thread_4_01.rb

require 'time'

module HashGenerator
  # calculating hash for string "#{string}#{number}"
  def self.call(string, number)
    # for macOS
    return `echo '#{string}#{number}' | sha2 -256`
      .gsub('SHA-256 ((null)) = ', '')
      .gsub(/\n/, '')
    # for Linux
    # return `echo '#{string}#{number}' | sha256sum`.gsub(/\s\s\-$/, '')
  end
end

module HashChecker
  # check does hash start with corrent numbers
  def self.call(hash_str, zero_count)
    hash_start = hash_str[0..(zero_count - 1)]
    hash_start == ('0' * zero_count)
  end
end

module TimeSplitter
  # prepare time format for output
  def self.call(time_start, time_end)
    seconds = ((time_end - time_start)).round
    minutes = ((time_end - time_start) / 60).round
    [minutes, seconds]
  end
end

# class for calculcation
# it takes main string and number of leading zeros
class MainMachine
  attr_reader :main_string, :zero_count

  def initialize(main_string, zero_count)
    @main_string = main_string
    @zero_count = zero_count
  end

  def perform
    time_start = Time.now
    number = 0
    sha_hash = ''

    # infinity loop
    loop do
      # generate hash
      sha_hash = HashGenerator.call(main_string, number)

      # check is hash valid
      if HashChecker.call(sha_hash, zero_count) == true
        # break loop if hash is valid
        break
      end

      # increase number for another iteration
      number += 1
    end

    # output
    time_end = Time.now
    minutes, seconds = TimeSplitter.call(time_start, time_end)
    puts "\n\rstring: '#{main_string}'"
    puts "number: '#{number}'"
    puts "hash: '#{sha_hash}'"
    puts "time: '#{minutes}'(minutes), '#{seconds}'(seconds)"
  end
end


main_string = 'hello world!'
number_of_leading_zeros = 3
MainMachine.new(main_string, number_of_leading_zeros).perform