ocpi_tariffs/
money.rs

1//! Various monetary types.
2use std::{borrow::Cow, fmt};
3
4use rust_decimal::Decimal;
5use rust_decimal_macros::dec;
6
7use crate::{
8    from_warning_set_to, impl_dec_newtype, into_caveat,
9    json::{self, FieldsAsExt as _},
10    number::{self, FromDecimal as _},
11    warning::{self, GatherWarnings as _, IntoCaveat},
12    SaturatingAdd as _, Verdict,
13};
14
15/// An item that has a cost.
16pub trait Cost: Copy {
17    /// The cost of this dimension at a certain price.
18    fn cost(&self, money: Money) -> Money;
19}
20
21impl Cost for () {
22    fn cost(&self, money: Money) -> Money {
23        money
24    }
25}
26
27/// The warnings that can happen when parsing or linting a monetary value.
28#[derive(Debug, Eq, PartialEq, Ord, PartialOrd)]
29pub enum WarningKind {
30    /// The `excl_vat` field is greater than the `incl_vat` field.
31    ExclusiveVatGreaterThanInclusive,
32
33    /// The JSON value given is not an object.
34    InvalidType,
35
36    /// The `excl_vat` field is required.
37    MissingExclVatField,
38
39    /// Both the `excl_vat` and `incl_vat` fields should be valid numbers.
40    Number(number::WarningKind),
41}
42
43impl fmt::Display for WarningKind {
44    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
45        match self {
46            WarningKind::ExclusiveVatGreaterThanInclusive => write!(
47                f,
48                "The `excl_vat` field is greater than the `incl_vat` field"
49            ),
50            WarningKind::InvalidType => write!(f, "The value should be a number."),
51            WarningKind::MissingExclVatField => write!(f, "The `excl_vat` field is required."),
52            WarningKind::Number(kind) => fmt::Display::fmt(kind, f),
53        }
54    }
55}
56
57impl warning::Kind for WarningKind {
58    fn id(&self) -> Cow<'static, str> {
59        match self {
60            WarningKind::ExclusiveVatGreaterThanInclusive => {
61                "exclusive_vat_greater_than_inclusive".into()
62            }
63            WarningKind::InvalidType => "invalid_type".into(),
64            WarningKind::MissingExclVatField => "missing_excl_vat_field".into(),
65            WarningKind::Number(kind) => kind.id(),
66        }
67    }
68}
69
70impl From<number::WarningKind> for WarningKind {
71    fn from(warn_kind: number::WarningKind) -> Self {
72        Self::Number(warn_kind)
73    }
74}
75
76from_warning_set_to!(number::WarningKind => WarningKind);
77
78/// A price consisting of a value including VAT, and a value excluding VAT.
79#[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd)]
80#[cfg_attr(test, derive(serde::Deserialize))]
81pub struct Price {
82    /// The price excluding VAT.
83    pub excl_vat: Money,
84
85    /// The price including VAT.
86    ///
87    /// If no vat is applicable this value will be equal to the `excl_vat`.
88    ///
89    /// If no vat could be determined this value will be `None`.
90    /// The v211 tariffs can't determine VAT.
91    #[cfg_attr(test, serde(default))]
92    pub incl_vat: Option<Money>,
93}
94
95impl fmt::Display for Price {
96    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
97        if let Some(incl_vat) = self.incl_vat {
98            write!(f, "{{ -vat: {}, +vat: {} }}", self.excl_vat, incl_vat)
99        } else {
100            fmt::Display::fmt(&self.excl_vat, f)
101        }
102    }
103}
104
105impl json::FromJson<'_, '_> for Price {
106    type WarningKind = WarningKind;
107
108    fn from_json(elem: &json::Element<'_>) -> Verdict<Self, Self::WarningKind> {
109        let mut warnings = warning::Set::new();
110        let value = elem.as_value();
111
112        let Some(fields) = value.as_object_fields() else {
113            warnings.with_elem(WarningKind::InvalidType, elem);
114            return Err(warnings);
115        };
116
117        let Some(excl_vat) = fields.find_field("excl_vat") else {
118            warnings.with_elem(WarningKind::MissingExclVatField, elem);
119            return Err(warnings);
120        };
121
122        let excl_vat = Money::from_json(excl_vat.element())?.gather_warnings_into(&mut warnings);
123
124        let incl_vat = fields
125            .find_field("incl_vat")
126            .map(|f| Money::from_json(f.element()))
127            .transpose()?
128            .gather_warnings_into(&mut warnings);
129
130        if let Some(incl_vat) = incl_vat {
131            if excl_vat > incl_vat {
132                warnings.with_elem(WarningKind::ExclusiveVatGreaterThanInclusive, elem);
133            }
134        }
135
136        Ok(Self { excl_vat, incl_vat }.into_caveat(warnings))
137    }
138}
139
140into_caveat!(Price);
141
142impl Price {
143    pub fn zero() -> Self {
144        Self {
145            excl_vat: Money::zero(),
146            incl_vat: Some(Money::zero()),
147        }
148    }
149
150    pub fn is_zero(&self) -> bool {
151        self.excl_vat.is_zero() && self.incl_vat.is_none_or(|v| v.is_zero())
152    }
153
154    /// Round this number to the OCPI specified amount of decimals.
155    #[must_use]
156    pub fn rescale(self) -> Self {
157        Self {
158            excl_vat: self.excl_vat.rescale(),
159            incl_vat: self.incl_vat.map(Money::rescale),
160        }
161    }
162
163    /// Saturating addition.
164    #[must_use]
165    pub(crate) fn saturating_add(self, rhs: Self) -> Self {
166        let incl_vat = self
167            .incl_vat
168            .zip(rhs.incl_vat)
169            .map(|(lhs, rhs)| lhs.saturating_add(rhs));
170
171        Self {
172            excl_vat: self.excl_vat.saturating_add(rhs.excl_vat),
173            incl_vat,
174        }
175    }
176
177    #[must_use]
178    pub fn round_dp(self, digits: u32) -> Self {
179        Self {
180            excl_vat: self.excl_vat.round_dp(digits),
181            incl_vat: self.incl_vat.map(|v| v.round_dp(digits)),
182        }
183    }
184}
185
186impl Default for Price {
187    fn default() -> Self {
188        Self::zero()
189    }
190}
191
192/// A monetary amount, the currency is dependent on the specified tariff.
193#[derive(Debug, Default, Clone, Copy, PartialEq, Eq, Ord, PartialOrd)]
194#[cfg_attr(test, derive(serde::Deserialize))]
195pub struct Money(Decimal);
196
197impl_dec_newtype!(Money, "¤");
198
199impl Money {
200    /// Apply a VAT percentage to this monetary amount.
201    #[must_use]
202    pub fn apply_vat(self, vat: Vat) -> Self {
203        const ONE: Decimal = dec!(1);
204
205        let x = vat.as_unit_interval().saturating_add(ONE);
206        Self(self.0.saturating_mul(x))
207    }
208}
209
210/// A VAT percentage.
211#[derive(Debug, PartialEq, Eq, Clone, Copy)]
212pub struct Vat(Decimal);
213
214impl_dec_newtype!(Vat, "%");
215
216impl Vat {
217    #[expect(clippy::missing_panics_doc, reason = "The divisor is non-zero")]
218    pub fn as_unit_interval(self) -> Decimal {
219        const PERCENT: Decimal = dec!(100);
220
221        self.0.checked_div(PERCENT).expect("divisor is non-zero")
222    }
223}
224
225/// A VAT percentage with embedded information about whether it's applicable, inapplicable or unknown.
226#[derive(Clone, Copy, Debug)]
227pub enum VatApplicable {
228    /// The VAT percentage is not known.
229    ///
230    /// All `incl_vat` fields should be `None` in the final calculation.
231    Unknown,
232
233    /// The VAT is known but not applicable.
234    ///
235    /// The total `incl_vat` should be equal to `excl_vat`.
236    Inapplicable,
237
238    /// The VAT us known and applicable.
239    Applicable(Vat),
240}
241
242impl json::FromJson<'_, '_> for VatApplicable {
243    type WarningKind = number::WarningKind;
244
245    fn from_json(elem: &'_ json::Element<'_>) -> Verdict<Self, Self::WarningKind> {
246        let vat = Decimal::from_json(elem)?;
247        Ok(vat.map(|d| Self::Applicable(Vat::from_decimal(d))))
248    }
249}
250
251#[cfg(test)]
252mod test {
253    use crate::test::ApproxEq;
254
255    use super::Price;
256
257    impl ApproxEq for Price {
258        fn approx_eq(&self, other: &Self) -> bool {
259            let incl_eq = match (self.incl_vat, other.incl_vat) {
260                (Some(a), Some(b)) => a.approx_eq(&b),
261                (None, None) => true,
262                _ => return false,
263            };
264
265            incl_eq && self.excl_vat.approx_eq(&other.excl_vat)
266        }
267    }
268}
269
270#[cfg(test)]
271mod test_price {
272    use assert_matches::assert_matches;
273    use rust_decimal::Decimal;
274    use rust_decimal_macros::dec;
275
276    use crate::json::{self, FromJson as _};
277
278    use super::{Price, WarningKind};
279
280    #[test]
281    fn should_create_from_json_with_only_excl_vat_field() {
282        const JSON: &str = r#"{
283            "excl_vat": 10.2
284        }"#;
285
286        let elem = json::parse(JSON).unwrap();
287        let price = Price::from_json(&elem).unwrap().unwrap();
288
289        assert!(price.incl_vat.is_none());
290        assert_eq!(Decimal::from(price.excl_vat), dec!(10.2));
291    }
292
293    #[test]
294    fn should_create_from_json_with_excl_and_incl_vat_fields() {
295        const JSON: &str = r#"{
296            "excl_vat": 10.2,
297            "incl_vat": 12.3
298        }"#;
299
300        let elem = json::parse(JSON).unwrap();
301        let price = Price::from_json(&elem).unwrap().unwrap();
302
303        assert_eq!(Decimal::from(price.incl_vat.unwrap()), dec!(12.3));
304        assert_eq!(Decimal::from(price.excl_vat), dec!(10.2));
305    }
306
307    #[test]
308    fn should_fail_to_create_from_non_object_json() {
309        const JSON: &str = "12.3";
310
311        let elem = json::parse(JSON).unwrap();
312        let warnings = Price::from_json(&elem).unwrap_err().into_kind_vec();
313
314        assert_matches!(*warnings, [WarningKind::InvalidType]);
315    }
316
317    #[test]
318    fn should_fail_to_create_from_json_as_excl_vat_is_required() {
319        const JSON: &str = r#"{
320            "incl_vat": 12.3
321        }"#;
322
323        let elem = json::parse(JSON).unwrap();
324        let warnings = Price::from_json(&elem).unwrap_err().into_kind_vec();
325
326        assert_matches!(*warnings, [WarningKind::MissingExclVatField]);
327    }
328
329    #[test]
330    fn should_create_from_json_and_warn_about_excl_vat_greater_than_incl_vat() {
331        const JSON: &str = r#"{
332            "excl_vat": 12.3,
333            "incl_vat": 10.2
334        }"#;
335
336        let elem = json::parse(JSON).unwrap();
337        let (_price, warnings) = Price::from_json(&elem).unwrap().into_parts();
338        let warnings = warnings.into_kind_vec();
339
340        assert_matches!(*warnings, [WarningKind::ExclusiveVatGreaterThanInclusive]);
341    }
342}
ocpi_tariffs/money.rs

ocpi_tariffs/
money.rs
