kprotty / payments-engine

Toy payment system

payments-engine

A toy payments system with support for multiple accounts and simulated transactions. Takes in a file to a CSV of transactions and spits out a CSV of the account details to stdout.

Usage

# view CLI parameters
cargo run -- --help 

# run engine through CLI
cargo run -- transactions.csv > account_details.csv

Testing

• cargo test runs built in integration tests on the engine.
• The examples/ folder contains .csv transactions for testing through cli.

Notes

• Engine transaction errors are ignored/skipped through the CLI interface.
• Transactions with invalid inputs (i.e. negative amounts, missing or unknown ids, etc.) are rejected and return an error internally.
• Transactions which could leave accounts or other transactions in "invalid states" (negative balances, unfreezing accounts, multiple disputes/resolutions/chargebacks) are also rejected internally with an error.
• Commited transactions (deposits/withdrawals) marked as invalid (through dispute -> chargeback) freeze the account preventing any further transactions on it.
• Committed transactions can be disputed then resolved more than once as long as it would leave the account in a "valid" state.
• Chargebacks on disputed withdrawals re-applies the withdrawal instead of coverting it into a deposit which avoids reporting the balance with extra currency.