hacklash / heimdall

The Watcher on the Wall

Heimdall

Please read all the instructions before starting this code challenge.

https://hexdocs.pm/phoenix/up_and_running.html

Visit this link for instructions on how to install Phoenix, Elixir, and the hard deps (Erland, Postgres, Node etc...) and get it running.

Challenge

Most products sold in retail have on them what's called a UPC-A barcode. UPC-A barcodes are a set of 12 digits. The first 11 digits are a product identifier while the last digit is what's called a check digit. The check digit exists to ensure that the barcode was generated correctly. Here's where the challenge begins.

We need our phoenix app to be able to generate a check digit so that our barcodes will work. Suppose that you want to find the check digit of UPC-A number 72641217542. From the right to the left, start with odd position, assign the odd/even position to each digit. Sum all digits in odd position and multiply the result by 3: (7+6+1+1+5+2)*3=66 Sum all digits in even position: (2+4+2+7+4)=19 Sum the results of step three and four: 66+19=85 Divide the result of step four by 10. The check digit is the number which adds the remainder to 10. In our case, divide 85 by 10 we get the remainder 5. The check digit then is the result of >10-5=5. If there is no remainder then the check digit equals zero. http://www.azalea.com/white-papers/upc-barcode-check-digit/

There are two routes you need to implement and one bug to fix. All the work will be done in the heimdall/lib/heimdall_web/controllers/api_controller.ex file.

Upon Completion

When finished, shoot us an email with the url of your forked repo.

If for any reason you don't want to fork the repo, you can clone the repo and when you're finished zip it up and email it to us.

Do Not

Do not submit a pull request to this repo.

Do not share your results with other applicants.

More Instructions & Resources

To start your Phoenix server:

• Install dependencies with mix deps.get
• Create and migrate your database with mix ecto.create && mix ecto.migrate
• Install Node.js dependencies with cd assets && npm install
• Start Phoenix endpoint with mix phx.server

Now you can visit localhost:4000 from your browser.

Ready to run in production? Please check our deployment guides.

Learn more

• Official website: http://www.phoenixframework.org/
• Guides: http://phoenixframework.org/docs/overview
• Docs: https://hexdocs.pm/phoenix
• Mailing list: http://groups.google.com/group/phoenix-talk
• Source: https://github.com/phoenixframework/phoenix