"""
    Requirements:
        pysnmp
        pysnmp-mibs
"""

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

from pysnmp.entity.rfc3413.oneliner import cmdgen as pysnmp
import collections

def options (parser) :
    parser = optparse.OptionGroup(parser, "SNMP Agent")

    parser.add_option('--snmp-community',
            help="SNMPv2 read community")

    return parser

class SNMPError (Exception) :
    pass

class SNMPEngineError (SNMPError) :
    """
        Internal SNMP Engine error (?)
    """

class SNMPAgent (object) :
    """
        GET SNMP shit from a remote host.
    """

    SNMP_PORT = 161
    snmp_cmdgen = pysnmp.CommandGenerator()

    @classmethod
    def apply (cls, options, host, community=None) :
        port = cls.SNMP_PORT

        if community is None :
            community = options.snmp_community


        if '@' in host :
            community, host = host.split('@', 1)
        
        if ':' in host :
            host, port = host.rsplit(':', 1)

        return cls(
                pysnmp.CommunityData(community),
                pysnmp.UdpTransportTarget((host, port))
        )

    def __init__ (self, security, transport) :
        self.security = security
        self.transport = transport

    def get (self, *request) :
        """
            request = (
                pysnmp.MibVariable('IF-MIB', 'ifInOctets', 1),
            )
        """

        opts = dict(
                lookupNames     = True,
                lookupValues    = True,
        )

        try :
            error, error_status, error_index, response = self.snmp_cmdgen.getCmd(self.security, self.transport,  *request, **opts)
        except pysnmp.error.PySnmpError as ex :
            raise SNMPEngineError(ex)

        if error :
            raise SNMPEngineError(error)
        
        if error_status :
            raise SNMPError(errorStatus.prettyPrint())
        
        return response
        #for name, value in response :
        #    yield name.getMibSymbol(), value.prettyPrint()

    def walk (self, *request) :
        """
            request = (
                    pysnmp.MibVariable('IF-MIB', 'ifInOctets'),
            )
        """

        opts = dict(
                lookupNames     = True,
                lookupValues    = True,
        )

        try :
            error, error_status, error_index, responses = self.snmp_cmdgen.nextCmd(self.security, self.transport, *request, **opts)
        except pysnmp.error.PySnmpError as ex :
            raise SNMPEngineError(ex)

        if error :
            raise SNMPEngineError(error)
        
        if error_status :
            raise SNMPError(errorStatus.prettyPrint())
        
        return responses
        #for response in responses:
        #    for name, value in response :
        #        yield name.getMibSymbol(), value.prettyPrint()

    def table (self, *columns) :
        """
            Given [oid] returns { idx: { oid: value } }
        """

        data = collections.defaultdict(dict)

        for row in self.walk(*columns) :
            log.debug("%s", row)

            for column, (field, value) in zip(columns, row) :
                mib, sym, idx = field.getMibSymbol()

                log.debug("%s::%s[%s]: %s: %s", mib, sym, ', '.join(str(x) for x in idx), column, value)
                
                data[idx][column] = value
            
        return data.items()