Rails Code Challenge

Background

This challenge was originally presented by a well-known daily-deal site. I passed the challenge but in the course of interviewing for a remote senior Rails developer position, I was informed that management had decided to suspend all remote hires and only hire in-house going forward.

I was invited to fork a private bare-bones git repository on Github. It was suggested that the challenge would require about 3 hours. I was given a week in which to submit a pull request comprising my solution.

Challenge

Your company has just acquired a new company and needs to import their data. Unfortunately, the acquired company has never stored their data in a database and instead uses a plain text file. Create a web-based application that fulfills the following requirements:

1. Accepts (via a form) a tab delimited file with the following columns: purchaser name, item description, item price, purchase count, merchant address, merchant name. Assume the columns will always be in that order, that there will always be data in each column, and that there will always be a header line. An example input file named example_input.tab is included in this repo.
2. Parses input file, normalizes the data, and stores the information in a relational database.
3. After upload, displays the total amount gross revenue represented by the uploaded file.
4. Installs and runs easily on either Linux or Mac OS X.
5. It should not require any for-pay software.

The application does not need to:

1. handle authentication or authorization (bonus points if it does, extra bonus points if authentication is via OpenID)
2. be aesthetically pleasing

Evaluation

Evaluation of your submission will be based on the following criteria:

1. Did your application fulfill the basic requirements?
2. Did you document the method for setting up and running your application?
3. Did you follow the instructions for submission?
4. Did you consider what changes would need to be made for a true production-ready solution? You can include your thoughts in the README.

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Challenge Submission

Installation

This application is designed to be run locally on the Rails development server with a PostgreSQL database.

Prerequisites

Developed and tested with the following components:

• Rails 4.2.3
• Ruby 2.2.1
• PostgreSQL 9.1.18
• Bundler 1.10.5
• Git 1.7.9.5

For help setting up Rails, see gorails.com.

Application Setup

Install the application itself using git:

git clone https://github.com/klenwell/rails-code-challenge.git rails-code-challenge

Install gems:

cd rails-code-challenge
bundle install

Authentication

Authentication was implemented using the OmniAuth Google OAuth2 gem and requires a Google account to authentice with the app. Any Gmail account should work.

It also requires the following additional configuration. To set up an API key and authorize your application, follow these steps:

1. Log into your Google Developer's Console.
2. Select an existing project (or create a new one if necessary).
3. In sidebar at left, click APIs & auth.
4. Enable API for both Contacts API and Google+ API.
5. In sidebar, click Consent Screen and configure consent screen for users.
6. In sidebar, click Credentials then under OAuth, click Create new Client ID
7. On modal screen, enter following options:

• Application Type: web application (should be default)
• Under Authorized Javascript origins, your test URL: e.g. http://localhost:3000/
• Under Redirect URIs: http://localhost:3000/auth/google_oauth2/callback

8. Click Create Client ID button.

You will be redirected to Credentials screen where you can now obtain the Client ID and Client Secret tokens you will need for your app.

Note: You would need to add any additional URIs for staging or production servers.

Finally, create the following file at config/app_environment_variables.rb to include your tokens:

# Google API Keys for omniauth-google-oauth2 gem.
# See Google Developers Console to manage.
ENV["GOOGLE_CLIENT_ID"] = "YOUR_CLIENT_ID_HERE"
ENV["GOOGLE_CLIENT_SECRET"] = "YOUR_CLIENT_SECRET_HERE"

Note: do not commit that file to your repository. It is already listed in the .gitignore file.

Database

Create your application's postgres database:

# Use postgres command line interface
sudo su - postgres
psql

# SQL commands
CREATE USER rails_challenge WITH PASSWORD 'rails_challenge';
CREATE DATABASE rails_challenge_dev;
GRANT ALL PRIVILEGES ON DATABASE rails_challenge_dev TO rails_challenge;
CREATE DATABASE rails_challenge_test;
GRANT ALL PRIVILEGES ON DATABASE rails_challenge_test TO rails_challenge;

Setup database:

bundle exec rake db:setup RAILS_ENV=development
bundle exec rake db:setup RAILS_ENV=test

Usage

Local Server

To start the the local server on port 3000:

bundle exec rails server -b 0.0.0.0 -p 3000

You should be able to upload files at http://localhost:3000/.

Tests

All tests:

bundle exec rake test

Single test:

bundle exec rake TEST=test/models/purchases_test.rb

Thoughts and Considerations

Design Decisions

• Designed application to meet minimum requirements of application while leaving room for progressive improvements.
• To expedite development, invalid files fail fast with terse messaging. Upload logic set up to enable more expressive feedback with minimal refactoring if desired.
• Organized data into Purchase, Merchant, Product, and Purchaser model. Adapted model names and other terminology from project spec and provided sample file.
• Chose SmarterCSV because I've used it before and it provides a friendly interface.
• Used MiniTest as a matter of habit.
• Coding style and practices generally reflect those promoted at my current organization.

Project Management

I used an Agile approach to organize and task out my project. I tracked my work using a Trello kanban board:

• https://trello.com/b/MwWGnF4p/rails-code-challenge

User stories were divided between requirements (meeting minimum requirements of challenge) and enhancements and are labelled accordingly.

Timesheet

In total, I spent about 5 hours completing the minimum requirements of the exercise:

Planning                        0.5 hours
Project Setup                   0.5
Upload Form                     3.0
Summary/Review                  1.0
----------------------------
Total                           5.0 hours

I spent another 5-6 hours in total implementing a working authentication feature integrating Google's OAuth 2.0 API which, according to their documentation "conforms to the OpenID Connect specification, and is OpenID Certified":

Research/Planning               0.5 hours
Failed 1st Try                  1.0
Additional Research/Planning    0.5
Google Auth Implementation      3.0
Summary/Review                  0.5
----------------------------
Total                           5.5 hours

Production Consideration

In submitting my original pull request, I offered the following points to consider before releasing the application to production:

• Subject application to appropriate security analysis.
  • Is authentication implemented correctly?
  • Is upload vulnerable to exploits?
• Add a file/upload model to track uploads and stop duplicates.
• Provide more detailed error messages to identify issues with reject files.
• Delegate processing to backend queues should upload files be too large for single request.
• Restructure data?
  • Extra data normalization may be overkill if new data is going to be transformed and reloaded by some secondary process.
  • Denormalization may also be warranted depending the size of data and performance demands on application.
• Use a different data store?
• Refactor data parser to be more tolerant or flexible, perhaps as its own class or library.
• Solicit suggestions for improved interface.

A list of additional enhancements can be found in the "To Do" list on my Trello board:

• https://trello.com/b/MwWGnF4p/rails-code-challenge