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_from_schema;
10
11#[cfg(test)]
12mod test_hour_decimal;
13
14use std::fmt;
15
16use chrono::TimeDelta;
17use num_traits::ToPrimitive as _;
18use rust_decimal::Decimal;
19use rust_decimal_macros::dec;
20
21use crate::{
22    json,
23    number::{self, int_error_kind_as_str, FromDecimal as _, RoundDecimal as _},
24    schema,
25    warning::{self, IntoCaveat as _},
26    Cost, FromSchema, Money, SaturatingAdd, SaturatingSub, Verdict,
27};
28
29pub(crate) const SECS_IN_MIN: i64 = 60;
30pub(crate) const MINS_IN_HOUR: i64 = 60;
31pub(crate) const MILLIS_IN_SEC: i64 = 1000;
32const NANOS_IN_HOUR: Decimal = dec!(36e11);
33const SECONDS_IN_HOUR: Decimal = dec!(3600);
34
35/// The warnings possible when parsing or linting a duration.
36#[derive(Debug, Eq, PartialEq, Ord, PartialOrd)]
37pub enum Warning {
38    /// Unable to parse the duration.
39    Invalid(&'static str),
40
41    /// The JSON value given is not an int.
42    InvalidType { type_found: json::ValueKind },
43
44    /// A numeric overflow occurred while creating a duration.
45    Overflow,
46}
47
48impl Warning {
49    fn invalid_type(elem: &json::Element<'_>) -> Self {
50        Self::InvalidType {
51            type_found: elem.value().kind(),
52        }
53    }
54}
55
56impl fmt::Display for Warning {
57    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
58        match self {
59            Self::Invalid(err) => write!(f, "Unable to parse the duration: {err}"),
60            Self::InvalidType { type_found } => {
61                write!(f, "The value should be an int but is `{type_found}`")
62            }
63            Self::Overflow => f.write_str("A numeric overflow occurred while creating a duration"),
64        }
65    }
66}
67
68impl crate::Warning for Warning {
69    fn id(&self) -> warning::Id {
70        match self {
71            Self::Invalid(_) => warning::Id::from_static("invalid"),
72            Self::InvalidType { type_found } => {
73                warning::Id::from_string(format!("invalid_type({type_found})"))
74            }
75            Self::Overflow => warning::Id::from_static("overflow"),
76        }
77    }
78}
79
80impl From<rust_decimal::Error> for Warning {
81    fn from(_: rust_decimal::Error) -> Self {
82        Self::Overflow
83    }
84}
85
86/// Convert a `TimeDelta` into a `Decimal` based amount of hours.
87pub trait ToHoursDecimal {
88    /// Return a `Decimal` based amount of hours.
89    fn to_hours_dec(&self) -> Decimal;
90    /// Return a `Decimal` based amount of hours, in the precision specified
91    /// by OCPI.
92    ///
93    /// Note this should only be used for output, for intermediate results use
94    /// `to_hours_dec`, to avoid rounding.
95    fn to_hours_dec_in_ocpi_precision(&self) -> Decimal {
96        self.to_hours_dec().round_to_ocpi_scale()
97    }
98}
99
100impl ToHoursDecimal for TimeDelta {
101    fn to_hours_dec(&self) -> Decimal {
102        let num_sec = Decimal::from(self.num_seconds());
103        let num_nano = Decimal::from(self.subsec_nanos());
104        let sec_part = num_sec.checked_div(SECONDS_IN_HOUR).unwrap_or(Decimal::MAX);
105        let nano_part = num_nano.checked_div(NANOS_IN_HOUR).unwrap_or(Decimal::MAX);
106        sec_part.checked_add(nano_part).unwrap_or(Decimal::MAX)
107    }
108}
109
110/// Convert a `Decimal` amount of hours to a `TimeDelta`.
111pub trait ToDuration {
112    /// Convert a `Decimal` amount of hours to a `TimeDelta`.
113    fn to_duration(&self) -> TimeDelta;
114}
115
116impl ToDuration for Decimal {
117    /// Convert a `Decimal` amount of hours to a `TimeDelta`.
118    ///
119    /// Round to the maximal precision of `TimeDelta` which is nanoseconds.
120    fn to_duration(&self) -> TimeDelta {
121        let nanos = self
122            .saturating_mul(NANOS_IN_HOUR)
123            // Any sub-nanosecond fraction is preserved correctly.
124            // A fraction >= 0.5 nanosecond still rounds up, and a fraction < 0.5 nanosecond
125            // rounds down. Both of which represent rounding errors far smaller than any
126            // meaningful time unit.
127            .round_dp_with_strategy(0, rust_decimal::RoundingStrategy::MidpointAwayFromZero)
128            .to_i64()
129            .unwrap_or(i64::MAX);
130        TimeDelta::nanoseconds(nanos)
131    }
132}
133
134/// A `TimeDelta` can't be parsed from JSON directly, you must first decide which unit of time to
135/// parse it as. The `Seconds` type is used to parse the JSON Element as an integer amount of seconds.
136pub(crate) struct Seconds(TimeDelta);
137
138impl number::IsZero for Seconds {
139    fn is_zero(&self) -> bool {
140        self.0.is_zero()
141    }
142}
143
144/// Once the `TimeDelta` has been parsed as seconds you can extract it from the newtype.
145impl From<Seconds> for TimeDelta {
146    fn from(value: Seconds) -> Self {
147        value.0
148    }
149}
150
151impl fmt::Debug for Seconds {
152    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
153        f.debug_tuple("Seconds")
154            .field(&self.0.num_seconds())
155            .finish()
156    }
157}
158
159impl fmt::Display for Seconds {
160    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
161        write!(f, "{}", self.0.num_seconds())
162    }
163}
164
165/// Parse a seconds `TimeDelta` from JSON.
166///
167/// Used to parse the `min_duration` and `max_duration` fields of the tariff Restriction.
168///
169/// * 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>).
170/// * 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>).
171impl<'buf> FromSchema<'buf, schema::Number<'buf>> for Seconds {
172    type Warning = Warning;
173
174    fn from_schema(source: &schema::Number<'buf>) -> Verdict<Self, Self::Warning> {
175        let warnings = warning::Set::new();
176
177        // `Seconds` only accepts a JSON number, not a number encoded as a string. The
178        // schema already proved the literal form is a valid JSON number, so its `digits`
179        // are read directly; a string-encoded value is the wrong kind.
180        let (elem, digits) = match source {
181            schema::Number::Number { elem, digits } => (elem, *digits),
182            schema::Number::StringEncoded { elem, .. } => {
183                return warnings.bail(elem, Warning::invalid_type(elem));
184            }
185        };
186
187        // We only support positive durations in an OCPI object.
188        let seconds = match digits.parse::<u64>() {
189            Ok(n) => n,
190            Err(err) => {
191                return warnings.bail(elem, Warning::Invalid(int_error_kind_as_str(*err.kind())));
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                elem,
200                Warning::Invalid("The duration value is larger than an i64 can represent."),
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#[expect(clippy::allow_attributes, reason = "used during debug sessions")]
231#[allow(dead_code, reason = "used during debug sessions")]
232pub(crate) trait AsHms {
233    /// Return a `Hms` formatter, that formats a `TimeDelta` into a `String` in `HH::MM::SS` format.
234    fn as_hms(&self) -> Hms;
235}
236
237impl AsHms for TimeDelta {
238    fn as_hms(&self) -> Hms {
239        Hms(*self)
240    }
241}
242
243impl AsHms for Decimal {
244    /// Return a `Hms` formatter, that formats a `TimeDelta` into a `String` in `HH::MM::SS` format.
245    fn as_hms(&self) -> Hms {
246        Hms(self.to_duration())
247    }
248}
249
250/// A utility for deserializing and displaying durations in `HH::MM::SS` format.
251#[derive(Copy, Clone)]
252pub struct Hms(pub TimeDelta);
253
254/// The Debug and Display impls are the same for `Hms` as I never want to see the `TimeDelta` representation.
255impl fmt::Debug for Hms {
256    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
257        fmt::Display::fmt(self, f)
258    }
259}
260
261impl fmt::Display for Hms {
262    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
263        let duration = self.0;
264        let seconds = duration.num_seconds();
265
266        // If the duration is negative write a single minus sign.
267        if seconds.is_negative() {
268            f.write_str("-")?;
269        }
270
271        // Avoid minus signs in the output.
272        let seconds_total = seconds.abs();
273
274        let seconds = seconds_total % SECS_IN_MIN;
275        let minutes = (seconds_total / SECS_IN_MIN) % MINS_IN_HOUR;
276        let hours = seconds_total / (SECS_IN_MIN * MINS_IN_HOUR);
277
278        write!(f, "{hours:0>2}:{minutes:0>2}:{seconds:0>2}")
279    }
280}
281
282#[cfg(test)]
283mod test_hms {
284    use chrono::TimeDelta;
285
286    use super::Hms;
287
288    #[test]
289    fn should_display_seconds() {
290        assert_eq!(Hms(TimeDelta::seconds(0)).to_string(), "00:00:00");
291        assert_eq!(Hms(TimeDelta::seconds(59)).to_string(), "00:00:59");
292    }
293
294    #[test]
295    fn should_display_minutes() {
296        assert_eq!(Hms(TimeDelta::seconds(60)).to_string(), "00:01:00");
297        assert_eq!(Hms(TimeDelta::seconds(3600)).to_string(), "01:00:00");
298    }
299
300    #[test]
301    fn should_display_hours() {
302        assert_eq!(Hms(TimeDelta::minutes(60)).to_string(), "01:00:00");
303        assert_eq!(Hms(TimeDelta::minutes(3600)).to_string(), "60:00:00");
304    }
305
306    #[test]
307    fn should_display_hours_mins_secs() {
308        assert_eq!(Hms(TimeDelta::seconds(87030)).to_string(), "24:10:30");
309    }
310}
311
312#[cfg(test)]
313mod test_to_hours_decimal {
314    use chrono::TimeDelta;
315    use rust_decimal_macros::dec;
316
317    use crate::ToHoursDecimal as _;
318
319    #[test]
320    fn to_hours_dec_should_be_correct() {
321        let actual = TimeDelta::hours(1).to_hours_dec();
322        assert_eq!(actual, dec!(1.0));
323
324        let actual = TimeDelta::seconds(3960).to_hours_dec();
325        assert_eq!(actual, dec!(1.1));
326
327        let actual = TimeDelta::seconds(360).to_hours_dec();
328        assert_eq!(actual, dec!(0.1));
329
330        let actual = TimeDelta::seconds(36).to_hours_dec();
331        assert_eq!(actual, dec!(0.01));
332
333        let actual = TimeDelta::milliseconds(36).to_hours_dec();
334        assert_eq!(actual, dec!(0.00001));
335
336        let actual = TimeDelta::nanoseconds(1).to_hours_dec();
337        assert_eq!(actual, dec!(2.777777777777778e-13));
338    }
339}
340
341#[cfg(test)]
342mod test_to_duration {
343    use chrono::TimeDelta;
344    use rust_decimal_macros::dec;
345
346    use crate::ToDuration as _;
347
348    #[test]
349    fn to_duration_should_be_correct() {
350        let actual = dec!(1.0).to_duration();
351        assert_eq!(actual, TimeDelta::hours(1));
352
353        let actual = dec!(1.1).to_duration();
354        assert_eq!(actual, TimeDelta::seconds(3960));
355
356        let actual = dec!(0.1).to_duration();
357        assert_eq!(actual, TimeDelta::seconds(360));
358
359        let actual = dec!(1e-14).to_duration();
360        assert_eq!(actual, TimeDelta::zero());
361
362        let actual = dec!(2.777e-13).to_duration();
363        assert_eq!(actual, TimeDelta::nanoseconds(1));
364    }
365}
ocpi_tariffs/duration.rs

ocpi_tariffs/
duration.rs
