require 'drb/drb'
require 'rinda/rinda'  ##
require 'nqueen'

class NQEngine
  def initialize(ts)
    @ts = ts
  end

  def main_loop
    while true
      sym, key, size, board, row, stream = take_request
      begin
        p [key, row] if $DEBUG
        do_it(key, size, board, row, stream)
      rescue
      ensure
        write_done(key)
      end
    end
  end

  def do_it(key, size, board, row, stream)
    NQueen.nqueen(size, board, row) do |x|
      stream.push(x)
    end
  end

  def take_request
    @ts.take([:nqueen, nil, Integer, Array, Integer, nil])
  end

  def write_done(key, timeout=30)
    @ts.write([:nqueen_done, key], timeout)
  end
end

if __FILE__ == $0
  DRb.start_service

  ts_uri = ARGV.shift || raise
  ts = DRbObject.new(nil, ts_uri)

  engine = NQEngine.new(Rinda::TupleSpaceProxy.new(ts)) ##
  engine.main_loop
end