// 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/.

// Calendier Positiviste Page 52-53

use crate::calendar::gregorian::Gregorian;

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

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

use crate::calendar::prelude::Perennial;

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

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

use crate::calendar::prelude::ToFromOrdinalDate;

use crate::calendar::AllowYearZero;

use crate::calendar::CalendarMoment;

use crate::calendar::HasEpagemonae;

use crate::calendar::OrdinalDate;

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;

use crate::day_cycle::Weekday;

use std::num::NonZero;

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

use num_traits::FromPrimitive;

const POSITIVIST_YEAR_OFFSET: i32 = 1789 - 1;

const NON_MONTH: u8 = 14;

/// Represents a month of the Positivist Calendar

///

/// The Positivist months are named after famous historical figures.

///

/// Note that the complementary days at the end of the Positivist calendar year have no

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

/// arbitrary day in the Positivist calendar, use an `Option<PositivistMonth>` for the

/// the month field.

///

/// See page 19 of "Calendier Positiviste" for more details.

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

pub enum PositivistMonth {

    Moses = 1,

    Homer,

    Aristotle,

    Archimedes,

    Caesar,

    SaintPaul,

    Charlemagne,

    Dante,

    Gutenburg,

    Shakespeare,

    Descartes,

    Frederick,

    Bichat,

}

/// Represents a complementary day of the Positivist Calendar

///

/// These are not part of any week or month.

/// See page 8 of "Calendier Positiviste" for more details.

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

pub enum PositivistComplementaryDay {

    /// In leap years of the Positivist calendar, this is the second-last day of the year.

    /// In common years of the Positivist calendar, this is the last day of the year.

    FestivalOfTheDead = 1,

    /// In leap years of the Positivist calendar, this is the last day of the year.

    FestivalOfHolyWomen,

}

/// Represents a date in the Positivist calendar

///

/// ## Introduction

///

/// The Positivist calendar was proposed by August Comte. It was part of his project of

/// creating a "Religion of Humanity". The months, weeks and days of the Positivist

/// calendar are named after people who made a positive (as judged by Comte) contributions

/// to society.

///

/// ## Basic structure

///

/// From *The Positivist Calendar* by Henry Edger:

/// > The Positivist year, beginning and ending with the Christian year, is divided into

/// > thirteen months, and an additional day in bisextile years, following that. To these

/// > two days no name, either weekly or monthly, is attached, being sufficiently

/// > designated by the corresponding festivals. The Calendar therefore becomes perpetual.

/// > Every year, and each month in the year, begins with a Monday, while the Sundays fall

/// > on the 7th, 14th 21st and 28th days of all the months alike.

///

/// The "bisextile" (leap) years must occur at the same time as Gregorian leap years based

/// on the above definition. This further implies a leap year rule similar to the Gregorian,

/// but offset by 1788 years.

///

/// ## Epoch

///

/// The years are numbered based on the French Revolution. The first day of the first year

/// of the Positivist calendar occurs on 1 January 1789 Common Era of the Gregorian calendar.

///

/// When using this epoch, years are named "of the Great Revolution" or "of the Great Crisis".

/// For example, 1855 Common Era in the Gregorian calendar is 67 of the Great Revolution in the

/// Positivist calendar.

///

/// ## Representation and Examples

///

/// ### Months

///

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

///

/// ```

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

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

///

/// let c_1_1 = CommonDate::new(67, 1, 1);

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

/// assert_eq!(a_1_1.try_month().unwrap(), PositivistMonth::Moses);

/// ```

///

/// ### Weekdays

///

/// The days of the Positivist week are not always the same as the days of the common week.

///

/// ```

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

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

/// use radnelac::day_cycle::*;

///

/// let c = CommonDate::new(66, 13, 28);

/// let p = Positivist::try_from_common_date(c).unwrap();

/// assert_eq!(p.weekday().unwrap(), Weekday::Sunday); //Positivist week

/// assert_eq!(p.convert::<Weekday>(), Weekday::Saturday); //Common week

/// ```

///

/// ### Festivals Ending the Year

///

/// The epagomenal festival days at the end of a Positivist year are represented as

/// [`PositivistComplementaryDay`]. When converting to and from a [`CommonDate`](crate::calendar::CommonDate),

/// the epagomenal days are treated as a 14th month.

///

/// ```

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

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

///

/// let c = CommonDate::new(67, 14, 1);

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

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

/// assert_eq!(a.epagomenae().unwrap(), PositivistComplementaryDay::FestivalOfTheDead);

/// ```

///

/// ## Further reading

/// + [Positivists.org](http://positivists.org/calendar.html)

/// + [*Calendrier Positiviste* by August Comte](https://gallica.bnf.fr/ark:/12148/bpt6k21868f/f42.planchecontact)

/// + [*The Positivist Calendar* by Henry Edger](https://books.google.ca/books?id=S_BRAAAAMAAJ)

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

pub struct Positivist(CommonDate);

impl AllowYearZero for Positivist {}

impl ToFromOrdinalDate for Positivist {

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

        let ord_g = OrdinalDate {

            year: ord.year + POSITIVIST_YEAR_OFFSET,

            day_of_year: ord.day_of_year,

        };

        Gregorian::valid_ordinal(ord_g)

    }

    fn ordinal_from_fixed(fixed_date: Fixed) -> OrdinalDate {

        let ord_g = Gregorian::ordinal_from_fixed(fixed_date);

        OrdinalDate {

            year: ord_g.year - POSITIVIST_YEAR_OFFSET,

            day_of_year: ord_g.day_of_year,

        }

    }

    fn to_ordinal(self) -> OrdinalDate {

        let offset_m = ((self.0.month as i64) - 1) * 28;

        let doy = (offset_m as u16) + (self.0.day as u16);

        OrdinalDate {

            year: self.0.year,

            day_of_year: doy,

        }

    }

    fn from_ordinal_unchecked(ord: OrdinalDate) -> Self {

        let year = ord.year;

        let month = (((ord.day_of_year - 1) as i64).div_euclid(28) + 1) as u8;

        let day = (ord.day_of_year as i64).adjusted_remainder(28) as u8;

        debug_assert!(day > 0 && day < 29);

        Positivist(CommonDate::new(year, month, day))

    }

}

impl HasEpagemonae<PositivistComplementaryDay> for Positivist {

    // Calendier Positiviste Page 8

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

        if self.0.month == NON_MONTH {

            PositivistComplementaryDay::from_u8(self.0.day)

        } else {

            None

        }

    }

    fn epagomenae_count(p_year: i32) -> u8 {

        if Positivist::is_leap(p_year) {

            2

        } else {

            1

        }

    }

}

impl Perennial<PositivistMonth, Weekday> for Positivist {

    // Calendier Positiviste Page 23-30

    fn weekday(self) -> Option<Weekday> {

        if self.0.month == NON_MONTH {

            None

        } else {

            Weekday::from_i64((self.0.day as i64).modulus(7))

        }

    }

    fn days_per_week() -> u8 {

        7

    }

    fn weeks_per_month() -> u8 {

        4

    }

}

impl HasLeapYears for Positivist {

    // Not sure about the source for this...

    fn is_leap(p_year: i32) -> bool {

        Gregorian::is_leap(POSITIVIST_YEAR_OFFSET + p_year)

    }

}

impl CalculatedBounds for Positivist {}

impl Epoch for Positivist {

    fn epoch() -> Fixed {

        Gregorian::try_year_start(POSITIVIST_YEAR_OFFSET)

            .expect("Year known to be valid")

            .to_fixed()

    }

}

impl FromFixed for Positivist {

    fn from_fixed(date: Fixed) -> Positivist {

        let ord_g = Gregorian::ordinal_from_fixed(date);

        let ord = OrdinalDate {

            year: ord_g.year - POSITIVIST_YEAR_OFFSET,

            day_of_year: ord_g.day_of_year,

        };

        Self::from_ordinal_unchecked(ord)

    }

}

impl ToFixed for Positivist {

    fn to_fixed(self) -> Fixed {

        let y = self.0.year + POSITIVIST_YEAR_OFFSET;

        let offset_y = Gregorian::try_year_start(y)

            .expect("Year known to be valid")

            .to_fixed()

            .get_day_i()

            - 1;

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

        Fixed::cast_new(offset_y + doy)

    }

}

impl ToFromCommonDate<PositivistMonth> for Positivist {

    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_MONTH26.7k
 {

            Err(CalendarError::InvalidMonth)

        } else if date.day < 1 {

            Err(CalendarError::InvalidDay)

        } else if date.month < NON_MONTH && 
date.day > 2821.5k
 {

            Err(CalendarError::InvalidDay)

        } else if date.month == NON_MONTH && 
date.day4.49k
 > Positivist::epagomenae_count(date.year) {

            Err(CalendarError::InvalidDay)

        } else {

            Ok(())

        }

    }

    fn year_end_date(year: i32) -> CommonDate {

        CommonDate::new(year, NON_MONTH, Positivist::epagomenae_count(year))

    }

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

        28

    }

}

impl Quarter for Positivist {

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

        match self.try_week_of_year() {

            None => NonZero::new(4).unwrap(),

            Some(w) => NonZero::new((w - 1) / 13 + 1).expect("w > 0"),

        }

    }

}

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

pub type PositivistMoment = CalendarMoment<Positivist>;

#[cfg(test)]

mod tests {

    use super::*;

    #[test]

    fn epoch() {

        let dg = Gregorian::try_from_common_date(CommonDate::new(1789, 1, 1)).unwrap();

        let dp = Positivist::try_from_common_date(CommonDate::new(1, 1, 1)).unwrap();

        let fg = dg.to_fixed();

        let fp = dp.to_fixed();

        assert_eq!(fg, fp);

    }

    #[test]

    fn example_from_text() {

        //The Positivist Calendar, page 37

        let dg = Gregorian::try_from_common_date(CommonDate::new(1855, 1, 1)).unwrap();

        let dp = Positivist::try_from_common_date(CommonDate::new(67, 1, 1)).unwrap();

        let fg = dg.to_fixed();

        let fp = dp.to_fixed();

        assert_eq!(fg, fp);

    }

}