// 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 ).

//! This module contains types and implementations for the Chinese calendar.
//!
//! ```rust
//! use icu::calendar::{cal::Chinese, Date, DateTime, Ref};
//!
//! let chinese = Chinese::new();
//! let chinese = Ref(&chinese); // to avoid cloning
//!
//! // `Date` type
//! let chinese_date = Date::try_new_chinese_with_calendar(4660, 6, 6, chinese)
//!     .expect("Failed to initialize Chinese Date instance.");
//!
//! // `DateTime` type
//! let chinese_datetime =
//!     DateTime::try_new_chinese_with_calendar(4660, 6, 6, 13, 1, 0, chinese)
//!         .expect("Failed to initialize Chinese DateTime instance");
//!
//! // `Date` checks
//! assert_eq!(chinese_date.year().era_year_or_extended(), 4660);
//! assert_eq!(chinese_date.year().cyclic().unwrap().get(), 40);
//! assert_eq!(chinese_date.month().ordinal, 6);
//! assert_eq!(chinese_date.day_of_month().0, 6);
//!
//! // `DateTime` checks
//! assert_eq!(chinese_datetime.date.year().era_year_or_extended(), 4660);
//! assert_eq!(chinese_datetime.date.year().cyclic().unwrap().get(), 40);
//! assert_eq!(chinese_datetime.date.month().ordinal, 6);
//! assert_eq!(chinese_datetime.date.day_of_month().0, 6);
//! assert_eq!(chinese_datetime.time.hour.number(), 13);
//! assert_eq!(chinese_datetime.time.minute.number(), 1);
//! assert_eq!(chinese_datetime.time.second.number(), 0);
//! ```

use crate::calendar_arithmetic::CalendarArithmetic;
use crate::calendar_arithmetic::PrecomputedDataSource;
use crate::chinese_based::{
    chinese_based_ordinal_lunar_month_from_code, ChineseBasedDateInner,
    ChineseBasedPrecomputedData, ChineseBasedWithDataLoading, ChineseBasedYearInfo,
};
use crate::error::DateError;
use crate::iso::Iso;
use crate::provider::chinese_based::ChineseCacheV1Marker;
use crate::AsCalendar;
use crate::{types, Calendar, Date, DateDuration, DateDurationUnit, DateTime, Time};
use core::cmp::Ordering;
use core::num::NonZeroU8;
use icu_provider::prelude::*;
use tinystr::tinystr;

/// The Chinese Calendar
///
/// The [Chinese Calendar] is a lunisolar calendar used traditionally in China as well as in other
/// countries particularly in, but not limited to, East Asia. It is often used today to track important
/// cultural events and holidays like the Chinese Lunar New Year.
///
/// This type can be used with [`Date`] or [`DateTime`] to represent dates in the Chinese calendar.
///
/// # Months
///
/// The Chinese calendar is an astronomical calendar which uses the phases of the moon to track months.
/// Each month starts on the date of the new moon as observed from China, meaning that months last 29
/// or 30 days.
///
/// One year in the Chinese calendar is typically 12 lunar months; however, because 12 lunar months does
/// not line up to one solar year, the Chinese calendar will add an intercalary leap month approximately
/// every three years to keep Chinese calendar months in line with the solar year.
///
/// Leap months can happen after any month; the month in which a leap month occurs is based on the alignment
/// of months with 24 solar terms into which the solar year is divided.
///
/// # Year and Era codes
///
/// Unlike the Gregorian calendar, the Chinese calendar does not traditionally count years in an infinitely
/// increasing sequence. Instead, 10 "celestial stems" and 12 "terrestrial branches" are combined to form a
/// cycle of year names which repeats every 60 years. However, for the purposes of calendar calculations and
/// conversions, this module counts Chinese years in an infinite system similar to ISO, with year 1 in the
/// calendar corresponding to the inception of the calendar, marked as 2637 BCE (ISO: -2636), and negative
/// years marking Chinese years before February 15, 2637 BCE.
///
/// Because the Chinese calendar does not traditionally count years, era codes are not used in this calendar;
/// this crate supports a single era code "chinese".
///
/// This Chinese calendar implementation also supports a related ISO year, which marks the ISO year in which a
/// Chinese year begins, and a cyclic year corresponding to the year in the 60 year cycle as described above.
///
/// For more information, suggested reading materials include:
/// * _Calendrical Calculations_ by Reingold & Dershowitz
/// * _The Mathematics of the Chinese Calendar_ by Helmer Aslaksen <https://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.139.9311&rep=rep1&type=pdf>
/// * Wikipedia: <https://en.wikipedia.org/wiki/Chinese_calendar>
///
/// # Month codes
///
/// This calendar is a lunisolar calendar. It supports regular month codes `"M01" - "M12"` as well
/// as leap month codes `"M01L" - "M12L"`.
///
/// This calendar is currently in a preview state: formatting for this calendar is not
/// going to be perfect.
#[derive(Clone, Debug, Default)]
pub struct Chinese {
    data: Option<DataPayload<ChineseCacheV1Marker>>,
}

/// The inner date type used for representing [`Date`]s of [`Chinese`]. See [`Date`] and [`Chinese`] for more details.
#[derive(Debug, Eq, PartialEq, PartialOrd, Ord)]
pub struct ChineseDateInner(ChineseBasedDateInner<Chinese>);

type Inner = ChineseBasedDateInner<Chinese>;

// we want these impls without the `C: Copy/Clone` bounds
impl Copy for ChineseDateInner {}
impl Clone for ChineseDateInner {
    fn clone(&self) -> Self {
        *self
    }
}

// These impls just make custom derives on types containing C
// work. They're basically no-ops
impl PartialEq for Chinese {
    fn eq(&self, _: &Self) -> bool {
        true
    }
}
impl Eq for Chinese {}
#[allow(clippy::non_canonical_partial_ord_impl)] // this is intentional
impl PartialOrd for Chinese {
    fn partial_cmp(&self, _: &Self) -> Option<Ordering> {
        Some(Ordering::Equal)
    }
}

impl Ord for Chinese {
    fn cmp(&self, _: &Self) -> Ordering {
        Ordering::Equal
    }
}

impl Chinese {
    /// Creates a new [`Chinese`] with some precomputed calendrical calculations.
    ///
    /// ✨ *Enabled with the `compiled_data` Cargo feature.*
    ///
    /// [📚 Help choosing a constructor](icu_provider::constructors)
    #[cfg(feature = "compiled_data")]
    pub const fn new() -> Self {
        Self {
            data: Some(DataPayload::from_static_ref(
                crate::provider::Baked::SINGLETON_CHINESE_CACHE_V1_MARKER,
            )),
        }
    }

    icu_provider::gen_any_buffer_data_constructors!(() -> error: DataError,
        functions: [
            new: skip,
            try_new_with_any_provider,
            try_new_with_buffer_provider,
            try_new_unstable,
            Self,
    ]);

    #[doc = icu_provider::gen_any_buffer_unstable_docs!(UNSTABLE, Self::new)]
    pub fn try_new_unstable<D: DataProvider<ChineseCacheV1Marker> + ?Sized>(
        provider: &D,
    ) -> Result<Self, DataError> {
        Ok(Self {
            data: Some(provider.load(Default::default())?.payload),
        })
    }

    /// Construct a new [`Chinese`] without any precomputed calendrical calculations.
    pub fn new_always_calculating() -> Self {
        Chinese { data: None }
    }

    pub(crate) const DEBUG_NAME: &'static str = "Chinese";
}

impl Calendar for Chinese {
    type DateInner = ChineseDateInner;

    // Construct a date from era/month codes and fields
    fn date_from_codes(
        &self,
        era: Option<types::Era>,
        year: i32,
        month_code: types::MonthCode,
        day: u8,
    ) -> Result<Self::DateInner, DateError> {
        let year_info = self.get_precomputed_data().load_or_compute_info(year);

        let month = if let Some(ordinal) =
            chinese_based_ordinal_lunar_month_from_code(month_code, year_info)
        {
            ordinal
        } else {
            return Err(DateError::UnknownMonthCode(month_code));
        };

        if let Some(era) = era {
            if era.0 != tinystr!(16, "chinese") {
                return Err(DateError::UnknownEra(era));
            }
        }

        Inner::new_from_ordinals(year, month, day, year_info)
            .map(ChineseBasedDateInner)
            .map(ChineseDateInner)
    }

    // Construct the date from an ISO date
    fn date_from_iso(&self, iso: Date<Iso>) -> Self::DateInner {
        let fixed = Iso::fixed_from_iso(iso.inner);
        ChineseDateInner(Inner::chinese_based_date_from_fixed(
            self,
            fixed,
            iso.inner.0,
        ))
    }

    // Obtain an ISO date from a Chinese date
    fn date_to_iso(&self, date: &Self::DateInner) -> Date<Iso> {
        let fixed = Inner::fixed_from_chinese_based_date_inner(date.0);
        Iso::iso_from_fixed(fixed)
    }

    //Count the number of months in a given year, specified by providing a date
    // from that year
    fn days_in_year(&self, date: &Self::DateInner) -> u16 {
        date.0.days_in_year_inner()
    }

    fn days_in_month(&self, date: &Self::DateInner) -> u8 {
        date.0.days_in_month_inner()
    }

    #[doc(hidden)] // unstable
    fn offset_date(&self, date: &mut Self::DateInner, offset: DateDuration<Self>) {
        date.0 .0.offset_date(offset, &self.get_precomputed_data());
    }

    #[doc(hidden)] // unstable
    #[allow(clippy::field_reassign_with_default)]
    /// Calculate `date2 - date` as a duration
    ///
    /// `calendar2` is the calendar object associated with `date2`. In case the specific calendar objects
    /// differ on date, the date for the first calendar is used, and `date2` may be converted if necessary.
    fn until(
        &self,
        date1: &Self::DateInner,
        date2: &Self::DateInner,
        _calendar2: &Self,
        _largest_unit: DateDurationUnit,
        _smallest_unit: DateDurationUnit,
    ) -> DateDuration<Self> {
        date1.0 .0.until(date2.0 .0, _largest_unit, _smallest_unit)
    }

    /// Obtain a name for the calendar for debug printing
    fn debug_name(&self) -> &'static str {
        Self::DEBUG_NAME
    }

    fn year(&self, date: &Self::DateInner) -> types::YearInfo {
        Self::format_chinese_year(date.0 .0.year, Some(date.0 .0.year_info))
    }

    fn is_in_leap_year(&self, date: &Self::DateInner) -> bool {
        Self::is_leap_year(date.0 .0.year, date.0 .0.year_info)
    }

    /// The calendar-specific month code represented by `date`;
    /// since the Chinese calendar has leap months, an "L" is appended to the month code for
    /// leap months. For example, in a year where an intercalary month is added after the second
    /// month, the month codes for ordinal months 1, 2, 3, 4, 5 would be "M01", "M02", "M02L", "M03", "M04".
    fn month(&self, date: &Self::DateInner) -> types::MonthInfo {
        date.0.month()
    }

    /// The calendar-specific day-of-month represented by `date`
    fn day_of_month(&self, date: &Self::DateInner) -> types::DayOfMonth {
        types::DayOfMonth(date.0 .0.day)
    }

    /// Information of the day of the year
    fn day_of_year_info(&self, date: &Self::DateInner) -> types::DayOfYearInfo {
        let prev_year = date.0 .0.year.saturating_sub(1);
        let next_year = date.0 .0.year.saturating_add(1);
        types::DayOfYearInfo {
            day_of_year: date.0.day_of_year(),
            days_in_year: date.0.days_in_year_inner(),
            prev_year: Self::format_chinese_year(prev_year, None),
            days_in_prev_year: date.0.days_in_prev_year(),
            next_year: Self::format_chinese_year(next_year, None),
        }
    }

    fn any_calendar_kind(&self) -> Option<crate::AnyCalendarKind> {
        Some(crate::any_calendar::IntoAnyCalendar::kind(self))
    }

    fn months_in_year(&self, date: &Self::DateInner) -> u8 {
        date.0.months_in_year_inner()
    }
}

impl<A: AsCalendar<Calendar = Chinese>> Date<A> {
    /// Construct a new Chinese date from a `year`, `month`, and `day`.
    /// `year` represents the Chinese year counted infinitely with -2636 (2637 BCE) as Chinese year 1;
    /// `month` represents the month of the year ordinally (ex. if it is a leap year, the last month will be 13, not 12);
    /// `day` indicates the day of month
    ///
    /// This date will not use any precomputed calendrical calculations,
    /// one that loads such data from a provider will be added in the future (#3933)
    ///
    /// ```rust
    /// use icu::calendar::{cal::Chinese, Date};
    ///
    /// let chinese = Chinese::new_always_calculating();
    ///
    /// let date_chinese =
    ///     Date::try_new_chinese_with_calendar(4660, 6, 11, chinese)
    ///         .expect("Failed to initialize Chinese Date instance.");
    ///
    /// assert_eq!(date_chinese.year().era_year_or_extended(), 4660);
    /// assert_eq!(date_chinese.year().cyclic().unwrap().get(), 40);
    /// assert_eq!(date_chinese.year().related_iso(), Some(2023));
    /// assert_eq!(date_chinese.month().ordinal, 6);
    /// assert_eq!(date_chinese.day_of_month().0, 11);
    /// ```
    pub fn try_new_chinese_with_calendar(
        year: i32,
        month: u8,
        day: u8,
        calendar: A,
    ) -> Result<Date<A>, DateError> {
        let year_info = calendar
            .as_calendar()
            .get_precomputed_data()
            .load_or_compute_info(year);
        let arithmetic = Inner::new_from_ordinals(year, month, day, year_info);
        Ok(Date::from_raw(
            ChineseDateInner(ChineseBasedDateInner(arithmetic?)),
            calendar,
        ))
    }
}

impl<A: AsCalendar<Calendar = Chinese>> DateTime<A> {
    /// Construct a new Chinese datetime from integers using the
    /// -2636-based year system
    ///
    /// This datetime will not use any precomputed calendrical calculations,
    /// one that loads such data from a provider will be added in the future (#3933)
    ///
    /// ```rust
    /// use icu::calendar::{cal::Chinese, DateTime};
    ///
    /// let chinese = Chinese::new_always_calculating();
    ///
    /// let chinese_datetime =
    ///     DateTime::try_new_chinese_with_calendar(4660, 6, 11, 13, 1, 0, chinese)
    ///         .expect("Failed to initialize Chinese DateTime instance.");
    ///
    /// assert_eq!(chinese_datetime.date.year().era_year_or_extended(), 4660);
    /// assert_eq!(chinese_datetime.date.year().cyclic().unwrap().get(), 40);
    /// assert_eq!(chinese_datetime.date.month().ordinal, 6);
    /// assert_eq!(chinese_datetime.date.day_of_month().0, 11);
    /// assert_eq!(chinese_datetime.time.hour.number(), 13);
    /// assert_eq!(chinese_datetime.time.minute.number(), 1);
    /// assert_eq!(chinese_datetime.time.second.number(), 0);
    /// ```
    pub fn try_new_chinese_with_calendar(
        year: i32,
        month: u8,
        day: u8,
        hour: u8,
        minute: u8,
        second: u8,
        calendar: A,
    ) -> Result<DateTime<A>, DateError> {
        Ok(DateTime {
            date: Date::try_new_chinese_with_calendar(year, month, day, calendar)?,
            time: Time::try_new(hour, minute, second, 0)?,
        })
    }
}

type ChineseCB = calendrical_calculations::chinese_based::Chinese;
impl ChineseBasedWithDataLoading for Chinese {
    type CB = ChineseCB;
    fn get_precomputed_data(&self) -> ChineseBasedPrecomputedData<Self::CB> {
        ChineseBasedPrecomputedData::new(self.data.as_ref().map(|d| d.get()))
    }
}

impl Chinese {
    /// Get a YearInfo from an integer Chinese year; optionally, a `ChineseBasedYearInfo`
    /// can be passed in for faster results.
    fn format_chinese_year(
        year: i32,
        year_info_option: Option<ChineseBasedYearInfo>,
    ) -> types::YearInfo {
        let cyclic = (year - 1).rem_euclid(60) as u8;
        let cyclic = NonZeroU8::new(cyclic + 1).unwrap_or(NonZeroU8::MIN); // 1-indexed
        let rata_die_in_year = if let Some(info) = year_info_option {
            info.new_year::<ChineseCB>(year)
        } else {
            Inner::fixed_mid_year_from_year(year)
        };
        let iso_year = Iso::iso_from_fixed(rata_die_in_year).year();
        let related_iso = iso_year.era_year_or_extended();
        types::YearInfo::new_cyclic(year, cyclic, related_iso)
    }
}

#[cfg(test)]
mod test {

    use super::*;
    use crate::types::MonthCode;
    use calendrical_calculations::{iso::fixed_from_iso, rata_die::RataDie};
    /// Run a test twice, with two calendars
    fn do_twice(
        chinese_calculating: &Chinese,
        chinese_cached: &Chinese,
        test: impl Fn(crate::Ref<Chinese>, &'static str),
    ) {
        test(crate::Ref(chinese_calculating), "calculating");
        test(crate::Ref(chinese_cached), "cached");
    }

    #[test]
    fn test_chinese_from_fixed() {
        #[derive(Debug)]
        struct TestCase {
            fixed: i64,
            expected_year: i32,
            expected_month: u8,
            expected_day: u8,
        }

        let cases = [
            TestCase {
                fixed: -964192,
                expected_year: -2,
                expected_month: 1,
                expected_day: 1,
            },
            TestCase {
                fixed: -963838,
                expected_year: -1,
                expected_month: 1,
                expected_day: 1,
            },
            TestCase {
                fixed: -963129,
                expected_year: 0,
                expected_month: 13,
                expected_day: 1,
            },
            TestCase {
                fixed: -963100,
                expected_year: 0,
                expected_month: 13,
                expected_day: 30,
            },
            TestCase {
                fixed: -963099,
                expected_year: 1,
                expected_month: 1,
                expected_day: 1,
            },
            TestCase {
                fixed: 738700,
                expected_year: 4660,
                expected_month: 6,
                expected_day: 12,
            },
            TestCase {
                fixed: fixed_from_iso(2319, 2, 20).to_i64_date(),
                expected_year: 2319 + 2636,
                expected_month: 13,
                expected_day: 30,
            },
            TestCase {
                fixed: fixed_from_iso(2319, 2, 21).to_i64_date(),
                expected_year: 2319 + 2636 + 1,
                expected_month: 1,
                expected_day: 1,
            },
            TestCase {
                fixed: 738718,
                expected_year: 4660,
                expected_month: 6,
                expected_day: 30,
            },
            TestCase {
                fixed: 738747,
                expected_year: 4660,
                expected_month: 7,
                expected_day: 29,
            },
            TestCase {
                fixed: 738748,
                expected_year: 4660,
                expected_month: 8,
                expected_day: 1,
            },
            TestCase {
                fixed: 738865,
                expected_year: 4660,
                expected_month: 11,
                expected_day: 29,
            },
            TestCase {
                fixed: 738895,
                expected_year: 4660,
                expected_month: 12,
                expected_day: 29,
            },
            TestCase {
                fixed: 738925,
                expected_year: 4660,
                expected_month: 13,
                expected_day: 30,
            },
        ];

        let chinese_calculating = Chinese::new_always_calculating();
        let chinese_cached = Chinese::new();
        for case in cases {
            let rata_die = RataDie::new(case.fixed);
            let iso = Iso::iso_from_fixed(rata_die);

            do_twice(
                &chinese_calculating,
                &chinese_cached,
                |chinese, calendar_type| {
                    let chinese =
                        Inner::chinese_based_date_from_fixed(chinese.0, rata_die, iso.inner.0);
                    assert_eq!(
                        case.expected_year, chinese.0.year,
                        "[{calendar_type}] Chinese from fixed failed, case: {case:?}"
                    );
                    assert_eq!(
                        case.expected_month, chinese.0.month,
                        "[{calendar_type}] Chinese from fixed failed, case: {case:?}"
                    );
                    assert_eq!(
                        case.expected_day, chinese.0.day,
                        "[{calendar_type}] Chinese from fixed failed, case: {case:?}"
                    );
                },
            );
        }
    }

    #[test]
    fn test_fixed_from_chinese() {
        #[derive(Debug)]
        struct TestCase {
            year: i32,
            month: u8,
            day: u8,
            expected: i64,
        }

        let cases = [
            TestCase {
                year: 4660,
                month: 6,
                day: 6,
                // June 23 2023
                expected: 738694,
            },
            TestCase {
                year: 1,
                month: 1,
                day: 1,
                expected: -963099,
            },
        ];

        let chinese_calculating = Chinese::new_always_calculating();
        let chinese_cached = Chinese::new();
        for case in cases {
            do_twice(
                &chinese_calculating,
                &chinese_cached,
                |chinese, calendar_type| {
                    let date = Date::try_new_chinese_with_calendar(
                        case.year, case.month, case.day, chinese,
                    )
                    .unwrap();
                    let fixed =
                        Inner::fixed_from_chinese_based_date_inner(date.inner.0).to_i64_date();
                    let expected = case.expected;
                    assert_eq!(fixed, expected, "[{calendar_type}] Fixed from Chinese failed, with expected: {fixed} and calculated: {expected}, for test case: {case:?}");
                },
            );
        }
    }

    #[test]
    fn test_fixed_chinese_roundtrip() {
        let mut fixed = -1963020;
        let max_fixed = 1963020;
        let mut iters = 0;
        let max_iters = 560;
        let chinese_calculating = Chinese::new_always_calculating();
        let chinese_cached = Chinese::new();
        while fixed < max_fixed && iters < max_iters {
            let rata_die = RataDie::new(fixed);
            let iso = Iso::iso_from_fixed(rata_die);

            do_twice(
                &chinese_calculating,
                &chinese_cached,
                |chinese, calendar_type| {
                    let chinese =
                        Inner::chinese_based_date_from_fixed(&chinese, rata_die, iso.inner.0);
                    let result = Inner::fixed_from_chinese_based_date_inner(chinese);
                    let result_debug = result.to_i64_date();
                    assert_eq!(result, rata_die, "[{calendar_type}] Failed roundtrip fixed -> Chinese -> fixed for fixed: {fixed}, with calculated: {result_debug} from Chinese date:\n{chinese:?}");
                },
            );
            fixed += 7043;
            iters += 1;
        }
    }

    #[test]
    fn test_chinese_epoch() {
        let iso = Date::try_new_iso(-2636, 2, 15).unwrap();

        do_twice(
            &Chinese::new_always_calculating(),
            &Chinese::new(),
            |chinese, _calendar_type| {
                let chinese = iso.to_calendar(chinese);

                assert_eq!(chinese.year().era_year_or_extended(), 1);
                assert_eq!(chinese.month().ordinal, 1);
                assert_eq!(chinese.month().standard_code.0, "M01");
                assert_eq!(chinese.day_of_month().0, 1);
                assert_eq!(chinese.year().cyclic().unwrap().get(), 1);
                assert_eq!(chinese.year().related_iso(), Some(-2636));
            },
        )
    }

    #[test]
    fn test_iso_to_chinese_negative_years() {
        #[derive(Debug)]
        struct TestCase {
            iso_year: i32,
            iso_month: u8,
            iso_day: u8,
            expected_year: i32,
            expected_month: u8,
            expected_day: u8,
        }

        let cases = [
            TestCase {
                iso_year: -2636,
                iso_month: 2,
                iso_day: 14,
                expected_year: 0,
                expected_month: 13,
                expected_day: 30,
            },
            TestCase {
                iso_year: -2636,
                iso_month: 1,
                iso_day: 15,
                expected_year: 0,
                expected_month: 12,
                expected_day: 30,
            },
        ];

        let chinese_calculating = Chinese::new_always_calculating();
        let chinese_cached = Chinese::new();

        for case in cases {
            let iso = Date::try_new_iso(case.iso_year, case.iso_month, case.iso_day).unwrap();
            do_twice(
                &chinese_calculating,
                &chinese_cached,
                |chinese, calendar_type| {
                    let chinese = iso.to_calendar(chinese);
                    assert_eq!(
                        case.expected_year,
                        chinese.year().era_year_or_extended(),
                        "[{calendar_type}] ISO to Chinese failed for case: {case:?}"
                    );
                    assert_eq!(
                        case.expected_month,
                        chinese.month().ordinal,
                        "[{calendar_type}] ISO to Chinese failed for case: {case:?}"
                    );
                    assert_eq!(
                        case.expected_day,
                        chinese.day_of_month().0,
                        "[{calendar_type}] ISO to Chinese failed for case: {case:?}"
                    );
                },
            );
        }
    }

    #[test]
    fn test_chinese_leap_months() {
        let expected = [
            (1933, 6),
            (1938, 8),
            (1984, 11),
            (2009, 6),
            (2017, 7),
            (2028, 6),
        ];
        let chinese_calculating = Chinese::new_always_calculating();
        let chinese_cached = Chinese::new();

        for case in expected {
            let year = case.0;
            let expected_month = case.1;
            let iso = Date::try_new_iso(year, 6, 1).unwrap();
            do_twice(
                &chinese_calculating,
                &chinese_cached,
                |chinese, calendar_type| {
                    let chinese_date = iso.to_calendar(chinese);
                    assert!(
                        chinese_date.is_in_leap_year(),
                        "[{calendar_type}] {year} should be a leap year"
                    );
                    let new_year = chinese_date.inner.0.new_year();
                    assert_eq!(
                        expected_month,
                        calendrical_calculations::chinese_based::get_leap_month_from_new_year::<
                            calendrical_calculations::chinese_based::Chinese,
                        >(new_year),
                        "[{calendar_type}] {year} have leap month {expected_month}"
                    );
                },
            );
        }
    }

    #[test]
    fn test_month_days() {
        let year = 4660;
        let year_info =
            ChineseBasedPrecomputedData::<<Chinese as ChineseBasedWithDataLoading>::CB>::default()
                .load_or_compute_info(year);
        let cases = [
            (1, 29),
            (2, 30),
            (3, 29),
            (4, 29),
            (5, 30),
            (6, 30),
            (7, 29),
            (8, 30),
            (9, 30),
            (10, 29),
            (11, 30),
            (12, 29),
            (13, 30),
        ];
        for case in cases {
            let days_in_month = Chinese::month_days(year, case.0, year_info);
            assert_eq!(
                case.1, days_in_month,
                "month_days test failed for case: {case:?}"
            );
        }
    }

    #[test]
    fn test_ordinal_to_month_code() {
        #[derive(Debug)]
        struct TestCase {
            year: i32,
            month: u8,
            day: u8,
            expected_code: &'static str,
        }

        let cases = [
            TestCase {
                year: 2023,
                month: 1,
                day: 9,
                expected_code: "M12",
            },
            TestCase {
                year: 2023,
                month: 2,
                day: 9,
                expected_code: "M01",
            },
            TestCase {
                year: 2023,
                month: 3,
                day: 9,
                expected_code: "M02",
            },
            TestCase {
                year: 2023,
                month: 4,
                day: 9,
                expected_code: "M02L",
            },
            TestCase {
                year: 2023,
                month: 5,
                day: 9,
                expected_code: "M03",
            },
            TestCase {
                year: 2023,
                month: 6,
                day: 9,
                expected_code: "M04",
            },
            TestCase {
                year: 2023,
                month: 7,
                day: 9,
                expected_code: "M05",
            },
            TestCase {
                year: 2023,
                month: 8,
                day: 9,
                expected_code: "M06",
            },
            TestCase {
                year: 2023,
                month: 9,
                day: 9,
                expected_code: "M07",
            },
            TestCase {
                year: 2023,
                month: 10,
                day: 9,
                expected_code: "M08",
            },
            TestCase {
                year: 2023,
                month: 11,
                day: 9,
                expected_code: "M09",
            },
            TestCase {
                year: 2023,
                month: 12,
                day: 9,
                expected_code: "M10",
            },
            TestCase {
                year: 2024,
                month: 1,
                day: 9,
                expected_code: "M11",
            },
            TestCase {
                year: 2024,
                month: 2,
                day: 9,
                expected_code: "M12",
            },
            TestCase {
                year: 2024,
                month: 2,
                day: 10,
                expected_code: "M01",
            },
        ];

        let chinese_calculating = Chinese::new_always_calculating();
        let chinese_cached = Chinese::new();

        for case in cases {
            let iso = Date::try_new_iso(case.year, case.month, case.day).unwrap();
            do_twice(
                &chinese_calculating,
                &chinese_cached,
                |chinese, calendar_type| {
                    let chinese = iso.to_calendar(chinese);
                    let result_code = chinese.month().standard_code.0;
                    let expected_code = case.expected_code.to_string();
                    assert_eq!(
                        expected_code, result_code,
                        "[{calendar_type}] Month codes did not match for test case: {case:?}"
                    );
                },
            );
        }
    }

    #[test]
    fn test_month_code_to_ordinal() {
        let year = 4660;
        // construct using ::default() to force recomputation
        let year_info =
            ChineseBasedPrecomputedData::<<Chinese as ChineseBasedWithDataLoading>::CB>::default()
                .load_or_compute_info(year);
        let codes = [
            (1, tinystr!(4, "M01")),
            (2, tinystr!(4, "M02")),
            (3, tinystr!(4, "M02L")),
            (4, tinystr!(4, "M03")),
            (5, tinystr!(4, "M04")),
            (6, tinystr!(4, "M05")),
            (7, tinystr!(4, "M06")),
            (8, tinystr!(4, "M07")),
            (9, tinystr!(4, "M08")),
            (10, tinystr!(4, "M09")),
            (11, tinystr!(4, "M10")),
            (12, tinystr!(4, "M11")),
            (13, tinystr!(4, "M12")),
        ];
        for ordinal_code_pair in codes {
            let code = MonthCode(ordinal_code_pair.1);
            let ordinal = chinese_based_ordinal_lunar_month_from_code(code, year_info);
            assert_eq!(
                ordinal,
                Some(ordinal_code_pair.0),
                "Code to ordinal failed for year: {year}, code: {code}"
            );
        }
    }

    #[test]
    fn check_invalid_month_code_to_ordinal() {
        let non_leap_year = 4659;
        let leap_year = 4660;
        let invalid_codes = [
            (non_leap_year, tinystr!(4, "M2")),
            (leap_year, tinystr!(4, "M0")),
            (non_leap_year, tinystr!(4, "J01")),
            (leap_year, tinystr!(4, "3M")),
            (non_leap_year, tinystr!(4, "M04L")),
            (leap_year, tinystr!(4, "M04L")),
            (non_leap_year, tinystr!(4, "M13")),
            (leap_year, tinystr!(4, "M13")),
        ];
        for year_code_pair in invalid_codes {
            let year = year_code_pair.0;
            // construct using ::default() to force recomputation
            let year_info = ChineseBasedPrecomputedData::<
                <Chinese as ChineseBasedWithDataLoading>::CB,
            >::default()
            .load_or_compute_info(year);
            let code = MonthCode(year_code_pair.1);
            let ordinal = chinese_based_ordinal_lunar_month_from_code(code, year_info);
            assert_eq!(
                ordinal, None,
                "Invalid month code failed for year: {year}, code: {code}"
            );
        }
    }

    #[test]
    fn test_iso_chinese_roundtrip() {
        let chinese_calculating = Chinese::new_always_calculating();
        let chinese_cached = Chinese::new();

        for i in -1000..=1000 {
            let year = i;
            let month = i as u8 % 12 + 1;
            let day = i as u8 % 28 + 1;
            let iso = Date::try_new_iso(year, month, day).unwrap();
            do_twice(
                &chinese_calculating,
                &chinese_cached,
                |chinese, calendar_type| {
                    let chinese = iso.to_calendar(chinese);
                    let result = chinese.to_calendar(Iso);
                    assert_eq!(iso, result, "[{calendar_type}] ISO to Chinese roundtrip failed!\nIso: {iso:?}\nChinese: {chinese:?}\nResult: {result:?}");
                },
            );
        }
    }

    #[test]
    fn test_consistent_with_icu() {
        #[derive(Debug)]
        struct TestCase {
            iso_year: i32,
            iso_month: u8,
            iso_day: u8,
            expected_rel_iso: i32,
            expected_cyclic: u8,
            expected_month: u8,
            expected_day: u8,
        }

        let cases = [
            TestCase {
                iso_year: -2332,
                iso_month: 3,
                iso_day: 1,
                expected_rel_iso: -2332,
                expected_cyclic: 5,
                expected_month: 1,
                expected_day: 16,
            },
            TestCase {
                iso_year: -2332,
                iso_month: 2,
                iso_day: 15,
                expected_rel_iso: -2332,
                expected_cyclic: 5,
                expected_month: 1,
                expected_day: 1,
            },
            TestCase {
                // This test case fails to match ICU
                iso_year: -2332,
                iso_month: 2,
                iso_day: 14,
                expected_rel_iso: -2333,
                expected_cyclic: 4,
                expected_month: 13,
                expected_day: 30,
            },
            TestCase {
                // This test case fails to match ICU
                iso_year: -2332,
                iso_month: 1,
                iso_day: 17,
                expected_rel_iso: -2333,
                expected_cyclic: 4,
                expected_month: 13,
                expected_day: 2,
            },
            TestCase {
                // This test case fails to match ICU
                iso_year: -2332,
                iso_month: 1,
                iso_day: 16,
                expected_rel_iso: -2333,
                expected_cyclic: 4,
                expected_month: 13,
                expected_day: 1,
            },
            TestCase {
                iso_year: -2332,
                iso_month: 1,
                iso_day: 15,
                expected_rel_iso: -2333,
                expected_cyclic: 4,
                expected_month: 12,
                expected_day: 29,
            },
            TestCase {
                iso_year: -2332,
                iso_month: 1,
                iso_day: 1,
                expected_rel_iso: -2333,
                expected_cyclic: 4,
                expected_month: 12,
                expected_day: 15,
            },
            TestCase {
                iso_year: -2333,
                iso_month: 1,
                iso_day: 16,
                expected_rel_iso: -2334,
                expected_cyclic: 3,
                expected_month: 12,
                expected_day: 19,
            },
        ];

        let chinese_calculating = Chinese::new_always_calculating();
        let chinese_cached = Chinese::new();

        for case in cases {
            let iso = Date::try_new_iso(case.iso_year, case.iso_month, case.iso_day).unwrap();

            do_twice(
                &chinese_calculating,
                &chinese_cached,
                |chinese, calendar_type| {
                    let chinese = iso.to_calendar(chinese);
                    let chinese_rel_iso = chinese.year().related_iso();
                    let chinese_cyclic = chinese.year().cyclic();
                    let chinese_month = chinese.month().ordinal;
                    let chinese_day = chinese.day_of_month().0;

                    assert_eq!(
                        chinese_rel_iso,
                        Some(case.expected_rel_iso),
                        "[{calendar_type}] Related ISO failed for test case: {case:?}"
                    );
                    assert_eq!(
                        chinese_cyclic.unwrap().get(),
                        case.expected_cyclic,
                        "[{calendar_type}] Cyclic year failed for test case: {case:?}"
                    );
                    assert_eq!(
                        chinese_month, case.expected_month,
                        "[{calendar_type}] Month failed for test case: {case:?}"
                    );
                    assert_eq!(
                        chinese_day, case.expected_day,
                        "[{calendar_type}] Day failed for test case: {case:?}"
                    );
                },
            );
        }
    }
}