Bootstrap the Trash node: reserved slug, identity, guards

3 files changed, 119 insertions, 2 deletions

diff --git a/app/models/node.rb b/app/models/node.rb
index dc69508..a2e9981 100644
--- a/app/models/node.rb
+++ b/app/models/node.rb
@@ -19,6 +19,7 @@ class Node < ApplicationRecord
   before_save    :check_for_changed_slug
   after_save     :update_unique_names_of_children
   before_destroy :refuse_destroy_with_children
+  before_destroy :refuse_destroying_trash_node
 
   # Validations
   validates_length_of     :slug, :within => 1..255,    :unless => -> { parent_id.nil? || slug.blank? }
@@ -26,6 +27,8 @@ class Node < ApplicationRecord
   validates_uniqueness_of :slug, :scope => :parent_id, :unless => -> { parent_id.nil? }
   validates_presence_of   :parent_id,                  :unless => -> { Node.root.nil? }
 
+  validate :reserved_slug_stays_reserved
+  validate :no_head_inside_trash
   validates :default_template_name,
             :inclusion => { :in => ->(_) { Page.custom_templates } },
             :allow_nil => true,
@@ -57,6 +60,15 @@ class Node < ApplicationRecord
     nil
   end
 
+  # The Trash container node. Lazily self-creating and idempotent, so
+  # every environment acquires it on first touch.
+  # Never call from validations. the positional predicates below
+  # exist for that.
+  def self.trash
+    root.children.find_by(:slug => CccConventions::TRASH_SLUG) ||
+      root.children.create!(:slug => CccConventions::TRASH_SLUG)
+  end
+
   # Instance Methods
 
   # Acquires (or reaffirms) the editing lock without creating a draft or
@@ -203,6 +215,10 @@ class Node < ApplicationRecord
     # Return nil if nothing to publish and no staged changes
     return nil unless self.draft || staged_slug || staged_parent_id
 
+    if in_trash? || trash_node?
+      raise ActiveRecord::RecordInvalid.new(self), "Cannot publish a node in the Trash"
+    end
+
     path_before = self.unique_name
 
     ActiveRecord::Base.transaction do
@@ -322,6 +338,20 @@ class Node < ApplicationRecord
     autosave || draft || head
   end
 
+  def trash_node?
+    parent&.root? && slug == CccConventions::TRASH_SLUG
+  end
+
+  # Inside the Trash subtree. False for the Trash node itself.
+  def in_trash?
+    current = parent
+    while current
+      return true if current.trash_node?
+      current = current.parent
+    end
+    false
+  end
+
   # Returns immutable node id for all new nodes so that the atom feed entry ids
   # stay the same eventhough the slug or positions changes.
   # Can be removed after a year or so ;)
@@ -435,4 +465,36 @@ class Node < ApplicationRecord
         end
       end
     end
+
+  private
+
+    def reserved_slug_stays_reserved
+      if parent&.root? && !trash_node_already_me?
+        errors.add(:slug, "is reserved for the Trash") if slug == CccConventions::TRASH_SLUG
+        errors.add(:staged_slug, "is reserved for the Trash") if staged_slug == CccConventions::TRASH_SLUG
+      end
+
+      if persisted? && slug_was == CccConventions::TRASH_SLUG && Node.find(id).trash_node?
+        errors.add(:slug, "of the Trash node cannot change") if slug_changed?
+        errors.add(:parent_id, "of the Trash node cannot change") if parent_id_changed?
+        errors.add(:staged_slug, "must stay empty on the Trash node") if staged_slug.present?
+        errors.add(:staged_parent_id, "must stay empty on the Trash node") if staged_parent_id.present?
+      end
+    end
+
+    def trash_node_already_me?
+      existing = Node.root&.children&.find_by(:slug => CccConventions::TRASH_SLUG)
+      existing.nil? || existing.id == id
+    end
+
+    def no_head_inside_trash
+      return unless head_id.present?
+      errors.add(:head_id, "cannot exist inside the Trash") if in_trash? || trash_node?
+    end
+
+    def refuse_destroying_trash_node
+      return unless trash_node?
+      errors.add(:base, "The Trash node cannot be destroyed")
+      throw :abort
+    end
 end
diff --git a/lib/ccc_conventions.rb b/lib/ccc_conventions.rb
index 352dd3c..7ff5a3a 100644
--- a/lib/ccc_conventions.rb
+++ b/lib/ccc_conventions.rb
@@ -1,6 +1,7 @@
 module CccConventions
-  ERFA_PARENT_NAME       = "club/erfas"
-  CHAOSTREFF_PARENT_NAME = "club/chaostreffs"
+  TRASH_SLUG              = "trash"
+  ERFA_PARENT_NAME        = "club/erfas"
+  CHAOSTREFF_PARENT_NAME  = "club/chaostreffs"
   SITEMAP_COLLAPSED_PATHS = %w[updates club/erfas club/chaostreffs disclosure].freeze
 
   NODE_KINDS = {
diff --git a/test/models/node_test.rb b/test/models/node_test.rb
index 9c4834e..3fb2d23 100644
--- a/test/models/node_test.rb
+++ b/test/models/node_test.rb
@@ -807,4 +807,58 @@ class NodeTest < ActiveSupport::TestCase
 
     assert_equal 0, Page.where(:id => autosave_id).count
   end
+
+  test "Node.trash lazily creates the container exactly once" do
+    assert_difference "Node.count", 1 do
+      Node.trash
+    end
+    assert_no_difference "Node.count" do
+      assert_equal Node.trash, Node.trash
+    end
+    assert Node.trash.trash_node?
+    assert_not Node.trash.in_trash?
+  end
+
+  test "in_trash? walks the whole parent chain" do
+    child = Node.trash.children.create!(:slug => "trashed_thing")
+    grandchild = child.children.create!(:slug => "trashed_deeper")
+
+    assert child.in_trash?
+    assert grandchild.in_trash?
+    assert_not Node.root.children.create!(:slug => "living_thing").in_trash?
+  end
+
+  test "the reserved slug is refused for other root children, live and staged" do
+    Node.trash
+
+    assert_not Node.root.children.build(:slug => CccConventions::TRASH_SLUG).valid?
+    assert_not Node.root.children.build(:slug => "fine", :staged_slug => CccConventions::TRASH_SLUG).valid?
+    assert Node.trash.children.create!(:slug => "sub").children.build(:slug => CccConventions::TRASH_SLUG).valid?
+  end
+
+  test "the Trash node refuses rename, move, and destroy" do
+    trash = Node.trash
+    other = Node.root.children.create!(:slug => "not_the_trash")
+
+    trash.slug = "recycling"
+    assert_not trash.valid?
+
+    trash.reload.parent_id = other.id
+    assert_not trash.valid?
+
+    assert_no_difference "Node.count" do
+      assert_not trash.reload.destroy
+    end
+  end
+
+  test "a head cannot exist inside the Trash, and publishing there is refused" do
+    node = Node.trash.children.create!(:slug => "no_publish_here")
+    page = node.pages.create!
+
+    node.head = page
+    assert_not node.valid?
+
+    node.reload
+    assert_raises(ActiveRecord::RecordInvalid) { node.publish_draft! }
+  end
 end