To start your Phoenix server:

• Install dependencies with mix deps.get
• Start Phoenix endpoint with mix phx.server

Now you can visit localhost:4000 from your browser.

• use mix test to run tests

A few things to note:

• I feel the use of Phoenix was an overkill, a Plug endpoint would do
• This can use more test cases in order to test every aspect of the codebase
• My reason for using Erlang's :ets for in memory cache storage was for efficiency as a standalone API
• This will be fairly performant though would be best to spawn up processes for each incomming request to handle concurrency with heavier payloads in future
• Dialyzer would have been efficient for testing the typespecs

• GET /status (starts up the service ready to accept requests and load cars)
• PUT /cars (updates available cars ready for journey)
• POST /journey (registers a group)
• POST /dropoff (drops off a group whether journeyed or not)
• POST /locate (locates a car that a group is riding in)

1. You can POST to localhost:4000/journey with this payload

   %{ "id" => 33, "group" => 5 }

2. Or post a group of cars to localhost:4000/cars

[
   %{"id" => 22, "seats" => 3},
   %{"id" => 555, "seats" => 15}
]

3. could as well drop off an existing group with a POST request to localhost:4000/dropoff

[
    %{"id" => 555}
]

• start up the API for requests

$ curl --location --request GET 'http://localhost:4000/status' --header 'Content-Type: application/x-www-form-urlencoded' --data-urlencode 'idryy=2'

• load up a few available cars

$ curl --location --request PUT 'http://localhost:4000/cars' --header 'Content-Type: application/json' --data-raw '[{"id": 2, "seats": 8}, {"id": 3, "seats": 4}]'

• if the cars payload is invalid expect a status 400 response

$ curl --location --request PUT 'http://localhost:4000/cars' --header 'Content-Type: application/json' --data-raw '[{"id": 2, "suits": 8}, {"id": "unknown", "seats": "wow"}]'

• load up a group that needs a car

$ curl --location --request POST 'http://localhost:4000/journey' --header 'Content-Type: application/json' --data-raw '{"id": 2, "people": 3}'

• dropoff a group whether boarded or not

$ curl --location --request POST 'http://localhost:4000/dropoff' --header 'Content-Type: application/x-www-form-urlencoded' --data-urlencode 'id=2'

• dropping off an invalid group returns a status 404

$ curl --location --request POST 'http://localhost:4000/dropoff' --header 'Content-Type: application/x-www-form-urlencoded' --data-urlencode 'id=777'

• locate a car that a group is riding in

$ curl --location --request POST 'http://localhost:4000/journey' --header 'Content-Type: application/json' --data-raw '{"id": 22, "people": 3}'

$ curl --location --request POST 'http://localhost:4000/locate' --header 'Content-Type: application/x-www-form-urlencoded' --data-urlencode 'id=22'