bf.rb

# frozen_string_literal: true

require 'socket'

class Op
  attr_accessor :op, :val

  def initialize(op, val)
    @op = op
    @val = val
  end
end

class Tape
  def initialize
    @tape = [0]
    @pos = 0
  end

  def get
    @tape[@pos]
  end

  def inc(x)
    @tape[@pos] += x
  end

  def move(x)
    @pos += x
    @tape << 0 while @pos >= @tape.size
  end
end

class Printer
  attr_reader :quiet

  def initialize(quiet)
    @sum1 = 0
    @sum2 = 0
    @quiet = quiet
  end

  def print(n)
    if @quiet
      @sum1 = (@sum1 + n) % 255
      @sum2 = (@sum2 + @sum1) % 255
    else
      $stdout.print(n.chr)
    end
  end

  def checksum
    (@sum2 << 8) | @sum1
  end
end

class Program
  def initialize(code, p)
    @ops = parse code.chars.each
    @p = p
  end

  def run
    _run @ops, Tape.new
  end

  private

  def _run(program, tape)
    program.each do |op|
      case op.op
      when :inc then tape.inc(op.val)
      when :move then tape.move(op.val)
      when :loop then _run(op.val, tape) while tape.get.positive?
      when :print then @p.print(tape.get)
      end
    end
  end

  def parse(iterator)
    res = []
    while (c = iterator.next rescue nil)
      op = case c
           when '+' then Op.new(:inc, 1)
           when '-' then Op.new(:inc, -1)
           when '>' then Op.new(:move, 1)
           when '<' then Op.new(:move, -1)
           when '.' then Op.new(:print, 0)
           when '[' then Op.new(:loop, parse(iterator))
           when ']' then break
           end
      res << op if op
    end
    res
  end
end

def notify(msg)
  Socket.tcp('localhost', 9001) { |s| s.puts msg }
rescue SystemCallError
  # standalone usage
end

def verify
  text = '++++++++[>++++[>++>+++>+++>+<<<<-]>+>+>->>+[<]<-]>>.>' \
         '---.+++++++..+++.>>.<-.<.+++.------.--------.>>+.>++.'
  p_left = Printer.new(true)
  Program.new(text, p_left).run
  left = p_left.checksum

  p_right = Printer.new(true)
  "Hello World!\n".each_char { |c| p_right.print(c.ord) }

  right = p_right.checksum
  return unless left != right

  warn "#{left} != #{right}"
  exit(1)
end

if __FILE__ == $PROGRAM_NAME
  verify

  engine = RUBY_ENGINE
  if engine == 'truffleruby'
    desc = RUBY_DESCRIPTION
    if desc.include?('Native')
      engine = 'Ruby/truffleruby'
    elsif desc.include?('JVM')
      engine = 'Ruby/truffleruby (JVM)'
    end
  elsif engine == 'ruby' && RubyVM::RJIT.enabled?
    engine = 'Ruby (--jit)'
  end

  text = File.read(ARGV[0])
  p = Printer.new(ENV.key?('QUIET'))

  notify("#{engine}\t#{Process.pid}")
  Program.new(text, p).run
  notify('stop')

  puts "Output checksum: #{p.checksum}" if p.quiet
end