module FileStore

  class BaseStore

    def store_upload(file, upload, content_type = nil)
      path = get_path_for_upload(upload)
      store_file(file, path)
    end

    def store_optimized_image(file, optimized_image)
      path = get_path_for_optimized_image(optimized_image)
      store_file(file, path)
    end

    def store_file(file, path, opts = {})
      not_implemented
    end

    def remove_upload(upload)
      remove_file(upload.url, get_path_for_upload(upload))
    end

    def remove_optimized_image(optimized_image)
      remove_file(optimized_image.url, get_path_for_optimized_image(optimized_image))
    end

    def remove_file(url, path)
      not_implemented
    end

    def has_been_uploaded?(url)
      not_implemented
    end

    def download_url(upload)
      not_implemented
    end

    def cdn_url(url)
      not_implemented
    end

    def absolute_base_url
      not_implemented
    end

    def relative_base_url
      not_implemented
    end

    def external?
      not_implemented
    end

    def internal?
      !external?
    end

    def path_for(upload)
      not_implemented
    end

    def download(upload)
      DistributedMutex.synchronize("download_#{upload.sha1}") do
        filename = "#{upload.sha1}#{File.extname(upload.original_filename)}"
        file = get_from_cache(filename)

        if !file
          max_file_size_kb = [SiteSetting.max_image_size_kb, SiteSetting.max_attachment_size_kb].max.kilobytes
          url = SiteSetting.scheme + ":" + upload.url
          file = FileHelper.download(
            url,
            max_file_size: max_file_size_kb,
            tmp_file_name: "discourse-download",
            follow_redirect: true
          )
          cache_file(file, filename)
        end

        file
      end
    end

    def purge_tombstone(grace_period)
    end

    def get_depth_for(id)
      [0, Math.log(id / 1_000.0, 16).ceil].max
    end

    def get_path_for(type, id, sha, extension)
      depth = get_depth_for(id)
      tree = File.join(*sha[0, depth].split(""), "")
      "#{type}/#{depth + 1}X/#{tree}#{sha}#{extension}"
    end

    def get_path_for_upload(upload)
      get_path_for("original".freeze, upload.id, upload.sha1, upload.extension)
    end

    def get_path_for_optimized_image(optimized_image)
      upload = optimized_image.upload
      extension = "_#{OptimizedImage::VERSION}_#{optimized_image.width}x#{optimized_image.height}#{optimized_image.extension}"
      get_path_for("optimized".freeze, upload.id, upload.sha1, extension)
    end

    CACHE_DIR ||= "#{Rails.root}/tmp/download_cache/"
    CACHE_MAXIMUM_SIZE ||= 500

    def get_cache_path_for(filename)
      "#{CACHE_DIR}#{filename}"
    end

    def get_from_cache(filename)
      path = get_cache_path_for(filename)
      File.open(path) if File.exists?(path)
    end

    def cache_file(file, filename)
      path = get_cache_path_for(filename)
      dir = File.dirname(path)
      FileUtils.mkdir_p(dir) unless Dir[dir].present?
      FileUtils.cp(file.path, path)
      # keep latest 500 files
      `ls -tr #{CACHE_DIR} | head -n +#{CACHE_MAXIMUM_SIZE} | xargs rm -f`
    end

    private

    def not_implemented
      raise "Not implemented."
    end

  end

end