import type { PrePointOnShape } from '../point-on-shape/point-on-shape.js';
import type { CpNode } from '../cp-node/cp-node.js';
import { RbTree } from 'flo-ll-rb-tree';


/**
 * @internal
 * 
 * Returns the predecessor `CpNode` in the `CpTree` or the same one if they fall
 * on top of each other.
 * 
 * * returns `undefined` if the tree is still empty
 * 
 * @param cpTree 
 * @param pos 
 * @param order 
 * @param order2 
 */
function getCpNodeNeighbors(
        cpTree: RbTree<CpNode>,
        pos: PrePointOnShape,
        order: number,
        order2: number): [CpNode,CpNode] | undefined {

    const pointOnShape = { ...pos, order, order2 };
    const cps = cpTree.findBounds({ pointOnShape } as CpNode);
    const [cp0,cp1] = cps;

    if (cp0 === undefined && cp1 === undefined) { 
        // The tree is still empty
        return undefined;
    }

    if (cp0 === undefined || cp1 === undefined) { 
        // Smaller than all OR larger than all
        const minNode = cpTree.getMinNode()?.datum!;
        const maxNode = cpTree.getMaxNode()?.datum!;

        return [maxNode,minNode];
    }

    return [cp0.datum, cp1.datum];
}


export { getCpNodeNeighbors }