Implementation process

shortener API on ruby on rails, as part of the fullstack challenge. Built it without previous experience on ruby on rails, that made me do a lot of research about how things work on the framework.

Adding the short_code field

On the migration file I added a column short_code to be able to store the value of the shortened url

Adding nokogiri gem

On the Gemfile I added the nokogiri gem to extract the title of the website

short_urls_controller.rb

• index method Here I obtained all the records ordered by their click count limiting the sql query to 100

  urls = ShortUrl.order('click_count DESC').limit(100);
  render json: {urls:urls}, status:200

• create method I instanciate a new ShortUrl object passing the full url as an argument, once the object was saved on the database, I called the short_code method to generate the shortcode url and assigned it to the short_code variable to return it on the response, then assigned the generated shortcode to the short_code attribute of the object and save it. If the object was not save I returned the error of the invalid url. More details of how the shortcode is generated on the short_url.rb model section.

  shortUrl = ShortUrl.new(full_url: shortUrl_params)
  if shortUrl.save 
    short_code = shortUrl.short_code
    shortUrl.short_code = short_code
    shortUrl.save!
    render json: {"short_code": short_code}, status:200
  else
    render json: shortUrl.errors, status:400
  end

• show method I try to retrive a record using the short_code as a parameter if the record was not present on the database return a 404 error, otherwise I update the record value of click_count adding 1 to then make the redirect to the stored full url.

  shortUrl = ShortUrl.find_by_short_code(params[:id])
  if shortUrl.nil?
    render json: {"error": "url not found"}, status:404
  else
    shortUrl.update_attribute(:click_count, shortUrl.click_count + 1 )
    redirect_to shortUrl.full_url
  end

• shortUrl_params This method is to tell the controller which parameters are required and be able to create a new object of the ShortUrl class

  def shortUrl_params
      params.require(:full_url)
  end

short_url.rb

Logic of the model ShortUrl

• Added a Regular expression to validate the url

  REGEX = /^(((http|https):\/\/|)?[a-z0-9]+([\-\.]{1}[a-z0-9]+)*\.[a-z]{2,6}(:[0-9]{1,5})?(\/.*)?)$/

• Added a callback to update the title after a record was created

  after_create :update_title!

• short_code method This is a "base 62" encoder for the id generated for the record on the database that way we assure the minimum lenght possible of the shortcode in dependency of the total of records on the system, what this does is to take the id of the object assign to the number variable, return the character "0" when number equals to zero, if the number is greater than zero it will concatenate to the short_url variable the character on the postion of the CHARACTERS array, in order to determinate which position use, we use the result of the number modulo 62, then we divide the number by 62 to be able to continue on the while loop or return the shortcode. modulo 62 and the division by 62 is beacuse that is the lenght of the CHARACTERS array.

  number = self.id
  if number == 0
     return "0" 
  end
  short_url = ""
  while number > 0
   short_url = CHARACTERS[number % 62] + short_url
   number = number / 62
  end
  short_url

• update_title! method Here I called the method perform_later of the UpdateTitleJob class to be enqueue passing the id of the record.

  UpdateTitleJob.perform_later(self.id)

• validate_full_url method On this method I assigned the value of the full url to the variable is_valid, then compare it with the regex expressio, in case the url was invalid I added the error, this error is displayed on the controller create method too.

  is_valid = self.full_url;
  if !is_valid.match?(REGEX)
     errors.add(:errors,"Full url is not a valid url")
  end

update_title_job.rb

• Added the require 'open-uri' to use it to fetch the url

• perform method

  Get the record from the database using the id, then using Nokogiri parse the html of the full url and extract the value of the title tag, then assign the title value to the object and save it to update the record on the database.

  shortUrl = ShortUrl.find(short_url_id)
  title = Nokogiri::HTML.parse(open(shortUrl.full_url)).title
  shortUrl.title = title
  shortUrl.save

Intial Setup

docker-compose build
docker-compose up mariadb
# Once mariadb says it's ready for connections, you can use ctrl + c to stop it
docker-compose run short-app rails db:migrate
docker-compose -f docker-compose-test.yml build

To run migrations

docker-compose run short-app rails db:migrate
docker-compose -f docker-compose-test.yml run short-app-rspec rails db:test:prepare

To run the specs

docker-compose -f docker-compose-test.yml run short-app-rspec

Run the web server

docker-compose up

Adding a URL

curl -X POST -d "full_url=https://google.com" http://localhost:3000/short_urls.json

Getting the top 100

curl localhost:3000

Checking your short URL redirect

curl -I localhost:3000/abc