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/// Represents the data present in a quad-tree node.
/// May be the base-level repr, or a node with 4 children.
pub enum Quad<A: Default, B> {
    /// Base cell in grid.
    /// May actually be a chunk of cells for performance.
    Base(A),
    /// Node with 4 children.
    Node(Box<[Node<A, B>;4]>),
    /// Children may be generated from Node.
    Cached,
}

/// Represends a node in a quadtree.
/// Has a depth denoting the number of nodes below it.
/// Nodes should only be siblings of nodes with the same depth.
/// Data stored inside a quadtree node, including children, are in `data`.
pub struct Node<A: Default, B> {
    depth: usize,
    compr: B,
    data:  Quad<A, B>,
}

/// Represents a context with shared state.
pub struct Ctx();

impl<A: Default, B> Node<A, B> {
    /// Creates a new tree from a single base node
    pub fn new_base(base: A, ctx: &mut Ctx) -> Self {
        Node {
            depth: 0,
            compr: ctx.compress(&base),
            data:  Quad::Base(base),
        }
    }

    /// Creates a new tree with a single empty base node
    pub fn new_empty(ctx: &mut Ctx) -> Self {
        Self::new_base(Default::default(), ctx)
    }

    /// Creates a new node double the size by centering the current node
    /// on a node double the size.
    pub fn pad_empty(self, ctx: &mut Ctx) -> Self {
        todo!()
    }

    
}