# frozen_string_literal: true

# This file is part of PacketGen
# See https://github.com/sdaubert/packetgen for more informations
# Copyright (C) 2016 Sylvain Daubert <sylvain.daubert@laposte.net>
# This program is published under MIT license.

module PacketGen
  module PcapNG
    # {SPB} represents a Section Simple Packet Block (SPB) of a pcapng file.
    #
    # == Pcapng::SPB Definition
    #   Int32   :type           Default: 0x00000003
    #   Int32   :block_len
    #   Int32   :orig_len
    #   String  :data
    #   Int32   :block_len2
    # @author Sylvain Daubert
    class SPB < Block
      # Minimum SPB size
      MIN_SIZE = 4 * 4

      # @return [:little, :big]
      attr_accessor :endian
      # @return [IPB]
      attr_accessor :interface

      # @!attribute orig_len
      #  32-bit original length
      #  @return [Integer]
      define_field_before :block_len2, :orig_len, Types::Int32, default: 0
      # @!attribute data
      #  @return [Types::String]
      define_field_before :block_len2, :data, Types::String

      # @param [Hash] options
      # @option options [:little, :big] :endian set block endianness
      # @option options [Integer] :type
      # @option options [Integer] :block_len block total length
      # @option options [Integer] :orig_len actual length of the packet when it was
      #                                     transmitted on the network
      # @option options [::String] :data
      # @option options [::String] :options
      # @option options [Integer] :block_len2 block total length
      def initialize(options={})
        super
        endianness(options[:endian] || :little)
        recalc_block_len
        self.type = options[:type] || PcapNG::SPB_TYPE.to_i
      end

      # Has this block options?
      # @return [false]
      # @since 2.7.0
      def options?
        false
      end

      # Reads a String or a IO to populate the object
      # @param [::String,IO] str_or_io
      # @return [self]
      def read(str_or_io)
        io = to_io(str_or_io)
        return self if io.eof?

        self[:type].read io.read(4)
        self[:block_len].read io.read(4)
        self[:orig_len].read io.read(4)
        data_len = compute_data_len
        self[:data].read io.read(data_len)
        remove_padding(io, data_len)
        read_blocklen2_and_check(io)

        self.type ||= PcapNG::IDB_TYPE.to_i
        self
      end

      # Return the object as a String
      # @return [String]
      def to_s
        pad_field :data
        recalc_block_len
        super
      end

      private

      # Take care of IDB snaplen
      # CAUTION: snaplen == 0 -> no capture limit
      def compute_data_len
        if interface && interface.snaplen.to_i.positive?
          [self[:orig_len].to_i, interface.snaplen.to_i].min
        else
          self[:orig_len].to_i
        end
      end
    end
  end
end