use super::prelude::*;

/// `move`: Move content without affecting layout.
pub fn move_(_: &mut EvalContext, args: &mut Args) -> TypResult<Value> {
    let offset = Spec::new(args.named("x")?, args.named("y")?);
    let body: Template = args.expect("body")?;
    Ok(Value::Template(Template::from_inline(move |style| {
        body.pack(style).moved(offset)
    })))
}

/// A node that moves its child without affecting layout.
#[derive(Debug, Hash)]
pub struct MoveNode {
    /// The node whose contents should be moved.
    pub child: PackedNode,
    /// How much to move the contents.
    pub offset: Spec<Option<Linear>>,
}

impl Layout for MoveNode {
    fn layout(
        &self,
        ctx: &mut LayoutContext,
        regions: &Regions,
    ) -> Vec<Constrained<Rc<Frame>>> {
        let mut frames = self.child.layout(ctx, regions);

        for (Constrained { item: frame, .. }, (_, base)) in
            frames.iter_mut().zip(regions.iter())
        {
            Rc::make_mut(frame).translate(Point::new(
                self.offset.x.map(|x| x.resolve(base.w)).unwrap_or_default(),
                self.offset.y.map(|y| y.resolve(base.h)).unwrap_or_default(),
            ));
        }

        frames
    }
}