export function ensureBalancedChildInNode()

in packages/core/micro/src/adjust-tree/node.ts [223:260]

• 35 lines of code
• 6 McCabe index (conditional complexity)

export function ensureBalancedChildInNode<T>(ctx: TreeContext<T>, parent: InteriorNode<T>, childIndex: number): Orphan<T> | undefined {
    const size = parent.size;
    const { segments } = parent;
    const child = segments[childIndex]
    if (child.size >= ctx.order) {
        return undefined;
    }
    if (size < 2) {
        return { node: child, heightDelta: 1, length: parent.lengths[childIndex] };
    }
    let leftIndex;
    let rightIndex;
    if (childIndex === 0) {
        leftIndex = 0;
        rightIndex = 1;
    } else {
        leftIndex = childIndex - 1;
        rightIndex = childIndex;
    }
    const rhs = segments[rightIndex];
    // Cast here is just to guarantee that both nodes are of the same
    // kind. We don't care whether they are interior or leaf nodes.
    const balancing = rebalanceNodes(ctx, segments[leftIndex] as InteriorNode<T>, rhs as InteriorNode<T>);
    if (balancing === 0) {
        return undefined;
    }
    const { lengths } = parent;
    if (rhs.size === 0) {
        lengths[leftIndex] += balancing;
        assert("ensureBalancedChildInNode - deleting right should return a delta equal to rhs len ", balancing === lengths[rightIndex]);
        deleteNodeRange(parent, rightIndex, 1, undefined!);
        return undefined;
    }
    lengths[leftIndex] += balancing;
    lengths[rightIndex] -= balancing;
    return undefined;

}