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
// This is a part of Chrono.
// See README.md and LICENSE.txt for details.

//! Formatting (and parsing) utilities for date and time.
//!
//! This module provides the common types and routines to implement,
//! for example, [`DateTime::format`](../struct.DateTime.html#method.format) or
//! [`DateTime::parse_from_str`](../struct.DateTime.html#method.parse_from_str) methods.
//! For most cases you should use these high-level interfaces.
//!
//! Internally the formatting and parsing shares the same abstract **formatting items**,
//! which are just an [`Iterator`](https://doc.rust-lang.org/std/iter/trait.Iterator.html) of
//! the [`Item`](./enum.Item.html) type.
//! They are generated from more readable **format strings**;
//! currently Chrono supports [one built-in syntax closely resembling
//! C's `strftime` format](./strftime/index.html).

#![allow(ellipsis_inclusive_range_patterns)]

#[cfg(feature = "alloc")]
use alloc::boxed::Box;
#[cfg(feature = "alloc")]
use alloc::string::{String, ToString};
#[cfg(any(feature = "alloc", feature = "std", test))]
use core::borrow::Borrow;
use core::fmt;
use core::str::FromStr;
#[cfg(any(feature = "std", test))]
use std::error::Error;

#[cfg(any(feature = "alloc", feature = "std", test))]
use naive::{NaiveDate, NaiveTime};
#[cfg(any(feature = "alloc", feature = "std", test))]
use offset::{FixedOffset, Offset};
#[cfg(any(feature = "alloc", feature = "std", test))]
use {Datelike, Timelike};
use {Month, ParseMonthError, ParseWeekdayError, Weekday};

#[cfg(feature = "unstable-locales")]
pub(crate) mod locales;

pub use self::parse::parse;
pub use self::parsed::Parsed;
pub use self::strftime::StrftimeItems;
/// L10n locales.
#[cfg(feature = "unstable-locales")]
pub use pure_rust_locales::Locale;

#[cfg(not(feature = "unstable-locales"))]
#[derive(Debug)]
struct Locale;

/// An uninhabited type used for `InternalNumeric` and `InternalFixed` below.
#[derive(Clone, PartialEq, Eq)]
enum Void {}

/// Padding characters for numeric items.
#[derive(Copy, Clone, PartialEq, Eq, Debug)]
pub enum Pad {
    /// No padding.
    None,
    /// Zero (`0`) padding.
    Zero,
    /// Space padding.
    Space,
}

/// Numeric item types.
/// They have associated formatting width (FW) and parsing width (PW).
///
/// The **formatting width** is the minimal width to be formatted.
/// If the number is too short, and the padding is not [`Pad::None`](./enum.Pad.html#variant.None),
/// then it is left-padded.
/// If the number is too long or (in some cases) negative, it is printed as is.
///
/// The **parsing width** is the maximal width to be scanned.
/// The parser only tries to consume from one to given number of digits (greedily).
/// It also trims the preceding whitespace if any.
/// It cannot parse the negative number, so some date and time cannot be formatted then
/// parsed with the same formatting items.
#[derive(Clone, PartialEq, Eq, Debug)]
pub enum Numeric {
    /// Full Gregorian year (FW=4, PW=∞).
    /// May accept years before 1 BCE or after 9999 CE, given an initial sign.
    Year,
    /// Gregorian year divided by 100 (century number; FW=PW=2). Implies the non-negative year.
    YearDiv100,
    /// Gregorian year modulo 100 (FW=PW=2). Cannot be negative.
    YearMod100,
    /// Year in the ISO week date (FW=4, PW=∞).
    /// May accept years before 1 BCE or after 9999 CE, given an initial sign.
    IsoYear,
    /// Year in the ISO week date, divided by 100 (FW=PW=2). Implies the non-negative year.
    IsoYearDiv100,
    /// Year in the ISO week date, modulo 100 (FW=PW=2). Cannot be negative.
    IsoYearMod100,
    /// Month (FW=PW=2).
    Month,
    /// Day of the month (FW=PW=2).
    Day,
    /// Week number, where the week 1 starts at the first Sunday of January (FW=PW=2).
    WeekFromSun,
    /// Week number, where the week 1 starts at the first Monday of January (FW=PW=2).
    WeekFromMon,
    /// Week number in the ISO week date (FW=PW=2).
    IsoWeek,
    /// Day of the week, where Sunday = 0 and Saturday = 6 (FW=PW=1).
    NumDaysFromSun,
    /// Day of the week, where Monday = 1 and Sunday = 7 (FW=PW=1).
    WeekdayFromMon,
    /// Day of the year (FW=PW=3).
    Ordinal,
    /// Hour number in the 24-hour clocks (FW=PW=2).
    Hour,
    /// Hour number in the 12-hour clocks (FW=PW=2).
    Hour12,
    /// The number of minutes since the last whole hour (FW=PW=2).
    Minute,
    /// The number of seconds since the last whole minute (FW=PW=2).
    Second,
    /// The number of nanoseconds since the last whole second (FW=PW=9).
    /// Note that this is *not* left-aligned;
    /// see also [`Fixed::Nanosecond`](./enum.Fixed.html#variant.Nanosecond).
    Nanosecond,
    /// The number of non-leap seconds since the midnight UTC on January 1, 1970 (FW=1, PW=∞).
    /// For formatting, it assumes UTC upon the absence of time zone offset.
    Timestamp,

    /// Internal uses only.
    ///
    /// This item exists so that one can add additional internal-only formatting
    /// without breaking major compatibility (as enum variants cannot be selectively private).
    Internal(InternalNumeric),
}

/// An opaque type representing numeric item types for internal uses only.
pub struct InternalNumeric {
    _dummy: Void,
}

impl Clone for InternalNumeric {
    fn clone(&self) -> Self {
        match self._dummy {}
    }
}

impl PartialEq for InternalNumeric {
    fn eq(&self, _other: &InternalNumeric) -> bool {
        match self._dummy {}
    }
}

impl Eq for InternalNumeric {}

impl fmt::Debug for InternalNumeric {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        write!(f, "<InternalNumeric>")
    }
}

/// Fixed-format item types.
///
/// They have their own rules of formatting and parsing.
/// Otherwise noted, they print in the specified cases but parse case-insensitively.
#[derive(Clone, PartialEq, Eq, Debug)]
pub enum Fixed {
    /// Abbreviated month names.
    ///
    /// Prints a three-letter-long name in the title case, reads the same name in any case.
    ShortMonthName,
    /// Full month names.
    ///
    /// Prints a full name in the title case, reads either a short or full name in any case.
    LongMonthName,
    /// Abbreviated day of the week names.
    ///
    /// Prints a three-letter-long name in the title case, reads the same name in any case.
    ShortWeekdayName,
    /// Full day of the week names.
    ///
    /// Prints a full name in the title case, reads either a short or full name in any case.
    LongWeekdayName,
    /// AM/PM.
    ///
    /// Prints in lower case, reads in any case.
    LowerAmPm,
    /// AM/PM.
    ///
    /// Prints in upper case, reads in any case.
    UpperAmPm,
    /// An optional dot plus one or more digits for left-aligned nanoseconds.
    /// May print nothing, 3, 6 or 9 digits according to the available accuracy.
    /// See also [`Numeric::Nanosecond`](./enum.Numeric.html#variant.Nanosecond).
    Nanosecond,
    /// Same as [`Nanosecond`](#variant.Nanosecond) but the accuracy is fixed to 3.
    Nanosecond3,
    /// Same as [`Nanosecond`](#variant.Nanosecond) but the accuracy is fixed to 6.
    Nanosecond6,
    /// Same as [`Nanosecond`](#variant.Nanosecond) but the accuracy is fixed to 9.
    Nanosecond9,
    /// Timezone name.
    ///
    /// It does not support parsing, its use in the parser is an immediate failure.
    TimezoneName,
    /// Offset from the local time to UTC (`+09:00` or `-04:00` or `+00:00`).
    ///
    /// In the parser, the colon can be omitted and/or surrounded with any amount of whitespace.
    /// The offset is limited from `-24:00` to `+24:00`,
    /// which is the same as [`FixedOffset`](../offset/struct.FixedOffset.html)'s range.
    TimezoneOffsetColon,
    /// Offset from the local time to UTC (`+09:00` or `-04:00` or `Z`).
    ///
    /// In the parser, the colon can be omitted and/or surrounded with any amount of whitespace,
    /// and `Z` can be either in upper case or in lower case.
    /// The offset is limited from `-24:00` to `+24:00`,
    /// which is the same as [`FixedOffset`](../offset/struct.FixedOffset.html)'s range.
    TimezoneOffsetColonZ,
    /// Same as [`TimezoneOffsetColon`](#variant.TimezoneOffsetColon) but prints no colon.
    /// Parsing allows an optional colon.
    TimezoneOffset,
    /// Same as [`TimezoneOffsetColonZ`](#variant.TimezoneOffsetColonZ) but prints no colon.
    /// Parsing allows an optional colon.
    TimezoneOffsetZ,
    /// RFC 2822 date and time syntax. Commonly used for email and MIME date and time.
    RFC2822,
    /// RFC 3339 & ISO 8601 date and time syntax.
    RFC3339,

    /// Internal uses only.
    ///
    /// This item exists so that one can add additional internal-only formatting
    /// without breaking major compatibility (as enum variants cannot be selectively private).
    Internal(InternalFixed),
}

/// An opaque type representing fixed-format item types for internal uses only.
#[derive(Debug, Clone, PartialEq, Eq)]
pub struct InternalFixed {
    val: InternalInternal,
}

#[derive(Debug, Clone, PartialEq, Eq)]
enum InternalInternal {
    /// Same as [`TimezoneOffsetColonZ`](#variant.TimezoneOffsetColonZ), but
    /// allows missing minutes (per [ISO 8601][iso8601]).
    ///
    /// # Panics
    ///
    /// If you try to use this for printing.
    ///
    /// [iso8601]: https://en.wikipedia.org/wiki/ISO_8601#Time_offsets_from_UTC
    TimezoneOffsetPermissive,
    /// Same as [`Nanosecond`](#variant.Nanosecond) but the accuracy is fixed to 3 and there is no leading dot.
    Nanosecond3NoDot,
    /// Same as [`Nanosecond`](#variant.Nanosecond) but the accuracy is fixed to 6 and there is no leading dot.
    Nanosecond6NoDot,
    /// Same as [`Nanosecond`](#variant.Nanosecond) but the accuracy is fixed to 9 and there is no leading dot.
    Nanosecond9NoDot,
}

/// A single formatting item. This is used for both formatting and parsing.
#[derive(Clone, PartialEq, Eq, Debug)]
pub enum Item<'a> {
    /// A literally printed and parsed text.
    Literal(&'a str),
    /// Same as `Literal` but with the string owned by the item.
    #[cfg(any(feature = "alloc", feature = "std", test))]
    OwnedLiteral(Box<str>),
    /// Whitespace. Prints literally but reads zero or more whitespace.
    Space(&'a str),
    /// Same as `Space` but with the string owned by the item.
    #[cfg(any(feature = "alloc", feature = "std", test))]
    OwnedSpace(Box<str>),
    /// Numeric item. Can be optionally padded to the maximal length (if any) when formatting;
    /// the parser simply ignores any padded whitespace and zeroes.
    Numeric(Numeric, Pad),
    /// Fixed-format item.
    Fixed(Fixed),
    /// Issues a formatting error. Used to signal an invalid format string.
    Error,
}

macro_rules! lit {
    ($x:expr) => {
        Item::Literal($x)
    };
}
macro_rules! sp {
    ($x:expr) => {
        Item::Space($x)
    };
}
macro_rules! num {
    ($x:ident) => {
        Item::Numeric(Numeric::$x, Pad::None)
    };
}
macro_rules! num0 {
    ($x:ident) => {
        Item::Numeric(Numeric::$x, Pad::Zero)
    };
}
macro_rules! nums {
    ($x:ident) => {
        Item::Numeric(Numeric::$x, Pad::Space)
    };
}
macro_rules! fix {
    ($x:ident) => {
        Item::Fixed(Fixed::$x)
    };
}
macro_rules! internal_fix {
    ($x:ident) => {
        Item::Fixed(Fixed::Internal(InternalFixed { val: InternalInternal::$x }))
    };
}

/// An error from the `parse` function.
#[derive(Debug, Clone, PartialEq, Eq, Copy)]
pub struct ParseError(ParseErrorKind);

/// The category of parse error
#[derive(Debug, Clone, PartialEq, Eq, Copy)]
enum ParseErrorKind {
    /// Given field is out of permitted range.
    OutOfRange,

    /// There is no possible date and time value with given set of fields.
    ///
    /// This does not include the out-of-range conditions, which are trivially invalid.
    /// It includes the case that there are one or more fields that are inconsistent to each other.
    Impossible,

    /// Given set of fields is not enough to make a requested date and time value.
    ///
    /// Note that there *may* be a case that given fields constrain the possible values so much
    /// that there is a unique possible value. Chrono only tries to be correct for
    /// most useful sets of fields however, as such constraint solving can be expensive.
    NotEnough,

    /// The input string has some invalid character sequence for given formatting items.
    Invalid,

    /// The input string has been prematurely ended.
    TooShort,

    /// All formatting items have been read but there is a remaining input.
    TooLong,

    /// There was an error on the formatting string, or there were non-supported formating items.
    BadFormat,
}

/// Same as `Result<T, ParseError>`.
pub type ParseResult<T> = Result<T, ParseError>;

impl fmt::Display for ParseError {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        match self.0 {
            ParseErrorKind::OutOfRange => write!(f, "input is out of range"),
            ParseErrorKind::Impossible => write!(f, "no possible date and time matching input"),
            ParseErrorKind::NotEnough => write!(f, "input is not enough for unique date and time"),
            ParseErrorKind::Invalid => write!(f, "input contains invalid characters"),
            ParseErrorKind::TooShort => write!(f, "premature end of input"),
            ParseErrorKind::TooLong => write!(f, "trailing input"),
            ParseErrorKind::BadFormat => write!(f, "bad or unsupported format string"),
        }
    }
}

#[cfg(any(feature = "std", test))]
impl Error for ParseError {
    #[allow(deprecated)]
    fn description(&self) -> &str {
        "parser error, see to_string() for details"
    }
}

// to be used in this module and submodules
const OUT_OF_RANGE: ParseError = ParseError(ParseErrorKind::OutOfRange);
const IMPOSSIBLE: ParseError = ParseError(ParseErrorKind::Impossible);
const NOT_ENOUGH: ParseError = ParseError(ParseErrorKind::NotEnough);
const INVALID: ParseError = ParseError(ParseErrorKind::Invalid);
const TOO_SHORT: ParseError = ParseError(ParseErrorKind::TooShort);
const TOO_LONG: ParseError = ParseError(ParseErrorKind::TooLong);
const BAD_FORMAT: ParseError = ParseError(ParseErrorKind::BadFormat);

/// Formats single formatting item
#[cfg(any(feature = "alloc", feature = "std", test))]
pub fn format_item<'a>(
    w: &mut fmt::Formatter,
    date: Option<&NaiveDate>,
    time: Option<&NaiveTime>,
    off: Option<&(String, FixedOffset)>,
    item: &Item<'a>,
) -> fmt::Result {
    let mut result = String::new();
    format_inner(&mut result, date, time, off, item, None)?;
    w.pad(&result)
}

#[cfg(any(feature = "alloc", feature = "std", test))]
fn format_inner<'a>(
    result: &mut String,
    date: Option<&NaiveDate>,
    time: Option<&NaiveTime>,
    off: Option<&(String, FixedOffset)>,
    item: &Item<'a>,
    _locale: Option<Locale>,
) -> fmt::Result {
    #[cfg(feature = "unstable-locales")]
    let (short_months, long_months, short_weekdays, long_weekdays, am_pm, am_pm_lowercase) = {
        let locale = _locale.unwrap_or(Locale::POSIX);
        let am_pm = locales::am_pm(locale);
        (
            locales::short_months(locale),
            locales::long_months(locale),
            locales::short_weekdays(locale),
            locales::long_weekdays(locale),
            am_pm,
            &[am_pm[0].to_lowercase(), am_pm[1].to_lowercase()],
        )
    };
    #[cfg(not(feature = "unstable-locales"))]
    let (short_months, long_months, short_weekdays, long_weekdays, am_pm, am_pm_lowercase) = {
        (
            &["Jan", "Feb", "Mar", "Apr", "May", "Jun", "Jul", "Aug", "Sep", "Oct", "Nov", "Dec"],
            &[
                "January",
                "February",
                "March",
                "April",
                "May",
                "June",
                "July",
                "August",
                "September",
                "October",
                "November",
                "December",
            ],
            &["Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat"],
            &["Sunday", "Monday", "Tuesday", "Wednesday", "Thursday", "Friday", "Saturday"],
            &["AM", "PM"],
            &["am", "pm"],
        )
    };

    use core::fmt::Write;
    use div::{div_floor, mod_floor};

    match *item {
        Item::Literal(s) | Item::Space(s) => result.push_str(s),
        #[cfg(any(feature = "alloc", feature = "std", test))]
        Item::OwnedLiteral(ref s) | Item::OwnedSpace(ref s) => result.push_str(s),

        Item::Numeric(ref spec, ref pad) => {
            use self::Numeric::*;

            let week_from_sun = |d: &NaiveDate| {
                (d.ordinal() as i32 - d.weekday().num_days_from_sunday() as i32 + 7) / 7
            };
            let week_from_mon = |d: &NaiveDate| {
                (d.ordinal() as i32 - d.weekday().num_days_from_monday() as i32 + 7) / 7
            };

            let (width, v) = match *spec {
                Year => (4, date.map(|d| i64::from(d.year()))),
                YearDiv100 => (2, date.map(|d| div_floor(i64::from(d.year()), 100))),
                YearMod100 => (2, date.map(|d| mod_floor(i64::from(d.year()), 100))),
                IsoYear => (4, date.map(|d| i64::from(d.iso_week().year()))),
                IsoYearDiv100 => (2, date.map(|d| div_floor(i64::from(d.iso_week().year()), 100))),
                IsoYearMod100 => (2, date.map(|d| mod_floor(i64::from(d.iso_week().year()), 100))),
                Month => (2, date.map(|d| i64::from(d.month()))),
                Day => (2, date.map(|d| i64::from(d.day()))),
                WeekFromSun => (2, date.map(|d| i64::from(week_from_sun(d)))),
                WeekFromMon => (2, date.map(|d| i64::from(week_from_mon(d)))),
                IsoWeek => (2, date.map(|d| i64::from(d.iso_week().week()))),
                NumDaysFromSun => (1, date.map(|d| i64::from(d.weekday().num_days_from_sunday()))),
                WeekdayFromMon => (1, date.map(|d| i64::from(d.weekday().number_from_monday()))),
                Ordinal => (3, date.map(|d| i64::from(d.ordinal()))),
                Hour => (2, time.map(|t| i64::from(t.hour()))),
                Hour12 => (2, time.map(|t| i64::from(t.hour12().1))),
                Minute => (2, time.map(|t| i64::from(t.minute()))),
                Second => (2, time.map(|t| i64::from(t.second() + t.nanosecond() / 1_000_000_000))),
                Nanosecond => (9, time.map(|t| i64::from(t.nanosecond() % 1_000_000_000))),
                Timestamp => (
                    1,
                    match (date, time, off) {
                        (Some(d), Some(t), None) => Some(d.and_time(*t).timestamp()),
                        (Some(d), Some(t), Some(&(_, off))) => {
                            Some((d.and_time(*t) - off).timestamp())
                        }
                        (_, _, _) => None,
                    },
                ),

                // for the future expansion
                Internal(ref int) => match int._dummy {},
            };

            if let Some(v) = v {
                if (spec == &Year || spec == &IsoYear) && !(0 <= v && v < 10_000) {
                    // non-four-digit years require an explicit sign as per ISO 8601
                    match *pad {
                        Pad::None => write!(result, "{:+}", v),
                        Pad::Zero => write!(result, "{:+01$}", v, width + 1),
                        Pad::Space => write!(result, "{:+1$}", v, width + 1),
                    }
                } else {
                    match *pad {
                        Pad::None => write!(result, "{}", v),
                        Pad::Zero => write!(result, "{:01$}", v, width),
                        Pad::Space => write!(result, "{:1$}", v, width),
                    }
                }?
            } else {
                return Err(fmt::Error); // insufficient arguments for given format
            }
        }

        Item::Fixed(ref spec) => {
            use self::Fixed::*;

            /// Prints an offset from UTC in the format of `+HHMM` or `+HH:MM`.
            /// `Z` instead of `+00[:]00` is allowed when `allow_zulu` is true.
            fn write_local_minus_utc(
                result: &mut String,
                off: FixedOffset,
                allow_zulu: bool,
                use_colon: bool,
            ) -> fmt::Result {
                let off = off.local_minus_utc();
                if !allow_zulu || off != 0 {
                    let (sign, off) = if off < 0 { ('-', -off) } else { ('+', off) };
                    if use_colon {
                        write!(result, "{}{:02}:{:02}", sign, off / 3600, off / 60 % 60)
                    } else {
                        write!(result, "{}{:02}{:02}", sign, off / 3600, off / 60 % 60)
                    }
                } else {
                    result.push_str("Z");
                    Ok(())
                }
            }

            let ret =
                match *spec {
                    ShortMonthName => date.map(|d| {
                        result.push_str(short_months[d.month0() as usize]);
                        Ok(())
                    }),
                    LongMonthName => date.map(|d| {
                        result.push_str(long_months[d.month0() as usize]);
                        Ok(())
                    }),
                    ShortWeekdayName => date.map(|d| {
                        result
                            .push_str(short_weekdays[d.weekday().num_days_from_sunday() as usize]);
                        Ok(())
                    }),
                    LongWeekdayName => date.map(|d| {
                        result.push_str(long_weekdays[d.weekday().num_days_from_sunday() as usize]);
                        Ok(())
                    }),
                    LowerAmPm => time.map(|t| {
                        #[cfg_attr(feature = "cargo-clippy", allow(useless_asref))]
                        {
                            result.push_str(if t.hour12().0 {
                                am_pm_lowercase[1].as_ref()
                            } else {
                                am_pm_lowercase[0].as_ref()
                            });
                        }
                        Ok(())
                    }),
                    UpperAmPm => time.map(|t| {
                        result.push_str(if t.hour12().0 { am_pm[1] } else { am_pm[0] });
                        Ok(())
                    }),
                    Nanosecond => time.map(|t| {
                        let nano = t.nanosecond() % 1_000_000_000;
                        if nano == 0 {
                            Ok(())
                        } else if nano % 1_000_000 == 0 {
                            write!(result, ".{:03}", nano / 1_000_000)
                        } else if nano % 1_000 == 0 {
                            write!(result, ".{:06}", nano / 1_000)
                        } else {
                            write!(result, ".{:09}", nano)
                        }
                    }),
                    Nanosecond3 => time.map(|t| {
                        let nano = t.nanosecond() % 1_000_000_000;
                        write!(result, ".{:03}", nano / 1_000_000)
                    }),
                    Nanosecond6 => time.map(|t| {
                        let nano = t.nanosecond() % 1_000_000_000;
                        write!(result, ".{:06}", nano / 1_000)
                    }),
                    Nanosecond9 => time.map(|t| {
                        let nano = t.nanosecond() % 1_000_000_000;
                        write!(result, ".{:09}", nano)
                    }),
                    Internal(InternalFixed { val: InternalInternal::Nanosecond3NoDot }) => time
                        .map(|t| {
                            let nano = t.nanosecond() % 1_000_000_000;
                            write!(result, "{:03}", nano / 1_000_000)
                        }),
                    Internal(InternalFixed { val: InternalInternal::Nanosecond6NoDot }) => time
                        .map(|t| {
                            let nano = t.nanosecond() % 1_000_000_000;
                            write!(result, "{:06}", nano / 1_000)
                        }),
                    Internal(InternalFixed { val: InternalInternal::Nanosecond9NoDot }) => time
                        .map(|t| {
                            let nano = t.nanosecond() % 1_000_000_000;
                            write!(result, "{:09}", nano)
                        }),
                    TimezoneName => off.map(|&(ref name, _)| {
                        result.push_str(name);
                        Ok(())
                    }),
                    TimezoneOffsetColon => {
                        off.map(|&(_, off)| write_local_minus_utc(result, off, false, true))
                    }
                    TimezoneOffsetColonZ => {
                        off.map(|&(_, off)| write_local_minus_utc(result, off, true, true))
                    }
                    TimezoneOffset => {
                        off.map(|&(_, off)| write_local_minus_utc(result, off, false, false))
                    }
                    TimezoneOffsetZ => {
                        off.map(|&(_, off)| write_local_minus_utc(result, off, true, false))
                    }
                    Internal(InternalFixed { val: InternalInternal::TimezoneOffsetPermissive }) => {
                        panic!("Do not try to write %#z it is undefined")
                    }
                    RFC2822 =>
                    // same as `%a, %d %b %Y %H:%M:%S %z`
                    {
                        if let (Some(d), Some(t), Some(&(_, off))) = (date, time, off) {
                            let sec = t.second() + t.nanosecond() / 1_000_000_000;
                            write!(
                                result,
                                "{}, {:02} {} {:04} {:02}:{:02}:{:02} ",
                                short_weekdays[d.weekday().num_days_from_sunday() as usize],
                                d.day(),
                                short_months[d.month0() as usize],
                                d.year(),
                                t.hour(),
                                t.minute(),
                                sec
                            )?;
                            Some(write_local_minus_utc(result, off, false, false))
                        } else {
                            None
                        }
                    }
                    RFC3339 =>
                    // same as `%Y-%m-%dT%H:%M:%S%.f%:z`
                    {
                        if let (Some(d), Some(t), Some(&(_, off))) = (date, time, off) {
                            // reuse `Debug` impls which already print ISO 8601 format.
                            // this is faster in this way.
                            write!(result, "{:?}T{:?}", d, t)?;
                            Some(write_local_minus_utc(result, off, false, true))
                        } else {
                            None
                        }
                    }
                };

            match ret {
                Some(ret) => ret?,
                None => return Err(fmt::Error), // insufficient arguments for given format
            }
        }

        Item::Error => return Err(fmt::Error),
    }
    Ok(())
}

/// Tries to format given arguments with given formatting items.
/// Internally used by `DelayedFormat`.
#[cfg(any(feature = "alloc", feature = "std", test))]
pub fn format<'a, I, B>(
    w: &mut fmt::Formatter,
    date: Option<&NaiveDate>,
    time: Option<&NaiveTime>,
    off: Option<&(String, FixedOffset)>,
    items: I,
) -> fmt::Result
where
    I: Iterator<Item = B> + Clone,
    B: Borrow<Item<'a>>,
{
    let mut result = String::new();
    for item in items {
        format_inner(&mut result, date, time, off, item.borrow(), None)?;
    }
    w.pad(&result)
}

mod parsed;

// due to the size of parsing routines, they are in separate modules.
mod parse;
mod scan;

pub mod strftime;

/// A *temporary* object which can be used as an argument to `format!` or others.
/// This is normally constructed via `format` methods of each date and time type.
#[cfg(any(feature = "alloc", feature = "std", test))]
#[derive(Debug)]
pub struct DelayedFormat<I> {
    /// The date view, if any.
    date: Option<NaiveDate>,
    /// The time view, if any.
    time: Option<NaiveTime>,
    /// The name and local-to-UTC difference for the offset (timezone), if any.
    off: Option<(String, FixedOffset)>,
    /// An iterator returning formatting items.
    items: I,
    /// Locale used for text.
    locale: Option<Locale>,
}

#[cfg(any(feature = "alloc", feature = "std", test))]
impl<'a, I: Iterator<Item = B> + Clone, B: Borrow<Item<'a>>> DelayedFormat<I> {
    /// Makes a new `DelayedFormat` value out of local date and time.
    pub fn new(date: Option<NaiveDate>, time: Option<NaiveTime>, items: I) -> DelayedFormat<I> {
        DelayedFormat { date: date, time: time, off: None, items: items, locale: None }
    }

    /// Makes a new `DelayedFormat` value out of local date and time and UTC offset.
    pub fn new_with_offset<Off>(
        date: Option<NaiveDate>,
        time: Option<NaiveTime>,
        offset: &Off,
        items: I,
    ) -> DelayedFormat<I>
    where
        Off: Offset + fmt::Display,
    {
        let name_and_diff = (offset.to_string(), offset.fix());
        DelayedFormat {
            date: date,
            time: time,
            off: Some(name_and_diff),
            items: items,
            locale: None,
        }
    }

    /// Makes a new `DelayedFormat` value out of local date and time and locale.
    #[cfg(feature = "unstable-locales")]
    pub fn new_with_locale(
        date: Option<NaiveDate>,
        time: Option<NaiveTime>,
        items: I,
        locale: Locale,
    ) -> DelayedFormat<I> {
        DelayedFormat { date: date, time: time, off: None, items: items, locale: Some(locale) }
    }

    /// Makes a new `DelayedFormat` value out of local date and time, UTC offset and locale.
    #[cfg(feature = "unstable-locales")]
    pub fn new_with_offset_and_locale<Off>(
        date: Option<NaiveDate>,
        time: Option<NaiveTime>,
        offset: &Off,
        items: I,
        locale: Locale,
    ) -> DelayedFormat<I>
    where
        Off: Offset + fmt::Display,
    {
        let name_and_diff = (offset.to_string(), offset.fix());
        DelayedFormat {
            date: date,
            time: time,
            off: Some(name_and_diff),
            items: items,
            locale: Some(locale),
        }
    }
}

#[cfg(any(feature = "alloc", feature = "std", test))]
impl<'a, I: Iterator<Item = B> + Clone, B: Borrow<Item<'a>>> fmt::Display for DelayedFormat<I> {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        #[cfg(feature = "unstable-locales")]
        {
            if let Some(locale) = self.locale {
                return format_localized(
                    f,
                    self.date.as_ref(),
                    self.time.as_ref(),
                    self.off.as_ref(),
                    self.items.clone(),
                    locale,
                );
            }
        }

        format(f, self.date.as_ref(), self.time.as_ref(), self.off.as_ref(), self.items.clone())
    }
}

// this implementation is here only because we need some private code from `scan`

/// Parsing a `str` into a `Weekday` uses the format [`%W`](./format/strftime/index.html).
///
/// # Example
///
/// ~~~~
/// use chrono::Weekday;
///
/// assert_eq!("Sunday".parse::<Weekday>(), Ok(Weekday::Sun));
/// assert!("any day".parse::<Weekday>().is_err());
/// ~~~~
///
/// The parsing is case-insensitive.
///
/// ~~~~
/// # use chrono::Weekday;
/// assert_eq!("mON".parse::<Weekday>(), Ok(Weekday::Mon));
/// ~~~~
///
/// Only the shortest form (e.g. `sun`) and the longest form (e.g. `sunday`) is accepted.
///
/// ~~~~
/// # use chrono::Weekday;
/// assert!("thurs".parse::<Weekday>().is_err());
/// ~~~~
impl FromStr for Weekday {
    type Err = ParseWeekdayError;

    fn from_str(s: &str) -> Result<Self, Self::Err> {
        if let Ok(("", w)) = scan::short_or_long_weekday(s) {
            Ok(w)
        } else {
            Err(ParseWeekdayError { _dummy: () })
        }
    }
}

/// Formats single formatting item
#[cfg(feature = "unstable-locales")]
pub fn format_item_localized<'a>(
    w: &mut fmt::Formatter,
    date: Option<&NaiveDate>,
    time: Option<&NaiveTime>,
    off: Option<&(String, FixedOffset)>,
    item: &Item<'a>,
    locale: Locale,
) -> fmt::Result {
    let mut result = String::new();
    format_inner(&mut result, date, time, off, item, Some(locale))?;
    w.pad(&result)
}

/// Tries to format given arguments with given formatting items.
/// Internally used by `DelayedFormat`.
#[cfg(feature = "unstable-locales")]
pub fn format_localized<'a, I, B>(
    w: &mut fmt::Formatter,
    date: Option<&NaiveDate>,
    time: Option<&NaiveTime>,
    off: Option<&(String, FixedOffset)>,
    items: I,
    locale: Locale,
) -> fmt::Result
where
    I: Iterator<Item = B> + Clone,
    B: Borrow<Item<'a>>,
{
    let mut result = String::new();
    for item in items {
        format_inner(&mut result, date, time, off, item.borrow(), Some(locale))?;
    }
    w.pad(&result)
}

/// Parsing a `str` into a `Month` uses the format [`%W`](./format/strftime/index.html).
///
/// # Example
///
/// ~~~~
/// use chrono::Month;
///
/// assert_eq!("January".parse::<Month>(), Ok(Month::January));
/// assert!("any day".parse::<Month>().is_err());
/// ~~~~
///
/// The parsing is case-insensitive.
///
/// ~~~~
/// # use chrono::Month;
/// assert_eq!("fEbruARy".parse::<Month>(), Ok(Month::February));
/// ~~~~
///
/// Only the shortest form (e.g. `jan`) and the longest form (e.g. `january`) is accepted.
///
/// ~~~~
/// # use chrono::Month;
/// assert!("septem".parse::<Month>().is_err());
/// assert!("Augustin".parse::<Month>().is_err());
/// ~~~~
impl FromStr for Month {
    type Err = ParseMonthError;

    fn from_str(s: &str) -> Result<Self, Self::Err> {
        if let Ok(("", w)) = scan::short_or_long_month0(s) {
            match w {
                0 => Ok(Month::January),
                1 => Ok(Month::February),
                2 => Ok(Month::March),
                3 => Ok(Month::April),
                4 => Ok(Month::May),
                5 => Ok(Month::June),
                6 => Ok(Month::July),
                7 => Ok(Month::August),
                8 => Ok(Month::September),
                9 => Ok(Month::October),
                10 => Ok(Month::November),
                11 => Ok(Month::December),
                _ => Err(ParseMonthError { _dummy: () }),
            }
        } else {
            Err(ParseMonthError { _dummy: () })
        }
    }
}