1 files changed, 107 insertions, 0 deletions
diff --git a/lib/gitlab/suggestions/file_suggestion.rb b/lib/gitlab/suggestions/file_suggestion.rb
new file mode 100644
index 00000000000..73b9800f0b8
--- /dev/null
+++ b/lib/gitlab/suggestions/file_suggestion.rb
@@ -0,0 +1,107 @@
+# frozen_string_literal: true
+
+module Gitlab
+  module Suggestions
+    class FileSuggestion
+      include Gitlab::Utils::StrongMemoize
+
+      SuggestionForDifferentFileError = Class.new(StandardError)
+
+      def initialize
+        @suggestions = []
+      end
+
+      def add_suggestion(new_suggestion)
+        if for_different_file?(new_suggestion)
+          raise SuggestionForDifferentFileError,
+                'Only add suggestions for the same file.'
+        end
+
+        suggestions << new_suggestion
+      end
+
+      def line_conflict?
+        strong_memoize(:line_conflict) do
+          _line_conflict?
+        end
+      end
+
+      def new_content
+        @new_content ||= _new_content
+      end
+
+      def file_path
+        @file_path ||= _file_path
+      end
+
+      private
+
+      attr_accessor :suggestions
+
+      def blob
+        first_suggestion&.diff_file&.new_blob
+      end
+
+      def blob_data_lines
+        blob.load_all_data!
+        blob.data.lines
+      end
+
+      def current_content
+        @current_content ||= blob.nil? ? [''] : blob_data_lines
+      end
+
+      def _new_content
+        current_content.tap do |content|
+          suggestions.each do |suggestion|
+            range = line_range(suggestion)
+            content[range] = suggestion.to_content
+          end
+        end.join
+      end
+
+      def line_range(suggestion)
+        suggestion.from_line_index..suggestion.to_line_index
+      end
+
+      def for_different_file?(suggestion)
+        file_path && file_path != suggestion_file_path(suggestion)
+      end
+
+      def suggestion_file_path(suggestion)
+        suggestion&.diff_file&.file_path
+      end
+
+      def first_suggestion
+        suggestions.first
+      end
+
+      def _file_path
+        suggestion_file_path(first_suggestion)
+      end
+
+      def _line_conflict?
+        has_conflict = false
+
+        suggestions.each_with_object([]) do |suggestion, ranges|
+          range_in_test = line_range(suggestion)
+
+          if has_range_conflict?(range_in_test, ranges)
+            has_conflict = true
+            break
+          end
+
+          ranges << range_in_test
+        end
+
+        has_conflict
+      end
+
+      def has_range_conflict?(range_in_test, ranges)
+        ranges.any? do |range|
+          range.overlaps?(range_in_test)
+        end
+      end
+    end
+  end
+end