#!/usr/bin/env ruby

require_relative "program"

NUM_PROGRAMS = 100
EXPECTED_OUTPUT = "HELLOWORLD"

def ord(chr)
  chr.unpack("C").first
end

def grade_program(p)
  output = p.execute
  grade = (EXPECTED_OUTPUT.size - output.size).abs * 100
  [EXPECTED_OUTPUT.size, output.size].min.times do |i|
    grade += (ord(EXPECTED_OUTPUT[i]) - ord(output[i])).abs * 10
  end
  grade + p.length
end

def main
  programs = NUM_PROGRAMS.times.map do
    p = Program.new
    [grade_program(p), p]
  end
  generation = 0
  begin
    last_best = nil
    while true
      generation += 1
      programs += programs.map do |grade, p|
        p2 = p.clone
        p2.mutate
        [grade_program(p2), p2]
      end
      programs.uniq!
      programs.sort! do |a, b|
        a.first <=> b.first
      end
      programs = programs.take(NUM_PROGRAMS)
      if last_best.nil? or programs.first.first < last_best
        last_best = programs.first.first
        $stdout.write("\rGrade: #{last_best}, output: #{programs.first.last.execute.inspect}                    ")
      end
      if programs.first.first == 0
        puts
        puts "Program found after #{generation} generations:"
        puts programs.first.last
        break
      end
    end
  rescue Interrupt
    puts
    puts "Canceled at #{generation} generations"
    puts "The best program (grade #{programs.first.first}) is:"
    puts programs.first.last
  end
end

main