# encoding: utf-8

module ActiveSupport #:nodoc:
  module CoreExtensions #:nodoc:
    module String #:nodoc:
      # Implements multibyte methods for easier access to multibyte characters in a String instance.
      module Multibyte
        unless '1.9'.respond_to?(:force_encoding)
          # +mb_chars+ is a multibyte safe proxy method for string methods.
          #
          # In Ruby 1.8 and older 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. If the proxy class doesn't respond to a certain method, it's forwarded to the encapsuled string.
          #
          #   name = 'Claus Müller'
          #   name.reverse  #=> "rell??M sualC"
          #   name.length   #=> 13
          #
          #   name.mb_chars.reverse.to_s   #=> "rellüM sualC"
          #   name.mb_chars.length         #=> 12
          #
          # In Ruby 1.9 and newer +mb_chars+ returns +self+ because String is (mostly) encoding aware so we don't need
          # a proxy class any more. This means that +mb_chars+ makes it easier to write code that runs on multiple Ruby
          # versions.
          #
          # == Method chaining 
          #
          # 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.mb_chars.reverse.length #=> 12
          #
          # == Interoperability and configuration
          #
          # 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. For
          # information about how to change the default Multibyte behaviour, see ActiveSupport::Multibyte.
          def mb_chars
            if ActiveSupport::Multibyte.proxy_class.wants?(self)
              ActiveSupport::Multibyte.proxy_class.new(self)
            else
              self
            end
          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::Chars.consumes?(self)
          end

          unless '1.8.7 and later'.respond_to?(:chars)
            alias chars mb_chars
          end
        else
          # In Ruby 1.9 and newer +mb_chars+ returns self. In Ruby 1.8 and older +mb_chars+ creates and returns an
          # Unicode safe proxy for string operations, this makes it easier to write code that runs on multiple Ruby
          # versions.
          def mb_chars
            self
          end
          
          # Returns true if the string has valid UTF-8 encoding.
          def is_utf8?
            case encoding
            when Encoding::UTF_8
              valid_encoding?
            when Encoding::ASCII_8BIT, Encoding::US_ASCII
              dup.force_encoding(Encoding::UTF_8).valid_encoding?
            else
              false
            end
          end
        end
      end
    end
  end
end