finance.tax.remove-vat

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::finance_tax_add_vat::{vat_breakdown_to_value, VatBreakdown};  ← from finance.tax.add-vat ^1.0.0 · built alongside by fune
use super::finance_tax_vat_rate::vat_rate;  ← from finance.tax.vat-rate ^1.0.0 · built alongside by fune
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};  ← from money.amount ^1.0.0 · built alongside by fune

/// Extract the VAT already included in a gross amount.
///
/// Taking 20% off a gross price is the classic error: the VAT inside a 120.00
/// gross price is 20.00, not 24.00. The net is gross x 10000 / (10000 + rate),
/// and the tax is the remainder, so the parts always add back to exactly the
/// gross with no stray penny.
pub fn remove_vat(
    gross: &Money,
    jurisdiction: &str,
    category: &str,
    on_date: &str,
) -> VatBreakdown {
    let rate = vat_rate(jurisdiction, category, on_date);
    let net = money(
        round_div(gross.minor * 10000, 10000 + rate.basis_points, "half-up"),
        &gross.currency,
    );
    VatBreakdown {
        tax: money(gross.minor - net.minor, &gross.currency),
        net,
        gross: gross.clone(),
        basis_points: rate.basis_points,
    }
}

pub fn fune_vector(args: &[Value]) -> Value {
    vat_breakdown_to_value(&remove_vat(
        &money_from_value(&args[0]),
        args[1].as_str(),
        args[2].as_str(),
        args[3].as_str(),
    ))
}