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    531

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

    //! The time zone, which calculates offsets from the local time to UTC.
    //!
    //! There are four operations provided by the `TimeZone` trait:
    //!
    //! 1. Converting the local `NaiveDateTime` to `DateTime<Tz>`
    //! 2. Converting the UTC `NaiveDateTime` to `DateTime<Tz>`
    //! 3. Converting `DateTime<Tz>` to the local `NaiveDateTime`
    //! 4. Constructing `DateTime<Tz>` objects from various offsets
    //!
    //! 1 is used for constructors. 2 is used for the `with_timezone` method of date and time types.
    //! 3 is used for other methods, e.g. `year()` or `format()`, and provided by an associated type
    //! which implements `Offset` (which then passed to `TimeZone` for actual implementations).
    //! Technically speaking `TimeZone` has a total knowledge about given timescale,
    //! but `Offset` is used as a cache to avoid the repeated conversion
    //! and provides implementations for 1 and 3.
    //! An `TimeZone` instance can be reconstructed from the corresponding `Offset` instance.

    use core::fmt;

    use format::{parse, ParseResult, Parsed, StrftimeItems};
    use naive::{NaiveDate, NaiveDateTime, NaiveTime};
    use Weekday;
    use {Date, DateTime};

    /// The conversion result from the local time to the timezone-aware datetime types.
    #[derive(Clone, PartialEq, Debug, Copy, Eq, Hash)]
    pub enum LocalResult<T> {
        /// Given local time representation is invalid.
        /// This can occur when, for example, the positive timezone transition.
        None,
        /// Given local time representation has a single unique result.
        Single(T),
        /// Given local time representation has multiple results and thus ambiguous.
        /// This can occur when, for example, the negative timezone transition.
        Ambiguous(T /*min*/, T /*max*/),
    }

    impl<T> LocalResult<T> {
        /// Returns `Some` only when the conversion result is unique, or `None` otherwise.
        pub fn single(self) -> Option<T> {
            match self {
                LocalResult::Single(t) => Some(t),
                _ => None,
            }
        }

        /// Returns `Some` for the earliest possible conversion result, or `None` if none.
        pub fn earliest(self) -> Option<T> {
            match self {
                LocalResult::Single(t) | LocalResult::Ambiguous(t, _) => Some(t),
                _ => None,
            }
        }

        /// Returns `Some` for the latest possible conversion result, or `None` if none.
        pub fn latest(self) -> Option<T> {
            match self {
                LocalResult::Single(t) | LocalResult::Ambiguous(_, t) => Some(t),
                _ => None,
            }
        }

        /// Maps a `LocalResult<T>` into `LocalResult<U>` with given function.
        pub fn map<U, F: FnMut(T) -> U>(self, mut f: F) -> LocalResult<U> {
            match self {
                LocalResult::None => LocalResult::None,
                LocalResult::Single(v) => LocalResult::Single(f(v)),
                LocalResult::Ambiguous(min, max) => LocalResult::Ambiguous(f(min), f(max)),
            }
        }
    }

    impl<Tz: TimeZone> LocalResult<Date<Tz>> {
        /// Makes a new `DateTime` from the current date and given `NaiveTime`.
        /// The offset in the current date is preserved.
        ///
        /// Propagates any error. Ambiguous result would be discarded.
        #[inline]
        pub fn and_time(self, time: NaiveTime) -> LocalResult<DateTime<Tz>> {
            match self {
                LocalResult::Single(d) => {
                    d.and_time(time).map_or(LocalResult::None, LocalResult::Single)
                }
                _ => LocalResult::None,
            }
        }

        /// Makes a new `DateTime` from the current date, hour, minute and second.
        /// The offset in the current date is preserved.
        ///
        /// Propagates any error. Ambiguous result would be discarded.
        #[inline]
        pub fn and_hms_opt(self, hour: u32, min: u32, sec: u32) -> LocalResult<DateTime<Tz>> {
            match self {
                LocalResult::Single(d) => {
                    d.and_hms_opt(hour, min, sec).map_or(LocalResult::None, LocalResult::Single)
                }
                _ => LocalResult::None,
            }
        }

        /// Makes a new `DateTime` from the current date, hour, minute, second and millisecond.
        /// The millisecond part can exceed 1,000 in order to represent the leap second.
        /// The offset in the current date is preserved.
        ///
        /// Propagates any error. Ambiguous result would be discarded.
        #[inline]
        pub fn and_hms_milli_opt(
            self,
            hour: u32,
            min: u32,
            sec: u32,
            milli: u32,
        ) -> LocalResult<DateTime<Tz>> {
            match self {
                LocalResult::Single(d) => d
                    .and_hms_milli_opt(hour, min, sec, milli)
                    .map_or(LocalResult::None, LocalResult::Single),
                _ => LocalResult::None,
            }
        }

        /// Makes a new `DateTime` from the current date, hour, minute, second and microsecond.
        /// The microsecond part can exceed 1,000,000 in order to represent the leap second.
        /// The offset in the current date is preserved.
        ///
        /// Propagates any error. Ambiguous result would be discarded.
        #[inline]
        pub fn and_hms_micro_opt(
            self,
            hour: u32,
            min: u32,
            sec: u32,
            micro: u32,
        ) -> LocalResult<DateTime<Tz>> {
            match self {
                LocalResult::Single(d) => d
                    .and_hms_micro_opt(hour, min, sec, micro)
                    .map_or(LocalResult::None, LocalResult::Single),
                _ => LocalResult::None,
            }
        }

        /// Makes a new `DateTime` from the current date, hour, minute, second and nanosecond.
        /// The nanosecond part can exceed 1,000,000,000 in order to represent the leap second.
        /// The offset in the current date is preserved.
        ///
        /// Propagates any error. Ambiguous result would be discarded.
        #[inline]
        pub fn and_hms_nano_opt(
            self,
            hour: u32,
            min: u32,
            sec: u32,
            nano: u32,
        ) -> LocalResult<DateTime<Tz>> {
            match self {
                LocalResult::Single(d) => d
                    .and_hms_nano_opt(hour, min, sec, nano)
                    .map_or(LocalResult::None, LocalResult::Single),
                _ => LocalResult::None,
            }
        }
    }

    impl<T: fmt::Debug> LocalResult<T> {
        /// Returns the single unique conversion result, or panics accordingly.
        pub fn unwrap(self) -> T {
            match self {
                LocalResult::None => panic!("No such local time"),
                LocalResult::Single(t) => t,
                LocalResult::Ambiguous(t1, t2) => {
                    panic!("Ambiguous local time, ranging from {:?} to {:?}", t1, t2)
                }
            }
        }
    }

    /// The offset from the local time to UTC.
    pub trait Offset: Sized + Clone + fmt::Debug {
        /// Returns the fixed offset from UTC to the local time stored.
        fn fix(&self) -> FixedOffset;
    }

    /// The time zone.
    ///
    /// The methods here are the primarily constructors for [`Date`](../struct.Date.html) and
    /// [`DateTime`](../struct.DateTime.html) types.
    pub trait TimeZone: Sized + Clone {
        /// An associated offset type.
        /// This type is used to store the actual offset in date and time types.
        /// The original `TimeZone` value can be recovered via `TimeZone::from_offset`.
        type Offset: Offset;

        /// Makes a new `Date` from year, month, day and the current time zone.
        /// This assumes the proleptic Gregorian calendar, with the year 0 being 1 BCE.
        ///
        /// The time zone normally does not affect the date (unless it is between UTC-24 and UTC+24),
        /// but it will propagate to the `DateTime` values constructed via this date.
        ///
        /// Panics on the out-of-range date, invalid month and/or day.
        ///
        /// # Example
        ///
        /// ~~~~
        /// use chrono::{Utc, TimeZone};
        ///
        /// assert_eq!(Utc.ymd(2015, 5, 15).to_string(), "2015-05-15UTC");
        /// ~~~~
        fn ymd(&self, year: i32, month: u32, day: u32) -> Date<Self> {
            self.ymd_opt(year, month, day).unwrap()
        }

        /// Makes a new `Date` from year, month, day and the current time zone.
        /// This assumes the proleptic Gregorian calendar, with the year 0 being 1 BCE.
        ///
        /// The time zone normally does not affect the date (unless it is between UTC-24 and UTC+24),
        /// but it will propagate to the `DateTime` values constructed via this date.
        ///
        /// Returns `None` on the out-of-range date, invalid month and/or day.
        ///
        /// # Example
        ///
        /// ~~~~
        /// use chrono::{Utc, LocalResult, TimeZone};
        ///
        /// assert_eq!(Utc.ymd_opt(2015, 5, 15).unwrap().to_string(), "2015-05-15UTC");
        /// assert_eq!(Utc.ymd_opt(2000, 0, 0), LocalResult::None);
        /// ~~~~
        fn ymd_opt(&self, year: i32, month: u32, day: u32) -> LocalResult<Date<Self>> {
            match NaiveDate::from_ymd_opt(year, month, day) {
                Some(d) => self.from_local_date(&d),
                None => LocalResult::None,
            }
        }

        /// Makes a new `Date` from year, day of year (DOY or "ordinal") and the current time zone.
        /// This assumes the proleptic Gregorian calendar, with the year 0 being 1 BCE.
        ///
        /// The time zone normally does not affect the date (unless it is between UTC-24 and UTC+24),
        /// but it will propagate to the `DateTime` values constructed via this date.
        ///
        /// Panics on the out-of-range date and/or invalid DOY.
        ///
        /// # Example
        ///
        /// ~~~~
        /// use chrono::{Utc, TimeZone};
        ///
        /// assert_eq!(Utc.yo(2015, 135).to_string(), "2015-05-15UTC");
        /// ~~~~
        fn yo(&self, year: i32, ordinal: u32) -> Date<Self> {
            self.yo_opt(year, ordinal).unwrap()
        }

        /// Makes a new `Date` from year, day of year (DOY or "ordinal") and the current time zone.
        /// This assumes the proleptic Gregorian calendar, with the year 0 being 1 BCE.
        ///
        /// The time zone normally does not affect the date (unless it is between UTC-24 and UTC+24),
        /// but it will propagate to the `DateTime` values constructed via this date.
        ///
        /// Returns `None` on the out-of-range date and/or invalid DOY.
        fn yo_opt(&self, year: i32, ordinal: u32) -> LocalResult<Date<Self>> {
            match NaiveDate::from_yo_opt(year, ordinal) {
                Some(d) => self.from_local_date(&d),
                None => LocalResult::None,
            }
        }

        /// Makes a new `Date` from ISO week date (year and week number), day of the week (DOW) and
        /// the current time zone.
        /// This assumes the proleptic Gregorian calendar, with the year 0 being 1 BCE.
        /// The resulting `Date` may have a different year from the input year.
        ///
        /// The time zone normally does not affect the date (unless it is between UTC-24 and UTC+24),
        /// but it will propagate to the `DateTime` values constructed via this date.
        ///
        /// Panics on the out-of-range date and/or invalid week number.
        ///
        /// # Example
        ///
        /// ~~~~
        /// use chrono::{Utc, Weekday, TimeZone};
        ///
        /// assert_eq!(Utc.isoywd(2015, 20, Weekday::Fri).to_string(), "2015-05-15UTC");
        /// ~~~~
        fn isoywd(&self, year: i32, week: u32, weekday: Weekday) -> Date<Self> {
            self.isoywd_opt(year, week, weekday).unwrap()
        }

        /// Makes a new `Date` from ISO week date (year and week number), day of the week (DOW) and
        /// the current time zone.
        /// This assumes the proleptic Gregorian calendar, with the year 0 being 1 BCE.
        /// The resulting `Date` may have a different year from the input year.
        ///
        /// The time zone normally does not affect the date (unless it is between UTC-24 and UTC+24),
        /// but it will propagate to the `DateTime` values constructed via this date.
        ///
        /// Returns `None` on the out-of-range date and/or invalid week number.
        fn isoywd_opt(&self, year: i32, week: u32, weekday: Weekday) -> LocalResult<Date<Self>> {
            match NaiveDate::from_isoywd_opt(year, week, weekday) {
                Some(d) => self.from_local_date(&d),
                None => LocalResult::None,
            }
        }

        /// Makes a new `DateTime` from the number of non-leap seconds
        /// since January 1, 1970 0:00:00 UTC (aka "UNIX timestamp")
        /// and the number of nanoseconds since the last whole non-leap second.
        ///
        /// Panics on the out-of-range number of seconds and/or invalid nanosecond,
        /// for a non-panicking version see [`timestamp_opt`](#method.timestamp_opt).
        ///
        /// # Example
        ///
        /// ~~~~
        /// use chrono::{Utc, TimeZone};
        ///
        /// assert_eq!(Utc.timestamp(1431648000, 0).to_string(), "2015-05-15 00:00:00 UTC");
        /// ~~~~
        fn timestamp(&self, secs: i64, nsecs: u32) -> DateTime<Self> {
            self.timestamp_opt(secs, nsecs).unwrap()
        }

        /// Makes a new `DateTime` from the number of non-leap seconds
        /// since January 1, 1970 0:00:00 UTC (aka "UNIX timestamp")
        /// and the number of nanoseconds since the last whole non-leap second.
        ///
        /// Returns `LocalResult::None` on out-of-range number of seconds and/or
        /// invalid nanosecond, otherwise always returns `LocalResult::Single`.
        fn timestamp_opt(&self, secs: i64, nsecs: u32) -> LocalResult<DateTime<Self>> {
            match NaiveDateTime::from_timestamp_opt(secs, nsecs) {
                Some(dt) => LocalResult::Single(self.from_utc_datetime(&dt)),
                None => LocalResult::None,
            }
        }

        /// Makes a new `DateTime` from the number of non-leap milliseconds
        /// since January 1, 1970 0:00:00 UTC (aka "UNIX timestamp").
        ///
        /// Panics on out-of-range number of milliseconds for a non-panicking
        /// version see [`timestamp_millis_opt`](#method.timestamp_millis_opt).
        ///
        /// # Example
        ///
        /// ~~~~
        /// use chrono::{Utc, TimeZone};
        ///
        /// assert_eq!(Utc.timestamp_millis(1431648000).timestamp(), 1431648);
        /// ~~~~
        fn timestamp_millis(&self, millis: i64) -> DateTime<Self> {
            self.timestamp_millis_opt(millis).unwrap()
        }

        /// Makes a new `DateTime` from the number of non-leap milliseconds
        /// since January 1, 1970 0:00:00 UTC (aka "UNIX timestamp").
        ///
        ///
        /// Returns `LocalResult::None` on out-of-range number of milliseconds
        /// and/or invalid nanosecond, otherwise always returns
        /// `LocalResult::Single`.
        ///
        /// # Example
        ///
        /// ~~~~
        /// use chrono::{Utc, TimeZone, LocalResult};
        /// match Utc.timestamp_millis_opt(1431648000) {
        ///     LocalResult::Single(dt) => assert_eq!(dt.timestamp(), 1431648),
        ///     _ => panic!("Incorrect timestamp_millis"),
        /// };
        /// ~~~~
        fn timestamp_millis_opt(&self, millis: i64) -> LocalResult<DateTime<Self>> {
            let (mut secs, mut millis) = (millis / 1000, millis % 1000);
            if millis < 0 {
                secs -= 1;
                millis += 1000;
            }
            self.timestamp_opt(secs, millis as u32 * 1_000_000)
        }

        /// Makes a new `DateTime` from the number of non-leap nanoseconds
        /// since January 1, 1970 0:00:00 UTC (aka "UNIX timestamp").
        ///
        /// Unlike [`timestamp_millis`](#method.timestamp_millis), this never
        /// panics.
        ///
        /// # Example
        ///
        /// ~~~~
        /// use chrono::{Utc, TimeZone};
        ///
        /// assert_eq!(Utc.timestamp_nanos(1431648000000000).timestamp(), 1431648);
        /// ~~~~
        fn timestamp_nanos(&self, nanos: i64) -> DateTime<Self> {
            let (mut secs, mut nanos) = (nanos / 1_000_000_000, nanos % 1_000_000_000);
            if nanos < 0 {
                secs -= 1;
                nanos += 1_000_000_000;
            }
            self.timestamp_opt(secs, nanos as u32).unwrap()
        }

        /// Parses a string with the specified format string and
        /// returns a `DateTime` with the current offset.
        /// See the [`format::strftime` module](../format/strftime/index.html)
        /// on the supported escape sequences.
        ///
        /// If the format does not include offsets, the current offset is assumed;
        /// otherwise the input should have a matching UTC offset.
        ///
        /// See also `DateTime::parse_from_str` which gives a local `DateTime`
        /// with parsed `FixedOffset`.
        fn datetime_from_str(&self, s: &str, fmt: &str) -> ParseResult<DateTime<Self>> {
            let mut parsed = Parsed::new();
            parse(&mut parsed, s, StrftimeItems::new(fmt))?;
            parsed.to_datetime_with_timezone(self)
        }

        /// Reconstructs the time zone from the offset.
        fn from_offset(offset: &Self::Offset) -> Self;

        /// Creates the offset(s) for given local `NaiveDate` if possible.
        fn offset_from_local_date(&self, local: &NaiveDate) -> LocalResult<Self::Offset>;

        /// Creates the offset(s) for given local `NaiveDateTime` if possible.
        fn offset_from_local_datetime(&self, local: &NaiveDateTime) -> LocalResult<Self::Offset>;

        /// Converts the local `NaiveDate` to the timezone-aware `Date` if possible.
        fn from_local_date(&self, local: &NaiveDate) -> LocalResult<Date<Self>> {
            self.offset_from_local_date(local).map(|offset| {
                // since FixedOffset is within +/- 1 day, the date is never affected
                Date::from_utc(*local, offset)
            })
        }

        /// Converts the local `NaiveDateTime` to the timezone-aware `DateTime` if possible.
        fn from_local_datetime(&self, local: &NaiveDateTime) -> LocalResult<DateTime<Self>> {
            self.offset_from_local_datetime(local)
                .map(|offset| DateTime::from_utc(*local - offset.fix(), offset))
        }

        /// Creates the offset for given UTC `NaiveDate`. This cannot fail.
        fn offset_from_utc_date(&self, utc: &NaiveDate) -> Self::Offset;

        /// Creates the offset for given UTC `NaiveDateTime`. This cannot fail.
        fn offset_from_utc_datetime(&self, utc: &NaiveDateTime) -> Self::Offset;

        /// Converts the UTC `NaiveDate` to the local time.
        /// The UTC is continuous and thus this cannot fail (but can give the duplicate local time).
        fn from_utc_date(&self, utc: &NaiveDate) -> Date<Self> {
            Date::from_utc(*utc, self.offset_from_utc_date(utc))
        }

        /// Converts the UTC `NaiveDateTime` to the local time.
        /// The UTC is continuous and thus this cannot fail (but can give the duplicate local time).
        fn from_utc_datetime(&self, utc: &NaiveDateTime) -> DateTime<Self> {
            DateTime::from_utc(*utc, self.offset_from_utc_datetime(utc))
        }
    }

    mod fixed;
    #[cfg(feature = "clock")]
    mod local;
    mod utc;

    pub use self::fixed::FixedOffset;
    #[cfg(feature = "clock")]
    pub use self::local::Local;
    pub use self::utc::Utc;

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

        #[test]
        fn test_negative_millis() {
            let dt = Utc.timestamp_millis(-1000);
            assert_eq!(dt.to_string(), "1969-12-31 23:59:59 UTC");
            let dt = Utc.timestamp_millis(-7000);
            assert_eq!(dt.to_string(), "1969-12-31 23:59:53 UTC");
            let dt = Utc.timestamp_millis(-7001);
            assert_eq!(dt.to_string(), "1969-12-31 23:59:52.999 UTC");
            let dt = Utc.timestamp_millis(-7003);
            assert_eq!(dt.to_string(), "1969-12-31 23:59:52.997 UTC");
            let dt = Utc.timestamp_millis(-999);
            assert_eq!(dt.to_string(), "1969-12-31 23:59:59.001 UTC");
            let dt = Utc.timestamp_millis(-1);
            assert_eq!(dt.to_string(), "1969-12-31 23:59:59.999 UTC");
            let dt = Utc.timestamp_millis(-60000);
            assert_eq!(dt.to_string(), "1969-12-31 23:59:00 UTC");
            let dt = Utc.timestamp_millis(-3600000);
            assert_eq!(dt.to_string(), "1969-12-31 23:00:00 UTC");

            for (millis, expected) in &[
                (-7000, "1969-12-31 23:59:53 UTC"),
                (-7001, "1969-12-31 23:59:52.999 UTC"),
                (-7003, "1969-12-31 23:59:52.997 UTC"),
            ] {
                match Utc.timestamp_millis_opt(*millis) {
                    LocalResult::Single(dt) => {
                        assert_eq!(dt.to_string(), *expected);
                    }
                    e => panic!("Got {:?} instead of an okay answer", e),
                }
            }
        }

        #[test]
        fn test_negative_nanos() {
            let dt = Utc.timestamp_nanos(-1_000_000_000);
            assert_eq!(dt.to_string(), "1969-12-31 23:59:59 UTC");
            let dt = Utc.timestamp_nanos(-999_999_999);
            assert_eq!(dt.to_string(), "1969-12-31 23:59:59.000000001 UTC");
            let dt = Utc.timestamp_nanos(-1);
            assert_eq!(dt.to_string(), "1969-12-31 23:59:59.999999999 UTC");
            let dt = Utc.timestamp_nanos(-60_000_000_000);
            assert_eq!(dt.to_string(), "1969-12-31 23:59:00 UTC");
            let dt = Utc.timestamp_nanos(-3_600_000_000_000);
            assert_eq!(dt.to_string(), "1969-12-31 23:00:00 UTC");
        }

        #[test]
        fn test_nanos_never_panics() {
            Utc.timestamp_nanos(i64::max_value());
            Utc.timestamp_nanos(i64::default());
            Utc.timestamp_nanos(i64::min_value());
        }
    }