feat: add toHierarchy utility for TreeView, RecursiveList (#2072)

Co-authored-by: Bram <bramhavers@gmail.com>

src/utils/toHierarchy.js

@@ -0,0 +1,49 @@
+// @ts-check
+/**
+ * Create a nested array from a flat array.
+ * @typedef {Object} NodeLike
+ * @property {string | number} id - Unique identifier for the node
+ * @property {NodeLike[]} [nodes] - Optional array of child nodes
+ * @property {Record<string, any>} [additionalProperties] - Any additional properties
+ *
+ * @param {NodeLike[]} flatArray - Array of flat nodes to convert
+ * @param {function(NodeLike): (string|number|null)} getParentId - Function to get parent ID for a node
+ * @returns {NodeLike[]} Hierarchical tree structure
+ */
+export function toHierarchy(flatArray, getParentId) {
+  /** @type {NodeLike[]} */
+  const tree = [];
+  const childrenOf = new Map();
+  const itemsMap = new Map(flatArray.map((item) => [item.id, item]));
+
+  flatArray.forEach((item) => {
+    const parentId = getParentId(item);
+
+    // Only create nodes array if we have children.
+    const children = childrenOf.get(item.id);
+    if (children) {
+      item.nodes = children;
+    }
+
+    // Check if parentId exists using Map instead of array lookup.
+    const parentExists = parentId && itemsMap.has(parentId);
+
+    if (parentId && parentExists) {
+      if (!childrenOf.has(parentId)) {
+        childrenOf.set(parentId, []);
+      }
+      childrenOf.get(parentId).push(item);
+
+      const parent = itemsMap.get(parentId);
+      if (parent) {
+        parent.nodes = childrenOf.get(parentId);
+      }
+    } else {
+      tree.push(item);
+    }
+  });
+
+  return tree;
+}
+
+export default toHierarchy;