--- /dev/null
+# RFC 4646/47 compliant Locale tag implementation that parses locale tags to
+# subtags such as language, script, region, variant etc.
+#
+# For more information see by http://en.wikipedia.org/wiki/IETF_language_tag
+#
+# Rfc4646::Parser does not implement grandfathered tags.
+
+module I18n
+ module Locale
+ module Tag
+ RFC4646_SUBTAGS = [ :language, :script, :region, :variant, :extension, :privateuse, :grandfathered ]
+ RFC4646_FORMATS = { :language => :downcase, :script => :capitalize, :region => :upcase, :variant => :downcase }
+
+ class Rfc4646 < Struct.new(*RFC4646_SUBTAGS)
+ class << self
+ # Parses the given tag and returns a Tag instance if it is valid.
+ # Returns false if the given tag is not valid according to RFC 4646.
+ def tag(tag)
+ matches = parser.match(tag)
+ new(*matches) if matches
+ end
+
+ def parser
+ @@parser ||= Rfc4646::Parser
+ end
+
+ def parser=(parser)
+ @@parser = parser
+ end
+ end
+
+ include Parents
+
+ RFC4646_FORMATS.each do |name, format|
+ define_method(name) { self[name].send(format) unless self[name].nil? }
+ end
+
+ def to_sym
+ to_s.to_sym
+ end
+
+ def to_s
+ @tag ||= to_a.compact.join("-")
+ end
+
+ def to_a
+ members.collect { |attr| self.send(attr) }
+ end
+
+ module Parser
+ PATTERN = %r{\A(?:
+ ([a-z]{2,3}(?:(?:-[a-z]{3}){0,3})?|[a-z]{4}|[a-z]{5,8}) # language
+ (?:-([a-z]{4}))? # script
+ (?:-([a-z]{2}|\d{3}))? # region
+ (?:-([0-9a-z]{5,8}|\d[0-9a-z]{3}))* # variant
+ (?:-([0-9a-wyz](?:-[0-9a-z]{2,8})+))* # extension
+ (?:-(x(?:-[0-9a-z]{1,8})+))?| # privateuse subtag
+ (x(?:-[0-9a-z]{1,8})+)| # privateuse tag
+ /* ([a-z]{1,3}(?:-[0-9a-z]{2,8}){1,2}) */ # grandfathered
+ )\z}xi
+
+ class << self
+ def match(tag)
+ c = PATTERN.match(tag.to_s).captures
+ c[0..4] << (c[5].nil? ? c[6] : c[5]) << c[7] # TODO c[7] is grandfathered, throw a NotImplemented exception here?
+ rescue
+ false
+ end
+ end
+ end
+ end
+ end
+ end
+end