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use serde::{Deserialize,Serialize};
use chrono::{NaiveDate,Datelike};
use crate::calendar::{Calendar};

/// Rules to adjust dates to business days
/// The rule "Modified Preceding" commonly referred to in text books
/// was intentionally left out since 
#[derive(Deserialize, Serialize, Debug)]
pub enum DayAdjust {
    #[serde(rename = "none")]
    None,
    #[serde(rename = "following")]
    Following,
    #[serde(rename = "preceding")]
    Preceding,
    /// Next business day, if it falls in the same month, otherwise preceding business day
    #[serde(rename = "modified")]
    #[serde(alias = "modified following")]
    Modified,
}

impl DayAdjust {
    pub fn adjust_date(&self, date: NaiveDate, cal: &Calendar) -> NaiveDate {
        match self {
            DayAdjust::None => date,
            DayAdjust::Following => if cal.is_holiday(date) { cal.next_bday(date) } else { date },
            DayAdjust::Preceding => if cal.is_holiday(date) { cal.prev_bday(date) } else { date },
            DayAdjust::Modified => {
                if cal.is_business_day(date) { date }
                else {
                    let new_date = cal.next_bday(date);
                    if new_date.month() != date.month() {
                        cal.prev_bday(date)
                    } else {
                        new_date
                    }
                }
            }
        }
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use crate::calendar::Holiday;

    #[test]
    fn day_adjust() {
        let holidays = vec![ 
            Holiday::SingularDay(NaiveDate::from_ymd(2019,10,10)), 
            Holiday::SingularDay(NaiveDate::from_ymd(2019,10,31)) 
        ];
        let cal = Calendar::calc_calendar(&holidays, 2019, 2019);
        let rule = DayAdjust::None;
        assert_eq!(rule.adjust_date(NaiveDate::from_ymd(2019,10,1), &cal), NaiveDate::from_ymd(2019,10,1));
        assert_eq!(rule.adjust_date(NaiveDate::from_ymd(2019,10,10), &cal), NaiveDate::from_ymd(2019,10,10));
        assert_eq!(rule.adjust_date(NaiveDate::from_ymd(2019,10,31), &cal), NaiveDate::from_ymd(2019,10,31));
        assert_eq!(rule.adjust_date(NaiveDate::from_ymd(2019,11,30), &cal), NaiveDate::from_ymd(2019,11,30));
        let rule = DayAdjust::Following;
        assert_eq!(rule.adjust_date(NaiveDate::from_ymd(2019,10,1), &cal), NaiveDate::from_ymd(2019,10,1));
        assert_eq!(rule.adjust_date(NaiveDate::from_ymd(2019,10,10), &cal), NaiveDate::from_ymd(2019,10,11));
        assert_eq!(rule.adjust_date(NaiveDate::from_ymd(2019,10,31), &cal), NaiveDate::from_ymd(2019,11,1));
        assert_eq!(rule.adjust_date(NaiveDate::from_ymd(2019,11,30), &cal), NaiveDate::from_ymd(2019,11,30));
        let rule = DayAdjust::Preceding;
        assert_eq!(rule.adjust_date(NaiveDate::from_ymd(2019,10,1), &cal), NaiveDate::from_ymd(2019,10,1));
        assert_eq!(rule.adjust_date(NaiveDate::from_ymd(2019,10,10), &cal), NaiveDate::from_ymd(2019,10,9));
        assert_eq!(rule.adjust_date(NaiveDate::from_ymd(2019,10,31), &cal), NaiveDate::from_ymd(2019,10,30));
        assert_eq!(rule.adjust_date(NaiveDate::from_ymd(2019,11,30), &cal), NaiveDate::from_ymd(2019,11,30));
        let rule = DayAdjust::Modified;
        assert_eq!(rule.adjust_date(NaiveDate::from_ymd(2019,10,1), &cal), NaiveDate::from_ymd(2019,10,1));
        assert_eq!(rule.adjust_date(NaiveDate::from_ymd(2019,10,10), &cal), NaiveDate::from_ymd(2019,10,11));
        assert_eq!(rule.adjust_date(NaiveDate::from_ymd(2019,10,31), &cal), NaiveDate::from_ymd(2019,10,30));
        assert_eq!(rule.adjust_date(NaiveDate::from_ymd(2019,11,30), &cal), NaiveDate::from_ymd(2019,11,30));
    }
}