remove item from heap

lib/rock/struct/heap.ex

@@ -18,6 +18,24 @@ defmodule Rock.Struct.Heap do
     %Heap{cluster_uuid: uuid, items: items}
   end
 
+  def remove_item(%Heap{items: items, cluster_uuid: cluster_uuid}, uuid) do
+    new_items = items |> _remove_item(items, uuid)
+
+    %Heap{cluster_uuid: cluster_uuid, items: new_items}
+  end
+
+  defp _remove_item(items, [{_, _, cluster_uuid} = item | _], uuid) when cluster_uuid == uuid do
+    items |> List.delete(item)
+  end
+
+  defp _remove_item(_, [_, []], uuid) do
+    raise ArgumentError, message: "heap does not have the item with uuid #{uuid}"
+  end
+
+  defp _remove_item(items, [_item | tail], uuid) do
+    items |> _remove_item(tail, uuid)
+  end
+
   defp prepare_items(cluster, clusters, link_matrix, theta) do
     clusters
     |> calculate_items(cluster, link_matrix, theta)

test/rock/struct/heap_test.exs

@@ -4,6 +4,7 @@ defmodule Rock.Struct.HeapTest do
   alias Rock.Struct.Point
   alias Rock.Struct.Heap
   alias Rock.Struct.Cluster
+  alias Rock.Test.TestFactory
 
   test "initializes heap" do
     points = [
@@ -60,5 +61,19 @@ defmodule Rock.Struct.HeapTest do
         end)
     end)
   end
+
+  test "deletes item from heap" do
+    items = [
+      {10, 15, UUID.uuid4},
+      item = {9, 14, uuid = UUID.uuid4},
+      {6, 12, UUID.uuid4},
+      {5, 10, UUID. uuid4}
+    ]
+    heap = TestFactory.create(:heap, items)
+
+    %Heap{items: new_items} = heap |> Heap.remove_item(uuid)
+
+    refute new_items |> Enum.member?(item)
+  end
 end
 

test/support/test_factory.ex

@@ -1,6 +1,7 @@
 defmodule Rock.Test.TestFactory do
   alias Rock.Struct.Point
   alias Rock.Struct.Cluster
+  alias Rock.Struct.Heap
 
   def from_string(:cluster, string_points) do
     string_points
@@ -13,4 +14,8 @@ defmodule Rock.Test.TestFactory do
   def from_string(:point, string_attributes) do
     string_attributes |> Point.new
   end
+
+  def create(:heap, items) do
+    %Heap{cluster_uuid: UUID.uuid4, items: items}
+  end
 end