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::math_round_div::round_div; ← from math.round-div ^1.0.0 · built alongside by fune
use super::money_amount::{money, money_from_value, money_to_value, Money}; ← from money.amount ^1.0.0 · built alongside by fune
use super::property_council_tax_band_data::{BandRatio, BAND_RATIOS, BAND_RATIOS_HISTORY}; ← this capability’s own data, compiled from data/band-ratios.json into the same file by fune build
// Keeps Band D × the largest proportion exact as a JavaScript number; the same limit here.
const MAX_MINOR: i64 = 1_000_000_000_000;
fn is_iso_date(value: &str) -> bool {
let bytes = value.as_bytes();
bytes.len() == 10
&& bytes.iter().enumerate().all(|(i, b)| if i == 4 || i == 7 { *b == b'-' } else { b.is_ascii_digit() })
}
/// The council tax for a band: Band D × the band's statutory proportion ÷ Band
/// D's, rounded half-up to the penny once. The proportions are dated rows, so
/// a Scottish band E before April 2017 uses 440/360 and after it 473/360.
///
/// # Panics
/// Panics on a malformed date, an unknown nation, a Band D charge not in GBP
/// or out of range, or a band the nation did not have on that date.
pub fn council_tax_band(band_d_charge: &Money, band: &str, nation: &str, on_date: &str) -> CouncilTaxBandCharge {
if !is_iso_date(on_date) {
panic!("onDate must be an ISO date (YYYY-MM-DD), received \"{}\"", on_date);
}
if !["england", "wales", "scotland"].contains(&nation) {
panic!("unknown nation \"{}\": use england, wales or scotland", nation);
}
if band_d_charge.currency != "GBP" {
panic!("bandDCharge must be in GBP, received {}", band_d_charge.currency);
}
if band_d_charge.minor < 0 || band_d_charge.minor > MAX_MINOR {
panic!("bandDCharge must be between 0 and {} minor units, received {}", MAX_MINOR, band_d_charge.minor);
}
let mut found: Option<&'static BandRatio> = None;
let mut earliest: Option<&'static str> = None;
for row in BAND_RATIOS {
if row.nation != nation {
continue;
}
if earliest.map_or(true, |e| row.valid_from < e) {
earliest = Some(row.valid_from);
}
if row.band != band || on_date < row.valid_from {
continue;
}
if let Some(to) = row.valid_to {
if on_date > to {
continue;
}
}
found = Some(row);
}
let row = match found {
Some(row) => row,
None => {
if BAND_RATIOS_HISTORY != "full" {
if let Some(e) = earliest {
if on_date < e {
panic!(
"no council tax band {} for {} on {}: this build was installed with history={}, so it only carries rules from {}",
band, nation, on_date, BAND_RATIOS_HISTORY, e
);
}
}
}
panic!("no council tax band {} for {} on {}", band, nation, on_date)
}
};
CouncilTaxBandCharge {
band: band.to_string(),
ratio_numerator: row.numerator,
ratio_denominator: row.denominator,
charge: money(round_div(band_d_charge.minor * row.numerator, row.denominator, "half-up"), "GBP"),
}
}
pub fn council_tax_band_charge_to_value(result: &CouncilTaxBandCharge) -> Value {
Value::obj(vec![
("band", Value::str(&result.band)),
("ratioNumerator", Value::Int(result.ratio_numerator)),
("ratioDenominator", Value::Int(result.ratio_denominator)),
("charge", money_to_value(&result.charge)),
])
}
pub fn fune_vector(args: &[Value]) -> Value {
council_tax_band_charge_to_value(&council_tax_band(
&money_from_value(&args[0]),
args[1].as_str(),
args[2].as_str(),
args[3].as_str(),
))
}