1 files changed, 54 insertions, 0 deletions
diff --git a/lib/gitlab/suggestions/commit_message.rb b/lib/gitlab/suggestions/commit_message.rb
new file mode 100644
index 00000000000..d59a8fc3730
--- /dev/null
+++ b/lib/gitlab/suggestions/commit_message.rb
@@ -0,0 +1,54 @@
+# frozen_string_literal: true
+
+module Gitlab
+  module Suggestions
+    class CommitMessage
+      DEFAULT_SUGGESTION_COMMIT_MESSAGE =
+        'Apply %{suggestions_count} suggestion(s) to %{files_count} file(s)'
+
+      def initialize(user, suggestion_set)
+        @user = user
+        @suggestion_set = suggestion_set
+      end
+
+      def message
+        project = suggestion_set.project
+        user_defined_message = project.suggestion_commit_message.presence
+        message = user_defined_message || DEFAULT_SUGGESTION_COMMIT_MESSAGE
+
+        Gitlab::StringPlaceholderReplacer
+          .replace_string_placeholders(message, PLACEHOLDERS_REGEX) do |key|
+          PLACEHOLDERS[key].call(user, suggestion_set)
+        end
+      end
+
+      def self.format_paths(paths)
+        paths.sort.join(', ')
+      end
+
+      private_class_method :format_paths
+
+      private
+
+      attr_reader :user, :suggestion_set
+
+      PLACEHOLDERS = {
+        'branch_name' => ->(user, suggestion_set) { suggestion_set.branch },
+        'files_count' => ->(user, suggestion_set) { suggestion_set.file_paths.length },
+        'file_paths' => ->(user, suggestion_set) { format_paths(suggestion_set.file_paths) },
+        'project_name' => ->(user, suggestion_set) { suggestion_set.project.name },
+        'project_path' => ->(user, suggestion_set) { suggestion_set.project.path },
+        'user_full_name' => ->(user, suggestion_set) { user.name },
+        'username' => ->(user, suggestion_set) { user.username },
+        'suggestions_count' => ->(user, suggestion_set) { suggestion_set.suggestions.size }
+      }.freeze
+
+      # This regex is built dynamically using the keys from the PLACEHOLDER struct.
+      # So, we can easily add new placeholder just by modifying the PLACEHOLDER hash.
+      # This regex will build the new PLACEHOLDER_REGEX with the new information
+      PLACEHOLDERS_REGEX = Regexp.union(PLACEHOLDERS.keys.map do |key|
+        Regexp.new(Regexp.escape(key))
+      end).freeze
+    end
+  end
+end