💱 moneyman

A crusty currency converter

Example

$ moneyman convert 50 --from EUR --to PHP --on 2023-05-06 --fallback
50 EUR -> 3044.5833333333350 PHP on the date 2023-05-06

moneyman is also available as a library.

use std::path::PathBuf;

use chrono::NaiveDate;
use rust_decimal_macros::dec;
use rusty_money::{iso, Money};

fn main() {
    // Choose where to save the historical data files.
    let data_dir: PathBuf = dirs::home_dir()
        .and_then(|home_dir| Some(home_dir.join(".moneyman")))
        .expect("need a home directory");

    // Fetches the historical data from European Central Bank, and creates an
    // exchange store.
    let store = moneyman_core::ExchangeStore::sync(data_dir).expect("failed ze sync");

    let amount_in_usd = Money::from_decimal(dec!(6500), iso::USD);
    let date = NaiveDate::from_ymd_opt(2023, 5, 4).expect("ok date");

    // Converts 6,500.00 USD to EUR
    let actual = store.convert_on_date(amount_in_usd, iso::EUR, date);
    let expected = Money::from_decimal(dec!(5869.6044789597254831135994221), iso::EUR);

    // Shouldn't explode? :)
    assert_eq!(actual, expected);
}

Details

moneyman extends on rusty-money as it already provides a lot of the things like Money, Currency, ExchangeRate, and Exchange. However, it does not provide any data to actually convert currency. For historical data, moneyman uses the European Central Bank, and saves its data to its own local data store.

Caveat

One important thing to know is that ANY_OTHER_CURRENCY -> EUR is computed with 1/<RATE_OF_ONE_EUR_IN_THAT_OTHER_CURRENCY> since ECB only contains the EUR -> ANY_OTHER_CURRENCY rates, not vice versa. This [dividing] is most probably not the behavior observed by RealWord™ currency exchanges. So this only serves as an approximation at best.