From 2c0635d8b77aaad71600ef48a304197a74c08b7d Mon Sep 17 00:00:00 2001
From: Martin Meyerhoff <mamhoff@gmail.com>
Date: Fri, 9 Apr 2021 16:27:13 +0200
Subject: [PATCH] Delete nested elements quickly

This builds an array of all the descendent elements from this element,
and then calls the DeleteElements service class on them. Afterwards it
resets the two associations, so that no callbacks run on in-memory
deleted objects.
---
 app/models/alchemy/element.rb       | 15 +++++++++++++++
 spec/models/alchemy/element_spec.rb | 14 ++++++++++++++
 2 files changed, 29 insertions(+)

diff --git a/app/models/alchemy/element.rb b/app/models/alchemy/element.rb
index 26f67864bb..c828ebd9c6 100644
--- a/app/models/alchemy/element.rb
+++ b/app/models/alchemy/element.rb
@@ -70,6 +70,8 @@ class Element < BaseRecord
 
     has_many :contents, dependent: :destroy, inverse_of: :element
 
+    before_destroy :delete_all_nested_elements
+
     has_many :all_nested_elements,
       -> { order(:position) },
       class_name: "Alchemy::Element",
@@ -347,5 +349,18 @@ def touch_touchable_pages
 
       touchable_pages.each(&:touch)
     end
+
+    def delete_all_nested_elements
+      deeply_nested_elements = descendent_elements(self).flatten
+      DeleteElements.new(deeply_nested_elements).call
+      nested_elements.reset
+      all_nested_elements.reset
+    end
+
+    def descendent_elements(element)
+      element.all_nested_elements + element.all_nested_elements.map do |nested_element|
+        descendent_elements(nested_element)
+      end
+    end
   end
 end
diff --git a/spec/models/alchemy/element_spec.rb b/spec/models/alchemy/element_spec.rb
index 3fa31ebcf0..d0a32ce186 100644
--- a/spec/models/alchemy/element_spec.rb
+++ b/spec/models/alchemy/element_spec.rb
@@ -968,4 +968,18 @@ module Alchemy
       end
     end
   end
+
+  describe "destroy callbacks" do
+    let(:element) { create(:alchemy_element) }
+    let!(:nested_element_1) { create(:alchemy_element, parent_element: element) }
+    let!(:nested_element_2) { create(:alchemy_element, parent_element: nested_element_1) }
+    let!(:nested_element_3) { create(:alchemy_element, parent_element: nested_element_2) }
+
+    it "destroys all the nested elements quickly" do
+      expect(Alchemy::DeleteElements).to receive(:new).with(
+        [nested_element_1, nested_element_2, nested_element_3]
+      ).and_call_original
+      element.reload.destroy!
+    end
+  end
 end