use chrono::{Datelike, Duration, Months, NaiveDate, Weekday};

#[derive(Debug)]
pub struct CalendarRow {
    pub begin: NaiveDate,
    pub end: NaiveDate,
}

pub enum RowDay {
    InRange(NaiveDate),
    NotInRange(NaiveDate),
}

impl RowDay {
    pub fn new(row: &CalendarRow, day: NaiveDate) -> RowDay {
        if day >= row.begin && day < row.end {
            RowDay::InRange(day)
        } else {
            RowDay::NotInRange(day)
        }
    }

    pub fn day(self) -> NaiveDate {
        match self {
            Self::InRange(day) => day,
            Self::NotInRange(day) => day,
        }
    }
}

/// A row in the calendar.
///
/// The row is always aligned to a week, i.e. the first
/// day of the row is the first day of the week (for now always Monday)
impl CalendarRow {
    /// A row that spans the month containing the given day    
    pub fn for_month(day: NaiveDate) -> CalendarRow {
        let begin = day.with_day0(0).unwrap();
        CalendarRow {
            begin,
            end: begin + Months::new(1),
        }
    }

    /// A row that spans the week containing the given day    
    pub fn for_week(day: NaiveDate) -> CalendarRow {
        let begin = day.week(Weekday::Mon).first_day();
        CalendarRow {
            begin,
            end: begin + Duration::weeks(1),
        }
    }

    /// Get the day for the given column of the row
    pub fn date_for_col(self: &Self, col: i64) -> RowDay {
        RowDay::new(
            self,
            self.begin.week(Weekday::Mon).first_day() + Duration::days(col),
        )
    }
    
    pub fn num_days(&self) -> i64 {
    	(self.end - self.begin).num_days()
    }
}