Simple file search in Ruby

search.rb

class String
  def triads()
    string = self.clone
    Enumerator.new do |y|
      while string.size > 2
        y << string.slice(0, 3)
        string.slice!(0)
      end
    end
  end
end

class Tokenizer
  def initialize(content)
    @content = content
  end

  def triads
    @content.gsub(/[^[:alnum:].:_]+/, ' ').split(' ').map(&:triads).map(&:to_a).flatten
  end
end

class FileMatcher

  def initialize(paths)
    @db = build_db(paths)
  end

  def files_for_query(string)
    triads = Tokenizer.new(string).triads
    files = @db[triads.shift].to_a

    triads.inject(files){ |old_values, triad|
      old_values.map{ |path, line_num, index| [path, line_num, index + 1] } & @db[triad]
    }.map{ |o, line_num, _| [o, line_num] }.uniq
  end

  private

  def build_db(paths)
    storage = Hash.new{ |h,k| h[k] = [] }
    paths.each do |path|
      content = IO.readlines(path).map(&:chomp).map{ |s| s.force_encoding('utf-8') }
      content.each_with_index do |line, line_num|
        Tokenizer.new(line).triads.each_with_index{ |triad, index| storage[triad] << [path, line_num, index] }
      end
    end
    storage
  end

end

class FileIndex
  def initialize(paths)
    @index = build_index(paths)
  end

  def get_line(path, line)
    @index[path][line]
  end

  private

  def build_index(paths)
    paths.inject({}) do |acc, path|
      lines = IO.readlines(path).map(&:chomp).map{ |s| s.force_encoding('utf-8') }
      acc[path] = Hash[lines.each_with_index.to_a.map(&:reverse)]
      acc
    end
  end

end

class Engine

  def search(string)
    @file_matcher.files_for_query(string).map do |path_line|
      line_content = @file_index.get_line(*path_line)
      if line_content =~ /#{string}/
        path_line.push(line_content)
      else
        nil
      end
    end.compact
  end

  def initialize(path, extensions)
    @paths = get_paths(path, extensions)
    @file_matcher = FileMatcher.new(@paths)
    @file_index = FileIndex.new(@paths)
  end


  def get_paths(path, extensions)
    extensions_part = extensions.map{ |o| "-name '*#{o}'" }.join(' -or ')
    `find #{path} #{extensions_part}`.split("\n")
  end

end

class Server

  def parse_command
    line = $stdin.readline.chomp
    command, arguments = line.split(' ', 2)
    if commands.include?(command)
      self.send(command, arguments)
    else
      puts "ERROR: no such command: #{command}"
    end

  end

  private

  def commands;  %w[init search]; end

  def init(arguments)
    path, *extensions_part = arguments.split(' ')
    @engine = Engine.new('data', ['.rb'])
    puts 'ok'
  end

  def search(arguments)
    if @engine
      results = @engine.search(arguments)
      puts results.map{ |file, line, string| "#{file}:#{line} #{string}"}
      puts "ok"
    else
      puts "ERROR: you need to issue init first."
    end
  end
end


@server = Server.new
@server.parse_command while true