Prepare suggestion implementation for multi-line

Adds the groundwork needed in order to persist multi-line suggestions,
while providing the parsing strategy which will be reused for the
**Preview** as well.

1 files changed, 30 insertions, 0 deletions

diff --git a/app/services/concerns/suggestible.rb b/app/services/concerns/suggestible.rb
new file mode 100644
index 00000000000..0b9822b1909
--- /dev/null
+++ b/app/services/concerns/suggestible.rb
@@ -0,0 +1,30 @@
+# frozen_string_literal: true
+
+module Suggestible
+  extend ActiveSupport::Concern
+
+  # This translates into limiting suggestion changes to `suggestion:-100+100`.
+  MAX_LINES_CONTEXT = 100.freeze
+
+  def fetch_from_content
+    diff_file.new_blob_lines_between(from_line, to_line).join
+  end
+
+  def from_line
+    real_above = [lines_above, MAX_LINES_CONTEXT].min
+    [target_line - real_above, 1].max
+  end
+
+  def to_line
+    real_below = [lines_below, MAX_LINES_CONTEXT].min
+    target_line + real_below
+  end
+
+  def diff_file
+    raise NotImplementedError
+  end
+
+  def target_line
+    raise NotImplementedError
+  end
+end