ocpi_tariffs/
duration.rs

1//! The OCPI spec represents some durations as fractional hours, where this crate represents all
2//! durations using [`TimeDelta`]. The [`ToDuration`] and [`ToHoursDecimal`] traits can be used to
3//! convert a [`TimeDelta`] into a [`Decimal`] and vice versa.
4
5#[cfg(test)]
6pub(crate) mod test;
7
8#[cfg(test)]
9mod test_hour_decimal;
10
11use std::fmt;
12
13use chrono::TimeDelta;
14use num_traits::ToPrimitive as _;
15use rust_decimal::Decimal;
16use rust_decimal_macros::dec;
17
18use crate::{
19    json,
20    number::{self, int_error_kind_as_str, FromDecimal as _, RoundDecimal as _},
21    warning::{self, IntoCaveat as _},
22    Cost, Money, SaturatingAdd, SaturatingSub, Verdict,
23};
24
25pub(crate) const SECS_IN_MIN: i64 = 60;
26pub(crate) const MINS_IN_HOUR: i64 = 60;
27pub(crate) const MILLIS_IN_SEC: i64 = 1000;
28const NANOS_IN_HOUR: Decimal = dec!(36e11);
29const SECONDS_IN_HOUR: Decimal = dec!(3600);
30
31/// The warnings possible when parsing or linting a duration.
32#[derive(Debug, Eq, PartialEq, Ord, PartialOrd)]
33pub enum Warning {
34    /// Unable to parse the duration.
35    Invalid(&'static str),
36
37    /// The JSON value given is not an int.
38    InvalidType { type_found: json::ValueKind },
39
40    /// A numeric overflow occurred while creating a duration.
41    Overflow,
42}
43
44impl Warning {
45    fn invalid_type(elem: &json::Element<'_>) -> Self {
46        Self::InvalidType {
47            type_found: elem.value().kind(),
48        }
49    }
50}
51
52impl fmt::Display for Warning {
53    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
54        match self {
55            Self::Invalid(err) => write!(f, "Unable to parse the duration: {err}"),
56            Self::InvalidType { type_found } => {
57                write!(f, "The value should be an int but is `{type_found}`")
58            }
59            Self::Overflow => f.write_str("A numeric overflow occurred while creating a duration"),
60        }
61    }
62}
63
64impl crate::Warning for Warning {
65    fn id(&self) -> warning::Id {
66        match self {
67            Self::Invalid(_) => warning::Id::from_static("invalid"),
68            Self::InvalidType { type_found } => {
69                warning::Id::from_string(format!("invalid_type({type_found})"))
70            }
71            Self::Overflow => warning::Id::from_static("overflow"),
72        }
73    }
74}
75
76impl From<rust_decimal::Error> for Warning {
77    fn from(_: rust_decimal::Error) -> Self {
78        Self::Overflow
79    }
80}
81
82/// Convert a `TimeDelta` into a `Decimal` based amount of hours.
83pub trait ToHoursDecimal {
84    /// Return a `Decimal` based amount of hours.
85    fn to_hours_dec(&self) -> Decimal;
86    /// Return a `Decimal` based amount of hours, in the precision specified
87    /// by OCPI.
88    ///
89    /// Note this should only be used for output, for intermediate results use
90    /// `to_hours_dec`, to avoid rounding.
91    fn to_hours_dec_in_ocpi_precision(&self) -> Decimal {
92        self.to_hours_dec().round_to_ocpi_scale()
93    }
94}
95
96impl ToHoursDecimal for TimeDelta {
97    fn to_hours_dec(&self) -> Decimal {
98        let num_sec = Decimal::from(self.num_seconds());
99        let num_nano = Decimal::from(self.subsec_nanos());
100        let sec_part = num_sec.checked_div(SECONDS_IN_HOUR).unwrap_or(Decimal::MAX);
101        let nano_part = num_nano.checked_div(NANOS_IN_HOUR).unwrap_or(Decimal::MAX);
102        sec_part.checked_add(nano_part).unwrap_or(Decimal::MAX)
103    }
104}
105
106/// Convert a `Decimal` amount of hours to a `TimeDelta`.
107pub trait ToDuration {
108    /// Convert a `Decimal` amount of hours to a `TimeDelta`.
109    fn to_duration(&self) -> TimeDelta;
110}
111
112impl ToDuration for Decimal {
113    /// Convert a `Decimal` amount of hours to a `TimeDelta`.
114    ///
115    /// Round to the maximal precision of `TimeDelta` which is nanoseconds.
116    fn to_duration(&self) -> TimeDelta {
117        let nanos = self
118            .saturating_mul(NANOS_IN_HOUR)
119            // Any sub-nanosecond fraction is preserved correctly.
120            // A fraction >= 0.5 nanosecond still rounds up, and a fraction < 0.5 nanosecond
121            // rounds down. Both of which represent rounding errors far smaller than any
122            // meaningful time unit.
123            .round_dp_with_strategy(0, rust_decimal::RoundingStrategy::MidpointAwayFromZero)
124            .to_i64()
125            .unwrap_or(i64::MAX);
126        TimeDelta::nanoseconds(nanos)
127    }
128}
129
130/// A `TimeDelta` can't be parsed from JSON directly, you must first decide which unit of time to
131/// parse it as. The `Seconds` type is used to parse the JSON Element as an integer amount of seconds.
132pub(crate) struct Seconds(TimeDelta);
133
134impl number::IsZero for Seconds {
135    fn is_zero(&self) -> bool {
136        self.0.is_zero()
137    }
138}
139
140/// Once the `TimeDelta` has been parsed as seconds you can extract it from the newtype.
141impl From<Seconds> for TimeDelta {
142    fn from(value: Seconds) -> Self {
143        value.0
144    }
145}
146
147impl fmt::Debug for Seconds {
148    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
149        f.debug_tuple("Seconds")
150            .field(&self.0.num_seconds())
151            .finish()
152    }
153}
154
155impl fmt::Display for Seconds {
156    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
157        write!(f, "{}", self.0.num_seconds())
158    }
159}
160
161/// Parse a seconds `TimeDelta` from JSON.
162///
163/// Used to parse the `min_duration` and `max_duration` fields of the tariff Restriction.
164///
165/// * See: [OCPI spec 2.2.1: Tariff Restriction](<https://github.com/ocpi/ocpi/blob/release-2.2.1-bugfixes/mod_tariffs.asciidoc#146-tariffrestrictions-class>).
166/// * See: [OCPI spec 2.1.1: Tariff Restriction](<https://github.com/ocpi/ocpi/blob/release-2.1.1-bugfixes/mod_tariffs.md#45-tariffrestrictions-class>).
167impl json::FromJson<'_> for Seconds {
168    type Warning = Warning;
169
170    fn from_json(elem: &'_ json::Element<'_>) -> Verdict<Self, Self::Warning> {
171        let warnings = warning::Set::new();
172        let Some(s) = elem.as_number_str() else {
173            return warnings.bail(elem, Warning::invalid_type(elem));
174        };
175
176        // We only support positive durations in an OCPI object.
177        let seconds = match s.parse::<u64>() {
178            Ok(n) => n,
179            Err(err) => {
180                return warnings.bail(elem, Warning::Invalid(int_error_kind_as_str(*err.kind())));
181            }
182        };
183
184        // Then we convert the positive duration to an i64 as that is how `chrono::TimeDelta`
185        // represents seconds.
186        let Ok(seconds) = i64::try_from(seconds) else {
187            return warnings.bail(
188                elem,
189                Warning::Invalid("The duration value is larger than an i64 can represent."),
190            );
191        };
192        let dt = TimeDelta::seconds(seconds);
193
194        Ok(Seconds(dt).into_caveat(warnings))
195    }
196}
197
198/// A duration of time has a cost.
199impl Cost for TimeDelta {
200    fn cost(&self, money: Money) -> Money {
201        let cost = self.to_hours_dec().saturating_mul(Decimal::from(money));
202        Money::from_decimal(cost)
203    }
204}
205
206impl SaturatingAdd for TimeDelta {
207    fn saturating_add(self, other: TimeDelta) -> TimeDelta {
208        self.checked_add(&other).unwrap_or(TimeDelta::MAX)
209    }
210}
211
212impl SaturatingSub for TimeDelta {
213    fn saturating_sub(self, other: TimeDelta) -> TimeDelta {
214        self.checked_sub(&other).unwrap_or_else(TimeDelta::zero)
215    }
216}
217
218/// A debug helper trait to display durations as `HH:MM:SS`.
219#[expect(clippy::allow_attributes, reason = "used during debug sessions")]
220#[allow(dead_code, reason = "used during debug sessions")]
221pub(crate) trait AsHms {
222    /// Return a `Hms` formatter, that formats a `TimeDelta` into a `String` in `HH::MM::SS` format.
223    fn as_hms(&self) -> Hms;
224}
225
226impl AsHms for TimeDelta {
227    fn as_hms(&self) -> Hms {
228        Hms(*self)
229    }
230}
231
232impl AsHms for Decimal {
233    /// Return a `Hms` formatter, that formats a `TimeDelta` into a `String` in `HH::MM::SS` format.
234    fn as_hms(&self) -> Hms {
235        Hms(self.to_duration())
236    }
237}
238
239/// A utility for deserializing and displaying durations in `HH::MM::SS` format.
240#[derive(Copy, Clone)]
241pub struct Hms(pub TimeDelta);
242
243/// The Debug and Display impls are the same for `Hms` as I never want to see the `TimeDelta` representation.
244impl fmt::Debug for Hms {
245    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
246        fmt::Display::fmt(self, f)
247    }
248}
249
250impl fmt::Display for Hms {
251    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
252        let duration = self.0;
253        let seconds = duration.num_seconds();
254
255        // If the duration is negative write a single minus sign.
256        if seconds.is_negative() {
257            f.write_str("-")?;
258        }
259
260        // Avoid minus signs in the output.
261        let seconds_total = seconds.abs();
262
263        let seconds = seconds_total % SECS_IN_MIN;
264        let minutes = (seconds_total / SECS_IN_MIN) % MINS_IN_HOUR;
265        let hours = seconds_total / (SECS_IN_MIN * MINS_IN_HOUR);
266
267        write!(f, "{hours:0>2}:{minutes:0>2}:{seconds:0>2}")
268    }
269}
270
271#[cfg(test)]
272mod test_hms {
273    use chrono::TimeDelta;
274
275    use super::Hms;
276
277    #[test]
278    fn should_display_seconds() {
279        assert_eq!(Hms(TimeDelta::seconds(0)).to_string(), "00:00:00");
280        assert_eq!(Hms(TimeDelta::seconds(59)).to_string(), "00:00:59");
281    }
282
283    #[test]
284    fn should_display_minutes() {
285        assert_eq!(Hms(TimeDelta::seconds(60)).to_string(), "00:01:00");
286        assert_eq!(Hms(TimeDelta::seconds(3600)).to_string(), "01:00:00");
287    }
288
289    #[test]
290    fn should_display_hours() {
291        assert_eq!(Hms(TimeDelta::minutes(60)).to_string(), "01:00:00");
292        assert_eq!(Hms(TimeDelta::minutes(3600)).to_string(), "60:00:00");
293    }
294
295    #[test]
296    fn should_display_hours_mins_secs() {
297        assert_eq!(Hms(TimeDelta::seconds(87030)).to_string(), "24:10:30");
298    }
299}
300
301#[cfg(test)]
302mod test_to_hours_decimal {
303    use chrono::TimeDelta;
304    use rust_decimal_macros::dec;
305
306    use crate::ToHoursDecimal as _;
307
308    #[test]
309    fn to_hours_dec_should_be_correct() {
310        let actual = TimeDelta::hours(1).to_hours_dec();
311        assert_eq!(actual, dec!(1.0));
312
313        let actual = TimeDelta::seconds(3960).to_hours_dec();
314        assert_eq!(actual, dec!(1.1));
315
316        let actual = TimeDelta::seconds(360).to_hours_dec();
317        assert_eq!(actual, dec!(0.1));
318
319        let actual = TimeDelta::seconds(36).to_hours_dec();
320        assert_eq!(actual, dec!(0.01));
321
322        let actual = TimeDelta::milliseconds(36).to_hours_dec();
323        assert_eq!(actual, dec!(0.00001));
324
325        let actual = TimeDelta::nanoseconds(1).to_hours_dec();
326        assert_eq!(actual, dec!(2.777777777777778e-13));
327    }
328}
329
330#[cfg(test)]
331mod test_to_duration {
332    use chrono::TimeDelta;
333    use rust_decimal_macros::dec;
334
335    use crate::ToDuration as _;
336
337    #[test]
338    fn to_duration_should_be_correct() {
339        let actual = dec!(1.0).to_duration();
340        assert_eq!(actual, TimeDelta::hours(1));
341
342        let actual = dec!(1.1).to_duration();
343        assert_eq!(actual, TimeDelta::seconds(3960));
344
345        let actual = dec!(0.1).to_duration();
346        assert_eq!(actual, TimeDelta::seconds(360));
347
348        let actual = dec!(1e-14).to_duration();
349        assert_eq!(actual, TimeDelta::zero());
350
351        let actual = dec!(2.777e-13).to_duration();
352        assert_eq!(actual, TimeDelta::nanoseconds(1));
353    }
354}
ocpi_tariffs/duration.rs

ocpi_tariffs/
duration.rs
