Test task for Elixir developers. Candidate should write a simple banking OTP application in Elixir language.
- All code is in
gitrepo (candidate can use his/her own github account). - OTP application is a standard
mixproject. - Application name is
:ex_banking(main Elixir module isExBanking). - Application interface is just set of public functions of
ExBankingmodule (no API endpoint, no REST / SOAP API, no TCP / UDP sockets, no any external network interface). - Application should
notuse any database / disc storage. All needed data should be stored only in application memory. - Candidate can use any Elixir or Erlang library he/she wants to.
- Money amount of any currency should
notbe negative. - Application should provide
2 decimalprecision of money amount for any currency. - Amount of money incoming to the system should be equal to amount of money inside the system + amount of withdraws (money should not appear or disappear accidentally).
- User and currency type is any string. Case sensitive. New currencies / users can be added dynamically in runtime.
Requirements for public functions provided by ExBanking module. Any function should return success result or error result. Success result is different for each function, error result is generic
@type banking_error :: {:error,
:wrong_arguments |
:user_already_exists |
:user_does_not_exist |
:not_enough_money |
:sender_does_not_exist |
:receiver_does_not_exist |
:too_many_requests_to_user |
:too_many_requests_to_sender |
:too_many_requests_to_receiver
}
@spec create_user(user :: String.t) :: :ok | banking_error
- Function creates new user in the system
- New user has zero balance of any currency
@spec deposit(user :: String.t, amount :: number, currency :: String.t) :: {:ok, new_balance :: number} | banking_error
- Increases user's balance in given
currencybyamountvalue - Returns
new_balanceof the user in given format
@spec withdraw(user :: String.t, amount :: number, currency :: String.t) :: {:ok, new_balance :: number} | banking_error
- Decreases user's balance in given
currencybyamountvalue - Returns
new_balanceof the user in given format
@spec get_balance(user :: String.t, currency :: String.t) :: {:ok, balance :: number} | banking_error
- Returns
balanceof the user in given format
@spec send(from_user :: String.t, to_user :: String.t, amount :: number, currency :: String.t) :: {:ok, from_user_balance :: number, to_user_balance :: number} | banking_error
- Decreases
from_user's balance in givencurrencybyamountvalue - Increases
to_user's balance in givencurrencybyamountvalue - Returns
balanceoffrom_userandto_userin given format
- In every single moment of time the system should handle 10 or less operations for every individual user (user is a string passed as the first argument to API functions). If there is any new operation for this user and he/she still has 10 operations in pending state - new operation for this user should immediately return
too_many_requests_to_usererror until number of requests for this user decreases < 10 - The system should be able to handle requests for different users in the same moment of time
- Requests for user A should not affect to performance of requests to user B (maybe except
sendfunction when both A and B users are involved in the request)