# 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.

# frozen_string_literal: true

module PacketGen
  module Header
    class TCP

      # Container for TCP options in {TCP TCP header}.
      # @author Sylvain Daubert
      class Options < Types::Array

        # Get {Option} subclasses
        # @return [Array<Class>]
        def self.option_classes
          return @klasses if defined? @klasses
          @klasses = []
          Option.constants.each do |cst|
            next unless cst.to_s.end_with? '_KIND'
            optname = cst.to_s.sub(/_KIND/, '')
            @klasses[Option.const_get(cst)] = TCP.const_get(optname)
          end
          @klasses
        end

        # Read TCP header options from a string
        # @param [String] str binary string
        # @return [self]
        def read(str)
          clear
          return self if str.nil?
          PacketGen.force_binary str

          i = 0
          klasses = self.class.option_classes
          while i < str.to_s.length
            kind = str[i, 1].unpack('C').first
            this_option = if klasses[kind].nil?
                            Option.new
                          else
                            klasses[kind].new
                          end
            this_option.read str[i, str.size]
            unless this_option.has_length?
              this_option.length = nil
              this_option.value = nil
            end
            self << this_option
            i += this_option.sz
          end
          self
        end

        # @deprecated use {#push} or {#<<}
        # Add a well-known option
        # @param [String] opt option name
        # @param [Object] value
        # @return [self]
        # @raise [ArgumentError] unknown option
        def add(opt, value=nil)
          option = record_from_hash(opt: opt, value: value)
          self << option
          self
        end

        private

        def record_from_hash(hsh)
          if hsh.has_key? :opt
            klassname = hsh.delete(:opt)
            if TCP.const_defined?(klassname)
              klass = TCP.const_get(klassname)
              unless klass < Option
                raise ArgumentError, 'opt should be a TCP::Option subclass'
              end
              klass.new(hsh)
            else
              raise ArgumentError, 'opt should be a TCP::Option subclass'
            end
          else
            hsh
          end
        end
      end
    end
  end
end

require_relative 'option'