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#
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# Copyright (c) 2004 David R. Halliday
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# All rights reserved.
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#
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# This SNMP library is free software.  Redistribution is permitted under the
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# same terms and conditions as the standard Ruby distribution.  See the
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# COPYING file in the Ruby distribution for details.
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#
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require 'snmp/ber'
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require 'snmp/varbind'
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include SNMP::BER
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module SNMP
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# Exceptions thrown during message/pdu decoding
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class UnsupportedVersion < RuntimeError; end
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class UnsupportedPduTag < RuntimeError; end
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class InvalidPduTag < RuntimeError; end
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class ParseError < RuntimeError; end
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class InvalidErrorStatus < RuntimeError; end
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class InvalidTrapVarbind < RuntimeError; end
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class InvalidGenericTrap < RuntimeError; end
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SYS_UP_TIME_OID = ObjectId.new("1.3.6.1.2.1.1.3.0")
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SNMP_TRAP_OID_OID = ObjectId.new("1.3.6.1.6.3.1.1.4.1.0")
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class Message
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    attr_reader :version
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    attr_reader :community
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    attr_reader :pdu
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    class << self
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        def decode(data)
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            message_data, remainder = decode_sequence(data)
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            assert_no_remainder(remainder)
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            version, remainder = decode_version(message_data)
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            community, remainder = decode_octet_string(remainder)
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            pdu, remainder = decode_pdu(version, remainder)
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            assert_no_remainder(remainder)
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            Message.new(version, community, pdu)
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        end
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        def decode_version(data)
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            version_data, remainder = decode_integer(data)
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            if version_data == SNMP_V1
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                version = :SNMPv1
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            elsif version_data == SNMP_V2C
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                version = :SNMPv2c
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            else
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                raise UnsupportedVersion, version_data.to_s
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            end
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            return version, remainder
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        end
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        def decode_pdu(version, data)
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            pdu_tag, pdu_data, remainder = decode_tlv(data)
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            case pdu_tag
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            when GetRequest_PDU_TAG
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                pdu = PDU.decode(GetRequest, pdu_data)
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            when GetNextRequest_PDU_TAG
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                pdu = PDU.decode(GetNextRequest, pdu_data)
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            when Response_PDU_TAG
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                pdu = PDU.decode(Response, pdu_data)
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            when SetRequest_PDU_TAG
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                pdu = PDU.decode(SetRequest, pdu_data)
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            when SNMPv1_Trap_PDU_TAG
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                raise InvalidPduTag, "SNMPv1-trap not valid for #{version.to_s}" if version != :SNMPv1
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                pdu = SNMPv1_Trap.decode(pdu_data)
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            when GetBulkRequest_PDU_TAG
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                raise InvalidPduTag, "get-bulk not valid for #{version.to_s}" if version != :SNMPv2c
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                pdu = PDU.decode(GetBulkRequest, pdu_data)
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            when InformRequest_PDU_TAG
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                raise InvalidPduTag, "inform not valid for #{version.to_s}" if version != :SNMPv2c
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                pdu = PDU.decode(InformRequest, pdu_data)
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            when SNMPv2_Trap_PDU_TAG
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                raise InvalidPduTag, "SNMPv2c-trap not valid for #{version.to_s}" if version != :SNMPv2c
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                pdu = PDU.decode(SNMPv2_Trap, pdu_data)
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            else
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                raise UnsupportedPduTag, pdu_tag.to_s
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            end
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            return pdu, remainder
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        end
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    end
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    def initialize(version, community, pdu)
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        @version = version
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        @community = community
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        @pdu = pdu
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    end
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    def response
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        Message.new(@version, @community, Response.from_pdu(@pdu))
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    end
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    def encode_version(version)
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        if version == :SNMPv1
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            encode_integer(SNMP_V1)
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        elsif version == :SNMPv2c
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            encode_integer(SNMP_V2C)
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        else
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            raise UnsupportedVersion, version.to_s
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        end
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    end
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    def encode
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        data = encode_version(@version)
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        data << encode_octet_string(@community)
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        data << @pdu.encode
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        encode_sequence(data)
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    end
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end
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class PDU
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    attr_accessor :request_id
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    attr_accessor :error_index
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    attr_accessor :varbind_list
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    alias vb_list varbind_list
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    def self.decode(pdu_class, pdu_data)
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        request_id, remainder = decode_integer(pdu_data)
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        error_status, remainder = decode_integer(remainder)
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        error_index, remainder = decode_integer(remainder)
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        varbind_list, remainder = VarBindList.decode(remainder)
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        assert_no_remainder(remainder)
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        pdu_class.new(request_id, varbind_list, error_status, error_index)
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    end
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    ERROR_STATUS_NAME = {
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         0 => :noError,
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         1 => :tooBig,
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         2 => :noSuchName,
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         3 => :badValue,
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         4 => :readOnly,
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         5 => :genErr,
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         6 => :noAccess,
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         7 => :wrongType,
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         8 => :wrongLength,
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         9 => :wrongEncoding,
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        10 => :wrongValue,
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        11 => :noCreation,
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        12 => :inconsistentValue,
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        13 => :resourceUnavailable,
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        14 => :commitFailed,
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        15 => :undoFailed,
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        16 => :authorizationError,
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        17 => :notWritable,
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        18 => :inconsistentName
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    }
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    ERROR_STATUS_CODE = ERROR_STATUS_NAME.invert
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    def initialize(request_id, varbind_list, error_status=0, error_index=0)
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        @request_id = request_id
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        self.error_status = error_status
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        @error_index = error_index.to_int
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        @varbind_list = varbind_list
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    end
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    def error_status=(status)
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        @error_status = ERROR_STATUS_CODE[status]
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        unless @error_status
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            if status.respond_to?(:to_int) && ERROR_STATUS_NAME[status.to_int]
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                @error_status = status
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            else
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                raise InvalidErrorStatus, status.to_s
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            end
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        end
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    end
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    def error_status
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        ERROR_STATUS_NAME[@error_status]
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    end
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    def encode_pdu(pdu_tag)
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        pdu_data = encode_integer(@request_id)
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        pdu_data << encode_integer(@error_status)
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        pdu_data << encode_integer(@error_index)
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        pdu_data << @varbind_list.encode
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        encode_tlv(pdu_tag, pdu_data)
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    end
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    def each_varbind(&block)
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        @varbind_list.each(&block)
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    end
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end
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class GetRequest < PDU
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    def encode
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        encode_pdu(GetRequest_PDU_TAG)
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    end
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end
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class GetNextRequest < PDU
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    def encode
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        encode_pdu(GetNextRequest_PDU_TAG)
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    end
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end
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class SetRequest < PDU
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    def encode
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        encode_pdu(SetRequest_PDU_TAG)
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    end
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end
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class GetBulkRequest <  PDU
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    alias max_repetitions error_index
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    alias max_repetitions= error_index=
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    def encode
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        encode_pdu(GetBulkRequest_PDU_TAG)
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    end
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    def non_repeaters=(number)
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        @error_status = number
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    end
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    def non_repeaters
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        @error_status
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    end
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end
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class Response < PDU
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    class << self
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        def from_pdu(request)
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            Response.new(request.request_id, request.varbind_list,
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                :noError, 0)
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        end
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    end
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    def encode
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        encode_pdu(Response_PDU_TAG)
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    end
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end
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##
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# The PDU class for traps in SNMPv2c.  Methods are provided for retrieving
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# the values of the mandatory varbinds: the system uptime and the OID of the
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# trap.  The complete varbind list is available through the usual varbind_list
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# method.  The first two varbinds in this list will always be the uptime
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# and trap OID varbinds.
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#
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class SNMPv2_Trap < PDU
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    def encode
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        encode_pdu(SNMPv2_Trap_PDU_TAG)
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    end
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    ##
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    # Returns the source IP address for the trap, usually derived from the
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    # source IP address of the packet that delivered the trap.
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    # 
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    attr_accessor :source_ip
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    ##
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    # Returns the value of the mandatory sysUpTime varbind for this trap.
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    #
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    # Throws InvalidTrapVarbind if the sysUpTime varbind is not present.
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    #
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    def sys_up_time
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        varbind = @varbind_list[0]
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        if varbind && (varbind.name == SYS_UP_TIME_OID)
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            return varbind.value
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        else
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            raise InvalidTrapVarbind, "Expected sysUpTime.0, found " + varbind.to_s
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        end
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    end
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    ##
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    # Returns the value of the mandatory snmpTrapOID varbind for this trap.
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    #
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    # Throws InvalidTrapVarbind if the snmpTrapOID varbind is not present.
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    #
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    def trap_oid
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        varbind = @varbind_list[1]
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        if varbind && (varbind.name == SNMP_TRAP_OID_OID)
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            return varbind.value
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        else
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            raise InvalidTrapVarbind, "Expected snmpTrapOID.0, found " + varbind.to_s 
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        end
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    end
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end
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##
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# The PDU class for SNMPv2 Inform notifications.  This class is identical
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# to SNMPv2_Trap.
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#
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class InformRequest < SNMPv2_Trap
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    def encode
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        encode_pdu(InformRequest_PDU_TAG)
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    end
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end
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##
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# The PDU class for traps in SNMPv1.
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#
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class SNMPv1_Trap
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    ##
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    # Returns the source IP address for the trap, usually derived from the
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    # source IP address of the packet that delivered the trap.
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    # 
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    attr_accessor :source_ip
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    attr_accessor :enterprise
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    attr_accessor :agent_addr
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    attr_accessor :specific_trap
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    attr_accessor :timestamp
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    attr_accessor :varbind_list
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    alias :vb_list :varbind_list
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    def self.decode(pdu_data)
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        oid_data, remainder = decode_object_id(pdu_data)
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        enterprise = ObjectId.new(oid_data)
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        ip_data, remainder = decode_ip_address(remainder)
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        agent_addr = IpAddress.new(ip_data)
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        generic_trap, remainder = decode_integer(remainder)
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        specific_trap, remainder = decode_integer(remainder)
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        time_data, remainder = decode_timeticks(remainder)
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        timestamp = TimeTicks.new(time_data)
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        varbind_list, remainder = VarBindList.decode(remainder)
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        assert_no_remainder(remainder)
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        SNMPv1_Trap.new(enterprise, agent_addr, generic_trap, specific_trap,
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            timestamp, varbind_list)
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    end
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    def initialize(enterprise, agent_addr, generic_trap, specific_trap, timestamp, varbind_list)
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        @enterprise = enterprise
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        @agent_addr = agent_addr
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        self.generic_trap = generic_trap
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        @specific_trap = specific_trap
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        @timestamp = timestamp
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        @varbind_list = varbind_list 
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    end
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    # Name map for all of the generic traps defined in RFC 1157.
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    GENERIC_TRAP_NAME = {
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        0 => :coldStart,
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        1 => :warmStart,
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        2 => :linkDown,
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        3 => :linkUp,
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        4 => :authenticationFailure,
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        5 => :egpNeighborLoss,
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        6 => :enterpriseSpecific
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    }
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    # Code map for all of the generic traps defined in RFC 1157.
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    GENERIC_TRAP_CODE = GENERIC_TRAP_NAME.invert
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    def generic_trap=(trap)
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        @generic_trap = GENERIC_TRAP_CODE[trap]
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        unless @generic_trap
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            if trap.respond_to?(:to_i) && GENERIC_TRAP_NAME[trap.to_i]
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                @generic_trap = trap
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            else
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                raise InvalidGenericTrap, trap.to_s
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            end
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        end
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    end
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    def generic_trap
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        GENERIC_TRAP_NAME[@generic_trap]
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    end
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    def encode
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        pdu_data = @enterprise.encode <<
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                   @agent_addr.encode <<
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                   encode_integer(@generic_trap) <<
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                   encode_integer(@specific_trap) <<
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                   @timestamp.encode <<
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                   @varbind_list.encode
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        encode_tlv(SNMPv1_Trap_PDU_TAG, pdu_data)
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    end
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    def each_varbind(&block)
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        @varbind_list.each(&block)
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    end
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end
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end
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