ohirjak / stte

Simple Toy Transactions Engine

Requirements interpretation

Dispute deposit assumptions

When disputed transaction amount > client available amount => allow negative number in available amount.

Dispute withdrawal assumptions

Provided dispute process describes/matches only handling/reversing of deposit transactions. Assuming handling of withdrawals:

The only action in the whole dispute withdrawal handling is to increase available amount (= reverse withdrawal) and lock account on chargeback. Starting the dispute changes only dispute_state of the transaction.

Creating new client considerations

Currently, a new client is created irrespectively of transaction type if one for particular client id does not exist. However, new client should probably be created only when processing Deposit type of transactions...

Implementation notes

Using type system for checking input file correctness. Checking presence and validity of the amount field for deposit/withdrawal transactions programmatically. Field amount and internally stored amounts use type Decimal from crate rust_decimal. See crate description: "Decimal number implementation written in pure Rust suitable for financial and fixed-precision calculations."

Error handling with crate thiserror.

Testing

Testing correctness of transaction processing with unit tests.

$ cargo test

Testing checking of input csv file validity with invalid input files in data folder.

$ NUM=1
$ cargo run -- data/input-invalid${NUM}.csv

Testing more complicated transaction "flows" with data/input-flow?.csv / data/output-flow?.csv files.

Running

$ cargo run -- transactions.csv > accounts.csv