Creates a generator to send SNMP notification.

    When iterator gets advanced by :py:mod:`asyncio` main loop,
    SNMP TRAP or INFORM notification is send (:RFC:`1905#section-4.2.6`).
    The iterator yields :py:class:`asyncio.Future` which gets done whenever
    response arrives or error occurs.

    Parameters
    ----------
    snmpDispatcher: :py:class:`~pysnmp.hlapi.v1arch.asyncore.SnmpDispatcher`
        Class instance representing asynio-based asynchronous event loop and
        associated state information.

    authData: :py:class:`~pysnmp.hlapi.v1arch.CommunityData`
        Class instance representing SNMPv1/v2c credentials.

    transportTarget: :py:class:`~pysnmp.hlapi.v1arch.asyncio.UdpTransportTarget` or
        :py:class:`~pysnmp.hlapi.v1arch.asyncio.Udp6TransportTarget` Class instance representing
        transport type along with SNMP peer address.

    notifyType : str
        Indicates type of notification to be sent. Recognized literal
        values are *trap* or *inform*.

    \*varBinds: :class:`tuple` of OID-value pairs or :py:class:`~pysnmp.smi.rfc1902.ObjectType` or :py:class:`~pysnmp.smi.rfc1902.NotificationType`
        One or more objects representing MIB variables to place
        into SNMP notification. It could be tuples of OID-values
        or :py:class:`~pysnmp.smi.rfc1902.ObjectType` class instances
        of :py:class:`~pysnmp.smi.rfc1902.NotificationType` objects.

        Besides user variable-bindings, SNMP Notification PDU requires at
        least two variable-bindings to be present:

        0. SNMPv2-MIB::sysUpTime.0 = <agent uptime>
        1. SNMPv2-SMI::snmpTrapOID.0 = <notification ID>

        When sending SNMPv1 TRAP, more variable-bindings could be present:

        2. SNMP-COMMUNITY-MIB::snmpTrapAddress.0 = <agent-IP>
        3. SNMP-COMMUNITY-MIB::snmpTrapCommunity.0 = <snmp-community-name>
        4. SNMP-COMMUNITY-MIB::snmpTrapEnterprise.0 = <enterprise-OID>

        If user does not supply some or any of the above variable-bindings or
        if they are at the wrong positions, the system will add/reorder the
        missing ones automatically.

        On top of that, some notification types imply including some additional
        variable-bindings providing additional details on the event being
        reported. Therefore it is generally easier to use
        :py:class:`~pysnmp.smi.rfc1902.NotificationType` object which will
        help adding relevant variable-bindings.

    Other Parameters
    ----------------
    \*\*options :
        Request options:

        * `lookupMib` - load MIB and resolve response MIB variables at
          the cost of slightly reduced performance. Default is `False`,
          unless :py:class:`~pysnmp.smi.rfc1902.ObjectType` or
          :py:class:`~pysnmp.smi.rfc1902.NotificationType` is present
          among `varBinds` in which case `lookupMib` gets automatically
          enabled.

    Yields
    ------
    errorIndication: str
        True value indicates SNMP engine error.
    errorStatus: str
        True value indicates SNMP PDU error.
    errorIndex: int
        Non-zero value refers to `varBinds[errorIndex-1]`
    varBinds: tuple
        A sequence of OID-value pairs in form of base SNMP types (if
        `lookupMib` is `False`) or :py:class:`~pysnmp.smi.rfc1902.ObjectType`
        class instances (if `lookupMib` is `True`) representing MIB variables
        returned in SNMP response.

    Raises
    ------
    PySnmpError
        Or its derivative indicating that an error occurred while
        performing SNMP operation.

    Examples
    --------
    >>> import asyncio
    >>> from pysnmp.hlapi.asyncio import *
    >>>
    >>> @asyncio.coroutine
    ... def run():
    ...     errorIndication, errorStatus, errorIndex, varBinds = yield from sendNotification(
    ...         SnmpDispatcher(),
    ...         CommunityData('public'),
    ...         UdpTransportTarget(('demo.snmplabs.com', 162)),
    ...         'trap',
    ...         NotificationType(ObjectIdentity('IF-MIB', 'linkDown')))
    ...     print(errorIndication, errorStatus, errorIndex, varBinds)
    ...
    >>> asyncio.get_event_loop().run_until_complete(run())
    (None, 0, 0, [])
    >>>

def sendNotification(snmpDispatcher, authData, transportTarget,
                     notifyType, *varBinds, **options):
    """Creates a generator to send SNMP notification.

    When iterator gets advanced by :py:mod:`asyncio` main loop,
    SNMP TRAP or INFORM notification is send (:RFC:`1905#section-4.2.6`).
    The iterator yields :py:class:`asyncio.Future` which gets done whenever
    response arrives or error occurs.

    Parameters
    ----------
    snmpDispatcher: :py:class:`~pysnmp.hlapi.v1arch.asyncore.SnmpDispatcher`
        Class instance representing asynio-based asynchronous event loop and
        associated state information.

    authData: :py:class:`~pysnmp.hlapi.v1arch.CommunityData`
        Class instance representing SNMPv1/v2c credentials.

    transportTarget: :py:class:`~pysnmp.hlapi.v1arch.asyncio.UdpTransportTarget` or
        :py:class:`~pysnmp.hlapi.v1arch.asyncio.Udp6TransportTarget` Class instance representing
        transport type along with SNMP peer address.

    notifyType : str
        Indicates type of notification to be sent. Recognized literal
        values are *trap* or *inform*.

    \*varBinds: :class:`tuple` of OID-value pairs or :py:class:`~pysnmp.smi.rfc1902.ObjectType` or :py:class:`~pysnmp.smi.rfc1902.NotificationType`
        One or more objects representing MIB variables to place
        into SNMP notification. It could be tuples of OID-values
        or :py:class:`~pysnmp.smi.rfc1902.ObjectType` class instances
        of :py:class:`~pysnmp.smi.rfc1902.NotificationType` objects.

        Besides user variable-bindings, SNMP Notification PDU requires at
        least two variable-bindings to be present:

        0. SNMPv2-MIB::sysUpTime.0 = <agent uptime>
        1. SNMPv2-SMI::snmpTrapOID.0 = <notification ID>

        When sending SNMPv1 TRAP, more variable-bindings could be present:

        2. SNMP-COMMUNITY-MIB::snmpTrapAddress.0 = <agent-IP>
        3. SNMP-COMMUNITY-MIB::snmpTrapCommunity.0 = <snmp-community-name>
        4. SNMP-COMMUNITY-MIB::snmpTrapEnterprise.0 = <enterprise-OID>

        If user does not supply some or any of the above variable-bindings or
        if they are at the wrong positions, the system will add/reorder the
        missing ones automatically.

        On top of that, some notification types imply including some additional
        variable-bindings providing additional details on the event being
        reported. Therefore it is generally easier to use
        :py:class:`~pysnmp.smi.rfc1902.NotificationType` object which will
        help adding relevant variable-bindings.

    Other Parameters
    ----------------
    \*\*options :
        Request options:

        * `lookupMib` - load MIB and resolve response MIB variables at
          the cost of slightly reduced performance. Default is `False`,
          unless :py:class:`~pysnmp.smi.rfc1902.ObjectType` or
          :py:class:`~pysnmp.smi.rfc1902.NotificationType` is present
          among `varBinds` in which case `lookupMib` gets automatically
          enabled.

    Yields
    ------
    errorIndication: str
        True value indicates SNMP engine error.
    errorStatus: str
        True value indicates SNMP PDU error.
    errorIndex: int
        Non-zero value refers to `varBinds[errorIndex-1]`
    varBinds: tuple
        A sequence of OID-value pairs in form of base SNMP types (if
        `lookupMib` is `False`) or :py:class:`~pysnmp.smi.rfc1902.ObjectType`
        class instances (if `lookupMib` is `True`) representing MIB variables
        returned in SNMP response.

    Raises
    ------
    PySnmpError
        Or its derivative indicating that an error occurred while
        performing SNMP operation.

    Examples
    --------
    >>> import asyncio
    >>> from pysnmp.hlapi.asyncio import *
    >>>
    >>> @asyncio.coroutine
    ... def run():
    ...     errorIndication, errorStatus, errorIndex, varBinds = yield from sendNotification(
    ...         SnmpDispatcher(),
    ...         CommunityData('public'),
    ...         UdpTransportTarget(('demo.snmplabs.com', 162)),
    ...         'trap',
    ...         NotificationType(ObjectIdentity('IF-MIB', 'linkDown')))
    ...     print(errorIndication, errorStatus, errorIndex, varBinds)
    ...
    >>> asyncio.get_event_loop().run_until_complete(run())
    (None, 0, 0, [])
    >>>
    """

    sysUpTime = v2c.apiTrapPDU.sysUpTime
    snmpTrapOID = v2c.apiTrapPDU.snmpTrapOID

    def _ensureVarBinds(varBinds):
        # Add sysUpTime if not present already
        if not varBinds or varBinds[0][0] != sysUpTime:
            varBinds.insert(0, (v2c.ObjectIdentifier(sysUpTime), v2c.TimeTicks(0)))

        # Search for and reposition sysUpTime if it's elsewhere
        for idx, varBind in enumerate(varBinds[1:]):
            if varBind[0] == sysUpTime:
                varBinds[0] = varBind
                del varBinds[idx + 1]
                break

        if len(varBinds) < 2:
            raise error.PySnmpError('SNMP notification PDU requires '
                                    'SNMPv2-MIB::snmpTrapOID.0 to be present')

        # Search for and reposition snmpTrapOID if it's elsewhere
        for idx, varBind in enumerate(varBinds[2:]):
            if varBind[0] == snmpTrapOID:
                del varBinds[idx + 2]
                if varBinds[1][0] == snmpTrapOID:
                    varBinds[1] = varBind
                else:
                    varBinds.insert(1, varBind)
                break

        # Fail on missing snmpTrapOID
        if varBinds[1][0] != snmpTrapOID:
            raise error.PySnmpError('SNMP notification PDU requires '
                                    'SNMPv2-MIB::snmpTrapOID.0 to be present')

        return varBinds

    def _cbFun(snmpDispatcher, stateHandle, errorIndication, rspPdu, _cbCtx):
        if future.cancelled():
            return

        errorStatus = v2c.apiTrapPDU.getErrorStatus(rspPdu)
        errorIndex = v2c.apiTrapPDU.getErrorIndex(rspPdu)

        varBinds = v2c.apiTrapPDU.getVarBinds(rspPdu)

        try:
            varBindsUnmade = VB_PROCESSOR.unmakeVarBinds(snmpDispatcher.cache, varBinds,
                                                         lookupMib)
        except Exception as e:
            future.set_exception(e)

        else:
            future.set_result(
                (errorIndication, errorStatus, errorIndex, varBindsUnmade)
            )

    lookupMib = options.get('lookupMib')

    if not lookupMib and any(isinstance(x, (NotificationType, ObjectType))
                             for x in varBinds):
        lookupMib = True

    if lookupMib:
        varBinds = VB_PROCESSOR.makeVarBinds(snmpDispatcher.cache, varBinds)

    if notifyType == 'trap':
        reqPdu = v2c.TrapPDU()
    else:
        reqPdu = v2c.InformRequestPDU()

    v2c.apiTrapPDU.setDefaults(reqPdu)
    v2c.apiTrapPDU.setVarBinds(reqPdu, varBinds)

    varBinds = v2c.apiTrapPDU.getVarBinds(reqPdu)

    v2c.apiTrapPDU.setVarBinds(reqPdu, _ensureVarBinds(varBinds))

    if authData.mpModel == 0:
        reqPdu = rfc2576.v2ToV1(reqPdu)

    future = asyncio.Future()

    snmpDispatcher.sendPdu(authData, transportTarget, reqPdu, cbFun=_cbFun)

    if notifyType == 'trap':
        def __trapFun(future):
            if future.cancelled():
                return
            future.set_result((None, 0, 0, []))

        loop = asyncio.get_event_loop()
        loop.call_soon(__trapFun, future)

    return future