kvs.rb

# frozen_string_literal: true

class SimpleKvs # :nodoc:
  def self.call(file_name)
    raf = File.open(file_name, 'r+')
    new(raf)
  end

  def initialize(raf)
    @raf = raf
  end

  def set(key, value)
    raf.seek(0, IO::SEEK_END)
    raf.write("#{key}\t")
    raf.write("#{Marshal.dump(value)}\n")
    nil
  end

  def get(key)
    line = seek(key)
    return unless line
    Marshal.load(line.split("\t").last) # rubocop:disable Security/MarshalLoad
  end

  private

  attr_reader :raf

  def seek(key)
    raf.rewind
    raf.readlines.reverse.find { |i| i.start_with?("#{key}\t") }
  end
end

def main
  name = './db.txt'
  File.write(name, '') unless File.exist?(name)
  kvs = SimpleKvs.call(name)
  kvs.set('k', 1)
  kvs.set('s', 2)
end

if File.identical?(__FILE__, $PROGRAM_NAME)
  require 'minitest/spec'
  require 'minitest/autorun'
  require 'stringio'
  describe SimpleKvs do
    let(:kvs) { SimpleKvs.new(StringIO.new) }
    it 'set and get' do
      kvs.set('k', 1)
      kvs.set('s', 2)
      _(kvs.get('k')).must_equal 1
      _(kvs.get('s')).must_equal 2
      kvs.set('k', 3)
      _(kvs.get('k')).must_equal 3
    end
  end
end