# This is a sample class that you'll probably need
# to do a bit of work on for your own needs, but it
# will hopefully save you a lot of the headaches that we had

class AwsMove
  FIVE_MB = 5 * 1024 * 1024
  MAX_THREADS = 25

  def move_folder(s3_client, old_key, new_key)
    # strip preceding '/'
    sanitized_old_key = old_key.sub(/\A\//, "")
    if params[:mode] == 'rename'
      sanitized_new_key = new_key.sub(/\A\//, "")
    else
      sanitized_new_key = new_key
    end

    t1 = Time.now
    Rails.logger.info "Moving"
    moves = []

    objects = s3_client.list_objects_v2(bucket: bucket_name, prefix: sanitized_old_key, encoding_type: 'url')

    loop do
      objects.contents.each do |object|
        from_key = CGI::unescape(object.key)
        to_key = from_key.sub(sanitized_old_key, sanitized_new_key)
        multipart_copy = object.size > FIVE_MB
        moves << [from_key, to_key, multipart_copy]
      end
      break unless objects.next_page?
      objects = objects.next_page
    end

    elapsed_ms = ((Time.now - t1) * 1000).to_i
    Rails.logger.info "Identified #{moves.count} AWS objects. Total elapsed = #{elapsed_ms}ms"

    # move files and subfolders before their parent folder
    moves.sort_by! { |move| -move[0].length }
    queue = moves.inject(Queue.new, :push)
    thread_count = [MAX_THREADS, moves.length].min

    threads = Array.new(thread_count) do
      Thread.new do
        begin
          while move = queue.pop(true)
            from_key, to_key, multipart_copy = move
            s3_object(s3_client, from_key).move_to(bucket: bucket_name, key: to_key, multipart_copy: multipart_copy)
          end
        rescue ThreadError
          # caught if the queue is empty, or if we are out of memory to generate a new thread
        end
      end
    end
    threads.each(&:join)

    elapsed_ms = ((Time.now - t1) * 1000).to_i
    Rails.logger.info "Moved files. Total elapsed = #{elapsed_ms}ms"

  end
end