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},
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 { .. } => warning::Id::from_static("invalid_type"),
69            Self::Overflow => warning::Id::from_static("overflow"),
70        }
71    }
72}
73
74impl From<rust_decimal::Error> for Warning {
75    fn from(_: rust_decimal::Error) -> Self {
76        Self::Overflow
77    }
78}
79
80/// Convert a `TimeDelta` into a `Decimal` based amount of hours.
81pub trait ToHoursDecimal {
82    /// Return a `Decimal` based amount of hours.
83    fn to_hours_dec(&self) -> Decimal;
84    /// Return a `Decimal` based amount of hours, in the precision specified
85    /// by OCPI.
86    ///
87    /// Note this should only be used for output, for intermediate results use
88    /// `to_hours_dec`, to avoid rounding.
89    fn to_hours_dec_in_ocpi_precision(&self) -> Decimal {
90        self.to_hours_dec().round_to_ocpi_scale()
91    }
92}
93
94impl ToHoursDecimal for TimeDelta {
95    fn to_hours_dec(&self) -> Decimal {
96        let num_sec = Decimal::from(self.num_seconds());
97        let num_nano = Decimal::from(self.subsec_nanos());
98        let sec_part = num_sec.checked_div(SECONDS_IN_HOUR).unwrap_or(Decimal::MAX);
99        let nano_part = num_nano.checked_div(NANOS_IN_HOUR).unwrap_or(Decimal::MAX);
100        sec_part.checked_add(nano_part).unwrap_or(Decimal::MAX)
101    }
102}
103
104/// Convert a `Decimal` amount of hours to a `TimeDelta`.
105pub trait ToDuration {
106    /// Convert a `Decimal` amount of hours to a `TimeDelta`.
107    fn to_duration(&self) -> TimeDelta;
108    /// Convert a `Decimal` amount of hours to a `TimeDelta`.
109    ///
110    /// Ceil the number of nanoseconds up to avoid exceeding `max_power`.
111    fn to_duration_ceil_nanos(&self) -> TimeDelta;
112}
113
114impl ToDuration for Decimal {
115    /// Convert a `Decimal` amount of hours to a `TimeDelta`.
116    ///
117    /// Round to the maximal precision of `TimeDelta` which is nanoseconds.
118    fn to_duration(&self) -> TimeDelta {
119        let nanos = self
120            .saturating_mul(NANOS_IN_HOUR)
121            .round_dp_with_strategy(0, rust_decimal::RoundingStrategy::MidpointAwayFromZero)
122            .to_i64()
123            .unwrap_or(i64::MAX);
124        TimeDelta::nanoseconds(nanos)
125    }
126
127    /// Convert a `Decimal` amount of hours to a `TimeDelta`.
128    ///
129    /// Use the maximal precision of `TimeDelta` which is nanoseconds,
130    /// using ceil to avoid exceeding `max_power`.
131    fn to_duration_ceil_nanos(&self) -> TimeDelta {
132        let nanos = self
133            .saturating_mul(NANOS_IN_HOUR)
134            .ceil()
135            .to_i64()
136            .unwrap_or(i64::MAX);
137        TimeDelta::nanoseconds(nanos)
138    }
139}
140
141/// A `TimeDelta` can't be parsed from JSON directly, you must first decide which unit of time to
142/// parse it as. The `Seconds` type is used to parse the JSON Element as an integer amount of seconds.
143pub(crate) struct Seconds(TimeDelta);
144
145impl number::IsZero for Seconds {
146    fn is_zero(&self) -> bool {
147        self.0.is_zero()
148    }
149}
150
151/// Once the `TimeDelta` has been parsed as seconds you can extract it from the newtype.
152impl From<Seconds> for TimeDelta {
153    fn from(value: Seconds) -> Self {
154        value.0
155    }
156}
157
158impl fmt::Debug for Seconds {
159    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
160        f.debug_tuple("Seconds")
161            .field(&self.0.num_seconds())
162            .finish()
163    }
164}
165
166impl fmt::Display for Seconds {
167    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
168        write!(f, "{}", self.0.num_seconds())
169    }
170}
171
172/// Parse a seconds `TimeDelta` from JSON.
173///
174/// Used to parse the `min_duration` and `max_duration` fields of the tariff Restriction.
175///
176/// * 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>)
177/// * 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>)
178impl json::FromJson<'_> for Seconds {
179    type Warning = Warning;
180
181    fn from_json(elem: &'_ json::Element<'_>) -> Verdict<Self, Self::Warning> {
182        let warnings = warning::Set::new();
183        let Some(s) = elem.as_number_str() else {
184            return warnings.bail(Warning::invalid_type(elem), elem);
185        };
186
187        // We only support positive durations in an OCPI object.
188        let seconds = match s.parse::<u64>() {
189            Ok(n) => n,
190            Err(err) => {
191                return warnings.bail(Warning::Invalid(int_error_kind_as_str(*err.kind())), elem);
192            }
193        };
194
195        // Then we convert the positive duration to an i64 as that is how `chrono::TimeDelta`
196        // represents seconds.
197        let Ok(seconds) = i64::try_from(seconds) else {
198            return warnings.bail(
199                Warning::Invalid("The duration value is larger than an i64 can represent."),
200                elem,
201            );
202        };
203        let dt = TimeDelta::seconds(seconds);
204
205        Ok(Seconds(dt).into_caveat(warnings))
206    }
207}
208
209/// A duration of time has a cost.
210impl Cost for TimeDelta {
211    fn cost(&self, money: Money) -> Money {
212        let cost = self.to_hours_dec().saturating_mul(Decimal::from(money));
213        Money::from_decimal(cost)
214    }
215}
216
217impl SaturatingAdd for TimeDelta {
218    fn saturating_add(self, other: TimeDelta) -> TimeDelta {
219        self.checked_add(&other).unwrap_or(TimeDelta::MAX)
220    }
221}
222
223impl SaturatingSub for TimeDelta {
224    fn saturating_sub(self, other: TimeDelta) -> TimeDelta {
225        self.checked_sub(&other).unwrap_or_else(TimeDelta::zero)
226    }
227}
228
229/// A debug helper trait to display durations as `HH:MM:SS`.
230#[allow(dead_code, reason = "used during debug sessions")]
231pub(crate) trait AsHms {
232    /// Return a `Hms` formatter, that formats a `TimeDelta` into a `String` in `HH::MM::SS` format.
233    fn as_hms(&self) -> Hms;
234}
235
236impl AsHms for TimeDelta {
237    fn as_hms(&self) -> Hms {
238        Hms(*self)
239    }
240}
241
242impl AsHms for Decimal {
243    /// Return a `Hms` formatter, that formats a `TimeDelta` into a `String` in `HH::MM::SS` format.
244    fn as_hms(&self) -> Hms {
245        Hms(self.to_duration())
246    }
247}
248
249/// A utility for deserializing and displaying durations in `HH::MM::SS` format.
250#[derive(Copy, Clone)]
251pub struct Hms(pub TimeDelta);
252
253/// The Debug and Display impls are the same for `Hms` as I never want to see the `TimeDelta` representation.
254impl fmt::Debug for Hms {
255    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
256        fmt::Display::fmt(self, f)
257    }
258}
259
260impl fmt::Display for Hms {
261    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
262        let duration = self.0;
263        let seconds = duration.num_seconds();
264
265        // If the duration is negative write a single minus sign.
266        if seconds.is_negative() {
267            f.write_str("-")?;
268        }
269
270        // Avoid minus signs in the output.
271        let seconds_total = seconds.abs();
272
273        let seconds = seconds_total % SECS_IN_MIN;
274        let minutes = (seconds_total / SECS_IN_MIN) % MINS_IN_HOUR;
275        let hours = seconds_total / (SECS_IN_MIN * MINS_IN_HOUR);
276
277        write!(f, "{hours:0>2}:{minutes:0>2}:{seconds:0>2}")
278    }
279}
280
281#[cfg(test)]
282mod test_hms {
283    use chrono::TimeDelta;
284
285    use super::Hms;
286
287    #[test]
288    fn should_display_seconds() {
289        assert_eq!(Hms(TimeDelta::seconds(0)).to_string(), "00:00:00");
290        assert_eq!(Hms(TimeDelta::seconds(59)).to_string(), "00:00:59");
291    }
292
293    #[test]
294    fn should_display_minutes() {
295        assert_eq!(Hms(TimeDelta::seconds(60)).to_string(), "00:01:00");
296        assert_eq!(Hms(TimeDelta::seconds(3600)).to_string(), "01:00:00");
297    }
298
299    #[test]
300    fn should_display_hours() {
301        assert_eq!(Hms(TimeDelta::minutes(60)).to_string(), "01:00:00");
302        assert_eq!(Hms(TimeDelta::minutes(3600)).to_string(), "60:00:00");
303    }
304
305    #[test]
306    fn should_display_hours_mins_secs() {
307        assert_eq!(Hms(TimeDelta::seconds(87030)).to_string(), "24:10:30");
308    }
309}
310
311#[cfg(test)]
312mod test_to_hours_decimal {
313    use chrono::TimeDelta;
314    use rust_decimal_macros::dec;
315
316    use crate::ToHoursDecimal as _;
317
318    #[test]
319    fn to_hours_dec_should_be_correct() {
320        let actual = TimeDelta::hours(1).to_hours_dec();
321        assert_eq!(actual, dec!(1.0));
322
323        let actual = TimeDelta::seconds(3960).to_hours_dec();
324        assert_eq!(actual, dec!(1.1));
325
326        let actual = TimeDelta::seconds(360).to_hours_dec();
327        assert_eq!(actual, dec!(0.1));
328
329        let actual = TimeDelta::seconds(36).to_hours_dec();
330        assert_eq!(actual, dec!(0.01));
331
332        let actual = TimeDelta::milliseconds(36).to_hours_dec();
333        assert_eq!(actual, dec!(0.00001));
334
335        let actual = TimeDelta::nanoseconds(1).to_hours_dec();
336        assert_eq!(actual, dec!(2.777777777777778e-13));
337    }
338}
339
340#[cfg(test)]
341mod test_to_duration {
342    use chrono::TimeDelta;
343    use rust_decimal_macros::dec;
344
345    use crate::ToDuration as _;
346
347    #[test]
348    fn to_duration_should_be_correct() {
349        let actual = dec!(1.0).to_duration();
350        assert_eq!(actual, TimeDelta::hours(1));
351
352        let actual = dec!(1.1).to_duration();
353        assert_eq!(actual, TimeDelta::seconds(3960));
354
355        let actual = dec!(0.1).to_duration();
356        assert_eq!(actual, TimeDelta::seconds(360));
357
358        let actual = dec!(1e-14).to_duration();
359        assert_eq!(actual, TimeDelta::zero());
360
361        let actual = dec!(2.777e-13).to_duration();
362        assert_eq!(actual, TimeDelta::nanoseconds(1));
363    }
364}
ocpi_tariffs/duration.rs

ocpi_tariffs/
duration.rs
