1 files changed, 103 insertions, 0 deletions
diff --git a/app/models/concerns/resolvable_discussion.rb b/app/models/concerns/resolvable_discussion.rb
new file mode 100644
index 00000000000..dd979e7bb17
--- /dev/null
+++ b/app/models/concerns/resolvable_discussion.rb
@@ -0,0 +1,103 @@
+module ResolvableDiscussion
+  extend ActiveSupport::Concern
+
+  included do
+    # A number of properties of this `Discussion`, like `first_note` and `resolvable?`, are memoized.
+    # When this discussion is resolved or unresolved, the values of these properties potentially change.
+    # To make sure all memoized values are reset when this happens, `update` resets all instance variables with names in
+    # `memoized_variables`. If you add a memoized method in `ResolvableDiscussion` or any `Discussion` subclass,
+    # please make sure the instance variable name is added to `memoized_values`, like below.
+    cattr_accessor :memoized_values, instance_accessor: false do
+      []
+    end
+
+    memoized_values.push(
+      :resolvable,
+      :resolved,
+      :first_note,
+      :first_note_to_resolve,
+      :last_resolved_note,
+      :last_note
+    )
+
+    delegate :potentially_resolvable?, to: :first_note
+
+    delegate  :resolved_at,
+              :resolved_by,
+
+              to: :last_resolved_note,
+              allow_nil: true
+  end
+
+  def resolvable?
+    return @resolvable if @resolvable.present?
+
+    @resolvable = potentially_resolvable? && notes.any?(&:resolvable?)
+  end
+
+  def resolved?
+    return @resolved if @resolved.present?
+
+    @resolved = resolvable? && notes.none?(&:to_be_resolved?)
+  end
+
+  def first_note
+    @first_note ||= notes.first
+  end
+
+  def first_note_to_resolve
+    return unless resolvable?
+
+    @first_note_to_resolve ||= notes.find(&:to_be_resolved?)
+  end
+
+  def last_resolved_note
+    return unless resolved?
+
+    @last_resolved_note ||= resolved_notes.sort_by(&:resolved_at).last
+  end
+
+  def resolved_notes
+    notes.select(&:resolved?)
+  end
+
+  def to_be_resolved?
+    resolvable? && !resolved?
+  end
+
+  def can_resolve?(current_user)
+    return false unless current_user
+    return false unless resolvable?
+
+    current_user == self.noteable.author ||
+      current_user.can?(:resolve_note, self.project)
+  end
+
+  def resolve!(current_user)
+    return unless resolvable?
+
+    update { |notes| notes.resolve!(current_user) }
+  end
+
+  def unresolve!
+    return unless resolvable?
+
+    update { |notes| notes.unresolve! }
+  end
+
+  private
+
+  def update
+    # Do not select `Note.resolvable`, so that system notes remain in the collection
+    notes_relation = Note.where(id: notes.map(&:id))
+
+    yield(notes_relation)
+
+    # Set the notes array to the updated notes
+    @notes = notes_relation.fresh.to_a
+
+    self.class.memoized_values.each do |var|
+      instance_variable_set(:"@#{var}", nil)
+    end
+  end
+end