partial_http_get.rb

require "net/http"

A_CHUNK_TOO_FAR = Class.new(StandardError)

# @param url [URI] uri to fetch title of
def url_title(url)
  title = nil

  Net::HTTP.start(url.host, url.port, use_ssl: (url.scheme == "https"), open_timeout: 5, read_timeout: 5) do |http|
    request = Net::HTTP::Get.new(url)

    http.request(request) do |response|
      bytes_read = 0

      response.read_body do |chunk|
        raise(A_CHUNK_TOO_FAR) if bytes_read > 16_000

        title = chunk[%r{<title>([^<]+)</title>}m, 1]&.strip
        raise(A_CHUNK_TOO_FAR) if title

        bytes_read += chunk.size
      end
    end

    nil
  end

rescue A_CHUNK_TOO_FAR
  title
end

url_title(URI("https://caiustheory.com")) # => "Latest - CaiusTheory"
url_title(URI("https://google.com")) # => nil
url_title(URI("http://zomgsexandporn.caius.name/2020-08-18-desk.jpeg")) # => nil