readme.md

As a user of bit.ly, I wish I could determine when a bit.ly URL could be used. For example, I have a cute kitten website with a special offer that I want to link to, but the bit.ly link for it shouldn't work until a specified date.

• I'd like to name my modified bit.ly service later.ly

• http://awesomesauce.com/specialoffer becomes - http://later.ly/

• Can set an available to open date for http://later.ly/

• Set once when the link is created (required)

• Can also set an expire date for http://later.ly/

  • Set once when the link is created (optional)

• If URL is accessed outside of acceptable date range it should be handled

First version: Depend on URI underneath as consistent type to operate on from function to function. Use Digest/SHA1 to create guid for path.

Second version: Provide a real url shortener using base32. Base32 provides a more human readable encoding and excludes I L O U which should keep us safe from any cuss words leaking in once we get to ROFLSCALE. Based on ideas in this SO post: http://stackoverflow.com/questions/742013/how-to-code-a-url-shortener

bitly.rb

require 'uri'
require 'digest/sha1'

class BitlyURLRewriter
  DOMAIN = "later.ly"

  def update_domain(url)
    URI.parse(url).tap { |uri| uri.host = "later.ly" }
  end

  # Generate a guid via secure digest of message (path)
  # Should use md5 since sha1 isn't very secure anyhow and 
  # it's slower than md5
  #
  def obfuscate_url(uri)
    uri.tap {|uri| uri.path = "/#{Digest::SHA1.base64digest uri.path}" }
  end

  # logic to see if date has passed either opening or closing date
  # validates input likely Date.parse will work
  #
  def check_available(date)
  end
end

bitly2.rb

require 'uri'

module DB
  @@urls = {}

  def self.urls
    @@urls
  end

  def self.reset!
    @@urls = {}
  end
end

class BitlyURLRewriter
  DOMAIN = "later.ly"

  # Update the host to the new host
  #
  # @param url [String]
  # @returns [URI] uri with modified host
  #
  def update_host(url)
    URI.parse(url).tap { |uri| uri.host = "later.ly" }
  end

  # Insert url into db
  #
  # @param url [String] original url to store in db
  # @returns [String] url
  # @returns [Fixnum] pk of inserted url
  # @returns [nil] nil for pk if none inserted
  #
  def insert(url)
    pk = Random.rand(10000)
    uri = update_host(url)
    DB::urls[pk] = uri.to_s
    return uri, pk
  end

  # Find url to redirect to given encoded url
  #   @param url [URI,String] encoded url either URI or string
  #   @returns [String] original url inserted into db
  #
  def find(url)
    path = if url.respond_to?(:path)
              url.path
           else
             URI.parse(url).path
           end
    path.gsub!(/\//, "")
    DB::urls[decode_path(path)]
  end

  # Modify path of uri with encoded pk
  #
  #   @param uri [URI]
  #   @param pk [Fixnum]
  #   @return [URI] URI with path updated
  #
  def encode_uri(uri, pk)
    uri.tap { |uri| uri.path = "/#{encode_pk(pk)}" }
  end

  # Convert base32 back to base10 (pk)
  #
  def decode_path(path)
    path.to_i(32)
  end

  # Convert pk to base32
  #
  def encode_pk(pk)
    pk.to_s(32)
  end

  # logic to see if date has passed either opening or closing date
  # validates input likely Date.parse will work
  #
  def check_available(date)
  end
end

bitly2_test.rb

require 'minitest/autorun'
require_relative './bitly'

class BitlyURLRewriterTest < Minitest::Test
  def setup
    DB::reset!
    @url = "http://awesomesauce.com/specialoffer"
    @rewriter = BitlyURLRewriter.new
    @uri, @pk = @rewriter.insert(@url)
  end

  def test_insert_updates_domain
    assert @uri.to_s =~ /http:\/\/#{BitlyURLRewriter::DOMAIN}\/specialoffer/, "#{@uri.path} was not rewritten to later.ly"
  end

  def test_generates_a_shortened_url
    assert_equal @rewriter.encode_uri(@uri, @pk).to_s, "http://#{BitlyURLRewriter::DOMAIN}/#{@rewriter.encode_pk(@pk)}"
  end

  def test_redirects_to_shortened_url
    assert_equal @rewriter.find(@rewriter.encode_uri(@uri, @pk)), "http:\/\/#{BitlyURLRewriter::DOMAIN}\/specialoffer"
  end

  def test_random_insertions_to_verify_encoding
    1000.times do
      DB::reset!
      @uri, @pk = @rewriter.insert(@url)
      assert_equal @rewriter.find(@rewriter.encode_uri(@uri, @pk)), "http:\/\/#{BitlyURLRewriter::DOMAIN}\/specialoffer"
    end
  end

  #TODO: implement
  def test_rewrite_with_nil_input
  end

  #TODO: implement
  def test_rewrite_with_non_string_values
  end

  #TODO: implement
  def test_rewrite_with_same_string_different_values
  end

  def test_rewrite_domain_to_laterly
    rewriter = BitlyURLRewriter.new
    assert_equal "http://later.ly/specialoffer", rewriter.update_host(@url).to_s
  end

end

bitly_test.rb

require 'test/unit'
require_relative './bitly'

class BitlyURLRewriterTest < Test::Unit::TestCase
  def setup
    @url = "http://awesomesauce.com/specialoffer"
  end

  def test_rewrite
    rewriter = BitlyURLRewriter.new
    assert rewriter.obfuscate_url(rewriter.update_domain(@url)).to_s =~ /^http:\/\/#{BitlyURLRewriter::DOMAIN}\/.*/
  end

  #TODO: implement
  def test_rewrite_with_nil_input
  end

  #TODO: implement
  def test_rewrite_with_non_string_values
  end

  #TODO: implement
  def test_rewrite_with_same_string_different_values
  end

  def test_rewrite_domain_to_laterly
    rewriter = BitlyURLRewriter.new
    assert_equal "http://later.ly/specialoffer", rewriter.update_domain(@url).to_s
  end

  def test_hash_domain
    rewriter = BitlyURLRewriter.new
    assert_nil rewriter.obfuscate_url(URI::parse(@url)).to_s =~ /\/specialoffer$/
  end

end