A toy commandline application for processing transaction records.
cargo run -- tx_records.csv
The provided records db contains a very large deposit of just over one
quintillion moneys to client 612 followed by a series of relatively
small thousand money withdrawals, to demonstrate the fixed point
arithmatic's correct behavior when compared to f64.
I'm unsure how a system might handle disputes of withdrawal transactions, and so such disputes are reported as errorneous.
main panics whenever the arguments are invalid, the input file is
inaccessable, or the parsing fails; all errors from process_transaction
are ignored, main simply moves on to the next record.
Using some error logging/tracing would make this more realistic, but is left undone.
The fixed point arithmatic will panic on overflow, even in release mode. Checking for overflow in the payment toy and cancelling the transaction may be better, but is a touch of code bloat too much for a presumably unrealistic situation.
Since only withdrawal and deposit transactions use the amount column,
constructing a Transaction with or without an amount of moneys
inappropriately is impossible, and the deserializer and constructors
for Transaction prevents negative amounts.
fxhash is likely not faster for
the small 16-bit Client identifiers, and so is not even worth
considering given the denial of service risk. std's default hasher is
used instead, well known for its DOS resistance.