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
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
1183
1184
1185
1186
1187
1188
1189
1190
1191
1192
1193
1194
1195
1196
1197
1198
1199
1200
1201
1202
1203
1204
1205
1206
1207
1208
1209
1210
1211
1212
1213
1214
1215
1216
1217
1218
1219
1220
1221
1222
1223
1224
1225
1226
1227
1228
1229
1230
1231
1232
1233
1234
1235
1236
1237
1238
1239
1240
1241
1242
1243
1244
1245
1246
1247
1248
1249
1250
1251
1252
1253
1254
1255
1256
1257
1258
1259
1260
1261
1262
1263
1264
1265
1266
1267
1268
1269
1270
1271
1272
1273
1274
1275
1276
1277
1278
1279
1280
1281
1282
1283
1284
1285
1286
1287
1288
1289
1290
1291
1292
1293
1294
1295
1296
1297
1298
1299
1300
1301
1302
1303
1304
1305
1306
1307
1308
1309
1310
1311
1312
1313
1314
1315
1316
1317
1318
1319
1320
1321
1322
1323
1324
1325
1326
1327
1328
1329
1330
1331
1332
1333
1334
1335
1336
1337
1338
1339
1340
1341
1342
1343
1344
1345
1346
1347
1348
1349
1350
1351
1352
1353
1354
1355
1356
1357
1358
1359
1360
1361
1362
1363
1364
1365
1366
1367
1368
1369
1370
1371
1372
1373
1374
1375
1376
1377
1378
1379
1380
1381
1382
1383
1384
1385
1386
1387
1388
1389
1390
1391
1392
1393
1394
1395
1396
1397
1398
1399
1400
1401
1402
1403
1404
1405
1406
1407
1408
1409
1410
1411
1412
1413
1414
1415
1416
1417
1418
1419
1420
1421
1422
1423
1424
1425
1426
1427
1428
1429
1430
1431
1432
1433
1434
1435
1436
1437
1438
1439
1440
1441
1442
1443
1444
1445
1446
1447
1448
1449
1450
1451
1452
1453
1454
1455
1456
1457
1458
1459
1460
1461
1462
1463
1464
1465
1466
1467
1468
1469
1470
1471
1472
1473
1474
1475
1476
1477
1478
1479
1480
1481
1482
1483
1484
1485
1486
1487
1488
1489
1490
1491
1492
1493
1494
1495
1496
1497
1498
1499
1500
1501
1502
1503
1504
1505
1506
1507
1508
1509
1510
1511
1512
1513
1514
1515
1516
1517
1518
1519
1520
1521
1522
1523
1524
1525
1526
1527
1528
1529
1530
1531
1532
1533
1534
1535
1536
1537
1538
use std::borrow::Cow;
use std::fmt::Debug;
use std::time::{Duration, SystemTime, UNIX_EPOCH};

use ordered_varint::Variable;
use serde::{Deserialize, Serialize};

use crate::key::time::limited::{BonsaiEpoch, UnixEpoch};
use crate::key::{ByteSource, CompositeKind, Key, KeyEncoding, KeyKind, KeyVisitor};

impl<'k> Key<'k> for Duration {
    const CAN_OWN_BYTES: bool = false;

    fn from_ord_bytes<'e>(bytes: ByteSource<'k, 'e>) -> Result<Self, Self::Error> {
        let merged = u128::decode_variable(bytes.as_ref()).map_err(|_| TimeError::InvalidValue)?;
        let seconds = u64::try_from(merged >> 30).map_err(|_| TimeError::DeltaNotRepresentable)?;
        let nanos = u32::try_from(merged & (2_u128.pow(30) - 1)).unwrap();
        Ok(Self::new(seconds, nanos))
    }
}

impl KeyEncoding<Self> for Duration {
    type Error = TimeError;

    const LENGTH: Option<usize> = None;

    fn describe<Visitor>(visitor: &mut Visitor)
    where
        Visitor: KeyVisitor,
    {
        visitor.visit_composite(
            CompositeKind::Struct(Cow::Borrowed("std::time::Duration")),
            1,
        );
        visitor.visit_type(KeyKind::Unsigned);
    }

    fn as_ord_bytes(&self) -> Result<Cow<'_, [u8]>, Self::Error> {
        let merged = u128::from(self.as_secs()) << 30 | u128::from(self.subsec_nanos());
        // It's safe to unwrap here, because under the hood ordered-varint can
        // only raise an error if the top bits are set. Since we only ever add
        // 94 bits, the top bits will not have any data set.
        Ok(Cow::Owned(merged.to_variable_vec().unwrap()))
    }
}

#[test]
fn duration_key_tests() {
    assert_eq!(
        Duration::ZERO,
        Duration::from_ord_bytes(ByteSource::Borrowed(
            &Duration::ZERO.as_ord_bytes().unwrap()
        ))
        .unwrap()
    );
    assert_eq!(
        Duration::MAX,
        Duration::from_ord_bytes(ByteSource::Borrowed(&Duration::MAX.as_ord_bytes().unwrap()))
            .unwrap()
    );
}

impl<'k> Key<'k> for SystemTime {
    const CAN_OWN_BYTES: bool = false;

    fn from_ord_bytes<'e>(bytes: ByteSource<'k, 'e>) -> Result<Self, Self::Error> {
        let since_epoch = Duration::from_ord_bytes(bytes)?;
        UNIX_EPOCH
            .checked_add(since_epoch)
            .ok_or(TimeError::DeltaNotRepresentable)
    }
}

impl KeyEncoding<Self> for SystemTime {
    type Error = TimeError;

    const LENGTH: Option<usize> = None;

    fn describe<Visitor>(visitor: &mut Visitor)
    where
        Visitor: KeyVisitor,
    {
        visitor.visit_composite(
            CompositeKind::Struct(Cow::Borrowed("std::time::SystemTime")),
            1,
        );
        visitor.visit_type(KeyKind::Unsigned);
    }

    fn as_ord_bytes(&self) -> Result<Cow<'_, [u8]>, Self::Error> {
        let since_epoch = self.duration_since(UNIX_EPOCH).unwrap();
        match since_epoch.as_ord_bytes()? {
            Cow::Owned(bytes) => Ok(Cow::Owned(bytes)),
            Cow::Borrowed(_) => unreachable!(),
        }
    }
}

#[test]
fn system_time_tests() {
    assert_eq!(
        UNIX_EPOCH,
        SystemTime::from_ord_bytes(ByteSource::Borrowed(&UNIX_EPOCH.as_ord_bytes().unwrap()))
            .unwrap()
    );
    let now = SystemTime::now();
    assert_eq!(
        now,
        SystemTime::from_ord_bytes(ByteSource::Borrowed(&now.as_ord_bytes().unwrap())).unwrap()
    );
}

/// An error that indicates that the stored timestamp is unable to be converted
/// to the destination type without losing data.
#[derive(thiserror::Error, Debug)]
#[error("the stored timestamp is outside the allowed range")]
pub struct DeltaNotRepresentable;

/// Errors that can arise from parsing times serialized with [`Key`].
#[derive(thiserror::Error, Debug, Clone, Serialize, Deserialize)]
pub enum TimeError {
    /// An error that indicates that the stored timestamp is unable to be converted
    /// to the destination type without losing data.
    #[error("the stored timestamp is outside the allowed range")]
    DeltaNotRepresentable,
    /// The value stored was not encoded correctly.
    #[error("invalid value")]
    InvalidValue,
}

impl From<DeltaNotRepresentable> for TimeError {
    fn from(_: DeltaNotRepresentable) -> Self {
        Self::DeltaNotRepresentable
    }
}

impl From<std::io::Error> for TimeError {
    fn from(_: std::io::Error) -> Self {
        Self::InvalidValue
    }
}

/// Types for storing limited-precision Durations.
pub mod limited {
    use std::borrow::Cow;
    use std::fmt::{self, Debug, Display, Write};
    use std::hash::Hash;
    use std::iter;
    use std::marker::PhantomData;
    use std::str::FromStr;
    use std::time::{Duration, SystemTime, UNIX_EPOCH};

    use derive_where::derive_where;
    use ordered_varint::Variable;
    use serde::{Deserialize, Serialize};

    use crate::key::time::TimeError;
    use crate::key::{ByteSource, CompositeKind, Key, KeyEncoding, KeyVisitor};

    /// A [`Duration`] of time stored with a limited `Resolution`. This type may be
    /// preferred to [`std::time::Duration`] because `Duration` takes a full 12
    /// bytes to achieve its nanosecond resolution.
    ///
    /// Converting from [`Duration`] truncates the duration and performs no rounding.
    ///
    /// The `Resolution` type controls the storage size. The resolutions
    /// provided by BonsaiDb:
    ///
    /// - [`Weeks`]
    /// - [`Days`]
    /// - [`Hours`]
    /// - [`Minutes`]
    /// - [`Seconds`]
    /// - [`Milliseconds`]
    /// - [`Microseconds`]
    /// - [`Nanoseconds`]
    ///
    /// Other resolutions can be used by implementing [`TimeResolution`].
    #[derive_where(Hash, Eq, PartialEq, Ord, PartialOrd, Clone, Copy)]
    pub struct LimitedResolutionDuration<Resolution: TimeResolution> {
        representation: Resolution::Representation,
        _resolution: PhantomData<Resolution>,
    }

    /// A resolution of a time measurement.
    pub trait TimeResolution: Debug + Send + Sync {
        /// The in-memory and serialized representation for this resolution.
        type Representation: Variable
            + Serialize
            + for<'de> Deserialize<'de>
            + for<'k> Key<'k>
            + Display
            + Hash
            + Eq
            + PartialEq
            + Ord
            + PartialOrd
            + Clone
            + Copy
            + Send
            + Sync
            + Debug
            + Default;

        /// The label used when formatting times with this resolution.
        const FORMAT_SUFFIX: &'static str;

        /// Converts a [`Self::Representation`] to [`Duration`].
        fn repr_to_duration(value: Self::Representation) -> Result<SignedDuration, TimeError>;

        /// Converts a [`Duration`] to [`Self::Representation`].
        fn duration_to_repr(duration: SignedDuration) -> Result<Self::Representation, TimeError>;
    }

    /// A [`Duration`] that can be either negative or positive.
    #[derive(Copy, Clone, Debug, Eq, PartialEq)]
    pub enum SignedDuration {
        /// A duration representing a positive measurement of time.
        Positive(Duration),
        /// A duration representing a negative measurement of time.
        Negative(Duration),
    }

    impl SignedDuration {
        /// Adds the two durations, honoring the signs, and returns the result
        /// if the duration is representable.
        #[must_use]
        pub fn checked_add(self, other: Self) -> Option<Self> {
            match (self, other) {
                (SignedDuration::Positive(a), SignedDuration::Positive(b)) => {
                    a.checked_add(b).map(SignedDuration::Positive)
                }
                (SignedDuration::Negative(a), SignedDuration::Negative(b)) => {
                    a.checked_add(b).map(SignedDuration::Negative)
                }
                (SignedDuration::Positive(a), SignedDuration::Negative(b)) => {
                    if let Some(result) = a.checked_sub(b) {
                        Some(SignedDuration::Positive(result))
                    } else {
                        Some(SignedDuration::Negative(b - a))
                    }
                }
                (SignedDuration::Negative(a), SignedDuration::Positive(b)) => {
                    if let Some(result) = a.checked_sub(b) {
                        Some(SignedDuration::Negative(result))
                    } else {
                        Some(SignedDuration::Positive(b - a))
                    }
                }
            }
        }
    }

    impl<Resolution> LimitedResolutionDuration<Resolution>
    where
        Resolution: TimeResolution,
    {
        /// Returns a new instance with the `representation` provided, which
        /// conceptually is a unit of `Resolution`.
        pub const fn new(representation: Resolution::Representation) -> Self {
            Self {
                representation,
                _resolution: PhantomData,
            }
        }

        /// Returns the internal representation of this duration.
        pub const fn representation(&self) -> Resolution::Representation {
            self.representation
        }
    }

    impl<Resolution: TimeResolution> Debug for LimitedResolutionDuration<Resolution> {
        fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
            write!(f, "{:?}{}", self.representation, Resolution::FORMAT_SUFFIX)
        }
    }

    impl<Resolution: TimeResolution> Display for LimitedResolutionDuration<Resolution> {
        fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
            write!(f, "{}{}", self.representation, Resolution::FORMAT_SUFFIX)
        }
    }

    impl iter::Sum<SignedDuration> for Option<SignedDuration> {
        fn sum<I: Iterator<Item = SignedDuration>>(mut iter: I) -> Self {
            let first = iter.next();
            iter.fold(first, |sum, duration| {
                sum.and_then(|sum| sum.checked_add(duration))
            })
        }
    }

    impl iter::Sum<Self> for SignedDuration {
        fn sum<I: Iterator<Item = Self>>(iter: I) -> Self {
            iter.sum::<Option<Self>>().expect("operation overflowed")
        }
    }

    impl<'k, Resolution> Key<'k> for LimitedResolutionDuration<Resolution>
    where
        Resolution: TimeResolution,
    {
        const CAN_OWN_BYTES: bool = false;

        fn from_ord_bytes<'e>(bytes: ByteSource<'k, 'e>) -> Result<Self, Self::Error> {
            let representation =
                <Resolution::Representation as Variable>::decode_variable(bytes.as_ref())
                    .map_err(|_| TimeError::InvalidValue)?;

            Ok(Self {
                representation,
                _resolution: PhantomData,
            })
        }
    }

    impl<Resolution> KeyEncoding<Self> for LimitedResolutionDuration<Resolution>
    where
        Resolution: TimeResolution,
    {
        type Error = TimeError;

        const LENGTH: Option<usize> = None;

        fn describe<Visitor>(visitor: &mut Visitor)
        where
            Visitor: KeyVisitor,
        {
            visitor.visit_composite(
                CompositeKind::Struct(Cow::Borrowed(
                    "bonsaidb::core::key::time::LimitedResolutionDuration",
                )),
                1,
            );
            <Resolution::Representation as KeyEncoding>::describe(visitor);
        }

        fn as_ord_bytes(&self) -> Result<Cow<'_, [u8]>, Self::Error> {
            self.representation
                .to_variable_vec()
                .map(Cow::Owned)
                .map_err(|_| TimeError::InvalidValue)
        }
    }

    impl<Resolution> Default for LimitedResolutionDuration<Resolution>
    where
        Resolution: TimeResolution,
    {
        fn default() -> Self {
            Self {
                representation: <Resolution::Representation as Default>::default(),
                _resolution: PhantomData,
            }
        }
    }

    impl<Resolution> Serialize for LimitedResolutionDuration<Resolution>
    where
        Resolution: TimeResolution,
    {
        fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
        where
            S: serde::Serializer,
        {
            self.representation.serialize(serializer)
        }
    }

    impl<'de, Resolution> Deserialize<'de> for LimitedResolutionDuration<Resolution>
    where
        Resolution: TimeResolution,
    {
        fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
        where
            D: serde::Deserializer<'de>,
        {
            <Resolution::Representation as Deserialize<'de>>::deserialize(deserializer)
                .map(Self::new)
        }
    }

    impl<Resolution> TryFrom<SignedDuration> for LimitedResolutionDuration<Resolution>
    where
        Resolution: TimeResolution,
    {
        type Error = TimeError;

        fn try_from(duration: SignedDuration) -> Result<Self, Self::Error> {
            Resolution::duration_to_repr(duration).map(|representation| Self {
                representation,
                _resolution: PhantomData,
            })
        }
    }

    impl<Resolution> TryFrom<LimitedResolutionDuration<Resolution>> for SignedDuration
    where
        Resolution: TimeResolution,
    {
        type Error = TimeError;

        fn try_from(value: LimitedResolutionDuration<Resolution>) -> Result<Self, Self::Error> {
            Resolution::repr_to_duration(value.representation)
        }
    }

    impl<Resolution> TryFrom<Duration> for LimitedResolutionDuration<Resolution>
    where
        Resolution: TimeResolution,
    {
        type Error = TimeError;

        fn try_from(duration: Duration) -> Result<Self, Self::Error> {
            Self::try_from(SignedDuration::Positive(duration))
        }
    }

    impl<Resolution> TryFrom<LimitedResolutionDuration<Resolution>> for Duration
    where
        Resolution: TimeResolution,
    {
        type Error = TimeError;

        fn try_from(value: LimitedResolutionDuration<Resolution>) -> Result<Self, Self::Error> {
            match SignedDuration::try_from(value) {
                Ok(SignedDuration::Positive(value)) => Ok(value),
                _ => Err(TimeError::DeltaNotRepresentable),
            }
        }
    }

    impl<Resolution> iter::Sum<LimitedResolutionDuration<Resolution>>
        for Option<LimitedResolutionDuration<Resolution>>
    where
        Resolution: TimeResolution,
    {
        fn sum<I: Iterator<Item = LimitedResolutionDuration<Resolution>>>(mut iter: I) -> Self {
            let first = iter
                .next()
                .and_then(|dur| Resolution::repr_to_duration(dur.representation).ok());
            let duration = iter.fold(first, |sum, dur| {
                sum.and_then(|sum| {
                    Resolution::repr_to_duration(dur.representation)
                        .ok()
                        .and_then(|dur| sum.checked_add(dur))
                })
            });
            duration.and_then(|dur| {
                Resolution::duration_to_repr(dur)
                    .ok()
                    .map(LimitedResolutionDuration::new)
            })
        }
    }

    impl<Resolution> iter::Sum<Self> for LimitedResolutionDuration<Resolution>
    where
        Resolution: TimeResolution,
    {
        fn sum<I: Iterator<Item = Self>>(iter: I) -> Self {
            iter.sum::<Option<Self>>().expect("operation overflowed")
        }
    }

    #[test]
    fn limited_resolution_duration_sum() {
        use super::Nanoseconds;
        assert_eq!(
            [
                Nanoseconds::new(1),
                Nanoseconds::new(2),
                Nanoseconds::new(3),
            ]
            .into_iter()
            .sum::<Nanoseconds>(),
            Nanoseconds::new(6)
        );
        assert_eq!(
            [
                Nanoseconds::new(1),
                Nanoseconds::new(2),
                Nanoseconds::new(3),
            ]
            .into_iter()
            .sum::<Option<Nanoseconds>>(),
            Some(Nanoseconds::new(6))
        );

        assert_eq!(
            [Nanoseconds::new(1), Nanoseconds::new(i64::MAX)]
                .into_iter()
                .sum::<Option<Nanoseconds>>(),
            None
        );

        assert_eq!(
            [Nanoseconds::new(i64::MAX), Nanoseconds::new(1)]
                .into_iter()
                .sum::<Option<Nanoseconds>>(),
            None
        );

        assert_eq!(
            [Nanoseconds::new(i64::MIN), Nanoseconds::new(-11)]
                .into_iter()
                .sum::<Option<Nanoseconds>>(),
            None
        );

        assert_eq!(
            [Nanoseconds::new(1), Nanoseconds::new(i64::MIN)]
                .into_iter()
                .sum::<Option<Nanoseconds>>(),
            Some(Nanoseconds::new(i64::MIN + 1))
        );
        assert_eq!(
            [Nanoseconds::new(i64::MIN), Nanoseconds::new(1)]
                .into_iter()
                .sum::<Option<Nanoseconds>>(),
            Some(Nanoseconds::new(i64::MIN + 1))
        );
    }

    /// A [`TimeResolution`] implementation that preserves nanosecond
    /// resolution. Internally, the number of microseconds is represented as an
    /// `i64`, allowing a range of +/- ~292.5 years.
    #[derive(Debug)]
    pub enum Nanoseconds {}

    const I64_MIN_ABS_AS_U64: u64 = 9_223_372_036_854_775_808;

    impl TimeResolution for Nanoseconds {
        type Representation = i64;

        const FORMAT_SUFFIX: &'static str = "ns";

        fn repr_to_duration(value: Self::Representation) -> Result<SignedDuration, TimeError> {
            if let Ok(unsigned) = u64::try_from(value) {
                Ok(SignedDuration::Positive(Duration::from_nanos(unsigned)))
            } else {
                let positive = value
                    .checked_abs()
                    .and_then(|value| u64::try_from(value).ok())
                    .unwrap_or(I64_MIN_ABS_AS_U64);
                Ok(SignedDuration::Negative(Duration::from_nanos(positive)))
            }
        }

        fn duration_to_repr(duration: SignedDuration) -> Result<Self::Representation, TimeError> {
            match duration {
                SignedDuration::Positive(duration) => {
                    i64::try_from(duration.as_nanos()).map_err(|_| TimeError::DeltaNotRepresentable)
                }
                SignedDuration::Negative(duration) => {
                    let nanos = duration.as_nanos();
                    if let Ok(nanos) = i64::try_from(nanos) {
                        Ok(-nanos)
                    } else if nanos == u128::from(I64_MIN_ABS_AS_U64) {
                        Ok(i64::MIN)
                    } else {
                        Err(TimeError::DeltaNotRepresentable)
                    }
                }
            }
        }
    }

    /// A [`TimeResolution`] implementation that truncates time measurements to
    /// microseconds. Internally, the number of microseconds is represented as
    /// an `i64`, allowing a range of +/- ~292,471 years.
    #[derive(Debug)]
    pub enum Microseconds {}

    impl TimeResolution for Microseconds {
        type Representation = i64;

        const FORMAT_SUFFIX: &'static str = "us";

        fn repr_to_duration(value: Self::Representation) -> Result<SignedDuration, TimeError> {
            if let Ok(unsigned) = u64::try_from(value) {
                Ok(SignedDuration::Positive(Duration::from_micros(unsigned)))
            } else {
                let positive = value
                    .checked_abs()
                    .and_then(|value| u64::try_from(value).ok())
                    .unwrap_or(u64::MAX);
                Ok(SignedDuration::Negative(Duration::from_micros(positive)))
            }
        }

        fn duration_to_repr(duration: SignedDuration) -> Result<Self::Representation, TimeError> {
            match duration {
                SignedDuration::Positive(duration) => i64::try_from(duration.as_micros())
                    .map_err(|_| TimeError::DeltaNotRepresentable),
                SignedDuration::Negative(duration) => {
                    let rounded_up = duration
                        .checked_add(Duration::from_nanos(999))
                        .ok_or(TimeError::DeltaNotRepresentable)?;
                    i64::try_from(rounded_up.as_micros())
                        .map(|repr| -repr)
                        .map_err(|_| TimeError::DeltaNotRepresentable)
                }
            }
        }
    }

    /// A [`TimeResolution`] implementation that truncates time measurements to
    /// milliseconds. Internally, the number of milliseconds is represented as
    /// an `i64`, allowing a range of +/- ~292.5 million years.
    #[derive(Debug)]
    pub enum Milliseconds {}

    impl TimeResolution for Milliseconds {
        type Representation = i64;

        const FORMAT_SUFFIX: &'static str = "ms";

        fn repr_to_duration(value: Self::Representation) -> Result<SignedDuration, TimeError> {
            if let Ok(unsigned) = u64::try_from(value) {
                Ok(SignedDuration::Positive(Duration::from_millis(unsigned)))
            } else {
                let positive = value
                    .checked_abs()
                    .and_then(|value| u64::try_from(value).ok())
                    .unwrap_or(u64::MAX);
                Ok(SignedDuration::Negative(Duration::from_millis(positive)))
            }
        }

        fn duration_to_repr(duration: SignedDuration) -> Result<Self::Representation, TimeError> {
            match duration {
                SignedDuration::Positive(duration) => i64::try_from(duration.as_millis())
                    .map_err(|_| TimeError::DeltaNotRepresentable),
                SignedDuration::Negative(duration) => {
                    let rounded_up = duration
                        .checked_add(Duration::from_nanos(999_999))
                        .ok_or(TimeError::DeltaNotRepresentable)?;
                    i64::try_from(rounded_up.as_millis())
                        .map(|repr| -repr)
                        .map_err(|_| TimeError::DeltaNotRepresentable)
                }
            }
        }
    }

    /// A [`TimeResolution`] implementation that truncates time measurements to
    /// seconds. Internally, the number of seconds is represented as an `i64`,
    /// allowing a range of +/- ~21 times the age of the universe.
    #[derive(Debug)]
    pub enum Seconds {}

    impl TimeResolution for Seconds {
        type Representation = i64;

        const FORMAT_SUFFIX: &'static str = "s";

        fn repr_to_duration(value: Self::Representation) -> Result<SignedDuration, TimeError> {
            if let Ok(unsigned) = u64::try_from(value) {
                Ok(SignedDuration::Positive(Duration::from_secs(unsigned)))
            } else {
                let positive = value
                    .checked_abs()
                    .and_then(|value| u64::try_from(value).ok())
                    .unwrap_or(u64::MAX);
                Ok(SignedDuration::Negative(Duration::from_secs(positive)))
            }
        }

        fn duration_to_repr(duration: SignedDuration) -> Result<Self::Representation, TimeError> {
            match duration {
                SignedDuration::Positive(duration) => {
                    i64::try_from(duration.as_secs()).map_err(|_| TimeError::DeltaNotRepresentable)
                }
                SignedDuration::Negative(duration) => {
                    let rounded_up = duration
                        .checked_add(Duration::from_nanos(999_999_999))
                        .ok_or(TimeError::DeltaNotRepresentable)?;
                    i64::try_from(rounded_up.as_secs())
                        .map(|repr| -repr)
                        .map_err(|_| TimeError::DeltaNotRepresentable)
                }
            }
        }
    }

    /// A [`TimeResolution`] implementation that truncates time measurements to
    /// minutes. Internally, the number of minutes is represented as an `i32`,
    /// allowing a range of +/- ~4,086 years.
    #[derive(Debug)]
    pub enum Minutes {}

    impl TimeResolution for Minutes {
        type Representation = i32;

        const FORMAT_SUFFIX: &'static str = "m";

        fn repr_to_duration(value: Self::Representation) -> Result<SignedDuration, TimeError> {
            if let Ok(unsigned) = u64::try_from(value) {
                Ok(SignedDuration::Positive(Duration::from_secs(unsigned * 60)))
            } else {
                let positive = u64::try_from(i64::from(value).abs()).unwrap();
                Ok(SignedDuration::Negative(Duration::from_secs(positive * 60)))
            }
        }

        fn duration_to_repr(duration: SignedDuration) -> Result<Self::Representation, TimeError> {
            match duration {
                SignedDuration::Positive(duration) => i32::try_from(duration.as_secs() / 60)
                    .map_err(|_| TimeError::DeltaNotRepresentable),
                SignedDuration::Negative(duration) => i32::try_from((duration.as_secs() + 59) / 60)
                    .map(|repr| -repr)
                    .map_err(|_| TimeError::DeltaNotRepresentable),
            }
        }
    }

    /// A [`TimeResolution`] implementation that truncates time measurements to
    /// hours. Internally, the number of hours is represented as an `i32`,
    /// allowing a range of +/- ~245,147 years.
    #[derive(Debug)]
    pub enum Hours {}

    impl TimeResolution for Hours {
        type Representation = i32;

        const FORMAT_SUFFIX: &'static str = "h";

        fn repr_to_duration(value: Self::Representation) -> Result<SignedDuration, TimeError> {
            if let Ok(unsigned) = u64::try_from(value) {
                Ok(SignedDuration::Positive(Duration::from_secs(
                    unsigned * 60 * 60,
                )))
            } else {
                let positive = u64::try_from(i64::from(value).abs()).unwrap();
                Ok(SignedDuration::Negative(Duration::from_secs(
                    positive * 60 * 60,
                )))
            }
        }

        fn duration_to_repr(duration: SignedDuration) -> Result<Self::Representation, TimeError> {
            const FACTOR: u64 = 60 * 60;
            match duration {
                SignedDuration::Positive(duration) => i32::try_from(duration.as_secs() / FACTOR)
                    .map_err(|_| TimeError::DeltaNotRepresentable),
                SignedDuration::Negative(duration) => {
                    i32::try_from((duration.as_secs() + FACTOR - 1) / FACTOR)
                        .map(|repr| -repr)
                        .map_err(|_| TimeError::DeltaNotRepresentable)
                }
            }
        }
    }

    /// A [`TimeResolution`] implementation that truncates time measurements to
    /// days. Internally, the number of days is represented as an `i32`,
    /// allowing a range of +/- ~5.88 million years.
    #[derive(Debug)]
    pub enum Days {}

    impl TimeResolution for Days {
        type Representation = i32;

        const FORMAT_SUFFIX: &'static str = "d";

        fn repr_to_duration(value: Self::Representation) -> Result<SignedDuration, TimeError> {
            if let Ok(unsigned) = u64::try_from(value) {
                Ok(SignedDuration::Positive(Duration::from_secs(
                    unsigned * 24 * 60 * 60,
                )))
            } else {
                let positive = u64::try_from(i64::from(value).abs()).unwrap();
                Ok(SignedDuration::Negative(Duration::from_secs(
                    positive * 24 * 60 * 60,
                )))
            }
        }

        fn duration_to_repr(duration: SignedDuration) -> Result<Self::Representation, TimeError> {
            const FACTOR: u64 = 24 * 60 * 60;
            match duration {
                SignedDuration::Positive(duration) => i32::try_from(duration.as_secs() / FACTOR)
                    .map_err(|_| TimeError::DeltaNotRepresentable),
                SignedDuration::Negative(duration) => {
                    Ok(i32::try_from((duration.as_secs() + FACTOR - 1) / FACTOR)
                        .map_or(i32::MIN, |repr| -repr))
                }
            }
        }
    }

    /// A [`TimeResolution`] implementation that truncates time measurements to
    /// weeks. Internally, the number of weeks is represented as an `i32`,
    /// allowing a range of +/- ~41.18 million years.
    #[derive(Debug)]
    pub enum Weeks {}

    impl TimeResolution for Weeks {
        type Representation = i32;

        const FORMAT_SUFFIX: &'static str = "w";

        fn repr_to_duration(value: Self::Representation) -> Result<SignedDuration, TimeError> {
            if let Ok(unsigned) = u64::try_from(value) {
                Ok(SignedDuration::Positive(Duration::from_secs(
                    unsigned * 7 * 24 * 60 * 60,
                )))
            } else {
                let positive = u64::try_from(i64::from(value).abs()).unwrap();
                Ok(SignedDuration::Negative(Duration::from_secs(
                    positive * 7 * 24 * 60 * 60,
                )))
            }
        }

        fn duration_to_repr(duration: SignedDuration) -> Result<Self::Representation, TimeError> {
            const FACTOR: u64 = 7 * 24 * 60 * 60;
            match duration {
                SignedDuration::Positive(duration) => i32::try_from(duration.as_secs() / FACTOR)
                    .map_err(|_| TimeError::DeltaNotRepresentable),
                SignedDuration::Negative(duration) => {
                    i32::try_from((duration.as_secs() + FACTOR - 1) / FACTOR)
                        .map(|repr| -repr)
                        .map_err(|_| TimeError::DeltaNotRepresentable)
                }
            }
        }
    }

    #[test]
    fn limited_resolution_duration_tests() {
        fn test_limited<Resolution: TimeResolution>(
            duration: Duration,
            expected_step: Resolution::Representation,
        ) {
            let limited = LimitedResolutionDuration::<Resolution>::try_from(duration).unwrap();
            assert_eq!(limited.representation, expected_step);
            let encoded = limited.as_ord_bytes().unwrap();
            println!("Encoded {limited:?} to {} bytes", encoded.len());
            let decoded =
                LimitedResolutionDuration::from_ord_bytes(ByteSource::Borrowed(&encoded)).unwrap();
            assert_eq!(limited, decoded);
        }

        fn test_eq_limited<Resolution: TimeResolution>(
            duration: Duration,
            expected_step: Resolution::Representation,
        ) {
            test_limited::<Resolution>(duration, expected_step);
            let limited = LimitedResolutionDuration::<Resolution>::try_from(duration).unwrap();
            assert_eq!(duration, Duration::try_from(limited).unwrap());
        }

        let truncating_seconds = 7 * 24 * 60 * 60 + 24 * 60 * 60 + 60 * 60 + 60 + 1;
        let truncating = Duration::new(u64::try_from(truncating_seconds).unwrap(), 987_654_321);
        test_limited::<Weeks>(truncating, 1);
        test_limited::<Days>(truncating, 8);
        test_limited::<Hours>(truncating, 8 * 24 + 1);
        test_limited::<Minutes>(truncating, 8 * 24 * 60 + 60 + 1);
        test_limited::<Seconds>(truncating, 8 * 24 * 60 * 60 + 60 * 60 + 60 + 1);
        test_limited::<Milliseconds>(truncating, truncating_seconds * 1_000 + 987);
        test_limited::<Microseconds>(truncating, truncating_seconds * 1_000_000 + 987_654);

        let forty_two_days = Duration::from_secs(42 * 24 * 60 * 60);
        test_eq_limited::<Weeks>(forty_two_days, 6);
        test_eq_limited::<Days>(forty_two_days, 42);
        test_eq_limited::<Hours>(forty_two_days, 42 * 24);
        test_eq_limited::<Minutes>(forty_two_days, 42 * 24 * 60);
        test_eq_limited::<Seconds>(forty_two_days, 42 * 24 * 60 * 60);
        test_eq_limited::<Milliseconds>(forty_two_days, 42 * 24 * 60 * 60 * 1_000);
        test_eq_limited::<Microseconds>(forty_two_days, 42 * 24 * 60 * 60 * 1_000_000);
    }

    /// A timestamp (moment in time) stored with a limited `Resolution`. This
    /// type may be preferred to [`std::time::SystemTime`] because `SystemTime`
    /// serializes with nanosecond resolution. Often this level of precision is
    /// not needed and less storage and memory can be used.
    ///
    /// This type stores the representation of the timestamp as a
    /// [`LimitedResolutionDuration`] relative to `Epoch`.
    ///
    /// The `Resolution` type controls the storage size. The resolutions
    /// provided by BonsaiDb:
    ///
    /// - [`Weeks`]
    /// - [`Days`]
    /// - [`Hours`]
    /// - [`Minutes`]
    /// - [`Seconds`]
    /// - [`Milliseconds`]
    /// - [`Microseconds`]
    /// - [`Nanoseconds`]
    ///
    /// Other resolutions can be used by implementing [`TimeResolution`].
    /// BonsaiDb provides two [`TimeEpoch`] implementations:
    ///
    /// - [`UnixEpoch`]
    /// - [`BonsaiEpoch`]
    #[derive_where(Hash, Eq, PartialEq, Ord, PartialOrd, Clone, Copy)]
    pub struct LimitedResolutionTimestamp<Resolution: TimeResolution, Epoch: TimeEpoch>(
        LimitedResolutionDuration<Resolution>,
        PhantomData<Epoch>,
    );

    impl<Resolution, Epoch> Default for LimitedResolutionTimestamp<Resolution, Epoch>
    where
        Resolution: TimeResolution,
        Epoch: TimeEpoch,
    {
        fn default() -> Self {
            Self(LimitedResolutionDuration::default(), PhantomData)
        }
    }

    impl<Resolution, Epoch> Serialize for LimitedResolutionTimestamp<Resolution, Epoch>
    where
        Resolution: TimeResolution,
        Epoch: TimeEpoch,
    {
        fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
        where
            S: serde::Serializer,
        {
            self.0.serialize(serializer)
        }
    }

    impl<'de, Resolution, Epoch> Deserialize<'de> for LimitedResolutionTimestamp<Resolution, Epoch>
    where
        Resolution: TimeResolution,
        Epoch: TimeEpoch,
    {
        fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
        where
            D: serde::Deserializer<'de>,
        {
            LimitedResolutionDuration::deserialize(deserializer)
                .map(|duration| Self(duration, PhantomData))
        }
    }

    /// An epoch for [`LimitedResolutionTimestamp`].
    pub trait TimeEpoch: Sized + Send + Sync {
        /// The name of this epoch, used in [`KeyEncoding::describe`] to
        /// disambiguate timestamps with different epochs.
        fn name() -> &'static str;

        /// The offset from [`UNIX_EPOCH`] for this epoch.
        fn epoch_offset() -> Duration;
    }

    impl<Resolution, Epoch> LimitedResolutionTimestamp<Resolution, Epoch>
    where
        Resolution: TimeResolution,
        Epoch: TimeEpoch,
    {
        /// Returns [`SystemTime::now()`] limited to `Resolution`. The timestamp
        /// will be truncated, not rounded.
        ///
        /// # Panics
        ///
        /// This function will panic [`SystemTime::now()`] is unable to be
        /// represented by `Resolution` and `Epoch`.
        #[must_use]
        pub fn now() -> Self {
            Self::try_from(SystemTime::now()).expect("now should always be representable")
        }

        /// Returns the duration since another timestamp. This returns None if
        /// `other` is before `self`,
        pub fn duration_since(
            &self,
            other: &impl AnyTimestamp,
        ) -> Result<Option<Duration>, TimeError> {
            let self_delta = self.duration_since_unix_epoch()?;
            let other_delta = other.duration_since_unix_epoch()?;
            Ok(self_delta.checked_sub(other_delta))
        }

        /// Returns the absolute duration between `self` and `other`.
        pub fn duration_between(&self, other: &impl AnyTimestamp) -> Result<Duration, TimeError> {
            let self_delta = self.duration_since_unix_epoch()?;
            let other_delta = other.duration_since_unix_epoch()?;
            if self_delta < other_delta {
                Ok(other_delta - self_delta)
            } else {
                Ok(self_delta - other_delta)
            }
        }

        /// Returns the internal representation of this timestamp, which is a
        /// unit of `Resolution`.
        pub const fn representation(&self) -> Resolution::Representation {
            self.0.representation()
        }

        /// Returns a new timestamp using the `representation` provided.
        pub fn from_representation(representation: Resolution::Representation) -> Self {
            Self::from(LimitedResolutionDuration::new(representation))
        }

        /// Converts this value to a a decimal string containing the number of
        /// seconds since the unix epoch (January 1, 1970 00:00:00 UTC).
        ///
        /// The resulting string can be parsed as well.
        ///
        /// ```rust
        /// use bonsaidb_core::key::time::limited::{
        ///     BonsaiEpoch, LimitedResolutionTimestamp, Milliseconds,
        /// };
        ///
        /// let now = LimitedResolutionTimestamp::<Milliseconds, BonsaiEpoch>::now();
        /// let timestamp = now.to_timestamp_string().unwrap();
        /// let parsed = timestamp.parse().unwrap();
        /// assert_eq!(now, parsed);
        /// ```
        ///
        /// The difference between this function and `to_string()`] is that
        /// `to_string()` will revert to using the underlying
        /// [`LimitedResolutionDuration`]'s `to_string()` if a value is unable
        /// to be converted to a value relative to the unix epoch.
        pub fn to_timestamp_string(&self) -> Result<String, TimeError> {
            let mut string = String::new();
            self.display(&mut string).map(|()| string)
        }

        fn display(&self, f: &mut impl Write) -> Result<(), TimeError> {
            let since_epoch = self.duration_since_unix_epoch()?;
            write!(f, "{}", since_epoch.as_secs()).map_err(|_| TimeError::InvalidValue)?;
            if since_epoch.subsec_nanos() > 0 {
                if since_epoch.subsec_nanos() % 1_000_000 == 0 {
                    // Rendering any precision beyond milliseconds will yield 0s
                    write!(f, ".{:03}", since_epoch.subsec_millis())
                        .map_err(|_| TimeError::InvalidValue)
                } else if since_epoch.subsec_nanos() % 1_000 == 0 {
                    write!(f, ".{:06}", since_epoch.subsec_micros())
                        .map_err(|_| TimeError::InvalidValue)
                } else {
                    write!(f, ".{:09}", since_epoch.subsec_nanos())
                        .map_err(|_| TimeError::InvalidValue)
                }
            } else {
                // No subsecond
                Ok(())
            }
        }
    }

    /// A timestamp that can report it sduration since the Unix Epoch.
    pub trait AnyTimestamp {
        /// Returns the [`Duration`] since January 1, 1970 00:00:00 UTC for this
        /// timestamp.
        fn duration_since_unix_epoch(&self) -> Result<Duration, TimeError>;
    }

    impl AnyTimestamp for SystemTime {
        fn duration_since_unix_epoch(&self) -> Result<Duration, TimeError> {
            Ok(self.duration_since(UNIX_EPOCH).unwrap())
        }
    }

    impl<Resolution, Epoch> AnyTimestamp for LimitedResolutionTimestamp<Resolution, Epoch>
    where
        Resolution: TimeResolution,
        Epoch: TimeEpoch,
    {
        fn duration_since_unix_epoch(&self) -> Result<Duration, TimeError> {
            let relative_offset = Resolution::repr_to_duration(self.0.representation)?;
            match relative_offset {
                SignedDuration::Positive(offset) => Epoch::epoch_offset()
                    .checked_add(offset)
                    .ok_or(TimeError::DeltaNotRepresentable),
                SignedDuration::Negative(offset) => Epoch::epoch_offset()
                    .checked_sub(offset)
                    .ok_or(TimeError::DeltaNotRepresentable),
            }
        }
    }

    impl<Resolution, Epoch> Debug for LimitedResolutionTimestamp<Resolution, Epoch>
    where
        Resolution: TimeResolution,
        Epoch: TimeEpoch,
    {
        fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
            write!(f, "LimitedResolutionTimestamp({self})")
        }
    }

    impl<Resolution, Epoch> Display for LimitedResolutionTimestamp<Resolution, Epoch>
    where
        Resolution: TimeResolution,
        Epoch: TimeEpoch,
    {
        fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
            self.display(f).or_else(|_| Display::fmt(&self.0, f))
        }
    }

    impl<Resolution, Epoch> FromStr for LimitedResolutionTimestamp<Resolution, Epoch>
    where
        Resolution: TimeResolution,
        Epoch: TimeEpoch,
    {
        type Err = TimeError;

        fn from_str(s: &str) -> Result<Self, Self::Err> {
            let mut parts = s.split('.');
            let seconds = parts.next().ok_or(TimeError::InvalidValue)?;
            let seconds = seconds
                .parse::<u64>()
                .map_err(|_| TimeError::InvalidValue)?;

            let duration = if let Some(subseconds_str) = parts.next() {
                if subseconds_str.len() > 9 || parts.next().is_some() {
                    return Err(TimeError::InvalidValue);
                }
                let subseconds = subseconds_str
                    .parse::<u32>()
                    .map_err(|_| TimeError::InvalidValue)?;

                let nanos =
                    subseconds * 10_u32.pow(u32::try_from(9 - subseconds_str.len()).unwrap());
                Duration::new(seconds, nanos)
            } else {
                Duration::from_secs(seconds)
            };

            let epoch = Epoch::epoch_offset();
            let duration = if duration < epoch {
                SignedDuration::Negative(epoch - duration)
            } else {
                SignedDuration::Positive(duration - epoch)
            };
            Ok(Self::from(
                LimitedResolutionDuration::<Resolution>::try_from(duration)?,
            ))
        }
    }

    #[test]
    fn timestamp_parse_tests() {
        fn test_roundtrip_parsing<Resolution: TimeResolution>() {
            let original = LimitedResolutionTimestamp::<Resolution, BonsaiEpoch>::now();
            let unix_timestamp = original.to_string();
            let parsed = unix_timestamp.parse().unwrap();
            assert_eq!(
                original, parsed,
                "{original} produced {unix_timestamp}, but parsed {parsed}"
            );
        }

        test_roundtrip_parsing::<Weeks>();
        test_roundtrip_parsing::<Days>();
        test_roundtrip_parsing::<Minutes>();
        test_roundtrip_parsing::<Seconds>();
        test_roundtrip_parsing::<Milliseconds>();
        test_roundtrip_parsing::<Microseconds>();
        test_roundtrip_parsing::<Nanoseconds>();
    }

    impl<'k, Resolution, Epoch> Key<'k> for LimitedResolutionTimestamp<Resolution, Epoch>
    where
        Resolution: TimeResolution,
        Epoch: TimeEpoch,
    {
        const CAN_OWN_BYTES: bool = false;

        fn from_ord_bytes<'e>(bytes: ByteSource<'k, 'e>) -> Result<Self, Self::Error> {
            let duration = LimitedResolutionDuration::<Resolution>::from_ord_bytes(bytes)?;
            Ok(Self::from(duration))
        }
    }

    impl<Resolution, Epoch> KeyEncoding<Self> for LimitedResolutionTimestamp<Resolution, Epoch>
    where
        Resolution: TimeResolution,
        Epoch: TimeEpoch,
    {
        type Error = TimeError;

        const LENGTH: Option<usize> = None;

        fn describe<Visitor>(visitor: &mut Visitor)
        where
            Visitor: KeyVisitor,
        {
            visitor.visit_composite(
                CompositeKind::Struct(Cow::Borrowed(
                    "bonsaidb::core::key::time::LimitedResolutionTimestamp",
                )),
                1,
            );
            visitor.visit_composite_attribute("epoch", Epoch::epoch_offset().as_nanos());
            <Resolution::Representation as KeyEncoding>::describe(visitor);
        }

        fn as_ord_bytes(&self) -> Result<Cow<'_, [u8]>, Self::Error> {
            self.0.as_ord_bytes()
        }
    }

    impl<Resolution, Epoch> From<LimitedResolutionDuration<Resolution>>
        for LimitedResolutionTimestamp<Resolution, Epoch>
    where
        Resolution: TimeResolution,
        Epoch: TimeEpoch,
    {
        fn from(duration: LimitedResolutionDuration<Resolution>) -> Self {
            Self(duration, PhantomData)
        }
    }

    impl<Resolution, Epoch> From<LimitedResolutionTimestamp<Resolution, Epoch>>
        for LimitedResolutionDuration<Resolution>
    where
        Resolution: TimeResolution,
        Epoch: TimeEpoch,
    {
        fn from(time: LimitedResolutionTimestamp<Resolution, Epoch>) -> Self {
            time.0
        }
    }

    impl<Resolution, Epoch> TryFrom<SystemTime> for LimitedResolutionTimestamp<Resolution, Epoch>
    where
        Resolution: TimeResolution,
        Epoch: TimeEpoch,
    {
        type Error = TimeError;

        fn try_from(time: SystemTime) -> Result<Self, TimeError> {
            let epoch = UNIX_EPOCH
                .checked_add(Epoch::epoch_offset())
                .ok_or(TimeError::DeltaNotRepresentable)?;
            match time.duration_since(epoch) {
                Ok(duration) => {
                    LimitedResolutionDuration::try_from(SignedDuration::Positive(duration))
                        .map(Self::from)
                }
                Err(_) => match epoch.duration_since(time) {
                    Ok(duration) => {
                        LimitedResolutionDuration::try_from(SignedDuration::Negative(duration))
                            .map(Self::from)
                    }
                    Err(_) => Err(TimeError::DeltaNotRepresentable),
                },
            }
        }
    }

    impl<Resolution, Epoch> TryFrom<LimitedResolutionTimestamp<Resolution, Epoch>> for SystemTime
    where
        Resolution: TimeResolution,
        Epoch: TimeEpoch,
    {
        type Error = TimeError;

        fn try_from(
            time: LimitedResolutionTimestamp<Resolution, Epoch>,
        ) -> Result<Self, TimeError> {
            let since_epoch = SignedDuration::try_from(time.0)?;
            let epoch = UNIX_EPOCH
                .checked_add(Epoch::epoch_offset())
                .ok_or(TimeError::DeltaNotRepresentable)?;
            let time = match since_epoch {
                SignedDuration::Positive(since_epoch) => epoch.checked_add(since_epoch),
                SignedDuration::Negative(since_epoch) => epoch.checked_sub(since_epoch),
            };

            time.ok_or(TimeError::DeltaNotRepresentable)
        }
    }

    /// A [`TimeEpoch`] implementation that allows storing
    /// [`LimitedResolutionTimestamp`] relative to the "unix epoch": January 1,
    /// 1970 00:00:00 UTC.
    pub struct UnixEpoch;

    impl TimeEpoch for UnixEpoch {
        fn name() -> &'static str {
            "Unix"
        }

        fn epoch_offset() -> Duration {
            Duration::ZERO
        }
    }

    /// A [`TimeEpoch`] implementation that allows storing
    /// [`LimitedResolutionTimestamp`] relative to the 10-year anniversary of
    /// BonsaiDb: March 20, 2031 04:31:47 UTC.
    ///
    /// ## Why use [`BonsaiEpoch`] instead of [`UnixEpoch`]?
    ///
    /// [`LimitedResolutionTimestamp`] uses [`ordered-varint::Variable`] to
    /// implement [`Key`], which encodes the underlying value in as few bytes as
    /// possible while still preserving the ordering required by [`Key`].
    ///
    /// Many applications are not storing timestamps that predate the
    /// application being developed. When there is a likelihood that timestamps
    /// are closer to "now" than they are to the unix timestamp (January 1, 1970
    /// 00:00:00 UTC), the [`BonsaiEpoch`] will consistently encode the
    /// underlying representation in fewer bytes than when using [`UnixEpoch`].
    ///
    /// We hope BonsaiDb is a viable database option for many years. By setting
    /// this epoch 10 years from the start of BonsaiDb, it allows the internal
    /// representation of timestamps to slowly decrease in size until the
    /// 10-year anniversary. Over the following 10 years, the size will grow
    /// back to the same size it was at its conception, and then slowly grow as
    /// needed from that point on.
    pub struct BonsaiEpoch;

    impl BonsaiEpoch {
        const EPOCH: Duration = Duration::new(1_931_747_507, 0);
    }

    impl TimeEpoch for BonsaiEpoch {
        fn name() -> &'static str {
            "BonsaiDb"
        }

        fn epoch_offset() -> Duration {
            Self::EPOCH
        }
    }

    #[test]
    fn limited_resolution_timestamp_tests() {
        fn test_resolution<Resolution: TimeResolution>(resolution: Duration) {
            let now_in_seconds = LimitedResolutionTimestamp::<Resolution, UnixEpoch>::now();
            let as_system = SystemTime::try_from(now_in_seconds).unwrap();
            let as_limited =
                LimitedResolutionTimestamp::<Resolution, UnixEpoch>::try_from(as_system).unwrap();
            assert_eq!(as_limited, now_in_seconds);

            let now_in_seconds = LimitedResolutionTimestamp::<Resolution, BonsaiEpoch>::now();
            let as_system = SystemTime::try_from(now_in_seconds).unwrap();
            let as_limited =
                LimitedResolutionTimestamp::<Resolution, BonsaiEpoch>::try_from(as_system).unwrap();
            assert_eq!(as_limited, now_in_seconds);

            let slightly_before_epoch = UNIX_EPOCH + BonsaiEpoch::EPOCH
                - Duration::from_nanos(u64::try_from(resolution.as_nanos() / 2).unwrap());
            let unix_epoch_in_recent =
                LimitedResolutionTimestamp::<Resolution, BonsaiEpoch>::try_from(
                    slightly_before_epoch,
                )
                .unwrap();
            let as_system = SystemTime::try_from(unix_epoch_in_recent).unwrap();
            let as_limited =
                LimitedResolutionTimestamp::<Resolution, BonsaiEpoch>::try_from(as_system).unwrap();
            assert!(
                slightly_before_epoch
                    .duration_since(as_system)
                    .expect("timestamp should have been trunctated towards MIN")
                    < resolution
            );
            assert_eq!(as_limited, unix_epoch_in_recent);

            let slightly_after_epoch = UNIX_EPOCH
                + BonsaiEpoch::EPOCH
                + Duration::from_nanos(u64::try_from(resolution.as_nanos() / 2).unwrap());
            let unix_epoch_in_recent =
                LimitedResolutionTimestamp::<Resolution, BonsaiEpoch>::try_from(
                    slightly_after_epoch,
                )
                .unwrap();
            let as_system = SystemTime::try_from(unix_epoch_in_recent).unwrap();
            println!("{slightly_after_epoch:?} converted to {unix_epoch_in_recent} and back as {as_system:?}");
            let as_limited =
                LimitedResolutionTimestamp::<Resolution, BonsaiEpoch>::try_from(as_system).unwrap();
            assert!(
                slightly_after_epoch
                    .duration_since(as_system)
                    .expect("timestamp should have been truncated towards 0")
                    < resolution
            );
            assert_eq!(as_limited, unix_epoch_in_recent);
        }

        test_resolution::<Weeks>(Duration::from_secs(7 * 24 * 60 * 60));
        test_resolution::<Days>(Duration::from_secs(24 * 60 * 60));
        test_resolution::<Hours>(Duration::from_secs(60 * 60));
        test_resolution::<Minutes>(Duration::from_secs(60));
        test_resolution::<Seconds>(Duration::from_secs(1));
        test_resolution::<Milliseconds>(Duration::from_millis(1));
        test_resolution::<Microseconds>(Duration::from_micros(1));
        test_resolution::<Nanoseconds>(Duration::from_nanos(1));
    }

    #[test]
    fn serialization_tests() {
        fn test_serialization<Resolution: TimeResolution>() {
            let original = LimitedResolutionTimestamp::<Resolution, BonsaiEpoch>::now();
            let serialized = pot::to_vec(&original).unwrap();
            let deserialized = pot::from_slice(&serialized).unwrap();
            assert_eq!(original, deserialized);
        }

        test_serialization::<Weeks>();
        test_serialization::<Days>();
        test_serialization::<Hours>();
        test_serialization::<Minutes>();
        test_serialization::<Seconds>();
        test_serialization::<Milliseconds>();
        test_serialization::<Microseconds>();
        test_serialization::<Nanoseconds>();
    }
}

/// A signed duration of time represented in weeks (604,800 seconds).
/// Internally, the number of weeks is represented as an `i32`,
/// allowing a range of +/- ~41.18 million years.
pub type Weeks = limited::LimitedResolutionDuration<limited::Weeks>;

/// A signed duration of time represented in days (86,400 seconds). Internally,
/// the number of days is represented as an `i32`, allowing a range of +/- ~5.88
/// million years.
pub type Days = limited::LimitedResolutionDuration<limited::Days>;

/// A signed duration of time represented in hours (3,600 seconds). Internally,
/// the number of hours is represented as an `i32`, allowing a range of +/-
/// ~245,147 years.
pub type Hours = limited::LimitedResolutionDuration<limited::Hours>;

/// A signed duration of time represented in minutes (60 seconds). Internally,
/// the number of minutes is represented as an `i32`,
/// allowing a range of +/- ~4,086 years.
pub type Minutes = limited::LimitedResolutionDuration<limited::Minutes>;

/// A signed duration of time represented in seconds (with no partial
/// subseconds). Internally, the number of seconds is represented as an `i64`,
/// allowing a range of +/- ~21 times the age of the universe.
pub type Seconds = limited::LimitedResolutionDuration<limited::Seconds>;

/// A signed duration of time represented in milliseconds (1/1,000th of a
/// second). Internally, the number of milliseconds is represented as an `i64`,
/// allowing a range of +/- ~292.5 million years.
pub type Milliseconds = limited::LimitedResolutionDuration<limited::Milliseconds>;

/// A signed duration of time represented in microseconds (1/1,000,000th of a
/// second). Internally, the number of microseconds is represented as an `i64`,
/// allowing a range of +/- ~292,471 years.
pub type Microseconds = limited::LimitedResolutionDuration<limited::Microseconds>;

/// A signed duration of time represented in nanoseconds (1/1,000,000,000th of a
/// second). Internally, the number of microseconds is represented as an `i64`,
/// allowing a range of +/- ~292.5 years.
pub type Nanoseconds = limited::LimitedResolutionDuration<limited::Nanoseconds>;

/// A timestamp stored as the number of weeks (604,800 seconds) relative to
/// [`UnixEpoch`]. Internally, the number of weeks is represented as an `i32`,
/// allowing a range of +/- ~41.18 million years.
pub type WeeksSinceUnixEpoch = limited::LimitedResolutionTimestamp<limited::Weeks, UnixEpoch>;

/// A timestamp stored as the number of days (86,400 seconds) relative to
/// [`UnixEpoch`]. Internally, the number of days is represented as an `i32`,
/// allowing a range of +/- ~5.88 million years.
pub type DaysSinceUnixEpoch = limited::LimitedResolutionTimestamp<limited::Days, UnixEpoch>;

/// A timestamp stored as the number of hours (3,600 seconds) relative to
/// [`UnixEpoch`]. Internally, the number of hours is represented as an `i32`,
/// allowing a range of +/- ~245,147 years.
pub type HoursSinceUnixEpoch = limited::LimitedResolutionTimestamp<limited::Hours, UnixEpoch>;

/// A timestamp stored as the number of minutes (60 seconds) relative to
/// [`UnixEpoch`]. Internally, the number of minutes is represented as an `i32`,
/// allowing a range of +/- ~4,086 years.
pub type MinutesSinceUnixEpoch = limited::LimitedResolutionTimestamp<limited::Minutes, UnixEpoch>;

/// A timestamp stored as the number of seconds (with no partial subseconds)
/// relative to [`UnixEpoch`]. Internally, the number of seconds is represented
/// as an `i64`, allowing a range of +/- ~21 times the age of the universe.
pub type SecondsSinceUnixEpoch = limited::LimitedResolutionTimestamp<limited::Seconds, UnixEpoch>;

/// A timestamp stored as the number of milliseconds (1/1,000th of a second)
/// relative to [`UnixEpoch`]. Internally, the number of milliseconds is
/// represented as an `i64`, allowing a range of +/- ~292.5 million years.
pub type MillisecondsSinceUnixEpoch =
    limited::LimitedResolutionTimestamp<limited::Milliseconds, UnixEpoch>;

/// A timestamp stored as the number of microseconds (1/1,000,000th of a second)
/// relative to [`UnixEpoch`]. Internally, the number of microseconds is
/// represented as an `i64`, allowing a range of +/- ~292,471 years.
pub type MicrosecondsSinceUnixEpoch =
    limited::LimitedResolutionTimestamp<limited::Microseconds, UnixEpoch>;

/// A timestamp stored as the number of nanoseconds (1/1,000,000,000th of a
/// second) relative to [`UnixEpoch`]. Internally, the number of microseconds is
/// represented as an `i64`, allowing a range of +/- ~292.5 years.
pub type NanosecondsSinceUnixEpoch =
    limited::LimitedResolutionTimestamp<limited::Nanoseconds, UnixEpoch>;

/// A timestamp stored as the number of weeks (604,800 seconds) relative to
/// [`BonsaiEpoch`]. Internally, the number of weeks is represented as an `i32`,
/// allowing a range of +/- ~41.18 million years.
pub type TimestampAsWeeks = limited::LimitedResolutionTimestamp<limited::Weeks, BonsaiEpoch>;

/// A timestamp stored as the number of days (86,400 seconds) relative to
/// [`BonsaiEpoch`]. Internally, the number of days is represented as an `i32`,
/// allowing a range of +/- ~5.88 million years.
pub type TimestampAsDays = limited::LimitedResolutionTimestamp<limited::Days, BonsaiEpoch>;

/// A timestamp stored as the number of hours (3,600 seconds) relative to
/// [`BonsaiEpoch`]. Internally, the number of hours is represented as an `i32`,
/// allowing a range of +/- ~245,147 years.
pub type TimestampAsHours = limited::LimitedResolutionTimestamp<limited::Hours, BonsaiEpoch>;

/// A timestamp stored as the number of minutes (60 seconds) relative to
/// [`BonsaiEpoch`]. Internally, the number of minutes is represented as an `i32`,
/// allowing a range of +/- ~4,086 years.
pub type TimestampAsMinutes = limited::LimitedResolutionTimestamp<limited::Minutes, BonsaiEpoch>;

/// A timestamp stored as the number of seconds (with no partial subseconds)
/// relative to [`BonsaiEpoch`]. Internally, the number of seconds is represented
/// as an `i64`, allowing a range of +/- ~21 times the age of the universe.
pub type TimestampAsSeconds = limited::LimitedResolutionTimestamp<limited::Seconds, BonsaiEpoch>;

/// A timestamp stored as the number of milliseconds (1/1,000th of a second)
/// relative to [`BonsaiEpoch`]. Internally, the number of milliseconds is
/// represented as an `i64`, allowing a range of +/- ~292.5 million years.
pub type TimestampAsMilliseconds =
    limited::LimitedResolutionTimestamp<limited::Milliseconds, BonsaiEpoch>;

/// A timestamp stored as the number of microseconds (1/1,000,000th of a second)
/// relative to [`BonsaiEpoch`]. Internally, the number of microseconds is
/// represented as an `i64`, allowing a range of +/- ~292,471 years.
pub type TimestampAsMicroseconds =
    limited::LimitedResolutionTimestamp<limited::Microseconds, BonsaiEpoch>;

/// A timestamp stored as the number of nanoseconds (1/1,000,000,000th of a
/// second) relative to [`BonsaiEpoch`]. Internally, the number of microseconds is
/// represented as an `i64`, allowing a range of +/- ~292.5 years.
pub type TimestampAsNanoseconds =
    limited::LimitedResolutionTimestamp<limited::Nanoseconds, BonsaiEpoch>;