First of all clone this repository:

git clone https://github.com/danbadge/bcg-dv

It's entirely up to you if you want to use Docker/Docker Compose or not, running the application or the tests should work either way.

The app was built with Ruby version 2.5.1 but I also tested with 2.4.3.

bundle install

bundle exec rspec

ruby app.rb

If you're interested, have a look at the .scripts folder as there's some shortcuts for the following commands.

docker-compose run web-app bundle exec rspec

docker-compose up --build

Once you've got the application running you can test out and explore the API, here's an example:

curl http://localhost:8081/lines/M4

• I decided to keep things pretty simple, even starting with a really basic test and implementation which pushed me to implement CSV data retrieval returned as JSON via an API call.
• Continuing with that TDD approach from outside-in has led me to a place where I've got a lot of high-level, functional tests. One improvement might be to push some of these down and closer to the lines_service. Either way, I'm happy with the level of coverage.
• It took a while to understand what was required for lines/:name endpoint, I'm still unsure whether I've interpreted the document correctly.
• There's a little bit too much going on in app.rb still, it could be good to define some api helpers for response building, for example.
• I'm not overly happy with the dependencies between the methods stop_ids_at_position, line_ids_at_stops_and_time and filter_lines_by in lines_service. It all feels a bit too coupled with one read needed before the next retrieval and filter. Nor does extracting this file seem like a good enough separation of concerns, it was difficult to decide how granular to go. However, I'm not sure it would help readability too much more.