require 'rubygems'
require 'bindata'
require 'readline'

class VirtualMachine
    def self.debug=(debug = false)
        @@debug = debug
    end

    def self.run bytecode
        cells = Array.new
        @plus     = 0x1
        @minus    = 0x2
        @next     = 0x3
        @previous = 0x4
        @read     = 0x5
        @print    = 0x6
        cell  = 0
        ip    = 0
        while not bytecode.size == ip
            if cells[cell].nil?
                cells[cell] = 0
            end

            case bytecode[ip]
            when @plus
                cells[cell] += 1
            when @minus
                cells[cell] -= 1
            when @next
                cell += 1
            when @previous
                cell -= 1
            when @read
                cells[cell] = Readline.readline('',true).chomp.to_i
            when @print
                print cells[cell].chr
            end
            ip += 1
        end
    end
end

VirtualMachine.debug = true
ARGV.each do |file_name|
    if not File.exist? file_name
        puts "File #{file_name} doesn't exist!"
        exit 1
    end
    bytecode = Array.new
    File.open(file_name) do |file|
        file.each_byte do |ch|
            bytecode[bytecode.size] = ch
        end
    end
    VirtualMachine.run bytecode
end