# -*- coding: binary -*-

module Rex
  module Proto
    module Kerberos
      module Model
        # This class provides a representation of a Kerberos EncryptionKey data
        # definition
        class EncryptionKey < Element

          # @!attribute key
          #   @return [Fixnum] The type of encryption key
          attr_accessor :type
          # @!attribute value
          #   @return [String] the key itself
          attr_accessor :value

          # Decodes a Rex::Proto::Kerberos::Model::EncryptionKey
          #
          # @param input [String, OpenSSL::ASN1::Sequence] the input to decode from
          # @return [self] if decoding succeeds
          # @raise [RuntimeError] if decoding doesn't succeed
          def decode(input)
            case input
            when String
              decode_string(input)
            when OpenSSL::ASN1::Sequence
              decode_asn1(input)
            else
              raise ::RuntimeError, 'Failed to decode EncryptionKey, invalid input'
            end

            self
          end

          # Encodes a Rex::Proto::Kerberos::Model::EncryptionKey into an
          # ASN.1 String
          #
          # @return [String]
          def encode
            elems = []
            elems << OpenSSL::ASN1::ASN1Data.new([encode_type], 0, :CONTEXT_SPECIFIC)
            elems << OpenSSL::ASN1::ASN1Data.new([encode_value], 1, :CONTEXT_SPECIFIC)
            seq = OpenSSL::ASN1::Sequence.new(elems)

            seq.to_der
          end

          private

          # Decodes a Rex::Proto::Kerberos::Model::EncryptionKey from an String
          #
          # @param input [String] the input to decode from
          def decode_string(input)
            asn1 = OpenSSL::ASN1.decode(input)

            decode_asn1(asn1)
          end

          # Decodes a Rex::Proto::Kerberos::Model::EncryptionKey from an
          # OpenSSL::ASN1::Sequence
          #
          # @param input [OpenSSL::ASN1::Sequence] the input to decode from
          def decode_asn1(input)
            seq_values = input.value
            self.type = decode_type(seq_values[0])
            self.value = decode_value(seq_values[1])
          end

          # Decodes the type from an OpenSSL::ASN1::ASN1Data
          #
          # @param input [OpenSSL::ASN1::ASN1Data] the input to decode from
          # @return [Fixnum]
          def decode_type(input)
            input.value[0].value.to_i
          end

          # Decodes the value from an OpenSSL::ASN1::ASN1Data
          #
          # @param input [OpenSSL::ASN1::ASN1Data] the input to decode from
          # @return [String]
          def decode_value(input)
            input.value[0].value
          end

          # Encodes the type field
          #
          # @return [OpenSSL::ASN1::Integer]
          def encode_type
            bn = OpenSSL::BN.new(type.to_s)
            int = OpenSSL::ASN1::Integer.new(bn)

            int
          end

          # Encodes the value field
          #
          # @return [OpenSSL::ASN1::OctetString]
          def encode_value
            OpenSSL::ASN1::OctetString.new(value)
          end
        end
      end
    end
  end
end