Imports name this capability’s declared dependencies, which fune builds next to it in your project; each one links to its page.
use super::funejson::Value; ← the fune runtime: the JSON value the test vectors use; fune build keeps it only where a signature takes one
use super::money_allocate::allocate; ← from money.allocate ^1.0.0 · built alongside by fune
use super::money_amount::{money_from_value, money_to_value, Money}; ← from money.amount ^1.0.0 · built alongside by fune
/// Split a period's charge into the part used and the part not used.
///
/// The mid-cycle upgrade, downgrade and cancellation calculation. Written the
/// obvious way - one rounding for the charge and another for the credit - the
/// two halves do not reliably add back up: 9.99 over two days is 4.995 each way,
/// and two half-up roundings produce 5.00 and 5.00, a penny invented on a line
/// the customer can see.
///
/// One call to `money::allocate` does the whole split instead, so
/// `used + unused` is the original amount for every input, credits included.
///
/// # Panics
/// Panics if `total_days` is not positive, or `used_days` is outside
/// `0..=total_days`.
pub fn prorate(amount: &Money, total_days: i64, used_days: i64) -> ProrationSplit {
if total_days <= 0 {
panic!(
"total days must be greater than zero, received {}",
total_days
);
}
if used_days < 0 {
panic!("used days must not be negative, received {}", used_days);
}
if used_days > total_days {
// Clamping here would turn a bug in the caller's period arithmetic into
// a plausible invoice, which is far more expensive to find later.
panic!(
"used days must not exceed total days, received {} of {}",
used_days, total_days
);
}
// total_days > 0 guarantees the ratios do not sum to zero, so allocate is
// safe even when one side is zero: [0, n] and [n, 0] are both well defined.
let parts = allocate(amount, &[used_days, total_days - used_days]);
ProrationSplit {
total: amount.clone(),
used: parts[0].clone(),
unused: parts[1].clone(),
}
}
pub fn proration_split_to_value(split: &ProrationSplit) -> Value {
Value::obj(vec![
("total", money_to_value(&split.total)),
("used", money_to_value(&split.used)),
("unused", money_to_value(&split.unused)),
])
}
pub fn fune_vector(args: &[Value]) -> Value {
// Refuse what the typed signature cannot hold, with the wording TypeScript
// and Python use, rather than let the conversion below quietly change it.
if let Value::Float(f) = args[1] {
if f.fract() != 0.0 {
panic!("total days must be greater than zero, received {}", f);
}
}
if let Value::Float(f) = args[2] {
if f.fract() != 0.0 {
panic!("used days must not be negative, received {}", f);
}
}
proration_split_to_value(&prorate(
&money_from_value(&args[0]),
args[1].as_i64(),
args[2].as_i64(),
))
}