simple debugging proxy for nrepl

nrepl-proxy.rb

#!/usr/bin/env ruby

require 'bencode'
require 'edn'
require 'socket'

if ARGV.length < 3
  puts "usage: #{$0} <source-port> <dest-host> <dest-port>"
  exit
end

sport, dhost, dport = ARGV

puts "Listening on #{sport}, proxying to #{dhost}:#{dport}"
server = TCPServer.open('127.0.0.1', sport.to_i)

def decode_message(message)
  decoded_stream = BEncode::Parser.new(StringIO.new(message.chomp))
  out = []
  until decoded_stream.eos?
    out << decoded_stream.parse!.to_edn
  end
  out.join "\n    "
end

loop do
  source = server.accept
  dest = TCPSocket.new(dhost, dport)

  block_size = 32768

  loop do
    ready = select([source, dest], nil, nil)
    if ready[0].include?(source)
      data = source.recv(block_size)
      if data.empty?
        puts "closed at local end"
        break
      end
      puts " => #{decode_message(data)}"
      dest.write(data)
    end
    if ready[0].include?(dest)
      data = dest.recv(block_size)
      if data.empty?
        puts "closed at remote end"
        break
      end
      puts "<=  #{decode_message(data)}"
      source.write(data)
    end
  end
end