use super::*;

/// How much less high scaled delimiters can be than what they wrap.
const DELIM_SHORT_FALL: Em = Em::new(0.1);

/// # Left-Right
/// Scales delimiters.
///
/// While matched delimiters scale by default, this can be used to scale
/// unmatched delimiters and to control the delimiter scaling more precisely.
///
/// ## Example
/// ```
/// $ lr(]a, b/2]) $
/// ```
///
/// ## Parameters
/// - body: Content (positional, variadic)
///   The delimited content, including the delimiters.
///
/// ## Category
/// math
#[func]
#[capable(LayoutMath)]
#[derive(Debug, Hash)]
pub struct LrNode(pub Content);

#[node]
impl LrNode {
    fn construct(_: &Vm, args: &mut Args) -> SourceResult<Content> {
        let mut body = Content::empty();
        for (i, arg) in args.all::<Content>()?.into_iter().enumerate() {
            if i > 0 {
                body += AtomNode(','.into()).pack();
            }
            body += arg;
        }
        Ok(Self(body).pack())
    }
}

impl LayoutMath for LrNode {
    fn layout_math(&self, ctx: &mut MathContext) -> SourceResult<()> {
        let mut row = ctx.layout_row(&self.0)?;

        let axis = scaled!(ctx, axis_height);
        let max_extent = row
            .0
            .iter()
            .map(|fragment| (fragment.ascent() - axis).max(fragment.descent() + axis))
            .max()
            .unwrap_or_default();

        let height = 2.0 * max_extent;
        if let [first, .., last] = row.0.as_mut_slice() {
            for fragment in [first, last] {
                if !matches!(
                    fragment.class(),
                    Some(MathClass::Opening | MathClass::Closing | MathClass::Fence)
                ) {
                    continue;
                }

                let MathFragment::Glyph(glyph) = *fragment else { continue };
                let short_fall = DELIM_SHORT_FALL.at(glyph.font_size);
                *fragment = MathFragment::Variant(
                    glyph.stretch_vertical(ctx, height, short_fall),
                );
            }
        }

        for fragment in row.0 {
            ctx.push(fragment);
        }

        Ok(())
    }
}