Allow suggesting single line changes in diffs

2 files changed, 110 insertions, 0 deletions

diff --git a/app/services/suggestions/apply_service.rb b/app/services/suggestions/apply_service.rb
new file mode 100644
index 00000000000..d931d528c86
--- /dev/null
+++ b/app/services/suggestions/apply_service.rb
@@ -0,0 +1,54 @@
+# frozen_string_literal: true
+
+module Suggestions
+  class ApplyService < ::BaseService
+    def initialize(current_user)
+      @current_user = current_user
+    end
+
+    def execute(suggestion)
+      unless suggestion.appliable?
+        return error('Suggestion is not appliable')
+      end
+
+      params = file_update_params(suggestion)
+      result = ::Files::UpdateService.new(suggestion.project, @current_user, params).execute
+
+      if result[:status] == :success
+        suggestion.update(commit_id: result[:result], applied: true)
+      end
+
+      result
+    end
+
+    private
+
+    def file_update_params(suggestion)
+      diff_file = suggestion.diff_file
+
+      file_path = diff_file.file_path
+      branch_name = suggestion.noteable.source_branch
+      file_content = new_file_content(suggestion)
+      commit_message = "Apply suggestion to #{file_path}"
+
+      {
+        file_path: file_path,
+        branch_name: branch_name,
+        start_branch: branch_name,
+        commit_message: commit_message,
+        file_content: file_content
+      }
+    end
+
+    def new_file_content(suggestion)
+      range = suggestion.from_line_index..suggestion.to_line_index
+      blob = suggestion.diff_file.new_blob
+
+      blob.load_all_data!
+      content = blob.data.lines
+      content[range] = suggestion.to_content
+
+      content.join
+    end
+  end
+end
diff --git a/app/services/suggestions/create_service.rb b/app/services/suggestions/create_service.rb
new file mode 100644
index 00000000000..77e958cbe0c
--- /dev/null
+++ b/app/services/suggestions/create_service.rb
@@ -0,0 +1,56 @@
+# frozen_string_literal: true
+
+module Suggestions
+  class CreateService
+    def initialize(note)
+      @note = note
+    end
+
+    def execute
+      return unless @note.supports_suggestion?
+
+      suggestions = Banzai::SuggestionsParser.parse(@note.note)
+
+      # For single line suggestion we're only looking forward to
+      # change the line receiving the comment. Though, in
+      # https://gitlab.com/gitlab-org/gitlab-ce/issues/53310
+      # we'll introduce a ```suggestion:L<x>-<y>, so this will
+      # slightly change.
+      comment_line = @note.position.new_line
+
+      rows =
+        suggestions.map.with_index do |suggestion, index|
+          from_content = changing_lines(comment_line, comment_line)
+
+          # The parsed suggestion doesn't have information about the correct
+          # ending characters (we may have a line break, or not), so we take
+          # this information from the last line being changed (last
+          # characters).
+          endline_chars = line_break_chars(from_content.lines.last)
+          to_content = "#{suggestion}#{endline_chars}"
+
+          {
+            note_id: @note.id,
+            from_content: from_content,
+            to_content: to_content,
+            relative_order: index
+          }
+        end
+
+      rows.in_groups_of(100, false) do |rows|
+        Gitlab::Database.bulk_insert('suggestions', rows)
+      end
+    end
+
+    private
+
+    def changing_lines(from_line, to_line)
+      @note.diff_file.new_blob_lines_between(from_line, to_line).join
+    end
+
+    def line_break_chars(line)
+      match = /\r\n|\r|\n/.match(line)
+      match[0] if match
+    end
+  end
+end