChannel` with `channel_type` set to
        `ChannelType.MASTER`.

        """
        return openChannel(channel_number, ChannelType.MASTER, bps=bps)

    def openSlave(channel_number, bps=None):
        """Open a channel as a slave

        This function simply calls `openChannel` with `channel_type` set to
        `ChannelType.SLAVE`.

        """
        return openChannel(channel_number, ChannelType.SLAVE, bps=bps)

    class Channel(object):
        """A LINlib channel

        This class is normally instantiated with `openMaster` or `openSlave`.

        Channels are automatically closed on garbage collection, and can
        also be used as context managers in which case they close as soon as the
        context exits.

        """
        def __init__(self, handle):
            self.handle = handle

        def __del__(self):
            self.close()

        def __enter__(self):
            return self

        def __exit__(self, type, value, traceback):
            self.close()

        # def readTimer():
        #     raise NotImplementedError

        def busOff(self):
            """Go bus off

            This function deactivates the LIN interface. It will not participate
            further in the LIN bus traffic.

            """
            dll.linBusOff(self.handle)

        def busOn(self):
            """Go bus on

            This function activates the LIN interface.

            """
            dll.linBusOn(self.handle)

        def clearMessage(self, msg_id):
            """Clear a message buffer for a LIN slave

            The message buffer will not answer next time it is polled.

            """
            dll.linClearMessage(self.handle, msg_id)

        def close(self):
            """Close this LINlib channel

            Closes an open handle to a LIN channel.

            Note:

                It is normally not necessary to call this function directly, as the
                internal handle is automatically closed when the `Channel` object
                is garbage collected.

            .. versionadded:: 1.6

            """
            if self.handle is not None:
                self.busOff()
                dll.linClose(self.handle)
                self.handle = None

        def getCanHandle(self):
            """Return the CAN handle given an open LIN handle"""
            can_handle = ct.c_uint()
            dll.linGetCanHandle(self.handle, ct.byref(can_handle))
            return can_handle.value

        def getFirmwareVersion(self):
            """Retrieve the firmware version from the LIN interface

            Returns a `FirmwareVersion` namedtuple containing `boot_version` and
            `app_version` that are `canlib.VersionNumber` namedtuples. If only one of
            these is needed, the return value can be unpacked as such::

                boot_ver, app_ver = channel.getFirmwareVersion()

            Note:
                For newer interfaces use `getChannelData` with
                `ChannelData.CARD_FIRMWARE_REV` instead.

                The version numbers aren't valid until `Channel.busOn` has been
                called.

                The firmware in the LIN interface is divided into two parts, the
                boot code and the application. The boot code is used only when
                reprogramming (reflashing) the LIN interface. The application
                handles all LIN communication.

                Version numbers are, since the precambric era, divided into a major
                version number, a minor version number and a build
                number. These are usually written like, for example,
                3.2.12. Here the major number is 3, the minor number 2 and the
                build number 12.

            """
            bootver = [ct.c_ubyte() for i in range(3)]
            appver = [ct.c_ubyte() for i in range(3)]

            # In Python 2, you can't use '*' on more than one argument
            refs = tuple(ct.byref(ub) for ub in bootver) + tuple(ct.byref(ub) for ub in appver)
            dll.linGetFirmwareVersion(self.handle, *refs)
            bootver = [v.value for v in bootver]
            appver = [v.value for v in appver]
            return FirmwareVersion(
                boot_version=VersionNumber(*bootver),
                app_version=VersionNumber(*appver),
            )

        def read(self, timeout=0):
            """Read a message from the LIN interface

            If a message is available for reception, linOK is returned. This is a
            non-blocking call. It waits until a message is received in the LIN
            interface, or the specified timeout period elapses.

            This may return a frame sent by `writeMessage` or `writeWakeup`.

            Note:
                This call will also return echoes of what the LIN interface is
                transmitting with `writeMessage`. In other words, the LIN
                interface can hear itself.

            Args:
                timeout (`int`): Timeout in milliseconds.

            Returns:
                (`canlib.LINFrame`)

            """
            id_ = ct.c_uint()
            _MAX_SIZE = 8
            msg = ct.create_string_buffer(_MAX_SIZE)
            dlc = ct.c_uint()
            flags = ct.c_uint()
            info = MessageInfo()

            dll.linReadMessageWait(
                self.handle,
                ct.byref(id_),
                ct.byref(msg),
                ct.byref(dlc),
                ct.byref(flags),
                ct.byref(info),
                timeout,
            )

            length = min(_MAX_SIZE, dlc.value)
            return LINFrame(
                id_=id_.value,
                data=bytearray(msg.raw[:length]),
                dlc=dlc.value,
                flags=MessageFlag(int(flags.value)),  # in Python 2, we get a long
                info=info,
            )

        def requestMessage(self, msgid):
            """Request a message from a slave

            This function writes a LIN message header to the LIN bus. A slave in
            the system is then expected to fill in the header with data.

            Note:
                This call is only available in master mode.

            """
            dll.linRequestMessage(self.handle, msgid)

        def setBitrate(self, bps):
            """Set the bitrate in bits per second

            This function sets the bit rate for a master, or the initial bit rate
            for a slave. The LIN interface should not be on-bus when this function
            is called.

            Note:
                The LIN Interface should not be on bus.
                Supported bit rates are 1000 - 20000 bits per second.

            """
            assert 1000 <= bps <= 20000  # qqqdaca nicer error
            dll.linSetBitrate(self.handle, bps)

        def setupIllegalMessage(self, msgid, disturb_flags, delay):
            """Create a corrupted LIN message

            Using this function, it is possible to use the LIN interface to create
            corrupted LIN messages. You call the function once for each LIN
            identifier that should be affected.

            To return to normal mode, either restart the LIN interface (by going
            off bus and on the bus again) or call the function with delay and
            disturb_flags set to zero.

            Args:

                msgid (`int`): The identifier of the LIN message

                disturb_flags (`MessageDisturb`): One or more of the
                    `MessageDisturb` flags.

                delay (`int`): The delay parameter will result in a delay of this
                    many bittimes after the header and before the first data byte.

            Note:
                The LIN Interface must be on bus for this command to work.
                It is supported in firmware version 2.4.1 and later.

            """
            dll.linSetupIllegalMessage(self.handle, msgid, disturb_flags, delay)

        def setupLIN(self, flags=Setup.VARIABLE_DLC, bps=0):
            """Setup the LIN interface

            This function changes various settings on a LIN Interface that is on
            bus. When going on bus, the bit rate and the flag values listed below
            are set to the default value (either as hard-coded in the firmware, or
            as stored in the non-volatile memory of the LIN Interface).

            With this function, you can do one or more of the following things:

            * Select checksum according to LIN 2.0

            * Turn variable message length off. The message length then will depend
              on the message ID.

            In master mode it is also possible to change the bit rate without going
            off bus first.

            Note:
                The LIN Interface must be on bus for this command to work.
                It is supported in firmware version 2.5.1 and later.
                For LIN 2.0 compliance, you must specify both LIN_ENHANCED_CHECKSUM
                and LIN_VARIABLE_DLC.

            Args:

                flags (`Setup`): One or more of the `Setup` flags

                bps (`int`): The bit rate in bits per second. This parameter can be
                    used only in master mode. The bit rate is set without going off
                    bus.

            """
            dll.linSetupLIN(self.handle, flags, bps)

        def updateMessage(self, frame):
            """Update a message buffer in a slave

            This function updates a message buffer in a slave. The contents of the
            message buffer will be used the next time the slave is polled for the
            specified LIN message id.

            Note:
                The LIN Interface must be on bus.

            Args:

                frame (`canlib.Frame`): The information to be updated. Only the `Frame.id`,
                    `Frame.data`, and `Frame.dlc` attributes are used. Note that the frame can,
                    but not need not, be a `canlib.LINFrame`.

            """
            void_p_data = (ct.c_ubyte * frame.dlc)(*frame.data)
            dll.linUpdateMessage(self.handle, frame.id, void_p_data, frame.dlc)

        def writeMessage(self, frame):
            """Write a LIN message

            Write a LIN message. It is advisable to wait until the message is
            echoed by `read` before transmitting a new message, or in
            case of a schedule table being used, transmit the next message when the
            previous one is known to be complete.

            Note:
                Only available in master mode

            Args:

                frame (`canlib.Frame`) :: The information to be updated. Only the `Frame.id`,
                    `Frame.data`, and `Frame.dlc` attributes are used. Note that the frame can,
                    but not need not, be a `canlib.LINFrame`.

            """
            void_p_data = (ct.c_ubyte * frame.dlc)(*frame.data)
            dll.linWriteMessage(self.handle, frame.id, void_p_data, frame.dlc)

        def writeSync(self, timeout):
            """Make sure all message transmitted to the interface have been received

            *timeout* is in milliseconds.

            When messages are transmitted to the LIN Interface, they are queued by
            the driver before appearing on the CAN bus.

            If the LIN Interface is in master mode and a LIN message has been
            transmitted with `writeMessage`, this function will return when the LIN
            Interface has received the message. If another LIN message is being
            received or transmitted, the message will not be transmitted on the LIN
            bus at once. And even if the LIN Interface is idle, the header of the
            new message will just have been started when `writeSync` returns.

            After calling `updateMessage` and `clearMessage` for a slave, this
            function is enough to know that the LIN Interface is updated.

            After `writeMessage`, it is advisable to wait until the message is
            echoed by `read` before transmitting a new message, or in case
            of a schedule table being used, transmit the next message when the
            previous one is known to be complete.

            When, in master mode, a message should be transmitted after a poll
            (reception) is done, it might be necessary to call `writeMessage`
            before the result is received via `read` as the LIN Interface
            waits up to the maximum frame length before knowing a received message
            is complete. A new message to transmit will force completion if the
            currently received one.

            """
            dll.linWriteSync(self.handle, timeout)

        def writeWakeup(self, count=0, interval=1):
            """Write one or more wakeup frames

            If *count* is zero (the default), one single wakeup frame is
            transmitted. If *count* > 1, several wakeup frames are transmitted
            spaced with *interval* bit times. The LIN interface will interrupt the
            sequence when a LIN message or another command is received. The stream
            of wakeups will be recived as incoming messages with the
            `MessageFlag.RX` flag.

            Args:
                count (`int`): The number of wakeup frames to send.
                interval (`int`): The time, in bit times, between the wakeup  frames.

            """
            dll.linWriteWakeup(self.handle, count, interval)