amount.rs - taler-rust - GNU Taler code in Rust. Largely core banking integrations.

amount.rs (16374B)
      1 /*
      2   This file is part of TALER
      3   Copyright (C) 2024, 2025, 2026 Taler Systems SA
      4 
      5   TALER is free software; you can redistribute it and/or modify it under the
      6   terms of the GNU Affero General Public License as published by the Free Software
      7   Foundation; either version 3, or (at your option) any later version.
      8 
      9   TALER is distributed in the hope that it will be useful, but WITHOUT ANY
     10   WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
     11   A PARTICULAR PURPOSE.  See the GNU Affero General Public License for more details.
     12 
     13   You should have received a copy of the GNU Affero General Public License along with
     14   TALER; see the file COPYING.  If not, see <http://www.gnu.org/licenses/>
     15 */
     16 
     17 //! Type for the Taler Amount <https://docs.taler.net/core/api-common.html#tsref-type-Amount>
     18 
     19 use std::{
     20     fmt::{Debug, Display},
     21     num::ParseIntError,
     22     str::FromStr,
     23 };
     24 
     25 use super::utils::InlineStr;
     26 
     27 /** Number of characters we use to represent currency names */
     28 // We use the same value than the exchange -1 because we use a byte for the len instead of 0 termination
     29 pub const CURRENCY_LEN: usize = 11;
     30 
     31 /** Maximum legal value for an amount, based on IEEE double */
     32 pub const MAX_VALUE: u64 = 2 << 52;
     33 
     34 /** The number of digits in a fraction part of an amount */
     35 pub const FRAC_BASE_NB_DIGITS: u8 = 8;
     36 
     37 /** The fraction part of an amount represents which fraction of the value */
     38 pub const FRAC_BASE: u32 = 10u32.pow(FRAC_BASE_NB_DIGITS as u32);
     39 
     40 const CENT_FRACTION: u32 = 10u32.pow((FRAC_BASE_NB_DIGITS - 2) as u32);
     41 
     42 #[derive(
     43     Clone, Copy, PartialEq, Eq, serde_with::DeserializeFromStr, serde_with::SerializeDisplay,
     44 )]
     45 /// Inlined ISO 4217 currency string
     46 pub struct Currency(InlineStr<CURRENCY_LEN>);
     47 
     48 impl AsRef<str> for Currency {
     49     fn as_ref(&self) -> &str {
     50         self.0.as_ref()
     51     }
     52 }
     53 
     54 #[derive(Debug, thiserror::Error)]
     55 pub enum CurrencyErrorKind {
     56     #[error("contains illegal characters (only A-Z allowed)")]
     57     Invalid,
     58     #[error("too long (max {CURRENCY_LEN} chars)")]
     59     Big,
     60     #[error("is empty")]
     61     Empty,
     62 }
     63 
     64 #[derive(Debug, thiserror::Error)]
     65 #[error("currency code name '{currency}' {kind}")]
     66 pub struct ParseCurrencyError {
     67     currency: String,
     68     pub kind: CurrencyErrorKind,
     69 }
     70 
     71 impl Currency {
     72     pub const TEST: Self = Self::const_parse("TEST");
     73     pub const KUDOS: Self = Self::const_parse("KUDOS");
     74     pub const EUR: Self = Self::const_parse("EUR");
     75     pub const CHF: Self = Self::const_parse("CHF");
     76     pub const HUF: Self = Self::const_parse("HUF");
     77 
     78     pub const fn const_parse(s: &str) -> Currency {
     79         let bytes = s.as_bytes();
     80         let len = bytes.len();
     81 
     82         if bytes.is_empty() {
     83             panic!("empty")
     84         } else if len > CURRENCY_LEN {
     85             panic!("too big")
     86         }
     87         let mut i = 0;
     88         while i < bytes.len() {
     89             if !bytes[i].is_ascii_uppercase() {
     90                 panic!("invalid")
     91             }
     92             i += 1;
     93         }
     94         Self(InlineStr::copy_from_slice(bytes))
     95     }
     96 }
     97 
     98 impl FromStr for Currency {
     99     type Err = ParseCurrencyError;
    100 
    101     fn from_str(s: &str) -> Result<Self, Self::Err> {
    102         let bytes = s.as_bytes();
    103         let len = bytes.len();
    104         if bytes.is_empty() {
    105             Err(CurrencyErrorKind::Empty)
    106         } else if len > CURRENCY_LEN {
    107             Err(CurrencyErrorKind::Big)
    108         } else if !bytes.iter().all(|c| c.is_ascii_uppercase()) {
    109             Err(CurrencyErrorKind::Invalid)
    110         } else {
    111             Ok(Self(InlineStr::copy_from_slice(bytes)))
    112         }
    113         .map_err(|kind| ParseCurrencyError {
    114             currency: s.to_owned(),
    115             kind,
    116         })
    117     }
    118 }
    119 
    120 impl Debug for Currency {
    121     fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
    122         Debug::fmt(&self.as_ref(), f)
    123     }
    124 }
    125 
    126 impl Display for Currency {
    127     fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
    128         Display::fmt(&self.as_ref(), f)
    129     }
    130 }
    131 
    132 #[derive(sqlx::Type)]
    133 #[sqlx(type_name = "taler_amount")]
    134 struct PgTalerAmount {
    135     pub val: i64,
    136     pub frac: i32,
    137 }
    138 
    139 #[derive(
    140     Clone,
    141     Copy,
    142     PartialEq,
    143     Eq,
    144     PartialOrd,
    145     Ord,
    146     serde_with::DeserializeFromStr,
    147     serde_with::SerializeDisplay,
    148 )]
    149 pub struct Decimal {
    150     /** Integer part */
    151     pub val: u64,
    152     /** Factional part, multiple of FRAC_BASE */
    153     pub frac: u32,
    154 }
    155 
    156 impl Decimal {
    157     pub const fn new(val: u64, frac: u32) -> Self {
    158         Self { val, frac }
    159     }
    160 
    161     pub const ZERO: Self = Self::new(0, 0);
    162     pub const MAX: Self = Self::new(MAX_VALUE, FRAC_BASE - 1);
    163 
    164     const fn normalize(mut self) -> Option<Self> {
    165         let Some(val) = self.val.checked_add((self.frac / FRAC_BASE) as u64) else {
    166             return None;
    167         };
    168         self.val = val;
    169         self.frac %= FRAC_BASE;
    170         if self.val > MAX_VALUE {
    171             return None;
    172         }
    173         Some(self)
    174     }
    175 
    176     pub fn try_add(mut self, rhs: &Self) -> Option<Self> {
    177         self.val = self.val.checked_add(rhs.val)?;
    178         self.frac = self
    179             .frac
    180             .checked_add(rhs.frac)
    181             .expect("amount fraction overflow should never happen with normalized amounts");
    182         self.normalize()
    183     }
    184 
    185     pub fn try_sub(mut self, rhs: &Self) -> Option<Self> {
    186         if rhs.frac > self.frac {
    187             self.val = self.val.checked_sub(1)?;
    188             self.frac += FRAC_BASE;
    189         }
    190         self.val = self.val.checked_sub(rhs.val)?;
    191         self.frac = self.frac.checked_sub(rhs.frac)?;
    192         self.normalize()
    193     }
    194 
    195     pub const fn to_amount(self, currency: &Currency) -> Amount {
    196         Amount::new_decimal(currency, self)
    197     }
    198 }
    199 
    200 #[derive(Debug, thiserror::Error)]
    201 pub enum DecimalErrKind {
    202     #[error("value overflow (must be <= {MAX_VALUE})")]
    203     Overflow,
    204     #[error("invalid value ({0})")]
    205     InvalidValue(ParseIntError),
    206     #[error("invalid fraction ({0})")]
    207     InvalidFraction(ParseIntError),
    208     #[error("fraction overflow (max {FRAC_BASE_NB_DIGITS} digits)")]
    209     FractionOverflow,
    210 }
    211 
    212 #[derive(Debug, thiserror::Error)]
    213 #[error("decimal '{decimal}' {kind}")]
    214 pub struct ParseDecimalErr {
    215     decimal: String,
    216     pub kind: DecimalErrKind,
    217 }
    218 
    219 impl FromStr for Decimal {
    220     type Err = ParseDecimalErr;
    221 
    222     fn from_str(s: &str) -> Result<Self, Self::Err> {
    223         let (value, fraction) = s.split_once('.').unwrap_or((s, ""));
    224 
    225         // TODO use try block when stable
    226         (|| {
    227             let value: u64 = value.parse().map_err(DecimalErrKind::InvalidValue)?;
    228             if value > MAX_VALUE {
    229                 return Err(DecimalErrKind::Overflow);
    230             }
    231 
    232             if fraction.len() > FRAC_BASE_NB_DIGITS as usize {
    233                 return Err(DecimalErrKind::FractionOverflow);
    234             }
    235             let fraction: u32 = if fraction.is_empty() {
    236                 0
    237             } else {
    238                 fraction
    239                     .parse::<u32>()
    240                     .map_err(DecimalErrKind::InvalidFraction)?
    241                     * 10u32.pow(FRAC_BASE_NB_DIGITS as u32 - fraction.len() as u32)
    242             };
    243             Ok(Self {
    244                 val: value,
    245                 frac: fraction,
    246             })
    247         })()
    248         .map_err(|kind| ParseDecimalErr {
    249             decimal: s.to_owned(),
    250             kind,
    251         })
    252     }
    253 }
    254 
    255 impl Display for Decimal {
    256     fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
    257         if self.frac == 0 {
    258             f.write_fmt(format_args!("{}", self.val))
    259         } else {
    260             let num = format!("{:08}", self.frac);
    261             f.write_fmt(format_args!("{}.{}", self.val, num.trim_end_matches('0')))
    262         }
    263     }
    264 }
    265 
    266 impl Debug for Decimal {
    267     fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
    268         Display::fmt(&self, f)
    269     }
    270 }
    271 
    272 impl sqlx::Type<sqlx::Postgres> for Decimal {
    273     fn type_info() -> sqlx::postgres::PgTypeInfo {
    274         PgTalerAmount::type_info()
    275     }
    276 }
    277 
    278 impl<'q> sqlx::Encode<'q, sqlx::Postgres> for Decimal {
    279     fn encode_by_ref(
    280         &self,
    281         buf: &mut sqlx::postgres::PgArgumentBuffer,
    282     ) -> Result<sqlx::encode::IsNull, sqlx::error::BoxDynError> {
    283         PgTalerAmount {
    284             val: self.val as i64,
    285             frac: self.frac as i32,
    286         }
    287         .encode_by_ref(buf)
    288     }
    289 }
    290 
    291 impl<'r> sqlx::Decode<'r, sqlx::Postgres> for Decimal {
    292     fn decode(value: sqlx::postgres::PgValueRef<'r>) -> Result<Self, sqlx::error::BoxDynError> {
    293         let pg = PgTalerAmount::decode(value)?;
    294         Ok(Self {
    295             val: pg.val as u64,
    296             frac: pg.frac as u32,
    297         })
    298     }
    299 }
    300 
    301 #[track_caller]
    302 pub fn decimal(decimal: impl AsRef<str>) -> Decimal {
    303     decimal.as_ref().parse().expect("Invalid decimal constant")
    304 }
    305 
    306 /// <https://docs.taler.net/core/api-common.html#tsref-type-Amount>
    307 #[derive(
    308     Clone, Copy, PartialEq, Eq, serde_with::DeserializeFromStr, serde_with::SerializeDisplay,
    309 )]
    310 pub struct Amount {
    311     pub currency: Currency,
    312     pub val: u64,
    313     pub frac: u32,
    314 }
    315 
    316 impl Amount {
    317     pub const fn new_decimal(currency: &Currency, decimal: Decimal) -> Self {
    318         Self {
    319             currency: *currency,
    320             val: decimal.val,
    321             frac: decimal.frac,
    322         }
    323     }
    324 
    325     pub const fn new(currency: &Currency, val: u64, frac: u32) -> Self {
    326         Self::new_decimal(currency, Decimal { val, frac })
    327     }
    328 
    329     pub const fn max(currency: &Currency) -> Self {
    330         Self::new_decimal(currency, Decimal::MAX)
    331     }
    332 
    333     pub const fn zero(currency: &Currency) -> Self {
    334         Self::new_decimal(currency, Decimal::ZERO)
    335     }
    336 
    337     pub fn is_zero(&self) -> bool {
    338         self.decimal() == Decimal::ZERO
    339     }
    340 
    341     /* Check is amount has fractional amount < 0.01 */
    342     pub const fn is_sub_cent(&self) -> bool {
    343         !self.frac.is_multiple_of(CENT_FRACTION)
    344     }
    345 
    346     pub const fn decimal(&self) -> Decimal {
    347         Decimal {
    348             val: self.val,
    349             frac: self.frac,
    350         }
    351     }
    352 
    353     pub fn normalize(self) -> Option<Self> {
    354         let decimal = self.decimal().normalize()?;
    355         Some((self.currency, decimal).into())
    356     }
    357 
    358     pub fn try_add(self, rhs: &Self) -> Option<Self> {
    359         assert_eq!(self.currency, rhs.currency);
    360         let decimal = self.decimal().try_add(&rhs.decimal())?.normalize()?;
    361         Some((self.currency, decimal).into())
    362     }
    363 
    364     pub fn try_sub(self, rhs: &Self) -> Option<Self> {
    365         assert_eq!(self.currency, rhs.currency);
    366         let decimal = self.decimal().try_sub(&rhs.decimal())?.normalize()?;
    367         Some((self.currency, decimal).into())
    368     }
    369 }
    370 
    371 impl From<(Currency, Decimal)> for Amount {
    372     fn from((currency, decimal): (Currency, Decimal)) -> Self {
    373         Self::new_decimal(&currency, decimal)
    374     }
    375 }
    376 
    377 #[track_caller]
    378 pub fn amount(amount: impl AsRef<str>) -> Amount {
    379     amount.as_ref().parse().expect("Invalid amount constant")
    380 }
    381 
    382 #[derive(Debug, thiserror::Error)]
    383 pub enum AmountErrKind {
    384     #[error("invalid format")]
    385     Format,
    386     #[error("currency {0}")]
    387     Currency(#[from] CurrencyErrorKind),
    388     #[error(transparent)]
    389     Decimal(#[from] DecimalErrKind),
    390 }
    391 
    392 #[derive(Debug, thiserror::Error)]
    393 #[error("amount '{amount}' {kind}")]
    394 pub struct ParseAmountErr {
    395     amount: String,
    396     pub kind: AmountErrKind,
    397 }
    398 
    399 impl FromStr for Amount {
    400     type Err = ParseAmountErr;
    401 
    402     fn from_str(s: &str) -> Result<Self, Self::Err> {
    403         // TODO use try block when stable
    404         (|| {
    405             let (currency, amount) = s.trim().split_once(':').ok_or(AmountErrKind::Format)?;
    406             let currency = currency.parse().map_err(|e: ParseCurrencyError| e.kind)?;
    407             let decimal = amount.parse().map_err(|e: ParseDecimalErr| e.kind)?;
    408             Ok((currency, decimal).into())
    409         })()
    410         .map_err(|kind| ParseAmountErr {
    411             amount: s.to_owned(),
    412             kind,
    413         })
    414     }
    415 }
    416 
    417 impl Display for Amount {
    418     fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
    419         f.write_fmt(format_args!("{}:{}", self.currency, self.decimal()))
    420     }
    421 }
    422 
    423 impl Debug for Amount {
    424     fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
    425         Display::fmt(&self, f)
    426     }
    427 }
    428 
    429 impl sqlx::Type<sqlx::Postgres> for Amount {
    430     fn type_info() -> sqlx::postgres::PgTypeInfo {
    431         PgTalerAmount::type_info()
    432     }
    433 }
    434 
    435 impl<'q> sqlx::Encode<'q, sqlx::Postgres> for Amount {
    436     fn encode_by_ref(
    437         &self,
    438         buf: &mut sqlx::postgres::PgArgumentBuffer,
    439     ) -> Result<sqlx::encode::IsNull, sqlx::error::BoxDynError> {
    440         self.decimal().encode_by_ref(buf)
    441     }
    442 }
    443 
    444 #[test]
    445 fn test_amount_parse() {
    446     const TALER_AMOUNT_FRAC_BASE: u32 = 100000000;
    447     // https://git.taler.net/exchange.git/tree/src/util/test_amount.c
    448 
    449     const INVALID_AMOUNTS: [&str; 6] = [
    450         "EUR:4a",                                                                     // non-numeric,
    451         "EUR:4.4a",                                                                   // non-numeric
    452         "EUR:4.a4",                                                                   // non-numeric
    453         ":4.a4",                                                                      // no currency
    454         "EUR:4.123456789", // precision to high
    455         "EUR:1234567890123456789012345678901234567890123456789012345678901234567890", // value to big
    456     ];
    457 
    458     for str in INVALID_AMOUNTS {
    459         let amount = Amount::from_str(str);
    460         assert!(amount.is_err(), "invalid {} got {:?}", str, &amount);
    461     }
    462 
    463     let eur: Currency = Currency::EUR;
    464     let local: Currency = Currency::CHF;
    465     let valid_amounts: Vec<(&str, &str, Amount)> = vec![
    466         ("EUR:4", "EUR:4", Amount::new(&eur, 4, 0)), // without fraction
    467         (
    468             "EUR:0.02",
    469             "EUR:0.02",
    470             Amount::new(&eur, 0, TALER_AMOUNT_FRAC_BASE / 100 * 2),
    471         ), // leading zero fraction
    472         (
    473             " EUR:4.12",
    474             "EUR:4.12",
    475             Amount::new(&eur, 4, TALER_AMOUNT_FRAC_BASE / 100 * 12),
    476         ), // leading space and fraction
    477         (
    478             " CHF:4444.1000",
    479             "CHF:4444.1",
    480             Amount::new(&local, 4444, TALER_AMOUNT_FRAC_BASE / 10),
    481         ), // local currency
    482     ];
    483     for (raw, expected, goal) in valid_amounts {
    484         let amount = Amount::from_str(raw);
    485         assert!(amount.is_ok(), "Valid {} got {:?}", raw, amount);
    486         assert_eq!(
    487             *amount.as_ref().unwrap(),
    488             goal,
    489             "Expected {:?} got {:?} for {}",
    490             goal,
    491             amount,
    492             raw
    493         );
    494         let amount = amount.unwrap();
    495         let str = amount.to_string();
    496         assert_eq!(str, expected);
    497         assert_eq!(amount, Amount::from_str(&str).unwrap(), "{str}");
    498     }
    499 }
    500 
    501 #[test]
    502 fn test_amount_add() {
    503     let eur: Currency = Currency::EUR;
    504     assert_eq!(
    505         Amount::max(&eur).try_add(&Amount::zero(&eur)),
    506         Some(Amount::max(&eur))
    507     );
    508     assert_eq!(
    509         Amount::zero(&eur).try_add(&Amount::zero(&eur)),
    510         Some(Amount::zero(&eur))
    511     );
    512     assert_eq!(
    513         amount("EUR:6.41").try_add(&amount("EUR:4.69")),
    514         Some(amount("EUR:11.1"))
    515     );
    516     assert_eq!(
    517         amount(format!("EUR:{MAX_VALUE}")).try_add(&amount("EUR:0.99999999")),
    518         Some(Amount::max(&eur))
    519     );
    520 
    521     assert_eq!(
    522         amount(format!("EUR:{}", MAX_VALUE - 5)).try_add(&amount("EUR:6")),
    523         None
    524     );
    525     assert_eq!(
    526         Amount::new(&eur, u64::MAX, 0).try_add(&amount("EUR:1")),
    527         None
    528     );
    529     assert_eq!(
    530         amount(format!("EUR:{}.{}", MAX_VALUE - 5, FRAC_BASE - 1))
    531             .try_add(&amount("EUR:5.00000002")),
    532         None
    533     );
    534 }
    535 
    536 #[test]
    537 fn test_amount_normalize() {
    538     let eur: Currency = "EUR".parse().unwrap();
    539     assert_eq!(
    540         Amount::new(&eur, 4, 2 * FRAC_BASE).normalize(),
    541         Some(amount("EUR:6"))
    542     );
    543     assert_eq!(
    544         Amount::new(&eur, 4, 2 * FRAC_BASE + 1).normalize(),
    545         Some(amount("EUR:6.00000001"))
    546     );
    547     assert_eq!(
    548         Amount::new(&eur, MAX_VALUE, FRAC_BASE - 1).normalize(),
    549         Some(Amount::new(&eur, MAX_VALUE, FRAC_BASE - 1))
    550     );
    551     assert_eq!(Amount::new(&eur, u64::MAX, FRAC_BASE).normalize(), None);
    552     assert_eq!(Amount::new(&eur, MAX_VALUE, FRAC_BASE).normalize(), None);
    553 
    554     for amount in [Amount::max(&eur), Amount::zero(&eur)] {
    555         assert_eq!(amount.normalize(), Some(amount))
    556     }
    557 }
	taler-rust GNU Taler code in Rust. Largely core banking integrations.
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