use crate::math::Xform;

pub struct TransformStack {
    stack: Vec<Xform>,
}

impl TransformStack {
    pub fn new() -> TransformStack {
        TransformStack { stack: Vec::new() }
    }

    pub fn clear(&mut self) {
        self.stack.clear();
    }

    pub fn push(&mut self, xform: Xform) {
        match self.stack.last() {
            None => self.stack.push(xform),
            Some(prev_xform) => self.stack.push(xform.compose(prev_xform)),
        }
    }

    pub fn pop(&mut self) -> Option<Xform> {
        self.stack.pop()
    }

    pub fn top(&self) -> Option<&Xform> {
        self.stack.last()
    }
}