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// This file is part of ICU4X. For terms of use, please see the file
// called LICENSE at the top level of the ICU4X source tree
// (online at: https://github.com/unicode-org/icu4x/blob/main/LICENSE ).
use core::fmt;
use crate::{
input::TimeZoneInput,
time_zone::{FormatTimeZone, FormatTimeZoneWithFallback, TimeZoneFormatter},
DateTimeError,
};
use writeable::Writeable;
/// [`FormattedTimeZone`] is a intermediate structure which can be retrieved as an output from [`TimeZoneFormatter`].
#[derive(Debug, Copy, Clone)]
pub struct FormattedTimeZone<'l, T>
where
T: TimeZoneInput,
{
pub(crate) time_zone_format: &'l TimeZoneFormatter,
pub(crate) time_zone: &'l T,
}
impl<'l, T> Writeable for FormattedTimeZone<'l, T>
where
T: TimeZoneInput,
{
/// Format time zone with fallbacks.
fn write_to<W: fmt::Write + ?Sized>(&self, sink: &mut W) -> fmt::Result {
let mut sink = writeable::adapters::CoreWriteAsPartsWrite(sink);
let r = match self.write_no_fallback(&mut sink) {
Ok(fmt_result) => Ok(fmt_result?),
Err(_) => self
.time_zone_format
.fallback_unit
.format_with_last_resort_fallback(
&mut sink,
self.time_zone,
&self.time_zone_format.data_payloads,
)?,
};
debug_assert!(r.is_ok(), "{r:?}");
Ok(())
}
// TODO(#489): Implement writeable_length_hint
}
impl<'l, T> fmt::Display for FormattedTimeZone<'l, T>
where
T: TimeZoneInput,
{
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
self.write_to(f)
}
}
impl<'l, T> FormattedTimeZone<'l, T>
where
T: TimeZoneInput,
{
/// Write time zone with no fallback.
///
/// # Examples
///
/// ```
/// use icu::datetime::time_zone::TimeZoneFormatter;
/// use icu::datetime::DateTimeError;
/// use icu::locid::locale;
/// use icu::timezone::CustomTimeZone;
/// use tinystr::tinystr;
///
/// let mut tzf =
/// TimeZoneFormatter::try_new(&locale!("en").into(), Default::default())
/// .unwrap();
/// let mut buf = String::new();
///
/// let mut time_zone = "Z".parse::<CustomTimeZone>().unwrap();
/// time_zone.time_zone_id = Some(tinystr!(8, "gblon").into());
///
/// // There are no non-fallback formats enabled:
/// assert!(matches!(
/// tzf.format(&time_zone).write_no_fallback(&mut buf),
/// Err(DateTimeError::UnsupportedOptions)
/// ));
/// assert!(buf.is_empty());
///
/// // Enable a non-fallback format:
/// tzf.include_generic_location_format().unwrap();
/// assert!(matches!(
/// tzf.format(&time_zone).write_no_fallback(&mut buf),
/// Ok(Ok(_))
/// ));
/// assert_eq!("London Time", buf);
///
/// // Errors still occur if the time zone is not supported:
/// buf.clear();
/// time_zone.time_zone_id = Some(tinystr!(8, "zzzzz").into());
/// assert!(matches!(
/// tzf.format(&time_zone).write_no_fallback(&mut buf),
/// Err(DateTimeError::UnsupportedOptions)
/// ));
///
/// // Use the `Writable` trait instead to enable infallible formatting:
/// writeable::assert_writeable_eq!(tzf.format(&time_zone), "GMT");
/// ```
pub fn write_no_fallback<W>(&self, mut w: &mut W) -> Result<fmt::Result, DateTimeError>
where
W: core::fmt::Write + ?Sized,
{
for unit in self.time_zone_format.format_units.iter() {
match unit.format(
&mut writeable::adapters::CoreWriteAsPartsWrite(&mut w),
self.time_zone,
&self.time_zone_format.data_payloads,
) {
Ok(r) => return Ok(r),
Err(DateTimeError::UnsupportedOptions) => continue,
Err(e) => return Err(e),
}
}
Err(DateTimeError::UnsupportedOptions)
}
}