export const TreeFlattenMixin = (superClass) => class TreeFlattenMixin extends superClass {
  _flattenNodes() {
    const results = [];
    const roots = Array.isArray(this.roots) ? this.roots : [];

    const walk = (nodes, depth, path) => {
      if (!Array.isArray(nodes)) return;
      nodes.forEach((node, index) => {
        const slug = node?.slug ?? `${index}`;
        const nextPath = [...path, slug];
        const states = Array.isArray(node?.states) ? node.states : [];
        const hasChildren = this._isExpandableNode(node);
        const expanded = states.includes('expanded');

        results.push({
          node,
          depth,
          path: nextPath,
          hasChildren,
          expanded,
          key: nextPath.join('/'),
        });

        if (hasChildren && expanded && Array.isArray(node?.children) && node.children.length > 0) {
          walk(node.children, depth + 1, nextPath);
        }
      });
    };

    walk(roots, 0, []);
    return results;
  }

  _findFlatIndexByKey(key) {
    const items = Array.isArray(this._flatItems) ? this._flatItems : [];
    return items.findIndex((it) => it?.key === key);
  }
};