How to create Parent Child Array using HashMap?

Developers
1

I would like to create Parent Child array how it’s possible

i create listCategory function but i don’t know how to make parent child array in listCategory function

here is my code.

type CategoryId = Nat32;
  type Category = {
    id : CategoryId;
    name : Text;
    parent_id : Int;
    sort_order : Int;
  };

  type ParentChildCategory = {
    id : CategoryId;
    name : Text;
    parent_id : Int;
    children : [child];
    sort_order : Int;
  };

  type child = {
    id : CategoryId;
    name : Text;
    parent_id : Int;
    sort_order : Int;
  };

  private stable var categoryEntries : [(CategoryId, Category)] = [];

  var categoryHashMap = HashMap.HashMap<CategoryId, Category>(
    10,
    func(x, y) { x == y },
    func(x) { x },
  );

  stable var lastCategoryId : Nat32 = 0;

  private func nextCategoryId() : Nat32 {
    lastCategoryId += 1;
    lastCategoryId;
  };

  public func addNewCategory(id : Nat32, category : Category) {
    let id = nextCategoryId();
    categoryHashMap.put(id, addCategory(id, category));
  };

  func addCategory(categoryId : Nat32, category : Category) : Category {
    {
      id = categoryId;
      name = category.name;
      parent_id = category.parent_id;
      description = category.description;
      status = category.status;
      sort_order = category.sort_order;
    };
  };


  public func listCategory() : async [Category] {
    let buff : Buffer.Buffer<Category> = Buffer.Buffer(10);
    for (e in categoryHashMap.vals()) {
      Debug.print(debug_show (e));
      buff.add(e);
    };
    buff.toArray();
  };

I want this kind of output.

[
    {
        name: "name",
        id:"id",
        parent_id : "parent_id",
        sort_order : "sort_order",
        "children": [
            {
                name: "name",
                id:"id",
                parent_id : "parent_id",
                sort_order : "sort_order",
                "children" : [
                    {
                         name: "name",
                         id:"id",
                         parent_id : "parent_id",
                         sort_order : "sort_order",
                    }
                ]
            }, 
            {
                 name: "name",
                 id:"id",
                 parent_id : "parent_id",
                 sort_order : "sort_order",
                "children" : [
                    {
                         name: "name",
                         id:"id",
                         parent_id : "parent_id",
                         sort_order : "sort_order",
                    },
                    {
                        name: "name",
                         id:"id",
                         parent_id : "parent_id",
                         sort_order : "sort_order",
                    }
                ]
            }
        ]
    }
]
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