// 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::prelude::CommonDate;

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

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

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

use crate::calendar::AllowYearZero;

use crate::calendar::CalendarMoment;

use crate::calendar::HasEpagemonae;

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::JulianDay;

use crate::day_count::ToFixed;

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

use num_traits::FromPrimitive;

use std::num::NonZero;

//LISTING 1.46 (*Calendrical Calculations: The Ultimate Edition* by Reingold & Dershowitz.)

const NABONASSAR_ERA_JD: i32 = 1448638;

const NON_MONTH: u8 = 13;

/// Represents a month in the Egyptian Calendar

///

/// Note that the epagomenal days at the end of the Egyptian calendar year have no

/// month and thus are not represented by ArmenianMonth. When representing an

/// arbitrary day in the Egyptian calendar, use an `Option<EgyptianMonth>` for the

/// the month field.

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

pub enum EgyptianMonth {

    //LISTING ?? SECTION 1.11 (*Calendrical Calculations: The Ultimate Edition* by Reingold & Dershowitz.)

    Thoth = 1,

    Phaophi,

    Athyr,

    Choiak,

    Tybi,

    Mechir,

    Phamenoth,

    Pharmuthi,

    Pachon,

    Payni,

    Epiphi,

    Mesori,

}

/// Represents an epagomenal day at the end of the Egyptian calendar year

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

pub enum EgyptianDaysUponTheYear {

    BirthOfOsiris = 1,

    BirthOfHorus,

    BirthOfSeth,

    BirthOfIsis,

    BirthOfNephthys,

}

/// Represents a date in the Egyptian calendar

///

/// ## Introduction

///

/// The Egyptian calendar was used in ancient Egypt.

///

/// ## Basic Structure

///

/// Years are always 365 days - there are no leap years. Years are divided into 12 months

/// of 30 days each, with an extra 5 epagomenal days.

///

/// ## Epoch

///

/// This implementation of the Egyptian calendar uses the Nabonassar Era from the *Almagest*

/// written by Claudius Ptolomy. The first year of the Nabonassar Era began on 26 Februrary

/// 747 BC of the Julian calendar.

///

/// The *Almagest* was written in Greek, and Nabonassar was a Babylonian king instead of an

/// Egyptian. The actual calendar dates in Ancient Egypt used regnal years.

///

/// ## Representation and Examples

///

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

///

/// ```

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

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

///

/// let c_1_1 = CommonDate::new(1462, 1, 1);

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

/// assert_eq!(a_1_1.try_month().unwrap(), EgyptianMonth::Thoth);

/// let c_12_30 = CommonDate::new(1462, 12, 30);

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

/// assert_eq!(a_12_30.try_month().unwrap(), EgyptianMonth::Mesori);

/// ```

///

/// When converting to and from a [`CommonDate`](crate::calendar::CommonDate), the epagomenal days

/// are treated as a 13th month.

///

/// ```

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

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

///

/// let c = CommonDate::new(1462, 13, 5);

/// let a = Egyptian::try_from_common_date(c).unwrap();

/// assert!(a.try_month().is_none());

/// assert!(a.epagomenae().is_some());

/// ```

///

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

///

/// ```

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

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

///

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

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

/// let a = Egyptian::from_fixed(e);

/// assert_eq!(j.year(), -747);

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

/// assert_eq!(j.day(), 26);

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

/// assert_eq!(a.try_month().unwrap(), EgyptianMonth::Thoth);

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

/// ```

///

/// ## Further reading

/// + Wikipedia

///   + [Egyptian Calendar](https://en.wikipedia.org/wiki/Egyptian_calendar)

///   + [Nabonassar](https://en.wikipedia.org/wiki/Nabonassar)

///   + [Egyptian chronology](https://en.wikipedia.org/wiki/Egyptian_chronology)

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

pub struct Egyptian(CommonDate);

impl AllowYearZero for Egyptian {}

impl ToFromOrdinalDate for Egyptian {

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

        if ord.day_of_year < 1 || 
ord.day_of_year > 3651.53k
 {

            Err(CalendarError::InvalidDayOfYear)

        } else {

            Ok(())

        }

    }

    fn ordinal_from_fixed(fixed_date: Fixed) -> OrdinalDate {

        let days = fixed_date.get_day_i() - Egyptian::epoch().get_day_i();

        let year = (days.div_euclid(365) + 1) as i32;

        let doy = (days.modulus(365) + 1) as u16;

        OrdinalDate {

            year: year,

            day_of_year: doy,

        }

    }

    fn to_ordinal(self) -> OrdinalDate {

        let month = self.0.month as i64;

        let day = self.0.day as i64;

        let offset = ((30 * (month - 1)) + day) as u16;

        OrdinalDate {

            year: self.0.year,

            day_of_year: offset,

        }

    }

    fn from_ordinal_unchecked(ord: OrdinalDate) -> Self {

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

        let day = ord.day_of_year - (30 * (month - 1));

        Egyptian(CommonDate::new(ord.year, month as u8, day as u8))

    }

}

impl CalculatedBounds for Egyptian {}

impl Epoch for Egyptian {

    fn epoch() -> Fixed {

        JulianDay::new(NABONASSAR_ERA_JD as f64).to_fixed()

    }

}

impl FromFixed for Egyptian {

    fn from_fixed(date: Fixed) -> Egyptian {

        //LISTING 1.49 (*Calendrical Calculations: The Ultimate Edition* by Reingold & Dershowitz.)

        let days = date.get_day_i() - Egyptian::epoch().get_day_i();

        let year = days.div_euclid(365) + 1;

        let month = days.modulus(365).div_euclid(30) + 1;

        let day = days - (365 * (year - 1)) - (30 * (month - 1)) + 1;

        Egyptian(CommonDate {

            year: year as i32,

            month: month as u8,

            day: day as u8,

        })

    }

}

impl ToFixed for Egyptian {

    fn to_fixed(self) -> Fixed {

        //LISTING 1.47 (*Calendrical Calculations: The Ultimate Edition* by Reingold & Dershowitz.)

        let year = self.0.year as i64;

        let month = self.0.month as i64;

        let day = self.0.day as i64;

        let offset = (365 * (year - 1)) + (30 * (month - 1)) + day - 1;

        Fixed::cast_new(Egyptian::epoch().get_day_i() + offset)

    }

}

impl ToFromCommonDate<EgyptianMonth> for Egyptian {

    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> {

        if date.month < 1 || 
date.month > NON_MONTH63.5k
 {

            Err(CalendarError::InvalidMonth)

        } else if date.day < 1 {

            Err(CalendarError::InvalidDay)

        } else if date.month < NON_MONTH && 
date.day > 3053.5k
 {

            Err(CalendarError::InvalidDay)

        } else if date.month == NON_MONTH && 
date.day > 58.43k
 {

            Err(CalendarError::InvalidDay)

        } else {

            Ok(())

        }

    }

    fn year_end_date(year: i32) -> CommonDate {

        CommonDate::new(year, NON_MONTH, 5)

    }

    fn month_length(_year: i32, _month: EgyptianMonth) -> u8 {

        30

    }

}

impl HasEpagemonae<EgyptianDaysUponTheYear> for Egyptian {

    fn epagomenae(self) -> Option<EgyptianDaysUponTheYear> {

        if self.0.month == NON_MONTH {

            EgyptianDaysUponTheYear::from_u8(self.0.day)

        } else {

            None

        }

    }

    fn epagomenae_count(_year: i32) -> u8 {

        5

    }

}

impl Quarter for Egyptian {

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

        let m = self.to_common_date().month as u8;

        if m == NON_MONTH {

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

        } else {

            NonZero::new(((m - 1) / 3) + 1).expect("(m - 1) / 3 > -1")

        }

    }

}

impl CommonWeekOfYear<EgyptianMonth> for Egyptian {}

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

pub type EgyptianMoment = CalendarMoment<Egyptian>;