// This Source Code Form is subject to the terms of the Mozilla Public

// License, v. 2.0. If a copy of the MPL was not distributed with this

// file, You can obtain one at https://mozilla.org/MPL/2.0/.

use crate::calendar::julian::Julian;

use crate::calendar::prelude::CommonDate;

use crate::calendar::prelude::CommonWeekOfYear;

use crate::calendar::prelude::GuaranteedMonth;

use crate::calendar::prelude::HasLeapYears;

use crate::calendar::prelude::Quarter;

use crate::calendar::prelude::ToFromCommonDate;

use crate::calendar::AllowYearZero;

use crate::calendar::CalendarMoment;

use crate::calendar::OrdinalDate;

use crate::calendar::ToFromOrdinalDate;

use crate::common::error::CalendarError;

use crate::common::math::TermNum;

use crate::day_count::BoundedDayCount;

use crate::day_count::CalculatedBounds;

use crate::day_count::Epoch;

use crate::day_count::Fixed;

use crate::day_count::FromFixed;

use crate::day_count::ToFixed;

#[allow(unused_imports)] //FromPrimitive is needed for derive

use num_traits::FromPrimitive;

use std::num::NonZero;

//TODO: Coptic weekdays

//LISTING 4.1 (*Calendrical Calculations: The Ultimate Edition* by Reingold & Dershowitz.)

const COPTIC_EPOCH_JULIAN: CommonDate = CommonDate {

    year: 284,

    month: 8,

    day: 29,

};

/// Represents a month in the Coptic Calendar

#[derive(Debug, PartialEq, PartialOrd, Clone, Copy, FromPrimitive, ToPrimitive)]

pub enum CopticMonth {

    //LISTING ?? SECTION 4.1 (*Calendrical Calculations: The Ultimate Edition* by Reingold & Dershowitz.)

    Thoout = 1,

    Paope,

    Athor,

    Koiak,

    Tobe,

    Meshir,

    Paremotep,

    Parmoute,

    Pashons,

    Paone,

    Epep,

    Mesore,

    Epagomene,

}

/// Represents a date in the Coptic calendar

///

/// ## Introduction

///

/// The Coptic calendar (also called the Alexandrian calendar or the Calendar of Martyrs)

/// is used by the Coptic Orthodox Church and the Coptic Catholic Church. Historically it

/// was also used for fiscal purposes in Egypt.

///

/// ## Basic Structure

///

/// Years are divided into 13 months. The first 12 months have 30 days each. The final month

/// has 5 days in a common year and 6 days in a leap year.

///

/// There is 1 leap year every four years. This leap year occurs *before* the Julian leap year.

/// In other words, if a given year is divisible by 4, the year *before* was a leap year.

///

/// ## Epoch

///

/// Years are numbered from the start of the reign of the Roman Emperor Diocletian. Each

/// individual year starts on the Feast of Neyrouz. Thus the first year of the Coptic calendar

/// began on 29 August 284 AD of the Julian calendar.

///

/// This epoch is called the Era of the Martyrs.

///

/// ## Representation and Examples

///

/// The months are represented in this crate as [`CopticMonth`].

///

/// ```

/// use radnelac::calendar::*;

/// use radnelac::day_count::*;

///

/// let c_1_1 = CommonDate::new(1741, 1, 1);

/// let a_1_1 = Coptic::try_from_common_date(c_1_1).unwrap();

/// assert_eq!(a_1_1.month(), CopticMonth::Thoout);

/// let c_12_30 = CommonDate::new(1741, 12, 30);

/// let a_12_30 = Coptic::try_from_common_date(c_12_30).unwrap();

/// assert_eq!(a_12_30.month(), CopticMonth::Mesore);

/// ```

///

/// The start of the Era of Martyrs can be read programatically.

///

/// ```

/// use radnelac::calendar::*;

/// use radnelac::day_count::*;

///

/// let e = Coptic::epoch();

/// let j = Julian::from_fixed(e);

/// let c = Coptic::from_fixed(e);

/// assert_eq!(j.year(), 284);

/// assert_eq!(j.month(), JulianMonth::August);

/// assert_eq!(j.day(), 29);

/// assert_eq!(c.year(), 1);

/// assert_eq!(c.month(), CopticMonth::Thoout);

/// assert_eq!(c.day(), 1);

/// ```

///

/// ## Further reading

/// + Wikipedia

///   + [Coptic Calendar](https://en.wikipedia.org/wiki/Coptic_calendar)

///   + [Era of the Martyrs](https://en.wikipedia.org/wiki/Era_of_the_Martyrs)

/// + [Coptic Orthodox Church](https://copticorthodox.church/en/coptic-church/coptic-history/)

/// + [*The Coptic Christian Heritage* by Lois M. Farag](https://www.google.ca/books/edition/The_Coptic_Christian_Heritage/dYK3AQAAQBAJ)

/// + [*A Handbook for Travellers in Lower and_Upper Egypt*](https://www.google.ca/books/edition/A_Handbook_for_Travellers_in_Lower_and_U/CnhJYhBzMmgC?hl=en&gbpv=1)

#[derive(Debug, PartialEq, PartialOrd, Clone, Copy)]

pub struct Coptic(CommonDate);

impl AllowYearZero for Coptic {}

impl ToFromOrdinalDate for Coptic {

    fn valid_ordinal(ord: OrdinalDate) -> Result<(), CalendarError> {

        let correction = if Coptic::is_leap(ord.year) { 
1328
 } else { 
0952
 };

        if ord.day_of_year > 0 && 
ord.day_of_year <= (365 + correction)1.02k
 {

            Ok(())

        } else {

            Err(CalendarError::InvalidDayOfYear)

        }

    }

    fn ordinal_from_fixed(fixed_date: Fixed) -> OrdinalDate {

        //LISTING 4.4 (*Calendrical Calculations: The Ultimate Edition* by Reingold & Dershowitz.)

        //Missing the day term and parts of the month term

        let date = fixed_date.get_day_i();

        let epoch = Coptic::epoch().get_day_i();

        let year = (4 * (date - epoch) + 1463).div_euclid(1461) as i32;

        let year_start = Coptic::to_fixed(Coptic(CommonDate::new(year, 1, 1)));

        let doy = ((date - year_start.get_day_i()) + 1) as u16;

        OrdinalDate {

            year: year,

            day_of_year: doy,

        }

    }

    fn to_ordinal(self) -> OrdinalDate {

        //LISTING 4.3 (*Calendrical Calculations: The Ultimate Edition* by Reingold & Dershowitz.)

        //This is just the terms containing monthand day

        OrdinalDate {

            year: self.0.year,

            day_of_year: (30 * ((self.0.month as u16) - 1) + (self.0.day as u16)),

        }

    }

    fn from_ordinal_unchecked(ord: OrdinalDate) -> Self {

        //LISTING 4.4 (*Calendrical Calculations: The Ultimate Edition* by Reingold & Dershowitz.)

        //Only the month and day terms, modified to use ordinal day count instead of count from epoch

        let month = ((ord.day_of_year - 1).div_euclid(30) + 1) as u8;

        let month_start = Coptic(CommonDate::new(ord.year, month, 1)).to_ordinal();

        let day = (ord.day_of_year - month_start.day_of_year + 1) as u8;

        Coptic(CommonDate::new(ord.year, month, day))

    }

}

impl HasLeapYears for Coptic {

    //LISTING 4.2 (*Calendrical Calculations: The Ultimate Edition* by Reingold & Dershowitz.)

    fn is_leap(year: i32) -> bool {

        year.modulus(4) == 3

    }

}

impl CalculatedBounds for Coptic {}

impl Epoch for Coptic {

    fn epoch() -> Fixed {

        Julian::try_from_common_date(COPTIC_EPOCH_JULIAN)

            .expect("Epoch known to be in range.")

            .to_fixed()

    }

}

impl FromFixed for Coptic {

    fn from_fixed(fixed_date: Fixed) -> Coptic {

        //LISTING 4.4 (*Calendrical Calculations: The Ultimate Edition* by Reingold & Dershowitz.)

        //Split compared to original

        let ord = Self::ordinal_from_fixed(fixed_date);

        Self::from_ordinal_unchecked(ord)

    }

}

impl ToFixed for Coptic {

    fn to_fixed(self) -> Fixed {

        //LISTING 4.3 (*Calendrical Calculations: The Ultimate Edition* by Reingold & Dershowitz.)

        //Split compared to original: the terms containing month and day are in to_ordinal

        let year = self.0.year as i64;

        let epoch = Coptic::epoch().get_day_i();

        let doy = self.to_ordinal().day_of_year as i64;

        Fixed::cast_new(epoch - 1 + (365 * (year - 1)) + year.div_euclid(4) + doy)

    }

}

impl ToFromCommonDate<CopticMonth> for Coptic {

    fn to_common_date(self) -> CommonDate {

        self.0

    }

    fn from_common_date_unchecked(date: CommonDate) -> Self {

        debug_assert!(Self::valid_ymd(date).is_ok());

        Self(date)

    }

    fn valid_ymd(date: CommonDate) -> Result<(), CalendarError> {

        let month_opt = CopticMonth::from_u8(date.month);

        if month_opt.is_none() {

            Err(CalendarError::InvalidMonth)

        } else if date.day < 1 {

            Err(CalendarError::InvalidDay)

        } else if date.day > Self::month_length(date.year, month_opt.unwrap()) {

            Err(CalendarError::InvalidDay)

        } else {

            Ok(())

        }

    }

    fn year_end_date(year: i32) -> CommonDate {

        let m = CopticMonth::Epagomene;

        CommonDate::new(year, m as u8, Self::month_length(year, m))

    }

    fn month_length(year: i32, month: CopticMonth) -> u8 {

        //LISTING ?? SECTION 4.1 (*Calendrical Calculations: The Ultimate Edition* by Reingold & Dershowitz.)

        match (month, Coptic::is_leap(year)) {

            (CopticMonth::Epagomene, false) => 5,

            (CopticMonth::Epagomene, true) => 6,

            (_, _) => 30,

        }

    }

}

impl Quarter for Coptic {

    fn quarter(self) -> NonZero<u8> {

        if self.month() == CopticMonth::Epagomene {

            NonZero::new(4 as u8).expect("4 != 0")

        } else {

            NonZero::new((((self.month() as u8) - 1) / 3) + 1).expect("(m-1)/3 > -1")

        }

    }

}

impl GuaranteedMonth<CopticMonth> for Coptic {}

impl CommonWeekOfYear<CopticMonth> for Coptic {}

/// Represents a date *and time* in the Coptic Calendar

pub type CopticMoment = CalendarMoment<Coptic>;

#[cfg(test)]

mod tests {

    use super::*;

    use crate::calendar::julian::JulianMonth;

    use crate::calendar::Gregorian;

    use proptest::prop_assume;

    use proptest::proptest;

    #[test]

    fn handbook() {

        //https://www.google.ca/books/edition/A_Handbook_for_Travellers_in_Lower_and_U/CnhJYhBzMmgC?hl=en&gbpv=1

        let c = Coptic::try_from_common_date(CommonDate::new(1604, 1, 1)).unwrap();

        let g = c.convert::<Gregorian>();

        assert_eq!(g.to_common_date(), CommonDate::new(1887, 9, 11));

    }

    proptest! {

        #[test]

        fn julian_leap_ad(x in 1..(i16::MAX/4)) {

            let jy: i32 = (x * 4) as i32;

            prop_assume!(Julian::is_leap(jy));

            let j = Julian::try_from_common_date(CommonDate::new(jy, 1, 1)).unwrap();

            let c = j.convert::<Coptic>();

            assert!(!Coptic::is_leap(c.year()));

            assert!(Coptic::is_leap(c.year() - 1));

        }

        #[test]

        fn christmas(y in i16::MIN..i16::MAX) {

            //LISTING 4.9 (*Calendrical Calculations: The Ultimate Edition* by Reingold & Dershowitz.)

            let c = Coptic::try_from_common_date(CommonDate::new(y as i32, CopticMonth::Koiak as u8, 29))?;

            let j = c.convert::<Julian>();

            assert_eq!(j.month(), JulianMonth::December);

            assert!(j.day() == 25 || j.day() == 26);

        }

        #[test]

        fn feast_of_neyrouz(y in i16::MIN..i16::MAX) {

            // https://en.wikipedia.org/wiki/Coptic_calendar

            let c = Coptic::try_from_common_date(CommonDate::new(y as i32, CopticMonth::Thoout as u8, 1))?;

            let j = c.convert::<Julian>();

            assert_eq!(j.month(), JulianMonth::August);

            assert!(j.day() == 29 || j.day() == 30);

        }

    }

}