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

    //! The local (system) time zone.

    #[cfg(not(all(target_arch = "wasm32", not(target_os = "wasi"), feature = "wasmbind")))]
    use sys::{self, Timespec};

    use super::fixed::FixedOffset;
    use super::{LocalResult, TimeZone};
    #[cfg(not(all(target_arch = "wasm32", not(target_os = "wasi"), feature = "wasmbind")))]
    use naive::NaiveTime;
    use naive::{NaiveDate, NaiveDateTime};
    use {Date, DateTime};
    #[cfg(not(all(target_arch = "wasm32", not(target_os = "wasi"), feature = "wasmbind")))]
    use {Datelike, Timelike};

    /// Converts a `time::Tm` struct into the timezone-aware `DateTime`.
    /// This assumes that `time` is working correctly, i.e. any error is fatal.
    #[cfg(not(all(target_arch = "wasm32", not(target_os = "wasi"), feature = "wasmbind")))]
    fn tm_to_datetime(mut tm: sys::Tm) -> DateTime<Local> {
        if tm.tm_sec >= 60 {
            tm.tm_nsec += (tm.tm_sec - 59) * 1_000_000_000;
            tm.tm_sec = 59;
        }

        #[cfg(not(windows))]
        fn tm_to_naive_date(tm: &sys::Tm) -> NaiveDate {
            // from_yo is more efficient than from_ymd (since it's the internal representation).
            NaiveDate::from_yo(tm.tm_year + 1900, tm.tm_yday as u32 + 1)
        }

        #[cfg(windows)]
        fn tm_to_naive_date(tm: &sys::Tm) -> NaiveDate {
            // ...but tm_yday is broken in Windows (issue #85)
            NaiveDate::from_ymd(tm.tm_year + 1900, tm.tm_mon as u32 + 1, tm.tm_mday as u32)
        }

        let date = tm_to_naive_date(&tm);
        let time = NaiveTime::from_hms_nano(
            tm.tm_hour as u32,
            tm.tm_min as u32,
            tm.tm_sec as u32,
            tm.tm_nsec as u32,
        );
        let offset = FixedOffset::east(tm.tm_utcoff);
        DateTime::from_utc(date.and_time(time) - offset, offset)
    }

    /// Converts a local `NaiveDateTime` to the `time::Timespec`.
    #[cfg(not(all(target_arch = "wasm32", not(target_os = "wasi"), feature = "wasmbind")))]
    fn datetime_to_timespec(d: &NaiveDateTime, local: bool) -> sys::Timespec {
        // well, this exploits an undocumented `Tm::to_timespec` behavior
        // to get the exact function we want (either `timegm` or `mktime`).
        // the number 1 is arbitrary but should be non-zero to trigger `mktime`.
        let tm_utcoff = if local { 1 } else { 0 };

        let tm = sys::Tm {
            tm_sec: d.second() as i32,
            tm_min: d.minute() as i32,
            tm_hour: d.hour() as i32,
            tm_mday: d.day() as i32,
            tm_mon: d.month0() as i32, // yes, C is that strange...
            tm_year: d.year() - 1900,  // this doesn't underflow, we know that d is `NaiveDateTime`.
            tm_wday: 0,                // to_local ignores this
            tm_yday: 0,                // and this
            tm_isdst: -1,
            tm_utcoff: tm_utcoff,
            // do not set this, OS APIs are heavily inconsistent in terms of leap second handling
            tm_nsec: 0,
        };

        tm.to_timespec()
    }

    /// The local timescale. This is implemented via the standard `time` crate.
    ///
    /// Using the [`TimeZone`](./trait.TimeZone.html) methods
    /// on the Local struct is the preferred way to construct `DateTime<Local>`
    /// instances.
    ///
    /// # Example
    ///
    /// ~~~~
    /// use chrono::{Local, DateTime, TimeZone};
    ///
    /// let dt: DateTime<Local> = Local::now();
    /// let dt: DateTime<Local> = Local.timestamp(0, 0);
    /// ~~~~
    #[derive(Copy, Clone, Debug)]
    pub struct Local;

    impl Local {
        /// Returns a `Date` which corresponds to the current date.
        pub fn today() -> Date<Local> {
            Local::now().date()
        }

        /// Returns a `DateTime` which corresponds to the current date.
        #[cfg(not(all(target_arch = "wasm32", not(target_os = "wasi"), feature = "wasmbind")))]
        pub fn now() -> DateTime<Local> {
            tm_to_datetime(Timespec::now().local())
        }

        /// Returns a `DateTime` which corresponds to the current date.
        #[cfg(all(target_arch = "wasm32", not(target_os = "wasi"), feature = "wasmbind"))]
        pub fn now() -> DateTime<Local> {
            use super::Utc;
            let now: DateTime<Utc> = super::Utc::now();

            // Workaround missing timezone logic in `time` crate
            let offset = FixedOffset::west((js_sys::Date::new_0().get_timezone_offset() as i32) * 60);
            DateTime::from_utc(now.naive_utc(), offset)
        }
    }

    impl TimeZone for Local {
        type Offset = FixedOffset;

        fn from_offset(_offset: &FixedOffset) -> Local {
            Local
        }

        // they are easier to define in terms of the finished date and time unlike other offsets
        fn offset_from_local_date(&self, local: &NaiveDate) -> LocalResult<FixedOffset> {
            self.from_local_date(local).map(|date| *date.offset())
        }

        fn offset_from_local_datetime(&self, local: &NaiveDateTime) -> LocalResult<FixedOffset> {
            self.from_local_datetime(local).map(|datetime| *datetime.offset())
        }

        fn offset_from_utc_date(&self, utc: &NaiveDate) -> FixedOffset {
            *self.from_utc_date(utc).offset()
        }

        fn offset_from_utc_datetime(&self, utc: &NaiveDateTime) -> FixedOffset {
            *self.from_utc_datetime(utc).offset()
        }

        // override them for avoiding redundant works
        fn from_local_date(&self, local: &NaiveDate) -> LocalResult<Date<Local>> {
            // this sounds very strange, but required for keeping `TimeZone::ymd` sane.
            // in the other words, we use the offset at the local midnight
            // but keep the actual date unaltered (much like `FixedOffset`).
            let midnight = self.from_local_datetime(&local.and_hms(0, 0, 0));
            midnight.map(|datetime| Date::from_utc(*local, *datetime.offset()))
        }

        #[cfg(all(target_arch = "wasm32", not(target_os = "wasi"), feature = "wasmbind"))]
        fn from_local_datetime(&self, local: &NaiveDateTime) -> LocalResult<DateTime<Local>> {
            let mut local = local.clone();
            // Get the offset from the js runtime
            let offset = FixedOffset::west((js_sys::Date::new_0().get_timezone_offset() as i32) * 60);
            local -= ::Duration::seconds(offset.local_minus_utc() as i64);
            LocalResult::Single(DateTime::from_utc(local, offset))
        }

        #[cfg(not(all(target_arch = "wasm32", not(target_os = "wasi"), feature = "wasmbind")))]
        fn from_local_datetime(&self, local: &NaiveDateTime) -> LocalResult<DateTime<Local>> {
            let timespec = datetime_to_timespec(local, true);

            // datetime_to_timespec completely ignores leap seconds, so we need to adjust for them
            let mut tm = timespec.local();
            assert_eq!(tm.tm_nsec, 0);
            tm.tm_nsec = local.nanosecond() as i32;

            LocalResult::Single(tm_to_datetime(tm))
        }

        fn from_utc_date(&self, utc: &NaiveDate) -> Date<Local> {
            let midnight = self.from_utc_datetime(&utc.and_hms(0, 0, 0));
            Date::from_utc(*utc, *midnight.offset())
        }

        #[cfg(all(target_arch = "wasm32", not(target_os = "wasi"), feature = "wasmbind"))]
        fn from_utc_datetime(&self, utc: &NaiveDateTime) -> DateTime<Local> {
            // Get the offset from the js runtime
            let offset = FixedOffset::west((js_sys::Date::new_0().get_timezone_offset() as i32) * 60);
            DateTime::from_utc(*utc, offset)
        }

        #[cfg(not(all(target_arch = "wasm32", not(target_os = "wasi"), feature = "wasmbind")))]
        fn from_utc_datetime(&self, utc: &NaiveDateTime) -> DateTime<Local> {
            let timespec = datetime_to_timespec(utc, false);

            // datetime_to_timespec completely ignores leap seconds, so we need to adjust for them
            let mut tm = timespec.local();
            assert_eq!(tm.tm_nsec, 0);
            tm.tm_nsec = utc.nanosecond() as i32;

            tm_to_datetime(tm)
        }
    }

    #[cfg(test)]
    mod tests {
        use super::Local;
        use offset::TimeZone;
        use Datelike;

        #[test]
        fn test_local_date_sanity_check() {
            // issue #27
            assert_eq!(Local.ymd(2999, 12, 28).day(), 28);
        }

        #[test]
        fn test_leap_second() {
            // issue #123
            let today = Local::today();

            let dt = today.and_hms_milli(1, 2, 59, 1000);
            let timestr = dt.time().to_string();
            // the OS API may or may not support the leap second,
            // but there are only two sensible options.
            assert!(timestr == "01:02:60" || timestr == "01:03:00", "unexpected timestr {:?}", timestr);

            let dt = today.and_hms_milli(1, 2, 3, 1234);
            let timestr = dt.time().to_string();
            assert!(
                timestr == "01:02:03.234" || timestr == "01:02:04.234",
                "unexpected timestr {:?}",
                timestr
            );
        }
    }