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use core::cmp::Ordering;
use core::fmt::{Debug, Display, Error, Formatter};
use chrono::{
Duration, FixedOffset, LocalResult, NaiveDate, NaiveDateTime, NaiveTime, Offset, TimeZone,
};
use crate::binary_search::binary_search;
use crate::timezones::Tz;
/// Returns [`Tz::UTC`].
impl Default for Tz {
fn default() -> Self {
Tz::UTC
}
}
/// An Offset that applies for a period of time
///
/// For example, [`::US::Eastern`] is composed of at least two
/// `FixedTimespan`s: `EST` and `EDT`, that are variously in effect.
#[derive(Copy, Clone, PartialEq, Eq)]
pub struct FixedTimespan {
/// The base offset from UTC; this usually doesn't change unless the government changes something
pub utc_offset: i32,
/// The additional offset from UTC for this timespan; typically for daylight saving time
pub dst_offset: i32,
/// The name of this timezone, for example the difference between `EDT`/`EST`
pub name: &'static str,
}
impl Offset for FixedTimespan {
fn fix(&self) -> FixedOffset {
FixedOffset::east_opt(self.utc_offset + self.dst_offset).unwrap()
}
}
impl Display for FixedTimespan {
fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), Error> {
write!(f, "{}", self.name)
}
}
impl Debug for FixedTimespan {
fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), Error> {
write!(f, "{}", self.name)
}
}
#[derive(Copy, Clone, PartialEq, Eq)]
pub struct TzOffset {
tz: Tz,
offset: FixedTimespan,
}
/// Detailed timezone offset components that expose any special conditions currently in effect.
///
/// This trait breaks down an offset into the standard UTC offset and any special offset
/// in effect (such as DST) at a given time.
///
/// ```
/// # extern crate chrono;
/// # extern crate chrono_tz;
/// use chrono::{Duration, Offset, TimeZone};
/// use chrono_tz::Europe::London;
/// use chrono_tz::OffsetComponents;
///
/// # fn main() {
/// let london_time = London.ymd(2016, 5, 10).and_hms(12, 0, 0);
///
/// // London typically has zero offset from UTC, but has a 1h adjustment forward
/// // when summer time is in effect.
/// let lon_utc_offset = london_time.offset().base_utc_offset();
/// let lon_dst_offset = london_time.offset().dst_offset();
/// let total_offset = lon_utc_offset + lon_dst_offset;
/// assert_eq!(lon_utc_offset, Duration::hours(0));
/// assert_eq!(lon_dst_offset, Duration::hours(1));
///
/// // As a sanity check, make sure that the total offsets added together are equivalent to the
/// // total fixed offset.
/// assert_eq!(total_offset.num_seconds(), london_time.offset().fix().local_minus_utc() as i64);
/// # }
/// ```
pub trait OffsetComponents {
/// The base offset from UTC; this usually doesn't change unless the government changes something
fn base_utc_offset(&self) -> Duration;
/// The additional offset from UTC that is currently in effect; typically for daylight saving time
fn dst_offset(&self) -> Duration;
}
/// Timezone offset name information.
///
/// This trait exposes display names that describe an offset in
/// various situations.
///
/// ```
/// # extern crate chrono;
/// # extern crate chrono_tz;
/// use chrono::{Duration, Offset, TimeZone};
/// use chrono_tz::Europe::London;
/// use chrono_tz::OffsetName;
///
/// # fn main() {
/// let london_time = London.ymd(2016, 2, 10).and_hms(12, 0, 0);
/// assert_eq!(london_time.offset().tz_id(), "Europe/London");
/// // London is normally on GMT
/// assert_eq!(london_time.offset().abbreviation(), "GMT");
///
/// let london_summer_time = London.ymd(2016, 5, 10).and_hms(12, 0, 0);
/// // The TZ ID remains constant year round
/// assert_eq!(london_summer_time.offset().tz_id(), "Europe/London");
/// // During the summer, this becomes British Summer Time
/// assert_eq!(london_summer_time.offset().abbreviation(), "BST");
/// # }
/// ```
pub trait OffsetName {
/// The IANA TZDB identifier (ex: America/New_York)
fn tz_id(&self) -> &str;
/// The abbreviation to use in a longer timestamp (ex: EST)
///
/// This takes into account any special offsets that may be in effect.
/// For example, at a given instant, the time zone with ID *America/New_York*
/// may be either *EST* or *EDT*.
fn abbreviation(&self) -> &str;
}
impl TzOffset {
fn new(tz: Tz, offset: FixedTimespan) -> Self {
TzOffset { tz, offset }
}
fn map_localresult(tz: Tz, result: LocalResult<FixedTimespan>) -> LocalResult<Self> {
match result {
LocalResult::None => LocalResult::None,
LocalResult::Single(s) => LocalResult::Single(TzOffset::new(tz, s)),
LocalResult::Ambiguous(a, b) => {
LocalResult::Ambiguous(TzOffset::new(tz, a), TzOffset::new(tz, b))
}
}
}
}
impl OffsetComponents for TzOffset {
fn base_utc_offset(&self) -> Duration {
Duration::seconds(self.offset.utc_offset as i64)
}
fn dst_offset(&self) -> Duration {
Duration::seconds(self.offset.dst_offset as i64)
}
}
impl OffsetName for TzOffset {
fn tz_id(&self) -> &str {
self.tz.name()
}
fn abbreviation(&self) -> &str {
self.offset.name
}
}
impl Offset for TzOffset {
fn fix(&self) -> FixedOffset {
self.offset.fix()
}
}
impl Display for TzOffset {
fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), Error> {
Display::fmt(&self.offset, f)
}
}
impl Debug for TzOffset {
fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), Error> {
Debug::fmt(&self.offset, f)
}
}
/// Represents the span of time that a given rule is valid for.
/// Note that I have made the assumption that all ranges are
/// left-inclusive and right-exclusive - that is to say,
/// if the clocks go forward by 1 hour at 1am, the time 1am
/// does not exist in local time (the clock goes from 00:59:59
/// to 02:00:00). Likewise, if the clocks go back by one hour
/// at 2am, the clock goes from 01:59:59 to 01:00:00. This is
/// an arbitrary choice, and I could not find a source to
/// confirm whether or not this is correct.
struct Span {
begin: Option<i64>,
end: Option<i64>,
}
impl Span {
fn contains(&self, x: i64) -> bool {
match (self.begin, self.end) {
(Some(a), Some(b)) if a <= x && x < b => true,
(Some(a), None) if a <= x => true,
(None, Some(b)) if b > x => true,
(None, None) => true,
_ => false,
}
}
fn cmp(&self, x: i64) -> Ordering {
match (self.begin, self.end) {
(Some(a), Some(b)) if a <= x && x < b => Ordering::Equal,
(Some(a), Some(b)) if a <= x && b <= x => Ordering::Less,
(Some(_), Some(_)) => Ordering::Greater,
(Some(a), None) if a <= x => Ordering::Equal,
(Some(_), None) => Ordering::Greater,
(None, Some(b)) if b <= x => Ordering::Less,
(None, Some(_)) => Ordering::Equal,
(None, None) => Ordering::Equal,
}
}
}
#[derive(Copy, Clone)]
pub struct FixedTimespanSet {
pub first: FixedTimespan,
pub rest: &'static [(i64, FixedTimespan)],
}
impl FixedTimespanSet {
fn len(&self) -> usize {
1 + self.rest.len()
}
fn utc_span(&self, index: usize) -> Span {
debug_assert!(index < self.len());
Span {
begin: if index == 0 { None } else { Some(self.rest[index - 1].0) },
end: if index == self.rest.len() { None } else { Some(self.rest[index].0) },
}
}
fn local_span(&self, index: usize) -> Span {
debug_assert!(index < self.len());
Span {
begin: if index == 0 {
None
} else {
let span = self.rest[index - 1];
Some(span.0 + span.1.utc_offset as i64 + span.1.dst_offset as i64)
},
end: if index == self.rest.len() {
None
} else if index == 0 {
Some(
self.rest[index].0
+ self.first.utc_offset as i64
+ self.first.dst_offset as i64,
)
} else {
Some(
self.rest[index].0
+ self.rest[index - 1].1.utc_offset as i64
+ self.rest[index - 1].1.dst_offset as i64,
)
},
}
}
fn get(&self, index: usize) -> FixedTimespan {
debug_assert!(index < self.len());
if index == 0 {
self.first
} else {
self.rest[index - 1].1
}
}
}
pub trait TimeSpans {
fn timespans(&self) -> FixedTimespanSet;
}
impl TimeZone for Tz {
type Offset = TzOffset;
fn from_offset(offset: &Self::Offset) -> Self {
offset.tz
}
#[allow(deprecated)]
fn offset_from_local_date(&self, local: &NaiveDate) -> LocalResult<Self::Offset> {
let earliest = self.offset_from_local_datetime(&local.and_time(NaiveTime::MIN));
let latest = self.offset_from_local_datetime(&local.and_hms_opt(23, 59, 59).unwrap());
// From the chrono docs:
//
// > This type should be considered ambiguous at best, due to the inherent lack of
// > precision required for the time zone resolution. There are some guarantees on the usage
// > of `Date<Tz>`:
// > - If properly constructed via `TimeZone::ymd` and others without an error,
// > the corresponding local date should exist for at least a moment.
// > (It may still have a gap from the offset changes.)
//
// > - The `TimeZone` is free to assign *any* `Offset` to the local date,
// > as long as that offset did occur in given day.
// > For example, if `2015-03-08T01:59-08:00` is followed by `2015-03-08T03:00-07:00`,
// > it may produce either `2015-03-08-08:00` or `2015-03-08-07:00`
// > but *not* `2015-03-08+00:00` and others.
//
// > - Once constructed as a full `DateTime`,
// > `DateTime::date` and other associated methods should return those for the original `Date`.
// > For example, if `dt = tz.ymd(y,m,d).hms(h,n,s)` were valid, `dt.date() == tz.ymd(y,m,d)`.
//
// > - The date is timezone-agnostic up to one day (i.e. practically always),
// > so the local date and UTC date should be equal for most cases
// > even though the raw calculation between `NaiveDate` and `Duration` may not.
//
// For these reasons we return always a single offset here if we can, rather than being
// technically correct and returning Ambiguous(_,_) on days when the clock changes. The
// alternative is painful errors when computing unambiguous times such as
// `TimeZone.ymd(ambiguous_date).hms(unambiguous_time)`.
use chrono::LocalResult::*;
match (earliest, latest) {
(result @ Single(_), _) => result,
(_, result @ Single(_)) => result,
(Ambiguous(offset, _), _) => Single(offset),
(_, Ambiguous(offset, _)) => Single(offset),
(None, None) => None,
}
}
// First search for a timespan that the local datetime falls into, then, if it exists,
// check the two surrounding timespans (if they exist) to see if there is any ambiguity.
fn offset_from_local_datetime(&self, local: &NaiveDateTime) -> LocalResult<Self::Offset> {
let timestamp = local.and_utc().timestamp();
let timespans = self.timespans();
let index = binary_search(0, timespans.len(), |i| timespans.local_span(i).cmp(timestamp));
TzOffset::map_localresult(
*self,
match index {
Ok(0) if timespans.len() == 1 => LocalResult::Single(timespans.get(0)),
Ok(0) if timespans.local_span(1).contains(timestamp) => {
LocalResult::Ambiguous(timespans.get(0), timespans.get(1))
}
Ok(0) => LocalResult::Single(timespans.get(0)),
Ok(i) if timespans.local_span(i - 1).contains(timestamp) => {
LocalResult::Ambiguous(timespans.get(i - 1), timespans.get(i))
}
Ok(i) if i == timespans.len() - 1 => LocalResult::Single(timespans.get(i)),
Ok(i) if timespans.local_span(i + 1).contains(timestamp) => {
LocalResult::Ambiguous(timespans.get(i), timespans.get(i + 1))
}
Ok(i) => LocalResult::Single(timespans.get(i)),
Err(_) => LocalResult::None,
},
)
}
#[allow(deprecated)]
fn offset_from_utc_date(&self, utc: &NaiveDate) -> Self::Offset {
// See comment above for why it is OK to just take any arbitrary time in the day
self.offset_from_utc_datetime(&utc.and_time(NaiveTime::MIN))
}
// Binary search for the required timespan. Any i64 is guaranteed to fall within
// exactly one timespan, no matter what (so the `unwrap` is safe).
fn offset_from_utc_datetime(&self, dt: &NaiveDateTime) -> Self::Offset {
let timestamp = dt.and_utc().timestamp();
let timespans = self.timespans();
let index =
binary_search(0, timespans.len(), |i| timespans.utc_span(i).cmp(timestamp)).unwrap();
TzOffset::new(*self, timespans.get(index))
}
}