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
use super::*;

impl Timestamp {
    /// Normalizes the timestamp to a canonical format.
    ///
    /// Based on [`google::protobuf::util::CreateNormalized`][1].
    ///
    /// [1]: https://github.com/google/protobuf/blob/v3.3.2/src/google/protobuf/util/time_util.cc#L59-L77
    pub fn normalize(&mut self) {
        // Make sure nanos is in the range.
        if self.nanos <= -NANOS_PER_SECOND || self.nanos >= NANOS_PER_SECOND {
            if let Some(seconds) = self
                .seconds
                .checked_add((self.nanos / NANOS_PER_SECOND) as i64)
            {
                self.seconds = seconds;
                self.nanos %= NANOS_PER_SECOND;
            } else if self.nanos < 0 {
                // Negative overflow! Set to the earliest normal value.
                self.seconds = i64::MIN;
                self.nanos = 0;
            } else {
                // Positive overflow! Set to the latest normal value.
                self.seconds = i64::MAX;
                self.nanos = 999_999_999;
            }
        }

        // For Timestamp nanos should be in the range [0, 999999999].
        if self.nanos < 0 {
            if let Some(seconds) = self.seconds.checked_sub(1) {
                self.seconds = seconds;
                self.nanos += NANOS_PER_SECOND;
            } else {
                // Negative overflow! Set to the earliest normal value.
                debug_assert_eq!(self.seconds, i64::MIN);
                self.nanos = 0;
            }
        }

        // TODO: should this be checked?
        // debug_assert!(self.seconds >= -62_135_596_800 && self.seconds <= 253_402_300_799,
        //               "invalid timestamp: {:?}", self);
    }

    /// Normalizes the timestamp to a canonical format, returning the original value if it cannot be
    /// normalized.
    ///
    /// Normalization is based on [`google::protobuf::util::CreateNormalized`][1].
    ///
    /// [1]: https://github.com/google/protobuf/blob/v3.3.2/src/google/protobuf/util/time_util.cc#L59-L77
    pub fn try_normalize(mut self) -> Result<Timestamp, Timestamp> {
        let before = self;
        self.normalize();
        // If the seconds value has changed, and is either i64::MIN or i64::MAX, then the timestamp
        // normalization overflowed.
        if (self.seconds == i64::MAX || self.seconds == i64::MIN) && self.seconds != before.seconds
        {
            Err(before)
        } else {
            Ok(self)
        }
    }

    /// Creates a new `Timestamp` at the start of the provided UTC date.
    pub fn date(year: i64, month: u8, day: u8) -> Result<Timestamp, TimestampError> {
        Timestamp::date_time_nanos(year, month, day, 0, 0, 0, 0)
    }

    /// Creates a new `Timestamp` instance with the provided UTC date and time.
    pub fn date_time(
        year: i64,
        month: u8,
        day: u8,
        hour: u8,
        minute: u8,
        second: u8,
    ) -> Result<Timestamp, TimestampError> {
        Timestamp::date_time_nanos(year, month, day, hour, minute, second, 0)
    }

    /// Creates a new `Timestamp` instance with the provided UTC date and time.
    pub fn date_time_nanos(
        year: i64,
        month: u8,
        day: u8,
        hour: u8,
        minute: u8,
        second: u8,
        nanos: u32,
    ) -> Result<Timestamp, TimestampError> {
        let date_time = datetime::DateTime {
            year,
            month,
            day,
            hour,
            minute,
            second,
            nanos,
        };

        Timestamp::try_from(date_time)
    }
}

impl Name for Timestamp {
    const PACKAGE: &'static str = PACKAGE;
    const NAME: &'static str = "Timestamp";

    fn type_url() -> String {
        type_url_for::<Self>()
    }
}

/// Implements the unstable/naive version of `Eq`: a basic equality check on the internal fields of the `Timestamp`.
/// This implies that `normalized_ts != non_normalized_ts` even if `normalized_ts == non_normalized_ts.normalized()`.
#[cfg(feature = "std")]
impl Eq for Timestamp {}

#[cfg(feature = "std")]
impl std::hash::Hash for Timestamp {
    fn hash<H: std::hash::Hasher>(&self, state: &mut H) {
        self.seconds.hash(state);
        self.nanos.hash(state);
    }
}

#[cfg(feature = "std")]
impl From<std::time::SystemTime> for Timestamp {
    fn from(system_time: std::time::SystemTime) -> Timestamp {
        let (seconds, nanos) = match system_time.duration_since(std::time::UNIX_EPOCH) {
            Ok(duration) => {
                let seconds = i64::try_from(duration.as_secs()).unwrap();
                (seconds, duration.subsec_nanos() as i32)
            }
            Err(error) => {
                let duration = error.duration();
                let seconds = i64::try_from(duration.as_secs()).unwrap();
                let nanos = duration.subsec_nanos() as i32;
                if nanos == 0 {
                    (-seconds, 0)
                } else {
                    (-seconds - 1, 1_000_000_000 - nanos)
                }
            }
        };
        Timestamp { seconds, nanos }
    }
}

/// A timestamp handling error.
#[derive(Debug, PartialEq)]
#[non_exhaustive]
pub enum TimestampError {
    /// Indicates that a [`Timestamp`] could not be converted to
    /// [`SystemTime`][std::time::SystemTime] because it is out of range.
    ///
    /// The range of times that can be represented by `SystemTime` depends on the platform. All
    /// `Timestamp`s are likely representable on 64-bit Unix-like platforms, but other platforms,
    /// such as Windows and 32-bit Linux, may not be able to represent the full range of
    /// `Timestamp`s.
    OutOfSystemRange(Timestamp),

    /// An error indicating failure to parse a timestamp in RFC-3339 format.
    ParseFailure,

    /// Indicates an error when constructing a timestamp due to invalid date or time data.
    InvalidDateTime,
}

impl fmt::Display for TimestampError {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        match self {
            TimestampError::OutOfSystemRange(timestamp) => {
                write!(
                    f,
                    "{} is not representable as a `SystemTime` because it is out of range",
                    timestamp
                )
            }
            TimestampError::ParseFailure => {
                write!(f, "failed to parse RFC-3339 formatted timestamp")
            }
            TimestampError::InvalidDateTime => {
                write!(f, "invalid date or time")
            }
        }
    }
}

#[cfg(feature = "std")]
impl std::error::Error for TimestampError {}

#[cfg(feature = "std")]
impl TryFrom<Timestamp> for std::time::SystemTime {
    type Error = TimestampError;

    fn try_from(mut timestamp: Timestamp) -> Result<std::time::SystemTime, Self::Error> {
        let orig_timestamp = timestamp;
        timestamp.normalize();

        let system_time = if timestamp.seconds >= 0 {
            std::time::UNIX_EPOCH.checked_add(time::Duration::from_secs(timestamp.seconds as u64))
        } else {
            std::time::UNIX_EPOCH.checked_sub(time::Duration::from_secs(
                timestamp
                    .seconds
                    .checked_neg()
                    .ok_or(TimestampError::OutOfSystemRange(timestamp))? as u64,
            ))
        };

        let system_time = system_time.and_then(|system_time| {
            system_time.checked_add(time::Duration::from_nanos(timestamp.nanos as u64))
        });

        system_time.ok_or(TimestampError::OutOfSystemRange(orig_timestamp))
    }
}

impl FromStr for Timestamp {
    type Err = TimestampError;

    fn from_str(s: &str) -> Result<Timestamp, TimestampError> {
        datetime::parse_timestamp(s).ok_or(TimestampError::ParseFailure)
    }
}

impl fmt::Display for Timestamp {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        datetime::DateTime::from(*self).fmt(f)
    }
}

#[cfg(kani)]
mod proofs {
    use super::*;

    #[cfg(feature = "std")]
    #[kani::proof]
    #[kani::unwind(3)]
    fn check_timestamp_roundtrip_via_system_time() {
        let seconds = kani::any();
        let nanos = kani::any();

        let mut timestamp = Timestamp { seconds, nanos };
        timestamp.normalize();

        if let Ok(system_time) = std::time::SystemTime::try_from(timestamp) {
            assert_eq!(Timestamp::from(system_time), timestamp);
        }
    }
}

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

    #[cfg(feature = "std")]
    use proptest::prelude::*;
    #[cfg(feature = "std")]
    use std::time::{self, SystemTime, UNIX_EPOCH};

    #[cfg(feature = "std")]
    proptest! {
        #[test]
        fn check_system_time_roundtrip(
            system_time in SystemTime::arbitrary(),
        ) {
            prop_assert_eq!(SystemTime::try_from(Timestamp::from(system_time)).unwrap(), system_time);
        }
    }

    #[cfg(feature = "std")]
    #[test]
    fn check_timestamp_negative_seconds() {
        // Representative tests for the case of timestamps before the UTC Epoch time:
        // validate the expected behaviour that "negative second values with fractions
        // must still have non-negative nanos values that count forward in time"
        // https://developers.google.com/protocol-buffers/docs/reference/google.protobuf#google.protobuf.Timestamp
        //
        // To ensure cross-platform compatibility, all nanosecond values in these
        // tests are in minimum 100 ns increments.  This does not affect the general
        // character of the behaviour being tested, but ensures that the tests are
        // valid for both POSIX (1 ns precision) and Windows (100 ns precision).
        assert_eq!(
            Timestamp::from(UNIX_EPOCH - time::Duration::new(1_001, 0)),
            Timestamp {
                seconds: -1_001,
                nanos: 0
            }
        );
        assert_eq!(
            Timestamp::from(UNIX_EPOCH - time::Duration::new(0, 999_999_900)),
            Timestamp {
                seconds: -1,
                nanos: 100
            }
        );
        assert_eq!(
            Timestamp::from(UNIX_EPOCH - time::Duration::new(2_001_234, 12_300)),
            Timestamp {
                seconds: -2_001_235,
                nanos: 999_987_700
            }
        );
        assert_eq!(
            Timestamp::from(UNIX_EPOCH - time::Duration::new(768, 65_432_100)),
            Timestamp {
                seconds: -769,
                nanos: 934_567_900
            }
        );
    }

    #[cfg(all(unix, feature = "std"))]
    #[test]
    fn check_timestamp_negative_seconds_1ns() {
        // UNIX-only test cases with 1 ns precision
        assert_eq!(
            Timestamp::from(UNIX_EPOCH - time::Duration::new(0, 999_999_999)),
            Timestamp {
                seconds: -1,
                nanos: 1
            }
        );
        assert_eq!(
            Timestamp::from(UNIX_EPOCH - time::Duration::new(1_234_567, 123)),
            Timestamp {
                seconds: -1_234_568,
                nanos: 999_999_877
            }
        );
        assert_eq!(
            Timestamp::from(UNIX_EPOCH - time::Duration::new(890, 987_654_321)),
            Timestamp {
                seconds: -891,
                nanos: 12_345_679
            }
        );
    }

    #[cfg(feature = "std")]
    #[test]
    fn check_timestamp_normalize() {
        // Make sure that `Timestamp::normalize` behaves correctly on and near overflow.
        #[rustfmt::skip] // Don't mangle the table formatting.
        let cases = [
            // --- Table of test cases ---
            //        test seconds      test nanos  expected seconds  expected nanos
            (line!(),            0,              0,                0,              0),
            (line!(),            1,              1,                1,              1),
            (line!(),           -1,             -1,               -2,    999_999_999),
            (line!(),            0,    999_999_999,                0,    999_999_999),
            (line!(),            0,   -999_999_999,               -1,              1),
            (line!(),            0,  1_000_000_000,                1,              0),
            (line!(),            0, -1_000_000_000,               -1,              0),
            (line!(),            0,  1_000_000_001,                1,              1),
            (line!(),            0, -1_000_000_001,               -2,    999_999_999),
            (line!(),           -1,              1,               -1,              1),
            (line!(),            1,             -1,                0,    999_999_999),
            (line!(),           -1,  1_000_000_000,                0,              0),
            (line!(),            1, -1_000_000_000,                0,              0),
            (line!(), i64::MIN    ,              0,     i64::MIN    ,              0),
            (line!(), i64::MIN + 1,              0,     i64::MIN + 1,              0),
            (line!(), i64::MIN    ,              1,     i64::MIN    ,              1),
            (line!(), i64::MIN    ,  1_000_000_000,     i64::MIN + 1,              0),
            (line!(), i64::MIN    , -1_000_000_000,     i64::MIN    ,              0),
            (line!(), i64::MIN + 1, -1_000_000_000,     i64::MIN    ,              0),
            (line!(), i64::MIN + 2, -1_000_000_000,     i64::MIN + 1,              0),
            (line!(), i64::MIN    , -1_999_999_998,     i64::MIN    ,              0),
            (line!(), i64::MIN + 1, -1_999_999_998,     i64::MIN    ,              0),
            (line!(), i64::MIN + 2, -1_999_999_998,     i64::MIN    ,              2),
            (line!(), i64::MIN    , -1_999_999_999,     i64::MIN    ,              0),
            (line!(), i64::MIN + 1, -1_999_999_999,     i64::MIN    ,              0),
            (line!(), i64::MIN + 2, -1_999_999_999,     i64::MIN    ,              1),
            (line!(), i64::MIN    , -2_000_000_000,     i64::MIN    ,              0),
            (line!(), i64::MIN + 1, -2_000_000_000,     i64::MIN    ,              0),
            (line!(), i64::MIN + 2, -2_000_000_000,     i64::MIN    ,              0),
            (line!(), i64::MIN    ,   -999_999_998,     i64::MIN    ,              0),
            (line!(), i64::MIN + 1,   -999_999_998,     i64::MIN    ,              2),
            (line!(), i64::MAX    ,              0,     i64::MAX    ,              0),
            (line!(), i64::MAX - 1,              0,     i64::MAX - 1,              0),
            (line!(), i64::MAX    ,             -1,     i64::MAX - 1,    999_999_999),
            (line!(), i64::MAX    ,  1_000_000_000,     i64::MAX    ,    999_999_999),
            (line!(), i64::MAX - 1,  1_000_000_000,     i64::MAX    ,              0),
            (line!(), i64::MAX - 2,  1_000_000_000,     i64::MAX - 1,              0),
            (line!(), i64::MAX    ,  1_999_999_998,     i64::MAX    ,    999_999_999),
            (line!(), i64::MAX - 1,  1_999_999_998,     i64::MAX    ,    999_999_998),
            (line!(), i64::MAX - 2,  1_999_999_998,     i64::MAX - 1,    999_999_998),
            (line!(), i64::MAX    ,  1_999_999_999,     i64::MAX    ,    999_999_999),
            (line!(), i64::MAX - 1,  1_999_999_999,     i64::MAX    ,    999_999_999),
            (line!(), i64::MAX - 2,  1_999_999_999,     i64::MAX - 1,    999_999_999),
            (line!(), i64::MAX    ,  2_000_000_000,     i64::MAX    ,    999_999_999),
            (line!(), i64::MAX - 1,  2_000_000_000,     i64::MAX    ,    999_999_999),
            (line!(), i64::MAX - 2,  2_000_000_000,     i64::MAX    ,              0),
            (line!(), i64::MAX    ,    999_999_998,     i64::MAX    ,    999_999_998),
            (line!(), i64::MAX - 1,    999_999_998,     i64::MAX - 1,    999_999_998),
        ];

        for case in cases.iter() {
            let mut test_timestamp = crate::Timestamp {
                seconds: case.1,
                nanos: case.2,
            };
            test_timestamp.normalize();

            assert_eq!(
                test_timestamp,
                crate::Timestamp {
                    seconds: case.3,
                    nanos: case.4,
                },
                "test case on line {} doesn't match",
                case.0,
            );
        }
    }
}