module ActiveSupport #:nodoc:
  module CoreExtensions #:nodoc:
    module String #:nodoc:
      # Define methods for handling unicode data.
      module Unicode
        def self.append_features(base)
          if '1.8.7 and later'.respond_to?(:chars)
            base.class_eval { remove_method :chars }
          end
          super
        end

        unless '1.9'.respond_to?(:force_encoding)
          # +chars+ is a Unicode safe proxy for string methods. It creates and returns an instance of the
          # ActiveSupport::Multibyte::Chars class which encapsulates the original string. A Unicode safe version of all
          # the String methods are defined on this proxy class. Undefined methods are forwarded to String, so all of the
          # string overrides can also be called through the +chars+ proxy.
          #
          #   name = 'Claus Müller'
          #   name.reverse              # => "rell??M sualC"
          #   name.length               # => 13
          #
          #   name.chars.reverse.to_s   # => "rellüM sualC"
          #   name.chars.length         # => 12
          #   
          #
          # All the methods on the chars proxy which normally return a string will return a Chars object. This allows
          # method chaining on the result of any of these methods.
          #
          #   name.chars.reverse.length # => 12
          #
          # The Char object tries to be as interchangeable with String objects as possible: sorting and comparing between
          # String and Char work like expected. The bang! methods change the internal string representation in the Chars
          # object. Interoperability problems can be resolved easily with a +to_s+ call.
          #
          # For more information about the methods defined on the Chars proxy see ActiveSupport::Multibyte::Chars and
          # ActiveSupport::Multibyte::Handlers::UTF8Handler.
          def chars
            ActiveSupport::Multibyte::Chars.new(self)
          end

          # Returns true if the string has UTF-8 semantics (a String used for purely byte resources is unlikely to have
          # them), returns false otherwise.
          def is_utf8?
            ActiveSupport::Multibyte::Handlers::UTF8Handler.consumes?(self)
          end
        else
          def chars #:nodoc:
            self
          end

          def is_utf8? #:nodoc:
            case encoding
              when Encoding::UTF_8
                valid_encoding?
              when Encoding::ASCII_8BIT
                dup.force_encoding('UTF-8').valid_encoding?
              else
                false
            end
          end
        end
      end
    end
  end
end