1 files changed, 91 insertions, 0 deletions
diff --git a/app/models/discussion.rb b/app/models/discussion.rb
new file mode 100644
index 00000000000..74facfd1c9c
--- /dev/null
+++ b/app/models/discussion.rb
@@ -0,0 +1,91 @@
+class Discussion
+  NUMBER_OF_TRUNCATED_DIFF_LINES = 16
+
+  attr_reader :first_note, :notes
+
+  delegate  :created_at,
+            :project,
+            :author,
+
+            :noteable,
+            :for_commit?,
+            :for_merge_request?,
+
+            :line_code,
+            :diff_file,
+            :for_line?,
+            :active?,
+
+            to: :first_note
+
+  delegate :blob, :highlighted_diff_lines, to: :diff_file, allow_nil: true
+
+  def self.for_notes(notes)
+    notes.group_by(&:discussion_id).values.map { |notes| new(notes) }
+  end
+
+  def self.for_diff_notes(notes)
+    notes.group_by(&:line_code).values.map { |notes| new(notes) }
+  end
+
+  def initialize(notes)
+    @first_note = notes.first
+    @notes = notes
+  end
+
+  def id
+    first_note.discussion_id
+  end
+
+  def diff_discussion?
+    first_note.diff_note?
+  end
+
+  def legacy_diff_discussion?
+    notes.any?(&:legacy_diff_note?)
+  end
+
+  def for_target?(target)
+    self.noteable == target && !diff_discussion?
+  end
+
+  def expanded?
+    !diff_discussion? || active?
+  end
+
+  def reply_attributes
+    data = {
+      noteable_type: first_note.noteable_type,
+      noteable_id:   first_note.noteable_id,
+      commit_id:     first_note.commit_id,
+      discussion_id: self.id,
+    }
+
+    if diff_discussion?
+      data[:note_type] = first_note.type
+
+      data.merge!(first_note.diff_attributes)
+    end
+
+    data
+  end
+
+  # Returns an array of at most 16 highlighted lines above a diff note
+  def truncated_diff_lines
+    prev_lines = []
+
+    highlighted_diff_lines.each do |line|
+      if line.meta?
+        prev_lines.clear
+      else
+        prev_lines << line
+
+        break if for_line?(line)
+
+        prev_lines.shift if prev_lines.length >= NUMBER_OF_TRUNCATED_DIFF_LINES
+      end
+    end
+
+    prev_lines
+  end
+end