use super::{SolarYear, HeavenlyStems, EarthlyBranch, Zodiac, LunarYear, LunarMonth, LEAP_MONTHS, BIG_MONTHS, MIN_YEAR_IN_SOLAR_CALENDAR, MAX_YEAR_IN_SOLAR_CALENDAR};

use std::fmt::{self, Display, Formatter};

/// 農曆西曆年，農曆新年所在的西曆年份。
#[derive(Debug, PartialOrd, Ord, PartialEq, Clone, Eq, Hash, Copy)]
pub struct LunisolarYear {
    solar_year: SolarYear,
}

impl LunisolarYear {
    /// 透過西曆年份來取得 `LunisolarYear` 實體。
    pub unsafe fn from_solar_year_unsafe<Y: Into<SolarYear>>(solar_year: Y) -> LunisolarYear {
        let solar_year = solar_year.into();

        LunisolarYear {
            solar_year
        }
    }

    /// 透過西曆年份來取得 `LunisolarYear` 實體。
    pub fn from_solar_year<Y: Into<SolarYear>>(solar_year: Y) -> Option<LunisolarYear> {
        let solar_year = solar_year.into();

        let year = solar_year.to_u16();

        if year >= MIN_YEAR_IN_SOLAR_CALENDAR && year <= MAX_YEAR_IN_SOLAR_CALENDAR {
            Some(LunisolarYear {
                solar_year
            })
        } else {
            None
        }
    }

    /// 取得此西曆年中，農曆新年的中國天干。
    pub fn get_heavenly_stems(&self) -> HeavenlyStems {
        let index = (7 + (self.solar_year.to_u16() - MIN_YEAR_IN_SOLAR_CALENDAR)) % 10;

        unsafe {
            HeavenlyStems::from_ordinal_unsafe(index as i8)
        }
    }

    /// 取得此西曆年中，農曆新年的中國地支。
    pub fn get_earthly_branch(&self) -> EarthlyBranch {
        let index = (self.solar_year.to_u16() - MIN_YEAR_IN_SOLAR_CALENDAR + 1) % 12;

        unsafe {
            EarthlyBranch::from_ordinal_unsafe(index as i8)
        }
    }

    /// 取得此西曆年中，農曆新年所屬的生肖。
    pub fn get_zodiac(&self) -> Zodiac {
        let index = (self.solar_year.to_u16() - MIN_YEAR_IN_SOLAR_CALENDAR + 1) % 12;

        unsafe {
            Zodiac::from_ordinal_unsafe(index as i8)
        }
    }

    /// 取得此年的農曆閏月月份。
    pub fn get_leap_lunar_month(&self) -> Option<LunarMonth> {
        let year = self.to_u16();

        let month = LEAP_MONTHS[((year - MIN_YEAR_IN_SOLAR_CALENDAR) / 2) as usize];

        let index = if year % 2 == 1 {
            ((month & 0xf0) >> 4)
        } else {
            (month & 0x0f)
        };

        if index == 0 {
            None
        } else {
            Some(unsafe {
                LunarMonth::from_u8_unsafe(index, true)
            })
        }
    }

    /// 計算此西曆年下的農曆閏月共有幾天。如果沒有閏月，則回傳0。
    pub fn get_total_days_in_leap_month(&self) -> u16 {
        let leap_lunar_month = self.get_leap_lunar_month();

        match leap_lunar_month {
            Some(leap_lunar_month) => {
                self.get_total_days_in_leap_month_inner(leap_lunar_month)
            }
            None => 0
        }
    }

    /// 計算指定的農曆閏月共有幾天。
    pub(crate) fn get_total_days_in_leap_month_inner(&self, leap_lunar_month: LunarMonth) -> u16 {
        let year = self.to_u16();

        let leap_month = leap_lunar_month.to_u8();

        if (BIG_MONTHS[(year - MIN_YEAR_IN_SOLAR_CALENDAR) as usize] & (0x8000 >> leap_month)) == 0 {
            29
        } else {
            30
        }
    }

    /// 計算此西曆年下的農曆年共有幾天。。
    pub fn get_total_days(&self) -> u16 {
        let leap_lunar_month = self.get_leap_lunar_month();

        let (leap_month, mut n) = match leap_lunar_month {
            Some(leap_lunar_month) => {
                (leap_lunar_month.to_u8(), self.get_total_days_in_leap_month_inner(leap_lunar_month))
            }
            None => (0, 0)
        };

        let year = self.to_u16();

        if leap_month > 0 {
            for month in 1..=leap_month {
                if (BIG_MONTHS[(year - MIN_YEAR_IN_SOLAR_CALENDAR) as usize] & (0x8000 >> (month - 1))) == 0 {
                    n += 29;
                } else {
                    n += 30;
                }
            }

            for month in (leap_month + 1)..=12 {
                if (BIG_MONTHS[(year - MIN_YEAR_IN_SOLAR_CALENDAR) as usize] & (0x8000 >> month)) == 0 {
                    n += 29;
                } else {
                    n += 30;
                }
            }
        } else {
            for month in 1..=12 {
                if (BIG_MONTHS[(year - MIN_YEAR_IN_SOLAR_CALENDAR) as usize] & (0x8000 >> (month - 1))) == 0 {
                    n += 29;
                } else {
                    n += 30;
                }
            }
        }

        n
    }

    /// 計算此西曆年下的農曆年的某個月共有幾天。。
    pub fn get_total_days_in_a_month(&self, lunar_month: LunarMonth) -> Option<u8> {
        lunar_month.get_total_days(*self)
    }

    /// 取得 `LunarYear` 實體。
    pub fn to_lunar_year(&self) -> LunarYear {
        let heavenly_stems = self.get_heavenly_stems();
        let earthly_branch = self.get_earthly_branch();

        LunarYear::from_era(heavenly_stems, earthly_branch)
    }

    /// 取得 `SolarYear` 實體。
    pub fn to_solar_year(&self) -> SolarYear {
        self.solar_year
    }

    /// 取得 `LunisolarYear` 實體所代表的西曆年份數值。
    pub fn to_u16(&self) -> u16 {
        self.solar_year.to_u16()
    }
}

impl Display for LunisolarYear {
    fn fmt(&self, f: &mut Formatter) -> Result<(), fmt::Error> {
        Display::fmt(&self.solar_year, f)
    }
}