auto replace rules in titles

lib/text_cleaner.rb

@@ -0,0 +1,45 @@
+#
+# Clean up a text
+#
+class TextCleaner
+
+  def self.title_options
+    # cf. http://meta.discourse.org/t/should-we-have-auto-replace-rules-in-titles/5687
+    {
+      deduplicate_exclamation_marks: SiteSetting.title_prettify,
+      deduplicate_question_marks: SiteSetting.title_prettify,
+      replace_all_upper_case: SiteSetting.title_prettify,
+      capitalize_first_letter: SiteSetting.title_prettify,
+      remove_unnecessary_period: SiteSetting.title_prettify,
+      remove_extraneous_space: SiteSetting.title_prettify && SiteSetting.default_locale == "en",
+      fixes_interior_spaces: true,
+      strip_whitespaces: true
+    }
+  end
+
+  def self.clean_title(title)
+    TextCleaner.clean(title, TextCleaner.title_options)
+  end
+
+  def self.clean(text, opts = {})
+    # Replace !!!!! with a single !
+    text.gsub!(/!+/, '!') if opts[:deduplicate_exclamation_marks]
+    # Replace ????? with a single ?
+    text.gsub!(/\?+/, '?') if opts[:deduplicate_question_marks]
+    # Replace all-caps text with regular case letters
+    text.tr!('A-Z', 'a-z') if opts[:replace_all_upper_case] && (text =~ /[A-Z]+/) && (text == text.upcase)
+    # Capitalize first letter
+    text.sub!(/\A([a-z])/) { |first| first.capitalize } if opts[:capitalize_first_letter]
+    # Remove unnecessary period at the end
+    text.sub!(/([^.])\.(\s*)\z/, '\1\2') if opts[:remove_unnecessary_period]
+    # Remove extraneous space before the end punctuation
+    text.sub!(/\s+([!?]\s*)\z/, '\1') if opts[:remove_extraneous_space]
+    # Fixes interior spaces
+    text.gsub!(/ +/, ' ') if opts[:fixes_interior_spaces]
+    # Strip whitespaces
+    text.strip! if opts[:strip_whitespaces]
+
+    text
+  end
+
+end