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# -*- coding: binary -*-
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module Rex
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module Proto
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module Kademlia
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  # Opcode for a bootstrap response
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  BOOTSTRAP_RESPONSE = 0x09
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  # A Kademlia bootstrap response message
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  class BootstrapResponse < Message
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    # @return [String] the ID of the peer that send the bootstrap response
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    attr_reader :peer_id
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    # @return [Integer] the TCP port that the responding peer is listening on
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    attr_reader :tcp_port
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    # @return [Integer] the version of this peer
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    attr_reader :version
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    # @return [Array<Hash<String, Object>>] the peer ID, IP address, UDP/TCP ports and version of each peer
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    attr_reader :peers
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    # Constructs a new bootstrap response
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    #
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    # @param peer_id [String] the ID of this peer
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    # @param tcp_port [Integer] the TCP port that this peer is listening on
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    # @param version [Integer] the version of this peer
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    # @param peers [Array<Hash<String, Object>>] the peer ID, IP address, UDP/TCP ports and version of each peer
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    def initialize(peer_id, tcp_port, version, peers)
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      @peer_id = peer_id
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      @tcp_port = tcp_port
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      @version = version
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      @peers = peers
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    end
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    # The minimum size of a peer in a KADEMLIA2_BOOTSTRAP_RES message:
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    # peer ID (16-bytes), IP (4 bytes), UDP port (2 bytes), TCP port (2 bytes)
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    # and version (1 byte)
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    BOOTSTRAP_PEER_SIZE = 25
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    # Builds a bootstrap response from given data
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    #
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    # @param data [String] the data to decode
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    # @return [BootstrapResponse] the bootstrap response if the data is valid, nil otherwise
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    def self.from_data(data)
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      message = Message.from_data(data)
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      # abort if this isn't a valid response
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      return unless message
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      return unless message.type == BOOTSTRAP_RESPONSE
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      return unless message.body.size >= 23
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      bootstrap_peer_id = Rex::Proto::Kademlia.decode_peer_id(message.body.slice!(0, 16))
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      bootstrap_tcp_port, bootstrap_version, num_peers = message.body.slice!(0, 5).unpack('vCv')
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      # protocol says there are no peers and the body confirms this, so just return with no peers
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      if num_peers == 0 && message.body.to_s.strip.empty?
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        peers = []
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      else
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        peers_data = message.body
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        # peers data is too long/short, abort
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        return if peers_data.size % BOOTSTRAP_PEER_SIZE != 0
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        peers = []
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        until peers_data.to_s.strip.empty?
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          peer_data = peers_data.slice!(0, BOOTSTRAP_PEER_SIZE)
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          peer_id = Rex::Proto::Kademlia.decode_peer_id(peer_data.slice!(0, 16))
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          ip, udp_port, tcp_port, version = peer_data.unpack('VvvC')
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          peers << {
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            id: peer_id,
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            ip: Rex::Socket.addr_itoa(ip),
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            tcp_port: tcp_port,
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            udp_port: udp_port,
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            version: version
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          }
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        end
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      end
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      BootstrapResponse.new(bootstrap_peer_id, bootstrap_tcp_port, bootstrap_version, peers)
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    end
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  end
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end
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end
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end
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