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CREATE EXTENSION IF NOT EXISTS pgcrypto;

-- Based roughly on: https://github.com/oklog/ulid
CREATE FUNCTION generate_ulid()
RETURNS TEXT
AS $$
DECLARE
  -- Crockford's Base32
  encoding   BYTEA = '0123456789ABCDEFGHJKMNPQRSTVWXYZ';
  timestamp  BYTEA = E'\\000\\000\\000\\000\\000\\000';

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# https://en.wikipedia.org/wiki/List_of_IP_protocol_numbers
UDP_PROTOCOL = 0x11

loop do
  data = socket.recv(BUFFER_SIZE).bytes

  frame = EthernetFrame.new(data)

  next unless frame.ip_packet.protocol == UDP_PROTOCOL &&
    frame.ip_packet.udp_datagram.destination_port == 4321

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def body
  bytes[8, (length - 8)].pack('C*')
end

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class UDPDatagram
  def source_port
    word16(bytes[0], bytes[1])
  end
  
  def destination_port
    word16(bytes[2], bytes[3])
  end
  
  def length

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def udp_datagram
  UDPDatagram.new(bytes.drop(20))
end

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def source_ip_address
  bytes[14, 4].join('.')
end

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def ihl
  bytes[0] & 0xF
end

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class IPPacket
  attr_reader :bytes
  
  def initialize(bytes)
    @bytes = bytes
  end
  
  def version
    bytes[0] >> 4
  end

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def data
  # Drop the first 14 bytes (MAC Header) and last 4 bytes (CRC Checksum)
  IPPacket.new(bytes[14...-4])
end

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class EthernetFrame
  attr_reader :bytes

  def initialize(bytes)
    @bytes = bytes
  end

  def destination_mac
    format_mac(bytes[0, 6])
  end