/// A unit of linear measurement
///
/// This is commonly combined with [`Rect`], [`Point`](crate::geometry::Point) and [`Size<T>`].
/// The default value is [`Dimension::Undefined`].
#[derive(Copy, Clone, PartialEq, Debug)]
#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
pub enum Dimension {
    /// The dimension is not given
    Undefined,
    /// The dimension should be automatically computed
    Auto,
    /// The dimension is stored in [points](https://en.wikipedia.org/wiki/Point_(typography))
    ///
    /// Each point is about 0.353 mm in size.
    Points(f32),
    /// The dimension is stored in percentage relative to the parent item.
    Percent(f32),
    /// The dimension is stored as the sum of percentage relative to the parent item and point.
    PercentPoints(f32, f32),
}

impl Dimension {
    /// Is this value defined?
    pub(crate) fn is_defined(self) -> bool {
        matches!(self, Dimension::Points(_) | Dimension::Percent(_) | Dimension::PercentPoints(_, _))
    }
}

impl MaybeResolve<Option<f32>> for Dimension {
    /// Converts the given [`Dimension`] into a concrete value of points
    ///
    /// Can return `None`
    fn maybe_resolve(self, context: Option<f32>) -> Option<f32> {
        match self {
            Dimension::Points(points) => Some(points),
            // parent_dim * percent
            Dimension::Percent(percent) => context.map(|dim| dim * percent),
            Dimension::PercentPoints(percent, points) => Some(context.map_or(points, |dim| dim * percent + points)),
            _ => None,
        }
    }
}