use crate::prelude::*;

pub struct MaxSize {
    pub inner: StrongWidget,
    pub x: Option<LayoutLen>,
    pub y: Option<LayoutLen>,
}

impl MaxSize {
    fn clamp(len: LayoutLen, max: Option<LayoutLen>, output: f32, density: f32) -> LayoutLen {
        let Some(max) = max else {
            return len;
        };
        let len_px = len.apply_rest(density).to_abs(output);
        let max_px = max.apply_rest(density).to_abs(output);
        if len_px > max_px {
            max.fold_dp(density)
        } else {
            len
        }
    }

    fn clamp_region(offered_px: f32, max: Option<LayoutLen>, output: f32, density: f32) -> UiSpan {
        let Some(max) = max else {
            return UiSpan::FULL;
        };
        let max_scalar = max.apply_rest(density);
        let max_px = max_scalar.to_abs(output);
        if offered_px > max_px {
            max_scalar.align(AxisAlign::Neg)
        } else {
            UiSpan::FULL
        }
    }
}

impl Widget for MaxSize {
    fn draw(&mut self, painter: &mut Painter) {
        let output = painter.output_size();
        let density = painter.density();
        let offered = painter.px_size();
        let region = UiRegion {
            x: Self::clamp_region(offered.x, self.x, output.x, density),
            y: Self::clamp_region(offered.y, self.y, output.y, density),
        };
        let used = painter.widget_within(&self.inner, region).size();
        let size = Size {
            x: Self::clamp(used.x, self.x, output.x, density),
            y: Self::clamp(used.y, self.y, output.y, density),
        };
        painter.place_used(&self.inner, size, UiRegion::FULL);
        painter.set_size(size);
    }
}