"""
    Requirements:
        memoized-property

    Setup:
        ./opt/bin/build-pysnmp-mib -o usr/mibs/Q-BRIDGE-MIB.py etc/mibs/rfc2674_q.mib

    Run:
        PYSNMP_MIB_DIRS=usr/mibs/ ./opt/bin/python ...

    SNMP:
        Q-BRIDGE-MIB::dot1qVlanCurrentTable

"""

from pvl.snmp import snmp
from pvl.snmp.snmp import pysnmp

from memoized_property import memoized_property

import logging; log = logging.getLogger('pvl.snmp.vlan')

DOT1Q_NUM_VLANS = pysnmp.MibVariable('Q-BRIDGE-MIB', 'dot1qNumVlans')
DOT1Q_VLAN_CURRENT_EGRESS_PORTS = pysnmp.MibVariable('Q-BRIDGE-MIB', 'dot1qVlanCurrentEgressPorts')
DOT1Q_VLAN_CURRENT_UNTAGGED_PORTS = pysnmp.MibVariable('Q-BRIDGE-MIB', 'dot1qVlanCurrentUntaggedPorts')
DOT1Q_VLAN_STATIC_NAME = pysnmp.MibVariable('Q-BRIDGE-MIB', 'dot1qVlanStaticName')

def portlist (value) :
    r"""
        Unpack a OctetString bitmask into bit offsets.

        >>> list(portlist('\x80'))
        [1]
        >>> list(portlist('\x01'))
        [8]
    """

    for octet_idx, byte in enumerate(value) :
        octet = ord(byte)

        for bit_idx in xrange(0, 8) :
            if octet & (1 << (7 - bit_idx)) :
                yield octet_idx * 8 + bit_idx + 1

class VLANAgent (snmp.SNMPAgent) :
    """
        Query VLAN configuration.
    """

    @memoized_property
    def count (self) :
        for name, value in self.get(DOT1Q_NUM_VLANS) :
            # XXX: ????
            if value.tagSet == pysnmp.rfc1905.NoSuchInstance.tagSet :
                continue

            return int(value)

    def names (self) :
        """
                (vlan, name)
        """

        for idx, data in self.table(DOT1Q_VLAN_STATIC_NAME) :
            vlan, = idx

            yield int(vlan), str(data[DOT1Q_VLAN_STATIC_NAME])

    def vlan_ports (self) :
        """
            Get per-vlan port configs.

                (vlan, (tagged, untagged))
        """

        for idx, data in self.table(DOT1Q_VLAN_CURRENT_EGRESS_PORTS, DOT1Q_VLAN_CURRENT_UNTAGGED_PORTS) :
            time, vlan = idx

            egress = set(portlist(data[DOT1Q_VLAN_CURRENT_EGRESS_PORTS]))
            untagged = set(portlist(data[DOT1Q_VLAN_CURRENT_UNTAGGED_PORTS]))

            tagged = egress - untagged
            
            yield int(vlan), (tagged, untagged)

if __name__ == '__main__':
    import doctest
    doctest.testmod()