use diesel::{
    backend::Backend,
    deserialize::{FromSql, FromSqlRow},
    expression::AsExpression,
    sql_types::Integer,
    sqlite::Sqlite,
};

#[derive(Clone, Copy, Hash, PartialEq, Eq, Debug, AsExpression, FromSqlRow)]
#[diesel(sql_type=Integer)]
pub struct ActualbudgetDate(i64);

#[derive(Clone, PartialOrd, PartialEq, Eq)]
enum DatePart {
    MonthOfYear,
    DayOfMonth,
}

// actualbudget represents dates as numbers which "look like" the corresponding
// ISO string when written in decimal. E.g. 20240901 represents 1 Sep 2024. It
// also uses month specifiers, e.g. 202409 to represent Sep 2024. In this case,
// we interpret this as the first day of the month, e.g. 2024-09-01.

impl ActualbudgetDate {
    pub fn to_iso(&self) -> String {
        format!(
            "{0}-{1}-{2}T00:00:00.000Z",
            self.year(),
            self.month(),
            self.day()
        )
    }

    pub fn to_iso_date(&self) -> String {
        format!("{0}-{1}-{2}", self.year(), self.month(), self.day())
    }

    pub fn year(&self) -> String {
        self.0.to_string()[0..4].to_string()
    }

    pub fn month(&self) -> String {
        self.0.to_string()[4..6].to_string()
    }

    pub fn day(&self) -> String {
        match self.date_part() {
            DatePart::DayOfMonth => self.0.to_string()[6..8].to_string(),
            DatePart::MonthOfYear => String::from("01"),
        }
    }

    pub fn from_i32(i: i32) -> Self {
        ActualbudgetDate(i.into())
    }

    pub fn from_ymd<T, S, U>(year: T, month: S, day: U) -> Self
    where
        T: Into<i64>,
        S: Into<i64>,
        U: Into<i64>,
    {
        Self(year.into() * 10_000 + month.into() * 100 + day.into())
    }

    pub fn oldest_valid_date() -> Self {
        Self(10000101)
    }

    fn date_part(&self) -> DatePart {
        if self.0 < 10000000 {
            DatePart::MonthOfYear
        } else {
            DatePart::DayOfMonth
        }
    }

    fn dayified_value(&self) -> i64 {
        match self.date_part() {
            DatePart::DayOfMonth => self.0,
            DatePart::MonthOfYear => self.0 * 100 + 1,
        }
    }
}

impl Ord for ActualbudgetDate {
    fn cmp(&self, other: &Self) -> std::cmp::Ordering {
        self.dayified_value().cmp(&other.dayified_value())
    }
}

impl PartialOrd for ActualbudgetDate {
    fn partial_cmp(&self, other: &Self) -> Option<std::cmp::Ordering> {
        Some(self.cmp(other))
    }
}

impl FromSql<Integer, Sqlite> for ActualbudgetDate {
    fn from_sql(bytes: <Sqlite as Backend>::RawValue<'_>) -> diesel::deserialize::Result<Self> {
        let int: i32 = FromSql::<Integer, Sqlite>::from_sql(bytes)?;
        Ok(ActualbudgetDate(int.into()))
    }
}

#[cfg(test)]
mod test {
    use crate::ActualbudgetDate;

    #[test]
    fn when_from_ymd_2026_01_16_then_constructs_2026_01_16() {
        let actualbudget_date = ActualbudgetDate::from_ymd(2026, 1, 16);
        assert_eq!(actualbudget_date.year(), "2026");
        assert_eq!(actualbudget_date.month(), "01");
        assert_eq!(actualbudget_date.day(), "16");
    }
}