use super::big_num::U128;

///! Math functions that do not check inputs or outputs
///! Contains methods that perform common math functions but do not do any
///! overflow or underflow checks

pub trait UnsafeMathTrait {
    /// Returns ceil (x / y)
    /// Division by 0 throws a panic, and must be checked externally
    ///
    /// In Solidity dividing by 0 results in 0, not an exception.
    ///
    /// # Arguments
    ///
    /// * `x` - The dividend
    /// * `y` - The divisor
    ///
    fn div_rounding_up(x: Self, y: Self) -> Self;
}

impl UnsafeMathTrait for u64 {
    fn div_rounding_up(x: Self, y: Self) -> Self {
        x / y + ((x % y > 0) as u64)
    }
}

impl UnsafeMathTrait for U128 {
    fn div_rounding_up(x: Self, y: Self) -> Self {
        x / y + U128::from((x % y > U128::default()) as u8)
    }
}

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

    #[test]
    fn divide_by_factor() {
        assert_eq!(u64::div_rounding_up(4, 2), 2);
    }

    #[test]
    fn divide_and_round_up() {
        assert_eq!(u64::div_rounding_up(4, 3), 2);
    }

    #[test]
    #[should_panic]
    fn divide_by_zero() {
        u64::div_rounding_up(2, 0);
    }
}