1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
//! Kubernetes [`Duration`]s.
use serde::{de, Deserialize, Deserializer, Serialize, Serializer};
use std::{cmp::Ordering, fmt, str::FromStr, time};

/// A Kubernetes duration.
///
/// This is equivalent to the [`metav1.Duration`] type in the Go Kubernetes
/// apimachinery package. A [`metav1.Duration`] is serialized in YAML and JSON
/// as a string formatted in the format accepted by the Go standard library's
/// [`time.ParseDuration()`] function. This type is a similar wrapper around
/// Rust's [`std::time::Duration`] that can be serialized and deserialized using
/// the same format as `metav1.Duration`.
///
/// # On Signedness
///
/// Go's [`time.Duration`] type is a signed integer type, while Rust's
/// [`std::time::Duration`] is unsigned. Therefore, this type is also capable of
/// representing both positive and negative durations. This is implemented by
/// storing whether or not the parsed duration was negative as a boolean field
/// in the wrapper type. The [`Duration::is_negative`] method returns this
/// value, and when a [`Duration`] is serialized, the negative sign is included
/// if the duration is negative.
///
/// [`Duration`]s can be compared with [`std::time::Duration`]s. If the
/// [`Duration`] is negative, it will always be considered less than the
/// [`std::time::Duration`]. Similarly, because [`std::time::Duration`]s are
/// unsigned, a negative [`Duration`] will never be equal to a
/// [`std::time::Duration`], even if the wrapped [`std::time::Duration`] (the
/// negative duration's absolute value) is equal.
///
/// When converting a [`Duration`] into a [`std::time::Duration`], be aware that
/// *this information is lost*: if a negative [`Duration`] is converted into a
/// [`std::time::Duration`] and then that [`std::time::Duration`] is converted
/// back into a [`Duration`], the second [`Duration`] will *not* be negative.
///
/// [`metav1.Duration`]: https://pkg.go.dev/k8s.io/apimachinery/pkg/apis/meta/v1#Duration
/// [`time.Duration`]: https://pkg.go.dev/time#Duration
/// [`time.ParseDuration()`]: https://pkg.go.dev/time#ParseDuration
#[derive(Copy, Clone, PartialEq, Eq)]
pub struct Duration {
    duration: time::Duration,
    is_negative: bool,
}

/// Errors returned by the [`FromStr`] implementation for [`Duration`].

#[derive(Debug, thiserror::Error, Eq, PartialEq)]
#[non_exhaustive]
pub enum ParseError {
    /// An invalid unit was provided. Units must be one of 'ns', 'us', 'μs',
    /// 's', 'ms', 's', 'm', or 'h'.
    #[error("invalid unit: {}", EXPECTED_UNITS)]
    InvalidUnit,

    /// No unit was provided.
    #[error("missing a unit: {}", EXPECTED_UNITS)]
    NoUnit,

    /// The number associated with a given unit was invalid.
    #[error("invalid floating-point number: {}", .0)]
    NotANumber(#[from] std::num::ParseFloatError),
}

const EXPECTED_UNITS: &str = "expected one of 'ns', 'us', '\u{00b5}s', 'ms', 's', 'm', or 'h'";

impl From<time::Duration> for Duration {
    fn from(duration: time::Duration) -> Self {
        Self {
            duration,
            is_negative: false,
        }
    }
}

impl From<Duration> for time::Duration {
    fn from(Duration { duration, .. }: Duration) -> Self {
        duration
    }
}

impl Duration {
    /// Returns `true` if this `Duration` is negative.
    #[inline]
    #[must_use]
    pub fn is_negative(&self) -> bool {
        self.is_negative
    }
}

impl fmt::Debug for Duration {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        use std::fmt::Write;
        if self.is_negative {
            f.write_char('-')?;
        }
        fmt::Debug::fmt(&self.duration, f)
    }
}

impl fmt::Display for Duration {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        use std::fmt::Write;
        if self.is_negative {
            f.write_char('-')?;
        }
        fmt::Debug::fmt(&self.duration, f)
    }
}

impl FromStr for Duration {
    type Err = ParseError;

    fn from_str(mut s: &str) -> Result<Self, Self::Err> {
        // implements the same format as
        // https://cs.opensource.google/go/go/+/refs/tags/go1.20.4:src/time/format.go;l=1589
        const MINUTE: time::Duration = time::Duration::from_secs(60);

        // Go durations are signed. Rust durations aren't.
        let is_negative = s.starts_with('-');
        s = s.trim_start_matches('+').trim_start_matches('-');

        let mut total = time::Duration::from_secs(0);
        while !s.is_empty() && s != "0" {
            let unit_start = s.find(|c: char| c.is_alphabetic()).ok_or(ParseError::NoUnit)?;

            let (val, rest) = s.split_at(unit_start);
            let val = val.parse::<f64>()?;
            let unit = if let Some(next_numeric_start) = rest.find(|c: char| !c.is_alphabetic()) {
                let (unit, rest) = rest.split_at(next_numeric_start);
                s = rest;
                unit
            } else {
                s = "";
                rest
            };

            // https://cs.opensource.google/go/go/+/refs/tags/go1.20.4:src/time/format.go;l=1573
            let base = match unit {
                "ns" => time::Duration::from_nanos(1),
                // U+00B5 is the "micro sign" while U+03BC is "Greek letter mu"
                "us" | "\u{00b5}s" | "\u{03bc}s" => time::Duration::from_micros(1),
                "ms" => time::Duration::from_millis(1),
                "s" => time::Duration::from_secs(1),
                "m" => MINUTE,
                "h" => MINUTE * 60,
                _ => return Err(ParseError::InvalidUnit),
            };

            total += base.mul_f64(val);
        }

        Ok(Duration {
            duration: total,
            is_negative,
        })
    }
}

impl Serialize for Duration {
    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
    where
        S: Serializer,
    {
        serializer.collect_str(self)
    }
}

impl<'de> Deserialize<'de> for Duration {
    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
    where
        D: Deserializer<'de>,
    {
        struct Visitor;
        impl<'de> de::Visitor<'de> for Visitor {
            type Value = Duration;

            fn expecting(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
                f.write_str("a string in Go `time.Duration.String()` format")
            }

            fn visit_str<E>(self, value: &str) -> Result<Self::Value, E>
            where
                E: de::Error,
            {
                let val = value.parse::<Duration>().map_err(de::Error::custom)?;
                Ok(val)
            }
        }
        deserializer.deserialize_str(Visitor)
    }
}

impl PartialEq<time::Duration> for Duration {
    fn eq(&self, other: &time::Duration) -> bool {
        // Since `std::time::Duration` is unsigned, a negative `Duration` is
        // never equal to a `std::time::Duration`.
        if self.is_negative {
            return false;
        }

        self.duration == *other
    }
}

impl PartialEq<time::Duration> for &'_ Duration {
    fn eq(&self, other: &time::Duration) -> bool {
        // Since `std::time::Duration` is unsigned, a negative `Duration` is
        // never equal to a `std::time::Duration`.
        if self.is_negative {
            return false;
        }

        self.duration == *other
    }
}

impl PartialEq<Duration> for time::Duration {
    fn eq(&self, other: &Duration) -> bool {
        // Since `std::time::Duration` is unsigned, a negative `Duration` is
        // never equal to a `std::time::Duration`.
        if other.is_negative {
            return false;
        }

        self == &other.duration
    }
}

impl PartialEq<Duration> for &'_ time::Duration {
    fn eq(&self, other: &Duration) -> bool {
        // Since `std::time::Duration` is unsigned, a negative `Duration` is
        // never equal to a `std::time::Duration`.
        if other.is_negative {
            return false;
        }

        *self == &other.duration
    }
}

impl PartialOrd for Duration {
    fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
        Some(self.cmp(other))
    }
}

impl Ord for Duration {
    fn cmp(&self, other: &Self) -> Ordering {
        match (self.is_negative, other.is_negative) {
            (true, false) => Ordering::Less,
            (false, true) => Ordering::Greater,
            // if both durations are negative, the "higher" Duration value is
            // actually the lower one
            (true, true) => self.duration.cmp(&other.duration).reverse(),
            (false, false) => self.duration.cmp(&other.duration),
        }
    }
}

impl PartialOrd<time::Duration> for Duration {
    fn partial_cmp(&self, other: &time::Duration) -> Option<Ordering> {
        // Since `std::time::Duration` is unsigned, a negative `Duration` is
        // always less than the `std::time::Duration`.
        if self.is_negative {
            return Some(Ordering::Less);
        }

        self.duration.partial_cmp(other)
    }
}

#[cfg(feature = "schema")]
impl schemars::JsonSchema for Duration {
    // see
    // https://github.com/kubernetes/apimachinery/blob/756e2227bf3a486098f504af1a0ffb736ad16f4c/pkg/apis/meta/v1/duration.go#L61
    fn schema_name() -> String {
        "Duration".to_owned()
    }

    fn is_referenceable() -> bool {
        false
    }

    fn json_schema(_: &mut schemars::gen::SchemaGenerator) -> schemars::schema::Schema {
        schemars::schema::SchemaObject {
            instance_type: Some(schemars::schema::InstanceType::String.into()),
            // the format should *not* be "duration", because "duration" means
            // the duration is formatted in ISO 8601, as described here:
            // https://datatracker.ietf.org/doc/html/draft-handrews-json-schema-validation-02#section-7.3.1
            format: None,
            ..Default::default()
        }
        .into()
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn parses_the_same_as_go() {
        const MINUTE: time::Duration = time::Duration::from_secs(60);
        const HOUR: time::Duration = time::Duration::from_secs(60 * 60);
        // from Go:
        // https://cs.opensource.google/go/go/+/refs/tags/go1.20.4:src/time/time_test.go;l=891-951
        // ```
        // var parseDurationTests = []struct {
        // 	in   string
        // 	want time::Duration
        // }{
        let cases: &[(&str, Duration)] = &[
            // 	// simple
            // 	{"0", 0},
            ("0", time::Duration::from_secs(0).into()),
            // 	{"5s", 5 * Second},
            ("5s", time::Duration::from_secs(5).into()),
            // 	{"30s", 30 * Second},
            ("30s", time::Duration::from_secs(30).into()),
            // 	{"1478s", 1478 * Second},
            ("1478s", time::Duration::from_secs(1478).into()),
            // 	// sign
            // 	{"-5s", -5 * Second},
            ("-5s", Duration {
                duration: time::Duration::from_secs(5),
                is_negative: true,
            }),
            // 	{"+5s", 5 * Second},
            ("+5s", time::Duration::from_secs(5).into()),
            // 	{"-0", 0},
            ("-0", Duration {
                duration: time::Duration::from_secs(0),
                is_negative: true,
            }),
            // 	{"+0", 0},
            ("+0", time::Duration::from_secs(0).into()),
            // 	// decimal
            // 	{"5.0s", 5 * Second},
            ("5s", time::Duration::from_secs(5).into()),
            // 	{"5.6s", 5*Second + 600*Millisecond},
            (
                "5.6s",
                (time::Duration::from_secs(5) + time::Duration::from_millis(600)).into(),
            ),
            // 	{"5.s", 5 * Second},
            ("5.s", time::Duration::from_secs(5).into()),
            // 	{".5s", 500 * Millisecond},
            (".5s", time::Duration::from_millis(500).into()),
            // 	{"1.0s", 1 * Second},
            ("1.0s", time::Duration::from_secs(1).into()),
            // 	{"1.00s", 1 * Second},
            ("1.00s", time::Duration::from_secs(1).into()),
            // 	{"1.004s", 1*Second + 4*Millisecond},
            (
                "1.004s",
                (time::Duration::from_secs(1) + time::Duration::from_millis(4)).into(),
            ),
            // 	{"1.0040s", 1*Second + 4*Millisecond},
            (
                "1.0040s",
                (time::Duration::from_secs(1) + time::Duration::from_millis(4)).into(),
            ),
            // 	{"100.00100s", 100*Second + 1*Millisecond},
            (
                "100.00100s",
                (time::Duration::from_secs(100) + time::Duration::from_millis(1)).into(),
            ),
            // 	// different units
            // 	{"10ns", 10 * Nanosecond},
            ("10ns", time::Duration::from_nanos(10).into()),
            // 	{"11us", 11 * Microsecond},
            ("11us", time::Duration::from_micros(11).into()),
            // 	{"12µs", 12 * Microsecond}, // U+00B5
            ("12µs", time::Duration::from_micros(12).into()),
            // 	{"12μs", 12 * Microsecond}, // U+03BC
            ("12μs", time::Duration::from_micros(12).into()),
            // 	{"13ms", 13 * Millisecond},
            ("13ms", time::Duration::from_millis(13).into()),
            // 	{"14s", 14 * Second},
            ("14s", time::Duration::from_secs(14).into()),
            // 	{"15m", 15 * Minute},
            ("15m", (15 * MINUTE).into()),
            // 	{"16h", 16 * Hour},
            ("16h", (16 * HOUR).into()),
            // 	// composite durations
            // 	{"3h30m", 3*Hour + 30*Minute},
            ("3h30m", (3 * HOUR + 30 * MINUTE).into()),
            // 	{"10.5s4m", 4*Minute + 10*Second + 500*Millisecond},
            (
                "10.5s4m",
                (4 * MINUTE + time::Duration::from_secs(10) + time::Duration::from_millis(500)).into(),
            ),
            // 	{"-2m3.4s", -(2*Minute + 3*Second + 400*Millisecond)},
            ("-2m3.4s", Duration {
                duration: 2 * MINUTE + time::Duration::from_secs(3) + time::Duration::from_millis(400),
                is_negative: true,
            }),
            // 	{"1h2m3s4ms5us6ns", 1*Hour + 2*Minute + 3*Second + 4*Millisecond + 5*Microsecond + 6*Nanosecond},
            (
                "1h2m3s4ms5us6ns",
                (1 * HOUR
                    + 2 * MINUTE
                    + time::Duration::from_secs(3)
                    + time::Duration::from_millis(4)
                    + time::Duration::from_micros(5)
                    + time::Duration::from_nanos(6))
                .into(),
            ),
            // 	{"39h9m14.425s", 39*Hour + 9*Minute + 14*Second + 425*Millisecond},
            (
                "39h9m14.425s",
                (39 * HOUR + 9 * MINUTE + time::Duration::from_secs(14) + time::Duration::from_millis(425))
                    .into(),
            ),
            // 	// large value
            // 	{"52763797000ns", 52763797000 * Nanosecond},
            ("52763797000ns", time::Duration::from_nanos(52763797000).into()),
            // 	// more than 9 digits after decimal point, see https://golang.org/issue/6617
            // 	{"0.3333333333333333333h", 20 * Minute},
            ("0.3333333333333333333h", (20 * MINUTE).into()),
            // 	// 9007199254740993 = 1<<53+1 cannot be stored precisely in a float64
            // 	{"9007199254740993ns", (1<<53 + 1) * Nanosecond},
            (
                "9007199254740993ns",
                time::Duration::from_nanos((1 << 53) + 1).into(),
            ),
            // Rust Durations can handle larger durations than Go's
            // representation, so skip these tests for their precision limits

            // 	// largest duration that can be represented by int64 in nanoseconds
            // 	{"9223372036854775807ns", (1<<63 - 1) * Nanosecond},
            // ("9223372036854775807ns", time::Duration::from_nanos((1 << 63) - 1).into()),
            // 	{"9223372036854775.807us", (1<<63 - 1) * Nanosecond},
            // ("9223372036854775.807us", time::Duration::from_nanos((1 << 63) - 1).into()),
            // 	{"9223372036s854ms775us807ns", (1<<63 - 1) * Nanosecond},
            // 	{"-9223372036854775808ns", -1 << 63 * Nanosecond},
            // 	{"-9223372036854775.808us", -1 << 63 * Nanosecond},
            // 	{"-9223372036s854ms775us808ns", -1 << 63 * Nanosecond},
            // 	// largest negative value
            // 	{"-9223372036854775808ns", -1 << 63 * Nanosecond},
            // 	// largest negative round trip value, see https://golang.org/issue/48629
            // 	{"-2562047h47m16.854775808s", -1 << 63 * Nanosecond},

            // 	// huge string; issue 15011.
            // 	{"0.100000000000000000000h", 6 * Minute},
            ("0.100000000000000000000h", (6 * MINUTE).into()), // 	// This value tests the first overflow check in leadingFraction.
                                                               // 	{"0.830103483285477580700h", 49*Minute + 48*Second + 372539827*Nanosecond},
                                                               // }
                                                               // ```
        ];

        for (input, expected) in cases {
            let parsed = dbg!(input).parse::<Duration>().unwrap();
            assert_eq!(&dbg!(parsed), expected);
        }
    }
}