Chengdong ZhangandCursor
5e866d08f4
Keep the REST contract; move domain logic out of route files so checkout, fulfillment, and identity can be reused across customer, shop, and admin surfaces. Co-authored-by: Cursor <cursoragent@cursor.com>
71 lines
2.1 KiB
Rust
71 lines
2.1 KiB
Rust
use rust_decimal::prelude::*;
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use rust_decimal::{Decimal, RoundingStrategy};
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use crate::error::ApiError;
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use crate::models::Currency;
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/// Convert integer minor units between currencies via base rates.
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/// rate_to_base = units of currency per 1 unit of base. Rounds half-up
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/// to whole minor units of the target currency.
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pub fn convert_minor(amount_minor: i64, from: &Currency, to: &Currency) -> Result<i64, ApiError> {
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if amount_minor < 0 {
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return Err(ApiError::BadRequest("amount_minor must be >= 0".into()));
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}
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let amount = Decimal::from(amount_minor);
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let from_scale = Decimal::from(10i64.pow(from.exponent as u32));
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let to_scale = Decimal::from(10i64.pow(to.exponent as u32));
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// minor(from) -> major(from) -> major(base) -> minor(to)
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let base_major = amount / from_scale / from.rate_to_base;
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let target = (base_major * to.rate_to_base * to_scale)
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.round_dp_with_strategy(0, RoundingStrategy::MidpointAwayFromZero);
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target
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.to_i64()
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.ok_or_else(|| ApiError::BadRequest("amount out of range".into()))
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}
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#[cfg(test)]
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mod tests {
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use super::*;
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use rust_decimal_macros::dec;
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fn usd() -> Currency {
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Currency {
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code: "USD".into(),
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name: serde_json::json!({"en": "US Dollar"}),
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symbol: "$".into(),
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exponent: 2,
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is_base: true,
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rate_to_base: dec!(1),
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enabled: true,
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}
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}
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fn jpy() -> Currency {
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Currency {
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code: "JPY".into(),
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name: serde_json::json!({"en": "Yen"}),
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symbol: "¥".into(),
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exponent: 0,
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is_base: false,
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rate_to_base: dec!(150),
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enabled: true,
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}
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}
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#[test]
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fn same_currency_is_identity() {
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assert_eq!(convert_minor(199, &usd(), &usd()).unwrap(), 199);
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}
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#[test]
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fn rejects_negative() {
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assert!(convert_minor(-1, &usd(), &usd()).is_err());
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}
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#[test]
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fn converts_via_base_half_up() {
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// 1.00 USD -> 150 JPY at rate 150
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assert_eq!(convert_minor(100, &usd(), &jpy()).unwrap(), 150);
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}
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}
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