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    // This is a part of Chrono.
    // Portions copyright (c) 2015, John Nagle.
    // See README.md and LICENSE.txt for details.

    //! Date and time parsing routines.

    #![allow(deprecated)]

    use core::borrow::Borrow;
    use core::str;
    use core::usize;

    use super::scan;
    use super::{Fixed, InternalFixed, InternalInternal, Item, Numeric, Pad, Parsed};
    use super::{ParseError, ParseErrorKind, ParseResult};
    use super::{BAD_FORMAT, INVALID, NOT_ENOUGH, OUT_OF_RANGE, TOO_LONG, TOO_SHORT};
    use {DateTime, FixedOffset, Weekday};

    fn set_weekday_with_num_days_from_sunday(p: &mut Parsed, v: i64) -> ParseResult<()> {
        p.set_weekday(match v {
            0 => Weekday::Sun,
            1 => Weekday::Mon,
            2 => Weekday::Tue,
            3 => Weekday::Wed,
            4 => Weekday::Thu,
            5 => Weekday::Fri,
            6 => Weekday::Sat,
            _ => return Err(OUT_OF_RANGE),
        })
    }

    fn set_weekday_with_number_from_monday(p: &mut Parsed, v: i64) -> ParseResult<()> {
        p.set_weekday(match v {
            1 => Weekday::Mon,
            2 => Weekday::Tue,
            3 => Weekday::Wed,
            4 => Weekday::Thu,
            5 => Weekday::Fri,
            6 => Weekday::Sat,
            7 => Weekday::Sun,
            _ => return Err(OUT_OF_RANGE),
        })
    }

    fn parse_rfc2822<'a>(parsed: &mut Parsed, mut s: &'a str) -> ParseResult<(&'a str, ())> {
        macro_rules! try_consume {
            ($e:expr) => {{
                let (s_, v) = $e?;
                s = s_;
                v
            }};
        }

        // an adapted RFC 2822 syntax from Section 3.3 and 4.3:
        //
        // date-time   = [ day-of-week "," ] date 1*S time *S
        // day-of-week = *S day-name *S
        // day-name    = "Mon" / "Tue" / "Wed" / "Thu" / "Fri" / "Sat" / "Sun"
        // date        = day month year
        // day         = *S 1*2DIGIT *S
        // month       = 1*S month-name 1*S
        // month-name  = "Jan" / "Feb" / "Mar" / "Apr" / "May" / "Jun" /
        //               "Jul" / "Aug" / "Sep" / "Oct" / "Nov" / "Dec"
        // year        = *S 2*DIGIT *S
        // time        = time-of-day 1*S zone
        // time-of-day = hour ":" minute [ ":" second ]
        // hour        = *S 2DIGIT *S
        // minute      = *S 2DIGIT *S
        // second      = *S 2DIGIT *S
        // zone        = ( "+" / "-" ) 4DIGIT /
        //               "UT" / "GMT" /                  ; same as +0000
        //               "EST" / "CST" / "MST" / "PST" / ; same as -0500 to -0800
        //               "EDT" / "CDT" / "MDT" / "PDT" / ; same as -0400 to -0700
        //               1*(%d65-90 / %d97-122)          ; same as -0000
        //
        // some notes:
        //
        // - quoted characters can be in any mixture of lower and upper cases.
        //
        // - we do not recognize a folding white space (FWS) or comment (CFWS).
        //   for our purposes, instead, we accept any sequence of Unicode
        //   white space characters (denoted here to `S`). any actual RFC 2822
        //   parser is expected to parse FWS and/or CFWS themselves and replace
        //   it with a single SP (`%x20`); this is legitimate.
        //
        // - two-digit year < 50 should be interpreted by adding 2000.
        //   two-digit year >= 50 or three-digit year should be interpreted
        //   by adding 1900. note that four-or-more-digit years less than 1000
        //   are *never* affected by this rule.
        //
        // - mismatching day-of-week is always an error, which is consistent to
        //   Chrono's own rules.
        //
        // - zones can range from `-9959` to `+9959`, but `FixedOffset` does not
        //   support offsets larger than 24 hours. this is not *that* problematic
        //   since we do not directly go to a `DateTime` so one can recover
        //   the offset information from `Parsed` anyway.

        s = s.trim_left();

        if let Ok((s_, weekday)) = scan::short_weekday(s) {
            if !s_.starts_with(',') {
                return Err(INVALID);
            }
            s = &s_[1..];
            parsed.set_weekday(weekday)?;
        }

        s = s.trim_left();
        parsed.set_day(try_consume!(scan::number(s, 1, 2)))?;
        s = scan::space(s)?; // mandatory
        parsed.set_month(1 + i64::from(try_consume!(scan::short_month0(s))))?;
        s = scan::space(s)?; // mandatory

        // distinguish two- and three-digit years from four-digit years
        let prevlen = s.len();
        let mut year = try_consume!(scan::number(s, 2, usize::MAX));
        let yearlen = prevlen - s.len();
        match (yearlen, year) {
            (2, 0...49) => {
                year += 2000;
            } //   47 -> 2047,   05 -> 2005
            (2, 50...99) => {
                year += 1900;
            } //   79 -> 1979
            (3, _) => {
                year += 1900;
            } //  112 -> 2012,  009 -> 1909
            (_, _) => {} // 1987 -> 1987, 0654 -> 0654
        }
        parsed.set_year(year)?;

        s = scan::space(s)?; // mandatory
        parsed.set_hour(try_consume!(scan::number(s, 2, 2)))?;
        s = scan::char(s.trim_left(), b':')?.trim_left(); // *S ":" *S
        parsed.set_minute(try_consume!(scan::number(s, 2, 2)))?;
        if let Ok(s_) = scan::char(s.trim_left(), b':') {
            // [ ":" *S 2DIGIT ]
            parsed.set_second(try_consume!(scan::number(s_, 2, 2)))?;
        }

        s = scan::space(s)?; // mandatory
        if let Some(offset) = try_consume!(scan::timezone_offset_2822(s)) {
            // only set the offset when it is definitely known (i.e. not `-0000`)
            parsed.set_offset(i64::from(offset))?;
        }

        Ok((s, ()))
    }

    fn parse_rfc3339<'a>(parsed: &mut Parsed, mut s: &'a str) -> ParseResult<(&'a str, ())> {
        macro_rules! try_consume {
            ($e:expr) => {{
                let (s_, v) = $e?;
                s = s_;
                v
            }};
        }

        // an adapted RFC 3339 syntax from Section 5.6:
        //
        // date-fullyear  = 4DIGIT
        // date-month     = 2DIGIT ; 01-12
        // date-mday      = 2DIGIT ; 01-28, 01-29, 01-30, 01-31 based on month/year
        // time-hour      = 2DIGIT ; 00-23
        // time-minute    = 2DIGIT ; 00-59
        // time-second    = 2DIGIT ; 00-58, 00-59, 00-60 based on leap second rules
        // time-secfrac   = "." 1*DIGIT
        // time-numoffset = ("+" / "-") time-hour ":" time-minute
        // time-offset    = "Z" / time-numoffset
        // partial-time   = time-hour ":" time-minute ":" time-second [time-secfrac]
        // full-date      = date-fullyear "-" date-month "-" date-mday
        // full-time      = partial-time time-offset
        // date-time      = full-date "T" full-time
        //
        // some notes:
        //
        // - quoted characters can be in any mixture of lower and upper cases.
        //
        // - it may accept any number of fractional digits for seconds.
        //   for Chrono, this means that we should skip digits past first 9 digits.
        //
        // - unlike RFC 2822, the valid offset ranges from -23:59 to +23:59.
        //   note that this restriction is unique to RFC 3339 and not ISO 8601.
        //   since this is not a typical Chrono behavior, we check it earlier.

        parsed.set_year(try_consume!(scan::number(s, 4, 4)))?;
        s = scan::char(s, b'-')?;
        parsed.set_month(try_consume!(scan::number(s, 2, 2)))?;
        s = scan::char(s, b'-')?;
        parsed.set_day(try_consume!(scan::number(s, 2, 2)))?;

        s = match s.as_bytes().first() {
            Some(&b't') | Some(&b'T') => &s[1..],
            Some(_) => return Err(INVALID),
            None => return Err(TOO_SHORT),
        };

        parsed.set_hour(try_consume!(scan::number(s, 2, 2)))?;
        s = scan::char(s, b':')?;
        parsed.set_minute(try_consume!(scan::number(s, 2, 2)))?;
        s = scan::char(s, b':')?;
        parsed.set_second(try_consume!(scan::number(s, 2, 2)))?;
        if s.starts_with('.') {
            let nanosecond = try_consume!(scan::nanosecond(&s[1..]));
            parsed.set_nanosecond(nanosecond)?;
        }

        let offset = try_consume!(scan::timezone_offset_zulu(s, |s| scan::char(s, b':')));
        if offset <= -86_400 || offset >= 86_400 {
            return Err(OUT_OF_RANGE);
        }
        parsed.set_offset(i64::from(offset))?;

        Ok((s, ()))
    }

    /// Tries to parse given string into `parsed` with given formatting items.
    /// Returns `Ok` when the entire string has been parsed (otherwise `parsed` should not be used).
    /// There should be no trailing string after parsing;
    /// use a stray [`Item::Space`](./enum.Item.html#variant.Space) to trim whitespaces.
    ///
    /// This particular date and time parser is:
    ///
    /// - Greedy. It will consume the longest possible prefix.
    ///   For example, `April` is always consumed entirely when the long month name is requested;
    ///   it equally accepts `Apr`, but prefers the longer prefix in this case.
    ///
    /// - Padding-agnostic (for numeric items).
    ///   The [`Pad`](./enum.Pad.html) field is completely ignored,
    ///   so one can prepend any number of whitespace then any number of zeroes before numbers.
    ///
    /// - (Still) obeying the intrinsic parsing width. This allows, for example, parsing `HHMMSS`.
    pub fn parse<'a, I, B>(parsed: &mut Parsed, s: &str, items: I) -> ParseResult<()>
    where
        I: Iterator<Item = B>,
        B: Borrow<Item<'a>>,
    {
        parse_internal(parsed, s, items).map(|_| ()).map_err(|(_s, e)| e)
    }

    fn parse_internal<'a, 'b, I, B>(
        parsed: &mut Parsed,
        mut s: &'b str,
        items: I,
    ) -> Result<&'b str, (&'b str, ParseError)>
    where
        I: Iterator<Item = B>,
        B: Borrow<Item<'a>>,
    {
        macro_rules! try_consume {
            ($e:expr) => {{
                match $e {
                    Ok((s_, v)) => {
                        s = s_;
                        v
                    }
                    Err(e) => return Err((s, e)),
                }
            }};
        }

        for item in items {
            match *item.borrow() {
                Item::Literal(prefix) => {
                    if s.len() < prefix.len() {
                        return Err((s, TOO_SHORT));
                    }
                    if !s.starts_with(prefix) {
                        return Err((s, INVALID));
                    }
                    s = &s[prefix.len()..];
                }

                #[cfg(any(feature = "alloc", feature = "std", test))]
                Item::OwnedLiteral(ref prefix) => {
                    if s.len() < prefix.len() {
                        return Err((s, TOO_SHORT));
                    }
                    if !s.starts_with(&prefix[..]) {
                        return Err((s, INVALID));
                    }
                    s = &s[prefix.len()..];
                }

                Item::Space(_) => {
                    s = s.trim_left();
                }

                #[cfg(any(feature = "alloc", feature = "std", test))]
                Item::OwnedSpace(_) => {
                    s = s.trim_left();
                }

                Item::Numeric(ref spec, ref _pad) => {
                    use super::Numeric::*;
                    type Setter = fn(&mut Parsed, i64) -> ParseResult<()>;

                    let (width, signed, set): (usize, bool, Setter) = match *spec {
                        Year => (4, true, Parsed::set_year),
                        YearDiv100 => (2, false, Parsed::set_year_div_100),
                        YearMod100 => (2, false, Parsed::set_year_mod_100),
                        IsoYear => (4, true, Parsed::set_isoyear),
                        IsoYearDiv100 => (2, false, Parsed::set_isoyear_div_100),
                        IsoYearMod100 => (2, false, Parsed::set_isoyear_mod_100),
                        Month => (2, false, Parsed::set_month),
                        Day => (2, false, Parsed::set_day),
                        WeekFromSun => (2, false, Parsed::set_week_from_sun),
                        WeekFromMon => (2, false, Parsed::set_week_from_mon),
                        IsoWeek => (2, false, Parsed::set_isoweek),
                        NumDaysFromSun => (1, false, set_weekday_with_num_days_from_sunday),
                        WeekdayFromMon => (1, false, set_weekday_with_number_from_monday),
                        Ordinal => (3, false, Parsed::set_ordinal),
                        Hour => (2, false, Parsed::set_hour),
                        Hour12 => (2, false, Parsed::set_hour12),
                        Minute => (2, false, Parsed::set_minute),
                        Second => (2, false, Parsed::set_second),
                        Nanosecond => (9, false, Parsed::set_nanosecond),
                        Timestamp => (usize::MAX, false, Parsed::set_timestamp),

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

                    s = s.trim_left();
                    let v = if signed {
                        if s.starts_with('-') {
                            let v = try_consume!(scan::number(&s[1..], 1, usize::MAX));
                            0i64.checked_sub(v).ok_or((s, OUT_OF_RANGE))?
                        } else if s.starts_with('+') {
                            try_consume!(scan::number(&s[1..], 1, usize::MAX))
                        } else {
                            // if there is no explicit sign, we respect the original `width`
                            try_consume!(scan::number(s, 1, width))
                        }
                    } else {
                        try_consume!(scan::number(s, 1, width))
                    };
                    set(parsed, v).map_err(|e| (s, e))?;
                }

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

                    match spec {
                        &ShortMonthName => {
                            let month0 = try_consume!(scan::short_month0(s));
                            parsed.set_month(i64::from(month0) + 1).map_err(|e| (s, e))?;
                        }

                        &LongMonthName => {
                            let month0 = try_consume!(scan::short_or_long_month0(s));
                            parsed.set_month(i64::from(month0) + 1).map_err(|e| (s, e))?;
                        }

                        &ShortWeekdayName => {
                            let weekday = try_consume!(scan::short_weekday(s));
                            parsed.set_weekday(weekday).map_err(|e| (s, e))?;
                        }

                        &LongWeekdayName => {
                            let weekday = try_consume!(scan::short_or_long_weekday(s));
                            parsed.set_weekday(weekday).map_err(|e| (s, e))?;
                        }

                        &LowerAmPm | &UpperAmPm => {
                            if s.len() < 2 {
                                return Err((s, TOO_SHORT));
                            }
                            let ampm = match (s.as_bytes()[0] | 32, s.as_bytes()[1] | 32) {
                                (b'a', b'm') => false,
                                (b'p', b'm') => true,
                                _ => return Err((s, INVALID)),
                            };
                            parsed.set_ampm(ampm).map_err(|e| (s, e))?;
                            s = &s[2..];
                        }

                        &Nanosecond | &Nanosecond3 | &Nanosecond6 | &Nanosecond9 => {
                            if s.starts_with('.') {
                                let nano = try_consume!(scan::nanosecond(&s[1..]));
                                parsed.set_nanosecond(nano).map_err(|e| (s, e))?;
                            }
                        }

                        &Internal(InternalFixed { val: InternalInternal::Nanosecond3NoDot }) => {
                            if s.len() < 3 {
                                return Err((s, TOO_SHORT));
                            }
                            let nano = try_consume!(scan::nanosecond_fixed(s, 3));
                            parsed.set_nanosecond(nano).map_err(|e| (s, e))?;
                        }

                        &Internal(InternalFixed { val: InternalInternal::Nanosecond6NoDot }) => {
                            if s.len() < 6 {
                                return Err((s, TOO_SHORT));
                            }
                            let nano = try_consume!(scan::nanosecond_fixed(s, 6));
                            parsed.set_nanosecond(nano).map_err(|e| (s, e))?;
                        }

                        &Internal(InternalFixed { val: InternalInternal::Nanosecond9NoDot }) => {
                            if s.len() < 9 {
                                return Err((s, TOO_SHORT));
                            }
                            let nano = try_consume!(scan::nanosecond_fixed(s, 9));
                            parsed.set_nanosecond(nano).map_err(|e| (s, e))?;
                        }

                        &TimezoneName => {
                            try_consume!(scan::timezone_name_skip(s));
                        }

                        &TimezoneOffsetColon | &TimezoneOffset => {
                            let offset = try_consume!(scan::timezone_offset(
                                s.trim_left(),
                                scan::colon_or_space
                            ));
                            parsed.set_offset(i64::from(offset)).map_err(|e| (s, e))?;
                        }

                        &TimezoneOffsetColonZ | &TimezoneOffsetZ => {
                            let offset = try_consume!(scan::timezone_offset_zulu(
                                s.trim_left(),
                                scan::colon_or_space
                            ));
                            parsed.set_offset(i64::from(offset)).map_err(|e| (s, e))?;
                        }
                        &Internal(InternalFixed {
                            val: InternalInternal::TimezoneOffsetPermissive,
                        }) => {
                            let offset = try_consume!(scan::timezone_offset_permissive(
                                s.trim_left(),
                                scan::colon_or_space
                            ));
                            parsed.set_offset(i64::from(offset)).map_err(|e| (s, e))?;
                        }

                        &RFC2822 => try_consume!(parse_rfc2822(parsed, s)),
                        &RFC3339 => try_consume!(parse_rfc3339(parsed, s)),
                    }
                }

                Item::Error => {
                    return Err((s, BAD_FORMAT));
                }
            }
        }

        // if there are trailling chars, it is an error
        if !s.is_empty() {
            Err((s, TOO_LONG))
        } else {
            Ok(s)
        }
    }

    impl str::FromStr for DateTime<FixedOffset> {
        type Err = ParseError;

        fn from_str(s: &str) -> ParseResult<DateTime<FixedOffset>> {
            const DATE_ITEMS: &'static [Item<'static>] = &[
                Item::Numeric(Numeric::Year, Pad::Zero),
                Item::Space(""),
                Item::Literal("-"),
                Item::Numeric(Numeric::Month, Pad::Zero),
                Item::Space(""),
                Item::Literal("-"),
                Item::Numeric(Numeric::Day, Pad::Zero),
            ];
            const TIME_ITEMS: &'static [Item<'static>] = &[
                Item::Numeric(Numeric::Hour, Pad::Zero),
                Item::Space(""),
                Item::Literal(":"),
                Item::Numeric(Numeric::Minute, Pad::Zero),
                Item::Space(""),
                Item::Literal(":"),
                Item::Numeric(Numeric::Second, Pad::Zero),
                Item::Fixed(Fixed::Nanosecond),
                Item::Space(""),
                Item::Fixed(Fixed::TimezoneOffsetZ),
                Item::Space(""),
            ];

            let mut parsed = Parsed::new();
            match parse_internal(&mut parsed, s, DATE_ITEMS.iter()) {
                Err((remainder, e)) if e.0 == ParseErrorKind::TooLong => {
                    if remainder.starts_with('T') || remainder.starts_with(' ') {
                        parse(&mut parsed, &remainder[1..], TIME_ITEMS.iter())?;
                    } else {
                        Err(INVALID)?;
                    }
                }
                Err((_s, e)) => Err(e)?,
                Ok(_) => Err(NOT_ENOUGH)?,
            };
            parsed.to_datetime()
        }
    }

    #[cfg(test)]
    #[test]
    fn test_parse() {
        use super::IMPOSSIBLE;
        use super::*;

        // workaround for Rust issue #22255
        fn parse_all(s: &str, items: &[Item]) -> ParseResult<Parsed> {
            let mut parsed = Parsed::new();
            parse(&mut parsed, s, items.iter())?;
            Ok(parsed)
        }

        macro_rules! check {
            ($fmt:expr, $items:expr; $err:tt) => (
                assert_eq!(parse_all($fmt, &$items), Err($err))
            );
            ($fmt:expr, $items:expr; $($k:ident: $v:expr),*) => (#[allow(unused_mut)] {
                let mut expected = Parsed::new();
                $(expected.$k = Some($v);)*
                assert_eq!(parse_all($fmt, &$items), Ok(expected))
            });
        }

        // empty string
        check!("",  []; );
        check!(" ", []; TOO_LONG);
        check!("a", []; TOO_LONG);

        // whitespaces
        check!("",          [sp!("")]; );
        check!(" ",         [sp!("")]; );
        check!("\t",        [sp!("")]; );
        check!(" \n\r  \n", [sp!("")]; );
        check!("a",         [sp!("")]; TOO_LONG);

        // literal
        check!("",    [lit!("a")]; TOO_SHORT);
        check!(" ",   [lit!("a")]; INVALID);
        check!("a",   [lit!("a")]; );
        check!("aa",  [lit!("a")]; TOO_LONG);
        check!("A",   [lit!("a")]; INVALID);
        check!("xy",  [lit!("xy")]; );
        check!("xy",  [lit!("x"), lit!("y")]; );
        check!("x y", [lit!("x"), lit!("y")]; INVALID);
        check!("xy",  [lit!("x"), sp!(""), lit!("y")]; );
        check!("x y", [lit!("x"), sp!(""), lit!("y")]; );

        // numeric
        check!("1987",        [num!(Year)]; year: 1987);
        check!("1987 ",       [num!(Year)]; TOO_LONG);
        check!("0x12",        [num!(Year)]; TOO_LONG); // `0` is parsed
        check!("x123",        [num!(Year)]; INVALID);
        check!("2015",        [num!(Year)]; year: 2015);
        check!("0000",        [num!(Year)]; year:    0);
        check!("9999",        [num!(Year)]; year: 9999);
        check!(" \t987",      [num!(Year)]; year:  987);
        check!("5",           [num!(Year)]; year:    5);
        check!("5\0",         [num!(Year)]; TOO_LONG);
        check!("\05",         [num!(Year)]; INVALID);
        check!("",            [num!(Year)]; TOO_SHORT);
        check!("12345",       [num!(Year), lit!("5")]; year: 1234);
        check!("12345",       [nums!(Year), lit!("5")]; year: 1234);
        check!("12345",       [num0!(Year), lit!("5")]; year: 1234);
        check!("12341234",    [num!(Year), num!(Year)]; year: 1234);
        check!("1234 1234",   [num!(Year), num!(Year)]; year: 1234);
        check!("1234 1235",   [num!(Year), num!(Year)]; IMPOSSIBLE);
        check!("1234 1234",   [num!(Year), lit!("x"), num!(Year)]; INVALID);
        check!("1234x1234",   [num!(Year), lit!("x"), num!(Year)]; year: 1234);
        check!("1234xx1234",  [num!(Year), lit!("x"), num!(Year)]; INVALID);
        check!("1234 x 1234", [num!(Year), lit!("x"), num!(Year)]; INVALID);

        // signed numeric
        check!("-42",         [num!(Year)]; year: -42);
        check!("+42",         [num!(Year)]; year: 42);
        check!("-0042",       [num!(Year)]; year: -42);
        check!("+0042",       [num!(Year)]; year: 42);
        check!("-42195",      [num!(Year)]; year: -42195);
        check!("+42195",      [num!(Year)]; year: 42195);
        check!("  -42195",    [num!(Year)]; year: -42195);
        check!("  +42195",    [num!(Year)]; year: 42195);
        check!("  -   42",    [num!(Year)]; INVALID);
        check!("  +   42",    [num!(Year)]; INVALID);
        check!("-",           [num!(Year)]; TOO_SHORT);
        check!("+",           [num!(Year)]; TOO_SHORT);

        // unsigned numeric
        check!("345",   [num!(Ordinal)]; ordinal: 345);
        check!("+345",  [num!(Ordinal)]; INVALID);
        check!("-345",  [num!(Ordinal)]; INVALID);
        check!(" 345",  [num!(Ordinal)]; ordinal: 345);
        check!(" +345", [num!(Ordinal)]; INVALID);
        check!(" -345", [num!(Ordinal)]; INVALID);

        // various numeric fields
        check!("1234 5678",
               [num!(Year), num!(IsoYear)];
               year: 1234, isoyear: 5678);
        check!("12 34 56 78",
               [num!(YearDiv100), num!(YearMod100), num!(IsoYearDiv100), num!(IsoYearMod100)];
               year_div_100: 12, year_mod_100: 34, isoyear_div_100: 56, isoyear_mod_100: 78);
        check!("1 2 3 4 5 6",
               [num!(Month), num!(Day), num!(WeekFromSun), num!(WeekFromMon), num!(IsoWeek),
                num!(NumDaysFromSun)];
               month: 1, day: 2, week_from_sun: 3, week_from_mon: 4, isoweek: 5, weekday: Weekday::Sat);
        check!("7 89 01",
               [num!(WeekdayFromMon), num!(Ordinal), num!(Hour12)];
               weekday: Weekday::Sun, ordinal: 89, hour_mod_12: 1);
        check!("23 45 6 78901234 567890123",
               [num!(Hour), num!(Minute), num!(Second), num!(Nanosecond), num!(Timestamp)];
               hour_div_12: 1, hour_mod_12: 11, minute: 45, second: 6, nanosecond: 78_901_234,
               timestamp: 567_890_123);

        // fixed: month and weekday names
        check!("apr",       [fix!(ShortMonthName)]; month: 4);
        check!("Apr",       [fix!(ShortMonthName)]; month: 4);
        check!("APR",       [fix!(ShortMonthName)]; month: 4);
        check!("ApR",       [fix!(ShortMonthName)]; month: 4);
        check!("April",     [fix!(ShortMonthName)]; TOO_LONG); // `Apr` is parsed
        check!("A",         [fix!(ShortMonthName)]; TOO_SHORT);
        check!("Sol",       [fix!(ShortMonthName)]; INVALID);
        check!("Apr",       [fix!(LongMonthName)]; month: 4);
        check!("Apri",      [fix!(LongMonthName)]; TOO_LONG); // `Apr` is parsed
        check!("April",     [fix!(LongMonthName)]; month: 4);
        check!("Aprill",    [fix!(LongMonthName)]; TOO_LONG);
        check!("Aprill",    [fix!(LongMonthName), lit!("l")]; month: 4);
        check!("Aprl",      [fix!(LongMonthName), lit!("l")]; month: 4);
        check!("April",     [fix!(LongMonthName), lit!("il")]; TOO_SHORT); // do not backtrack
        check!("thu",       [fix!(ShortWeekdayName)]; weekday: Weekday::Thu);
        check!("Thu",       [fix!(ShortWeekdayName)]; weekday: Weekday::Thu);
        check!("THU",       [fix!(ShortWeekdayName)]; weekday: Weekday::Thu);
        check!("tHu",       [fix!(ShortWeekdayName)]; weekday: Weekday::Thu);
        check!("Thursday",  [fix!(ShortWeekdayName)]; TOO_LONG); // `Thu` is parsed
        check!("T",         [fix!(ShortWeekdayName)]; TOO_SHORT);
        check!("The",       [fix!(ShortWeekdayName)]; INVALID);
        check!("Nop",       [fix!(ShortWeekdayName)]; INVALID);
        check!("Thu",       [fix!(LongWeekdayName)]; weekday: Weekday::Thu);
        check!("Thur",      [fix!(LongWeekdayName)]; TOO_LONG); // `Thu` is parsed
        check!("Thurs",     [fix!(LongWeekdayName)]; TOO_LONG); // ditto
        check!("Thursday",  [fix!(LongWeekdayName)]; weekday: Weekday::Thu);
        check!("Thursdays", [fix!(LongWeekdayName)]; TOO_LONG);
        check!("Thursdays", [fix!(LongWeekdayName), lit!("s")]; weekday: Weekday::Thu);
        check!("Thus",      [fix!(LongWeekdayName), lit!("s")]; weekday: Weekday::Thu);
        check!("Thursday",  [fix!(LongWeekdayName), lit!("rsday")]; TOO_SHORT); // do not backtrack

        // fixed: am/pm
        check!("am",  [fix!(LowerAmPm)]; hour_div_12: 0);
        check!("pm",  [fix!(LowerAmPm)]; hour_div_12: 1);
        check!("AM",  [fix!(LowerAmPm)]; hour_div_12: 0);
        check!("PM",  [fix!(LowerAmPm)]; hour_div_12: 1);
        check!("am",  [fix!(UpperAmPm)]; hour_div_12: 0);
        check!("pm",  [fix!(UpperAmPm)]; hour_div_12: 1);
        check!("AM",  [fix!(UpperAmPm)]; hour_div_12: 0);
        check!("PM",  [fix!(UpperAmPm)]; hour_div_12: 1);
        check!("Am",  [fix!(LowerAmPm)]; hour_div_12: 0);
        check!(" Am", [fix!(LowerAmPm)]; INVALID);
        check!("ame", [fix!(LowerAmPm)]; TOO_LONG); // `am` is parsed
        check!("a",   [fix!(LowerAmPm)]; TOO_SHORT);
        check!("p",   [fix!(LowerAmPm)]; TOO_SHORT);
        check!("x",   [fix!(LowerAmPm)]; TOO_SHORT);
        check!("xx",  [fix!(LowerAmPm)]; INVALID);
        check!("",    [fix!(LowerAmPm)]; TOO_SHORT);

        // fixed: dot plus nanoseconds
        check!("",              [fix!(Nanosecond)]; ); // no field set, but not an error
        check!("4",             [fix!(Nanosecond)]; TOO_LONG); // never consumes `4`
        check!("4",             [fix!(Nanosecond), num!(Second)]; second: 4);
        check!(".0",            [fix!(Nanosecond)]; nanosecond: 0);
        check!(".4",            [fix!(Nanosecond)]; nanosecond: 400_000_000);
        check!(".42",           [fix!(Nanosecond)]; nanosecond: 420_000_000);
        check!(".421",          [fix!(Nanosecond)]; nanosecond: 421_000_000);
        check!(".42195",        [fix!(Nanosecond)]; nanosecond: 421_950_000);
        check!(".421950803",    [fix!(Nanosecond)]; nanosecond: 421_950_803);
        check!(".421950803547", [fix!(Nanosecond)]; nanosecond: 421_950_803);
        check!(".000000003547", [fix!(Nanosecond)]; nanosecond: 3);
        check!(".000000000547", [fix!(Nanosecond)]; nanosecond: 0);
        check!(".",             [fix!(Nanosecond)]; TOO_SHORT);
        check!(".4x",           [fix!(Nanosecond)]; TOO_LONG);
        check!(".  4",          [fix!(Nanosecond)]; INVALID);
        check!("  .4",          [fix!(Nanosecond)]; TOO_LONG); // no automatic trimming

        // fixed: nanoseconds without the dot
        check!("",             [internal_fix!(Nanosecond3NoDot)]; TOO_SHORT);
        check!("0",            [internal_fix!(Nanosecond3NoDot)]; TOO_SHORT);
        check!("4",            [internal_fix!(Nanosecond3NoDot)]; TOO_SHORT);
        check!("42",           [internal_fix!(Nanosecond3NoDot)]; TOO_SHORT);
        check!("421",          [internal_fix!(Nanosecond3NoDot)]; nanosecond: 421_000_000);
        check!("42143",        [internal_fix!(Nanosecond3NoDot), num!(Second)]; nanosecond: 421_000_000, second: 43);
        check!("42195",        [internal_fix!(Nanosecond3NoDot)]; TOO_LONG);
        check!("4x",           [internal_fix!(Nanosecond3NoDot)]; TOO_SHORT);
        check!("  4",          [internal_fix!(Nanosecond3NoDot)]; INVALID);
        check!(".421",         [internal_fix!(Nanosecond3NoDot)]; INVALID);

        check!("",             [internal_fix!(Nanosecond6NoDot)]; TOO_SHORT);
        check!("0",            [internal_fix!(Nanosecond6NoDot)]; TOO_SHORT);
        check!("42195",        [internal_fix!(Nanosecond6NoDot)]; TOO_SHORT);
        check!("421950",       [internal_fix!(Nanosecond6NoDot)]; nanosecond: 421_950_000);
        check!("000003",       [internal_fix!(Nanosecond6NoDot)]; nanosecond: 3000);
        check!("000000",       [internal_fix!(Nanosecond6NoDot)]; nanosecond: 0);
        check!("4x",           [internal_fix!(Nanosecond6NoDot)]; TOO_SHORT);
        check!("     4",       [internal_fix!(Nanosecond6NoDot)]; INVALID);
        check!(".42100",       [internal_fix!(Nanosecond6NoDot)]; INVALID);

        check!("",             [internal_fix!(Nanosecond9NoDot)]; TOO_SHORT);
        check!("42195",        [internal_fix!(Nanosecond9NoDot)]; TOO_SHORT);
        check!("421950803",    [internal_fix!(Nanosecond9NoDot)]; nanosecond: 421_950_803);
        check!("000000003",    [internal_fix!(Nanosecond9NoDot)]; nanosecond: 3);
        check!("42195080354",  [internal_fix!(Nanosecond9NoDot), num!(Second)]; nanosecond: 421_950_803, second: 54); // don't skip digits that come after the 9
        check!("421950803547", [internal_fix!(Nanosecond9NoDot)]; TOO_LONG);
        check!("000000000",    [internal_fix!(Nanosecond9NoDot)]; nanosecond: 0);
        check!("00000000x",    [internal_fix!(Nanosecond9NoDot)]; INVALID);
        check!("        4",    [internal_fix!(Nanosecond9NoDot)]; INVALID);
        check!(".42100000",    [internal_fix!(Nanosecond9NoDot)]; INVALID);

        // fixed: timezone offsets
        check!("+00:00",    [fix!(TimezoneOffset)]; offset: 0);
        check!("-00:00",    [fix!(TimezoneOffset)]; offset: 0);
        check!("+00:01",    [fix!(TimezoneOffset)]; offset: 60);
        check!("-00:01",    [fix!(TimezoneOffset)]; offset: -60);
        check!("+00:30",    [fix!(TimezoneOffset)]; offset: 30 * 60);
        check!("-00:30",    [fix!(TimezoneOffset)]; offset: -30 * 60);
        check!("+04:56",    [fix!(TimezoneOffset)]; offset: 296 * 60);
        check!("-04:56",    [fix!(TimezoneOffset)]; offset: -296 * 60);
        check!("+24:00",    [fix!(TimezoneOffset)]; offset: 24 * 60 * 60);
        check!("-24:00",    [fix!(TimezoneOffset)]; offset: -24 * 60 * 60);
        check!("+99:59",    [fix!(TimezoneOffset)]; offset: (100 * 60 - 1) * 60);
        check!("-99:59",    [fix!(TimezoneOffset)]; offset: -(100 * 60 - 1) * 60);
        check!("+00:59",    [fix!(TimezoneOffset)]; offset: 59 * 60);
        check!("+00:60",    [fix!(TimezoneOffset)]; OUT_OF_RANGE);
        check!("+00:99",    [fix!(TimezoneOffset)]; OUT_OF_RANGE);
        check!("#12:34",    [fix!(TimezoneOffset)]; INVALID);
        check!("12:34",     [fix!(TimezoneOffset)]; INVALID);
        check!("+12:34 ",   [fix!(TimezoneOffset)]; TOO_LONG);
        check!(" +12:34",   [fix!(TimezoneOffset)]; offset: 754 * 60);
        check!("\t -12:34", [fix!(TimezoneOffset)]; offset: -754 * 60);
        check!("",          [fix!(TimezoneOffset)]; TOO_SHORT);
        check!("+",         [fix!(TimezoneOffset)]; TOO_SHORT);
        check!("+1",        [fix!(TimezoneOffset)]; TOO_SHORT);
        check!("+12",       [fix!(TimezoneOffset)]; TOO_SHORT);
        check!("+123",      [fix!(TimezoneOffset)]; TOO_SHORT);
        check!("+1234",     [fix!(TimezoneOffset)]; offset: 754 * 60);
        check!("+12345",    [fix!(TimezoneOffset)]; TOO_LONG);
        check!("+12345",    [fix!(TimezoneOffset), num!(Day)]; offset: 754 * 60, day: 5);
        check!("Z",         [fix!(TimezoneOffset)]; INVALID);
        check!("z",         [fix!(TimezoneOffset)]; INVALID);
        check!("Z",         [fix!(TimezoneOffsetZ)]; offset: 0);
        check!("z",         [fix!(TimezoneOffsetZ)]; offset: 0);
        check!("Y",         [fix!(TimezoneOffsetZ)]; INVALID);
        check!("Zulu",      [fix!(TimezoneOffsetZ), lit!("ulu")]; offset: 0);
        check!("zulu",      [fix!(TimezoneOffsetZ), lit!("ulu")]; offset: 0);
        check!("+1234ulu",  [fix!(TimezoneOffsetZ), lit!("ulu")]; offset: 754 * 60);
        check!("+12:34ulu", [fix!(TimezoneOffsetZ), lit!("ulu")]; offset: 754 * 60);
        check!("Z",         [internal_fix!(TimezoneOffsetPermissive)]; offset: 0);
        check!("z",         [internal_fix!(TimezoneOffsetPermissive)]; offset: 0);
        check!("+12:00",    [internal_fix!(TimezoneOffsetPermissive)]; offset: 12 * 60 * 60);
        check!("+12",       [internal_fix!(TimezoneOffsetPermissive)]; offset: 12 * 60 * 60);
        check!("CEST 5",    [fix!(TimezoneName), lit!(" "), num!(Day)]; day: 5);

        // some practical examples
        check!("2015-02-04T14:37:05+09:00",
               [num!(Year), lit!("-"), num!(Month), lit!("-"), num!(Day), lit!("T"),
                num!(Hour), lit!(":"), num!(Minute), lit!(":"), num!(Second), fix!(TimezoneOffset)];
               year: 2015, month: 2, day: 4, hour_div_12: 1, hour_mod_12: 2,
               minute: 37, second: 5, offset: 32400);
        check!("20150204143705567",
                [num!(Year), num!(Month), num!(Day),
                num!(Hour), num!(Minute), num!(Second), internal_fix!(Nanosecond3NoDot)];
                year: 2015, month: 2, day: 4, hour_div_12: 1, hour_mod_12: 2,
                minute: 37, second: 5, nanosecond: 567000000);
        check!("Mon, 10 Jun 2013 09:32:37 GMT",
               [fix!(ShortWeekdayName), lit!(","), sp!(" "), num!(Day), sp!(" "),
                fix!(ShortMonthName), sp!(" "), num!(Year), sp!(" "), num!(Hour), lit!(":"),
                num!(Minute), lit!(":"), num!(Second), sp!(" "), lit!("GMT")];
               year: 2013, month: 6, day: 10, weekday: Weekday::Mon,
               hour_div_12: 0, hour_mod_12: 9, minute: 32, second: 37);
        check!("Sun Aug 02 13:39:15 CEST 2020",
                [fix!(ShortWeekdayName), sp!(" "), fix!(ShortMonthName), sp!(" "),
                num!(Day), sp!(" "), num!(Hour), lit!(":"), num!(Minute), lit!(":"),
                num!(Second), sp!(" "), fix!(TimezoneName), sp!(" "), num!(Year)];
                year: 2020, month: 8, day: 2, weekday: Weekday::Sun,
                hour_div_12: 1, hour_mod_12: 1, minute: 39, second: 15);
        check!("20060102150405",
               [num!(Year), num!(Month), num!(Day), num!(Hour), num!(Minute), num!(Second)];
               year: 2006, month: 1, day: 2, hour_div_12: 1, hour_mod_12: 3, minute: 4, second: 5);
        check!("3:14PM",
               [num!(Hour12), lit!(":"), num!(Minute), fix!(LowerAmPm)];
               hour_div_12: 1, hour_mod_12: 3, minute: 14);
        check!("12345678901234.56789",
               [num!(Timestamp), lit!("."), num!(Nanosecond)];
               nanosecond: 56_789, timestamp: 12_345_678_901_234);
        check!("12345678901234.56789",
               [num!(Timestamp), fix!(Nanosecond)];
               nanosecond: 567_890_000, timestamp: 12_345_678_901_234);
    }

    #[cfg(test)]
    #[test]
    fn test_rfc2822() {
        use super::NOT_ENOUGH;
        use super::*;
        use offset::FixedOffset;
        use DateTime;

        // Test data - (input, Ok(expected result after parse and format) or Err(error code))
        let testdates = [
            ("Tue, 20 Jan 2015 17:35:20 -0800", Ok("Tue, 20 Jan 2015 17:35:20 -0800")), // normal case
            ("Fri,  2 Jan 2015 17:35:20 -0800", Ok("Fri, 02 Jan 2015 17:35:20 -0800")), // folding whitespace
            ("Fri, 02 Jan 2015 17:35:20 -0800", Ok("Fri, 02 Jan 2015 17:35:20 -0800")), // leading zero
            ("20 Jan 2015 17:35:20 -0800", Ok("Tue, 20 Jan 2015 17:35:20 -0800")), // no day of week
            ("20 JAN 2015 17:35:20 -0800", Ok("Tue, 20 Jan 2015 17:35:20 -0800")), // upper case month
            ("Tue, 20 Jan 2015 17:35 -0800", Ok("Tue, 20 Jan 2015 17:35:00 -0800")), // no second
            ("11 Sep 2001 09:45:00 EST", Ok("Tue, 11 Sep 2001 09:45:00 -0500")),
            ("30 Feb 2015 17:35:20 -0800", Err(OUT_OF_RANGE)), // bad day of month
            ("Tue, 20 Jan 2015", Err(TOO_SHORT)),              // omitted fields
            ("Tue, 20 Avr 2015 17:35:20 -0800", Err(INVALID)), // bad month name
            ("Tue, 20 Jan 2015 25:35:20 -0800", Err(OUT_OF_RANGE)), // bad hour
            ("Tue, 20 Jan 2015 7:35:20 -0800", Err(INVALID)),  // bad # of digits in hour
            ("Tue, 20 Jan 2015 17:65:20 -0800", Err(OUT_OF_RANGE)), // bad minute
            ("Tue, 20 Jan 2015 17:35:90 -0800", Err(OUT_OF_RANGE)), // bad second
            ("Tue, 20 Jan 2015 17:35:20 -0890", Err(OUT_OF_RANGE)), // bad offset
            ("6 Jun 1944 04:00:00Z", Err(INVALID)),            // bad offset (zulu not allowed)
            ("Tue, 20 Jan 2015 17:35:20 HAS", Err(NOT_ENOUGH)), // bad named time zone
        ];

        fn rfc2822_to_datetime(date: &str) -> ParseResult<DateTime<FixedOffset>> {
            let mut parsed = Parsed::new();
            parse(&mut parsed, date, [Item::Fixed(Fixed::RFC2822)].iter())?;
            parsed.to_datetime()
        }

        fn fmt_rfc2822_datetime(dt: DateTime<FixedOffset>) -> String {
            dt.format_with_items([Item::Fixed(Fixed::RFC2822)].iter()).to_string()
        }

        // Test against test data above
        for &(date, checkdate) in testdates.iter() {
            let d = rfc2822_to_datetime(date); // parse a date
            let dt = match d {
                // did we get a value?
                Ok(dt) => Ok(fmt_rfc2822_datetime(dt)), // yes, go on
                Err(e) => Err(e),                       // otherwise keep an error for the comparison
            };
            if dt != checkdate.map(|s| s.to_string()) {
                // check for expected result
                panic!(
                    "Date conversion failed for {}\nReceived: {:?}\nExpected: {:?}",
                    date, dt, checkdate
                );
            }
        }
    }

    #[cfg(test)]
    #[test]
    fn parse_rfc850() {
        use {TimeZone, Utc};

        static RFC850_FMT: &'static str = "%A, %d-%b-%y %T GMT";

        let dt_str = "Sunday, 06-Nov-94 08:49:37 GMT";
        let dt = Utc.ymd(1994, 11, 6).and_hms(8, 49, 37);

        // Check that the format is what we expect
        assert_eq!(dt.format(RFC850_FMT).to_string(), dt_str);

        // Check that it parses correctly
        assert_eq!(Ok(dt), Utc.datetime_from_str("Sunday, 06-Nov-94 08:49:37 GMT", RFC850_FMT));

        // Check that the rest of the weekdays parse correctly (this test originally failed because
        // Sunday parsed incorrectly).
        let testdates = [
            (Utc.ymd(1994, 11, 7).and_hms(8, 49, 37), "Monday, 07-Nov-94 08:49:37 GMT"),
            (Utc.ymd(1994, 11, 8).and_hms(8, 49, 37), "Tuesday, 08-Nov-94 08:49:37 GMT"),
            (Utc.ymd(1994, 11, 9).and_hms(8, 49, 37), "Wednesday, 09-Nov-94 08:49:37 GMT"),
            (Utc.ymd(1994, 11, 10).and_hms(8, 49, 37), "Thursday, 10-Nov-94 08:49:37 GMT"),
            (Utc.ymd(1994, 11, 11).and_hms(8, 49, 37), "Friday, 11-Nov-94 08:49:37 GMT"),
            (Utc.ymd(1994, 11, 12).and_hms(8, 49, 37), "Saturday, 12-Nov-94 08:49:37 GMT"),
        ];

        for val in &testdates {
            assert_eq!(Ok(val.0), Utc.datetime_from_str(val.1, RFC850_FMT));
        }
    }

    #[cfg(test)]
    #[test]
    fn test_rfc3339() {
        use super::*;
        use offset::FixedOffset;
        use DateTime;

        // Test data - (input, Ok(expected result after parse and format) or Err(error code))
        let testdates = [
            ("2015-01-20T17:35:20-08:00", Ok("2015-01-20T17:35:20-08:00")), // normal case
            ("1944-06-06T04:04:00Z", Ok("1944-06-06T04:04:00+00:00")),      // D-day
            ("2001-09-11T09:45:00-08:00", Ok("2001-09-11T09:45:00-08:00")),
            ("2015-01-20T17:35:20.001-08:00", Ok("2015-01-20T17:35:20.001-08:00")),
            ("2015-01-20T17:35:20.000031-08:00", Ok("2015-01-20T17:35:20.000031-08:00")),
            ("2015-01-20T17:35:20.000000004-08:00", Ok("2015-01-20T17:35:20.000000004-08:00")),
            ("2015-01-20T17:35:20.000000000452-08:00", Ok("2015-01-20T17:35:20-08:00")), // too small
            ("2015-02-30T17:35:20-08:00", Err(OUT_OF_RANGE)), // bad day of month
            ("2015-01-20T25:35:20-08:00", Err(OUT_OF_RANGE)), // bad hour
            ("2015-01-20T17:65:20-08:00", Err(OUT_OF_RANGE)), // bad minute
            ("2015-01-20T17:35:90-08:00", Err(OUT_OF_RANGE)), // bad second
            ("2015-01-20T17:35:20-24:00", Err(OUT_OF_RANGE)), // bad offset
        ];

        fn rfc3339_to_datetime(date: &str) -> ParseResult<DateTime<FixedOffset>> {
            let mut parsed = Parsed::new();
            parse(&mut parsed, date, [Item::Fixed(Fixed::RFC3339)].iter())?;
            parsed.to_datetime()
        }

        fn fmt_rfc3339_datetime(dt: DateTime<FixedOffset>) -> String {
            dt.format_with_items([Item::Fixed(Fixed::RFC3339)].iter()).to_string()
        }

        // Test against test data above
        for &(date, checkdate) in testdates.iter() {
            let d = rfc3339_to_datetime(date); // parse a date
            let dt = match d {
                // did we get a value?
                Ok(dt) => Ok(fmt_rfc3339_datetime(dt)), // yes, go on
                Err(e) => Err(e),                       // otherwise keep an error for the comparison
            };
            if dt != checkdate.map(|s| s.to_string()) {
                // check for expected result
                panic!(
                    "Date conversion failed for {}\nReceived: {:?}\nExpected: {:?}",
                    date, dt, checkdate
                );
            }
        }
    }