puzzle-solver.rb

require 'optparse'
require 'pathname'
require 'open3'
require 'ripper'
require 'etc'
require 'timeout'

def valid_syntax?(code)
  Ripper.sexp(code)
end

def sh(*cmd)
  Open3.capture3(*cmd).then do |out, _err, status|
    out if status.success?
  end
end

def solve(code:, ch:, result:, pos:)
  Timeout.timeout(TIMEOUT_SEC) do
    code = code.dup
    code.insert pos, ch
    return nil unless valid_syntax?(code)

    if sh('ruby', '-e', code) == result
      [ch, pos]
    end
  end
rescue Timeout::Error
  nil
end


opt = ARGV.getopts('result:', 'timeout:')
result = opt['result'] || "Hello world\n"
TIMEOUT_SEC = opt['timeout']&.to_i || 3
ruby_code = Pathname(ARGV.first).read

in_q = Queue.new
out_q = Queue.new

# TODO: null byte
(1..0xff).each do |i|
  ch = i.chr
  (ruby_code.size + 1).times do |pos|
    in_q.push(code: ruby_code, ch: ch, result: result, pos: pos)
  end
end

in_q.close

ths = Etc.nprocessors.times.map do
  Thread.new do
    loop do
      v = in_q.pop
      break unless v
      ret = solve(**v)
      next unless ret
      out_q.push ret
    end
  end
end

ths.each(&:join)
out_q.close

while ret = out_q.pop
  p ret
end