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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 crate::cal::abstract_gregorian::{impl_with_abstract_gregorian, GregorianYears};
use crate::cal::gregorian::CeBce;
use crate::calendar_arithmetic::ArithmeticDate;
use crate::error::{DateError, UnknownEraError};
use crate::provider::{CalendarJapaneseExtendedV1, CalendarJapaneseModernV1, EraStartDate};
use crate::{types, AsCalendar, Date};
use icu_provider::prelude::*;
use tinystr::tinystr;
/// The [Japanese Calendar] (with modern eras only)
///
/// The [Japanese Calendar] is a variant of the [`Gregorian`](crate::cal::Gregorian) calendar
/// created by the Japanese government. It is identical to the Gregorian calendar except that
/// is uses Japanese eras instead of the Common Era.
///
/// This implementation extends proleptically for dates before the calendar's creation
/// in 6 Meiji (1873 CE).
/// The Meiji era is used proleptically back to and including 1868-10-23, Gregorian eras are used before that.
///
/// For a variant that uses approximations of historical Japanese eras proleptically, check out [`JapaneseExtended`].
///
/// This corresponds to the `"japanese"` [CLDR calendar](https://unicode.org/reports/tr35/#UnicodeCalendarIdentifier).
///
/// [Japanese calendar]: https://en.wikipedia.org/wiki/Japanese_calendar
///
/// # Era codes
///
/// This calendar currently supports seven era codes. It supports the five eras since its
/// introduction (`meiji`, `taisho`, `showa`, `heisei`, `reiwa`), as well as the Gregorian
/// `bce` (alias `bc`), and `ce` (alias `ad`) for earlier dates.
///
/// Future eras will also be added to this type when they are decided.
///
/// These eras are loaded from data, requiring a data provider capable of providing [`CalendarJapaneseModernV1`]
/// data.
#[derive(Clone, Debug, Default)]
pub struct Japanese {
eras: DataPayload<CalendarJapaneseModernV1>,
}
/// The [Japanese Calendar] (with historical eras)
///
/// The [Japanese Calendar] is a variant of the [`Gregorian`](crate::cal::Gregorian) calendar
/// created by the Japanese government. It is identical to the Gregorian calendar except that
/// is uses Japanese eras instead of the Common Era.
///
/// This implementation extends proleptically for dates before the calendar's creation
/// in 6 Meiji (1873 CE).
/// This implementation uses approximations of earlier Japanese eras proleptically and uses the Gregorian eras for
/// even earlier dates that don't have an approximate Japanese era.
///
/// For a variant whose Japanese eras start with Meiji, check out [`Japanese`].
///
/// This corresponds to the `"japanext"` [CLDR calendar](https://unicode.org/reports/tr35/#UnicodeCalendarIdentifier).
///
/// [Japanese calendar]: https://en.wikipedia.org/wiki/Japanese_calendar
///
/// # Era codes
///
/// This calendar supports a large number of era codes. It supports the five eras since its introduction
/// (`meiji`, `taisho`, `showa`, `heisei`, `reiwa`). Proleptic eras are represented
/// with their names converted to lowercase ASCII and followed by their start year. E.g. the *Ten'ō*
/// era (781 - 782 CE) has the code `teno-781`. The Gregorian `bce` (alias `bc`), and `ce` (alias `ad`)
/// are used for dates before the first known era era.
///
///
/// These eras are loaded from data, requiring a data provider capable of providing [`CalendarJapaneseExtendedV1`]
/// data.
#[derive(Clone, Debug, Default)]
pub struct JapaneseExtended(Japanese);
impl Japanese {
/// Creates a new [`Japanese`] using only modern eras (post-meiji) from compiled data.
///
/// ✨ *Enabled with the `compiled_data` Cargo feature.*
///
/// [📚 Help choosing a constructor](icu_provider::constructors)
#[cfg(feature = "compiled_data")]
pub const fn new() -> Self {
Self {
eras: DataPayload::from_static_ref(
crate::provider::Baked::SINGLETON_CALENDAR_JAPANESE_MODERN_V1,
),
}
}
icu_provider::gen_buffer_data_constructors!(() -> error: DataError,
functions: [
new: skip,
try_new_with_buffer_provider,
try_new_unstable,
Self,
]);
#[doc = icu_provider::gen_buffer_unstable_docs!(UNSTABLE, Self::new)]
pub fn try_new_unstable<D: DataProvider<CalendarJapaneseModernV1> + ?Sized>(
provider: &D,
) -> Result<Self, DataError> {
Ok(Self {
eras: provider.load(Default::default())?.payload,
})
}
}
impl JapaneseExtended {
/// Creates a new [`Japanese`] from using all eras (including pre-meiji) from compiled data.
///
/// ✨ *Enabled with the `compiled_data` Cargo feature.*
///
/// [📚 Help choosing a constructor](icu_provider::constructors)
#[cfg(feature = "compiled_data")]
pub const fn new() -> Self {
Self(Japanese {
eras: DataPayload::from_static_ref(
crate::provider::Baked::SINGLETON_CALENDAR_JAPANESE_EXTENDED_V1,
),
})
}
icu_provider::gen_buffer_data_constructors!(() -> error: DataError,
functions: [
new: skip,
try_new_with_buffer_provider,
try_new_unstable,
Self,
]);
#[doc = icu_provider::gen_buffer_unstable_docs!(UNSTABLE, Self::new)]
pub fn try_new_unstable<D: DataProvider<CalendarJapaneseExtendedV1> + ?Sized>(
provider: &D,
) -> Result<Self, DataError> {
Ok(Self(Japanese {
eras: provider.load(Default::default())?.payload.cast(),
}))
}
}
const MEIJI_START: EraStartDate = EraStartDate {
year: 1868,
month: 10,
day: 23,
};
const TAISHO_START: EraStartDate = EraStartDate {
year: 1912,
month: 7,
day: 30,
};
const SHOWA_START: EraStartDate = EraStartDate {
year: 1926,
month: 12,
day: 25,
};
const HEISEI_START: EraStartDate = EraStartDate {
year: 1989,
month: 1,
day: 8,
};
const REIWA_START: EraStartDate = EraStartDate {
year: 2019,
month: 5,
day: 1,
};
impl GregorianYears for &'_ Japanese {
fn extended_from_era_year(
&self,
era: Option<&[u8]>,
year: i32,
) -> Result<i32, UnknownEraError> {
if let Ok(g) = CeBce.extended_from_era_year(era, year) {
return Ok(g);
}
let Some(era) = era else {
// unreachable, handled by CeBce
return Err(UnknownEraError);
};
// Avoid linear search by trying well known eras
if era == b"reiwa" {
return Ok(year - 1 + REIWA_START.year);
} else if era == b"heisei" {
return Ok(year - 1 + HEISEI_START.year);
} else if era == b"showa" {
return Ok(year - 1 + SHOWA_START.year);
} else if era == b"taisho" {
return Ok(year - 1 + TAISHO_START.year);
} else if era == b"meiji" {
return Ok(year - 1 + MEIJI_START.year);
}
let data = &self.eras.get().dates_to_eras;
// Try to avoid linear search by binary searching for the year suffix
if let Some(start_year) = era
.split(|x| *x == b'-')
.nth(1)
.and_then(|y| core::str::from_utf8(y).ok()?.parse::<i32>().ok())
{
if let Ok(index) = data.binary_search_by(|(d, _)| d.year.cmp(&start_year)) {
// There is a slight chance we hit the case where there are two eras in the same year
// There are a couple of rare cases of this, but it's not worth writing a range-based binary search
// to catch them since this is an optimization
#[expect(clippy::unwrap_used)] // binary search
if data.get(index).unwrap().1.as_bytes() == era {
return Ok(start_year + year - 1);
}
}
}
// Avoidance didn't work. Let's find the era manually, searching back from the present
let era_start = data
.iter()
.rev()
.find_map(|(s, e)| (e.as_bytes() == era).then_some(s))
.ok_or(UnknownEraError)?;
Ok(era_start.year + year - 1)
}
fn era_year_from_extended(&self, year: i32, month: u8, day: u8) -> types::EraYear {
let date: EraStartDate = EraStartDate { year, month, day };
let (start, era) = if date >= MEIJI_START
&& self
.eras
.get()
.dates_to_eras
.last()
.is_some_and(|(_, e)| e == tinystr!(16, "reiwa"))
{
// We optimize for the five "modern" post-Meiji eras, which are stored in a smaller
// array and also hardcoded. The hardcoded version is not used if data indicates the
// presence of newer eras.
if date >= REIWA_START {
(REIWA_START, tinystr!(16, "reiwa"))
} else if date >= HEISEI_START {
(HEISEI_START, tinystr!(16, "heisei"))
} else if date >= SHOWA_START {
(SHOWA_START, tinystr!(16, "showa"))
} else if date >= TAISHO_START {
(TAISHO_START, tinystr!(16, "taisho"))
} else {
(MEIJI_START, tinystr!(16, "meiji"))
}
} else {
let data = &self.eras.get().dates_to_eras;
#[allow(clippy::unwrap_used)] // binary search
match data.binary_search_by(|(d, _)| d.cmp(&date)) {
Err(0) => {
return types::EraYear {
// TODO: return era indices?
era_index: None,
..CeBce.era_year_from_extended(year, month, day)
};
}
Ok(index) => data.get(index).unwrap(),
Err(index) => data.get(index - 1).unwrap(),
}
};
types::EraYear {
era,
era_index: None,
year: year - start.year + 1,
extended_year: year,
ambiguity: types::YearAmbiguity::CenturyRequired,
}
}
fn debug_name(&self) -> &'static str {
if self.eras.get().dates_to_eras.len() > 10 {
"Japanese (historical era data)"
} else {
"Japanese"
}
}
fn calendar_algorithm(&self) -> Option<crate::preferences::CalendarAlgorithm> {
if self.eras.get().dates_to_eras.len() > 10 {
None
} else {
Some(crate::preferences::CalendarAlgorithm::Japanese)
}
}
}
impl_with_abstract_gregorian!(Japanese, JapaneseDateInner, Japanese, this, this);
impl_with_abstract_gregorian!(
JapaneseExtended,
JapaneseExtendedDateInner,
Japanese,
this,
&this.0
);
impl Date<Japanese> {
/// Construct a new Japanese Date.
///
/// Years are specified in the era provided, and must be in range for Japanese
/// eras (e.g. dates past April 30 Heisei 31 must be in Reiwa; "Jun 5 Heisei 31" and "Jan 1 Heisei 32"
/// will not be adjusted to being in Reiwa 1 and 2 respectively)
///
/// However, dates may always be specified in "bce" or "ce" and they will be adjusted as necessary.
///
/// ```rust
/// use icu::calendar::cal::Japanese;
/// use icu::calendar::{Date, Ref};
/// use tinystr::tinystr;
///
/// let japanese_calendar = Japanese::new();
/// // for easy sharing
/// let japanese_calendar = Ref(&japanese_calendar);
///
/// let era = "heisei";
///
/// let date =
/// Date::try_new_japanese_with_calendar(era, 14, 1, 2, japanese_calendar)
/// .expect("Constructing a date should succeed");
///
/// assert_eq!(date.era_year().era, era);
/// assert_eq!(date.era_year().year, 14);
/// assert_eq!(date.month().ordinal, 1);
/// assert_eq!(date.day_of_month().0, 2);
///
/// // This function will error for unknown eras
/// let fake_era = "neko"; // 🐱
/// let fake_date = Date::try_new_japanese_with_calendar(
/// fake_era,
/// 10,
/// 1,
/// 2,
/// japanese_calendar,
/// );
/// assert!(fake_date.is_err());
/// ```
pub fn try_new_japanese_with_calendar<A: AsCalendar<Calendar = Japanese>>(
era: &str,
year: i32,
month: u8,
day: u8,
japanese_calendar: A,
) -> Result<Date<A>, DateError> {
let extended = japanese_calendar
.as_calendar()
.extended_from_era_year(Some(era.as_bytes()), year)?;
Ok(Date::from_raw(
JapaneseDateInner(ArithmeticDate::new_gregorian::<&Japanese>(
extended, month, day,
)?),
japanese_calendar,
))
}
}
impl Date<JapaneseExtended> {
/// Construct a new Japanese Date with all eras.
///
/// Years are specified in the era provided, and must be in range for Japanese
/// eras (e.g. dates past April 30 Heisei 31 must be in Reiwa; "Jun 5 Heisei 31" and "Jan 1 Heisei 32"
/// will not be adjusted to being in Reiwa 1 and 2 respectively)
///
/// However, dates may always be specified in "bce" or "ce" and they will be adjusted as necessary.
///
/// ```rust
/// use icu::calendar::cal::JapaneseExtended;
/// use icu::calendar::{Date, Ref};
/// use tinystr::tinystr;
///
/// let japanext_calendar = JapaneseExtended::new();
/// // for easy sharing
/// let japanext_calendar = Ref(&japanext_calendar);
///
/// let era = "kansei-1789";
///
/// let date = Date::try_new_japanese_extended_with_calendar(
/// era,
/// 7,
/// 1,
/// 2,
/// japanext_calendar,
/// )
/// .expect("Constructing a date should succeed");
///
/// assert_eq!(date.era_year().era, era);
/// assert_eq!(date.era_year().year, 7);
/// assert_eq!(date.month().ordinal, 1);
/// assert_eq!(date.day_of_month().0, 2);
/// ```
pub fn try_new_japanese_extended_with_calendar<A: AsCalendar<Calendar = JapaneseExtended>>(
era: &str,
year: i32,
month: u8,
day: u8,
japanext_calendar: A,
) -> Result<Date<A>, DateError> {
let extended = (&japanext_calendar.as_calendar().0)
.extended_from_era_year(Some(era.as_bytes()), year)?;
Ok(Date::from_raw(
JapaneseExtendedDateInner(ArithmeticDate::new_gregorian::<&Japanese>(
extended, month, day,
)?),
japanext_calendar,
))
}
}
#[cfg(test)]
mod tests {
use super::*;
use crate::Ref;
fn single_test_roundtrip(calendar: Ref<Japanese>, era: &str, year: i32, month: u8, day: u8) {
let date = Date::try_new_japanese_with_calendar(era, year, month, day, calendar)
.unwrap_or_else(|e| {
panic!("Failed to construct date with {era:?}, {year}, {month}, {day}: {e:?}")
});
let iso = date.to_iso();
let reconstructed = Date::new_from_iso(iso, calendar);
assert_eq!(
date, reconstructed,
"Failed to roundtrip with {era:?}, {year}, {month}, {day}"
);
// Extra coverage for https://github.com/unicode-org/icu4x/issues/4968
assert_eq!(reconstructed.era_year().era, era);
assert_eq!(reconstructed.era_year().year, year);
}
fn single_test_roundtrip_ext(
calendar: Ref<JapaneseExtended>,
era: &str,
year: i32,
month: u8,
day: u8,
) {
let date = Date::try_new_japanese_extended_with_calendar(era, year, month, day, calendar)
.unwrap_or_else(|e| {
panic!("Failed to construct date with {era:?}, {year}, {month}, {day}: {e:?}")
});
let iso = date.to_iso();
let reconstructed = Date::new_from_iso(iso, calendar);
assert_eq!(
date, reconstructed,
"Failed to roundtrip with {era:?}, {year}, {month}, {day}"
)
}
// test that out-of-range era values roundtrip to other eras
fn single_test_era_range_roundtrip(
calendar: Ref<Japanese>,
era: &str,
year: i32,
month: u8,
day: u8,
era2: &str,
year2: i32,
) {
let expected = Date::try_new_japanese_with_calendar(era2, year2, month, day, calendar)
.unwrap_or_else(|e| {
panic!(
"Failed to construct expectation date with {era2:?}, {year2}, {month}, {day}: {e:?}"
)
});
let date = Date::try_new_japanese_with_calendar(era, year, month, day, calendar)
.unwrap_or_else(|e| {
panic!("Failed to construct date with {era:?}, {year}, {month}, {day}: {e:?}")
});
let iso = date.to_iso();
let reconstructed = Date::new_from_iso(iso, calendar);
assert_eq!(
expected, reconstructed,
"Failed to roundtrip with {era:?}, {year}, {month}, {day} == {era2:?}, {year}"
)
}
fn single_test_era_range_roundtrip_ext(
calendar: Ref<JapaneseExtended>,
era: &str,
year: i32,
month: u8,
day: u8,
era2: &str,
year2: i32,
) {
let expected = Date::try_new_japanese_extended_with_calendar(era2, year2, month, day, calendar)
.unwrap_or_else(|e| {
panic!(
"Failed to construct expectation date with {era2:?}, {year2}, {month}, {day}: {e:?}"
)
});
let date = Date::try_new_japanese_extended_with_calendar(era, year, month, day, calendar)
.unwrap_or_else(|e| {
panic!("Failed to construct date with {era:?}, {year}, {month}, {day}: {e:?}")
});
let iso = date.to_iso();
let reconstructed = Date::new_from_iso(iso, calendar);
assert_eq!(
expected, reconstructed,
"Failed to roundtrip with {era:?}, {year}, {month}, {day} == {era2:?}, {year}"
)
}
fn single_test_error(
calendar: Ref<Japanese>,
era: &str,
year: i32,
month: u8,
day: u8,
error: DateError,
) {
let date = Date::try_new_japanese_with_calendar(era, year, month, day, calendar);
assert_eq!(
date,
Err(error),
"Construction with {era:?}, {year}, {month}, {day} did not return {error:?}"
)
}
#[test]
fn test_japanese() {
let calendar = Japanese::new();
let calendar_ext = JapaneseExtended::new();
let calendar = Ref(&calendar);
let calendar_ext = Ref(&calendar_ext);
single_test_roundtrip(calendar, "heisei", 12, 3, 1);
single_test_roundtrip(calendar, "taisho", 3, 3, 1);
// Heisei did not start until later in the year
single_test_era_range_roundtrip(calendar, "heisei", 1, 1, 1, "showa", 64);
single_test_roundtrip_ext(calendar_ext, "heisei", 12, 3, 1);
single_test_roundtrip_ext(calendar_ext, "taisho", 3, 3, 1);
single_test_era_range_roundtrip_ext(calendar_ext, "heisei", 1, 1, 1, "showa", 64);
single_test_roundtrip_ext(calendar_ext, "hakuho-672", 4, 3, 1);
single_test_error(calendar, "hakuho-672", 4, 3, 1, DateError::UnknownEra);
// handle bce/ce
single_test_roundtrip(calendar, "bce", 100, 3, 1);
single_test_roundtrip(calendar, "bce", 1, 3, 1);
single_test_roundtrip(calendar, "ce", 1, 3, 1);
single_test_roundtrip(calendar, "ce", 100, 3, 1);
single_test_roundtrip_ext(calendar_ext, "ce", 100, 3, 1);
single_test_roundtrip(calendar, "ce", 1000, 3, 1);
single_test_era_range_roundtrip(calendar, "ce", 0, 3, 1, "bce", 1);
single_test_era_range_roundtrip(calendar, "bce", -1, 3, 1, "ce", 2);
// handle the cases where bce/ce get adjusted to different eras
// single_test_gregorian_roundtrip(calendar, "ce", 2021, 3, 1, "reiwa", 3);
single_test_era_range_roundtrip_ext(calendar_ext, "ce", 1000, 3, 1, "choho-999", 2);
single_test_era_range_roundtrip_ext(calendar_ext, "ce", 749, 5, 10, "tenpyokampo-749", 1);
single_test_era_range_roundtrip_ext(calendar_ext, "bce", 10, 3, 1, "bce", 10);
single_test_era_range_roundtrip_ext(calendar_ext, "ce", -1, 3, 1, "bce", 2);
// There were multiple eras in this year
// This one is from Apr 14 to July 2
single_test_roundtrip_ext(calendar_ext, "tenpyokampo-749", 1, 4, 20);
single_test_roundtrip_ext(calendar_ext, "tenpyokampo-749", 1, 4, 14);
single_test_roundtrip_ext(calendar_ext, "tenpyokampo-749", 1, 7, 1);
single_test_era_range_roundtrip_ext(
calendar_ext,
"tenpyokampo-749",
1,
7,
5,
"tenpyoshoho-749",
1,
);
single_test_era_range_roundtrip_ext(
calendar_ext,
"tenpyokampo-749",
1,
4,
13,
"tenpyoshoho-749",
1,
);
}
}