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Vast Shipping Company

Background Provided

The Vast Shipping Company has a fleet of ships that venture between a set of sea ports in the Wohlstand Sea. The ships and their crews work non stop to load and deliver goods to ports. While the crews diligently work to deliver goods the owner of the Vast Shipping Company likes to track certain statistics of his fleet to help him optimize the business.

Requirements For App to Run Locally

  • Docker Desktop running (for docker-compose commands)
  • ports 3001 and 3307 open on the host (for Puma and MySQL, respectively)

My Approach with Rails and MySQL

Using two docker containers, one for Rails and one for MySQL, we can answer the questions and display them on an interactive web page where the user can query for a given date in the fleet travel logs.

The logic requested is mainly in /app/models/port.rb and /app/models/ship.rb as well as the /app/controllers/pages_controller.rb that serves the database queries out to the dashboard view.

Some familiarity with Docker and Rails will be helpful here, but the commands below should get you a running app at localhost:3001 as long as your machine meets the requirements above (I created this on macOS Catalina).

Starting App

  1. From project root directory:

docker-compose up -d

An image should take a minute to build. If the Rails container fails to start due to a missing ruby dependency (like mini_portile2 2.5.3), the Docker image build may have missed it during bundle install. Exec into the container with:

docker-compose run --rm --service-ports app bash

bundle install

exit

Then repeat Step 1, since your Rails container stopped upon exit of the temporary bash session.

  1. Once both containers are running, you'll have to exec into the Rails container again to talk to the MySQL database:

docker exec -it sportradar_vastshipping_app_1 /bin/sh

bundle exec rake db:migrate

bundle exec rake db:seed

This will create the table schemas and populate the data from the CSV files provided, with relations built in. Example, from the Rails console (note the internal IDs are shifted by one to accomodate MySQL autoincrement behavior for primary keys):

./bin/rails c

irb(main):001:0> s = Ship.find(1) Ship Load (0.8ms) SELECT ships.* FROM ships WHERE ships.id = 1 LIMIT 1 => #<Ship id: 1, name: "Alpha", created_at: "2021-07-28 02:58:10", updated_at: "2021-07-28 02:58:10">

irb(main):002:0> s.fleet_travel_logs FleetTravelLog Load (0.5ms) SELECT fleet_travel_logs.* FROM fleet_travel_logs WHERE fleet_travel_logs.ship_id = 1 LIMIT 11 => #<ActiveRecord::Associations::CollectionProxy [#<FleetTravelLog id: 4, ship_id: 1, from_port_id: 8, to_port_id: 4, time_depart: "2016-06-12 11:20:00", time_arrive: "2016-06-12 13:05:36", distance_traveled: 81.0, average_trip_speed: 46.0227>, #<FleetTravelLog id: 7, ship_id: 1, from_port_id: 4, to_port_id: 7, time_depart: "2016-06-12 15:14:36", time_arrive: "2016-06-12 16:29:00" ...

irb(main):003:0> s.fleet_travel_logs.count() (0.7ms) SELECT COUNT(*) FROM fleet_travel_logs WHERE fleet_travel_logs.ship_id = 1 => 74

Note the times were converted from -0500 (GMT-5) in the text file to UTC in the database:

irb(main):010:0> log = s.fleet_travel_logs.first.time_depart.zone => "UTC"

So converting it back to CDT for Minneapolis, MN at runtime is necessary to make the "same day" calculations accurate. This is done by setting the Rails environment in config/application.rb:

irb(main):001:0> Time.zone => #<ActiveSupport::TimeZone:0x000055cb3565ee28 @name="Central Time (US & Canada)", @utc_offset=nil, @tzinfo=#<TZInfo::DataTimezone: America/Chicago>>

  1. Go to localhost:3001 to see the Fleet Manager dashboard.

Running Tests

Several steps involved here, beginning with creating the test database and with stopping and starting the Rails container into test mode (this could be automated for CI/CD workflows):

docker exec -it sportradar_vastshipping_mysql_1 /bin/sh

mysql -u root -p

create database app_test;

exit

docker-compose run --rm --service-ports -e RAILS_ENV=test app bash

root@08d697da21cb:/home/app# echo $RAILS_ENV test

./bin/rails generate rspec:install

bundle exec rake db:migrate

bundle exec rspec spec/models

Spec Provided

Develop a class called FleetManager that would have the following methods or properties. Note, the definition of a 'completed trip' is a trip that has both started and ended. So when we are interested in number of completed trips in a day, we are interested in the trips that both started and completed with in that day. For this challenge, assume that the owner of Vast Shipping and all the boats operate in the same timezone.

Additional Code Quality Steps

  • Wrote unit tests in RSpec
  • Used rubocop for code style enforcement
manager = FleetManager.new

# Returns a collection of all the ships in the fleet (see FleetShip class)
manager.ships

# Returns the ship (instance of FleetShip) with the slowest trip out of all the completed trips by all ships that day
manager.slowest_ship(time)

# Returns the ship (instance of FleetShip) with the fastest trip out of all the completed trips by all ships that day
manager.fastest_ship(time)

# Returns the name of the port most visited out of all the ports which were visited by the ships in that day.
# Do not count the first port that the ship left as a visited port.
manager.most_visited_port(time)

# Returns the name of the port least visited out of all the ports which were visited by the ships in that day,
# Do not count the first port that the ship left as a visited port.
manager.least_visited_port(time)

Develop a class called FleetShip that would have the following methods or properties

# Returns the name of the ship
ship.name


# Returns a float representing the number of kilometers traveled with the completed trips on that day.
ship.distance_traveled(time)

# Returns a hash representing the completed trip of that day with the fastest average speed (distance in km/time in hr).
# The hash returned includes the name of the beginning port, the name of ending port, depart_time, arrival_time, number 
# of kilometers between the ports, and the average speed in kilometers for the completed. If there is more than one trip
# with the same fastest average speed, only return the first one. 
ship.fastest_trip(time)

# Returns a hash representing the completed trip of that day with the slowest average speed (distance in km/time in hr).
# The hash returned includes the name of the beginning port, the name of ending port, depart_time, arrival_time, number
# of kilometers between the ports, and the average speed in kilometers for the completed. If there is more than one trip
# with the same slowest average speed, only return the last one. 
ship.slowest_trip(time)

Data Files

There are four data files:

  • distances.txt
  • fleet_travel_log.txt
  • ports.txt
  • ships.txt

Read in and parse these files, i.e., do not hard code any of these values.

ports.txt and ships.txt

These two files contain the names of the ports and the names of the ships. Their ids are based on zero-based row position. So for example the port 'Havennesse' has the id of zero. These ids are used in the other files.

distances.txt

This table represents the distances in kilometers between the ports in the Wohlstand sea. So for example if we want the distance between ports 0 and 3, then we would look at position [0,3], which in this case would be 59.

fleet_travel_log.txt

This is a log that contains a snapshot of the travels of the ships. The columns of this table are as follows: ship id, beginning port id, ending port id, time left, time arrived.

The data_file_helpers.rb file

This file has been included as a file you may to incorporate/import it into your solution. Totally up to you.