#!/usr/bin/env ruby
#
# ==========================================================================
# koregusu0.1 -- version 0.0.99.20250906.4
#
# written by cleemy desu wayo / Licensed under CC0 1.0
#
# official repository: https://gitlab.com/cleemy-desu-wayo/koregusu0.1
# ==========================================================================
#
# * requirements:
#     * Ruby 3.0 or later
#

require 'digest'
require 'optparse'

class KRGS
  @@debug_mode = false

  def self.debug_mode?
    !!@@debug_mode
  end

  def self.debug_mode=(x)
    @@debug_mode = !!x
  end

  def self.exec_one_step(krgs_code, source)
    if krgs_code.is_a?(String)
      krgs_code.force_encoding("ASCII-8BIT")
    else
      raise "ERROR: krgs_code is not a String"
    end

    if source.is_a?(String)
      source.force_encoding("ASCII-8BIT")
    else
      raise "ERROR: source is not a String"
    end

    if @@debug_mode
      puts krgs_code
    end

    krgs_code_body = krgs_code.partition(":KRGS0.1:")

    checksum, param, later = krgs_code_body[2].partition(/\([^)]+\)/)

    if param == ""
      new_result = checksum
    else
      param_method, param_concat, param_remaining = param.sub(/[\(\)]/, "").split(",")

      if @@debug_mode
        puts "checksum:#{checksum} -- param: #{param} -- later: #{later} -- param_method:#{param_method} -- param_concat: #{param_concat} -- param_remaining : #{param_remaining}"
      end
  
      # generate a string to pass to the hash function
      key_str = ""
      param_concat.each_char do |tag|
        case tag
        when "k"
          key_str += krgs_code
        when "r"
          if checksum == ""
            key_str += source
          else
            key_str += checksum
          end
        when "R"
          if checksum == ""
            if source =~ /\A[0-9a-f]+\z/
              key_str += [source].pack("H*")
            end
          elsif checksum =~ /\A[0-9a-f]+\z/
            key_str += [checksum].pack("H*")
          end
        when "s"
          key_str += source
        when "S"
          if source =~ /\A[0-9a-f]+\z/
            key_str += [source].pack("H*")
          end
        end
      end

      case param_method
      when "s256"
        new_checksum = Digest::SHA256.hexdigest(key_str)
      when "s512"
        new_checksum = Digest::SHA512.hexdigest(key_str)
      when "copy"
        new_checksum = key_str
      when "rev"
        new_checksum = key_str.reverse
      when "REV"
        new_checksum = key_str.scan(/.{1,2}/).reverse.join
      end

      new_param = ""
      new_later = ""
      if param_remaining.to_i > 1
        new_param = "(#{param_method},#{param_concat},#{param_remaining.to_i - 1})"
        new_later = later
      else
        if later.start_with?("(")
          new_later = later
        end
      end
  
      new_result = "#{krgs_code_body[0]}#{krgs_code_body[1]}#{new_checksum}#{new_param}#{new_later}"
    end

    new_result
  end

  def self.exec(krgs_code, source)
    result = krgs_code

    step = 1
    loop do
      if @@debug_mode
        puts "step:#{step}"
      end

      result = exec_one_step(result, source)

      if @@debug_mode
        puts result
        puts "--"
      end

      break unless result =~ /:KRGS0.1:/
      step += 1
    end

    result
  end
end

if $0 == __FILE__

  opts = OptionParser.new

  krgs_code   = nil
  source      = nil
  source_file = nil

  opts.on("--debug")                         { KRGS.debug_mode = true }
  opts.on("-e CODE")                         { |optvalue| krgs_code = optvalue }
  opts.on("--source SOURCE", "--key SOURCE") { |optvalue| source = optvalue }
  opts.on("--source-file SOURCE_FILE")       { |optvalue| source_file = optvalue ; source = File.binread(source_file) }

  opts.parse!(ARGV)

  if krgs_code
    puts KRGS.exec(krgs_code, source)
  else
    raise "ERROR: lack of KRGS code"
  end

end